Dissertations / Theses on the topic 'Neurobiology'

Reelin is a large extracellular matrix glycoprotein with a crucial role both during brain development, where it is key for neuronal migration and for the formation of the layered structure of cerebral cortex and cerebellum, and in the adulthood, where it is involved in adult synaptic plasticity, including neurogenesis in the dentate gyrus and dendritogenesis amongst other processes. Reelin acts through the binding to its canonical receptors (apolipoprotein E receptor 2, ApoER2; and very low density lipoprotein receptor, VLDLR) which trigger a complex signaling cascade involving numerous kinases and the adaptor protein Dab1. At the embryonic stage, Reelin is expressed mainly by Cajal-Retzius cells on the developing brain whereas at perinatal stages its expression gradually disappears from Cajal-Retzius cells and starts to be expressed by GABAergic interneurons of the cortex and hippocampus. In the neocortex, postmitotic neurons migrate in an ordered sequence that determines the normal “inside-out” layer formation. The malpositioning of cortical neurons is a result of abnormal migration and could cause severe layering malformations with functional consequences related with neurodevelopmental diseases such as Schizophrenia, Autism and Epilepsy. In this context, one of the most studied models has been the reeler mouse which presents a characteristic phenotype caused by an autosomal mutation in the Rln gene. The reeler mouse presents several morphological defects including a failed pre-plate splitting that causes a roughly inverted neuronal layering in the cortex, mispositioning of pyramidal neurons as well as granular cells on the dentate gyrus and profound cerebellar hypoplasia. However the study of the effects of Reelin signaling in the adult brain is difficult in the reeler mouse model due to the failed migration and mispositioning during development. Thus, to unravel the function of Reelin at different developmental stages (from embryonic to adult) as well as to gain insight in the potential distinct contribution of Reelin from different cell-types, we have generated three Reelin deficient conditional transgenic lines which allow us to ubiquitously delete Reelin in a temporally-controlled manner (Cre fR/fR) or selectively remove Reelin from Cajal-Retzius cells (CR fR/fR) or GABAergic interneurons (Gad fR/fR). Analysis of the cortical organization using layer-specific markers reveals that, unlike the reeler mouse, none of our transgenic lines shows the characteristic inversion of cortical layers. Moreover, our data strongly indicates that Reelin from Cajal-Retzius cells is important for the typical inside-out laminar cortical development but seems to be dispensable for pre-plate splitting. Furthermore, our results suggest that the absence of Reelin during early postnatal and adult stages seems to impact on the well-defined laminar structure of the cortex, leading to an invasion of layer I by late-born neurons from layer II-III. Regarding the hippocampus, our results suggest, on the one hand, a differential contribution of Reelin expressed by Cajal-Retzius cells and by GABAergic interneurons in the formation of the laminar structures of the hippocampus. On the other hand, temporally-controlled removal of Reelin at postnatal stages demonstrates that it is essential for the correct formation of the hippocampus whereas in the adult seems to be key for several aspects of hippocampus neurogenesis, including neuronal positioning in the dentate gyrus and dendritic orientation at different maturation stages of adult new-born granule cells. Finally, our findings also support the importance of Reelin expression for proper Purkinje cell migration, but not for granule cell disposition in the cerebellum at early postnatal and adult stages. Taken altogether, our results suggest a causal relation between the absence of Reelin and structural alterations in the hippocampus, cortex and cerebellum, either at developments stages or adult stages.
Reelina es una glicoproteína extracelular de matriz esencial para la regulación de los procesos de migración neuronal y posicionamiento de las neuronas corticales durante el desarrollo del encéfalo. Durante la embriogénesis, Reelina es producida por las células Cajal-Retzius de la superficie de la corteza en desarrollo. En este estadío, las neuronas postmitóticas migran de forma ordenada originando una estructura laminar en seis capas, en las cuáles las neuronas más jóvenes se sitúan en las capas más externas. La pérdida de Reelina durante el desarrollo comporta fallos en la migración de las neuronas, provocando a su vez grandes alteraciones en la estructuración de la corteza que contribuyen a la patogénesis de muchos trastornos neurológicos como el autismo, la epilepsia, la esquizofrenia, o el trastorno bipolar. En este contexto, uno de los fenotipos más estudiado es el del ratón mutante de Reelina, reeler, que presenta una estructura cortical alterada con las capas invertidas. Sin embargo, dado que la expresión de Reelina durante el desarrollo ocurre a edades embrionarias muy tempranas, es difícil estudiar el efecto de su pérdida en este tipo de mutantes a edades más tardías, en los que los primeros efectos de su pérdida son tan profundos. Todo ello evidencia la necesidad de desarrollar otro tipo de modelos en los que la pérdida de Reelina sea más gradual o selectiva. En estadíos perinatales y en el cerebro adulto Reelina es expresada principalmente por interneuronas gabaérgicas, donde presumiblemente Reelina controla funciones de formación de sinapsis y mantenimiento de la plasticidad sináptica de las neuronas del córtex y del hipocampo. Nuestros resultados muestran un fenotipo diferencial para cada uno de nuestros mutantes, sugiriendo un papel diferente de Reelina expresada por cada tipo celular, o en función del estadío en el cuál la deleccionamos. En concreto, hemos visto que la función de Reelina es imprescindible para la correcta laminación del córtex, para la formación del hipocampo, y para el correcto posicionamiento de las células Purkinje del cerebelo. Además la pérdida de Reelina en estadíos adultos comporta fallos en la neurogénesis de la zona subventricular del giro dentado.

Since the use of opioids started to emerge for analgesic reasons in the 19th century with the synthetization of morphine, opioids have been studied rigorously to better understand its effects on the brain. This thesis shows that both the analgesic effects and the reinforcing effects of opioids are mediated by the same receptor, the mu opioid receptor (MOR). MOR activity has been correlated to both primary and secondary reinforcers and should be considered to cause positive reinforcement together with increases in dopamine transmission for all drugs of abuse, and not only in relation to opioids. Opioid tolerance, dependence and even addiction are to some extent thought to relate to opioids’ acute effect of cyclic adenosine monophosphate (cAMP) superactivation. Based upon these findings, the allostasis theory of addiction is considered to be the most suitable in defining opioid addiction. The theory claims that the mesolimbic dopamine system becomes sensitized, increasing the attractiveness of opioids. This while counteradaptation increases the pleasurable tolerance of opioids, encouraging the user to increase its intake for the same initial reward. Furthermore the theory claims that cAMP superactivation is causing an unfolding effect of neurobiological and neurochemical expressions which leads to the disorder of addiction. cAMP superactivation is mediating the negatively reinforcing aspects of opioid addiction together with changes to corticotropin-releasing factor (CRF) in the brain stress system, such as the hypothalamic-pituitary-adrenal (HPA) axis and the extended amygdala.

Pas de résumé
Oligodendrocyte precursors cells (OPCs) are a major pool of progenitors during early development, but also persist in the adult. In 2000, a major dogma in neuroscience was broken when the existence of bona fide synapses between neurons and OPCs, a non-neuronal cell in the brain, was demonstrated. Now, it is known that OPCs can be contacted either by glutamatergic or GABAergic synapses in grey and white matter regions. However, the role of these synapses, especially of GABAergic synapses, in OPC physiology is still unclear. Our team previously demonstrated that synaptic inputs received by OPCs in the deep layer of the somatosensory cortex are primarly GABAergic. It shows that these synapses are transient, reaching a peak of connectivity in the second postnatal week (2PNW) and disappearing in the fourth postnatal week (4PNW). Nevertheless, a different mode of GABAergic transmission still persists in the 4PNW in a form of an extrasynaptic transmission relying solely on GABA spillover from nearby neurons. In the first study of this thesis, I demonstrated that the developmental switch of transmission from synaptic to extrasynaptic between GABAergic interneurons and OPCs is accompanied by molecular changes in the subunit composition of the GABAA receptors (GABAARs) of OPCs. These changes are mainly characterized by the downregulation of the γ2 and the α5 subunits between the 2PNW and the 4PNW. Interestingly, the γ2 subunit, known as a hallmark of synaptic GABAARs in neurons, is downregulated in concomitance with the loss of synaptic inputs of cortical OPCs. Pharmacology specific for γ2 showed that the switch of transmission starts at the end of the 2PNW, with a gradual loss of sensitivity to diazepam, and a decrease in the amplitude of the miniature GABAergic evoked events. The leading hypotheses regarding the role of OPC synapses include proliferation and differentiation of OPCs as well as myelination. However, none has been formally demonstrated. Since γ2 is expressed exclusively at synaptic sites in OPCs, I targeted this subunit to inactivate γ2-mediated synapses and unravel their fonction in OPCs during postnatal development. The inducible deletion of γ2 in OPCs decreased by more than a half their GABAergic synaptic activity during the 2PNW, indicating that this model constitutes a suitable tool to inactivate cortical GABAergic OPC synapses. Contrary to initial hypotheses, including those of my team, we did not observe any change in proliferation, differentiation or developmental myelination pattern of the somatosensory cortex in the knockout mouse. In addition, two-photon calcium imaging allowed us to demonstrate that evoked γ2- mediated synaptic signaling does not involved calcium signaling. Nevertheless, we observed a decrease in the number of OPCs at P30 in the knockout mouse, suggesting that these synapses regulate the self-maintenance capacity of OPCs rather than oligodendrogenesis or myelination. To confirm that the reduction of OPC density is caused specifically by the inactivation of γ2-mediated synapses, we examined the proportion of recombinant OPCs and OLs, and used non-recombinant cells as internal controls. We observed a significant 32% decrease of recombined OPCs in the knockout at P30 that was not compensated by recombinant OLs or non-recombinant cells. Hence, postsynaptic γ2-mediated GABAARs play a role in adjusting OPC density during postnatal development. In conclusion, during my thesis I have demonstrated that the postnatal switch of transmission from synaptic in the 2PNW to extrasynaptic at the 4PNW between interneurons and OPCs is accompanied by the down-regulation of the γ2 subunit of GABAARs in cortical OPCs. Impairing the γ2-mediated synaptic GABAergic signaling in OPCs did not result in drastic changes in the proliferation of differentiation of these cells. Instead, our results rather indicate a role in the density homeostasis of OPC population during cortical development

Intertemporal choices are both common and important and yet the neurobiology of intertemporal choice is poorly understood. The work in this thesis contributes to a growing literature on the neurobiology of intertemporal choice. In particular I have investigated the contributions of the orbitofrontal cortex (OFC) and hippocampus (HPC) to intertemporal choice through the creation of novel intertemporal choice behavioral tasks. Firstly I reported that lesions of the HPC, but not the OFC, cauSe impulsive choice in a non-spatial T-maze based behavioral task. Secondly I described the creation and validation of a spatial, T-maze based intertemporal choice task for mice. This task was then used to investigate the contributions of the dopaminergic and serotonergic systems to intertemporal choice in mice. These experiments suggested that the dopaminergic system, but not the serotonergic system, is important in intertemporal choice. I then examined the contributions of the mouse OFC and HPC to intertemporal choice using an operant intertemporal choice task for mic.e. In this task, lesions of the HPC, but not the OFC, cause an increase in self- . controlled choice. Finally I reported a series of modelling experiments exploring the adaptiveness of self-control in foraging. These experiments called into question an influential theory suggesting that interspecific differences i~ metabolic rates helped .drive the evolution of impulsive strategies.. ' The behavioral tasks developed in this thesis may be used to further our understanding of the neurobiology of intertemporal choice and in particular the genetic basis of intertemporal choice.

`Object constancy' is the name given to the brain's ability to overcome the myriad environmental obstacles to visual perception and produce a stable, consistent internal representation of object shape. Changes in object orientation represent one such confound. It can be inferred from the time taken to recognise misoriented objects that we encode specific object views based on our experience of those objects and their typical orientations ('viewpoint-dependent recognition'). Such studies also suggest that we may recognise certain objects in a manner that is not dependent on their orientation ('viewpoint-invariant recognition'). Further studies indicate that the time to resolve two angularly disparate shapes (`mental rotation') increases as a function of their angular disparity. It is hypothesised, based on these findings, that viewpoint-dependent recognition and mental rotation share a common mechanism for transforming the global stimulus percept into alignment, but that viewpointinvariant recognition is achieved by some other, non-transformational means. This thesis presents studies that examine the cortical correlates of viewpoint-dependent and viewpointinvariant object recognition using novel objects to eliminate the confounding effects of prior experience. It also presents a study that directly compares the cortical correlates of mental rotation, viewpoint-dependent and viewpoint-invariant recognition. Further comparison of these object constancy processes is then made using electrophysiological markers of visuospatial transformation. The findings of these studies indicate that viewpoint-dependent recognition and mental rotation recruit a bilateral parietal-premotor network for the manipulation of global stimulus percepts, hypothesised to be the same mechanism as that used for physical object manipulation and prehension. Viewpoint-invariant recognition does not appear to recruit such a mechanism, and this process appears to be less expensive in terms of cognitive resources than transformational object constancy mechanisms. Thus, implementation of a viewpoint-invariant mechanism to recognise misoriented objects is preferable, but may not be possible where stimulus features are few or ambiguous. In recognising misoriented objects, viewpoint-dependent and viewpoint-invariant mechanisms initially proceed in parallel, but successful recognition of object invariant features may be sufficient to terminate the viewpoint-dependent mechanism.

In the course of our everyday lives, we are constantly faced with situations in which we must choose. Do we invest in the bank or the stock-market? Is a new wage deal so unfair that we should resort to a strike? These situations are elegantly described mathematically by Rational Choice Theory (RCT), which dominates the quantitative social sciences such as economics. However, unfortunately RCT often fails to predict how humans actually behave. Here I investigate choice using paradigms derived from the RCT framework, but aim to better predict actual choices by using a biological level of explanation. First, I examine simple choices that involve no social interaction, asking how choices are influenced by risk in potential outcomes, and by whether outcomes reflect potential gains or losses. The data reveal independent impacts of risk and loss on choice, findings not predicted by extant economic theories. Instead, I then harness functional Magnetic Resonance Imaging (fMRI) to suggest a biological mechanism by which risk and loss bias approach behaviour, and test this hypotheses in further behavioural experiments. Secondly, I examine social choices. Specifically, I examine biological systems that enable social behaviour to respond flexibly to environmental contingencies. I investigate the neural basis of the human fairness motivation using fMRI, and show how it flexibly adapts to external social context. Next, I show how this fairness motivation adapts to changes in an individual’s internal physiological state. Finally, I show how cooperation is modulated by the androgen hormone testosterone. Overall, in light of these non-social and social findings, I propose that a biologically-based account of choice can explain choices that are not predicted by existing theory.

Ketamine is a dissociative anesthetic prescription drug and has been used for general anesthesia. The research surrounding this chemical compound has revealed conflicting evidence of its potential use in health care and addiction treatment. On one side, ketamine is a widespread drug of abuse associated with neurocognitive deficits and neurotoxicity, on the other side ketamine has recently been found to have a variety of potential uses, including but not limited to; antidepressant effects, reconsolidation of drug-related memories and disrupting maladaptive rumination. Ketamine’s ability to induce psychedelic and mystic experiences, reconsolidation of memories, antidepressant effects, and its ability to reduce cue-induced drug craving makes it a potentially useful tool in drug abuse therapy. Most of the negative side-effects of ketamine seem to be apparent at high doses and in frequent use but low doses and non-frequent use has a low risk of harm, therefore, careful consideration and extensive research are required before ketamine can be widely used in the public and in health care for treatment strategies. This thesis aims to explore the role of ketamine and its neurobiological effects in the treatment of addiction and depression.

Many animals exhibit seasonal changes in life-history stages, and these seasonal transitions are often accompanied by dramatic switches in behavior. While the neuroendocrine mechanisms that regulate such behavioral transitions are poorly understood, arginine vasotocin (AVT) and neuropeptide Y (NPY) are excellent candidates because they regulate reproductive and feeding behavior, respectively. In this study, I asked if seasonal changes in AVT and/or NPY are concomitant with spring migration away from the breeding grounds, as male and female red-sided garter snakes (Thamnophis sirtalis parietalis) are transitioning from reproductive to non-reproductive behavior during this time. To address this question, I collected male and female snakes in different migratory stages during the spring and fall. Brains were processed for AVT and NPY immunohistochemistry and the total number of immunoreactive (-ir) cells quantified for each individual. As predicted, males had significantly more AVT-ir cells in the preoptic area and bed nucleus of the stria terminalis, brain regions important for courtship behavior, during the spring mating season compared to the fall. Females had significantly more AVT-ir cells in the preoptic area during the spring compared to the fall and, surprisingly, did not exhibit seasonal changes in NPY. In contrast, males had significantly more NPY-ir cells in the cortex, a region important for spatial memory, and in the posterior hypothalamus during the fall compared to the spring, which likely reflects increased feeding behavior during the summer foraging period. Neither AVT- nor NPY-ir cell number varied significantly with migratory status, indicating that seasonal changes in these neuropeptides are not directly related to migration. I then asked if the observed seasonal changes in AVT and NPY in males and females are related to the transition from reproductive to non-reproductive states. Compared to courting males, non-courting males had significantly more AVT-ir cells in the supraoptic nucleus and more NPY-ir cells in the cortex. AVT- and NPY-ir cells did not differ between unmated and mated females. Collectively, my results suggest that AVT and NPY play a role in regulating seasonal transitions in male reproductive behavior, rather than regulating migration per se. Further, these data indicate that both AVT and NPY are regulating reproductive behavior differently in males versus females. These data provide the framework for future studies examining the mechanisms regulating transitions between reproductive, migratory and foraging behaviors.

Risk is a highly salient psychological decision variable, and sensitivity to risk is an evolutionarily ancient attribute. In this thesis I address the neurobiological foundation of risk assessment, and show that behaviour is driven by an underlying distributed neural representation of different elements of risk in the brain. In particular, I show using fMRI (in Chapter 4) and MEG (in Chapter 8) that variance (dispersion) and skewness (asymmetry) of gambles evokes anatomically separable neural responses in a parietal, prefrontal and insula cortical network. I discuss possible theoretical neurobiological mechanisms by which preferences could be imbued to choice, and show that subjective tastes for risk, in terms of behavioural sensitivity to each of these risk dimensions, influences the encoding of risk and subsequent anticipatory responses. In Chapter 5, I show that a representation of prospective outcomes several trials into the future is supported by a dissociated encoding of the statistical information of future states in medial prefrontal cortex; furthermore that this encoding is contingent upon overarching goals or constraints. In Chapter 6, I demonstrate that economic choice is highly susceptible to exogenous biological influences, namely the effect of metabolic state, whilst in Chapter 7 I provide evidence that the encoding of risk is not affected by dopaminergic disruption, suggesting that dopamine might mediate effects on risk-taking via its role in reward feedback representation. In summary, the studies in this thesis elaborate the neural mechanisms underlying how humans make both single-shot and sequential decisions under risk, central elements in decision-making scenarios ranging from foraging to financial investment. This demonstrates that phylogenetically ancient circuitry subserving valuation and reward decompose choice into their salient statistical features, enabling the sophisticated representation of the future and its alternatives.

Adolescence represents a time in development when the reward system undergoes substantial changes. Several studies suggest differences in reward processing amongst adolescents compared to adults and children. Abnormalities in reward processing also underlie many psychiatric disorders, such as attention deficit hyperactivity disorder (ADHD). The present research has the following objectives: 1) to investigate normal reward processing during reward anticipation and reward feedback in a large population based cohort of old adolescents. 2) to explore gender differences in reward processing and determine whether the association between reward processing and ADHD symptoms differs between boys and girls. 3) to determine whether the X-linked gene Monoamine Oxidase A (MAOA) is associated with ventral striatal brain activation during reward anticipation and 4) to investigate whether MAOA stratifies the relationship between ventral striatal activation and ADHD symptoms in boys. Objectives 1 and 2 were explored using the full IMAGEN dataset (n > 1200 adolescent), objective 3 was addressed using the first wave of IMAGEN, including both boys and girls (n = 411 adolescents) whereas objective 4 was investigated using only boys from the first wave (n = 190 adolescents). The results from random effects analyses and region of interest analyses suggested robust activation patterns during reward anticipation and feedback, particularly in the ventral striatum (VS) and orbitofrontal cortex. Gender differences were prominent during both phases of reward processing with boys showing significantly higher activation of a number of regions, including the VS, relative to girls. We also found that the X-linked gene MAOA significantly affected VS activation in boys, but not in girls. This gene also stratified the frequently reported relationship between VS activation and ADHD symptoms in adolescent boys.

Thesis (Ph. D.)--University of California, San Diego and San Diego State University, 2010.
Title from first page of PDF file (viewed February 17, 2010). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 81-86).

L’addiction se caractérise par une recherche et une consommation pathologiques de la drogue, maintenues malgré leurs conséquences néfastes. C’est une pathologie chronique car, le plus souvent, les tentatives de sevrage se soldent par une rechute. L’addiction à la cocaïne se développe chez 15 à 20 % des usagers, après un usage plus ou moins prolongé. Les solutions thérapeutiques font gravement défaut et c’est un enjeu que de comprendre les mécanismes neurobiologiques qui sous-tendent cette addiction. Les études cliniques et précliniques proposent que l’addiction résulte d’un déséquilibre entre les circuits cortico-subcorticaux qui gèrent la valeur motivationnelle de la drogue et ceux qui sont impliqués dans le contrôle cognitif inhibiteur. Des changements séquentiels dans des circuits interconnectés qui incluent notamment le noyau basolatéral de l’amygdale, le noyau accumbens et le cortex préfrontal seraient au cœur de processus motivationnels pathologiques et d’une difficulté à inhiber le craving et la consommation. L’étude de l’addiction, à l’échelle des circuits neuronaux, fait face à plusieurs défis. Techniquement limitée chez l’homme, elle peut bénéficier des modèles animaux, mais seulement s’ils capturent des dimensions de la pathologie. Au cours des dix dernières années, de tels modèles ont été mis en œuvre, mais exclusivement chez le rat. Or, les outils pour l’exploration fonctionnelle fine des circuits neuronaux ont été majoritairement développés chez la souris. Un autre défi consiste à pouvoir questionner la fonctionnalité des circuits, en temps réel, sur l’individu se comportant. Mes travaux de thèse ont eu pour objectif : 1. L’étude de marqueurs de connectivité fonctionnelle chez des rats Addict et des rats Non-addict à la cocaïne. Notre modèle d’addiction à la cocaïne permet d’identifier 15 à 20 % de rats qui, après une période prolongée d’autoadministration intraveineuse de cocaïne, et bien qu’ils aient consommé la même quantité de cocaïne que les autres, montrent une très forte motivation pour la substance, une difficulté à limiter la recherche de drogue, et maintiennent la prise de cocaïne malgré ses conséquences néfastes. L’électrophysiologie in vivo, multi-site, au moyen d’enregistrements unitaires ou de potentiels de champs locaux est un outil de choix pour l’exploration de la connectivité fonctionnelle chez le rongeur. Un défi technique a été de l’adapter pour la coupler à notre modèle d’addiction à la cocaïne chez le rat. Nous avons montré des différences significatives de connectivité fonctionnelle entre rats Addict et Non-addict, suggérant un défaut de fonctionnalité du cortex préfrontal médian (PFM) chez les Addict. 2. L’étude du rôle du cortex prélimbique (PL) dans le contrôle du comportement d’autoadministration de cocaïne chez le rat. Des données récentes de la littérature remettent en cause le dogme selon lequel le PL exerce exclusivement un rôle facilitateur sur les propriétés motivationnelles de la cocaïne. Nous avons cherché à clarifier le rôle du PL dans le comportement d’autoadministration de cocaïne avant que ne se développe une addiction : comprendre son rôle dans l’usage précoce de cocaïne pour, à terme, étudier l’évolution de son implication selon que l’individu développe ou non une addiction. Nous avons montré que l’inactivation du PL peut s’accompagner, chez le même individu, d’une diminution ou d’une exacerbation du comportement de recherche de cocaïne selon les contingences expérimentales. Les neurones du PL émettent des projections vers plusieurs structures. Pour étudier leur rôle dans les effets comportementaux observés, nous avons travaillé à la mise au point d’outils optogénétiques pour la manipulation de l’activité de voies neuronales spécifiques, chez le rat, pour lequel ils sont encore très peu développés. Mes travaux de thèse contribuent tant sur le plan théorique que technique à la compréhension des mécanismes psychobiologiques de l’addiction à la cocaïne
Drug addiction is characterized by pathological drug seeking and taking, maintained despite their negative consequences. This is a chronic pathology, withdrawal attempts being unsuccessful in most cases. Cocaine addiction develops in about 15 to 20 % of habitual users. For cocaine, therapeutic options are lacking, which could be explained by the relatively poor understanding of the neurobiological mechanisms underlying cocaine addiction to date. Clinical and preclinical studies propose that addiction results from an imbalance between the cortical-subcortical circuits that process motivational value of drug-related stimuli versus those involved in cognitive inhibitory control. Hierarchical sequential changes in distinct, but interconnected circuits, including the basolateral amygdala, the nucleus accumbens and the prefrontal cortex could be at the core of pathological incentive processes and difficulty to control craving and drug taking. Studying addiction at the neuronal circuit level faces many challenges. Technically limited in humans, it can benefit from animal models, but only if they properly capture dimensions of the pathology. Over the last ten years, such models have been developed, but exclusively in rats. However, tools for a refined functional exploration of neuronal circuits have been established mostly in mice, and until recently they have begun to be explored in rats. In addition, another main challenge is the ability to investigate functional connectivity in real time in behaving animals. My thesis work had two objectives: 1. Studying markers of functional connectivity in rats showing a cocaine addiction-like behavior (Addict) or not (Non-addict). Our model of cocaine addiction allows identifying 15-20% of rats that show a high motivation for cocaine, a difficulty to limit drug seeking and that maintain drug taking despite negative consequences. These extreme behaviors occur after prolonged cocaine self-administration and despite that these rats have used a comparable amount of cocaine as compared to the others. In vivo, multi-site electrophysiology recordings, applied to single units or local field potentials, is a tool of choice for studying functional connectivity in rodents. A technical challenge has been to adapt and couple it to our model of cocaine addiction in the rat. We have evidenced significant differences in connectivity between Addict and Non-addict rats, which suggest a default of functionality of the medial prefrontal cortex in the Addict rats. 2. Studying the role of the prelimbic cortex (PL) in cocaine self-administration behavior in the rat. The canonical role of the PL in exclusively promoting drug seeking was recently questioned, with studies involving it also in inhibition of drug seeking. Our first goal was to clarify this role of the PL in early cocaine self-administration, i.e. before addiction-like behavior develops: understanding its early role to eventually compare it to its late role and whether an addiction-like behavior develops or not. We have shown that optogenetic PL inactivation can decrease or increase cocaine seeking in the same individual, according to experimental contingencies. PL neurons project to several remote structures. To study the role of these different neuronal pathways, we have worked in establishing optogenetic tools for the manipulation of specific neuronal pathways, in the rat, for which they are still poorly developed. My thesis work contribute, both theoretically and technically, to the understanding of the psychobiology of cocaine addiction

Comparative genomics of shared processes can provide insights into plant-parasitic nematode biology that would otherwise be intractable. Caenorhabditis elegans, together with the information and resources available for this model species, was used in Globodera pallida. This cyst nematode infects potato plants and is considered an agricultural pest worldwide.

Social cognition has not been studied in PSP, despite its clinical importance with regard to patients’ progressive decline in independence and communication. This thesis focuses on the extent and neural basis of social cognition in PSP. Cognitive function was assessed in multiple domains including social cognition, executive function and perception, at baseline and after one year. At baseline, subjects underwent structural magnetic resonance imaging and saccadometry. Patients were poor at both emotion recognition and theory of mind tasks in visual and auditory modalities, compared with matched controls. Social cognition correlated with global cognitive decline but was not attributable to perceptual disturbance and was independent if executive function. The latency of visually evoked saccades correlated with global and social cognitive performance. Regression analysis revealed latency as the best predictor of cognitive function, above disease duration and motor function. Voxel based morphometry of grey and white matter confirms that areas previously implicated in social cognition were atrophic in PSP. Moreover, this atrophy correlated with social cognition dysfunction, implying a functional association. In summary, social cognition is an integral part of the cognitive syndrome of PSP, and is associated with focal atrophy of regions associated with normal social cognition.

Neuroscience is increasingly part of the national dialogue regarding mental health. The field of interpersonal neurobiology may offer a framework for helping mental health professionals identify and apply the most relevant neuroscience principles to counseling. This study explored mental health professionals’ experiences learning IPNB. I conducted semi-structured interviews with participants (n = 6), all of whom were licensed mental health professionals and had completed a year-long study in the application of IPNB through Nurturing the Heart with the Brain in Mind. I analyzed the data, along with a research partner, according to interpretative phenomenological analysis (IPA) protocol. Four super-ordinate themes emerged from the analysis: (1) learning process as dynamic and engaging, (2) deepening knowledge and understanding of self and others, (3) personal and professional growth, and (4) impact on therapeutic practice. A number of sub-ordinate themes also emerged through the analysis , including experiential learning; learning through group process; influence of the past on the present; increased understanding of the change process; increased compassion, empathy, and acceptance for self and for others; increased confidence; using IPNB to educate clients; using IPNB to conceptualize clients; and using IPNB to select interventions. Finally, I identified three higher-order constructs that appeared embedded within and across themes: learning as ongoing, person of the participant, and person of the instructor. The findings in this study suggest that participants’ learning of IPNB had a significant impact on their personal and professional development, specifically in areas related to characteristics of effective counselors. The findings also suggest that these meaningful changes occurred in a learning environment characterized by emotional engagement, experiential activities, and group process. Limitations to this research, as well as further discussion of the results are included. Implications for future research, clinical practice, and counselor education are also offered.

It has been proposed that the spectacular olfactory learning capabilities of the rat may prove useful in the development of rodent models of human amnesia. In particular, it has been suggested that rats show a 'primate-like' learning capacity when tested with olfactory (rather than visual or auditory) cues; and that this learning is sensitive to damage to brain stuctures considered critical in the human amnesic syndrome. The aim of this thesis is to evaluate and exploit these claims in the investigation of the neurobiology of rodent olfactory learning. In a series of experiments, an automated 'olfactory maze' is developed for the demonstration and measurement of rodent olfactory learning capacity, and parallels between rodent and primate learning capabilities are investigated. It is concluded that the suggestion that rats form 'primate-like' learning sets (and therefore learn complex abstract rules) when trained on a series of novel olfactory problems is unlikely to be correct. Investigation of the effects of hippocampal and dorsomedial thalamic nucleus (DMN) lesions on olfactory learning do not support the hypothesis that olfactory learning is sensitive to damage to the structures considered critical in human amnesia; hippocampal lesions are without effect, and DMN lesions appear to cause a perceptual, rather than cognitive, abnormality. Infusion of the N-methyl D-aspartate receptor in antagonist AP5, widely used as a tool to investigate the role of synaptic plasticity in learning, is also without effect. Hippocampally lesioned animals are, however, demonstrated to be impaired in a spatial reference memory task. On this basis, it is concluded that rodent olfactory learning does not constitute a useful model for the investigation of the biology of human amnesia.

Epigenetic mechanisms regulate gene expression and mediate interactions between genetic factors and environmental exposures. The enzymes responsible for epigenetic regulation may thus be important therapeutic targets for multifactorial neurological syndromes. KDM1A, the first histone lysine demethylase to be discovered, regulates the maturation of neurons and is inactivated by non-selective monoamine oxidase inhibitors such as the antidepressant tranylcypromine. This thesis entails the development of small-molecule tools to study KDM1A in a neurobiological context, with application towards the development of new therapeutic agents. We leveraged the chemical scaffold of tranylcypromine to generate novel KDM1A inhibitors. In chapter 2, we profile these analogs using biochemical, cellular, and in vivo assays. We show that RN1 potently inhibits KDM1A, exhibits high brain uptake, and affects the behavior of mice in a novel object recognition assay. Thermal shift assays reveal engagement of KDM1A by tranylcypromine in the brains of systemically-treated rats, suggesting that inhibition of KDM1A by non-selective antidepressants in a clinical setting warrants further examination. We sought to discover new mechanisms of KDM1A inhibition in order to gain further selectivity versus the monoamine oxidases. In chapter 3, we present outcomes of a high-throughput screen and secondary assays which reveal a predominant mode of KDM1A inhibition based on thiol-reactivity, and widespread contamination of test compounds by elemental sulfur. We show that KDM1A is inhibited by the FDA-approved drug disulfiram, and disclose two novel scaffolds for medicinal chemistry development. In chapter 4, we further profile the thiol-reactivity of KDM1A and show that catalytically-generated hydrogen peroxide negatively regulates demethylase activity. MALDI-TOF mass spectrometry indicates that hydrogen peroxide blocks labeling of cysteine 600, which we propose forms an intramolecular disulfide bond with cysteine 618. This activity-dependent regulation is unique among histone-modifying enzymes but consistent with redox sensitivity of epigenetic regulators. KDM1A may use this thiol/disulfide switch as a mechanism to sense other cellular oxidants, such as the monoamine neurotransmitter dopamine.
Chemistry and Chemical Biology

Upon an inflammation the immune system signals the brain by secreted cytokines to elicit central nervous responses such as fever, loss of appetite and secretion of stress hormones. Since the blood brain barrier, (BBB) protects the brain from unwanted material, molecules like cytokines are not allowed to cross the barrier and enter the brain. However, it is clear that they in some way can signal the brain upon an inflammation. Many suggestions concerning this signaling has been made, one being that cytokines bind to receptors on the endothelial cells of the blood vessels of the brain and trigger the production of prostaglandins that can cross the BBB. This conversion is catalyzed by the enzyme cyclooxygenase-2, (COX-2), which is induced by transcription factors like NF-κB in response to cytokines. One of the central nervous responses to inflammatory stimuli is activation of the HPA-axis whose main purpose is glucocorticoid production. Glucocorticoids inhibit the inflammatory response by suppressing gene transcription of pro-inflammatory genes including those producing prostaglandins through direct interference with transcription factors such as NF-κB or initiation of transcription of anti-inflammatory genes like IκB or IL-10. It has however not been clear if glucocorticoids can target the endothelial cells of the brain in order to provide negative feed-back on the immune-to-brain signaling, and in that way inhibit central nervous inflammatory symptoms. An anatomical prerequisite for such a mechanism would be that the induced prostaglandin production occurs in cells expressing GR. This has however never been demonstrated. Here I show that a majority of the brain endothelial cells expressing the prostaglandin synthesizing enzyme COX-2 in response to immune challenge also express the glucocorticoid receptor, (GR). This indicates that immune-to-brain signaling is a target for negative regulation of inflammatory signaling executed by glucocorticoids and identifies brain endothelial GR as a possible future drug target for treatment of central nervous responses to inflammation such as fever and pain.

During neural development, signaling molecules and networks of expressed transcription factors cooperate to control cellular fate. Chromatin acting factors are essential players in cell proliferation and differentiation events. PHF2 is a histone demethylase, previously associated with cancer and autism spectrum disorder (ASD) but despite its clinical relevance its function during neural development remains unclear. PHF2 belongs to the KDM7 family of demethylases. It harbors an N-terminal plant homeodomain, (PHD) a domain that was shown to be associated with methylated lysine residues and an enzymatically active Jumonji-C (JmjC) domain responsible for their demethylase activity towards H3K9me and H3K9me2. PHF2 has been proposed to be a transcriptional coactivator, although, its genomic localization still remains unclear. To address the function of this protein during early neurogenesis constitutes the major goal of this Ph.D. thesis. To do so, we are using in vitro (cortical neural stem cells, NSC) and in vivo (the chick embryo neural tube) models. We demonstrated that this histone demethylase binds mainly promoter regions along the genome and more specifically cell cycle gene promoters facilitating their transcription in NSCs. PHF2 was shown to regulate genes involved in G1-S transition (E2f2/3/7/8, Cdc7, Cdc25a, Cdk4, Mcm3/4/8), DNA replication (Orc1/2/6, Pcna), mitosis (Cdk1, Smc2/3/4, Aurkb, Topo2a), as well as chromatin activity (Cenpa, Kdm1b, Hat1, Parp1, Prmt5). In addition, we demontrated that this demethylase colocalizes with H3K4me2/3 marks, partially colocalizes with E2F1 and E2F4 transcription factors and mediates H3K9 demethylation at global and promoter levels. Moreover, PHF2 binds to the centromeric and pericentromeric regions and requiring its catalytic activity suppresses unprogrammed transcription from satellite repeats. In that way, PHF2 allows neural stem cells proliferation and preserves heterochromatin integrity during progenitor expansion. We also showed that PHF2 interacts with heterochromatic components such as the histone methyltransferase SUV39H1 and the HP1-binding protein 3. Furthermore, PHF2 fine-tunes H3K9 methylation levels, ensuring genome stability and chromatin homeostasis, as we observed that its lack of function leads to γH2Ax and R-loops accumulation in NSCs. Interestingly, we demonstrated that PHF2 is essential for neural progenitor self- renewal in the chick embryo neural tube and for neural subpopulation specification. To conclude, this work helps to move forward our understanding of the multiple crosstalks between epigenetics and developmental programs.
Durante el desarrollo neural, los factores reguladores de la actividad de la cromatina son esenciales en el control de la proliferación y diferenciación de las células. PHF2 es una desmetilasa de histonas, asociada a cáncer y a trastornos del espectro autista (ASD) cuya función en el desarrollo neural no ha sido estudiada. PHF2 pertenece a la familia de desmetilasas KDM7. Contiene un dominio PHD, capaz de unirse a residuos de lysinas metiladas y un dominio Jumonji-C (JmjC) enzimáticamente activo, responsable de la actividad desmetilasa hacía las marcas H3K9me y H3K9me2. PHF2 ha sido propuesta como un activador transcripcional pero su localización genómica no ha sido descrita. El objetivo principal de esta tesis doctoral es abordar la función de esta desmetilasa de histonas durante la neurogénesis temprana. Para ello, hemos usado modelos in vitro (progenitores neurales de córtex, NSCs) e in vivo (el tubo neural del embrión de pollo). Nuestros resultados han permitido identificar los lugares de unión de PHF2 en el genoma, esencialmente promotores y más específicamente promotores de genes de ciclo celular facilitando su transcripción. Además, esta desmetilasa colocaliza con las marcas H3K4me2/3, media desmetilación de las marcas H3K9 a nivel global y en promotores. Los experimentos realizados han demostrado que PHF2 se une a las regiones centromérica y pericentromérica y así mantiene niveles bajos de la transcripción de las secuencias repetidas. De esta forma preserva la integridad de la heterocromatina, asegurando la estabilidad genómica y la homeostasis de la cromatina. Estos resultados han sido validados en nuestro modelo in vivo; en el tubo neural, hemos demostrado que PHF2 es esencial para la proliferación y el mantenimiento de la pluripotencia de los progenitores, así como para la especificación de los diferentes tipos de las poblaciones neurales. En resumen, el trabajo presentado ayuda a avanzar en el conocimiento de las múltiples interacciones moleculares entre los programas de desarrollo y la epigenética.

L'épilepsie affecte des millions de patients dans le monde. Les traitements disponibles sont symptomatiques, ils per récepteur mGlu7 du glutamate dans la modulation non seulement de l’excitabilité, mais également de l'hypersynchronisation des réseaux de neurones, deux facteurs cruciaux dans les crises d'épilepsie. J'ai parachevé ces découvertes qui ont été à l’origine d’une première publication (Tassin, Girard et al. 2016).A l’aide d’un nouvel agoniste du récepteur mGlu7, le LSP2-9166, lors de ma thèse j'ai ensuite étudié l’impact de ce récepteur dans différents modèles d’épilepsie chez la souris. Deux modèles complémentaires ont été utilisés : le kindling (embrasement), modèle chimique induit par le pentylènetétrazol (PTZ) qui sensibilise le cerveau jusqu’à générer des crises tonico-cloniques généralisées, et l’injection intra-hippocampique de kainate, mimant l’épilepsie mésiale du lobe temporal chez l'homme.Dans un premier temps j'ai observé une atténuation de la progression de la sévérité des crises dans le modèle de kindling au PTZ, sous l’activation du récepteur mGlu7. Cet effet a été corrélé à une inflammation, et une activation microgliale et astrocytaire plus faibles. Dans le modèle d’injection intra-hippocampique de KA, considéré comme pharmaco-résistant, l’activation du récepteur mGlu7 pendant la période d’épileptogenèse a augmenté la durée des périodes interictales et diminué la durée des crises ainsi que la réorganisation neuronale. Une fois les crises chroniques installées, l’activation aigu du récepteur mGlu7 a diminué le nombre de crises aussi fortement que le diazépam couramment utilisé dans le cadre clinique. Pour finir, des injections chroniques de LSP2-9166 chez des animaux naïfs (non épileptiques) n’engendrent pas de déficit cognitif ou comportemental détectables, ni de modification du niveau d’ARNm du récepteur mGlu7. L’activation du récepteur mGlu7 offre donc une cible stratégique dans nos deux modèles.Ces travaux permettent une meilleurmettent de traiter les crises sans pour autant éviter la progression de la maladie et présentent de lourds effets secondaires. La découverte de nouvelles cibles thérapeutiques et de nouveaux composés reste primordiale pour dépasser les limites des stratégies thérapeutiques actuelles. Au début de ma thèse, des études précédentes avaient montré une implication due compréhension du rôle du récepteur mGlu7 dans l’épileptogenèse. Ils participent ainsi à la recherche de futurs traitements. antiépileptiques adéquats
Epilepsy affects millions of patients worldwide. The available treatments are symptomatic, they treat seizures without preventing the progression of the disease and have heavy side effects. The discovery of new therapeutic targets and new compounds is therefore essential to overcome the limitations of current therapeutic strategies. Previous studies have demonstrated substantial involvement of the mGlu7 receptor in modulating not only excitability but also hypersynchronization of neural networks, two crucial factors affecting epileptic seizures. These discoveries were at the origin of a first publication that I completed at the beginning of my thesis (Tassin, Girard et al., 2016).Using a new mGlu7 receptor agonist, LSP2-9166, in my thesis I then studied the impact of this receptor in different epilepsy models in mice. Two complementary models were used: kindling, a chemical model induced by pentylenetetrazol (PTZ) which sensitizes the brain to induce generalized tonic-clonic seizures, and intra-hippocampal injection of kainate, mimicking mesial temporal lobe epilepsy in humans.At first, I observed an attenuation of the progression of the seizures severity in the PTZ kindling model, under the activation of the mGlu7 receptor. This effect was correlated with weaker inflammation, and microglial and astrocytic activation. In the intra-hippocampal injection model of KA, considered as drug-resistant, activation of the mGlu7 receptor during the epileptogenesis period increased the duration of interictal periods and decreased the duration of seizures as well as neuronal reorganization. Once chronic seizures were established, acute activation of the mGlu7 receptor decreased the number of seizures as strongly as diazepam, commonly used in clinical settings. Finally, chronic injections of LSP2-9166 into naive (non epileptic) animals do not generate any detectable cognitive or behavioral deficits or changes in mGlu7 receptor mRNA level. The activation of the mGlu7 receptor thus presents a strategic target in our two models.This work provides a better understanding of the role of the mGlu7 receptor in epileptogenesis. It participates in the search for future more adequate treatments

Both schizophrenia and bipolar disorder are characterised by deficits in cognitive function, particularly in those executive functions subserved by the prefrontal cortex. In order to further our understanding of the neuropathophysiology of cognitive deficits in psychiatric disorders, this thesis examined structural and functional changes in the prefrontal cortex (PFC) in rodent models mimicking some aspects of schizophrenia and bipolar disorder. Chosen models were subchronic phencyclidine (PCP), chronic administration of corticosterone to flatten the glucocorticoid rhythm (CORT) and maternal immune activation (MIA). These models mimic glutamate hypofunction, hypothalamo-pituitary adrenal axis dysfunction and maternal infection, respectively. Behavioural studies established that PCP induced a selective deficit in attentional set shifting whilst CORT and MIA induced reversal learning deficits. In vitro electrophysiological studies established a novel model for measuring synaptic transmission in the infralimbic (IL) region of the medial prefrontal cortex (mPFC). Synaptic transmission was shown to be mediated by glutamate and γ-aminobutyric acid (GABA) and to be subject to inhibitory modulation by serotonin (5-HT) and noradrenaline (NA). Differential changes in both basal synaptic transmission and in the monoaminergic modulation of synaptic transmission were evident in the three animal models. Immunohistochemical studies showed that the three animal models induced differential changes in the numbers of particular subtypes of GABAergic interneurones, suggesting that GABAergic activity in the mPFC was altered. These studies demonstrate that models of select features of psychiatric disorders, glutamate hypofunction, HPA axis dysfunction, and prenatal infection, induce deficits in executive function present in psychiatric disorders. These differential behavioural outcomes might be explained by differential changes in synaptic transmission in the mPFC and in the expression of GABAergic interneurones in the mPFC induced in the three models.

Dissertation (DSc)-- Stellenbosch University, 2008.
ENGLISH ABSTRACT: The overall aim of these studies was to investigate selected aspects of psychopathology, neurobiological abnormalities and treatment in schizophrenia. The following topics were researched: 1. Psychopathology: We explored the symptom structure of schizophrenia by means of principal components and factor analysis in two separate samples. a. The first study investigated the nature of symptoms in patients with a first-episode of schizophrenia, in a large cohort of patients who were participating in a multinational clinical trial. We compared our findings with similar analyses previously conducted in multi-episode schizophrenia patients. b. We then assessed the influence of culture on the symptom structure of schizophrenia by conducting a principal components and factor analysis of the symptom ratings in a large sample of South African Xhosa patients with schizophrenia, and comparing the results with those in other parts of the world. c. We investigated the occurrence of co-morbid depressive and anxiety symptoms, and their demographic and clinical correlates. The sample for this study comprised acutely psychotic patients who were participants in clinical drug trials conducted at our centre. d. To explore the relationships between obsessive-compulsive disorder and schizophrenia, we conducted a review of the relevant literature. 2. Neurobiological abnormalities: a. We performed a series of studies to investigate disorders of water homeostasis and vasopressin secretion in schizophrenia. To test the hypothesis that acutely psychotic patients have disordered regulation of water homeostasis, we applied a dynamic suppression test - a water loading test, with assessment of excretory capacity (including arginine vasopressin assay) in acutely psychotic patients. To evaluate whether a subset of patients with schizophrenia and co-morbid disordered water homeostasis sustained cerebral damage as a consequence of water intoxication we did the following experiment: We identified a cohort of subjects with schizophrenia and disordered water homeostasis and compared them with patients with schizophrenia without disordered water homeostasis in terms of cerebral ventricular size and cognitive function. To assess the prevalence of disordered water homeostasis in a long-term inpatient sample of psychiatric patients we conducted serum sodium screening tests. Those subjects with dilutional hyponatraemia were then further investigated for dysregulation of water homeostatic mechanisms. b. We studied neurological soft signs in a sample of subjects with first-episode schizophrenia followed up over a two year period. We investigated their occurrence, relationships to psychiatric symptoms and medication effects, their temporal stability and their outcome correlates. We also investigated their potential to predict outcome in schizophrenia 3. Treatment aspects A great deal of our work has focussed on the pharmacological treatment of schizophrenia. The following aspects of treatment are included in this thesis: a. Treatment effects on psychiatric symptoms: i. To assess the effects of ethnicity on treatment outcome in schizophrenia we compared the acute response to antipsychotic treatment in 3 ethnic groups, namely blacks, coloureds and whites. We included patients in this analysis who had participated in clinical trials in our department as well as the Department of Psychiatry in the University of the Free Sate. Patients had been treated under blinded conditions over a 6-week period. ii. After discussions with the late Dr David Horrobin, who had pioneered possible applications of the omega-3 fatty acids in the treatment of various psychiatric disorders, we became interested in further investigating the potential of this group of compounds as an affordable adjunct to treating schizophrenia. We assessed the antipsychotic potential of the omega-3 fatty acid, ethyl-eicosapentaenoic-acid (e-EPA) supplementation versus placebo supplementation in a small sample of subjects with schizophrenia who had been only partially responsive to antipsychotic treatment previously. We also conducted a review of the literature to evaluate the evidence for efficacy for the omega-3 fatty acids in schizophrenia according to published studies. b. Treatment effects on neurological abnormalities: i. In a single-blinded controlled study we compared a new generation antipsychotic to a conventional antipsychotic in the treatment of tardive dyskinesia (TD). This was a long-term (1 yr) study in patients with chronic schizophrenia and established tardive dyskinesia. ii. We also assessed the effect of omega-3 fatty acid (e-EPA) supplementation in treating TD. This was conducted in a larger sample (n=84) of patients with chronic schizophrenia and established TD. The blinded, placebo-controlled phase was 12 weeks. This was followed by an open-label extension for 40 weeks. c. Conventional versus new generation antipsychotic agents. Several evidence-based literature reviews of the efficacy and tolerability of the new generation of antipsychotics compared to the conventional agents were conducted. Some multinational, randomised, controlled clinical trials in which the author was principal investigator, are included in this thesis. Also, studies addressing patients with partial treatment refractoriness are included, as well as studies of the effects of antipsychotics on depressive symptoms, body mass and glycaemic control. Finally, we have included a pharmacoeconomic study comparing a conventional antipsychotic (haloperidol) with a new generation antipsychotic (quetiapine) in partially refractory patients in a South African setting. Findings and conclusions: 1. Psychopathology: Our studies demonstrated that the factor structure for the symptoms of schizophrenia is replicable across samples, and is not greatly influenced by ethnic and cultural factors. However, changes in the factor structures do occur over time. There are symptom domains that are present in first-episode schizophrenia but disappear as a distinct entity as the illness becomes chronic. Particularly, a motor component is evident in untreated patients, but disappears after initiation of treatment. We found that depression and anxiety are common co-morbid symptoms in schizophrenia, and have important clinical and outcome correlates. Depressive symptoms in the acute psychotic phase of schizophrenia are associated with a favourable prognosis and diminish as the symptoms of psychosis improve in response to antipsychotic treatment. However, persistent depressive symptoms are associated with a poorer prognosis, and require additional therapeutic intervention. 2. Neurobiological abnormalities: We investigated the occurrence of disordered water regulation in a population of psychiatric inpatients, and conducted further investigations on those identified, in order to establish mechanisms involved. Polydipsia and the syndrome of inappropriate antidiuretic hormone secretion (SIADH) were found to occur in a subset of patients with schizophrenia, and are associated with acute psychosis, as well as with some psychotropic medications. These patients are characterised by more severe cognitive impairment and evidence of cerebral atrophy. The condition can become life-threatening in the presence of other factors impeding water excretion, particularly thiazide diuretics. Neurological soft signs were investigated in a sample of patients with a first-episode of schizophrenia. These soft signs appear to be trait-like (present early in the illness, and stable over time), except for a motor sequencing factor. Patients performing poorly on this latter group of tests have a longer duration of untreated psychosis, and are at significant risk for developing TD. 3. Treatment aspects: Our studies suggest that there are important ethnic differences in antipsychotic treatment response, but that these differences could be explained by a number of environmental and biological factors. As was found with many studies worldwide, we found that the new generation antipsychotics have important efficacy and safety advantages over their predecessors. Risperidone was as effective as haloperidol in first-episode psychosis, but with a more favourable side-effect profile in terms of reduced extrapyramidal symptoms. Quetiapine treatment in partially refractory patients resulted in more responders compared to haloperidol, and fewer extrapyramidal symptoms. However, evidence of a different side-effect profile is emerging. Of particular concern is the finding that some of the new antispychotics cause weight gain, glucose intolerance and dyslipidaemias. We found that one novel antipsychotic, quetiapine, was not associated with significantly more weight gain or disordered glucose metabolism that a conventional agent, haloperidol. The omega-3 fatty acids, particularly EPA may have a role in the treatment of various psychiatric disorders. Our studies provided mixed results – the first found a significant beneficial effect on psychotic symptoms and dyskinesia scores for EPA supplementation, while the second failed to demonstrate a beneficial effect on TD or psychotic symptoms. We explored the early treatment response in first-episode psychosis and found, unlike that reported in multi-episode patients, some patients took a long time to respond. We also found that early treatment response was a significant predictor of later remission, as was duration of untreated psychosis, educational level and baseline excitement factor scores. Finally, our pharmacoeconomic study conducted for South African circumstances in patients with a partial response to conventional antipsychotic treatment showed cost-neutrality or cost-benefits for quetiapine compared with haloperidol treatment for direct costs.
AFRIKAANSE OPSOMMING: Die oorkoepelende doel van hierdie studies was om geselekteerde aspekte van psigopatologie, neurobiologiese abnormaliteite en behandeling in skisofrenie te ondersoek. Die volgende onderwerpe is nagevors: 4. Psigopatologie: Ons het die simptoomstruktuur van skisofrenie ondersoek deur middel van hoofkomponent- en faktoranalise in twee aparte steekproewe. a. Die eerste studie het die aard van simptome in pasiënte, met ʼn eerste-episode van skisofrenie, ondersoek in ʼn groot kohort van pasiënte wat deelgeneem het aan ʼn multi-nasionale kliniese proefneming. Ons het ons bevindinge vergelyk met soortgelyke analises wat voorheen gedoen is in multi-eposode skisofrenie pasiënte. b. Hierna het ons die invloed van kultuur op die simptoom struktuur van skisofrenie geassesseer deur ʼn hoofkomponent- en faktoranalise van die simptoomtellings uit te voer in ʼn groot steekproef van Suid-Afrikaanse Xhosa pasiënte met skisofrenie en die resultate te vergelyk met bevindinge in ander dele van die wêreld. c. Ons het die voorkoms van ko-morbiede depressiewe en angssimptome ondersoek, asook hul demografiese en kliniese korrelate. Die steekproef vir hierdie studie het bestaan uit akute psigotiese pasiënte wat deelnemers was in ʼn kliniese geneesmiddel proef wat uitgevoer is by ons sentrum. d. Om die verband tussen obsessief-kompulsiewe steurnis en skisofrenie te verken, het ons ʼn oorsig van die relevante literatuur gedoen. 5. Neurobiologiese abnormaliteite: a. Ons het ʼn reeks studies uitgevoer om steurnisse in water homeostase en vasopressien sekresie in skisofrenie te ondersoek. Om die hipotese dat akute psigotiese pasiënte versteurde regulering van water homeostase het te ondersoek, het ons ʼn dinamiese onderdrukkingstoets toegepas – ʼn water ladingstoets, met assessering van ekskresiekapasiteit (insluitend arginien vasopressien essai) in akute psigotiese pasiënte. Om te evalueer of ʼn onderafdeling van skisofrenie pasiënte met ko-morbiede versteurde water homeostase serebrale skade opgedoen het as gevolg van water intoksikasie, het ons die volgende eksperiment uitgevoer: Ons het ʼn kohort deelnemers met skisofrenie en versteurde water homeostase geïdentifiseer en hulle vergelyk met skisofrenie pasiënte sonder versteurde water homeostase in terme van serebrale ventrikulêre grootte en kognitiewe funksionering. Om die voorkoms van versteurde water homeostase in ʼn langtermyn binne-pasiënt steekproef van psigiatriese pasiënte te bepaal, het ons serum natrium siftingstoetse uitgevoer. Deelnemers met hiponatremie is hierna verder ondersoek vir disregulering van water homeostatiese meganismes. b. Ons het neurologiese sagte tekens in ʼn steekproef van deelnemers met eersteepisode skisofrenie bestudeer en opgevolg oor ʼn twee jaar tydperk. Ons het hulle voorkoms, verwantskappe met psigiatriese simptome en medikasie effekte, hulle temporale stabiliteit en hul uitkoms korrelate ondersoek. Ons het ook hulle potensiaal om die uitkoms in skisofrenie te voorspel, ondersoek. 6. Behandelings aspekte ʼn Groot meerderheid van ons werk het gefokus op die farmakologiese behandeling van skisofrenie. Die volgende aspekte van behandeling is ingesluit in hierdie tesis: a. Behandelingseffekte op psigiatriese simptome: i. Om die effek van etnisiteit op behandelingsuitkoms in skisofrenie te assesseer, het ons die akute respons op anti-psigotiese behandeling in 3 etniese groepe vergelyk, naamlik swart, gekleurd, en wit. Ons het pasiënte wat deelgeneem het aan kliniese proefnemings in ons departement sowel as die Departement Psigiatrie van die Universiteit van die Vrystaan ingesluit in hierdie analise. Pasiënte is behadel onder geblinde toestande oor ʼn tydperk van 6 weke. ii. Na besprekings met wyle Dr David Horrobin, wie die moontlike toepassings van omega-3 vetsure in die behandeling van verskeie psigiatreise steurnisse gepionier het, het ons begin belangstel in verdere ondersoek na die potensiaal van hierdie groep samestellings as ʼn bekostigbare toevoeging in die behandeling van skisofrenie. Ons het die anti-psigotiese potensiaal van die omega-3 vetsuur, etieleikosapentanoësuur (e-EPA) supplementasie versus plasebo supplementasie ondersoek in ʼn klein steekproef van deelnemers met skisofrenie wat slegs gedeeltelik responsief was op anti-psigotiese behandeling in die verlede. Ons het ook ʼn literatuuroorsig gedoen om die bewyse vir die effektiwiteit vir die omega-3 vetsure in skisofrenie te evalueer volgens gepubliseerde studies. b. Behandelingseffekte op neurologiese abnormaliteite: i. In ʼn enkelblinde kontrole studie het ons ʼn nuwe generasie anti-psigotiese medikasie vergelyk met ʼn konvensionele anti-psigotiese medikasie in die behandeling van tardiewe diskinesie (TD). Hierdie was ʼn langtermyn (1- jaar) studie in pasiënte met chroniese skisofrenie en vasgestelde TD. ii. Ons het ook die effek van omega-3 vetsuur (e-EPA) suplementasie geassesseer in die behandeling van TD. Dit was gedoen in ʼn groter steekproef (n=84) van pasiënte met chroniese skisofrenie en vasgestelde TD. Die blinde, placebo kontrole fase was 12 weke. Dit is gevolg deur ʼn nie-geblinde ekstensie vir 40 weke. c. Konvensionele versus nuwe generasie anti-psigotiese agente. Verskeie bewys-gebaseerde literatuuroorsigte oor die effektiwiteit en toleransie van die nuwe generasie anti-psigotiese agente in vergelyking met die konvensionele agente, is gedoen. Sommige multi-nasionale, ewekansige, kontole kliniese proefnemings waarin die outeur die hoofnavorser was, is ingesluit in hierdie tesis. Verder, studies wat die pasiënte met gedeeltelike behandelingsweerstandigheid aanspreek, is ingesluit, sowel as studies oor die effekte van anti-psigotiese agente op depressiewe simptome, liggaamsmassa en glisemiese kontrole. Laastens, het ons a farmakoekonomiese studie ingesluit wat die konvensionele anti-psigotiese behandeling (haloperidol) met ʼn nuwe generasie anti-psigotiese behandeling (quetiapien) in gedeeltelik weerstandige pasiënte in ʼn Suid-Afrikaanse ligging vergelyk. Bevindinge en gevolgtrekkings: 4. Psigopatologie: Ons studies het gedemonstreer dat die faktor struktuur vir die simptome van skisofrenie herhaalbaar is oor steekproewe, en dat dit nie grootliks beïnvloed word deur etnisiteit en kulturele faktore nie. Veranderinge vind egter in die faktor strukture wel plaas met verloop van tyd. Daar is simptoom domeine wat teenwoordig is in eerste-episode skisofrenie, maar verdwyn as ʼn afsonderlike entiteit soos wat die toestand chronies word. Spesifiek, ʼn motoriese komponent is duidelik in onbehandelde pasiënte, maar verdwyn na die aanvang van behandeling. Ons het gevind dat depressie en angs algemene ko-morbiede simptome in skisofrenie is en het belangrike kliniese en uitkoms korrelate. Depressiewe simptome in die akute psigotiese fase van skisofrenie word geassosieer met ʼn gunstige prognose en verminder soos wat die simptome van psigose verbeter in repons op anti-psigotiese behandeling. Egter, volgehoue depressiewe simptome word geassosieer met ʼn swakker prognose en benodig addisionele terepeutiese intervensie. 5. Neurobiologiese abnormaliteite: Ons het die voorkoms van versteurde water regulering ondersoek in ʼn populasie van psigiatriese binne-pasiënte en verdere ondersoek ingestel op dié wie geïdentifiseer is, om die betrokke meganismes vas te stel. Polidipsie en en die sindroom van onvoldoende antidiuretiese hormoon sekresie (SIADH) is gevind om voor te kom in ʼn onderafdeling van pasiënte met skisofrenie, en word geassosieer met akute psigose sowel as met somige psigotropiese medikasie. Hierdie pasiënte word gekenmerk deur meer ernstige kognitiewe beperking en bewyse van serebrale atrofie. Die toestand kan lewensbedreigend raak in die teenwoordigheid van ander faktore wat water ekskresie hinder, veral tiasied diuretikums. Neurologiese sagte tekens is ondersoek in ʼn steekproef van pasiënte met eerste-episode skisofrenie. Hierdie sagte tekens blyk om kenmerkend (teenwoordig vroeg in die siekte, en stabiel oor tyd) te wees, behalwe vir ʼn motoriese volgorde faktor. Pasiënte wat swak vaar op die laasgenoemde groep toetse, het ʼn langer durasie van onbehandelde psigose, en het ʼn beduidende risko om TD te ontwikkel. 6. Behandeling aspekte: Ons studies stel voor dat daar ʼn belangrigke etniese verskil is in anti-psigotiese behandelingsrespons, maar dat hierdie verskille verduidelik kan word deur ʼn aantal omgewings- en biologiese faktore. Soos wat gevind was vir verskeie studies wêreldwyd, het ons gevind dat die nuwe generasie anti-psigotiese agente belangrike effektiwiteit- en veiligheidsvoordele het bo hulle voorgangers. Risperidoon was net so effektief as haloperidol in eerste-episode psigose, maar met ʼn meer gunstige newe-effkte profiel in terme van verminderde ekstrapirimidale simptome. Quetiapien behandeling in veral refraktêre pasiënte het gelei tot meer respondeerders vergeleke met haloperidol, en minder ekstra pirimidale simptome. Alhoewel, bewyse van ʼn verskillende newe-effekte profiel is besig om na vore te kom. Van spesifieke belang is die bevinding dat sommige van die nuwe anti-psigotiese agente gewigstoename, glukose intoleransie en dyslipidemie veroorsaak. Ons het gevind dat een nuwe anti-psigotiese agent, quetiapien, nie geassosieer was met enige beduidende meer gewigstoename of versteurde glukose metabolisme as ʼn konvensionele agent, haloperidol, nie. Die omega-3 vetsure, spesifiek EPA mag moontlik ʼn rol in die behandeling van verskeie psigiatriese versteurings hê. Ons studies het gemengde resultate voorsien – die eerste het ʼn beduidende voordelige effek op psigotiese simptome en diskinesie tellings vir EPA supplementasie gevind, terwyl die tweede nie ʼn voordelige effek op TD of psigotiese simptome gevind het nie. Ons het die vroeë behandelingsrespons ondersoek in eersteepisode pasiënte en het gevind, in teenstelling met dit wat gerapporteer word in multi-episode pasiënte, dat sommige pasiënte ʼn lang tyd geneem het om te reaggeer. Ons het ook gevind dat vroeë behandelingsrespons ʼn beduidende voorspeller was van latere remissie, so ook die durasie van onbehandelde psigose, opvoedingspeil, en basisvlak opwindings-faktor tellings. Laastens het ons farma-ekonomiese studie, wat uitgevoer is vir Suid-Afrikaanse omstandighede in pasiënte met ʼn gedeeltelike repons op konvensionele anti-psigotiese behandeling, koste-neutraliteit of koste-voordele aangetoon vir quetiapien vergeleke met haloperidol behandeling vir direkte onkostes.

This review will attempt to bring together several current fields of research on the topic of the olfactory system. The neurobiology of the system is fairly well understood in many different species, from insects to humans, which advanced significantly with the characterization of olfactory G-protein coupled receptors. These receptors bind odorant molecules and the sensory neurons carry the signal of that odor to the brain for further identification. Each olfactory sensory neuron only expresses a single type of receptor. The mechanisms for how this is done are not well understood. Epigenetics have been identified as a possible mechanism of inheritance of neurobiological and behavioral changes in response to odor fear-conditioning. Many different scientific disciplines will need to combine knowledge and further studies in order to discover how olfaction has evolved in varying ways across species having many different lifestyles.

Personality is something that sets every human being apart, yet it is something that has been quite hard to pinpoint. Recently, neuroscientists have begun pinning down the neural correlates of personality traits – with focus on the Big Five, sparking a whole new subfield within personality research, known as personality neuroscience. By using neuroscientific methods and techniques to find the underpinnings of the Big Five have led to a deeper and broader understanding of how genetics and the environment integrate into making individuals who they are. This research has also been helpful in the prediction of various outcomes e.g. academic performance and achievement and neuropsychological disorders. In this thesis, the supposed neural correlates of the Big Five are examined through thorough and critical investigations, where evidence from some of the existing relevant studies is reviewed and compared, as well as the different problems and complexities that the field of personality neuroscience is dealing with. The findings in this thesis shows that extraversion has neurobiological basis in the frontal areas of the brain, neuroticism with reduced volume in the frontal areas, agreeableness with frontoparietal areas that are related to theory of mind as well as temporal regions, conscientiousness with frontal parts that are associated with planning and goal-orientation, and openness/intellect with frontoparietal areas as well as subcortical regions, which have been linked with intelligence and creativity. However, some of the correlations were inconsistent and scattered and further research needs to be done. The analysis of academic achievement and performance, as well as neuropsychological disorders and the Big Five with neuroimaging as a method, have shown to be limited, thus much more research is needed.

The aim of this review paper was to investigate variations in sex differentiation, andalso, examine what neurobiological underpinnings there are to gender identity andgender dysphoria. In addition, the most extreme form of gender dysphoria,transsexuality, will be described from a neurobiological perspective but also discussedin terms of the classification from DSM-5. One theory considered on how genderidentity originates is the fact that the sexual differentiation of the brain and thedifferentiation of sexual organs develop during different time periods. Alterationswere displayed in a demonstration of male-to-female (MTF) and female-to-male(FTM) transsexuals that showed reversed results in cell number in a part of thehypothalamus, acronymized INAH-3 and reversal volume results in another region,acronymized BSTc. Likewise, differences in grey matter in the right putamendepended upon their natal gender. It can be concluded that there is biologicalevidence for sex differentiation and indications that lead science into consideringbiological components for gender dysphoria. This conclusion suggests for futureresearch questions focused more on the possible genetic factors of gender identity,also, consider larger sample sizes and more replications. There is still incompleteknowledge of what exactly constitutes an individual’s gender identity.

A Neurobiologia Vegetal é um recente ramo das ciências vegetais que objetiva esclarecer os complexos padrões de comportamento vegetal, no que se refere à percepção, processamento, armazenamento e transmissão de sinais na planta e entre plantas. A detecção de vizinhos, é uma capacidade que implica em auto reconhecimento, uma vez que um organismo só terá sucesso em interações competitivas se for capaz de auto/não-auto discriminação. Assim, objetivou-se com este trabalho verificar se raízes de ervilha (Pisum sativum) cv. Mikado apresentam crescimento diferenciado quando na presença de raízes da mesma planta, e de raízes de outras plantas, mas pertencentes ao mesmo genótipo, para que se possa averiguar sua capacidade de auto/não-auto discriminação. Além disso, avaliou-se também o crescimento da parte aérea para observar em que grau a presença de plantas vizinhas pode influenciar o desenvolvimento vegetativo de plantas de ervilha. Quatro dias após a germinação, plântulas de Pisum sativum cv. Mikado tiveram a raiz principal cortada 5 mm abaixo do hipocótilo. Passados sete dias, foram retiradas as raízes secundárias, deixando-se apenas duas raízes, de igual tamanho, por planta (split-root). Plantas com duas raízes iguais foram replantadas, com cada vaso contendo duas raízes da mesma planta (tratamento Auto) ou duas raízes de plantas diferentes (Tratamento Não-auto). Os vasos foram agrupados em tríades. O experimento foi mantido em estufa incubadora sob condições de temperatura e fotoperíodo controladas e após 18 dias foram feitas avaliações do crescimento da parte aérea e das raízes, através das medições de: altura da planta (cm), peso fresco de parte aérea e de raiz (g), peso seco de parte aérea e de raiz (g), área foliar (cm2), área radicular (cm2), comprimento total de raiz (cm) e diâmetro médio de raiz (cm). A análise dos dados considerando os valores médios de cada tríade revelou não haver diferença significativa entre os tratamentos Auto e Não-auto com relação ao crescimento de parte aérea. No que se refere ao crescimento da raiz, com exceção do diâmetro médio, as demais variáveis diferiram significativamente, sendo que as plantas pertencentes ao tratamento Auto apresentaram valores de peso seco, área superficial e comprimento total 36,71%, 27,84% e 23,18%, respectivamente, maiores do que as plantas do tratamento Não-auto. Ou seja, as plantas que não estavam sob competição apresentaram maior crescimento de raiz. No entanto, quando se observou o comportamento das plantas entre si, em cada tríade, verificou-se, no tratamento não-auto, diferenças visíveis de crescimento tanto em parte aérea como na raiz entre as três plantas que constituía cada tríade. Verificou-se também que a raiz de uma mesma planta cresceu diferentemente de acordo com a identidade da raiz vizinha. Enquanto que no tratamento auto as três plantas que constituíam uma tríade tinham aproximadamente o mesmo tamanho de parte aérea e raiz. Assim, podemos afirmar que o crescimento das plantas no tratamento não-auto foi influenciado pelas interações entre as raízes e mais que isto, foi dependente da identidade da raiz vizinha implicando em auto/não-auto discriminação e reconhecimento parental.
The Plant Neurobiology is a recent branch of plant science that aims to clarify the complex patterns of behavior vegetable, with respect to perception, processing, storage and transmission of signals in plant and between plants. The detection of neighbors, is a capacity that involves self-recognition and an individual will only be successful in competitive interactions if it is capable of self/non-self discrimination. Thus, the objective was to determine whether roots of pea (Pisum sativum) cv. Mikado grow differently in the presence of the same plant roots, and roots of other plants, but within the same genotype, so that we can determine its capacity for self/non-self discrimination. In addition, we assessed also the growth of the shoot to see to what degree the presence of neighboring plants can influence the vegetative growth of pea plants. Five days from germination, seedlings of Pisum sativum cv. Mikado had the seminal root severed 5 mm below the hypocotyl. After seven days, all but two of these roots were removed, leaving only two roots of equal size per plant (split-root). Plants with two equal roots were replanted, with each pot containing two roots of the same plant (treatment self) or two roots of different plants (Treatment non-self). Pots were grouped in triplets. The experiment was kept in an incubator camera under controlled conditions of temperature and photoperiod and after 18 days were evaluated for growth of shoots and roots. It was measure plant height (cm), fresh weight of shoot and root (g), dry weight of shoot and root (g), leaf area (cm2), root area (cm2), total length of root (cm) and average root diameter (cm). The analysis of data considering the average values of each triplets showed no significant difference between treatments self and non-self in relation to the growth of shoots. With respect to root growth, except for the diameter, the other variables differed significantly, and plants belonging to treatment self had values of dry weight, surface area and total length of 36.71%, 27.84 % and 23.18%, respectively, higher than the treatment plants non-self. That is, plants that were not under competition had higher root growth. However, when we observe the behavior of plants in each triplet, it was found that the treatment non-self, the plants had sizes of shoot and root differ. It was also found that the root of the same plant grew differently depending on the identity of neighboring roots. While in treatment self, the three plants that constituted a triplet had, approximately, the same size of shoot and root. Thus, we can say that the growth of plants to treatment non-self was influenced by the interactions between roots and more that this was dependent on the identity of neighboring roots implying self/non-self discrimination and kin recognition.

Autism spectrum condition (ASC) is a complex neurodevelopmental disorder that impacts physiological processes, cognition, functional behaviors, social-communication, and often has comorbidities. One approach gaining empirical support for ASC treatment is neurofeedback. Neurofeedback uses operant conditioning to normalize cerebral activity through auditory and visual reinforcement. Live Z-score Training (LZT) has become the latest advancement in neurofeedback. There is no published research to date on LZT neurofeedback in adulthood ASC. The purpose of this study was to evaluate LZT's impact on neuropsychological measures in an adult with ASC. A multiple baseline single-case research design was used with a convenience sample of one adult with ASC to evaluate the effects of 20 LZT sessions using the Conservative Dual Criterion visual inspection method as the primary form analysis. ADHD, mood stability, anxiety, depression, and ASC symptoms were significantly reduced according to the Neuropsych Questionnaire. The participant improved significantly on the CNS Vital Signs (CNVS) Neurocognitive measures of executive function, cognitive flexibility, reaction time, and complex attention. Also, the participant increased intelligence as measured by the Test of Nonverbal Intelligence. Lastly, the participant had changes in brain function according to quantitative electroencephalography and low-resolution brain electromagnetic tomography. CNVS processing speed was the only measure that did not significantly change. No adverse effects were reported. This study may lead to positive social change by providing a technologically advanced intervention for adults with ASC, which may improve their overall quality of life and promote self-sufficiency through adulthood.

INTRODUCTION To answer many complex and fascinating biological phenomena, we must go over or above (epi-) genetics because the DNA blueprint is identical in each of the abovementioned somatic cells. The mechanisms by which epigenetics affects so deeply the cell physiology are mediated by a large number of actors, most of them represented by covalently modified nucleotides and amino acids, non-coding RNAs and proteins. MeCP2 is an epigenetic reader able to bind to methylated and 5- hydroxymethylated cytosines. Despite all the initial evidences proposing a chromatin-repression role for MeCP2, many other functions have been demonstrated, including transcriptional activation, mRNA splicing regulation and protein synthesis modulation. Importantly, MeCP2 impairments are the primary responsible for RTT syndrome and have also been shown to be involved in several other disorders, albeit in very few patients, as Prader-Willi syndrome, Angelman syndrome, nonsyndromic mental retardation, and autism. AIMS To date, no MeCP2-regulated gene has been successfully targeted in order to improve the severe symptoms of RTT. In the present Doctoral Thesis we sought to identify new MeCP2 targets through different approaches with the purpose of expanding the knowledge of the impaired biological pathways in RTT. * In the first study we focused on a class of transcriptional regulators called long non-coding RNAs (lncRNAs). * In the second study we took advantage of RNA sequencing, a powerful high-throughput technique with the ability to detect very low amounts of transcript. Then, we proposed to investigate also the consequence of MeCP2 over-expression in a well-known developmental model such as the chicken embryo. RESULTS STUDY I DYSREGULATION OF THE LONG NON-CODING RNA TRANSCRIPTOME IN A RETT SYNDROME MOUSE MODEL * We found 701 lncRNAs that had a different expression pattern in wild-type and Mecp2-null brain with a score of <0.05 in the false discovery rate (FDR) test and a >1.5-fold expression change. Among the altered lncRNAs, downregulation of transcripts was predominant (520 of 701, 74%), whereas upregulation occurred in the minority of differentially expressed genes (181 of 701, 26%). * Following a selection of lncRNAs with a fold-change >2 that were associated with an annotated protein-coding gene involved in neuronal or glial functions, we validated two up-regulated lncRNAs, AK081227 and AK087060, in the Mecp2-null brain using qRT-PCR on independent samples. * We showed that AK081227 and AK087060 promoters were occupied by the MeCP2 protein in wild-type mouse brains. * We reported that the up-regulation of AK081227 in Mecp2-null mice was associated with a down-regulation of its host gene Gabrr2 in four brain regions (frontal cortex, hypothalamus, thalamus and cerebellum) (Pearson's correlation test = 0.44, p = 0.06). * In the case of AK087060, we found that the up-regulation of this 1ncRNA was correlated with an increase in the expression of its host gene Arhgef26 in the four studied brain regions (Pearson's correlation test = 0.41, p = 0.08). STUDY II RNA-SEQUENCING OF A RETT SYNDROME MOUSE MODEL REVEALS GLOBAL IMPAIRMENT OF IMMEDIATE-EARLY GENES EXPRESSION * We sequenced the transcriptome of Mecp2-null and control mice and we detected 1049 and 1154 differentially expressed genes in HIP and PFC, respectively. The ratio of up- and down-regulated genes was different between the two regions. In the HIP the ratio was favorable to the less expressed genes, being 388 (37%) and 661 (63%) the up- and down-regulated genes, respectively. On the other hand, in the PFC there were slightly more up-regulated genes, 630 (55%), compared to the down-regulated ones, 523 (45%). In addition we reported that only a small fraction of genes, 76 and 109, were up- and down-regulated, respectively, in both brain areas. * Gene Ontology (GO) analysis of differentially expressed transcripts revealed that both HIP and PFC up-regulated genes were enriched in neuronal function terms and, to a lesser extent, signal transduction ones. The scenario was similar for the down-regulated genes but in this case we found many inflammatory, apoptosis, oxidative stress and immune system-related terms. * We found several members of the immediate-early genes (IEGs) family to be up-regulated both in the PFC and HIP of Mecp2-null mouse. Consistent with the findings from the RNA-sequencing analysis in the HIP, qRT-PCR showed significant alterations in the expression of Fos, Junb, Egr2, Nr4a1, Npas4, Fosb and Egr1. Furthermore, Fos, Junb, Npas4 and Fosb were validated also in the PFC. * We demonstrated the binding of MeCP2 upon the regulatory regions of IEGs. In both PFC and HIP wild-type brain, we observed a reduction of MeCP2 occupancy upon the regions associated with high CpG content of Fos, Junb, Nr4a1, Npas4, Fosb and Egr1 promoters. We also found that the HIP chromatin was more accessible to MNase digestion in the Mecp2-null brain. * Then, we showed that four IEGs (Fos, Junb, Egr2, Npas4) displayed altered expression in Mecp2-null cultured neurons treated with forskolin. Precisely, this four IEG exhibited an aberrant kinetic of recovery to the basal state. One hour after forskolin withdrawal, Fos, Junb, Egr2 and Npas4 expression levels in the Mecp2-null hippocampal neurons continue to increase, while in wild-type they did not change or even decrease. The situation is the opposite in cortical neurons, where Fos, Junb, Egr2 and Npas4 are less expressed after forskolin withdrawal in Mecp2-null samples. * Finally, we evaluated whether the IEGs response was impaired in vivo as well. Indeed, we observed a significant increase of Junb expression in the hippocampus of Mecp2-null animals treated with kainic acid, when compared to treated wild type mice. STUDY III AN INCREASE IN MECP2 DOSAGE IMPAIRS NEURAL TUBE FORMATION * We detected the expression of both chicken MeCP2 (cMECP2) transcript and protein in a wide window of developmental stages. In addition, we showed that nuclear localization and the sequence of the region encompassing the methyl-CpG binding domain are conserved between human and chicken. * We found that the overexpression of MeCP2 in the neural tube of chicken embryos provokes an overall decrease in the number of proliferating BrdUpositive cells, with the most affected part being the ventricular zone. In addition, normal H3S1Op pattern along the lumen is disrupted upon MeCP2 overexpression. * Also, MeCP2 increase in dosage cause a clear decrease in the amounts of differentiated neuronal population located at the mantle zone, as it was demonstrated through immunostaining of neural tubes with TUJ1 and HUC/D, two neuronal-lineage restricted markers. Moreover, MeCP2 overexpression leads to a decrease of a neuroepithelial polarity marker such as N-cadherin. * Finally, we showed that one of the possible explanations of our phenotype is the increased cell death occurring upon MeCP2 increase in dosage. We reported an increment of apoptotic cells in MeCP2-overexpressing neural tubes immunostained with Caspase-3 and -8. Furthermore, we described also an increase of pyknotic cells number in MeCP2 electroporated neural tubes.
Introducción: El síndrome de Rett (RTT, OMIM#312750) fue por primera vez descrito en 1966 por el pediatra austriaco Andreas Rett. El síndrome de Rett causa retraso mental en 1 de cada 10000 niñas, lo que hace que sea la segunda causa de retraso mental en niñas. En 1999 en el laboratorio de Huda Zoghbi descubrieron las bases genéticas de la enfermedad. El 95% de los casos de Rett clásico se produce por mutaciones en MeCP2. Es interesante el hecho de que mutaciones que provocan el incremento de copias del gen MECP2 también llevan a enfermedades neurológicas, como es el caso del trastorno provocado por la duplicación de MeCP2. MeCP2 es una proteína nuclear, que se expresa en diferentes tejidos, pero es especialmente abundante en neuronas del sistema nervioso maduro. MeCP2 es una proteína con capacidad para unirse a dinucleótidos CpG. Entre las varias funciones biológicas propuesta para MeCP2 se encuentran: 1) Silenciamento transcripcional; 2) activador transcripcional; 3) regulador de splicing; 4) Regulador de la cromatina. Objetivos del estudio: El principal objetivo de esta tesis es evaluar el impacto del incremento o disminución de expresión de MeCP2 , tanto a nivel transcripcional como de desarrollo, al fin de caracterizar las vías moleculares desreguladas en las manifestaciones clínicas relacionadas con MeCP2. En los primeros dos estudios se buscarán nuevos targets de MeCP2 a través de dos diferentes tecnologías, secuenciación del ARN y microarray. En ambos estudios utilizaremos un modelo murino bien establecido (MeCP2-null), obtenido mediante supresión del gen MeCP2, que simula el síndrome de Rett. Las diferencias entre los primeros dos estudios es que mientras en el primero se buscarán solo "long non-coding RNA" relacionados con MeCP2, el segundo será enfocado en todos los ARN codificantes. En el tercer estudio evaluaremos el efecto de la sobreexpresión de MeCP2 en un bien establecido modelo de desarrollo embrionario como es el embrión de pollo. Resultados y conclusiones: Parte 1 * Se han encontrado 701 lncRNAs diferencialmente expresados entre el cerebro del ratón Mecp2-null y el control (salvaje). * MeCP2 está unido a los promotores de los lncRNAs AK081227 y AK087060. * El incremento de expresión de AK081227 en ratones Mecp2-null está asociado con la bajada de expresión de su gen huésped Gabrr2 en cuatro regiones del cerebro. * La sobre regulación de AK087060 se correlaciona con un aumento en la expresión de su gen huésped Arhgef26 en las cuatro regiones cerebrales estudiadas. Parte 2 * Hemos encontrados 1049 y 1154 transcritos diferencialmente expresado en el hipocampo (HIP) y la corteza pre-frontal (PFC), respectivamente, del ratón Mecp2- null. * Los genes "immediate early genes" (IEGs) Fos, JunB, EGR2, NR4A1, Npas4, FosB y Egrl están sobreexpresados en el HIP de Mecp2-null. Además, Fos, JunB, Npas4 y FosB están sobreexpresados también en el PFC. * En tanto la PFC como en el HIP del ratón wild-type, la unión de MeCP2 se reduce en las regiones asociadas con alto contenido de CpG de los genes Fos, JunB, NR4A1, Npas4, FosB y Egr1. Además, los promotores de Fos, JunB y Npas4 son más accesibles a la digestión con nucleasas micrococales (MNase) en el HIP de ratones Mecp2-null. * Cuatro IEGs (Fos, JunB, Egr2, Npas4) muestran un patrón de expresión alterado en neuronas derivadas de animales Mecp2-null y tratadas con forskolina. * La expresión de JunB es incrementada significativamente en el hipocampo de los animales Mecp2-null tratados con ácido kaínico, en comparación con ratones controles tratados. Parte 3 * El transcrito y la proteína de MeCP2 de pollo se expresan en varios estadio del desarrollo embrionario y especialmente en el tubo neural * La sobreexpresión de MeCP2 en el tubo neural de embriones de pollo provoca una disminución general en el número de células proliferantes. Además, el patrón de localización del marcador mitótico H3S1Op es aberrante en tubos neurales que sobreexpresan MeCP2. * Una dosis elevada de MeCP2 provoca una clara disminución de las neuronas diferenciadas localizadas en la zona del mantel. Por otra parte, la sobreexpresión de MeCP2 conduce a una disminución del marcador de polaridad neuroepitelia Ncadherin. * La sobreexpresión de MeCP2 en tubos neurales provoca un aumento de apoptosis.

The Myc transcription factor activates expression of genes that promote cellular functions such as proliferation and cell growth. The deregulated Myc expression, characteristic for the tumor cell, also activates apoptosis, which selects for additional genetic changes deactivating the induced cell death. However, the continuous overexpression of Myc can also be a liability for a tumor, which can be taken advantage of in cancer treatment.  In Paper I, we describe a new way of using the DNA methyltransferase inhibitor Decitabine, in treating Myc overexpressing tumors. We show that Decitabine treatment activates cell death by reactivating silenced tumor suppressors such as Puma, but also by inducing DNA damage. Decitabine treatment of Myc driven lymphomas is also shown to prolong disease free survival in mouse models. Myc driven transformation requires a collaborative deregulation of genes. The family of Pim kinases has been shown to collaborate with Myc in tumorigenesis. In Paper II, we show that the Pim-3 kinase protein is highly expressed in many Myc overexpressing lymphomas from Myc transgenic mice as well as human Burkitt Lymphoma samples. The Pim-3 locus is shown to interact with the Myc protein and be a direct target for Myc activated transcription. Additionally, we demonstrate that the Pim kinase inhibitor, Pimi, targeting the Pim kinase family (Pim-1, Pim-2 and Pim-3), induce a cell death that is mediated by, but not dependent on caspase activity. The Pimi induced cell death was potentiated when combined with RNAi knockdown of the casein kinase II (CK2) protein.  In paper III, we describe the development of a somatic mouse model for lymphomagenesis, utilizing the RCAS-tva technology. We show that primary B cells from these mice are transducible and transformed when infected with a combination of RCAS- HA tagged Myc, KRasV12D and human Bcl-XL virus. In conclusion, we show that the labile milieu created by the deregulated expression of Myc facilitates new approaches in treatment of Myc overexpressing tumors. Also, our new tva mouse model show promise in modeling lymphomagenesis.

The epsilon4 allele of apolipoprotein E is now a well-known risk factor for Alzheimer's disease, however there is still much to be learned of the physiology of apoE in the brain, throughout normal aging and AD. To better understand the neurobiology of apoE, the work included in this thesis has focused on some of the key relationships apoE holds with some proteins known or suggested to have a role in the etiology of Alzheimer's disease. The H2 allele of apolipoprotein C-I is associated with Alzheimer's disease (AD). To examine the possibility of a direct role for apoC-I in AD, we compared apoC-I and apoE protein and mRNA levels in post-mortem specimens of frontal cortex and hippocampus from AD patients with levels in non-demented controls. We were able to confirm apoC-I expression in the CNS and identify astrocytes as the source of apoC-I. In addition, we revealed differences in apoC-I expression based on location in the brain, genotype and disease status that may reflect a role for apoC-I in the pathogenesis of AD. Lipoproteins are only efficient if able to access their target cells. ApoER2 is one of the major receptors for ApoE in the brain, and has been shown to be involved not only in lipoprotein endocytosis, but also in various cellular functions such as signalling and cellular guidance. By performing an entorhinal cortex lesion, a model of synaptic plasticity, in mice which express a decreasing number of copies of the apoER2 gene, we investigated the implication of a deficiency of this particular receptor in response to damage. Our results clearly indicate a role for apoER2 in maintaining efficient synaptic plasticity. We have also used the same synaptic plasticity model to compare the reactivity of various proteins associated with Alzheimer's disease, in wild-type C57Bl/6J and apoE-knockout mice. Along with quantifiying the levels of these proteins (APP, amyloid peptides and apoE receptors LRP and apoER2), our results also show that

Dissertation (PhD)--Stellenbosch University, 2001.
ENGLISH ABSTRACT: Obsessive-compulsive disorder (OCD) is characterized by intrusive thoughts (obsessions) and repetiti ve mental acts or behaviours (compulsions) . For many years, it was considered a rather uncommon condition, caused by unconscious conflict, and somewhat resistant to treatment. In recent decades, however, it has emerged that OCD is a highly prevalent disorder, mediated by particular neuroanatomical circuits (e.g. striatal pathways) and neurochemical systems (e.g. the serotonin system), and responsive to treatment with serotonin reuptake inhibitors (SRIs) . Nevertheless, many questions remain; about the specificity of neuroanatomical findings to OCD, about the role of the multiple serotonin (5-HT) receptor subtypes (e.g. 5-HT10)' and about the appropriate pharmacotherapy for patients resistent to SRI treatment? In a series of studies, 1) the neuroanatomy of OCD was assessed by means of magnetic resonance imaging and neuropsychological testing, 2) the neurochemistry of OCD was assessed by means of functional brain imaging after administration of a 5-HT10 agonist, and 3) the pharmacotherapy of OCD was explored in a series of treatment-refractory OCD and OCD spectrum disorder patients using SRI augmentation with a dopamine blocker. Although no significant difference was found in the volume of the caudate in women with OCD and controls, there was a significant correlation between caudate volume and neuropsychological dysfunction in patients, consistent with evidence of striatal involvement in OCD. Functional imaging demonstrated behavioural heterogeneity, but brain-behaviour correlations were positive, consistent with preclinical evidence of a role for the 5-HTlD receptor in the mediation of OCD. Finally, preliminary treatment findings with dopamine blocker augmentation of a SRI were promising, consistent with preclinical understandings of the interactions between the dopamine and serotonin systems. Although oeD is a complex disorder, a number of future research avenues hold promise for providing a thorough delineation of its pathogenesis.
AFRIKAANSE OPSOMMING: Obsessief-kompulsiewe steuring (OKS) word gekenmerk deur indringende gedagtes (obsessies) en herhalende gedagtes of gedrag (kompulsies). Vir baie jare is dit beskou as 'n redelik seldsame toestand wat veroorsaak word deur onbewustelike konflik, en wat in 'n mate teen behandeling weerstandig is. Meer onlangs het dit egter na vore getree as 'n toestand wat baie dikwels voorkom, wat deur spesifieke neuroanatomiese siklusse (bv. striatale bane) en neurochemiese sisteme (bv. die serotonien-sisteem) teweeg gebring word, en wat op behandeling met serotonien heropname inhibeerders (SHIs) reageer. Nogtans is daar steeds baie vrae; oor die spesifisiteit van neuroanatomiese bevindinge vir OKS, oor die rol van die veelvuldige serotonien (5-HT) reseptor subtipes (bv. 5- HT1D), en oor die toepaslike farmakoterapie vir pasiënte wat weerstandig is vir SHI behandeling. In' n reeks van navorsingstudies, is 1.) die neuroanatomie van OKS deur middel van magnetiese resonans beelding en neurosielkundige toetse ondersoek, 2. ) die neurochemie van OKS deur middel van funksionele breinbeelding na toediening van 'n 5-HT1D agonis bepaal, en 3.) die farmakoterapie van OKS in 'n reeks van behandelingsweerstandige OKS en OKS-spektrum steuring pasiënte - waar gebruik gemaak is van SHI aanvulling met 'n dopamien-blokker - ondersoek. Alhoewel daar geen beduidende verskil in die volume van die caudata in vroue met OKS en kontroles gevind is nie, was daar 'n beduidende korrelasie tussen die caudata volume en neurosielkundige wanfunksionering in pasiënte, in ooreenstemming met striatale betrokkenheid in OKS. Funksionele beelding het positief, in demonstreer, maar ooreenstemming met brein-gedrag pre-kliniese heterogeneïteit korrelasies was in gedrag bewyse vir 'n rol vir die 5-HT1D reseptor in die bemiddeling van OKS. Ten laaste, voorlopige behandelingsbevindinge oor dopamienblokker aanvulling van 'n SHI is belowend, in ooreenstemming met v