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1
Kullmann, Jan A., Sophie Meyer, Fabrizia Pipicelli, et al. "Profilin1-Dependent F-Actin Assembly Controls Division of Apical Radial Glia and Neocortex Development." Cerebral Cortex 30, no. 6 (2019): 3467–82. http://dx.doi.org/10.1093/cercor/bhz321.
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Abstract Neocortex development depends on neural stem cell proliferation, cell differentiation, neurogenesis, and neuronal migration. Cytoskeletal regulation is critical for all these processes, but the underlying mechanisms are only poorly understood. We previously implicated the cytoskeletal regulator profilin1 in cerebellar granule neuron migration. Since we found profilin1 expressed throughout mouse neocortex development, we here tested the hypothesis that profilin1 is crucial for neocortex development. We found no evidence for impaired neuron migration or layering in the neocortex of profilin1 mutant mice. However, proliferative activity at basal positions was doubled in the mutant neocortex during mid-neurogenesis, with a drastic and specific increase in basal Pax6+ cells indicative for elevated numbers of basal radial glia (bRG). This was accompanied by transiently increased neurogenesis and associated with mild invaginations resembling rudimentary neocortex folds. Our data are in line with a model in which profilin1-dependent actin assembly controls division of apical radial glia (aRG) and thereby the fate of their progenies. Via this mechanism, profilin1 restricts cell delamination from the ventricular surface and, hence, bRG production and thereby controls neocortex development in mice. Our data support the radial cone hypothesis” claiming that elevated bRG number causes neocortex folds.
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Penisson, Maxime, Mingyue Jin, Shengming Wang, Shinji Hirotsune, Fiona Francis, and Richard Belvindrah. "Lis1 mutation prevents basal radial glia-like cell production in the mouse." Human Molecular Genetics 31, no. 6 (2021): 942–57. http://dx.doi.org/10.1093/hmg/ddab295.
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Abstract Human cerebral cortical malformations are associated with progenitor proliferation and neuronal migration abnormalities. Progenitor cells include apical radial glia, intermediate progenitors and basal (or outer) radial glia (bRGs or oRGs). bRGs are few in number in lissencephalic species (e.g. the mouse) but abundant in gyrencephalic brains. The LIS1 gene coding for a dynein regulator, is mutated in human lissencephaly, associated also in some cases with microcephaly. LIS1 was shown to be important during cell division and neuronal migration. Here, we generated bRG-like cells in the mouse embryonic brain, investigating the role of Lis1 in their formation. This was achieved by in utero electroporation of a hominoid-specific gene TBC1D3 (coding for a RAB-GAP protein) at mouse embryonic day (E) 14.5. We first confirmed that TBC1D3 expression in wild-type (WT) brain generates numerous Pax6+ bRG-like cells that are basally localized. Second, using the same approach, we assessed the formation of these cells in heterozygote Lis1 mutant brains. Our novel results show that Lis1 depletion in the forebrain from E9.5 prevented subsequent TBC1D3-induced bRG-like cell amplification. Indeed, we observe perturbation of the ventricular zone (VZ) in the mutant. Lis1 depletion altered adhesion proteins and mitotic spindle orientations at the ventricular surface and increased the proportion of abventricular mitoses. Progenitor outcome could not be further altered by TBC1D3. We conclude that disruption of Lis1/LIS1 dosage is likely to be detrimental for appropriate progenitor number and position, contributing to lissencephaly pathogenesis.
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Sawada, Kazuhiko. "Neurogenesis of Subventricular Zone Progenitors in the Premature Cortex of Ferrets Facilitated by Neonatal Valproic Acid Exposure." International Journal of Molecular Sciences 23, no. 9 (2022): 4882. http://dx.doi.org/10.3390/ijms23094882.
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The present study evaluated the neurogenesis of neonatal valproic acid (VPA) exposure on subventricular zone progenitors of the developing cerebral cortex in ferrets. VPA was injected at a dose of 200 µg/g of body weight into ferret infants on postnatal days 6 and 7. Two different thymidine analogues, 5-ethynyl-2′-deoxyuridine (EdU) and 5-bromo-2′-deoxyuridine (BrdU), were injected with a 48 h interval to label proliferating cells before and after VPA exposure. Two hours after BrdU injection, BrdU single- and EdU/BrdU double-labeled cells, but not EdU single-labeled cells, were significantly denser in both the inner and outer subventricular zones of VPA-exposed infants than in control infants. Notably, more than 97% of BrdU single- and EdU/BrdU double-labeled cells were immunopositive for Pax6, a stable marker for basal radial glia (bRG), in both groups. In contrast, the percentage of cells positively immunostained for Cux1, a postmitotic marker for upper-layer cortical neurons, in both EdU single- and BrdU single-labeled cells, was significantly higher in VPA-exposed infants than in control infants. These findings suggest that neonatal VPA exposure facilitates bRG proliferation, including self-renewal, followed by their differentiation into upper layer cortical neurons in the premature cortex of ferrets.
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Meyerink, Brandon L., Neeraj K. Tiwari, and Louis-Jan Pilaz. "Ariadne’s Thread in the Developing Cerebral Cortex: Mechanisms Enabling the Guiding Role of the Radial Glia Basal Process during Neuron Migration." Cells 10, no. 1 (2020): 3. http://dx.doi.org/10.3390/cells10010003.
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Radial neuron migration in the developing cerebral cortex is a complex journey, starting in the germinal zones and ending in the cortical plate. In mice, migratory distances can reach several hundreds of microns, or millimeters in humans. Along the migratory path, radially migrating neurons slither through cellularly dense and complex territories before they reach their final destination in the cortical plate. This task is facilitated by radial glia, the neural stem cells of the developing cortex. Indeed, radial glia have a unique bipolar morphology, enabling them to serve as guides for neuronal migration. The key guiding structure of radial glia is the basal process, which traverses the entire thickness of the developing cortex. Neurons recognize the basal process as their guide and maintain physical interactions with this structure until the end of migration. Thus, the radial glia basal process plays a key role during radial migration. In this review, we highlight the pathways enabling neuron-basal process interactions during migration, as well as the known mechanisms regulating the morphology of the radial glia basal process. Throughout, we describe how dysregulation of these interactions and of basal process morphology can have profound effects on cortical development, and therefore lead to neurodevelopmental diseases.
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Pereida-Jaramillo, Elizabeth, Gabriela B. Gómez-González, Angeles Edith Espino-Saldaña, and Ataúlfo Martínez-Torres. "Calcium Signaling in the Cerebellar Radial Glia and Its Association with Morphological Changes during Zebrafish Development." International Journal of Molecular Sciences 22, no. 24 (2021): 13509. http://dx.doi.org/10.3390/ijms222413509.
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Radial glial cells are a distinct non-neuronal cell type that, during development, span the entire width of the brain walls of the ventricular system. They play a central role in the origin and placement of neurons, since their processes form structural scaffolds that guide and facilitate neuronal migration. Furthermore, glutamatergic signaling in the radial glia of the adult cerebellum (i.e., Bergmann glia), is crucial for precise motor coordination. Radial glial cells exhibit spontaneous calcium activity and functional coupling spread calcium waves. However, the origin of calcium activity in relation to the ontogeny of cerebellar radial glia has not been widely explored, and many questions remain unanswered regarding the role of radial glia in brain development in health and disease. In this study we used a combination of whole mount immunofluorescence and calcium imaging in transgenic (gfap-GCaMP6s) zebrafish to determine how development of calcium activity is related to morphological changes of the cerebellum. We found that the morphological changes in cerebellar radial glia are quite dynamic; the cells are remarkably larger and more elaborate in their soma size, process length and numbers after 7 days post fertilization. Spontaneous calcium events were scarce during the first 3 days of development and calcium waves appeared on day 5, which is associated with the onset of more complex morphologies of radial glia. Blockage of gap junction coupling inhibited the propagation of calcium waves, but not basal local calcium activity. This work establishes crucial clues in radial glia organization, morphology and calcium signaling during development and provides insight into its role in complex behavioral paradigms.
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Moore, Rachel, and Paula Alexandre. "Delta-Notch Signaling: The Long and The Short of a Neuron’s Influence on Progenitor Fates." Journal of Developmental Biology 8, no. 2 (2020): 8. http://dx.doi.org/10.3390/jdb8020008.
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Maintenance of the neural progenitor pool during embryonic development is essential to promote growth of the central nervous system (CNS). The CNS is initially formed by tightly compacted proliferative neuroepithelial cells that later acquire radial glial characteristics and continue to divide at the ventricular (apical) and pial (basal) surface of the neuroepithelium to generate neurons. While neural progenitors such as neuroepithelial cells and apical radial glia form strong connections with their neighbours at the apical and basal surfaces of the neuroepithelium, neurons usually form the mantle layer at the basal surface. This review will discuss the existing evidence that supports a role for neurons, from early stages of differentiation, in promoting progenitor cell fates in the vertebrates CNS, maintaining tissue homeostasis and regulating spatiotemporal patterning of neuronal differentiation through Delta-Notch signalling.
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Li, Zhen, William A. Tyler, Ella Zeldich, et al. "Transcriptional priming as a conserved mechanism of lineage diversification in the developing mouse and human neocortex." Science Advances 6, no. 45 (2020): eabd2068. http://dx.doi.org/10.1126/sciadv.abd2068.
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How the rich variety of neurons in the nervous system arises from neural stem cells is not well understood. Using single-cell RNA-sequencing and in vivo confirmation, we uncover previously unrecognized neural stem and progenitor cell diversity within the fetal mouse and human neocortex, including multiple types of radial glia and intermediate progenitors. We also observed that transcriptional priming underlies the diversification of a subset of ventricular radial glial cells in both species; genetic fate mapping confirms that the primed radial glial cells generate specific types of basal progenitors and neurons. The different precursor lineages therefore diversify streams of cell production in the developing murine and human neocortex. These data show that transcriptional priming is likely a conserved mechanism of mammalian neural precursor lineage specialization.
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Golden, J. A., J. C. Zitz, K. McFadden, and C. L. Cepko. "Cell migration in the developing chick diencephalon." Development 124, no. 18 (1997): 3525–33. http://dx.doi.org/10.1242/dev.124.18.3525.
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We previously reported that retrovirally marked clones in the mature chick diencephalon were widely dispersed in the mediolateral, dorsoventral and rostrocaudal planes. The current study was undertaken to define the migration routes that led to the dispersion. Embryos were infected between stages 10 and 14 with a retroviral stock encoding alkaline phosphatase and a library of molecular tags. Embryos were harvested 2.5-5.5 days later and the brains were fixed and serially sectioned. Sibling relationships were determined following PCR amplification and sequencing of the molecular tag. On embryonic day 4, all clones were organized in radial columns spanning the neuroepithelium, which was composed primarily of a ventricular zone at this age. No tangential migration was seen in the ventricular zone. On embryonic day 5, most clones remained radial with many cells located in the ventricular zone; however, a few clones had cells migrating perpendicular to the radial column, in either a rostrocaudal or dorsoventral direction. The tangential migration began just beyond the basal limit of the ventricular zone. On embryonic days 6 and 7, many clones had cells migrating perpendicular to the radial column, which spanned from the ventricular to the pial surface. The migrating cells appeared to be aligned along axes that were perpendicular to the radial column. Using a combination of DiI tracing, immunohistochemistry and electron microscopy, we have determined that axonal tracts are present and are aligned with the migrating cells, suggesting that they support the non-radial cell migration. These data indicate that migration along pathways independent of radial glia occur outside of the ventricular zone in more than 50% of the clones in the chick diencephalon.
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Zhang, Sanguo, Huanhuan Joyce Wang, Jia Li, Xiao-Ling Hu, and Qin Shen. "Radial Glial Cell-Derived VCAM1 Regulates Cortical Angiogenesis Through Distinct Enrichments in the Proximal and Distal Radial Processes." Cerebral Cortex 30, no. 6 (2020): 3717–30. http://dx.doi.org/10.1093/cercor/bhz337.
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Abstract Angiogenesis in the developing cerebral cortex accompanies cortical neurogenesis. However, the precise mechanisms underlying cortical angiogenesis at the embryonic stage remain largely unknown. Here, we show that radial glia-derived vascular cell adhesion molecule 1 (VCAM1) coordinates cortical vascularization through different enrichments in the proximal and distal radial glial processes. We found that VCAM1 was highly enriched around the blood vessels in the inner ventricular zone (VZ), preventing the ingrowth of blood vessels into the mitotic cell layer along the ventricular surface. Disrupting the enrichment of VCAM1 surrounding the blood vessels by a tetraspanin-blocking peptide or conditional deletion of Vcam1 gene in neural progenitor cells increased angiogenesis in the inner VZ. Conversely, VCAM1 expressed in the basal endfeet of radial glial processes promoted angiogenic sprouting from the perineural vascular plexus (PNVP). In utero, overexpression of VCAM1 increased the vessel density in the cortical plate, while knockdown of Vcam1 accomplished the opposite. In vitro, we observed that VCAM1 bidirectionally affected endothelial cell proliferation in a concentration-dependent manner. Taken together, our findings identify that distinct concentrations of VCAM1 around VZ blood vessels and the PNVP differently organize cortical angiogenesis during late embryogenesis.
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Zaidi, Donia, Kaviya Chinnappa, and Fiona Francis. "Primary Cilia Influence Progenitor Function during Cortical Development." Cells 11, no. 18 (2022): 2895. http://dx.doi.org/10.3390/cells11182895.
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Corticogenesis is an intricate process controlled temporally and spatially by many intrinsic and extrinsic factors. Alterations during this important process can lead to severe cortical malformations. Apical neuronal progenitors are essential cells able to self-amplify and also generate basal progenitors and/or neurons. Apical radial glia (aRG) are neuronal progenitors with a unique morphology. They have a long basal process acting as a support for neuronal migration to the cortical plate and a short apical process directed towards the ventricle from which protrudes a primary cilium. This antenna-like structure allows aRG to sense cues from the embryonic cerebrospinal fluid (eCSF) helping to maintain cell shape and to influence several key functions of aRG such as proliferation and differentiation. Centrosomes, major microtubule organising centres, are crucial for cilia formation. In this review, we focus on how primary cilia influence aRG function during cortical development and pathologies which may arise due to defects in this structure. Reporting and cataloguing a number of ciliary mutant models, we discuss the importance of primary cilia for aRG function and cortical development.
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Wichterle, Hynek, Daniel H. Turnbull, Susana Nery, Gord Fishell, and Arturo Alvarez-Buylla. "In utero fate mapping reveals distinct migratory pathways and fates of neurons born in the mammalian basal forebrain." Development 128, no. 19 (2001): 3759–71. http://dx.doi.org/10.1242/dev.128.19.3759.
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Recent studies suggest that neurons born in the developing basal forebrain migrate long distances perpendicularly to radial glia and that many of these cells reach the developing neocortex. This form of tangential migration, however, has not been demonstrated in vivo, and the sites of origin, pathways of migration and final destinations of these neurons in the postnatal brain are not fully understood. Using ultrasound-guided transplantation in utero, we have mapped the migratory pathways and fates of cells born in the lateral and medial ganglionic eminences (LGE and MGE) in 13.5-day-old mouse embryos. We demonstrate that LGE and MGE cells migrate along different routes to populate distinct regions in the developing brain. We show that LGE cells migrate ventrally and anteriorly, and give rise to the projecting medium spiny neurons in the striatum, nucleus accumbens and olfactory tubercle, and to granule and periglomerular cells in the olfactory bulb. By contrast, we show that the MGE is a major source of neurons migrating dorsally and invading the developing neocortex. MGE cells migrate into the neocortex via the neocortical subventricular zone and differentiate into the transient subpial granule neurons in the marginal zone and into a stable population of GABA-, parvalbumin- or somatostatin-expressing interneurons throughout the cortical plate.
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Moers, Alexandra, Alexander Nürnberg, Sandra Goebbels, Nina Wettschureck та Stefan Offermanns. "Gα12/Gα13 Deficiency Causes Localized Overmigration of Neurons in the Developing Cerebral and Cerebellar Cortices". Molecular and Cellular Biology 28, № 5 (2007): 1480–88. http://dx.doi.org/10.1128/mcb.00651-07.
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ABSTRACT The heterotrimeric G proteins G12 and G13 link G-protein-coupled receptors to the regulation of the actin cytoskeleton and the induction of actomyosin-based cellular contractility. Here we show that conditional ablation of the genes encoding the α-subunits of G12 and G13 in the nervous system results in neuronal ectopia of the cerebral and cerebellar cortices due to overmigration of cortical plate neurons and cerebellar Purkinje cells, respectively. The organization of the radial glia and the basal lamina was not disturbed, and the Cajal-Retzius cell layer had formed normally in mutant mice. Embryonic cortical neurons lacking G12/G13 were unable to retract their neurites in response to lysophosphatidic acid and sphingosine-1-phosphate, indicating that they had lost the ability to respond to repulsive mediators acting via G-protein-coupled receptors. Our data indicate that G12/G13-coupled receptors mediate stop signals and are required for the proper positioning of migrating cortical plate neurons and Purkinje cells during development.
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Loeb, J. A., T. S. Khurana, J. T. Robbins, A. G. Yee, and G. D. Fischbach. "Expression patterns of transmembrane and released forms of neuregulin during spinal cord and neuromuscular synapse development." Development 126, no. 4 (1999): 781–91. http://dx.doi.org/10.1242/dev.126.4.781.
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We mapped the distribution of neuregulin and its transmembrane precursor in developing, embryonic chick and mouse spinal cord. Neuregulin mRNA and protein were expressed in motor and sensory neurons shortly after their birth and levels steadily increased during development. Expression of the neuregulin precursor was highest in motor and sensory neuron cell bodies and axons, while soluble, released neuregulin accumulated along early motor and sensory axons, radial glia, spinal axonal tracts and neuroepithelial cells through associations with heparan sulfate proteoglycans. Neuregulin accumulation in the synaptic basal lamina of neuromuscular junctions occurred significantly later, coincident with a reorganization of muscle extracellular matrix resulting in a relative concentration of heparan sulfate proteoglycans at endplates. These results demonstrate an early axonal presence of neuregulin and its transmembrane precursor at developing synapses and a role for heparan sulfate proteoglycans in regulating the temporal and spatial sites of soluble neuregulin accumulation during development.
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Zhao, Xiang, Jason Q. Garcia, Kai Tong, et al. "Polarized endosome dynamics engage cytoplasmic Par-3 that recruits dynein during asymmetric cell division." Science Advances 7, no. 24 (2021): eabg1244. http://dx.doi.org/10.1126/sciadv.abg1244.
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In the developing embryos, the cortical polarity regulator Par-3 is critical for establishing Notch signaling asymmetry between daughter cells during asymmetric cell division (ACD). How cortically localized Par-3 establishes asymmetric Notch activity in the nucleus is not understood. Here, using in vivo time-lapse imaging of mitotic radial glia progenitors in the developing zebrafish forebrain, we uncover that during horizontal ACD along the anteroposterior embryonic axis, endosomes containing the Notch ligand DeltaD (Dld) move toward the cleavage plane and preferentially segregate into the posterior (subsequently basal) Notchhi daughter. This asymmetric segregation requires the activity of Par-3 and dynein motor complex. Using label retention expansion microscopy, we further detect Par-3 in the cytosol colocalizing the dynein light intermediate chain 1 (Dlic1) onto Dld endosomes. Par-3, Dlic1, and Dld are associated in protein complexes in vivo. Our data reveal an unanticipated mechanism by which cytoplasmic Par-3 directly polarizes Notch signaling components during ACD.
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Pushchina, Evgeniya V., Eva I. Zharikova, and Anatoly A. Varaksin. "Expression of Doublecortin, Glial Fibrillar Acidic Protein, and Vimentin in the Intact Subpallium and after Traumatic Injury to the Pallium in Juvenile Salmon, Oncorhynchus masou." International Journal of Molecular Sciences 23, no. 3 (2022): 1334. http://dx.doi.org/10.3390/ijms23031334.
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Fetalization associated with a delay in development and the preservation of the features of the embryonic structure of the brain dominates the ontogeny of salmonids. The aim of the present study was to comparatively analyze the distribution of the glial-type aNSC markers such as vimentin and glial fibrillar acidic protein (GFAP) and the migratory neuronal precursors such as doublecortin in the telencephalon subpallium of juvenile masu salmon, Oncorhynchus masou, in normal conditions and at 1 week after an injury to the dorsal pallium. Immunohistochemical labeling of vimentin, GFAP, and doublecortin in the pallium of intact juvenile masu salmon revealed single cells with similar morphologies corresponding to a persistent pool of neuronal and/or glial progenitors. The study of the posttraumatic process showed the presence of intensely GFAP-labeled cells of the neuroepithelial type that form reactive neurogenic zones in all areas of the subpallial zone of juvenile masu salmon. A comparative analysis of the distribution of radial glia in the dorsal, ventral, and lateral zones of the subpallium showed a maximum concentration of cells in the dorsal part of subpallium (VD) and a minimum concentration in the lateral part of subpallium VL. An essential feature of posttraumatic immunolabeling in the masu salmon subpallium is the GFAP distribution patterns that are granular intracellular in the apical periventricular zone (PVZ) and fibrillar extracellular in the subventricular (SVZ) and parenchymal zones (PZ). In contrast to those in intact animals, most of the GFAP+ granules and constitutive neurogenic niches in injured fish were localized in the basal part of the PVZ. With the traumatic injury to the subpallium, the number of Vim+ cells in the lateral and ventral regions significantly increased. At 1 week post-injury, the total immunolabeling of vimentin cells in the PVZ was replaced by the granular pattern of Vim immunodistribution spreading from the PVZ to the SVZ and deeper parenchymal layers of the brain in all areas of the subpallium. A significant increase in the number of DC+ cells was observed also in all areas of the subpallium. The number of cells increased both in the PVZ and in the SVZ, as well as in the deeper PZ. Thus, at 1 week after the injury to the dorsal pallium, the number of DC, Vim, and GFAP expressing cells of the neuroepithelial type in the subpallium of juvenile masu salmon increased, and additionally GFAP+ radial glia appeared in VD, which was absent from intact animals.
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Sawada, Kazuhiko, Shiori Kamiya, and Tetsuya Kobayashi. "Neonatal Exposure to Lipopolysaccharide Promotes Neurogenesis of Subventricular Zone Progenitors in the Developing Neocortex of Ferrets." International Journal of Molecular Sciences 24, no. 19 (2023): 14962. http://dx.doi.org/10.3390/ijms241914962.
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Lipopolysaccharide (LPS) is a natural agonist of toll-like receptor 4 that serves a role in innate immunity. The current study evaluated the LPS-mediated regulation of neurogenesis in the subventricular zone (SVZ) progenitors, that is, the basal radial glia and intermediate progenitors (IPs), in ferrets. Ferret pups were subcutaneously injected with LPS (500 μg/g of body weight) on postnatal days (PDs) 6 and 7. Furthermore, 5-ethynyl-2′-deoxyuridine (EdU) and 5-bromo-2′-deoxyuridine (BrdU) were administered on PDs 5 and 7, respectively, to label the post-proliferative and proliferating cells in the inner SVZ (iSVZ) and outer SVZ (oSVZ). A significantly higher density of BrdU single-labeled proliferating cells was observed in the iSVZ of LPS-exposed ferrets than in controls but not in post-proliferative EdU single-labeled and EdU/BrdU double-labeled self-renewing cells. BrdU single-labeled cells exhibited a lower proportion of Tbr2 immunostaining in LPS-exposed ferrets (22.2%) than in controls (42.6%) and a higher proportion of Ctip2 immunostaining in LPS-exposed ferrets (22.2%) than in controls (8.6%). The present findings revealed that LPS modified the neurogenesis of SVZ progenitors. Neonatal LPS exposure facilitates the proliferation of SVZ progenitors, followed by the differentiation of Tbr2-expressing IPs into Ctip2-expressing immature neurons.
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Stier, H., and B. Schlosshauer. "Axonal guidance in the chicken retina." Development 121, no. 5 (1995): 1443–54. http://dx.doi.org/10.1242/dev.121.5.1443.
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During retina development, ganglion cells extend their axons exclusively into the innermost tissue layer, but not into outer retina layers. In order to elucidate guiding mechanisms for axons, tissue strips of embryonic chicken retinae were explanted onto retinal cryosections (cryoculture). Ganglion cell axons originating from the explant grew preferentially on the innermost retina layer of cryosections, whereas outer tissue layers were avoided, very much as in vivo. Stereotropism, interaction with laminin of the basal lamina and axonal fasciculation did not significantly affect oriented axonal outgrowth, so that stereotropism as a guidance mechanism could be excluded. Ganglion cell axons were not directed by physical barriers, e.g. microstructured silicon oxide chips. Similarly, UV induced protein inactivation revealed that laminin present in the inner retina did not provide a guidance cue. Even in the absence of ganglion cell axons in retinal cryosections due to prior optic nerve transection in ovo, the growth preference for the innermost retina layer was maintained in cryocultures. However, oriented elongation of axons along the innermost retina layer was lost when radial glial endfeet were selectively eliminated in retinal cryosections. In addition, glial endfeet provided an excellent growth substratum when pure preparations of endfeet were employed in explant cultures. The preference for glial endfeet positioned at the inner retina surface was accompanied by the avoidance of outer retina layers, most likely because of inhibitory components in this region. This assumption is corroborated by the finding that addition of exogenous growth-promoting laminin to cryosections did not abolish the inhibition. Laminin on glass surfaces provided an excellent substratum. Axonal outgrowth was also seriously hampered on specifically purified cells of the outer retina. Most notable, however, in cryocultures aberrant innervation of outer retina layers could be induced by prior heat or protease treatment of cryosections, which pointed to proteins as potential inhibitory components. In summary the data substantiate the hypothesis that within the retina, ganglion cell axons are guided by a dual mechanism based on a permissive and an inhibitory zone. Radial glia is likely to be instructive in this process.
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Pushchina, Evgeniya V., Maria E. Stukaneva, and Anatoly A. Varaksin. "Hydrogen Sulfide Modulates Adult and Reparative Neurogenesis in the Cerebellum of Juvenile Masu Salmon, Oncorhynchus masou." International Journal of Molecular Sciences 21, no. 24 (2020): 9638. http://dx.doi.org/10.3390/ijms21249638.
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Fish are a convenient model for the study of reparative and post-traumatic processes of central nervous system (CNS) recovery, because the formation of new cells in their CNS continues throughout life. After a traumatic injury to the cerebellum of juvenile masu salmon, Oncorhynchus masou, the cell composition of the neurogenic zones containing neural stem cells (NSCs)/neural progenitor cells (NPCs) in the acute period (two days post-injury) changes. The presence of neuroepithelial (NE) and radial glial (RG) neuronal precursors located in the dorsal, lateral, and basal zones of the cerebellar body was shown by the immunohistochemical (IHC) labeling of glutamine synthetase (GS). Progenitors of both types are sources of neurons in the cerebellum of juvenile O. masou during constitutive growth, thus, playing an important role in CNS homeostasis and neuronal plasticity during ontogenesis. Precursors with the RG phenotype were found in the same regions of the molecular layer as part of heterogeneous constitutive neurogenic niches. The presence of neuroepithelial and radial glia GS+ cells indicates a certain proportion of embryonic and adult progenitors and, obviously, different contributions of these cells to constitutive and reparative neurogenesis in the acute post-traumatic period. Expression of nestin and vimentin was revealed in neuroepithelial cerebellar progenitors of juvenile O. masou. Patterns of granular expression of these markers were found in neurogenic niches and adjacent areas, which probably indicates the neurotrophic and proneurogenic effects of vimentin and nestin in constitutive and post-traumatic neurogenesis and a high level of constructive metabolism. No expression of vimentin and nestin was detected in the cerebellar RG of juvenile O. masou. Thus, the molecular markers of NSCs/NPCs in the cerebellum of juvenile O. masou are as follows: vimentin, nestin, and glutamine synthetase label NE cells in intact animals and in the post-traumatic period, while GS expression is present in the RG of intact animals and decreases in the acute post-traumatic period. A study of distribution of cystathionine β-synthase (CBS) in the cerebellum of intact young O. masou showed the expression of the marker mainly in type 1 cells, corresponding to NSCs/NCPs for other molecular markers. In the post-traumatic period, the number of CBS+ cells sharply increased, which indicates the involvement of H2S in the post-traumatic response. Induction of CBS in type 3 cells indicates the involvement of H2S in the metabolism of extracellular glutamate in the cerebellum, a decrease in the production of reactive oxygen species, and also arrest of the oxidative stress development, a weakening of the toxic effects of glutamate, and a reduction in excitotoxicity. The obtained results allow us to consider H2S as a biologically active substance, the numerous known effects of which can be supplemented by participation in the processes of constitutive neurogenesis and neuronal regeneration.
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Kaluthantrige Don, Flaminia, and Nereo Kalebic. "Forebrain Organoids to Model the Cell Biology of Basal Radial Glia in Neurodevelopmental Disorders and Brain Evolution." Frontiers in Cell and Developmental Biology 10 (June 14, 2022). http://dx.doi.org/10.3389/fcell.2022.917166.
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The acquisition of higher intellectual abilities that distinguish humans from their closest relatives correlates greatly with the expansion of the cerebral cortex. This expansion is a consequence of an increase in neuronal cell production driven by the higher proliferative capacity of neural progenitor cells, in particular basal radial glia (bRG). Furthermore, when the proliferation of neural progenitor cells is impaired and the final neuronal output is altered, severe neurodevelopmental disorders can arise. To effectively study the cell biology of human bRG, genetically accessible human experimental models are needed. With the pioneering success to isolate and culture pluripotent stem cells in vitro, we can now routinely investigate the developing human cerebral cortex in a dish using three-dimensional multicellular structures called organoids. Here, we will review the molecular and cell biological features of bRG that have recently been elucidated using brain organoids. We will further focus on the application of this simple model system to study in a mechanistically actionable way the molecular and cellular events in bRG that can lead to the onset of various neurodevelopmental diseases.
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An, Boyang, Akari Ando, Hiroto Akuta, Fumihiro Morishita, and Takuya Imamura. "Human‐biased TMEM25 expression promotes expansion of neural progenitor cells to alter cortical structure in the developing brain." FEBS Letters, October 17, 2023. http://dx.doi.org/10.1002/1873-3468.14756.
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Cortical expansion has occurred during human brain evolution. By comparing human and mouse RNA‐seq datasets, we found that transmembrane protein 25 (TMEM25) was much more highly expressed in human neural progenitors (NPCs). Overexpression of either human TMEM25 or mouse Tmem25 similarly promoted mouse NPC proliferation in vitro. Mimicking human‐type expression of TMEM25 in mouse ventricular cortical progenitors accelerated proliferation of basal radial glia (bRG) and increased the number of upper‐layer neurons in vivo. By contrast, RNA‐seq analysis and pharmacological assays showed that knockdown of TMEM25 in cultured human NPCs compromised the effects of extracellular signals, leading to cell cycle inhibition via Akt repression. Thus, TMEM25 can receive extracellular signals to expand bRG in human cortical development.
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Heng, Xin, Qiuxia Guo, Alan W. Leung, and James YH Li. "Analogous mechanism regulating formation of neocortical basal radial glia and cerebellar Bergmann glia." eLife 6 (May 10, 2017). http://dx.doi.org/10.7554/elife.23253.
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Neocortical basal radial glia (bRG) and cerebellar Bergmann glia (BG) are basal progenitors derived from ventricular apical radial glia (aRG) that selectively lose their apical processes. bRG and BG have been implicated in the expansion and folding of the cerebrum and cerebellum, respectively. Here, we analyzed the molecular characteristics and development of bRG and BG. Transcriptomic comparison revealed striking similarity of the molecular features of bRG and BG. We found that heightened ERK signaling activity in aRG is tightly linked to the temporal formation and the relative abundance of bRG in human and mouse cortices. Forced activation of an FGF-ERK-ETV axis that is crucial to BG induction specifically induced bRG with canonical human bRG features in mice. Therefore, our data point to a common mechanism of bRG and BG generation, bearing implications to the role for these basal progenitors in the evolution of cortical folding of the cerebrum and cerebellum.
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Xing, Lei, Vasiliki Gkini, Anni I. Nieminen, et al. "Functional synergy of a human-specific and an ape-specific metabolic regulator in human neocortex development." Nature Communications 15, no. 1 (2024). http://dx.doi.org/10.1038/s41467-024-47437-8.
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AbstractMetabolism has recently emerged as a major target of genes implicated in the evolutionary expansion of human neocortex. One such gene is the human-specific gene ARHGAP11B. During human neocortex development, ARHGAP11B increases the abundance of basal radial glia, key progenitors for neocortex expansion, by stimulating glutaminolysis (glutamine-to-glutamate-to-alpha-ketoglutarate) in mitochondria. Here we show that the ape-specific protein GLUD2 (glutamate dehydrogenase 2), which also operates in mitochondria and converts glutamate-to-αKG, enhances ARHGAP11B’s ability to increase basal radial glia abundance. ARHGAP11B + GLUD2 double-transgenic bRG show increased production of aspartate, a metabolite essential for cell proliferation, from glutamate via alpha-ketoglutarate and the TCA cycle. Hence, during human evolution, a human-specific gene exploited the existence of another gene that emerged during ape evolution, to increase, via concerted changes in metabolism, progenitor abundance and neocortex size.
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Pinson, Anneline, Lei Xing, Takashi Namba, et al. "Human TKTL1 implies greater neurogenesis in frontal neocortex of modern humans than Neanderthals." Science 377, no. 6611 (2022). http://dx.doi.org/10.1126/science.abl6422.
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Neanderthal brains were similar in size to those of modern humans. We sought to investigate potential differences in neurogenesis during neocortex development. Modern human transketolase-like 1 (TKTL1) differs from Neanderthal TKTL1 by a lysine-to-arginine amino acid substitution. Using overexpression in developing mouse and ferret neocortex, knockout in fetal human neocortical tissue, and genome-edited cerebral organoids, we found that the modern human variant, hTKTL1, but not the Neanderthal variant, increases the abundance of basal radial glia (bRG) but not that of intermediate progenitors (bIPs). bRG generate more neocortical neurons than bIPs. The hTKTL1 effect requires the pentose phosphate pathway and fatty acid synthesis. Inhibition of these metabolic pathways reduces bRG abundance in fetal human neocortical tissue. Our data suggest that neocortical neurogenesis in modern humans differs from that in Neanderthals.
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Vaid, Samir, Oskari Heikinheimo, and Takashi Namba. "Embryonic mouse medial neocortex as a model system for studying the radial glial scaffold in fetal human neocortex." Journal of Neural Transmission, November 30, 2022. http://dx.doi.org/10.1007/s00702-022-02570-w.
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AbstractNeocortex is the evolutionarily newest region in the brain, and is a structure with diversified size and morphology among mammalian species. Humans have the biggest neocortex compared to the body size, and their neocortex has many foldings, that is, gyri and sulci. Despite the recent methodological advances in in vitro models such as cerebral organoids, mice have been continuously used as a model system for studying human neocortical development because of the accessibility and practicality of in vivo gene manipulation. The commonly studied neocortical region, the lateral neocortex, generally recapitulates the developmental process of the human neocortex, however, there are several important factors missing in the lateral neocortex. First, basal (outer) radial glia (bRG), which are the main cell type providing the radial scaffold to the migrating neurons in the fetal human neocortex, are very few in the mouse lateral neocortex, thus the radial glial scaffold is different from the fetal human neocortex. Second, as a consequence of the difference in the radial glial scaffold, migrating neurons might exhibit different migratory behavior and thus distribution. To overcome those problems, we propose the mouse medial neocortex, where we have earlier revealed an abundance of bRG similar to the fetal human neocortex, as an alternative model system. We found that similar to the fetal human neocortex, the radial glial scaffold, neuronal migration and neuronal distribution are tangentially scattered in the mouse medial neocortex. Taken together, the embryonic mouse medial neocortex could be a suitable and accessible in vivo model system to study human neocortical development and its pathogenesis.
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Viola, Valeria, Kaviya Chinnappa, and Fiona Francis. "Radial glia progenitor polarity in health and disease." Frontiers in Cell and Developmental Biology 12 (October 2, 2024). http://dx.doi.org/10.3389/fcell.2024.1478283.
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Radial glia (RG) are the main progenitor cell type in the developing cortex. These cells are highly polarized, with a long basal process spanning the entire thickness of the cortex and acting as a support for neuronal migration. The RG cell terminates by an endfoot that contacts the pial (basal) surface. A shorter apical process also terminates with an endfoot that faces the ventricle, with a primary cilium protruding in the cerebrospinal fluid. These cell domains have particular subcellular compositions that are critical for the correct functioning of RG. When altered, this can affect proper development of the cortex, ultimately leading to cortical malformations, associated with different pathological outcomes. In this review, we focus on the current knowledge concerning the cell biology of these bipolar stem cells and discuss the role of their polarity in health and disease.
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Nakamura, Yuji, Issei S. Shimada, Reza Maroofian, et al. "Biallelic null variants in PNPLA8 cause microcephaly by reducing the number of basal radial glia." Brain, July 31, 2024. http://dx.doi.org/10.1093/brain/awae185.
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Abstract Patatin-like phospholipase domain-containing lipase 8 (PNPLA8), one of the calcium-independent phospholipase A2 enzymes, is involved in various physiological processes through the maintenance of membrane phospholipids. Biallelic variants in PNPLA8 have been associated with a range of paediatric neurodegenerative disorders. However, the phenotypic spectrum, genotype–phenotype correlations and the underlying mechanisms are poorly understood. Here, we newly identified 14 individuals from 12 unrelated families with biallelic ultra-rare variants in PNPLA8 presenting with a wide phenotypic spectrum of clinical features. Analysis of the clinical features of current and previously reported individuals (25 affected individuals across 20 families) showed that PNPLA8-related neurological diseases manifest as a continuum ranging from variable developmental and/or degenerative epileptic–dyskinetic encephalopathy to childhood-onset neurodegeneration. We found that complete loss of PNPLA8 was associated with the more profound end of the spectrum, with congenital microcephaly. Using cerebral organoids generated from human induced pluripotent stem cells, we found that loss of PNPLA8 led to developmental defects by reducing the number of basal radial glial cells and upper-layer neurons. Spatial transcriptomics revealed that loss of PNPLA8 altered the fate specification of apical radial glial cells, as reflected by the enrichment of gene sets related to the cell cycle, basal radial glial cells and neural differentiation. Neural progenitor cells lacking PNPLA8 showed a reduced amount of lysophosphatidic acid, lysophosphatidylethanolamine and phosphatidic acid. The reduced number of basal radial glial cells in patient-derived cerebral organoids was rescued, in part, by the addition of lysophosphatidic acid. Our data suggest that PNPLA8 is crucial to meet phospholipid synthetic needs and to produce abundant basal radial glial cells in human brain development.
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Yoshida, Ryota, and Tetsuji Mori. "Morphological classification of radial glia–like cells in the postnatal mouse subventricular zone." European Journal of Neuroscience, August 10, 2024. http://dx.doi.org/10.1111/ejn.16503.
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AbstractThe subventricular zone (SVZ) is one of the neurogenic regions of the adult mammalian brain. Neural stem cells (NSCs) in the SVZ have certain key features: they express glial fibrillary acidic protein (GFAP), proliferate slowly, have a radial glia–like (RG‐L) morphology, and are in contact with the cerebrospinal fluid (CSF). NSCs have been isolated by FACS to analyse them, but their morphology has not been systematically examined. To address this knowledge gap, we sparsely labelled RG‐L cells in the SVZ of neonatal mice by introducing via electroporation a plasmid expressing fluorescent protein under the control of the GFAP promoter. We then classified RG‐L cells into three types (RG‐L1, 2, and 3) based on their morphologies. RG‐L1 cells had a basal process with some branches and numerous fine processes. RG‐L2 cells had a basal process, but fewer branches and fine processes than RG‐L1 cells. RG‐L3 cells had one basal process that was almost free of branches and fine processes. Importantly, regardless of the cell type, about half of their somata resided on the basal side of the SVZ. Based on changes in their proportions during postnatal development and their expression of GFAP and cell proliferation markers at the adult stage, we speculated that NSCs change their morphologies during development/maturation and not all NSCs must always be in the apical SVZ or in contact with the CSF. Our results indicate that in addition to expression of markers for NSCs, the morphology is a critical feature to identify NSCs.
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Ju, Xiang-Chun, Qiong-Qiong Hou, Ai-Li Sheng, et al. "The hominoid-specific gene TBC1D3 promotes generation of basal neural progenitors and induces cortical folding in mice." eLife 5 (August 9, 2016). http://dx.doi.org/10.7554/elife.18197.
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Cortical expansion and folding are often linked to the evolution of higher intelligence, but molecular and cellular mechanisms underlying cortical folding remain poorly understood. The hominoid-specific gene TBC1D3 undergoes segmental duplications during hominoid evolution, but its role in brain development has not been explored. Here, we found that expression of TBC1D3 in ventricular cortical progenitors of mice via in utero electroporation caused delamination of ventricular radial glia cells (vRGs) and promoted generation of self-renewing basal progenitors with typical morphology of outer radial glia (oRG), which are most abundant in primates. Furthermore, down-regulation of TBC1D3 in cultured human brain slices decreased generation of oRGs. Interestingly, localized oRG proliferation resulting from either in utero electroporation or transgenic expression of TBC1D3, was often found to underlie cortical regions exhibiting folding. Thus, we have identified a hominoid gene that is required for oRG generation in regulating the cortical expansion and folding.
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Kawaguchi, Ayano. "Neuronal Delamination and Outer Radial Glia Generation in Neocortical Development." Frontiers in Cell and Developmental Biology 8 (February 5, 2021). http://dx.doi.org/10.3389/fcell.2020.623573.
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During neocortical development, many neuronally differentiating cells (neurons and intermediate progenitor cells) are generated at the apical/ventricular surface by the division of neural progenitor cells (apical radial glial cells, aRGs). Neurogenic cell delamination, in which these neuronally differentiating cells retract their apical processes and depart from the apical surface, is the first step of their migration. Since the microenvironment established by the apical endfeet is crucial for maintaining neuroepithelial (NE)/aRGs, proper timing of the detachment of the apical endfeet is critical for the quantitative control of neurogenesis in cerebral development. During delamination, the microtubule–actin–AJ (adherens junction) configuration at the apical endfeet shows dynamic changes, concurrent with the constriction of the AJ ring at the apical endfeet and downregulation of cadherin expression. This process is mediated by transcriptional suppression of AJ-related molecules and multiple cascades to regulate cell adhesion and cytoskeletal architecture in a posttranscriptional manner. Recent advances have added molecules to the latter category: the interphase centrosome protein AKNA affects microtubule dynamics to destabilize the microtubule–actin–AJ complex, and the microtubule-associated protein Lzts1 inhibits microtubule assembly and activates actomyosin systems at the apical endfeet of differentiating cells. Moreover, Lzts1 induces the oblique division of aRGs, and loss of Lzts1 reduces the generation of outer radial glia (oRGs, also called basal radial glia, bRGs), another type of neural progenitor cell in the subventricular zone. These findings suggest that neurogenic cell delamination, and in some cases oRG generation, could be caused by a spectrum of interlinked mechanisms.
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Kálmán, Mihály, Erzsébet Oszwald та István Adorján. "Appearance of β-dystroglycan precedes the formation of glio-vascular end-feet in developing rat brain". European Journal of Histochemistry, 18 травня 2018. http://dx.doi.org/10.4081/ejh.2018.2908.
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Dystroglycan has an important role in binding of perivascular glial end-feet tothe basal lamina. Its β-subunit is localized in the glial end-feet. The investigation period lasted from E(embryonic day)12 to E20. Laminin and β-dystroglycan were detected by immunohistochemistry, the glial localization of the latter one was supported by electron microscopy. The immatureglial structures were visualized by the immunostaining of nestin. The β-dystroglycan immunoreactivity appeared at E16 following the laminin of basal lamina but preceding the perivascular processes of radial glia (E18) and astrocyte-like cells (E20). It occurred in cell bodies which attached to the vessels directly but not with vascular processes and end-feet. The presence of β-dystroglycan in such immature cells may promote their differentiation to perivascular astrocytes and influence the formation of the glio-vascular processes.
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Del-Valle-Anton, Lucia, Salma Amin, Daniela Cimino, et al. "Multiple parallel cell lineages in the developing mammalian cerebral cortex." Science Advances 10, no. 13 (2024). http://dx.doi.org/10.1126/sciadv.adn9998.
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Cortical neurogenesis follows a simple lineage: apical radial glia cells (RGCs) generate basal progenitors, and these produce neurons. How this occurs in species with expanded germinal zones and a folded cortex, such as human, remains unclear. We used single-cell RNA sequencing from individual cortical germinal zones in ferret and barcoded lineage tracking to determine the molecular diversity of progenitor cells and their lineages. We identified multiple RGC classes that initiate parallel lineages, converging onto a common class of newborn neuron. Parallel RGC classes and transcriptomic trajectories were repeated across germinal zones and conserved in ferret and human, but not in mouse. Neurons followed parallel differentiation trajectories in the gyrus and sulcus, with different expressions of human cortical malformation genes. Progenitor cell lineage multiplicity is conserved in the folded mammalian cerebral cortex.
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Eşiyok, Nesil, and Michael Heide. "The SVZ stem cell niche–components, functions, and in vitro modelling." Frontiers in Cell and Developmental Biology 11 (December 22, 2023). http://dx.doi.org/10.3389/fcell.2023.1332901.
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Neocortical development depends on the intrinsic ability of neural stem and progenitor cells to proliferate and differentiate to generate the different kinds of neurons in the adult brain. These progenitor cells can be distinguished into apical progenitors, which occupy a stem cell niche in the ventricular zone and basal progenitors, which occupy a stem cell niche in the subventricular zone (SVZ). During development, the stem cell niche provided in the subventricular zone enables the increased proliferation and self-renewal of basal progenitors, which likely underlie the expansion of the human neocortex. However, the components forming the SVZ stem cell niche in the developing neocortex have not yet been fully understood. In this review, we will discuss potential components of the SVZ stem cell niche, i.e., extracellular matrix composition and brain vasculature, and their possible key role in establishing and maintaining this niche during fetal neocortical development. We will also emphasize the potential role of basal progenitor morphology in maintaining their proliferative capacity within the stem cell niche of the SVZ. Finally, we will focus on the use of brain organoids to i) understand the unique features of basal progenitors, notably basal radial glia; ii) study components of the SVZ stem cell niche; and iii) provide future directions on how to improve brain organoids, notably the organoid SVZ, and make them more reliable models of human neocortical development and evolution studies.
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Stefanova, Eva E., Julian V. T. Dychiao, Mavis C. Chinn, Matin Borhani, and Angela L. Scott. "P2X7 regulates ependymo-radial glial cell proliferation in adult Danio rerio following spinal cord injury." Biology Open, March 25, 2024. http://dx.doi.org/10.1242/bio.060270.
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In contrast to mammals, zebrafish undergo successful neural regeneration following spinal cord injury. Spinal cord ependymo-radial glia (ERG) undergo injury-induced proliferation and neuronal differentiation to replace damaged cells and restore motor function. However, the molecular cues driving these processes remain elusive. Here, we demonstrate that the evolutionarily conserved P2X7 receptors are widely distributed on neurons and ERG within the zebrafish spinal cord. At the protein level, the P2X7 receptor expressed in zebrafish is a truncated splice variant of the full-length variant found in mammals. The protein expression of this 50 kDa isoform was significantly downregulated at 7 days post injury (dpi) but returned to basal levels at 14 dpi when compared to naïve controls. Pharmacological activation of P2X7 following SCI resulted in a greater number of proliferating cells around the central canal by 7 dpi but did not affect neuronal differentiation at 14 dpi. Our findings suggest that unlike in mammals, P2X7 signaling may not play a maladaptive role following SCI in adult zebrafish and may also work to curb the proliferative response of ERG following injury.
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Vierl, Franziska, Manpreet Kaur, and Magdalena Götz. "Non-codon Optimized PiggyBac Transposase Induces Developmental Brain Aberrations: A Call for in vivo Analysis." Frontiers in Cell and Developmental Biology 9 (August 3, 2021). http://dx.doi.org/10.3389/fcell.2021.698002.
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In this perspective article, we briefly review tools for stable gain-of-function expression to explore key fate determinants in embryonic brain development. As the piggyBac transposon system has the highest insert size, a seamless integration of the transposed sequence into the host genome, and can be delivered by transfection avoiding viral vectors causing an immune response, we explored its use in the murine developing forebrain. The original piggyBac transposase PBase or the mouse codon-optimized version mPB and the construct to insert, contained in the piggyBac transposon, were introduced by in utero electroporation at embryonic day 13 into radial glia, the neural stem cells, in the developing dorsal telencephalon, and analyzed 3 or 5 days later. When using PBase, we observed an increase in basal progenitor cells, often accompanied by folding aberrations. These effects were considerably ameliorated when using the piggyBac plasmid together with mPB. While size and strength of the electroporated region was not correlated to the aberrations, integration was essential and the positive correlation to the insert size implicates the frequency of transposition as a possible mechanism. We discuss this in light of the increase in transposing endogenous viral vectors during mammalian phylogeny and their role in neurogenesis and radial glial cells. Most importantly, we aim to alert the users of this system to the phenotypes caused by non-codon optimized PBase application in vivo.
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Ohtsuka, Toshiyuki, and Ryoichiro Kageyama. "Hes1 overexpression leads to expansion of embryonic neural stem cell pool and stem cell reservoir in the postnatal brain." Development 148, no. 4 (2021). http://dx.doi.org/10.1242/dev.189191.
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ABSTRACT Neural stem cells (NSCs) gradually alter their characteristics during mammalian neocortical development, resulting in the production of various neurons and glial cells, and remain in the postnatal brain as a source of adult neurogenesis. Notch-Hes signaling is a key regulator of stem cell properties in the developing and postnatal brain, and Hes1 is a major effector that strongly inhibits neuronal differentiation and maintains NSCs. To manipulate Hes1 expression levels in NSCs, we generated transgenic (Tg) mice using the Tet-On system. In Hes1-overexpressing Tg mice, NSCs were maintained in both embryonic and postnatal brains, and generation of later-born neurons was prolonged until later stages in the Tg neocortex. Hes1 overexpression inhibited the production of Tbr2+ intermediate progenitor cells but instead promoted the generation of basal radial glia-like cells in the subventricular zone (SVZ) at late embryonic stages. Furthermore, Hes1-overexpressing Tg mice exhibited the expansion of NSCs and enhanced neurogenesis in the SVZ of adult brain. These results indicate that Hes1 overexpression expanded the embryonic NSC pool and led to the expansion of the NSC reservoir in the postnatal and adult brain.
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Barahona, M. J., F. Langlet, G. Labouèbe, et al. "GLUT2 expression by glial fibrillary acidic protein-positive tanycytes is required for promoting feeding-response to fasting." Scientific Reports 12, no. 1 (2022). http://dx.doi.org/10.1038/s41598-022-22489-2.
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AbstractFeeding behavior is a complex process that depends on the ability of the brain to integrate hormonal and nutritional signals, such as glucose. One glucosensing mechanism relies on the glucose transporter 2 (GLUT2) in the hypothalamus, especially in radial glia-like cells called tanycytes. Here, we analyzed whether a GLUT2-dependent glucosensing mechanism is required for the normal regulation of feeding behavior in GFAP-positive tanycytes. Genetic inactivation of Glut2 in GFAP-expressing tanycytes was performed using Cre/Lox technology. The efficiency of GFAP-tanycyte targeting was analyzed in the anteroposterior and dorsoventral axes by evaluating GFP fluorescence. Feeding behavior, hormonal levels, neuronal activity using c-Fos, and neuropeptide expression were also analyzed in the fasting-to-refeeding transition. In basal conditions, Glut2-inactivated mice had normal food intake and meal patterns. Implementation of a preceeding fasting period led to decreased total food intake and a delay in meal initiation during refeeding. Additionally, Glut2 inactivation increased the number of c-Fos-positive cells in the ventromedial nucleus in response to fasting and a deregulation of Pomc expression in the fasting-to-refeeding transition. Thus, a GLUT2-dependent glucose-sensing mechanism in GFAP-tanycytes is required to control food consumption and promote meal initiation after a fasting period.
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Temereva, Elena, Nadezhda Rimskaya-Korsakova, and Vyacheslav Dyachuk. "Detailed morphology of tentacular apparatus and central nervous system in Owenia borealis (Annelida, Oweniidae)." Zoological Letters 7, no. 1 (2021). http://dx.doi.org/10.1186/s40851-021-00182-y.
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AbstractThe Oweniidae are marine annelids with many unusual features of organ system, development, morphology, and ultrastructure. Together with magelonids, oweniids have been placed within the Palaeoannelida, a sister group to all remaining annelids. The study of this group may increase our understanding of the early evolution of annelids (including their radiation and diversification). In the current research, the morphology and ulta-anatomy of the head region of Owenia borealis is studied by scanning electron microscopy (SEM), 3D reconstructions, transmission electron microscopy (TEM), and whole-mount immunostaining with confocal laser scanning microscopy. According to SEM, the tentacle apparatus consists of 8–14 branched arms, which are covered by monociliary cells that form a ciliary groove extending along the oral side of the arm base. Each tentacle contains a coelomic cavity with a network of blood capillaries. Monociliary myoepithelial cells of the tentacle coelomic cavity form both the longitudinal and the transverse muscles. The structure of this myoepithelium is intermediate between a simple and pseudo-stratified myoepithelium. Overall, tentacles lack prominent zonality, i.e., co-localization of ciliary zones, neurite bundles, and muscles. This organization, which indicates a non-specialized tentacle crown in O. borealis and other oweniids with tentacles, may be ancestral for annelids. TEM, light, and confocal laser scanning microscopy revealed that the head region contains the anterior nerve center comprising of outer and inner (=circumoral) nerve rings. Both nerve rings are organized as concentrated nerve plexus, which contains perikarya and neurites extending between basal projections of epithelial cells (radial glia). The outer nerve ring gives rise to several thick neurite bundles, which branch and extend along aboral side of each tentacle. Accordingly to their immunoreactivity, both rings of the anterior nerve center could be homologized with the dorsal roots of circumesophageal connectives of the typical annelids. Accordingly to its ultrastructure, the outer nerve ring of O. borealis and so-called brain of other oweniids can not be regarded as a typical brain, i.e. the most anterior ganglion, because it lacks ganglionic structure.