Tesis sobre el tema "Glycogen storage disease type III"

La glycogénose de type III (GSDIII) est une maladie génétique récessive due à des mutations affectant l’activité de l'enzyme de débranchement du glycogène (GDE). Les symptômes sont une hépatomégalie et une hypoglycémie chez l’enfant puis une faiblesse musculaire dégénérative chez l’adulte. Aucun traitement curatif n'existe pour GSDIII. Nous avons dans un premier temps développé un modèle de souris GSDIII viable possédant phénotype proche de la maladie de l’homme. La thérapie génique permet le traitement des maladies métaboliques et neuromusculaires. En thérapie génique in vivo, les vecteurs dérivés du virus adéno-associé (AAV) ont démontré leur efficacité chez l’homme. Une limitation dans le développement d'une thérapie génique pour la GSDIII est la taille du transgène qui dépasse la taille d’encapsidation de l'AAV. Nous avons exploré une approche alternative utilisant la voie lysosomale de la dégradation du glycogène par l’enzyme GAA. Les résultats chez les souris GSDIII montrent que l’augmentation de la quantité de GAA dans les muscles ne permet pas de traiter le phénotype de la GSDIII alors qu’au contraire elle induit une normalisation de la quantité du glycogène hépatique. La seconde étape fut de faire exprimer à nouveau la GDE par les cellules. Nous avons développé deux vecteurs pouvant utiliser les mécanismes de la recombinaison homologue. Cette stratégie a permis la correction du phénotype GSDIII dans le modèle murin de la maladie. Les résultats montrent qu’il est possible de corriger la faiblesse musculaire ainsi que l’accumulation de glycogène conduisant à la vacuolisation du tissu. L’efficacité de cette stratégie ne reste néanmoins que partielle dans le foie
Glycogen storage disease type III (GSDIII) is a recessive genetic disorder caused by mutations affecting the activity of the glycogen debranching enzyme (GDE). Symptoms are hepatomegaly and hypoglycemia during childhood and degenerative muscle weakness during adulthood. At present, no curative treatment exists for GSDIII. First, we developed and characterized a mouse model that faithfully recapitulates the human disease. Gene therapy allows the treatment of previously untreatable metabolic and neuromuscular diseases. Adeno-associated virus (AAV) vectors are vectors of choice for in vivo gene therapy, with an excellent safety and efficacy profile demonstrated in human. A major limitation for GSDIII is the size of the transgene that exceeds the genome packaging capacity of AAV vectors. We explored an alternative approach using the lysosomal pathway and the acid alpha-glucosidase (GAA) able to degrade the glycogen, overloading the lysosomes with this protein. In muscles, the increase of GAA activity is not able to treat the phenotype of GSDIII whereas the overexpression of GAA in the liver induces a normalization of the concentration of glycogen. The second step of this thesis was to have GDE de novo expressed in cells. We developed strategy based on the injection of two vectors that can use the mechanisms of homologous recombination. This allowed the correction of the GSDIII phenotype in a murine model of the disease. The results show that it is possible to correct the muscle phenotype of GSDIII. Nevertheless, the effectiveness of this strategy remains only partial in the liver, again highlighting a different glycogen degradation pathway in both tissues

La glycogénose de type III (GSDIII) est une maladie génétique rare due à un déficit en enzyme débranchante du glycogène (GDE), provoquant une accumulation de glycogène dans le foie, le cœur et les muscles squelettiques. Alors que les atteintes hépatiques dominent durant l'enfance, les atteintes musculaires progressent et deviennent prédominantes à l'âge adulte. L'absence de modèles humains freine la compréhension de cette pathologie et la mise au point de traitements.Dans ce contexte, mon premier objectif était de créer des modèles pathologiques humains in vitro à partir de cellules souches pluripotentes induites (hiPSC). J'ai généré cinq lignées hiPSC pathologiques : quatre lignées dérivées de patients par reprogrammation et une lignée génétiquement modifiée par CRISPR/Cas9. Ces cellules ont ensuite été différenciées en myocytes et en hépatocytes, les deux types cellulaires pertinents pour l'étude de la GSDIII. J'ai confirmé que ces cellules expriment respectivement les marqueurs spécifiques des muscles et du foie, et récapitulent, en condition de privation de glucose, le phénotype d'accumulation de glycogène en comparaison à des cellules saines.Le deuxième objectif visait à mieux comprendre les mécanismes physiopathologiques de la GSDIII et à identifier de nouveaux biomarqueurs de la pathologie. Je me suis d'abord focalisée sur le muscle, pour lequel j'ai identifié, par séquençage ARN des myocytes dérivés d'hiPSC, des gènes différentiellement exprimés entre cellules saines et pathologiques. Une analyse comparative avec les données d'un séquençage ARN réalisés sur des biopsies de triceps de souris saines et GSDIII a révélé la surexpression d'un gène commun codant pour la Galectine-3, un marqueur de vésicules endommagées. Sa surexpression a été validée dans les myocytes mutés dérivés d'hiPSC, ainsi que dans les triceps de souris GSDIII et dans des biopsies de patients. En parallèle, une approche similaire sur les hépatocytes dérivés d'hiPSC a permis d'identifier de potentiels biomarqueurs du foie, ouvrant la voie à une meilleure compréhension des mécanismes physiopathologiques hépatiques. Le dernier objectif était d'utiliser ces modèles pathologiques humains in vitro pour tester de nouvelles thérapies. J'ai démontré que le traitement de myocytes mutés par des vecteurs AAV exprimant la GDE humaine complète ou tronquée, préalablement validés dans des modèles in vivo de souris et de rats GSDIII, diminuait l'accumulation de glycogène à des niveaux comparables à ceux de cellules saines. Ces expériences ont confirmé l'intérêt du développement de ces nouveaux modèles in vitro. L'ensemble de ces travaux ont permis l'identification de nouveaux biomarqueurs de la GSDIII, permettant d'améliorer la compréhension des mécanismes moléculaires dans le muscle et le foie. La création de ces nouveaux modèles in vitro ouvre également de nouvelles perspectives thérapeutiques pour la GSDIII, notamment en facilitant le criblage de médicaments
Glycogen storage disease type III (GSDIII) is a rare genetic disorder caused by glycogen debranching enzyme (GDE) deficiency, leading to an accumulation of glycogen accumulation in the liver, heart and skeletal muscles. While liver damages predominate in childhood, muscle impairments progress and become predominant in adulthood. The lack of human models hinders our understanding of the disease and the development of treatments.In this context, my first objective was to create in vitro human pathological models from induced pluripotent stem cells (hiPSCs). I generated five pathological hiPSC lines: four lines derived from patients by reprogramming and one line genetically modified by CRISPR/Cas9. These cells were then differentiated into myocytes and hepatocytes, the two relevant cell types for the study of GSDIII. I confirmed that these cells express muscle and liver specific markers respectively, and recapitulate the glycogen accumulation phenotype under glucose starvation conditions compared to healthy cells.The second objective was to better understand the pathophysiological mechanisms of GSDIII and to identify new biomarkers of the disease. I first focused on muscle, for which I identified genes differentially expressed between healthy and pathological cells by RNA sequencing of hiPSC-derived myocytes. Comparative analysis with RNA sequencing data from triceps biopsies of healthy and GSDIII mice revealed overexpression of a common gene encoding galectin-3, a marker of damaged vesicles. This overexpression was validated in mutated myocytes derived from hiPSCs, as well as in the triceps of GSDIII mice and in patient biopsies. In parallel, a similar approach on hiPSC-derived hepatocytes identified potential liver biomarkers, paving the way for a better understanding of the mechanisms of liver damage.The final objective was to use these in vitro human pathological models to test new therapies. I demonstrated that treatment of mutated myocytes with AAV vectors expressing complete or truncated human GDE, previously validated on in vivo GSDIII mouse and rat models, reduced glycogen accumulation to levels comparable to those of healthy cells. These experiments confirmed the value of developing these new in vitro models.Taken together, this work has led to the identification of new biomarkers for GSDIII, providing a better understanding of the molecular mechanisms in muscle and liver. The creation of these new in vitro models also opens up new therapeutic prospects for GSDIII, particularly by facilitating drug screening

The nutritional management of glycogen storage disease has often been called “the intensive regimen”. The intensive regimen may not be without consequence. This thesis aims to characterise the intensive regimen and implement changes. Chapter 1 discusses concepts of glucose homeostasis in humans and introduces the glycogen storage diseases as a group of disorders. The metabolic physiology of those glycogen storage disorders associated with hypoglycaemia are reviewed and traditional methods used to ameliorate these metabolic disturbances are discussed. Methods used in the study include cornstarch loads, breath enrichment of 13CO2, hydrogen breath tests and dietary assessment as well as participant characteristics are discussed in chapter 2. Chapter 3 examines nutritional management as a cross-sectional dietary survey of children and adults with GSD, comparing the patient group to expert-panel recommendations as well as age and sex matched controls. Chapter 4 looks at the short-term effect a new carbohydrate therapy has on biochemical indices of metabolic control focusing on glucose, lactate and insulin profiles. These studies are double-blind cross-over studies, comparing the novel starch to uncooked cornstarch. Similarly Chapter 5 studies further short-term metabolic effects of the novel starch compared to cornstarch by examining hydrogen breath test data and enrichment of 13C02 in breath in an attempt to gauge the mechanism of action of the novel carbohydrate therapy. Chapter 6 examines the implementation of the new dietary starch into subjects' long-term dietary regimen in the form of a randomised cross-over trial. The primary endpoints are quantity of treatment starch use but safety, efficacy and patient acceptance of therapy are also considered. Chapter 7 brings together these various studies drawing conclusions and suggestions for further study. This chapter highlights the difficulties in performing investigations in rare disorders, when subjects are vulnerable to metabolic decompensation and recommends further study in healthy volunteers.

Glycogen storage diseases (GSD) are inherited metabolic disorders that affect glycogen use and storage. People with GSD Ia lack the enzyme glucose-6-phosphatase (G6Pase). As a result, these people are unable to convert liver glycogen to free glucose and develop severe hypoglycemia. Patients with GSD also develop growth retardation, hepatomegaly, renomegaly, hypertriglyceridemia, hypercholesterolemia, and hyperlactacidemia. No cure for GSD Ia currently exists. Patients are treated symptomatically with repeated naso-gastric feedings and glucose infusions to maintain normal blood glucose concentrations. Despite treatment, the underlying enzymatic defect remains. Gene therapy holds the promise of correcting this metabolic defect, thus providing a true cure for GSD Ia. Gene therapy uses modified virus particles to deliver a replacement functional G6Pase gene to the patientâs liver. Our group is using two viral vectors, adeno-associated virus (AAV) and helper-dependent adenovirus (HDAd), for gene therapy in dogs with an inheritable form of GSD Ia. We have treated three GSD Ia dogs with the AAV vector and two GSD Ia dogs with the HDAd vector. Vector-treated dogs were able to maintain normal blood glucose concentrations and unlike their untreated counterparts, survived for several years. These promising results provide hope that gene therapy may emerge as an effective treatment for people with GSD Ia.

Glycogen storage disease type II (GSDII) is an autosomal recessive lysosomal storage disorder caused by acid alpha-1,4-glucosidase (GAA) deficiency. This study aimed to provide an in-depth description of a late-onset GSDII (LO-GSDII) cohort (n=36) and assess potential genotype-phenotype correlation. We performed a clinical record-based study, some patients (n= 19) were also followed prospectively. Phenotypes were highly variable. We focused our clinical assessment onrespiratory failure, as it is the most frequent cause of death in LO-GSDII. In addition to standard spirometric measures, in a subgroup of patients (n = 10) we utilized a new tool, optoelectronic plethysmography (OEP), to investigate the pathophysiology of respiratory muscle impairment.The GAA gene was sequenced in every patient, and pathogenic mutations were identified inall of them. Almost all (35/36) patients carried the same mutation on one allele, IVS1-32-13T>G, which was in compound heterozygosity with a variety of other GAA mutations. To investigate genotype-phenotype correlation, we divided the patient cohort in two groups, according to the severity of the mutation on the second allele. The respiratory function study focused on diaphragmatic weakness. According to the change in forced vital capacity in supine position (ΔFVC), we defined patients with ΔFVC>25% ashaving diaphragmatic weakness (DW) and those with ΔFVC<25% as without diaphragmatic weakness (noDW). We measured pulmonary function and chest wall volumes using OEP inboth groups. We found a good correlation between the supine abdominal contribution to tidal volume (%VAB) and ΔFVC. Patients showed reduced chest wall and abdominal inspiratory capacity and low abdominal expiratory reserve volume. In terms of genotype-phenotype correlation, we counted more subjects in the group with severe second mutations (n=21) who had severe motor disability and respiratory dysfunction. However, this finding remains preliminary because differences were not significant, likely because of small sample size. Finally, in two smaller substudies, we investigated the occurrence of urinary and fecal incontinence in LO-GSDII, and reported a possibly non-fortuitous association of LO-GSDII and hydromyelia in two individuals. Overall, this work 1) provided new insight into genotype-phenotype correlation in GSDII, suggesting that it is of complex nature; 2) refined the analysis of respiratory muscle impairment and showed the utility of OEP for respiratory assessment in this neuromuscular disorder, and possibly in others as well; 3) indicated some so far little studied phenotypic features of LO-GSD-II that deserve further investigation.
Doctorat en Sciences médicales (Médecine)
info:eu-repo/semantics/nonPublished

The objective of this study was to examine at molecular, biochemical and muscle pathology level two groups of patients affected with Danon disease and GSDII, in order to get new insights that might help in tracing genotype-phenotype correlations and to delineate their pathological mechanisms. Glycogen storage disease type II (GSDII) is an autosomal recessive disorder (OMIM # 232300) caused by the deficiency of the lysosomal enzyme acid ?-glucosidase or acid maltase (EC 3.2.1.20/3), which catalyses the hydrolysis of ?-1,4 and ?-1,6 links of glycogen. The enzyme deficiency leads to lysosomal accumulation of glycogen that results in different clinical phenotypes, ranging from the : the severe infantile-onset form to the childhood, juvenile or adult-onset forms (late-onset forms). We investigated 23 patients with infantile-onset or late-onset glycogen storage disease type II by enzyme activity, protein expression by immunoblotting, GAA gene mutations, and muscle pathology including immunolabeling for Golgi and sarcolemmal proteins. The enzyme activity resulted absent or minimal in infantile-onset cases and variably reduced in late-onset patients. Genotype-phenotype correlation (seven novel mutations were found) showed that most late-onset patients had the heterozygous c.–32-13T>G leaky splicing mutation (one patient was homozygous), but the course of the disease was often difficult to predict on the basis of the mutations alone. One important and novel result from our study came from the Western blot analysis of the different maturative forms of acid ? –glucosidase protein in the muscle from patients with GSDII. We have demonstrated that the muscle from patients with GSDII has a predominant expression of inactive forms of acid ?-glucosidase protein and severely reduced or absent levels of the mature forms. Furthermore, the residual amount of the mature forms of the protein on blotting correlated with the level of enzyme activity in muscle. We first report a different molecular weight of the mature and the intermediate forms of the protein between patients and controls that we attribute to an excessive sialylation of mutant proteins. This is likely caused by a delayed transport and longer transit of the inactive proteins in the Golgi where the sialyltransferases are localized. Supporting this hypothesis, we observed that, in both infantile and late-onset patients, there is an enhanced proliferation of the Golgi apparatus. On the other hand, we did not find any increased expression of LAMP-1 in patients with GSDII, possibly due to the fact that only a minor proportion of mutant enzyme protein is able to reach the lysosomes. Another interesting data rises from the morphologic analysis of the different cellular organelles. Interestingly, we observed a differential degree of dysfunction of endocytic and autophagic pathways in patients with infantile and late-onset GSDII. In late-onset acid maltase deficient muscle, vacuolar membranes expressed sarcolemmal proteins, such as caveolin-3 and dystrophin (previously classified as type 2 vacuoles) and not in the infantile form of the disease (type 4 vacuoles, lakes of glycogen). These features are possibly due to reduced membrane proliferation and vesicular movement in the overcrowded muscle fibers of Pompe disease, and to the membrane remodelling occurring only in patients with late-onset GSDII, which would be a protective mechanism to prevent membrane rupture during fiber contraction. This observation is important because the pathogenesis of the autophagosomes has not yet been fully investigated. Autophagy and membrane remodelling, which is peculiar to late onset disease, might modify a clear response to enzyme replacement therapy and, also, compartmentalize the delivery of the recombinant enzyme. Danon disease, an X-linked dominant disorder, results from mutations in the lysosome-associated membrane protein-2 (LAMP2) gene and presents with hypertrophic cardiomyopathy, skeletal myopathy, and mental retardation. To investigate the effects of LAMP2 gene mutations on protein expression in different tissues, we screened LAMP2 gene mutations and LAMP-2 protein deficiency in the skeletal muscle of nine unrelated patients with hypertrophic cardiomyopathy and vacuolar myopathy. We identified three novel families (including one affected mother) with unreported LAMP2 gene null mutations and LAMP-2 protein deficiency in skeletal and myocardial muscle, leukocytes, and fibroblasts. LAMP-2 protein deficiency was detectable in various tissues, including leukocytes, explaining the multisystem clinical involvement. Skeletal muscle immunopathology showed that mutant protein was not localized in the Golgi complex, vacuolar membranes expressed sarcolemmal- specific proteins, and the degree of muscle fiber vacuolization correlated with clinical muscle involvement. In our female patient, muscle histopathology and LAMP-2 protein analysis was inconclusive, indicating that diagnosis in females requires mutation identification. The random X-chromosome inactivation found in muscle and leukocytes excluded the possibility that selective involvement of some tissues in females is due to skewed X-chromosome inactivation. Therefore, biochemical analysis of leukocytes might be used for screening in male patients, but genetic screening is required in females.
Scopo di questo studio è stato quello di analizzare a livello molecolare, biochimico e della patologia muscolare due gruppi di pazienti affetti dalla malattia di Danon e da glicogenosi di tipo II, in modo da acquisire nuove informazioni utili a tracciare possibili correlazioni genotipo-fenotipo e a chiarire i meccanismi patologici alla base di queste patologie. La Glicogenosi di tipo II (GSDII) è una malattia autosomica recessiva (OMIM # 232300) causata da un deficit dell’enzima mitocondriale ?-glucosidasi o maltasi acida (EC 3.2.1.20/3), che catalizza l’idrolisi dei legami glicogeno ? -1,4 e ? -1,6. Tale deficit enzimatico porta all’accumulo a livello lisosomale di glicogeno, che genera un’ampia eterogeneità clinica, che spazia da casi con esordio infantile e quadro clinico molto severo a forme più benigne con esordio tardivo nell’età adulta. Sono stati analizzati 23 pazienti con deficit di ?-glucosidasi acida per l’attività enzimatica mediante saggio fluorimetrico, l’espressione proteica mediante immunoblotting, la presenza di mutazioni nel gene GAA con SSCP e la patologia muscolare mediante immunocolorazione del Golgi e delle proteine sarcolemmali. L’attività enzimatica è risultata assente o minima nei casi ad esordio infantile e variabilmente ridotta nei pazienti con esordio tardivo. Le correlazioni genotipo-fenotipo indicano che la maggior parte dei pazienti ad esordio tardivo presentano la mutazione “leaky splicing” c.–32-13T>G in eterozigosi (un paziente era omozigote), ma il decorso della malattia è spesso difficile da prevedere solo sulla base delle mutazioni. Un risultato interessante deriva dall’analisi mediante western blot dell’espressione dell’?-glucosidasi nei pazienti: abbiamo infatti dimostrato che il muscolo di questi pazienti esprime prevalentemente forme inattive/immature dell’enzima ?-glucosidasi, mentre la forma matura della proteina è assente o presente a livelli molto ridotti. Inoltre, si è visto che l’eventuale quantità residua di forme proteiche mature riscontrate al western blot correla con i livelli di attività enzimatica riscontrati nel muscolo di questi pazienti. Il peso molecolare sia delle forme mature che di quelle immature/inattive è risultato essere maggiore nei pazienti rispetto ai muscoli di controllo. Attribuiamo tali differenze ad un’eccessiva sialilizzazione delle forme proteiche non funzionali, causata probabilmente da un loro trasporto ritardato o da una loro ritenzione nel complesso di Golgi, in cui agiscono le sialil-transferasi. A sostegno di tale ipotesi, abbiamo riscontrato una proliferazione del Golgi nelle fibre muscolari dei pazienti, causata possibilmente dalla ritenzione delle forme enzimatiche inattive, che non possono venire correttamente veicolate ai lisosomi. Le membrane vacuolari esprimono le proteine sarcolemmali nei pazienti con esordio tardivo ma non in quelli ad esordio infantile, suggerendo un’autofagia estesa ed un rimodellamento della membrana vacuolare nei pazienti ad esordio tardivo. La Malattia di Danon ha ereditarietà di tipo dominante legato al cromosoma X ed è causata da mutazioni nel gene LAMP2 (Lysosomal Associated Membrane Protein-2), e si presenta con cardiomiopatia ipertrofica, miopatia e ritardo mentale. Per studiare gli effetti delle mutazioni nel gene LAMP2 sull’espressione proteica in diversi tessuti, abbiamo effettuato uno screening molecolare ed un’analisi del difetto proteico sul tessuto muscolare, cardiaco, sui leucociti e fibroblasti di 9 soggetti maschi non correlati tra loro, con cardiomiopatia ipertrofica e miopatia vacuolare. Tre dei 9 soggetti analizzati hanno evidenziato un deficit proteico di LAMP2 generalizzato. Tale difetto è stato infatti riscontrato in tutti i tessuti da noi analizzati: tessuto muscolare scheletrico e cardiaco, leucociti e fibroblasti. Questo risultato indica che l’analisi biochimica può essere svolta in modo non invasivo sui leucociti, e potrebbe quindi essere impiegata nello screening dei soggetti maschi; inoltre, questo deficit multi-organo di proteina LAMP2 potrebbe spiegare il coinvolgimento clinico multisistemico. Abbiamo inoltre esteso l’analisi anche alla madre di un affetto: in questo caso il muscolo, i fibroblasti e i leucociti presentano livelli proteici comparabili al controllo normale. Sono state identificate mutazioni nel gene LAMP2 in tutti e 3 i pazienti maschi e nella femmina eterozigote. Ciascun paziente presentava una mutazione diversa e non riportata precedentemente in letteratura: sono tutte mutazioni nulle (nonsenso o frame-shifting) che ci si aspetta diano origine ad una proteina tronca, con perdita del dominio trans-membrana. ’istopatologia muscolare ha evidenziato una vacuolizzazione fibrale estesa e della degenerazione . L’analisi immunopatologica del muscolo scheletrico ha evidenziato che non vi è proliferazione del complesso del Golgi nei pazienti, che le membrane vacuolari esprimono le proteine sarcolemmali e che il grado di vacuolizzazione correla con il coinvolgimento clinico a livello muscolare. L’analisi dell’inattivazione del cromosoma X effettuata sul tessuto muscolare e sui leucociti ha escluso la possibilità che il coinvolgimento selettivo di alcuni tessuti nelle femmine sia dovuto ad una inattivazione non casuale dell’X

Pompe disease is a rare autosomal recessive condition caused by a deficiency in lysosomal alpha glucosidase. It is a progressive and often fatal muscular disease with wide variation in clinical presentation. Two broad clinical categories of Pompe disease have been identified; infantile- and late- onset. In the past decade, enzyme replacement therapy has shown promising results in treating the underlying pathology, resulting in improved clinical outcome. Clinical trials indicating that initiation of treatment at an earlier disease stage leads to a higher chance of preventing permanent damage have led to the proposition of introducing newborn screening for Pompe disease. All forms of Pompe disease are caused by the same pathology, and thus newborn screening has the potential to identify those affected with the more severe infantile-onset form as well as those with late-onset disease who may not present with symptoms until late in life.
The aim of this study was to investigate attitudes towards newborn screening for Pompe disease among affected adults, their family members and parents of ‘healthy’ children. Affected adults were recruited through support groups in Australia, the United Kingdom and United States; family members of affected adults were recruited from Australia; and parents of ‘healthy’ children were recruited through maternal child health clinics in Victoria, Australia. Participants completed questionnaires exploring their experiences of Pompe disease and/or newborn screening and their attitudes towards newborn screening for Pompe disease.
Support for newborn screening for Pompe disease was high among adults with Pompe disease (85.4%), parents of ‘healthy’ children (93.9%) and all three family members of affected adults who participated in this study. However, when offered a theoretical screening test that would only identify infantile-onset Pompe disease, 42.1% of adults with Pompe disease and 53.1% of parents of ‘healthy’ children preferred this screen, indicating that these stakeholders have some concerns regarding detection of late-onset disease in infancy. Factors influencing attitudes were investigated and support for newborn screening in affected adults was highly correlated with age of onset of disease; a preference to have been diagnosed in infancy; a belief that an earlier diagnosis would have made symptoms easier to cope with; and a stronger confidence in the efficacy of enzyme replacement therapy.
Potential benefits of diagnosis of late-onset disease in infancy were identified as being able to avoid the diagnosis odyssey, access enzyme replacement therapy at the optimal time, and allow individuals to make appropriate life choices. Participants identified increased anxiety in parents and the potential for over-protectiveness, in addition to possible discrimination, as harms of newborn screening for Pompe disease.
Families in which an infant is identified with the potential for late-onset Pompe disease will need assistance to adapt to and manage this diagnosis, so that anxiety is minimised and unnecessary limitations are not placed on the child. Whilst potential medical and psychosocial benefits can result from newborn screening, it is important to carefully consider the potential for harm and the resources required to appropriately manage these so that ultimately benefit outweighs harm.

La glycogénose de type Ia (GSDIa) est une maladie métabolique rare causée par une déficience en glucose-6-phosphatase (G6Pase), due à des mutations de la sous-unité catalytique (G6PC). Cette enzyme confère au foie, aux reins et à l’intestin la capacité de produire du glucose. Les patients atteints de GSDIa sont donc incapables de produire du glucose et souffrent d’hypoglycémies sévères lors de jeûnes courts. De plus, la déficience en G6Pase provoque une accumulation de glucose-6 phosphate dans le foie et les reins, conduisant à l’accumulation de glycogène et de lipides. A long terme, la plupart des patients souffre d’une maladie chronique rénale (MCR), qui peut évoluer en insuffisance rénale, nécessitant une mise sous dialyse ou une transplantation rénale. Cette MCR se caractérise par une fibrose, ainsi que par le développement de kystes dans les stades tardifs. Au niveau du foie, les patients développent une hépatomégalie et une stéatose hépatique qui peut évoluer vers le développement d’adénomes ou carcinomes hépatocellulaires. Le but de mes travaux de thèse a été d’identifier les mécanismes moléculaires impliqués dans l’établissement de la pathologie rénale et la formation des kystes, à l’aide de modèles murins invalidés pour le gène G6pc spécifiquement dans les reins (souris K.G6pc-/-). Alors que la GSDIa est une maladie caractérisée par l’accumulation hépatique et rénale de glycogène, nous avons d’abord montré que le développement de la fibrose, à l’origine de la perte de la fonction rénale, était induit par l’accumulation de lipides, indépendamment du contenu en glycogène. De plus, l’utilisation d’un agoniste de PPARα, le fénofibrate, en diminuant le contenu lipidique rénal, a ralenti l’installation de la fibrose et l’évolution de la MCR. Le mécanisme moléculaire impliqué est l’activation du système rénine angiotensine par les dérivés lipidiques, qui induit l’expression du facteur profibrotique TGFβ1. De même, le fénofibrate en limitant l’accumulation de lipides hépatiques a prévenu le développement d’atteintes hépatiques caractéristiques de la GSDI. Ainsi, l’activation du catabolisme des lipides par des agonistes de PPARα semble une stratégie thérapeutique intéressante pour réduire la progression des maladies rénales et hépatique de la GSDI. La deuxième partie de mes résultats suggèrent que le développement de kystes rénaux chez les patients atteints de la GSDI pourrait être causé par une altération du cil primaire, organelle jouant un rôle clé dans le maintien d’une structure et fonction normale des reins. En effet, une augmentation de la longueur du cil primaire a pu être observée dans les reins des souris K.G6pc-/- associée à une dérégulation de différentes protéines impliquées dans sa structure et sa fonction, par rapport aux souris contrôles. Nous avons également mis en évidence une reprogrammation métabolique de type Warburg, caractérisée par une activation accrue de la glycolyse aérobie, une inhibition de l’oxydation mitochondriale du pyruvate et une production de lipides. Ainsi, l’ensemble de ces perturbations va favoriser la prolifération cellulaire et le développement de kystes, et pourrait mener au développement de tumeur rénale comme observée chez une souris K.G6pc-/-. En conclusion nous avons démontré que, dans le cadre de la GSDI, l’accumulation de lipides dans les reins et le foie, secondaire à la déficience en G6Pase, joue un rôle clé dans le développement des complications hépatiques et rénales à long terme. Également, la reprogrammation métabolique rénale de type Warburg, prenant place dans le cadre de la GSDI, associée à un défaut du cil primaire pourrait être à l’origine de la formation des kystes et de tumeurs rénales. Ces études, en permettant une meilleure compréhension de la physiopathologie des complications à long terme de la GSDIa, offrent de nouvelles perspectives concernant les stratégies thérapeutiques à développer pour une meilleure prise en charge des patients atteints de GSDIa
Glycogen storage disease type Ia (GSDIa) is a rare metabolic disease caused by glucose-6-phosphatase (G6Pase) deficiency, due to mutations on the gene encoding G6Pase catalytic subunit (G6PC). This enzyme confers to the liver, kidneys and intestine the ability to produce glucose. Thus, patients with GSDIa are unable to ensure endogenous glucose production and suffer from severe hypoglycemia during fasting in the absence of nutritional control. In addition, G6Pase deficiency causes intracellular accumulation of glucose-6 phosphate in the liver and kidneys, leading to metabolic defects and the accumulation of glycogen and lipids. Over time, most adult patients suffer from chronic kidney disease (CKD), which can progress to kidney failure, requiring dialysis or kidney transplantation. This nephropathy is characterized in particular by tubulo-interstitial fibrosis and glomerulosclerosis, as well as by the development of cysts in the late stages. Moreover, patients develop hepatomegaly and hepatic steatosis that may progress to the development of hepatocellular adenomas or carcinomas. The aim of my thesis was to identify the molecular mechanisms involved in the establishment of renal pathology and cyst formation in GSDIa, by using mouse models where G6pc gene is specifically deleted in the kidneys (K.G6pc-/- mice). While GSDIa is a disease characterized by glycogen accumulation in the liver and kidneys, we first showed that the development of fibrosis, which causes progressive loss of kidney function, was induced by intracellular accumulation of lipids, regardless of glycogen content. The molecular mechanism probably involved is the activation of the renin angiotensin system by lipid derivatives such as diacylglycerol, which induced the expression of the profibrotic factor TGFβ1 and an epithelial-mesenchymal transition. In addition, the use of a PPARα agonist, i.e. fenofibrate, by decreasing renal lipid content, reduced the development of fibrosis and CKD evolution. Similarly, fenofibrate treatment prevented the accumulation of lipids in the liver and the development of liver damages that cause tumor development. Thus, the activation of lipid catabolism by PPARα agonists such as fenofibrate seems to be an interesting therapeutic strategy to reduce the progression of renal and hepatic diseases of GSDIa. The second part of my results suggest that the development of renal cysts in GSDI patients may be caused by an alteration of the primary cilia, a non-motile organelle that plays a key role in maintaining normal kidney structure and function. Indeed, defects in the primary cilia are involved in many polycystic kidney diseases. In summary, an increase in the length of the primary cilia was observed in the kidneys of K.G6pc-/- mice, which could be explained by a deregulation of the expression of different proteins involved in cilia structure and function, compared to control mice. We also demonstrated a metabolic reprogramming leading to a Warburg metabolism, characterized by the increased activation of aerobic glycolysis and the inhibition of mitochondrial pyruvate oxidation and lipid production in K.G6pc-/- mice. Thus, all these disorders would promote cell proliferation and cyst development, and could lead to the development of renal tumor, as recently observed in one K.G6pc-/- mouse (out of 36 studied mice). In conclusion, we have shown that, in GSDI, the accumulation of lipids in the kidneys and liver that occurs secondary to G6Pase deficiency plays a key role in the development of hepatic and renal long-term complications. In addition, the Warburg like metabolic reprogramming taking place in the GSDIa kidneys, associated with a defect in the primary cilia, could be at the origin of cysts formation and renal tumors. These new studies, by providing a better understanding of the pathophysiology of long-term complications of GSDIa, offer new perspectives on therapeutic strategies to be developed for better management of patients

La glycogénose de type I (GSDI) est une maladie génétique rare, due à une déficience en glucose-6 phosphatase (G6Pase), enzyme clé de la production endogène de glucose. En plus des hypoglycémies sévères, la perte de l'activité G6Pase conduit à l'accumulation de glycogène, mais aussi de lipides dans le foie et les reins. A long-terme, la plupart des patients développent des tumeurs hépatiques et une maladie rénale chronique (MRC).Le but de cette thèse a été de caractériser les mécanismes moléculaires impliqués dans la carcinogenèse hépatique et la MRC grâce à des modèles murins viables et uniques, avec une délétion de la G6Pase spécifiquement dans le foie ou les reins, reproduisant respectivement toutes les caractéristiques de la pathologie hépatique ou rénale.Au niveau du foie, notre étude a permis de mettre en évidence une reprogrammation métabolique « Warburg-like » très similaire à celle des cellules cancéreuses, associée à une perte des défenses cellulaires et des suppresseurs de tumeur. De plus, nous avons montré que les adénomes hépatocellulaires, se transformant ensuite en carcinomes, se développent en absence de fibrose, en accord avec l'absence d'activation des voies pro-fibrotiques. Au niveau des reins, l'étude de la MRC a mis en évidence le développement de kystes rénaux chez les souris atteintes de GSDI, observés aussi chez les patients à un stade avancé de la MRC. Finalement, une dernière étude portant sur l'activation de l'oxydation des lipides, par un traitement des souris au fénofibrate, a permis de suggérer le rôle délétère de l'accumulation des lipides dans le développement des pathologies hépatique et rénale
Glycogen storage disease type I (GSDI) is a rare genetic disease, due to a deficiency in glucose-6 phosphatase (G6Pase), a key enzyme in the endogenous glucose production. Besides severe hypoglycemia, the loss of G6Pase leads to the accumulation of glycogen and lipids in the liver and kidneys. On the long term, most patients develop hepatic tumors and chronic kidney disease (CKD).The goal of this thesis was to characterize the molecular mechanisms involved in hepatic carcinogenesis and CKD, thanks to viable and unique mouse models with specific deletion of G6Pase in the liver or kidneys, which exhibit all hallmarks of hepatic and renal pathologies, respectively.On a hepatic level, our study allowed us to highlight a « Warburg-like » metabolic reprogramming, very similar to what is observed in cancer cells, associated with a loss of cellular defenses and tumor suppressors. Furthermore, we showed that formation of hepatocellular adenoma, which transform later in carcinoma, occurs in the absence of liver fibrosis, due to the fact that pro-fibrotic pathways are not activated. In the kidneys, the study of CKD highlighted the development of renal cysts in mice with GSDI, as well as in the patients presenting an advanced stage of CKD. Finally, the last study on the activation of the oxidation of lipids, by treating the mice with fenofibrate, allowed us to suggest a deleterious role of lipid accumulation in the development of the hepatic and renal pathologies

La glycogénose de type Ia (GSDIa) est une maladie métabolique rare causée par un déficit en glucose-6- phosphatase (G6Pase), menant à l'absence de production endogène de glucose. Cette pathologie est caractérisée par des hypoglycémies sévères, une hépatomégalie et une stéatose hépatique ainsi qu'une néphromégalie. En absence de traitement curatif, la prise en charge de cette maladie repose actuellement sur des mesures diététiques très strictes. Cependant, des complications apparaissent avec l'âge comme le développement de tumeurs hépatiques et la progression de la néphropathie vers l'insuffisance rénale. Afin d'étudier l'évolution de cette pathologie à long terme, nous avons utilisé des modèles murins originaux présentant une invalidation du gène de la sous-unité catalytique de la G6Pase spécifiquement au niveau du foie ou des reins. Dans ce travail, nous avons démontré que la déficience en G6Pase uniquement au niveau des reins est suffisante pour entrainer le développement de la pathologie rénale de la GSDIa. Les souris déficientes en G6Pase hépatique nous ont permis de mettre en évidence les effets délétères d'une consommation modérée de fructose ou de galactose et d'une alimentation riche en lipides, de type « cafétéria », sur la pathologie hépatique de la GSDIa, en particulier sur le développement tumoral. Nous avons également démontré chez ces souris l'efficacité et l'innocuité d'un traitement par thérapie génique ciblant le foie. Le transfert de gène avec un vecteur lentiviral, permettant l'intégration du transgène au génome, semble plus efficace qu'avec un vecteur AAV pour prévenir le développement de la pathologie hépatique de la GSDIa et l'apparition des tumeurs
Glycogen storage disease type Ia (GSDIa) is a rare metabolic disease caused by glucose-6-phosphatase (G6Pase) deficiency, leading to the absence of endogenous glucose production. This pathology is characterized by severe hypoglycemia, hepatomegaly, hepatic steatosis and nephromegaly. In the absence of a curative therapy, the current treatments available consist in strict dietary management. However, various complications occur with aging, such as hepatic tumor development and progressive chronic renal disease leading to renal failure. In order to study the long term pathology development, we used original mouse models, presenting an invalidation of the gene encoding the G6Pase catalytic subunit, specifically in the liver or in the kidneys. In this work, we demonstrated that renal G6Pase deficiency alone is sufficient to induce the development of the GSDIa nephropathy. Mice with liver-specific G6Pase deficiency allowed us to highlight the deleterious effects of high-fat diet, such as « fast-food » diet, as well as moderate consumption of fructose or galactose on the hepatic GSDIa pathology, particularly on tumor development. Furthermore, we demonstrated the efficiency and innocuity of gene therapies targeting the liver in these mice. Gene transfer with a lentiviral vector, allowing transgene integration into the genome, seems to be more efficient than an AAV vector in preventing the development of hepatic GSDIa pathology and tumor formation

La glycogénose de type I (GSDI) est une maladie génétique rare, due à une déficience en glucose-6 phosphatase (G6Pase), enzyme clé de la production endogène de glucose. En plus des hypoglycémies sévères, la perte de l'activité G6Pase conduit à l'accumulation de glycogène, mais aussi de lipides dans le foie et les reins. A long-terme, la plupart des patients développent des tumeurs hépatiques et une maladie rénale chronique (MRC).Le but de cette thèse a été de caractériser les mécanismes moléculaires impliqués dans la carcinogenèse hépatique et la MRC grâce à des modèles murins viables et uniques, avec une délétion de la G6Pase spécifiquement dans le foie ou les reins, reproduisant respectivement toutes les caractéristiques de la pathologie hépatique ou rénale.Au niveau du foie, notre étude a permis de mettre en évidence une reprogrammation métabolique « Warburg-like » très similaire à celle des cellules cancéreuses, associée à une perte des défenses cellulaires et des suppresseurs de tumeur. De plus, nous avons montré que les adénomes hépatocellulaires, se transformant ensuite en carcinomes, se développent en absence de fibrose, en accord avec l'absence d'activation des voies pro-fibrotiques. Au niveau des reins, l'étude de la MRC a mis en évidence le développement de kystes rénaux chez les souris atteintes de GSDI, observés aussi chez les patients à un stade avancé de la MRC. Finalement, une dernière étude portant sur l'activation de l'oxydation des lipides, par un traitement des souris au fénofibrate, a permis de suggérer le rôle délétère de l'accumulation des lipides dans le développement des pathologies hépatique et rénale
Glycogen storage disease type I (GSDI) is a rare genetic disease, due to a deficiency in glucose-6 phosphatase (G6Pase), a key enzyme in the endogenous glucose production. Besides severe hypoglycemia, the loss of G6Pase leads to the accumulation of glycogen and lipids in the liver and kidneys. On the long term, most patients develop hepatic tumors and chronic kidney disease (CKD).The goal of this thesis was to characterize the molecular mechanisms involved in hepatic carcinogenesis and CKD, thanks to viable and unique mouse models with specific deletion of G6Pase in the liver or kidneys, which exhibit all hallmarks of hepatic and renal pathologies, respectively.On a hepatic level, our study allowed us to highlight a « Warburg-like » metabolic reprogramming, very similar to what is observed in cancer cells, associated with a loss of cellular defenses and tumor suppressors. Furthermore, we showed that formation of hepatocellular adenoma, which transform later in carcinoma, occurs in the absence of liver fibrosis, due to the fact that pro-fibrotic pathways are not activated. In the kidneys, the study of CKD highlighted the development of renal cysts in mice with GSDI, as well as in the patients presenting an advanced stage of CKD. Finally, the last study on the activation of the oxidation of lipids, by treating the mice with fenofibrate, allowed us to suggest a deleterious role of lipid accumulation in the development of the hepatic and renal pathologies

La glycogénose de type 1a (GSD1a) est une maladie métabolique rare liée à une absence d’activité glucose‐6 phosphatase (G6Pase). La G6Pase est une enzyme clé de la production endogène de glucose (PEG) catalysant l’hydrolyse du G6P en glucose avant sa libération dans le sang. Cette fonction est restreinte au foie, aux reins et à l’intestin. La GSD1a est caractérisée par des hypoglycémies chroniques, une hépatomégalie associée à une stéatose hépatique et une néphromégalie. A plus longterme, la plupart des patients développent des adénomes. Un modèle murin de GSD 1a existe mais les souris ne survivent pas après le sevrage. Nous avons donc généré un modèle original de GSD1a, en invalidant le gène de la sous‐unité catalytique de la G6Pase spécifiquement dans le foie, grâce à une stratégie CRE‐LOX inductible (souris L‐G6pc‐/‐). Dans ce travail, nous avons montré que les souris L‐G6pc‐/‐ sont viables et reproduisent parfaitement la pathologie hépatique de la GSD1a, y compris le développement d’adénomes hépatiques après 9 mois d’invalidation. La viabilité des souris nous a permis de débuter des traitements par thérapie génique ciblant le foie à l’aide de vecteurs lentiviraux et AAV. La survie de ces souris, qui ne peuvent pas produire du glucose par le foie, repose la question du rôle relatif de la production hépatique de glucose dans la régulation de la glycémie Nous avons montré que les souris L‐G6pc‐/‐ sont capables de réguler leur glycémie, même au cours d’un jeûne prolongé. Ce maintien de l’homéostasie glucidique est due à une induction rapide de la néoglucogenèse rénale et intestinale, principalement par un mécanisme dépendant du glucagon
Glycogen storage disease type 1a (GSD1a) is a rare metabolic disorder due to an absence of glucose‐6 phosphatase (G6Pase) activity. G6Pase is the key enzyme of endogenous glucose production (EGP) and catalyzes the last step before the glucose release into the bloodstream. This function to produce glucose is restricted to the liver, the kidneys and the intestine. GSD1a is characterized by chronic hypoglycemia, hepatomegaly associated with hepatic steatosis and nephromegaly. The longterm complications of G6Pase deficiency include hepatocellular adenomas. The available animal model of GSD1a rarely survive over three months of age and the study of mechanisms of hepatocellular adenomas development cannot be investigated. So, we generated an original mouse model of GSD1a with a liver‐specific invalidation of catalytic subunit of G6Pase gene by an inducible CRE‐LOX strategy (L‐G6pc‐/‐ mice). In this work, we demonstrated that L‐G6pc‐/‐ were viable and totally reproduced the liver pathology of GSD1a, including the late development of hepatocellular adenomas. Then, we have begun liver gene therapy treatment using lentiviral and AAV vectors to correct the hepatic pathology. Finally, concerning glucose homeostasis, we have demonstrated that L‐G6pc‐/‐ were able to regulate blood glucose, during prolonged fast, even in the absence of hepatic glucose production. Rapidly, L‐G6pc‐/‐ mice were able to induce renal and intestinal gluconeogenesis thanks to a key role of glucagon and the development of a metabolic acidosis. These results provide evidence that the major role of the liver for EGP during fasting requires re‐examination

A doença de Pompe (GSDII), autossômica recessiva, é causada pela deficiência da enzima lisossomal que degrada o glicogênio, -glucosidase ácida (GAA). O quadro clínico varia de acordo com a idade de início da doença, grau de progressão e envolvimento dos tecidos: predominantemente cardíaco e muscular esquelético na forma de início-precoce (FIP) e mais restrito no músculo esquelético na forma de início-tardio (FIT). A sobrevida média na FIP é de 9-12 meses. Com avanço dos métodos histológicos, histoquímicos e imunoistoquímicos intensificou-se a análise estrutural e funcional dos tipos de fibras musculares. O estudo da vascularização também é de importância pelo aporte nutricional e funcional das fibras. O objetivo do presente trabalho é analisar a correlação da distribuição do tipo de fibras com a forma de apresentação clínica da doença de Pompe, seu genótipo correspondente e a quantidade residual da enzima GAA. Analisou-se 10 biópsias musculares de pacientes FIP e 09 de FIT comparados com o grupo controle, pareados por idade e gênero. Os pacientes foram selecionados segundo dados clínicos e laboratoriais, sendo feito o seqüenciamento de toda parte codificante do gene e Western Blotting (WB) com anticorpo monoclonal 15362-157, cedido pela Genzyme (primário 1:200 e secundário 1:10.000). A confirmação do diagnóstico foi feita através da medida da atividade residual de GAA em papel filtro, da presença de miopatia vacuolar com grânulos PAS e fosfatase ácida positivos em biópsia muscular e pela presença de mutação no gene GAA. A reação de imunoistoquímica foi realizada para fibras tipo I (lenta), tipo II (rápida) e densidade capilar (ulex), utilizando anticorpos monoclonais, respectivamente: antimiosina lenta (1:80), anti-miosina rápida (1:40) da Novocastra e ulex da Vector (1:800). A contagem das fibras foi realizada por 2 observadores em todo fragmento do corte transversal da biópsia com auxílio de um programa semi-automatizado. Observou-se predomínio de fibras tipo II em ambos os gêneros na FIP e predomínio de fibras tipo I em mulheres e tipo II em homens, na FIT. Aumento da densidade capilar, em comparação com os controles, foi notada em ambas as formas IP e IT. Verificou-se em média 90% de fibras vacuoladas nos casos FIP com completa distorção da arquitetura, enquanto na FIT, a porcentagem de fibras vacuoladas foi variável (0-88%). Como alguns genes constitutivos influenciam na distribuição das fibras musculares, como o gene ACE, o polimorfismo deste gene foi analisado quanto aos genótipos I/I, D/D e I/D. Observou-se ausência de concordância entre o genótipo do ACE e a distribuição de fibras em 60% dos casos da FIP e FIT, atribuindo-se o resultado da distribuição do tipo de fibras como parte da patologia da doença de Pompe. A gravidade da doença variou inversamente com a quantidade de enzima residual, sendo compatível com o quadro clínico do paciente. A presença de mutação deletéria em ambos os alelos foi observada em 3/10 casos de IP, sendo que todos os 3 casos apresentaram ausência total de enzima no WB. Há maior envolvimento de fibras tipo II em GSDII, sem depleção da microcirculação muscular. Estudos demonstram que a remoção do depósito de glicogênio ocorre diferencialmente nos tipos de fibra, sendo menos eficiente nas fibras tipo II. O achado do presente estudo poderá ter implicações na resposta à recente terapêutica proposta por reposição enzimática.
The glycogen storage disease type II (GSDII), autosomal recessive disorder, is caused by the deficiency of GAA (acid -glucosidase) a lysossomal enzyme that degrades the glycogen. The clinical findings are in accordance to great variability of age onset, degree of disease progression and extent of tissue involvement: predominantly cardiac and skeletal muscle in the infantile form (I) and more restricted to the skeletal muscle in the late-onset form (LO). The average survival time of the infantile form is 9-12 months. With advances of the histological, histochemical and imunohistochemical methods structural and functional analysis of muscle fiber types were intensified. The study of the capillary density is also important for nutritional and functional aspects. The objective of the present work is to analyze the correlations of the fiber type distribution to clinical presentation, genotype and residual GAA enzymatic activity. We analyzed 10 muscle biopsies of infantile and 09 of late-onset patients and compared to age and gender matched controls. The patients were selected according to clinical and laboratorial data, molecular diagnosis by full gene sequencing, and Western Blotting (WB) with monoclonal antibody 15362-157, courtesy Genzyme Science Group (primary 1:200 and secondary 1:10.000). Diagnostic confirmation was made by GAA enzymatic measurement in DBS, presence of vacuolar myopathy in muscle biopsy, and presence of mutation in GAA gene. The imunohistochemical study was carried out by detection of type I (slow), type II (fast) fibers and capillaries, using monoclonal antibodies, respectively: anti-slow myosin (1:80), anti-fast myosin (1:40) (Novocastra) and ulex (1:800) (Vector). Morphometry was performed by 2 observers using a half-automatized program. Type II fiber predominance was observed in both gender in the infantile form, type I fiber predominance in women and type II predominance in men with LO. Increase of the capillary density, in comparison to controls was noticed in both forms. 90% of vacuolated fibers with complete distortion of fiber architecture were demonstrated in I cases, while in LO, the percentage of vacuolated fibers ranged from 0 to 88%. As some constitutive gene, like ACE, influence muscle fiber distribution, its polymorphisms I/I, D/D and I/D gene were analyzed. Absence of agreement was observed between ACE genotype and fiber type distribution in 60% of I and LO cases, which was attributed as consequence of Pompe disease pathology itself. The disease severity varied inversely to the amount of residual GAA enzymatic activity, being compatible with the patient clinical findings. The presence of deleterious mutation in both alleles was observed in 3/10 infantile cases, and all 3 presented total enzyme absence at WB. A greater fiber type II involvement was observed in GSDII, without decrease in muscle capillary density. Recent studies demonstrated that glycogen deposit removal occurs distinctively in different fiber types, being less efficient in type II fibers. The present findings might have implications in the reply to the recent proposed enzyme replacement therapy.

Lam Ching-wan.
"May 2000."
Thesis (Ph.D.)--Chinese University of Hong Kong, 2000.
Includes bibliographical references (p. 91-101).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Mode of access: World Wide Web.
Abstracts in English and Chinese.

Indiana University-Purdue University Indianapolis (IUPUI)
Pompe disease (PD) is a rare metabolic myopathy characterized by loss of acid alpha-glucosidase (GAA), the enzyme responsible for breaking down glycogen to glucose within the lysosomes. PD cells accumulate massive quantities of glycogen within their lysosomes, and as such, PD is classified as a “lysosomal storage disease” (LSD). GAA-deficient cells also exhibit accumulation of autophagic debris. Symptoms of severe infantile PD include extreme muscle weakness, hypotonia, and hypertrophic cardiomyopathy, resulting in death before one year of age. Certain LSDs are currently being successfully treated with enzyme replacement therapy (ERT), which involves intravenous infusion of a recombinant enzyme to counteract the endogenous deficiency. ERT has been less successful in PD, however, due to ineffective delivery of the recombinant enzyme. Alternatively, specific genes deletion may reduce lysosomal glycogen load, and could thus be targeted in PD therapy development. Absence of malin (EPM2B) or laforin (EPM2A) has been proposed to impair autophagy, which could reduce lysosomal glycogen levels. Additionally, deficiency of Stbd1 has been postulated to disable lysosomal glycogen import. Furthermore, Ptg deficiency was previously reported to abrogate Lafora body formation and correct neurological abnormalities in Lafora disease mouse models and could have similar effects on PD pathologies. The goal of this study was to characterize the effects of homozygous disruption of Epm2a, Epm2b, Stbd1, and Ptg loci on total glycogen levels in PD mouse model heart tissue, as in severe infantile PD, it is accumulation of glycogen in the heart that results in fatal hypertrophic cardiomyopathy. Gaa-/- mice were intercrossed with Epm2a-/-, Epm2b-/-, Stbd1-/-, and Ptg-/- mice to generate wildtype (WT), single knockout, and double knockout mice. The results indicated that Gaa-/- hearts accumulated up to 100-fold more glycogen than the WT. These mice also displayed cardiac hypertrophy. However, deficiency of Epm2a, Epm2b, Stbd1, or PTG in the Gaa-/- background did not reveal changes of statistical significance in either heart glycogen or cardiac hypertrophy. Nevertheless, since total glycogen was measured, these deficiencies should not be discarded in future discussions of PD therapy, as increasing sample sizes and/or distinguishing cytosolic from lysosomal glycogen content may yet reveal differences of greater significance.

G6Pase-alpha and G6Pase-beta share kinetic properties and active site structures, which lie on the luminal side of the endoplasmic reticulum (ER). For hydrolysis of G6P to glucose, G6Pase-alpha or G6Pase-beta must couple with an ubiquitously expressed ER-transmembrane protein, the G6P transporter (G6PT) that translocates G6P from the cytoplasm into the lumen of the ER. The primary role of the G6Pase/G6PT complex is therefore to provide endogenous glucose to the ER lumen. The essential role of the G6Pase-alpha/G6PT complex in glucose homeostasis has been well established, and the deficiencies in G6Pase-alpha and G6PT cause glycogen storage disease type Ia (GSD-Ia) and GSD-Ib, respectively. Both patients manifest the same metabolic phenotype of disturbed glucose homeostasis. While the metabolic abnormalities of GSD-Ia and GSD-Ib are almost identical, GSD-Ib patients exhibit neutropenia and myeloid dysfunctions which are not observed in GSD-Ia patients. Since G6Pase-beta and G6PT share an ubiquitous expression pattern, we hypothesized that the G6Pase-beta/G6PT complex might be functional in neutrophils and that the myeloid defects in GSD-Ib are due to the loss of activity of that complex. To test this hypothesis, we generated G6Pase-beta-deficient (G6pc3 --/--) mouse strains and showed that G6pc3--/-- mice manifest neutropenia; defects in neutrophil respiratory burst, chemotaxis, and calcium flux; and increased susceptibility to bacterial infection mimicking GSD-Ib patients. Consistent with this, G6pc3--/-- neutrophils exhibit enhanced ER stress and apoptosis. Taken together, the results demonstrate that endogenous glucose production in the ER via G6P translocation and metabolism are critical for normal neutrophil functions and that an ER stress-mediated neutrophil apoptosis is one mechanism underlying myeloid dysfunctions in the G6pc3--/-- mice.
Macrophages are the abundant leukocytes in the decidua throughout pregnancy and were thought to play a vital role in decidual homeostasis, placental development, and maintenance of a successful pregnancy. We hypothesized that endogenous glucose production in the ER might also be critical for normal macrophage function and G6pc3--/-- females manifesting neutropenia, neutrophil and macrophage dysfunctions might suffer from pregnancy-associated complications. Here we show that G6pc3--/-- macrophages exhibited impaired respiratory burst activity and repressed trafficking in vivo during an inflammatory response. The litter size and pregnancy frequency were markedly reduced in female G6pc3--/-- matings as compared to female G6pc3+/--/G6pc3+/+ matings, indicative of reduced fertility. The pregnancy-associated mortality risk was greatly increased in G6pc3--/--. Pathological analyses revealed that the sick or dying G6pc3--/-- mothers were emaciated and suffered from dental dysplasia and otitis media. Consistent with this, parental male and female G6pc3--/-- mice were more neutropenic than their age-matched virgin G6pc3 --/-- mice. Taken together, our results show that macrophage dysfunction, defective macrophage trafficking, neutrophil dysfunction, and enhanced neutropenia underlie the reduced fertility and increased mortality of G6pc3--/-- mothers.
Cheung, Yuk Yin.
Advisers: Janice Chou; Kam Bo Wong.
Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: .
Thesis (Ph.D.)--Chinese University of Hong Kong, 2009.
Includes bibliographical references (leaves 92-107).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstract also in Chinese.

Indiana University-Purdue University Indianapolis (IUPUI)
Glycogen, a branched polymer of glucose, acts as an intracellular carbon and energy reserve in many tissues and cell types. The breakdown of glycogen by hormonally regulated degradation involving the coordinated action of glycogen phosphorylase and debranching enzyme has been well studied. However, the importance of lysosomal disposal of glycogen has been underscored by a glycogen storage disorder, Pompe disease. This disease destroys tissues by over-accumulating glycogen in lysosomes due to a genetic defect in the lysosomal acid α-glucosidase. Details of the intracellular trafficking of glycogen are not well understood. Starch-binding domain-containing protein 1 (Stbd1) is a protein of previously unknown function with predicted hydrophobic N-terminus and C-terminal CBM20 carbohydrate binding domain. The protein is highly expressed in the liver and muscle, the major repositories of glycogen. Stbd1 binds to glycogen in vitro and in vivo with a preference for less branched and more phosphorylated polysaccharides. In animal models, the protein level of Stbd1 correlates with the genetic depletion of glycogen. Endogenous Stbd1 is found in perinuclear compartments in cultured mouse and rat cells. When over-expressed in cells, Stbd1 accumulates and coincides with glycogen and GABARAPL1, the autophagy protein. They form enlarged perinuclear structures which are abolished by removing the hydrophobic N-terminus of Stbd1. Stbd1, with point mutations in the CBM20 domain, retains the perinuclear localization but without concentration of glycogen in this compartment. In cells that are stably over-expressing glycogen synthase, glycogen exists as large perinuclear deposits, where Stbd1 can also be present. Removing glucose from the culture leads to a breakdown of the massive glycogen accumulation into numerous smaller and scattered deposits which are still positive for Stbd1. Furthermore, the autophagy protein GABARAPL1 co-immunoprecipates and co-localizes with Stbd1 when co-expressed in cells. Point mutation or deletion of the autophagy protein interacting region on Stbd1 eliminates the interaction and co-localization with GABARAPL1 but not the characteristic perinuclear distribution of Stbd1. We propose that Stbd1 is involved in glycogen metabolism. In particular, it participates in the vesicular transfer of glycogen to the lysosome with the recruitment of autophagy related proteins GABARAPL1 and/or GABARAP, as these vesicles mature prior to lysosomal fusion.

For the development of a G6PD-deficient mouse model, we introduced the mutant Gpdxa-m1Neu allele (a severe ENU-induced mutation that results in 13-15% G6PD activities of wild type littermates) into the C57L/J background (a strain that constitutively exhibits low G6PD activity) through a breeding program. Of significance is that 78% of the F2 generation had G6PD activities <2 U/g Hb, levels similar to those of severe G6PD deficiency in human. The efficacy of this model was preliminary verified by the known haemolytic agent, naphthalene, as demonstrated by the decrease of GSH/GSSG ratio by 24.6% (P=0.032) and increase of methaemoglobin by 4.5 fold (P=0.8) when compared with the respective control without treatment.
Genetic analysis of 14 mutation hotpots was performed on 98 hemi-/homozygous and 17 heterozygous G6PD-deficient human subjects. We developed a novel Multiplex Primer Extension Reaction (MPER) assay and detected seven specific mutations in 97 subjects: c.1376G>T (33.7%), c.1388G>A (29.6%), c.871G>A + c.1311C>T (12.3%), c.95A>G (9.2%), c.392G>T (7.1%), c.1024C>T (6.2%) and c.1360C>T (1.0%). For the genotyping of 15 heterozygous female, all mutations were identified as follows: c.1376G>T/Normal (33.3%), c.1388G>A/Normal (26.7%), c.871G>A/Normal + c.1311C>T/Normal (20.0%), c.95A>G/Normal (13.3%) and c.392G>T./Normal (6.7%). The c.871G>A and 'silent' mutation c.1311 C>T was newly found to coexist in a high proportion of genotype in our population.
Glucose-6-phosphate dehydrogenase (G6PD)-deficient subjects are vulnerable to chemical-induced haemolysis if exposed to oxidative agents. Little is known, however, of the haemolytic effects of Chinese herbal medicine on G6PD-deficient subjects. Only one case study has reported that a G6PD-deficient newborn developed severe haemolysis after ingestion of Rhizoma Coptidis. Besides, recent studies reported that green tea and its constituents exerted pro-oxidative effects on cellular systems in culture.
Glucose-6-phosphate dehydrogenase deficiency is a genetic disorder inherited in the X-linked manner. The condition is prevalent in the Mediterranean region, Africa and Southeast Asia. In Hong Kong, the frequency of G6PD deficiency is around 4.5% in males and 0.3% in females. Over 140 specific mutations of the X-linked gene for G6PD have been characterized in various geographic regions. However, the local mutation pattern has not been clearly determined.
In conclusion, some Chinese herbal medicine, tea and tea polyphenols significantly altered the oxidative status of G6PD-deficient erythrocytes in vitro. Their in vivo effects on G6PD-deficient individuals would be further investigated by the novel G6PD-dificient mouse model.
In this study, we aim (1) to investigate effects of (a) a panel of Chinese Herbal Medicine (CHM), (b) tea and its constituents, on the oxidative status of human G6PD-deficient erythrocytes in vitro ; (2) to characterize the genotype of G6PD-deficiency in the Chinese population and their specific response to oxidative stress; (3) to develop a novel strain of mice as a model for study of chemicals agents on G6PD-deficient red cell in vivo.
Our results showed that six of eighteen CHM significantly reduced GSH levels in the G6PD-deficient erythrocytes (p<0.05, n=10). After exposure to 1 mg/mL of Rhizoma Coptidis, GSH levels in G6PD-deficient erythrocytes was decreased by 48.9 +/- 5.4% (P<0.001, n=10). At 5 mg/mL of Cortex Moutan, Radix Rehmanniae, Radix Bupleuri, Rhizoma Polygoni Cuspidati and Flos Chimonanthi, GSH levels were decreased significantly (P=0.001 to 0.004) by 51.8 +/- 7.6%, 25.9 +/- 6.7%, 21.0 +/- 6.9%, 17.5 $ 6.7% and 8.7 +/- 6.8% respectively. There were noticeable increases in levels of methaemoglobin by 2.8 fold (5 mg/mL, P=0.012) and 3.4 fold (10 mg/mL, P=0.016) in the presence of Rhizoma Coptidis and Cortex Moutan, respectively, in G6PD-deficient erythrocytes.
We also investigated the pro-oxidative effect of tea and its polyphenolic components on G6PD erythrocytes from G6PD-deficient (n=8) and normal adult (n=8) subjects. The tea extracts significantly reduced GSH and increased GSSG levels in G6PD-deficient erythrocytes in a dose-dependent manner (0.5-10 mg/mL), but not in normal erythrocytes. Similar dose-dependent responses to (-)-Epigallocatechin (EGC) and (-)-Epigallocatechin-3gallate (EGCG), but not to the other polyphenols, were observed. In G6PD-deficient cells, GSH was reduced by 43.3% (EGC at 0.05 mg/mL) and 33.3% (EGCG at 0.5 mg/mL), compared with pre-challenged levels. The concentration of methaemoglobin was increased significantly when these cells were challenged with tea extracts, and EGC. Plasma haemoglobin levels were higher in G6PD-deficient samples after exposure to tea extracts, EGCG, EGC and gallic acid, compared with those in normal blood.
Ko Chun Kay.
"August 2006."
Advisers: Tai Fai Fok; Kwai Har Karen Li.
Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1577.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2006.
Includes bibliographical references (p. xxii-xliii).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts in English and Chinese.
School code: 1307.