by Tong Yuen Kwan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 124-141). / Abstract also in Chinese. / acknowledgements --- p.i / Abstract (English/Chinese) --- p.ii / contents --- p.vi / list of tables --- p.viii / ost of figures --- p.x / Chapter I. --- introduction --- p.1 / Chapter I.1. --- Tumors of the Central Nervous System --- p.1 / Chapter I.2. --- Histopathological Classification of Human Glial Tumors --- p.3 / Chapter I.2.1. --- Histopathology of Astrocytic Gliomas --- p.3 / Chapter I.2.1.1. --- Diffuse Astrocytomas --- p.3 / Chapter I.2.1.2. --- Others --- p.6 / Chapter I.2.2. --- Histopathology of Non-Astrocytic Gliomas --- p.6 / Chapter I.2.2.1. --- Oligodendroglial Tumors --- p.6 / Chapter I.2.2.2. --- Ependymal Tumors --- p.9 / Chapter I.3. --- Tumor Suppressor Genes --- p.14 / Chapter I.3.1. --- p53 --- p.14 / Chapter I.3.1.1. --- Historical Perspectives --- p.14 / Chapter I.3.1.2. --- Structure of p53 Gene and Protein --- p.15 / Chapter I.3.1.3. --- Functions of Wild-Type p53 Protein --- p.18 / Chapter I.3.1.4. --- Regulation and Modulation of the Functions of p53 --- p.21 / Chapter I.3.1.5. --- Mechnism of p53 Inactivation --- p.23 / Chapter I.3.1.6. --- p53 Mutation Profiles in Human Tumors --- p.25 / Chapter I.3.2. --- Novel Genes --- p.28 / Chapter I.3.2.1. --- PTEN/MMAC1 --- p.28 / Chapter I.3.2.2. --- DMBT1 --- p.31 / Chapter I.4. --- Cytogenetic and Molecular Genetic Studies in Gliomas --- p.34 / Chapter I.4.1. --- Astrocytic Gliomas --- p.34 / Chapter I.4.2. --- Non-Astrocytic Gliomas --- p.39 / Chapter I.4.2.1. --- Oligodendroglial Tumors --- p.39 / Chapter I.4.2.2. --- Ependymal Tumors --- p.46 / Chapter II. --- objectives of study --- p.49 / Chapter III. --- materials and methods --- p.52 / Chapter III.l. --- Patients and Materials --- p.52 / Chapter III.2. --- Collection of Samples --- p.57 / Chapter III.3. --- DNA Extraction --- p.58 / Chapter III.3.1. --- Extraction of Genomic DNA from Formalin-Fixed Paraffin Embedded Tissues --- p.58 / Chapter III.3.2. --- Extraction of Genomic DNA from Blood --- p.60 / Chapter III.4. --- Loss of Heterozygosity (LOH) Analysis on Chromosome 10q --- p.61 / Chapter III.4.1. --- Microsatellite Markers --- p.62 / Chapter III.4.2. --- Amplification of Target Sequences by PCR --- p.63 / Chapter III.4.3. --- Denaturing Polyaerylamide Gel Electrophoresis --- p.64 / Chapter III.4.4. --- Detection of Loss of Heterozygosity (LOH) --- p.64 / Chapter III.5. --- Mutational Analysis of p53 and PTEN/MMAC1 --- p.66 / Chapter III.5.1. --- Polymerase Chain Reaction-Single Strand Conformation Polymorphism (PCR-SSCP) Analysis --- p.66 / Chapter III.5.1.1. --- PCR Primers --- p.66 / Chapter III.5.1.2. --- PCR Amplification of Target Sequences --- p.68 / Chapter III.5.1.3. --- Non-denaturing Polyacrylamide Gel Electrophoresis --- p.71 / Chapter III.5.2. --- Direct DNA Sequencing Analysis --- p.72 / Chapter III.5.2.1. --- Cycle Sequencing --- p.72 / Chapter III.5.2.2. --- Denaturing Gel Electrophoresis --- p.73 / Chapter III.6. --- Differential PCR for Detection of MDM2 Amplification --- p.74 / Chapter III.6.1. --- DNA Amplification by PCR --- p.74 / Chapter III.6.2. --- Polyacrylamide Gel Electrophoresis --- p.75 / Chapter III.6.3. --- Detection of Gene Amplification --- p.75 / Chapter IV. --- Results --- p.77 / Chapter IV.1. --- LOH Analysis of Chromosome l0q --- p.77 / Chapter IV.2. --- Mutational Analysis ofp53 and PTEN/MMAC1 --- p.92 / Chapter IV.3. --- Differential PCR Analysis of MDM2 Amplification --- p.103 / Chapter V. --- discussion --- p.109 / Chapter V.l. --- p53 Gene Inactivation Studies --- p.110 / Chapter V.2. --- Molecular Genetic Studies on Chromosome l0q --- p.113 / Chapter V.3. --- Microsatellite Instability in Non-Astrocytic Gliomas --- p.117 / Chapter V.4. --- Significance of This Study --- p.118 / Chapter V.5. --- Limitations of This Study --- p.119 / Chapter V.6. --- Future Studies --- p.122 / Chapter VI. --- REFERENCES --- p.124

Ng Yeung Lam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 180-209). / Abstracts in English and Chinese. / acknowledgements --- p.i / abstract --- p.ii / abstract in chinese --- p.vi / table of contents --- p.ix / list of tables --- p.xiii / list of figures --- p.xi v / list of abbreviations --- p.xvi / Chapter 1 --- chapter1 introduction and literature review --- p.1 / Chapter 1.1 --- Introduction of brain tumors --- p.1 / Chapter 1.2 --- Oligodendroglial tumors (OTs) --- p.3 / Chapter 1.2.1 --- Oligodendroglioma (OD) and anaplastic oligodendroglioma (AOD) --- p.3 / Chapter 1.2.1.1 --- WHO's definition and grading --- p.3 / Chapter 1.2.1.2 --- "Incidence, age, sex distribution, tumor location and survival rate" --- p.3 / Chapter 1.2.1.3 --- Clinical presentation --- p.4 / Chapter 1.2.1.4 --- Macroscopy and histopathology --- p.4 / Chapter 1.2.1.5 --- Immunohistochemistry --- p.5 / Chapter 1.2.1.6 --- Treatment --- p.6 / Chapter 1.2.2 --- Oligoastrocytoma (OA) and anaplastic oligoastrocytoma (AOA) --- p.11 / Chapter 1.2.2.1 --- WHO's definition and grading --- p.11 / Chapter 1.2.2.2 --- "Incidence, age, sex distribution, tumor location and survival rate" --- p.12 / Chapter 1.2.2.3 --- Clinical features --- p.12 / Chapter 1.2.2.4 --- Macroscopy and histopathology --- p.12 / Chapter 1.3 --- Overview of Genetic and Epigenetic Aberrations of OTs --- p.14 / Chapter 1.3.1 --- Chromosomal and genetic aberrations in OTs --- p.14 / Chapter 1.3.2 --- Candidate regions and genes on 1 p --- p.15 / Chapter 1.3.3 --- Candidate regions and genes on 19q --- p.20 / Chapter 1.3.4 --- Other aberrations in WHO grade II OTs --- p.24 / Chapter 1.3.5 --- Progression-associated aberrations in ODs --- p.25 / Chapter 1.3.6 --- Chromosomal and genetic aberrations in OAs --- p.29 / Chapter 1.4 --- Correlation of genetic alterations with response to therapy and survival --- p.31 / Chapter 1.4.1 --- Response to PCV chemotherapy correlates with lp and combined lp/19q status in patients with AODs --- p.31 / Chapter 1.4.2 --- Survival of patients with AODs correlates with lp/19q status --- p.32 / Chapter 1.4.3 --- WHO grade II ODs behavior and lp/19q status --- p.32 / Chapter 1.4.4 --- Response to other therapies (temozolomide and radiotherapy) and lp/19q status in patients with ODs --- p.33 / Chapter 1.4.5 --- lp and 19q loss in OAs and diffuse astrocytomas --- p.34 / Chapter 1.5 --- Microarray-based expression profiling of OTs --- p.35 / Chapter 1.6 --- Description of p73 protein --- p.37 / Chapter 1.6.1 --- Introduction of p73 --- p.37 / Chapter 1.6.2 --- p73: gene structure and splicing variants --- p.37 / Chapter 1.6.3 --- Signaling in p73 --- p.40 / Chapter 1.6.4 --- Regulation ofp73 protein stability and transcriptional activity --- p.43 / Chapter 1.6.4.1 --- Regulation by DNA damage --- p.43 / Chapter 1.6.4.2 --- Regulation by oncogenes --- p.44 / Chapter 1.6.4.3 --- Interaction with viral proteins --- p.44 / Chapter 1.6.5 --- Role of p73 in the nervous system --- p.45 / Chapter 1.6.6 --- p73 in cancer --- p.45 / Chapter 1.6.6.1 --- p73 knockout mice --- p.45 / Chapter 1.6.6.2 --- Alteration of p73 expression in human cancers --- p.46 / Chapter 1.6.7 --- p73 and chemosensitivity --- p.50 / Chapter CHAPTER2 --- AIMS OF STUDY --- p.51 / Chapter CHAPTER3 --- MATERIALS AND METHODS --- p.53 / Chapter 3.1 --- Tumor and blood samples --- p.53 / Chapter 3.2 --- Cell culture --- p.53 / Chapter 3.3 --- DNA extraction from frozen tissues and blood samples --- p.54 / Chapter 3.4 --- Detection of allelic loss of chromosome lp --- p.58 / Chapter 3.4.1 --- LOH analysis --- p.58 / Chapter 3.4.2 --- Fluorescence in situ Hybridization (FISH) analysis on Paraffin and Frozen Sections --- p.60 / Chapter 3.6 --- DNA sequencing analysis --- p.62 / Chapter 3.7 --- Analysis of Methylation --- p.63 / Chapter 3.7.1 --- Bisulfite sequencing --- p.63 / Chapter 3.7.2 --- Methylation-specific polymerase chain reaction (MSP) --- p.66 / Chapter 3.8 --- Northern Blot analysis --- p.68 / Chapter 3.9 --- RNA isolation and cDNA preparation --- p.70 / Chapter 3.10 --- Laser microdissection and RNA extraction from microdissected tumor cells --- p.71 / Chapter 3.10.1 --- Conventional RT-PCR --- p.71 / Chapter 3.11 --- Primer design for TP73 and its isoforms --- p.74 / Chapter 3.12 --- Real-time RT-PCR --- p.77 / Chapter 3.12.1 --- Real-time RT-PCR for TP73 and its isoforms --- p.78 / Chapter 3.12.2 --- Real-time RT-PCR for KIAA0495 --- p.79 / Chapter 3.13 --- Statistical analyses --- p.81 / Chapter CHAPTER4 --- RESULTS --- p.82 / Chapter 4.1 --- Genes annotated in the minimally deleted regions --- p.82 / Chapter 4.2 --- Expression analyses of TP73 and its isoforms in ODs by quantitative real-time RT-PCR --- p.85 / Chapter 4.3 --- Methylation analysis of TP73 in ODs by methylation sensitive PCR (MSP) --- p.97 / Chapter 4.4 --- A rapid screen of candidate genes for aberrant expression in microdissected tumors --- p.100 / Chapter 4.5 --- Quantitative real-time RT-PCR of KIAA0495 gene --- p.103 / Chapter 4.6 --- Mutation analysis of KIAA0495 gene --- p.110 / Chapter 4.7 --- Methylation analysis of KIAA0495 in ODs by bisulfite sequencing…… --- p.112 / Chapter 4.8 --- Detection of allelic loss of lp by LOH analysis and interphase FISH --- p.121 / Chapter 4.9 --- Two-hit inactivation of KIAA0495 gene in ODs --- p.126 / Chapter 4.10 --- Tissue distribution of KIAA0495 gene --- p.130 / Chapter 4.11 --- Bioinformatics of KIAA0495 --- p.133 / Chapter CHAPTER5 --- DISCUSSION --- p.146 / Chapter 5.1 --- Expression analysis of TP73 and its isoforms in ODs by isoform-specific RT-PCR --- p.148 / Chapter 5.2 --- Methylation status ofTP73 in ODs --- p.153 / Chapter 5.3 --- A rapid screening of candidate genes for aberrant expressionin microdissected tumors --- p.156 / Chapter 5.4 --- Expression pattern of KIAA0495 mRNA in a large cohort of ODs --- p.157 / Chapter 5.5 --- No somatic mutation in coding region of KIAA0495 --- p.158 / Chapter 5.6 --- Methylation status of putative promoter region of KIAA0495 in ODs --- p.159 / Chapter 5.7 --- Status of chromosome lp in ODs --- p.161 / Chapter 5.8 --- Two-hit inactivation of KIAA0495 gene in ODs by promoter hypermethylation and allelic loss of lp --- p.162 / Chapter 5.9 --- Evaluation of expression of KIAA0495 gene as a marker for the response to chemotherapy and prognostic marker in patients with OTs --- p.164 / Chapter 5.10 --- Tissue distribution of KIAA0495 --- p.166 / Chapter 5.11 --- "KIAA0495 cDNA sequence, protein sequence and potential functional features" --- p.167 / Chapter 5.12 --- Candidate tumor suppressor genes on lp in other type of tumors with loss of lp --- p.171 / Chapter CHAPTER6 --- CONCLUSIONS --- p.174 / Chapter CHAPTER7 --- FUTURE STUDIES --- p.177 / Chapter CHAPTER8 --- REFERENCES --- p.180

<p>Genetic variation is a natural occurrence in the genome that contributes to the phenotypic differences observed between individuals as well as the phenotypic outcomes of various diseases, including infectious disease and cancer. Single nucleotide polymorphisms (SNPs) have been identified as genetic factors influencing host susceptibility to infectious disease while the study of copy number variation (CNV) in various cancers has led to the identification of causal genetic factors influencing tumor formation and severity. In this work, we evaluated the association between genomic variation and disease phenotypes to identify SNPs contributing to host susceptibility in Staphylococcus aureus (<italic>S. aureus</italic>) infection and to characterize a nervous system brain tumor, known as oligodendroglioma (OD), using the CNV observed in tumors with varying degree of malignancy.</p><p>Using SNP data, we utilized a computational approach, known as in silico haplotype mapping (ISHM), to identify genomic regions significantly associated with susceptibility to <italic>S. aureus</italic> infection in inbred mouse strains. We conducted ISHM on four phenotypes collected from <italic>S. aureus</italic> infected mice and identified genes contained in the significant regions, which were considered to be potential candidate genes. Gene expression studies were then conducted on inbred mice considered to be resistant or susceptible to <italic>S. aureus</italic> infection to identify genes differentially expressed between the two groups, which provided biological validation of the genes identified in significant ISHM regions. Genes identified by both analyses were considered our top priority genes and known biological information about the genes was used to determine their function roles in susceptibility to <italic>S. aureus</italic> infection.</p><p> We then evaluated CNV in subtypes of ODs to characterize the tumors by their genomic aberrations. We conducted array-based comparative genomic hybridization (CGH) on 74 ODs to generate genomic profiles that were classified by tumor grade, providing insight about the genomic changes that typically occur in patients with OD ranging from the less to more severe tumor types. Additionally, smaller genomic intervals with substantial copy number differences between normal and OD DNA samples, known as minimal critical regions (MCRs), were identified among the tumors. The genomic regions with copy number changes were interrogated for genes and assessed for their biological roles in the tumors' phenotype and formation. This information was used to assess the validity of using genomic variation in these tumors to further classify these tumors in addition to standard classification techniques. </p><p> The studies described in this project demonstrate the utility of using genetic variation to study disease phenotypes and applying computational and experimental techniques to identify the underlying genetic factors contributing to disease pathogenesis. Moreover, the continued development of similar approaches could aid in the development of new diagnostic procedures as well as novel therapeutics for the generation of more personalized treatments. The genomic regions with copy number changes were interrogated for genes and assessed for their biological roles in the tumors' phenotype and formation. This information was used to assess the validity of using genomic variation in these tumors to further classify these tumors in addition to standard classification techniques.</p><p> The studies described in this project demonstrate the utility of using genetic variation to study disease phenotypes and applying computational and experimental techniques to identify the underlying genetic factors contributing to disease pathogenesis. Moreover, the continued development of similar approaches could aid in the development of new diagnostic procedures as well as novel therapeutics for the generation of more personalized treatments.</p> / Dissertation

Background: Gliomas are neuroepithelial tumours classified by cell type and grade. In adults, low-grade gliomas are comprised mainly of astrocytomas and oligodendrogliomas grade II. The aim was to non-invasively characterise suspected low-grade gliomas through use of 11C-methionine-PET and physiological MRI in order to facilitate treatment decisions. Materials and methods: Patients with suspected low-grade glioma were prospectively and consecutively included after referral to the Neurosurgical Department, Uppsala University Hospital, between February 2010 and February 2014. All patients underwent morphological MRI, perfusion MRI, diffusion MRI and 11C-methionine PET. The institutional review board approved the study, and written informed consent was obtained prior to participation from each patient. Results: 11C-methionine PET hot spot regions corresponded spatially with regions of maximum relative cerebral blood volume in dynamic susceptibility contrast (DSC) perfusion MRI. The skewness of the transfer constantin dynamic contrast-enhanced (DCE) perfusion MRI, and the standard deviation of relative cerebral blood flow in DSC perfusion MRI could most efficiently discriminate between glioma grades II and III. In diffusion MRI, tumour fractional anisotropy differed between suspected low-grade gliomas of different neuropathological types. Quantitative diffusion tensor tractography was applicable for the evaluation of tract segment infiltration. Conclusion: PET and physiological MRI are able to characterise low-grade gliomas and are promising tools for guiding therapy and clinical decisions before neuropathological diagnosis has been obtained.

Les gliomes diffus de bas grades sont des tumeurs qui affectent des régions fonctionnelles du cerveau chez des jeunes patients. Malgré leur faible taux de prolifération ces tumeurs peuvent dégénérer en des tumeurs plus agressives après leurs exérèses. Le gène IDH1 est très fréquemment muté dans les DLGG. Cette mutation confère à l’enzyme isocitratedeshydrogénase (IDH1) la propriété de produire du 2-OH-glutarate (2-HG) au lieu de l’α-cétoglutarate (α-KG). L’oncométabolite 2HG rentre alors en compétition avec l’α-KG pour les enzymes de déméthylation conduisant à une hyperméthylation de l’ADN et de l’histone H3 concourant à un blocage de la différenciation cellulaire. Mon projet de thèse consiste à la caractérisation des cellules tumorales et la compréhension des voies de signalisation impliquées dans la progression tumorale ainsi que l’identité du microenvironnement tumoral. Les récepteurs tyrosine kinase, PDGFRα et EGFR, sont abondamment exprimés par les cellules tumorales mais ne sont pas activés. En revanche, une forte phosphorylation de la protéine Erk p42/44 a été détectée dans les tumeurs. Cette phosphorylation a une double origine : les cellules tumorales et leur environnement. L’utilisation d’une série de marqueurs m’a permis de mieux définir l’état de différenciation des cellules tumorales et de mettre en évidence une préférence pour l’expression de Sox8 dans les oligodendrogliomes tandis que Sox9 est prédominant dans les astrocytomes. Dans une seconde partie, j’ai mis au point des méthodes pour la culture des gliomes diffus de bas grade et isolé cinq lignées de gliomes portant la mutation récurente IDH1 R132H. Récemment, la société Agios a identifié des inhibiteurs très spécifiques (notamment l’AGI-5198) de l’enzyme mutée IDH1 qui, utilisés dans un modèle de gliome murin, provoquent une déméthylation des histones H3K9me3 associées à une augmentation de l’expression de gènes de différenciation ainsi qu’à une réduction de la masse tumorale. A contrario, j’ai montré que l’AGI-5198 augmente la croissance cellulaire sur les lignée de patients, modifie la migration cellulaire ainsi que différentes voies de signalisation.Ces travaux apportent un nouvel éclairage sur le phénotype des cellules tumorales, leur diversité et les mécanismes moléculaires régissant leur prolifération. / Low grade gliomas are low proliferating tumors affecting functional regions of young patients. In most cases, they tend to transform into a more malignant state following surgery. These tumors carry a key mutation in isocitrate dehydrogenase (70-80% of DLGG). Gliomas with IDH1 mutation have improved prognosis compared togliomaswith wild type IDH1. IDH1 protein acquires the ability to convert α-Ketoglutarate (α-KG) to 2-OH-glutarate (2-HG). The new onco-metabolite can interfere with the normal function of α-KG, leading to a general hypermethylation of the genome, thus inducing a blockage of the cellular differentiation. Very good reviews on the molecular mechanisms underlying high grade glioma invasion already exist but little is known about the cellular and molecular mechanisms in diffuse low grade gliomas. To that end, I characterized the profile of IDH1 mutated cells in the different types of DLGG. I have demonstrated that the tyrosine kinase, PDGFRα and EGFR receptors are abundantly expressed by tumor cells eventhough they are not activated. In contrast, a strong phosphorylation of Erk p42 / 44 proteins was detected in these tumors. This phosphorylation has a dual origin: tumor cells and their environment. The use of a series of markers allowed me to better define the state of differentiation of cancerous cells and to demonstrate a preferential expression of Sox8 in oligodendrogliomas while Sox9 is predominant in astrocytomas. In a second time, I have developed a method for the culture of low-grade diffuse gliomas and isolated five cell lines carrying the recurrent mutation IDH1 R132H. Recently Agios has identified very specific inhibitors (particularly AGI-5198) of the mutated IDH1 enzyme which, used in a murine glioma model, contributed to the demethylation of H3K9me3 histones with an increased expression of differentiation related genes as well as a reduction of the tumor mass. On the contrary, I have shown that AGI-5198 increases cell growth of patient cell lines, modifies the cellular migration and various signaling pathways.These studies shed new light on the phenotype of tumor cells, their diversity and The molecular mechanisms governing their proliferation.

We carried out a population-based study on low-grade diffuse gliomas in the Canton of Zurich, Switzerland (population 1.16 million). From 1980 to 1994, 987 astrocytic and oligodendroglial tumors were diagnosed, of which 122 (12.4%) were low-grade (WHO grade II). The incidence rates adjusted to the World Standard Population, per million population per year, were 2.28 for low-grade diffuse astrocytomas, 0.89 for oligoastrocytomas, and 2.45 for oligodendrogliomas. The survival rate (mean follow-up 7.5±4.8 years) was highest for patients with oligodendroglioma (78% at 5 years, 51% at 10 years), followed by those with oligoastrocytoma (70% at 5 years, 49% at 10 years) and fibrillary astrocytoma (65% at 5 years, 31% at 10 years). Survival of patients with gemistocytic astrocytoma was poor, with survival rates of 16% at 5 years and 0% at 10 years. Younger patients (<50 years) survived significantly longer than older patients (>50 years; P=0.013). DNA sequencing, performed in 84% of cases, revealed that TP53 mutations were most frequent in gemistocytic astrocytomas (88%), followed by fibrillary astrocytomas (53%) and oligoastrocytomas (44%), but were infrequent (13%) in oligodendrogliomas. The presence of TP53 mutations was associated with shorter survival of patients with low-grade diffuse gliomas (log-rank test; P=0.047), but when each histological type was analyzed separately, an association was observed only for oligoastrocytoma (P=0.05). Loss on 1p and 19q were assessed by quantitative microsatellite analysis in 67% of cases. These alterations were frequent in oligodendrogliomas (1p, 57%; 19q, 69%), less common in oligoastrocytomas (lp, 27%; 19q, 45%), rare in fibrillary astrocytomas (lp, 7%; 19q, 7%), and absent in gemistocytic astrocytomas. None of these alterations were predictive of survival. These results establish the frequency of key genetic alterations in low-grade diffuse gliomas at a population-based level. Multi-variate Cox's regression analysis indicates that only age and histological type, but not genetic alterations, are significant predictive factors.

La v-ATPase est une pompe à protons. Elle permet l’acidification d’organelles, ce qui est indispensable à de nombreux processus cellulaires. Cette enzyme est composée de 14 sous-unités différentes, organisées en deux domaines, le domaine catalytique V1 et le domaine membranaire V0. La sous-unité a du domaine V0 est essentielle au transport des protons. Il en existe 4 isoformes (a1 à a4) et des variants d’épissage (a1-I à a1-IV pour a1) permettant à la v-ATPase d’être adressée vers différents compartiments et donc d’être impliquée dans différents processus. Deux projets visant à étudier cette sous-unité ont été réalisés.En plus de son rôle dans le transport des protons, il a été montré que le domaine V0 de la v-ATPase est impliqué dans des évènements de trafic membranaire, tel que l’exocytose de vésicules de sécrétion. Ce rôle semble nécessiter des interactions avec les protéines SNAREs. J’ai montré, pendant la première partie de ma thèse, que les sous-unités flag-a1-I et flag-a1-IV sont toutes deux adressées aux granules de sécrétion de cellules neurosécrétrices et interagissent avec les protéines SNAREs VAMP2 et syntaxine-1. De façon intéressante la syntaxine-1 semble interagir préférentiellement avec la sous-unité a1-I qui dans les neurones est l’isoforme adressée aux terminaisons nerveuses. Les sous-unités a1-IV ne diffèrent d’a1-I que par l’ajout de 7 acides aminés dans sa moitié N-terminale. Le domaine d’interaction de la sous-unité a avec la syntaxine-1 semble donc être localisé dans cette région.Dans la deuxième partie de ma thèse, j’ai mis en évidence et étudié l’expression de la sous-unité rénale a4 dans des gliomes humains. Ces tumeurs sont les tumeurs cérébrales les plus fréquentes et sont en général associées à un mauvais pronostic. L’OMS distingue, en fonction de paramètres histologiques, les astrocytomes (de grade I à IV), les oligodendrogliomes et les gliomes mixtes (chacun de grade II ou III). Cette classification est controversée, notamment à cause de son manque de reproductibilité, et la prise en compte de marqueurs moléculaires semble s’imposer comme une solution pour la renforcer.J’ai quantifié par RT-PCR quantitative l’expression du gène ATP6V0A4 (codant la sous-unité a4) dans 188 prélèvements de gliomes humains. Nous avons ainsi montré que l’expression de la sous-unité a4 peut être utilisée comme marqueur diagnostique des oligodendrogliomes anaplasiques (35 % l’expriment). Dans un prélèvement, la présence de la codélétion 1p/19q et l’expression de a4, tout deux marqueurs indépendants des oligodendrogliomes, permettra le renforcement du diagnostique oligodendrogliome anaplasique. De plus a4 est fréquemment exprimée par les astrocytomes pilocytiques (70%), où elle est associée à la duplication en tandem de la région chromosomique 7q34 située à proximité directe du gène ATP6V0A4. Enfin une observation prometteuse est que l’expression de a4 pourrait être un marqueur de mauvais pronostic pour les patients atteints d’oligodendrogliome anaplasique ne présentant pas la co-délétion 1p/19q, observation qui devra être confirmée sur une plus grande cohorte de patients. / Vacuolar type H+-ATPase is a proton pump, which acidifies numerous organelles, crucial for many cellular processes. This enzyme is composed of 14 different subunits organized in two domains, a catalytic V1 domain and a V0 membrane domain. The a-subunit of V0 is essential for proton transport. There are 4 isoforms of a (a1 to a4) and splicing variants (a1-I to a1-IV for the a1 subunit). v-ATPases containing different a-subunit isoforms are localized in different compartments allowing v-ATPase to participate in different processes. The a-subunits were studied in this work in two distinct projects.Besides its role in proton pumping, V0 domain of v-ATPase is implicated in organelles trafficking events, like vesicles exocytosis. This role seems to require interactions of V0 with SNARE proteins. During my thesis work, I showed that flag-a1-I and flag-a1-IV are both targeted to secretion granules in PC12 neurosecretory cells. These subunits interact with the SNARE proteins VAMP2 and syntaxin-1. Interestingly, syntaxin-1 seems to preferentially interact with the a1-I subunit, isoform which in neurons is sorted to nerve terminals. The only difference between a1-I and a1-IV subunits is the addition of 7 amino acids in the N-terminal half of a1-IV. So syntaxin-1 probably interacts with a1-I at this location. In a second project, I studied the expression of the renal a4-subunit in human gliomas. These tumors are the most frequent brain tumors and are generally associated with a poor prognosis. Based on histological parameters,WHO distinguishes, astrocytomas (grade I to IV), oligodendrogliomas and oligoastrogliomas (each of grade II or III). This classification suffers of a lack of reproducibility, which could be overcome by the identification of specific molecular markers.In the present work, by real time quantitative PCR, ATP6V0A4 gene (encoding the renal a4) expression was quantified in 188 human glioma biopsies. We established a4 expression as a new marker of grade III oligodendrogliomas (35 % express it), independent of the 1p/19q codeletion, an established marker of oligodendrogliomas. Moreover, a4 is expressed in 70% of pilocytic astrocytomas, in which it is associated with the tandem duplication of 7q34, localized at direct proximity of the ATP6V0A4 gene. Of promising interest is the observation that a4 expression could be considered as a bad prognostic marker for patients with 1p/19q non-deleted oligodendrogliomas, an observation that should be confirmed on larger cohorts of patients.