Role of the new splicing isoform of gene von Hippel-Lindau in the development of Erythrocytosis and hereditary renal cancer ; Rôle de la nouvelle isoforme d’épissage du gène von Hippel-Lindau dans la survenue d’érythrocytoses et de cancers du rein héréditaires

The von Hippel-Lindau protein (VHL), encoded by the VHL gene that contains three exons, is a key factor of the hypoxia pathway. The main player of this pathway is the hypoxia inducible factor (HIF). In presence of oxygen, HIF is recognized by VHL, then ubiquitinylated and degradated by the proteasome. In absence of oxygen, HIF is stabilized and induces the expression of hundreds of genes involved in angiogenesis (VEGF), proliferation (TGF), metabolism (GLUT1) and erythropoiesis (EPO). When VHL is mutated, HIF is not degraded and induces the overexpression of these genes which can led to the formation of tumors via the hypervascularisation and the hyperproliferation of the cells or to an excessive erythropoiesis. Two pathologies are associated with mutations in VHL. The erythrocytosis is characterized by an elevated level of red blood cells and EPO serum level associated with homozygous or compound heterozygous mutations of VHL. The VHL disease is characterized by the development of hypervascularized tumors (hemangioblastomas of the central nervous system or of the retina, pheochromocytomas, paragangliomas or renal cancers) associated with heterozygous mutations of VHL and a loss of heterozygosity in tumors. It has been described that VHL mutations followed a continuum model of tumor suppression: the more severe is the loss of pVHL function the more severe is the developed pathology. However, some patients presented with a clinical aspect typical of VHL mutations but without any identified mutation (VHL disease) or with only heterozygous mutation (erythrocytosis). The molecular mechanisms at the origin of these phenotypes are not yet understood, the aim of my thesis was to study complex mutations of VHL, namely mutations that impact VHL splicing. A comprehensive study has been performed on twelve families: segregation study, phylogenetic analysis, minigene experiments and sequencing of RNA from tumors or lymphoblastoid cell lines of patients, measurement of the expression of mRNA and proteins, functional study of ...