Les maladies rétiniennes héréditaires représentent un groupe de pathologie hétérogène sur le plan phénotypique et génétique. Elles sont dues à une dysfonction ou une dégénérescence de la neurorétine ou de l’épithélium pigmentaire rétinien. Elles peuvent être présente de manière isolée ou être associée à des atteintes extraoculaires dans les formes syndromiques. Le travail de thèse porte sur l’identification moléculaire de gènes responsables de formes rares de pathologie rétinienne syndromique incluant les ciliopathies dont le syndrome de Bardet-Biedl, caractérisé notamment par une dégénérescence rétinienne constante, et les microcéphalies associées à une choriorétinopathie. Par une approche de séquençage exomique, nous avons pu identifier trois nouveaux gènes impliqués dans ces pathologies rétiniennes syndromiques et confirmer l’implication d’un gène dans le syndrome de Bardet-Biedl. L’analyse des phénotypes rétiniens d’une cohorte de patients présentant un syndrome de Bardet-Biedl a permis la description d’un phénotype atypique avec atteinte prédominante des cônes. / Inherited retinal diseases (IRDs) represent a clinically and genetically heterogeneous group of rare pathologies. These disorders result of a dysfunction or a degeneration of the photoreceptors or the retinal pigment epithelium. IRDs can be subdivided in isolated forms, and syndromic forms that involve non–ocular features. This work deals with the molecular identification of genes implicated in rare forms of syndromic retinal diseases, including the ciliopathies with the Bardet-Biedl syndrome (BBS), characterized by a constant retinal degeneration, and the microcephaly associated with chorioretinopathy.Using an exomic sequencing approach, we have identified three new genes involved in these rare syndromic retinal diseases and confirmed the implication of a gene in Bardet-Biedl syndrome. The analysis of the retinal phenotypes of a BBS patients’ cohort allowed the description of an atypical retinal phenotype with predominantly cone dysfunction.

Primary cilia are evolutionarily conserved organelles required in a number of signalling pathways influencing the development and behaviour of a diverse range of organisms. More recently, studies into a new class of human diseases known as ciliopathies have helped to shed light on the critical role of this once-ignored signalling centre. Bardet-Biedl syndrome (BBS) proteins localize to the primary cilium and participate in cilium biogenesis and function. BBS is a pleiotropic human disorder with variable severity that is suitable as a disease model for investigating the pathogenesis of a number of common ciliopathy features such as photoreceptor degeneration, renal cysts, and obesity. The C. elegans genome encodes a number of BBS proteins which undergo intraflagellar transport (IFT) at the primary cilium. Given the conservation between C. elegans and human BBS proteins, I hypothesize the existence of unidentified conserved genetic pathways related to the functions of these proteins. Using C. elegans, I characterize novel features of bbs mutants while identifying sources of genomic variation that may elucidate the variability of human BBS features. I show that C. elegans bbs mutants exhibit smaller body size, delayed development, and decreased exploration behaviour. Moreover, I identify a role for the soluble guanylate cyclases GCY-35/GCY-36 in modifying these bbs phenotypes. I conclude that BBS proteins non-cell autonomously influence a set of body cavity neurons in which GCY-35/GCY-36 function genetically upstream of a cGMP-dependent protein kinase (PKG), EGL-4, to control body size. Furthermore, the role of GCY-35/GCY-36 is unique amongst a large number of guanylate cyclases and BBS proteins may influence body size via an IFT-independent function. I explore the biological functions of EGL-4 and conclude that it may regulate body size through multiple cellular mechanisms. I also examine potential candidate genes related to cGMP production and turnover, confirming that additional cGMP-related factors can influence body size although not necessarily in body cavity neurons. In conclusion, I propose a model where BBS-expressing sensory neurons influence body size and development through cGMP-PKG signalling in body cavity neurons while functioning in parallel with additional sensory neurons (possibly BBS-independent) that use similar cGMP-PKG signalling dynamics.

Primary cilia are evolutionarily conserved organelles required in a number of signalling pathways influencing the development and behaviour of a diverse range of organisms. More recently, studies into a new class of human diseases known as ciliopathies have helped to shed light on the critical role of this once-ignored signalling centre. Bardet-Biedl syndrome (BBS) proteins localize to the primary cilium and participate in cilium biogenesis and function. BBS is a pleiotropic human disorder with variable severity that is suitable as a disease model for investigating the pathogenesis of a number of common ciliopathy features such as photoreceptor degeneration, renal cysts, and obesity. The C. elegans genome encodes a number of BBS proteins which undergo intraflagellar transport (IFT) at the primary cilium. Given the conservation between C. elegans and human BBS proteins, I hypothesize the existence of unidentified conserved genetic pathways related to the functions of these proteins. Using C. elegans, I characterize novel features of bbs mutants while identifying sources of genomic variation that may elucidate the variability of human BBS features. I show that C. elegans bbs mutants exhibit smaller body size, delayed development, and decreased exploration behaviour. Moreover, I identify a role for the soluble guanylate cyclases GCY-35/GCY-36 in modifying these bbs phenotypes. I conclude that BBS proteins non-cell autonomously influence a set of body cavity neurons in which GCY-35/GCY-36 function genetically upstream of a cGMP-dependent protein kinase (PKG), EGL-4, to control body size. Furthermore, the role of GCY-35/GCY-36 is unique amongst a large number of guanylate cyclases and BBS proteins may influence body size via an IFT-independent function. I explore the biological functions of EGL-4 and conclude that it may regulate body size through multiple cellular mechanisms. I also examine potential candidate genes related to cGMP production and turnover, confirming that additional cGMP-related factors can influence body size although not necessarily in body cavity neurons. In conclusion, I propose a model where BBS-expressing sensory neurons influence body size and development through cGMP-PKG signalling in body cavity neurons while functioning in parallel with additional sensory neurons (possibly BBS-independent) that use similar cGMP-PKG signalling dynamics.