Molecular and patho-physiological basis of syndromes with developmental anomalies and intellectual disability ; Bases moléculaires et physiopathologiques de syndromes avec anomalies du développement et déficience intellectuelle

Intellectual disability (ID) corresponds to abnormal intellectual performances and adaptive functions, beginning in childhood. It is estimated that 2-3% of individuals develop a ID, which represents a significant medical challenge since people with ID are frequently in situations of social dependence. Overall, a critical involvement of genetic factors in this disease is suspected. To date, several hundreds of genes are known to be responsible for ID. The ID is particularly characterized by extreme clinical and genetic heterogeneity, that made it resistant to conventional genetic studies. However, it is classicaly separated between syndromic ID, which may be clinically recognizable due to associated congenital anomalies; isolated ID, without disctinctive features.The objective of this thesis was to identify the molecular basis of ID by combining both approaches. The first is based on the systematic identification of chromosomal microrearrangements using array-CGH in a group of patients with ID, to constitute a posteriori homogeneous cohorts. The second is based on a cohort of patients with a clinical diagnosis of Shprintzen-Goldberg syndrome studied by high throughput sequencing.This thesis defines new clinical entities by identifying recurrent genetic variations between different patients including the description of two microdeletionnal syndromes, and two candidate genes to the ID. In addition, we identified the molecular basis for the Shprintzen-Goldberg syndrome by highlighting a mutational hotspot in the SKI gene. ; La déficience intellectuelle (DI) correspond à un défaut des performances intellectuelles et des fonctions adaptatives, débutant dans l’enfance. Il est estimé que 2-3% des individus développeront une DI, ce qui représente un enjeu médical important puisque les personnes avec DI sont fréquemment en situation de dépendance sociale. Dans l’ensemble, on estime majoritaire l’implication de facteurs génétique dans cette pathologie. A ce jour, plusieurs centaines de gènes sont connus pour être ...