Human chromosome 15q11-q14 is characterized by genome instability, allele-specificmethylation and gene expression complexity. Several large segmental duplications relocated at this chromosome region and are known to mediate genomic rearrangements leading to genomic disorders. In addition to Praderj-Willi and Angel man syndromes, complex disorders like autism, schizophrenia and epilepsy are found to be associated with rearrangements of ISqII-qH. The understanding of the genomic organization of the 15q11-q14 regions is the first step towards the detailed analysis of the link between variants at the genomic or molecular level and specific disorders. All versions of the draft sequence of this region are still very preliminary and the understanding of its genomic organization is hampered by the large number of segmental duplications that it contains, the complexity of the orientation of the different copies of the segmental duplications, and the variability that exists in the general population and in parents of patients that suffer from disorders affecting this region. Complete supplicant map of 15q11-q14 has not yet been developed and the major breakpoints of rearrangements have not yet been characterized at a precise molecular level. One of the major goals of this project is to further study the detailed segmental duplications organization of 15q11-q14 and to detect the molecular mechanisms that predispose to their genomic rearrangements. The proposed project also aims to identify the breakpoints of rearrangements in patients with autism that carry either deletions or duplications of 15q11-q14. In these patients, gene dosage effect and/or genes with disrupted structure is likely tube a direct cause of disease. Analysis of molecularly defined rearranged segments will identify such genes and their role in disease.