Rett syndrome (RTT) is a genetic encephalopathy and the typical form is caused by mutations in the gene MECP2. It is a genetically heterogeneous pathology. CDKL5 and FOXG1 have been recently discovered being involved in other forms of RTT. However, at least 5% of typical forms and more other atypical forms are not linked to any of 3 genes known to be involved in the disease.

The purpose of this study is to identify new genes involved in molecular etiology of typical and atypical forms of RTT.

Search for pathogenic chromosomal imbalance through comparative genomic hybridization (aCGH) on DNA microarrays will be done in a group of patients having typical or atypical forms of RTT without known mutations in MECP2, CDKL5 et FOXG1B genes.

After imbalance confirmation by qPCR, the pathogenic potential of the segmental aneusomy will be assigned according to the interpretation of aCGH technique-dedicated DECEPHER, BACH and GVD databases. Analysis of parents will allow distinguishing between inherited polymorphic variants and potentially deleterious new imbalances.

In case of a new imbalance, a bioinformatics approach will look for candidate genes that will be possibly confirmed by classic mutation screening (sequencing and PCR) in all typical and atypical cases of RTT present in the cohort.

The identification of new genes involved in RTT will ameliorate the molecular diagnosis of the disease and genetic counseling for families. This project will allow progression in comprehension of physiopathological mechanisms of cerebral development abnormalities

Inclusion Criteria:

• Patients: RETT syndrome
• Patients: Female
• Parents: parent of a patients