Identification of New Genes Causing Frontotemporal Lobar Degeneration by Whole Exome Sequencing and Characterization of the Associated Phenotypes

Background and justification of the research. In France, 6,000 to 8,000 patients are affected by frontotemporal lobar degeneration (FTLD). FTLD are degenerative dementias related to Alzheimer's disease, characterized by behavioural, language and cognitive disorders beginning in the sixth decade. The genetic forms of FTLD are frequent (30-50% of the patients), but the genes responsible for 30-40% of familial FTLD are still unknown. At present, no molecular diagnosis can be proposed for 30% of the FTLD families and patients, for which the responsible genes are still unknown. No presymptomatic testing can be proposed either to at-risk relatives in these families.

Objectives.

1. The principal objective of this proposal is to identify one or several genes responsible for FTLD.
2. The secondary objectives are to:

• evaluate the relative frequency of identified genes;
• describe the phenotypes associated with the mutations in these genes;
• establish phenotype-genotype correlations in order to improve the diagnostic procedures and strategies;
• develop new genetic diagnostic analyses in the near future.

Project The patients will be recruited in three hospitals (Paris Salpetriere, Limoges, Lille). These three centers are partners of a national clinico-genetic network of 20 french centers experts in FTLD/FTLD-ALS, coordinated by Dr. I Le Ber. The participants in this network have collaborated for the last 15 years, and have already recruited over 1,000 patients with FTLD. Sequencing of known genes in these families allowed the identification of 150 families with an autosomal dominant form of FTLD not associated with a known mutation. Through the network, we aim to recruit 400 new patients with FTLD during the 4 years of the project. This estimation is based on the annual recruitment of the network during the last two years.