Using Target Exome Sequencing to Identify the Genetic Mutation that causes a Rare Form of CMT

Charcot–Marie–Tooth (CMT) is a disease with many forms, produced by mutations in genes that cause defects in neuronal proteins resulting in the wasting away of muscle tissue, in the lower body. The objective of the Raskind Lab is to identify the genes that are responsible for a rare form of this genetic disease, using exome sequencing. It was predicted that exome sequencing would expose a mutation shared by the affected individuals in the family, thereby pinpointing the alteration responsible for this rare form of CMT. Two distant relatives were carefully chosen and their exomes were captured using array hybridization and sequenced by massively parallel techniques (“next-generation” sequencing”).  Single nucleotide polymorphisms (SNSPs) were genotyped by array technology and used for a linkage analysis to locate possible places on the chromosomes where the gene might reside. In those regions, the variants in the exomes (sequences that differ from the reference genome) were compared to dbSNP and exomes from people without this disease to filter out the nucleotide changes that are benign polymorphisms in the population. Then, only the variants that could lead to a non-conservative amino acid exchange, a protein truncation, or a splicing aberration were evaluated. So far, no shared variant were identified that could cause this form of CMT. Now we are focusing on the linkage analysis to try to find a single region for genome sequencing. If the mutation responsible for CMT is discovered functional analysis as well as diagnostic application can be put into action.