Résumé :
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Neuromuscular diseases (NMD) are debilitating diseases with a strong impact on the individuals and the society. Despite tremendous research and clinical efforts, the molecular causes of NMD are still unknown for about 40% of patients, and additional genes remain to be implicated. This is mainly due to genetic heterogeneity (mutations in several genes causing the same or very similar disease), and phenotypic heterogeneity (one gene implicated in different diseases). In order to provide a faster and cheaper molecular diagnosis for NMD patients and identify novel genes mutated in congenital myopathies, we have validated sequence capture and next generation sequencing (NGS) in-house using Agilent liquid capture and Illumina GAIIx sequencer.Molecular diagnosis: Using targeted re-sequencing of 230 genes in 7 patients with known mutations and either congenital myopathies or dystrophies, we successfully retrieved the deleterious mutations in 6 of them (covering point mutations, intronic mutation 10nt from the exon, a small deletion, and a large hemizygous deletion). The exon harbouring the mutation in the last patient did not have a sufficient coverage and we are currently updating the sequencing protocol and capture library design. NGS is thus able to detect different classes of mutations both at the homozygous and heterozygous state, and might be developed as a first molecular screening before more invasive or time-consuming investigations are performed, to shorten diagnosis wandering of patients.Identification of novel genes: We are performing targeted re-sequencing of thousand of candidate genes or whole exome sequencing in patients with different congenital myopathies. For example, starting from a recessive case with centronuclear myopathy, we identified potential mutations in a gene usually linked to another myopathy suggesting allelic disorders.We conclude that next generation sequencing is a powerful approach to identify potential disease-causing variants in neuromuscular diseases, a prerequisite for genetic counselling, better healthcare, inclusion into most clinical trials and, in the case of novel gene, for the identification of new therapeutic targets.
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