Molecular diagnosis of congenital muscular dystrophies with defective glycosylation of alpha-dystroglycan using next-generation sequencing technology

Targeted resequencing using next-generation sequencing technology is being rapidly applied to the molecular diagnosis of human genetic diseases. The group of muscular dystrophies may be an appropriate candidate for this approach because these diseases exhibit genotype-phenotype heterogeneity. To perform a proof-of-concept study, we selected four patients with congenital muscular dystrophies with defective glycosylation of alpha-dystroglycan. A custom-solution-based target enrichment kit was designed to capture whole-genic regions of the 26 muscular-dystrophy-related genes, including six genes implicated in alpha-dystroglycanopathies. Although approximately 95% of both coding and noncoding regions were covered with at least 15-read depth, parts of the coding exons of FKRP and POMT2 were insufficiently covered. Homozygous and compound heterozygous POMGnT1 mutations were found in two patients. Two novel noncoding variants of FKTN were identified in one patient who had a retrotransposon insertion mutation of FKTN in only one allele. The current targeted resequencing strategy yielded promising results for the extension of this method to other muscular dystrophies. As suboptimal coverage in a small subset of coding regions may affect the sensitivity of the method, complementary Sanger sequencing may be required.