Comprehensive Diagnosis of Congenital Neuromuscular Disorders by Next Generation Sequencing of 236 Genes with Deep Coverage (P1.338)

OBJECTIVE: To establish an effective diagnostic approach to identify defective genes responsible for neuromuscular disorders (NMD). BACKGROUND: Neuromuscular disorders are clinically and genetically heterogeneous. Paralytic floppy infant syndrome (PFIS) with muscle weakness and hypotonia is caused by genes responsible for motor neuron diseases, congenital neuropathy, congenital myasthenia gravis syndrome (CMyS), congenital muscular dystrophy (CMD), congenital myopathy (CM), congenital myotonic dystrophy and ion channel disorders (CMtD), metabolic myopathy (mitochondrial disorders, congenital deficiency of glycosylation (CDG), glycolipids storage, peroxisomal disorders), and congenital arthrogryposis. Most patients result in long term disability. While the definitive diagnosis is difficult, it is crucial for genetic counseling, prognosis, and potential therapy. DESIGN/METHODS: All coding exons and at least 20 bp of flanking intronic sequences of 236 genes related to PFIS and NMD are captured followed by Massively Parallel Sequencing (MPS). RESULTS: The target gene capture/deep sequencing provides an average coverage of 1000X. Forty-three patients whose muscle histopathologies consistent with above mentioned NMDs were analyzed. Deleterious mutations were found in 39 patients (91%). Mutations were confirmed in 29 (74%), but not in 10 cases (26%) due to either unavailable parents or inconsistent clinical phenotypes. The most frequently mutated genes are RYR1 and TTN causing congenital myopathy. Using this comprehensive panel, we have identified mutations in congenital neuropathy IGHMBP2 , CM patients with mutations in CMD TCAP and CMyS genes, and MM patients with mutations in channelopathy CACNA1S . Confirmed disease may have therapeutic options. CONCLUSIONS: Target gene capture/deep MPS approach greatly improves the diagnostic yield of congenital NMD. It also demonstrate the power of NGS to confirm and expand clinical phenotypes and genotypes of the extremely heterogeneous NMD. Study Supported by: Disclosure: Dr. Tian has nothing to disclose. Dr. Liang has nothing to disclose. Dr. Feng has nothing to disclose. Dr. Wang has nothing to disclose. Dr. Zhang has nothing to disclose. Dr. Wong has nothing to disclose. Dr. Jong has nothing to disclose.