Improving molecular diagnosis of Chinese patients with Charcot-Marie-Tooth by targeted next-generation sequencing and functional analysis

// Li-Xi Li 1, * , Shao-Yun Zhao 2, * , Zhi-Jun Liu 1 , Wang Ni 2 , Hong-Fu Li 2 , Bao-Guo Xiao 1 , Zhi-Ying Wu 1, 2 1 Department of Neurology and Institute of Neurology, Huashan Hospital, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Shanghai Medical College, Fudan University, Shanghai, 200040, China 2 Department of Neurology and Research Center of Neurology in Second Affiliated Hospital, and The Collaborative Innovation Center for Brain Science, Zhejiang University School of Medicine, Hangzhou 310009, China * These authors have contributed equally to this work Correspondence to: Zhi-Ying Wu, e-mail: zhiyingwu@zju.edu.cn Keywords: Charcot-Marie-Tooth, molecular diagnosis, targeted next-generation sequencing, genetic variant, functional analysis Received: January 20, 2016      Accepted: March 16, 2016      Published: March 25, 2016 ABSTRACT Charcot-Marie-Tooth (CMT) disease is the most common hereditary peripheral neuropathy. More than 50 causative genes have been identified. The lack of genotype-phenotype correlations in many CMT patients make it difficult to decide which genes are affected. Recently, targeted next-generation sequencing (NGS) has been introduced as an alternative approach for diagnosis of genetic disorders. Here, we applied targeted NGS in combination with PMP22 duplication/deletion analysis to screen causative genes in 22 Chinese CMT families. The novel variants detected by targeted NGS were then further studied in cultured cells. Of the 22 unrelated patients, 8 had PMP22 duplication. The targeted NGS revealed 10 possible pathogenic variants in 11 patients, including 7 previously reported variants and 3 novel heterozygous variants (GJB1: p.Y157H; MFN2: p.G127S; YARS: p.V293M). Further classification of the novel variants according to American College of Medical Genetics and Genomics (ACMG) standards and guidelines and functional analysis in cultured cells indicated that p.Y157H in GJB1 was pathogenic, p.G127S in MFN2 was likely pathogenic, while p.V293M in YARS was likely benign. Our results suggest the potential for targeted NGS to make a more rapid and precise diagnosis in CMT patients. Moreover, the functional analysis is required when the novel variants are indistinct.