ORIGINAL ARTICLE Targeted Next-Generation Sequencing Successfully Detects Causative Genes in Chinese Patients with Hereditary Hearing Loss Siqi Chen, 1 Cheng Dong, 1 Qi Wang, 1 Zhen Zhong, 1 Yu Qi, 2 Xiaomei Ke, 1 and Yuhe Liu 1 Aims: We attempted to identify the genetic epidemiology of hereditary hearing loss among the Chinese Han population using next-generation sequencing (NGS). Materials and Methods: The entire length of the genes GJB2, SLC26A4, and GJB3, as well as exons of 57 additional candidate genes were sequenced from 116 individuals suffering from hearing loss. Results: Thirty potentially causative mutations from these 60 genes were identified as the likely etiologies of hearing loss in 67 of the cases. In our study, SLC26A4 and GJB2 were the most frequently affected genes among the Chinese Han population with hearing loss. Collectively, they account for 52.8% of the cases, followed by MTRNR1, PCDH15, and TECTA. These data also illustrate that NGS can be used to identify rare alleles responsible for hereditary hearing loss: 22 of the 30 (73.3%) genes identified with mutations are rarely mutated in hereditary hearing loss and only account for 21.5% (42/195) of the total mutation frequency, explaining no more than 2% for each gene. These rarely mutated genes would be missed by con- ventional diagnostic sequencing approaches. Conclusions: NGS can be used effectively to identify the common and rare genes causing hereditary hearing loss. Keywords: NGS, hearing loss, deafness, genes, mutation Introduction H earing loss is the most common sensory defect in humans. Over 5.0% of the world’s population—328 million adults and 32 million children—has disabling hearing loss (www.who.int). Currently, genetic defects may account for *60% of all early-onset hearing loss (Nance et al., 2006), with an incidence of more than 1 in every 1000 neonates confirmed to be affected in hearing screening (Mehl and Thomson, 2002). Among them, according to etiological studies, 70.0% of cases are nonsyndromic hearing loss with the remaining 30.0% syndromic hearing loss (Nance, 2003). It is still widely accepted that clarifying the genetic diagnosis in this extremely heterogeneous disease remains a tremendous challenge. In recent years, advances and improvements in tar- geted next-generation sequencing (NGS) technology have highlighted its efficiency for identifying causative mutations in Mendelian disorders. Such achievements have also been wit- nessed in hearing loss cohorts, with many studies reporting great successes in the identification of causative variants (Shearer et al., 2010, 2013; Brownstein et al. , 2011; Tang et al., 2012; Chatterjee et al., 2013; Acke et al., 2014). The aim of this study is to clarify the genetic epidemiology in a large number of patients by using a targeted NGS approach in 116 patients that allowed the analysis of 60 hearing- associated genes. Our enrichment design included the custom- targeted enrichment of the full length of GJB2, GJB3, and SLC26A4 and the exons of 57 genes. We describe the mo- lecular epidemiology in Chinese Hans with hearing loss. Materials and Methods Ethics statement This study was approved by the Ethics Committee of Peking University Health Science Center and Peking Uni- versity First Hospital. Written informed consent was ob- tained from all subjects. Recruitment of subjects In total, 116 Chinese patients with hearing loss were re- cruited from the Otolaryngology Head and Neck Surgery Department of Peking University First Hospital, Beijing, China, and a deaf-mute school in Beijing, which was largely composed of subjects with prelingual or early-onset non- syndromic hearing loss. For all subjects, clinical information was obtained and relevant tests were arranged for assessment of the presence of syndromic hearing loss. Mutations in the 1 Department of Otolaryngology Head and Neck Surgery, Peking University First Hospital, Beijing, China. 2 Laboratory Center, Peking University First Hospital, Beijing, China. GENETIC TESTING AND MOLECULAR BIOMARKERS Volume 20, Number 11, 2016 ª Mary Ann Liebert, Inc. Pp. 1–6 DOI: 10.1089/gtmb.2016.0051 1