Date Published: April 11, 2019
Publisher: Public Library of Science
Author(s): Yalan Liu, Chang Hu, Chang Liu, Deyuan Liu, Lingyun Mei, Chufeng He, Lu Jiang, Hong Wu, Hongsheng Chen, Yong Feng, Jumana Yousuf Al-Aama.
Hearing loss (HL) is a common sensory disorder. More than half of HL cases can be attributed to genetic causes. There is no effective therapy for genetic HL at present, early diagnosis to reduce the incidence of genetic HL is important for clinical intervention in genetic HL. Previous studies have identified 111 nonsyndromic hearing loss genes. The most frequently mutated genes identified in NSHL patients in China include GJB2, SLC26A4, and the mitochondrial gene MT-RNR1. It is important to develop HL gene panels in Chinese population, which allow for etiologic diagnosis of both SHL and NSHL. In this study, a total of 220 unrelated Han Chinese patients with bilateral progressive SNHL and 50 unrelated healthy controls were performed Single nucleotide polymorphism (SNP) genotyping using an improved multiplex ligation detection reaction (iMLDR) technique, is to simultaneously detect a total of 32 mutations in ten HL genes, covering all currently characterized mutations involved in the etiology of nonsyndromic or syndromic hearing loss in the Chinese population. The 49 positive samples with known mutations were successfully detected using the iMLDR Technique. For 171 SNHL patients, gene variants were found in 57 cases (33.33%), among which, 30 patients carried mutations in GJB2, 14 patients carried mutations in SLC26A4, seven patients carried mutations in GJB3, and six patients carried mutations in MT-RNR1. The molecular etiology of deafness was confirmed in 12.9% (22/171) of patients carried homozygous variants. These results were verified by Sanger sequencing, indicating that the sensitivity and specificity of the iMLDR technique was 100%. We believe that the implementation of this population-specific technology at an efficient clinical level would have great value in HL diagnosis and treatment.
Hearing loss (HL) is a common sensory disorder, affecting 360 million people worldwide (WHO, 2017) and more than 27 million individuals in China alone. It is estimated that the prevalence of HL is 1 to 3 per 1000 live births, and the total number of children that suffer from HL exceeds 32 million worldwide (WHO, 2017). Both genetic and environmental factors can lead to HL. More than half of congenital HL cases can be attributed to genetic causes, of which 30% are syndromic (SHL) and 70% are nonsyndromic (NSHL). HL is commonly caused by variation in a single gene that adheres to a simple Mendelian inheritance pattern: autosomal dominant, autosomal recessive, X-linked inheritance, Y-linked inheritance, or maternal inheritance. However, more than 1000 known variants in over 100 genes cause HL. Previous studies have mapped 165 NSHL loci, and 111 of these have been cloned (http://hereditaryhearingloss.org, March 2018).
HL affects one in 1000 newborns. However, the heterogeneity of etiologies leading to HL provides a challenge for effective diagnosis and treatment. Mutations in GJB2, SLC26A4, and the mitochondrial gene MT-RNR1 were the most frequently identified in NSHL patients. GJB2 accounts for about 50% of NSHL cases. To date, up to 350 GJB2 mutations have been reported (http://www.hgmd.cf.ac.uk). The most frequently reported mutation in GJB2 in East Asian populations is c.235delC[12, 13]. In this study, GJB2 was the most prevalent causative gene among nonsyndromic SNHL patients. In this gene, three mutations, c.235delC, c.299_300delAT, and c.176_191del16, were detected. Consistent with the results of previous c.235delC was the most prevalent GJB2 mutation detected in this study . The autosomal recessive inheritance of GJB2 mutations means that only the NSHL patients with homozygous or compound heterozygous pathological GJB2 mutations would present with hearing impairment. Therefore, monoallelic GJB2 mutations could not explain the molecular etiology of the subject’s HL in this study. Additional mutations, in other alleles, might be responsible for the HL phenotype. Alternatively, other factors, such as congenital cytomegalovirus (CMV) infection or additional environmental factors, could contribute to HL in this study population.