Genetic analysis of a Chinese family with members affected with Usher syndrome type II and Waardenburg syndrome type IV

Next-generation sequencing identifies rare pathogenic and novel candidate variants in a cohort of Chinese patients with syndromic or nonsyndromic hearing loss

Background

Hearing loss (HL) is a common sensory disorder in humans characterized by extreme clinical and genetic heterogeneity. In recent years, next‐generation sequencing (NGS) technologies have proven to be highly effective and powerful tools for population genetic studies of HL. Here, we analyzed clinical and molecular data from 21 Chinese deaf families who did not have hotspot mutations in the common deafness genes GJB2, SLC26A4, GJB3, and MT‐RNR1.

Method

Targeted next‐generation sequencing (TGS) of 127 known deafness genes was performed in probands of 12 families, while whole‐exome sequencing (WES) or trio‐WES was used for the remaining nine families.

Results

Potential pathogenic mutations in a total of 12 deafness genes were identified in 13 probands; the mutations were observed in GJB2, CDH23, EDNRB, MYO15A, OTOA, OTOF, TBC1D24, SALL1, TMC1, TWNK, USH1C, and USH1G, with eight of the identified mutations being novel. Further, a copy number variant (CNV) was detected in one proband with heterozygous deletion of chromosome 4p16.3‐4p15.32. Thus, the total diagnostic rate using NGS in our deafness patients reached 66.67% (14/21).

Conclusions

These results expand the mutation spectrum of deafness‐causing genes and provide support for the use of NGS detection technologies for routine molecular diagnosis in Chinese deaf populations.

Whole exome sequencing identifies novel USH2A mutations and confirms Usher syndrome 2 diagnosis in Chinese retinitis pigmentosa patients

Retinitis pigmentosa (RP) is a common phenotype in multiple inherited retinal dystrophies (IRD). Disease gene identification can assist the clinical diagnosis of IRD patients for better clinical management, treatment and counseling. In this study, we aimed to delineate and characterize the disease-causing mutations in Chinese familial and sporadic patients with initial diagnosis of RP. Four unrelated Chinese families and 118 sporadic RP patients were recruited for whole exome sequencing analysis. A total of 5 reported and 3 novel USH2A mutations were identified in four Chinese probands. The probands and their family members showed typical RP features and mild to severe hearing impairment, confirming the diagnosis of Usher syndrome 2 (USH). Moreover, 11 sporadic RP patients were identified to carry the compound heterozygous mutations in the USH2A gene, confirming the diagnosis of USH2. The patients carried the truncating mutations had a younger age of first visit than the patients carried only the missense mutations (p = 0.017). In summary, this study revealed 8 novel USH2A variants in Chinese familial and sporadic RP patients, assuring that whole exome sequencing analysis is an adequate strategy to facilitate the clinical diagnosis of USH from the sporadic RP patients.