Dongye Chen

The homozygous p.V37I variant of GJB2 is associated with diverse hearing phenotypes

The homozygous p.V37I variant of GJB2 is frequent in East Asians and has been reported to have a pathogenic role in mild‐to‐moderate hearing impairment (HI). In this study, we investigated the prevalence and phenotypic spectrum of homozygous p.V37I in three Chinese Han cohorts with severe‐to‐profound HI (n = 857, Cohort S), mild‐to‐moderate HI (n = 88, Cohort M) and normal hearing (n = 1550, Cohort N). Sequencing of GJB2 showed that homozygous p.V37I was detected in 1.63% (14/857), 12.5% (11/88) and 0.32% (5/1550) of subjects in Cohorts S, M and N, respectively. It was strongly associated with both mild‐to‐moderate (p = 2.0 × 10−11) and severe‐to‐profound (p = 0.001) HI, but was estimated to have a rather low penetrance (17%). Among the hearing impaired subjects with homozygous p.V37I, the onset of HI was congenital in 65% (11/17) and delayed in 35% (6/17). By targeted next‐generation sequencing of 79 known deafness genes, we identified an additional homozygous pathogenic mutation of CDH23 in 1 of 14 p.V37I homozygous subjects from Cohort S. Our study suggested that homozygous p.V37I is associated with a broader spectrum of hearing phenotypes than previously revealed. Data presented in this study can be effectively applied to clinical evaluation and genetic counseling of people carrying this variant.

Targeted next-generation sequencing in Uyghur families with non-syndromic sensorineural hearing loss.

The mutation spectrum of deafness genes may vary in different ethnical groups. In this study, we investigated the genetic etiology of nonsyndromic deafness in four consanguineous and two multiplex Uyghur families in which mutations in common deafness genes GJB2, SLC26A4 and MT-RNR1 were excluded. Targeted next-generation sequencing of 97 deafness genes was performed in the probands of each family. Novel pathogenic mutations were identified in four probands including the p.L416R/p.A438T compound heterozygous mutations in TMC1, the homozygous p.V1880E mutation in MYO7A, c.1238delT frameshifting deletion in PCDH15 and c.9690+1G>A splice site mutation in MYO15A. Co-segregation of the mutations and the deafness were confirmed within each family by Sanger sequencing. No pathogenic mutations were identified in one multiplex family and one consanguineous family. Our study provided a useful piece of information for the genetic etiology of deafness in Uyghurs.

Clinical characterization of a novel COCH mutation G87V in a Chinese DFNA9 family

OBJECTIVES To characterize the clinical features of a Chinese DFNA9 family associated with a novel COCH mutation and to confirm the proposed genotype-phenotype correlation of COCH. METHODS Mutation screening of 79 deafness genes was performed in the proband by targeted next-generation sequencing. Co-segregation of the disease phenotype and the detected variants was confirmed in all family members by PCR amplification and Sanger sequencing. The progression of hearing impairment in affected family members was followed and the concomitant vestibular dysfunction was verified by the caloric vestibulo-ocular reflex test. RESULTS A novel COCH mutation p.G87V was identified in the family segregating with late-onset, progressive sensorineural hearing impairment and consistent vestibular dysfunction. CONCLUSION The p.G87V mutation leads to a very similar phenotype as a previously reported p.G87W mutation of COCH. Our study suggested that the G87 residue is critical for function of COCH and further confirms a previously proposed genotype-phenotype correlation for DFNA9.

Characterization of Spectrum, de novo Rate and Genotype-Phenotype Correlation of Dominant GJB2 Mutations in Chinese Hans

Dominant mutations in GJB2 may lead to various degrees of sensorineural hearing impairment and/or hyperproliferative epidermal disorders. So far studies of dominant GJB2 mutations were mostly limited to case reports of individual patients and families. In this study, we identified 7 families, 11 subjects with dominant GJB2 mutations by sequencing of GJB2 in 2168 Chinese Han probands with sensorineural hearing impairment and characterized the associated spectrum, de novo rate and genotype-phenotype correlation. We identified p.R75Q, p.R75W and p.R184Q as the most frequent dominant GJB2 mutations among Chinese Hans, which had a very high de novo rate (71% of probands). A majority (10/11) of subjects carrying dominant GJB2 mutations exhibited palmoplantar keratoderma in addition to hearing impairment. In two families segregated with additional c.235delC or p.V37I mutations of GJB2, family members with the compound heterozygous mutations exhibited more severe phenotype than those with single dominant GJB2 mutation. Our study suggested that the high de novo mutation rate gives rise to a significant portion of dominant GJB2 mutations. The severity of the hearing and epidermal phenotypes associated with dominant GJB2 mutations may be modified by additional recessive mutations of GJB2.

Molecular etiology of non-dominant, non-syndromic, mild-to-moderate childhood hearing impairment in Chinese Hans

Childhood hearing impairment (HI) is genetically heterogeneous. Compared with the severe‐to‐profound HI, the molecular etiology of mild‐to‐moderate HI in children has been less well characterized, especially for those not inherited in the dominant mode. In this study, we recruited 114 probands with non‐dominant, non‐syndromic, mild‐to‐moderate childhood HI. Sequencing of GJB2, SLC26A4, and MTRNR1 identified causative mutations in 30.7% (35/114), 4.4% (5/114), and 4.4% (5/114) of subjects, respectively. A majority (62.9%) of bi‐allelic GJB2 mutations have non‐truncating mutations in at least one allele. In 10 multiplex probands with no GJB2, SLC26A4, and MTRNR1 mutations identified, targeted next‐generation sequencing (NGS) of 79 known deafness genes did not identify any additional causes. Our data showed that the molecular etiology of mild‐to‐moderate childhood HI is considerably different from what reported for severe‐to‐profound HI and far from complete for those inherited in non‐dominant modes.

A novel splice site mutation in DFNA5 causes late-onset progressive non-syndromic hearing loss in a Chinese family.

OBJECTIVES Mutations in DFNA5 may lead to autosomal dominant non-syndromic sensorineural hearing loss (NSHL). To date, only four DFNA5 mutations have been reported, all resulting in skipping of exon 8 at the mRNA level. In this study, we aim to characterize the clinical features and the genetic cause of a Chinese DFNA5 family. METHODS Targeted next-generation sequencing of 79 known deafness genes was performed in the proband. Co-segregation between the disease phenotype and the potentially pathogenic variant was confirmed in all family members by Sanger sequencing. RESULTS A novel heterozygous c.991-2A>G mutation in DFNA5 was identified in this family segregating with the autosomal dominant, late-onset NSHL. This mutation was located in the conventional splice site in intron 7 and was likely to result in skipping of exon 8. The severity of hearing impairment varied intrafamilially. CONCLUSION We identified a novel c.991-2A>G mutation in DFNA5 which again may lead to exon 8 skipping at the mRNA level. Our findings supported that the DFNA5-associated NSHL results from a specific gain-of-function mechanism.

A dominant variant in DMXL2 is linked to nonsyndromic hearing loss.

Purpose:To explore the genetic etiology of deafness in a dominant family with late-onset, progressive, nonsyndromic hearing loss.Methods:Genome-wide linkage analysis was performed for 21 family members. Candidate pathogenic variants were identified by whole-exome sequencing of selected family members and confirmed by Sanger sequencing of all family members. Cochlear expression of Dmxl2 was investigated by reverse-transcription polymerase chain reaction (RT-PCR) and immunostaining of the organ of Corti from mice.Results:The causative gene was mapped to a 9.68-Mb candidate region on chromosome 15q21.2 (maximum logarithm of the odds score = 4.03) that contained no previously described deafness genes. Whole-exome sequencing identified heterozygous c.7250G>A (p.Arg2417His) in DMXL2 as the only candidate pathogenic variant segregating the hearing loss. In mouse cochlea, expression of DMXL2 was restricted to the hair cells and the spiral ganglion neurons.Conclusion:Our data indicated that the p.Arg2417His variant in DMXL2 is associated with dominant, nonsyndromic hearing loss and suggested an important role of DMXL2 in inner ear function.Genet Med advance online publication 22 September 2016

Mutation in PCDH15 may modify the phenotypic expression of the 7511T>C mutation in MT-TS1 in a Chinese Han family with maternally inherited nonsyndromic hearing loss

OBJECTIVES Mutations in MT-TS1 have been found to be associated with nonsyndromic sensorineural hearing loss (SNHL). PCDH15 codes for protocadherin-15, a member of the cadherin superfamily of calcium-dependent cell-cell adhesion molecules. In this study, we analyzed the correlation of both MT-TS1 and PCDH15 mutations in a Chinese Han family segregating maternally inherited nonsyndromic SNHL. METHODS We ascertained a Chinese Han family segregating maternally inherited nonsyndromic sensorineural hearing loss. Eight of 10 maternal members in this family exhibited late-onset, progressive hearing impairment. Mutation screening of 79 known deafness genes was performed for the proband by targeted next-generation sequencing. RESULTS A total of 651 variants were detected in this individual. Among them, a homoplasmic 7511T>C variant in MT-TS1, the mitochondrial tRNA (Ser(UCN)) gene, and a heterozygous p.Asp1010Gly variant in PCDH15 were more likely to be pathogenic. Consistent with the matrilineal inheritance with reduced penetrance, the 7511T>C variant in MT-TS1 was found in all 10 maternal members and an additional heterozygous p.Asp1010Gly variant in PCDH15 cosegregated with the hearing loss in this family. CONCLUSION Our results suggested that the PCDH15 p.Asp1010Gly variant probably modified the phenotypic expression of the 7511T>C mutation in MT-TS1.

Mutation analysis of seven consanguineous Uyghur families with non- syndromic deafness

OBJECTIVE To investigate the genetic causes of consanguineous Uyghur families with nonsyndromic deafness. METHOD Seven consanguineous Uyghur families with nonsyndromic deafness were recruited in this study and characterized for their audiometric phenotype. Mutation analysis of common deafness genes GJB2, SLC26A4 and MT-RNR1 was performed in all families by direct sequencing. RESULT Bi-allelic mutations in SLC26A4, including p.N392Y/p.N392Y, p.S57X/p.S57X and p.Q413R/p.L676Q, were detected in three families as the pathogenic causes for the deafness. No mutations were identified in GJB2 and MT-RNR1. CONCLUSION Mutations in SLC26A4 was the most common causes of the Uyghur consanguineous deaf families.

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

AIMS The purpose of this study was to identify the genetic causes of a family presenting with multiple symptoms overlapping Usher syndrome type II (USH2) and Waardenburg syndrome type IV (WS4). METHODS Targeted next-generation sequencing including the exon and flanking intron sequences of 79 deafness genes was performed on the proband. Co-segregation of the disease phenotype and the detected variants were confirmed in all family members by PCR amplification and Sanger sequencing. RESULTS The affected members of this family had two different recessive disorders, USH2 and WS4. By targeted next-generation sequencing, we identified that USH2 was caused by a novel missense mutation, p.V4907D in GPR98; whereas WS4 due to p.V185M in EDNRB. This is the first report of homozygous p.V185M mutation in EDNRB in patient with WS4. CONCLUSION This study reported a Chinese family with multiple independent and overlapping phenotypes. In condition, molecular level analysis was efficient to identify the causative variant p.V4907D in GPR98 and p.V185M in EDNRB, also was helpful to confirm the clinical diagnosis of USH2 and WS4.