Lianhua Sun

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.

Double heterozygous mutations of MITF and PAX3 result in Waardenburg syndrome with increased penetrance in pigmentary defects

Yang T, Li X, Huang Q, Li L, Chai Y, Sun L, Wang X, Zhu Y, Wang Z, Huang Z, Li Y, Wu H. Double heterozygous mutations of MITF and PAX3 result in Waardenburg syndrome with increased penetrance in pigmentary defects.

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.

Mutation spectrum and differential gene expression in cystic and solid vestibular schwannoma.

Purpose:We sought to characterize the mutation spectrum of NF2 and the differential gene expression in cystic and solid vestibular schwannomas.Methods:We collected tumor tissue and blood samples of 31 cystic vestibular schwannomas and 114 solid vestibular schwannomas. Mutation screening of NF2 was performed in both tumor and blood DNA samples of all patients. cDNA microarray was used to analyze the differential gene expression between 11 cystic vestibular schwannomas and 6 solid vestibular schwannomas. Expression levels of top candidate genes were verified by quantitative reverse transcription PCR.Results:NF2 mutations were identified in 34.5% of sporadic vestibular schwannomas, with all mutations being exclusively somatic. No significant difference was found between the mutation detection rates of cystic vestibular schwannoma (35.5%) and solid vestibular schwannoma (34.2%). cDNA microarray analysis detected a total of 46 differentially expressed genes between the cystic vestibular schwannoma and solid vestibular schwannoma samples. The significantly decreased expression of four top candidate genes, C1orf130, CNTF, COL4A3, and COL4A4, was verified by quantitative reverse transcription PCR.Conclusion:NF2 mutations are not directly involved in the cystic formation of vestibular schwannoma. In addition, the differential gene expression of cystic vestibular schwannoma reported in our study may provide useful insights into the molecular mechanism underlying this process.Genet Med 2014:16(3):264–270

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.

Molecular etiology and genotype-phenotype correlation of Chinese Han deaf patients with type I and type II Waardenburg Syndrome.

Waardenburg syndrome (WS) characterized by sensorineural hearing loss and pigmentary abnormalities is genetically heterogeneous and phenotypically variable. This study investigated the molecular etiology and genotype-phenotype correlation of WS in 36 Chinese Han deaf probands and 16 additional family members that were clinically diagnosed with WS type I (WS1, n = 8) and type II (WS2, n = 42). Mutation screening of six WS-associated genes detected PAX3 mutations in 6 (86%) of the 7 WS1 probands. Among the 29 WS2 probands, 13 (45%) and 10 (34%) were identified with SOX10 and MITF mutations, respectively. Nineteen of the 26 detected mutations were novel. In WS2 probands whose parental DNA samples were available, de novo mutations were frequently seen for SOX10 mutations (7/8) but not for MITF mutations (0/5, P = 0.005). Excessive freckle, a common feature of WS2 in Chinese Hans, was frequent in WS2 probands with MITF mutations (7/10) but not in those with SOX10 mutations (0/13, P = 4.9 × 10−4). Our results showed that mutations in SOX10 and MITF are two major causes for deafness associated with WS2. These two subtypes of WS2 can be distinguished by the high de novo rate of the SOX10 mutations and the excessive freckle phenotype exclusively associated with the MITF mutations.

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.

A Novel Missense Mutation of NOG Interferes With the Dimerization of NOG and Causes Proximal Symphalangism Syndrome in a Chinese Family

Objectives: NOG is an antagonist to bone morphogenetic proteins and plays an important role in proper bone and joint development. Dominant mutations in NOG may lead to a series of symphalangism spectrum disorders. In this study, we aimed to identify the genetic cause and the pathogenic mechanism of an autosomal dominant disorder with cosegregating proximal symphalangism and conductive hearing impairment in a Chinese family. Methods: Mutation screening of NOG was performed in the affected family members by polymerase chain reaction (PCR) amplification and direct sequencing. Western blotting analysis of NOG was performed in the leukocyte samples of the family members. Results: A novel p.W150C heterozygous mutation in NOG was identified cosegregating with the proximal symphalangism disorder in the family. Western blotting analysis showed that the p.W150C mutation interferes with the dimerization of the mutant NOG. Conclusions: Our results agreed with previously published results of in vitro studies and suggested that impaired dimerization of mutant NOG is an important pathogenic mechanism for the NOG-related symphalangism spectrum disorder.