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

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

Genotypes and phenotypes of subjects with dominant <i>GJB2</i> mutations.

<p>*Probands.</p

Representative epidermal abnormalities of the subjects carrying dominant <i>GJB2</i> mutations.

<p>(A) Thickening of the skin and the circular keratotic constriction band (box); (B) Peeling (box) and deep fissures (arrow in the box); (C) Punctiform keratoderma; (D) Callus (the upper box) and striped keratoderma (the lower box); (E) Thickened nails; (F) Brittle nails; (G) Erythema; (H) knuckle pad; (I) spooned nails.</p

Genotype and phenotype characterization of Fmaily D439.

<p>(A) Pedigree and the genotypes of family members. (B) HL phenotypes of D439-1, D439-2 and D439-4. (C) PPK phenotypes of D439-1, D439-2 and D439-4. Note that D439-1 and D439-4 had more severe keratoderma than D439-2 (the left and right panels), and that a number of PPK-associated epidermal abnormalities observed in D439-1 and D439-4 were absent in D439-2, including peeling of the skin (arrows in the right panel), knuckle pad (arrows, the middle panel) and circular keratotic constriction band (arrows, the left panel).</p

Genotype and phenotype characterization of Fmaily 209.

<p>(A) Pedigree and the genotypes of family members. Proband C209-1 with <i>de novo</i> p.R184Q mutation of <i>GJB2</i> was pointed by the arrow. (B) HL phenotypes of C209-1. (C) PPK phenotypes of C209-1 including the thickening and peeling of the skin, keratoderma, callus (the left panel), spoon nails of the toes (the middle panel) and thickened nails of the fingers (the right panel). (D) Skin biopsy of the left sole showing hyperkeratosis, thickening of the granular layer, acanthosis, and sparse lymphocytes infiltration in the superficial layer of dermis. (Hematoxylin-eosin stain; original magnification ×200.).</p

Genotype and phenotype characterization of Family D441.

<p>(A) Pedigree and the genotypes of family members. Subject D441-2 with <i>de novo</i> p.R75W mutation of <i>GJB2</i> was pointed by the arrow. (B) HL phenotypes of D441-1 and D441-2. (C) PPK phenotypes of D441-1 and D441-2. Note that D441-1 had more severe keratoderma (the third panels) and erythema (the second, fourth and fifth panels) than D441-2, and that the PPK phenotype of D441-1 was extended to the wrist (the second panels), the ankle (the fourth and fifth panels) and the back of the hands and feet (the second and fourth panels).</p

Pedigree, genotype and phenotype characterization of Family F13.

<p>A) Pedigree and SNP genotypes of Family F13. The proband F13-2 is pointed by the arrow. SNP genotypes of subjects F13-1, F13-2, F13-6 and F13-7 showed a loss of heterozygosity (in dotted box) in the affected individuals. B) Representative audiograms of subject F13-6. The gaps between the air- (AC) and bone-conducted (BC) hearing thresholds indicate a conductive hearing loss. C) Images and digital radiography of the hands of subject F13-5 showing fusion of the proximal interphalangeal joints at the fifth fingers (arrows).</p

Mapping and identification of the breakpoints of the 1.6-Mb microdeletion in Family F13.

<p>A) Schematic illustration of the mapping and identification process. The results of array-CGH, quantitative real-time PCR and sequencing across the breakpoints are shown in the top, middle and bottom panels, respectively. B) A 1.2-kb PCR product was amplified from the mutant allele across the breakpoints in the five affected family members F13-2, F13-3, F13-5, F13-6 and F13-7, but not in the unaffected family member F13-4.</p

Comparison of the genes and the genomic intervals deleted by the microdeletions in chromosome 17q22 that are associated with <i>NOG</i>-SSD only (dark gray), ID only (light gray), or both <i>NOG</i>-SSD and ID (black).

<p>Candidate regions for causative genes of ID are shown by the brackets on the top.</p

Targeted Next-Generation Sequencing in Uyghur Families with Non-Syndromic Sensorineural Hearing Loss

<div><p>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 <i>GJB2</i>, <i>SLC26A4</i> and <i>MT-RNR</i>1 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 <i>TMC1</i>, the homozygous p.V1880E mutation in <i>MYO7A</i>, c.1238delT frameshifting deletion in <i>PCDH15</i> and c.9690+1G>A splice site mutation in <i>MYO15A</i>. 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.</p></div