Dataset Information

Novel homozygous variant in the PDZD7 gene in a family with nonsyndromic sensorineural hearing loss.

ABSTRACT: Hearing loss is the most common sensory neural disorder in humans, and according to a WHO estimation, 5.5% (466 million) of people worldwide have disabling hearing loss. In this study, a Chinese family with prelingual sensorineural hearing loss was investigated. The affected individuals showed moderately severe hearing loss at all frequencies. Using target genome enrichment and high-throughput sequencing, the homozygous variant c.2372del; p.(Ser791fs) was identified in PDZD7. This variant lies in exon 15 of PDZD7 and results in a frame shift followed by an early stop codon. It is classified as pathogenic according to the ACMG/AMP guidelines and ClinGen specifications. Our study expands the pathogenic variant spectrum of PDZD7 and strengthens the clinical importance of this gene in patients with moderately severe hearing loss.

SUBMITTER: Du Q

PROVIDER: S-EPMC9204979 | biostudies-literature | 2022 Jun

REPOSITORIES: biostudies-literature

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Novel homozygous variant in the PDZD7 gene in a family with nonsyndromic sensorineural hearing loss.

Du Qiang Q Sun Qin Q Gu Xiaodong X Wang Jinchao J Li Weitao W Guo Luo L Li Huawei H

BMC medical genomics 20220617 1

Hearing loss is the most common sensory neural disorder in humans, and according to a WHO estimation, 5.5% (466 million) of people worldwide have disabling hearing loss. In this study, a Chinese family with prelingual sensorineural hearing loss was investigated. The affected individuals showed moderately severe hearing loss at all frequencies. Using target genome enrichment and high-throughput sequencing, the homozygous variant c.2372del; p.(Ser791fs) was identified in PDZD7. This variant lies i ...[more]

PMID: 35715776

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Project description:Hereditary hearing impairment is one of the major and common birth defects in Chinese population. Non-syndromic sensorineural hearing loss (NSHL) is the most common types of hereditary hearing impairment. Genotypically and phenotypically NSHL is extremely heterogenous and follow either autosomal dominant or autosomal recessive or X-linked mode of inheritance. Presently, 127 genes have been identified to be associated with both syndromic and (NSHL). Here, we studied a Chinese family with moderate and profound hearing impairment. The proband is a 30-year old Chinese man. The proband was born with normal hearing and at the age of 5-years, the proband was first noticed with hearing impairment. Gradually and progressively the proband was presented with loss of hearing in his both right and left ears at the age of 30 years. The clinical symptoms, age of onset or progression to loss of hearing was similar in both the proband and his younger brother. The proband's parents are phenotypically normal and non-consanguineous. Clinical diagnosis of the proband and his younger brother has been done by classical pure tone audiogram (PTA). Computed Tomography (CT) found no abnormality in bilateral external ear, middle ear and inner ear. Targeted next generation sequencing was performed with a panel of 127 genes reported to be associated with hereditary hearing impairment. A novel homozygous single nucleotide deletion (c.427delT) in exon 4 of ILDR1 gene has been identified in proband and in his younger brother. Sanger sequencing confirmed that proband's father and mother are carrying this mutation in a heterozygous manner. This mutation has not been identified in 100 normal healthy control individuals. This mutation (c.427delT) causes frameshift (p.Tyr143Ilefs∗19) which leads to the formation of a truncated ILDR1 protein of 162 amino acids instead of the wild type ILDR1 protein of 546 amino acids. ILDR1 associated hereditary hearing impairment is very rare and this is the first report of identifying a loss-of-function mutation in ILDR1 gene associated with hereditary hearing impairment in Chinese population. Our present study also emphasized the significance of rapid, accurate and cost-effective screening for the patient with hereditary hearing impairment by targeted next generation sequencing.

Project description:ImportanceSensorineural hearing loss (SNHL) is commonly caused by conditions that affect cochlear structures or the auditory nerve, and the genes identified as causing SNHL to date only explain a fraction of the overall genetic risk for this debilitating disorder. It is likely that other genes and mutations also cause SNHL.ObjectiveTo identify a candidate gene that causes bilateral, symmetric, progressive SNHL in a large multigeneration family of Northern European descent.Design, setting, and participantsIn this prospective genotype and phenotype study performed from January 1, 2006, through April 1, 2016, a 6-generation family of Northern European descent with 19 individuals having reported early-onset hearing loss suggestive of an autosomal dominant inheritance were studied at a tertiary academic medical center. In addition, 179 unrelated adult individuals with SNHL and 186 adult individuals reporting nondeafness were examined.Main outcomes and measuresSensorineural hearing loss.ResultsNine family members (5 women [55.6%]) provided clinical audiometric and medical records that documented hearing loss. The hearing loss is characterized as bilateral, symmetric, progressive SNHL that reached severe to profound loss in childhood. Audiometric configurations demonstrated a characteristic dip at 1000 to 2000 Hz. All affected family members wear hearing aids or have undergone cochlear implantation. Exome sequencing and linkage and association analyses identified a fully penetrant sequence variant (rs35725509) on chromosome 12q21 (logarithm of odds, 3.3) in the TMTC2 gene region that segregates with SNHL in this family. This gene explains the SNHL occurrence in this family. The variant is also associated with SNHL in a cohort of 363 unrelated individuals (179 patients with confirmed SNHL and 184 controls, P = 7 × 10-4).Conclusions and relevanceA previously uncharacterized gene, TMTC2, has been identified as a candidate for causing progressive SNHL in humans. This finding identifies a novel locus that causes autosomal dominant SNHL and therefore a more detailed understanding of the genetic basis of SNHL. Because TMTC2 has not been previously reported to regulate auditory function, the discovery reveals a potentially new, uncharacterized mechanism of hearing loss.

Dataset Information

Novel homozygous variant in the PDZD7 gene in a family with nonsyndromic sensorineural hearing loss.

Publications

Novel homozygous variant in the PDZD7 gene in a family with nonsyndromic sensorineural hearing loss.

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