Deafness, Autosomal Recessive 22

Alternative Names

  • DFNB22

Associated Genes

Otoancorin
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WHO-ICD-10 version:2010

Diseases of the ear and mastoid process

Other disorders of ear

OMIM Number

607039

Mode of Inheritance

Autosomal recessive

Gene Map Locus

16p12.2

Description

Hearing loss is the most common birth defect, with estimates of 1:1000 children being born with profound or severe hearing loss. More than 70% of hereditary hearing loss cases are non-syndromic or isolated, that is, not in association with any other symptoms. In 85% of these non-syndromic cases, the deafness is transmitted as an autosomal recessive trait (DFNB type). As most autosomal recessive loci, DFNB22 causes prelingual severe-to-profound hearing loss.

Molecular Genetics

DFNB22 is caused by homozygous mutation in the OTOA gene on chromosome 16p12.2. The protein encoded by this gene, called otoancorin, is specifically expressed in the inner ear, and is located at the interface between the apical surface of the inner ear sensory epithelia and their overlying acellular gels. It is proposed that this protein is involved in the attachment of the inner ear acellular gels to the apical surface of the underlying nonsensory cells.

Epidemiology in the Arab World

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Other Reports

Palestine

Zwaenepoel et al. (2002) reported a consanguineous Palestinian family with autosomal recessive moderate to severe prelingual sensorineural deafness. The disease in this family segregated with a locus, termed DFNB22, on chromosome 16p13.1-q11.2. Zwaenepoel et al. (2002) identified a splice site mutation in the OTOA gene (IVS12+2T>C) in the homozygous state in one affected child of this family. The mutation was found to cosegregate with the hearing impairment in this kindred and was not detected in 417 Jordanian, Lebanese, Palestinian, and Jewish (mainly Sephardic and Yemenite) individuals with normal hearing.

Walsh et al. (2006) undertook a study to identify the genes responsible for inherited hearing loss, by linkage scan using microsatellite markers in 156 affected individuals and their families. Walsh et al. (2006) identified a mutation in the OTOA gene in a Palestinian family with 6 members diagnosed with prelingual, bilateral, moderate to severe hearing loss. All affected members of the family were found to be homozygous for a missense mutation (c.1067A>T; p.D356V), while all unaffected members of the family were found to be either heterozygous carriers of this mutation or wild type.

Shahin et al. (2010) carried out a molecular study to identify the genes responsible for inherited hearing loss, by using high-density SNP arrays to genotype the DNA of 155 relatives (including: 78 patients, 28 of their hearing siblings, and 49 parents) from 20 Palestinian consanguineous families with prelingual bilateral autosomal recessive non-syndromic hearing loss (NSHL). Shahin et al. (2010) reported one family with sibs (two females and two males) affected with DFNB22. Deaf individuals in this family were found to be homozygous for a large genomic deletion of Otoancorin (OTOA) and their parents were found to be heterozygous for the deletion.

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