The study of gene GJB2/DFNB1 causing deafness in humans by linkage analysis from district Peshawar.

Families with at least 2 or more individuals having hereditary hearing loss were enrolled from different areas of Khyber Pakhtoonkhwa, mainly from district Peshawar. Detailed history was taken from each family to minimize the presence of other abnormalities and environmental causes for deafness. Families were questioned about skin pigmentation, hair pigmentation, and problems relating to balance, vision, night blindness, thyroid, kidneys, heart, and infectious diseases like meningitis, antibiotic usage, injury, and typhoid. The pedigree structures were based upon interviews with multiple family members, and pedigrees of the enrolled families were drawn using Cyrillic program (version 2.1). All families showed recessive mode of inheritance. I studied 8 families of these 10. For linkage analyses, studies for DFNB1 locus, 3 STR markers (D13S175, D13S292, and D13S787) were genotyped using polyacrylamide gel electrophoresis (PAGE) and haplotypes were constructed to determined, linkage with DFNB1 locus. From a total of 8 families, a single family-10 showed linkage to DFNB1 locus.

Connexin 26 and autosomal recessive non-syndromic hearing loss.

Prelingual deafness occurs with a frequency of 1 in 1000 live births and is divided into syndromic and non-syndromic forms contributing 40 and 60% respectively. Autosomal recessive non-syndromic hearing loss (ARNSHL) is responsible for 80% cases of childhood deafness. Nearly all genes localized for ARNSHL cause prelingual, severe to profound, sensorineural hearing impairment. ARNSHL is genetically heterogeneous and at least 39 loci have been identified. The most significant finding to date has been the discovery of mutations in GJB2 gene at the DFNB1 locus on chromosome 13q12 as the major cause of profound prelingual deafness. This was first reported in a Tunisian family in 1994 and thereafter in many different countries. GJB2 gene encodes the gap-junction protein, connexin 26 (Cx26), mutations in which have become the first genetic marker of inherited hearing loss. Allele-specific polymerase chain reaction (AS-PCR), single stranded conformation polymorphism (SSCP) and sequencing methods have been developed for the detection of mutations in Cx26 gene. In India as well, the Cx26 mutations are being screened in families with hearing impaired children using these molecular methods. Therefore, in order to create awareness among the clinicians and the affected families; we have attempted to review the Cx26 gene mutations responsible for autosomal recessive type of non-syndromic hearing loss. The efficacy and utility of Cx26 gene analysis might open the path to proper counseling of families for carrier detection and prenatal diagnosis. It may even facilitate the development of strategies in future for the treatment of this common genetic disorder.