Clinical study and genetics of non syndromic congenital deafness

ABSTRACT

Hearing impairment affects 1/1000 infants. Congenital deafness is inherited or apparently sporadic. DFNB1 on chromosome 13 is a major locus for recessive deafness in about 80% of Mediterranean families and the connexin-26 gene gap junction protein b2 [GJB2] is mutated in DFNB1 families. We acquired DNA samples from 38 families of Moroccan children with recessive non-syndromic deafness and 95 unrelated participants with apparently sporadic congenital deafness. Therefore, we analysed the coding region of the GJB2 gene for mutations. Findings: 31.5% of participants with recessive deafness and 21.5% of sporadic deafness had mutations in the GJB2 gene. The 35delG mutation represented 24.1% of GJB2 mutations. GJB2 gene mutation is a major cause of inherited congenital deafness. 35delG mutation is the most common mutation for inherited congenital deafness. This study shows that 35delG mutation prevalence is important in Morocco with a prevalence of 31.5%, while it is inexistent in Asian population, and very rare in Africa [2.2%]. Such prevalence disparity may reflect an anthropological history of human travels. So, 35delG mutation has a Mediterranean origin. In conclusion, the mutation in the connexion-26 GJB2 gene is the most common cause of non syndromic autosomal recessive deafness in Morocco. More studies are needed to confirm these findings: