Mutations of GJB2 in three geographic isolates from northern Tunisia: evidence for genetic heterogeneity within isolates

Geographically isolated populations have been successfully used to localize genes for recessive inherited diseases, including non-syndromic sensorineu ral recessive deafness (NSRD). To date, 25 loci for NSRD have been localize d on human chromosomes (DFNB loci), and six of the corresponding genes have been identified. Here, we report on the contribution of the DFNB1 locus (GJB2 gene) to NRSD in seven affected families living in three northern Tunisian geographic iso lates, and we provide evidence fbr genetic heterogeneity within isolates. T his finding challenges the classical view of a single 'founder' mutation se gregating in such isolates.