High carrier frequency of the 35delG deafness mutation in European populations

Congenital deafness accounts for about 1 in 1000 infants and approximately 80% of cases are inherited as an autosomal recessive trait. Recently, it ha s been demonstrated that connexin 26 (GJS2) gene is a major gene for congen ital sensorineural deafness. A single mutation (named 35delG) was found in most recessive families and sporadic cases of congenital deafness, among Ca ucasoids, with relative frequencies ranging from 28% to 63%. We present her e the analysis of the 35delG mutation in 3270 random controls from 17 Europ ean countries. We have detected a carrier frequency for 35delG of 1 in 35 i n southern Europe and 1 in 79 in central and northern Europe. In addition, 35delG was detected in five out of 376Jewish subjects of different origin, but was absent in other non-European populations. The study suggests either a single origin for 35delG somewhere in Europe or in the Middle East, and the possible presence of a carrier advantage together with a founder effect . The 35delG carrier frequency of 1 in 51 in the overall European populatio n clearly indicates that this genetic alteration is a major mutation for au tosomal recessive deafness in Caucasoids. This finding should facilitate di agnosis of congenital deafness and allow early treatment of the affected su bjects.