Carrier rates of the ancestral Indian W24X mutation in GJB2 in the general gypsy population and individual subisolates
Abstract
Mutations in the GJB2 gene are the most common cause of autosomal recessive nonsyndromic hearing loss and occur in approximately 20% of all cases of prelingual deafness. Previous studies of Roma/Gypsies in Slovakia, the Czech Republic, and Spain have shown that W24X, the most common GJB2 mutation in India, is also the prevalent molecular defect in the Gypsy population.
The reported W24X frequencies vary broadly from 23% to 93% of Gypsy mutant alleles, likely reflecting local founder effects, drift, and differential admixture in the subisolates of this genetically structured population. Our goal was to provide more representative data on W24X carrier rates in European Gypsies, which can inform individual diagnostic investigations and public health initiatives across countries.
Mutation testing in 603 control subjects of Gypsy ethnicity, representing 8 traditional subisolates in southeastern Europe and 4 additional European regions revealed that W24X is spread across subisolates, as expected for an ancestral founder mutation. While variation between subisolates does exist, the average carrier rates, overall and in the major linguistic/migrational categories of Balkan Gypsies, Vlax Roma, and west European Gypsies, are consistently in the 4%-5% range.
The results place W24X among the three most common founder mutations in the Gypsies, and classify them as one of the high-risk populations for prelingual deafness. Higher demands on language acquisition in this bilingual population, together with poorer quality of health care compared to autochthonous Europeans, make the consequences of congenital deafness even more damaging than is usually the case.
Neonatal screening for W24X among Gypsies would be a justified and cost-effective public health intervention.