EVIDENCE FOR A FOURTH LOCUS IN USHER SYNDROME TYPE-I

Usher syndrome type I (US1) is an autosomal recessive condition in whi ch three different genes have been already localised (USH1A, USH1B, an d USH1C on chromosomes 14q32, 11q13, and 11p15 respectively). The gene tic heterogeneity of US1 has been confirmed in a previous study by lin kage analysis of 20 French pedigrees. Here, we report the genetic excl usion of the three previously reported loci in two large multiplex fam ilies of Moroccan and Pakistani origin, suggesting the existence of at least a fourth locus in Usher syndrome type I.