Evaluation of the myosin VIIA gene and visual function in patients with Usher syndrome type I

Usher syndrome type I (USH1) is a recessively-inherited disorder consisting of retinitis pigmentosa, profound congenital deafness, and vestibular atax ia. It can be caused by mutations in at least six different loci (USH1A-IF) . The gene encoding human myosin VIIA (MYO7A) is the USH1B locus. In this s tudy, hh unrelated patients with USH1 were evaluated for defects in MYO7A u sing single-strand conformation polymorphism analysis and direct genomic se quencing. Twenty-nine per cent of cases were found to have likely pathogeni c MYO7A, mutations. A total of 22 likely pathogenic changes were identified , 18 of which were novel. Cosegregation analysis of mutations in five avail able families showed that the MYO7A changes segregated with the disease in an autosomal recessive fashion. Average visual function as measured by Visu al acuity, visual field area, and ERG amplitude was not significantly diffe rent between the group of patients with likely pathogenic MYO7A changes and the group in which no likely pathogenic MYO7A changes were detected. (C) 2 000 Academic Press.