3231 Frequencies of different forms of autosomal dominant retinitis pigmentosa and a new locus for adRP

m Seven loci for dominant retinitis pigmentoeehave been described in the literature. These include the Rhodopsin and Rdslperipherin genee. and anonymous loci identtfted only by linkage on 7p, 7q. aq, 17p and 19q. We wishedto estimatethe frequendesof the anonymous loci, and determinewhether any adRP loci remained to be found. &@g& DNAe were colleded from twenty ftve adRP families. These were tested by linkage analyeis and mutetiin screening to determine the origin of the phenotype in each family. j&t& Of the twenty five families, the diiease in twelve wes found to be rhcdwein RP either bv linkaae analwie or by mutation detection. A further three map& the 19q adRP &us. one to {he 7p l&us. and one to the 17p locus. Three other familiee gave tentative evidence of linkege,hvo to 19q and one to sq. Four families show crcssovere at all the known loci. Finally in one large family we discovered a new locus. on chromosome 17q between markers D17SBo9 and Dl7S942. Multipoint enalysie in this fern@ gave e maximum led sccfe of 8.24 in this interval. Concluelone In this sample, Rho-RP accounted for approximately50% of adRP while the 19q lccus(RP11) accented for around 20%. All other loci ere rare. Approximately 15% of families map to an unknown locus or loci, proving that adRP is caused by mutations in at least nine dinerent genes.