A 9TH LOCUS (RP18) FOR AUTOSOMAL-DOMINANT RETINITIS-PIGMENTOSA MAPS IN THE PERICENTROMERIC REGION OF CHROMOSOME-1

We studied a large Danish family of seven generations in which autosom al dominant retinitis pigmentosa (adRP), a heterogeneous genetic form of retinal dystrophy, was segregating, After linkage had been excluded to all known adRP loci on chromosomes 3q, 6p, 7p, 7q, 8q, 17p, 17q an d 19q, a genome screening was performed, Positive lod scores suggestiv e of linkage with values ranging between Z = 1.58-5.36 at theta = 0.04 -0.20 were obtained for eight loci on proximal 1p and 1q. Close linkag e without recombination and a maximum lod score of 7.22 at theta = 0.0 0 was found between the adRP locus (RP18) in this family and D1S498 wh ich is on Iq very near the centromere. Analysis of multiply informativ e meioses suggests that in this family D1S534 and D1S305 flank RP18 in interval 1p13-q23, No linkage has been found to loci from this chromo somal region in six other medium sized adRP families in which the dise ase locus has been excluded from all known chromosomal regions harbour ing an adRP gene or locus suggesting that there is (at least) one furt her adRP locus to be mapped in the future.