GENETIC-MAPPING OF RP1 ON 8Q11-Q21 IN AN AUSTRALIAN FAMILY WITH AUTOSOMAL-DOMINANT RETINITIS-PIGMENTOSA REDUCES THE CRITICAL REGION TO 4 CMBETWEEN D8S601 AND D8S285

The locus (RP1) for one form of autosomal retinitis pigmentosa (adRP) was mapped on chromosome 8q11-q22 between D8S589 and D8S285, which are about 8 cM apart, by linkage analysis in an extended family ascertain ed in the USA. We have studied a multigeneration Australian family wit h adRP and found close linkage without recombination between the disea se locus and D8S591, D8S566, and D8S166 (Z(max) = 1.137-4.650 at theta = 0.00), all mapped in the region known to harbor RP1. Assuming that the mutation of the same gene is responsible for the disease in both f amilies, the analysis of multiply informative meioses in the American and Australian families places the adRP locus between D8S601 and D8S28 5, which reduces the critical region to about 4 cM, corresponding to a pproximately 4 Mb, which is completely covered by a yeast artificial c hromosome contig assembled recently.