A NEW AUTOSOMAL RECESSIVE RETINITIS-PIGMENTOSA LOCUS MAPS ON CHROMOSOME 2Q31-Q33

Autosomal recessive retinitis pigmentosa (ARRP) is a genetically heter ogeneous disease. To date, mutations in four members of the phototrans duction cascade have been implicated in ARRP. Additionally, linkage of the disease to three loci on 1p, 1q, and 6p has been described. Howev er, the majority of cases are still uncharacterised. We have performed linkage analysis in a large nuclear ARRP family with five affected si bs. After exclusion of several regions of the genome known to contain loci for retinal dystrophies, a genomic search for linkage to ARRP was undertaken. Positive lod scores were obtained with markers on 2q31-q3 3 (Zmax at 0=0.00 of 4.03, 4.12, and 4.12 at D2S364, D2S118, and D2S38 9, respectively) defining an interval of about 7 cM for this new ARRP locus, between D2S148 and D2S161. Forty-four out of 47 additional ARRP families, tested with markers on 2q32, failed to show linkage, provid ing evidence of further genetic heterogeneity.