A NOVEL LOCUS FOR LEBER CONGENITAL AMAUROSIS ON CHROMOSOME 14Q24

Leber congenital amaurosis (LCA) is a clinically and genetically heter ogeneous autosomal recessive retinal dystrophy and the most common gen etic cause of congenital visual impairment. We used a DNA pooling stra tegy comparing the genotypes of affected to unaffected control pools i n a genome-wide search for identity-by-descent on a consanguineous Sau di Arabian LCA family, A shift to homozygosity was observed in the aff ected DNA pool compared with the control pool at linked markers D14S60 6 and D14S610. Genotyping of individual DNA samples from the entire pe digree for marker D14S74, closely linked to these loci, and several fl anking markers confirmed linkage with a Z(MAX)=13.29 at theta=0.0. The se data assign a third locus (LCA3) for LCA to chromosome 14q24. This locus and the previously identified loci are excluded for other Saudi Arabian pedigrees, both confirming that this clinical disorder is gene tically heterogeneous and that additional LCA genes remain to be ident ified.