REFINED GENETIC-MAPPING OF JUVENILE X-LINKED RETINOSCHISIS

Juvenile X-linked retinoschisis (RS) is an eye disease that causes acu ity reduction and peripheral visual field loss typically beginning ear ly in life. In further work towards positional cloning of the RS gene, we restudied our previously reported seven large American families an d one additional new family, with a total of 63 affected males. RS lin kage analysis using microsatellite repeat markers gave the following r esults: DXS207 (Z = 24.89, theta = 0.01), DXS987 (Z = 24.04, theta 0.0 1) and DXS999 (Z = 14.70, theta = 0.00). Recombination events in four individuals were studied further with additional markers (AFM291wf5, D XS443, DXS1052, DXS274 and DXS1226), and a flanking interval was obtai ned (DXS43, DXS207, DXS987)-RS-(AFM291wf5, DXS443). This study moves t he RS centromeric boundary to (AFM291wf5, DXS443), about 5.5 cM closer than the previously reported boundary at DXS274 and narrows the RS in clusion interval to about 3.7 cM (using distances from CEPH family dat a).