Refined genetic mapping of juvenile X-linked retinoschisis.

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