Linkage mapping of new X-linked juvenile retinoschisis kindreds using microsatellite markers.

X-linked retinoschisis (RS) is an inherited bilateral eye disorder with variable clinical manifestations. Previous studies have localized RS locus to the region Xp22.1-p22.3 on the short arm of the X-chromosome. In an attempt to map the RS locus more precisely, we have performed linkage analysis in four previously unreported kindreds of different geographic origins using six microsatellite markers - DXS987, DXS207, DXS999, DXS443, DXS365 and DXS274 -- all located in the region Xp22.1-p22.3. Two point analysis suggests linkage to DXS207 (Zmax = 1.8 at theta max = 0) and DXS999, DXS443, DXS365 and DXS274 (Zmax = 1.2 at theta max = 0). Multipoint analysis has confirmed this linkage with these same markers (Zmax = 2.107 at theta = 0). There are no recombinants between the disease phenotype and the above markers. These results indicate that RS gene in our families is located in the same inclusion interval (between DXS987 and DXS274) reported for other RS families. Furthermore, they confirm the lack of genetic/locus heterogeneity of RS.