Refinement of the chromosomal position of the X linked juvenile retinoschisis gene.

Linkage analysis was carried out in seven X linked juvenile retinoschisis (XLRS) families using four DNA probes and four CA repeat polymorphisms from the Xp22 region. Close linkage was observed between the XLRS locus and DXS207 (theta max = 0.04, Zmax = 3.71), DXS999 (theta max = 0.00, Zmax = 4.59), DXS365 (theta max = 0.07, Zmax = 2.22), and DXS451 (theta max = 0.05, Zmax = 3.26). The analysis of recombination breakpoints and multipoint linkage analysis suggests the order Xpter-DXS16-(DXS43, DXS207)-RS-DXS365-(DXS451, DXS41)-Xcen, thereby refining the position of the XLRS locus to an interval of approximately 3-4 cM. These results improve the feasibility of diagnosis in XLRS considerably, since carriers of this disease cannot be identified clinically.