REFINEMENT OF THE CHROMOSOMAL POSITION OF THE X-LINKED JUVENILE RETINOSCHISIS GENE

Linkage analysis was carried out in seven X linked juvenile retinoschi sis (XLRS) families using four DNA probes and four CA repeat polymorph isms 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 m ax= 0.05, Zmax=3.26). The analysis of recombination breakpoints and mu ltipoint linkage analysis suggests the order Xpter-DXS16-(DXS43, DXS20 7)-RS-DXS365-(DXS451, DXS41)-Xcen, thereby refining the position of th e XLRS locus to an interval of approximately 3-4 cM. These results imp rove the feasibility of diagnosis in XLRS considerably, since carriers of this disease cannot be identified clinically.