Linkage relationship of X-linked juvenile retinoschisis with Xp22.1-p22.3 probes

Linkage analysis was performed to evaluate the relationhip between the locus for X-linked juvenile retinoschisis (RS) and five X-chromosomal markers - RC8 (DXS9), SE3.2L (DXS16), 99-6 (DXS41), D2 (DXS43), and 782 (DXS85) - all mapped to the interval Xp22.1-p22.3. Seven U.S. families with 56 affected males were studied. No recombinants were found between RS and DXS9 with a maximum lod score (Z) of 4.93 at a recombination fraction of zero. Obligate recombinants were found for RS with DXS16, DXS41, DXS43, and DXS85. Multipoint linkage analysis and consideration of recombination events within pedigrees suggest that DXS41 and DXS43, and also DXS41 and DXS16, flank RS and that DXS85 lies outside the interval DXS41-DXS43. Our pedigrees provide no evidence for genetic heterogeneity of RS, with five of our families individually showing evidence of linkage (Z > 2.0) to at least one of these probes from Xp22.1-p22.3.