X-linked alpha-thalassemia/mental retardation syndrome. Linkage analysis in a new family further supports localization in proximal Xq.

Linkage analysis was performed in a three generation family with three males affected by the recently delineated X-linked form of alpha-thalassemia/mental retardation syndrome (ATR-X). Results are in agreement with the linkage study reported by Gibbons et al in 1992 and further confirm that the ATR-X gene is located in proximal Xq. Positive LOD scores were obtained for several markers situated in the pericentromeric region. A maximum LOD score of 2.09 at a recombination fraction of 0 was obtained for DXS453 located at the boundary q12-q13.1. The nearest flanking loci demonstrating recombination with the disease locus were AR at Xq11.2-q12 on the centromeric side and DXS72 at Xq21.1 on the telomeric side. Consequently the authors were able to reduce the previously defined candidate region for the gene location. Their results are compatible with a distal boundary at Xq21.1 instead of q21.31.