Pulsed-field gel electrophoresis and radiation hybrid mapping analyses enable the ordering of eleven DNA loci in Xq22.

The Xq22 region of the human X chromosome encompasses the loci of several genes and random DNA markers whose relative positions have not been determined. By a combination of PFGE mapping and the analysis of a selected panel of X chromosome radiation hybrid cell lines, we have constructed physical maps of Xq22 that order a total of 11 polymorphic and nonpolymorphic DNA markers. Ten of these probes have been linked physically into three separate clusters, spanning nearly 6 Mb of DNA in total. The DXS94, DXS147, DXS211, DXS17, and DXS87 loci are all present on a 2.7-Mb MluI fragment; PLP, DXS54, DXS24, and DXS83 are present on MluI fragments spanning over 1.6 Mb; and DXS178 is present on a 1.5-Mb MluI fragment. Mapping with additional enzymes has allowed the further ordering of these loci with respect to each other. Together with these data, analysis of a small set of radiation hybrids has suggested the following over-all order of loci within Xq22: centromere-DXS178-DXS94-DXS147-DXS211-DXS17++ +-DXS87- PLP-DXS54-DXS24-DXS83-COL4A5-telomere. The ordering of these random DNA markers, genes, and disease loci, including the genes responsible for Pelizaeus-Merzbacher disease and Alport syndrome, indicates DNA markers that could be of further use clinically for these diseases. Furthermore, this map should form a basis for the refinement of additional disease-associated loci in this region.