Partial deletions of a sequence family ("DXS278") and its physical linkage to steroid sulfatase as detected by pulsed-field gel electrophoresis.

pCRI-S232 (DXS278) is a 7-kb genomic sequence that hybridizes to multiple polymorphic X-linked restriction fragments on standard Southern analysis. Physical mapping of pCRI-S232 by pulsed-field gel electrophoresis (PFGE) suggests that a sequence in S232 is repeated in multiple X-chromosomal regions in normal individuals. Steroid sulfatase (STS) and DXS237 each hybridize to two of six X-linked SfiI fragments detected by S232. Two independent familial STS deletions, one of which is associated with a phenotype of ichthyosis plus ocular albinism (XI/OA1) and the other with nystagmus plus Rud syndrome, lack some but not all of the normal S232 PFGE fragments. We isolated a DNA fragment, E25B1.8, from a cosmid that contains S232. E25B1.8 detects a subset of the S232 polymorphic fragments on standard Southern blots plus new constant fragments; some, but not all, of the E25B1.8-hybridizing fragments are deleted in the XI/OA1 and Rud syndrome/nystagmus males. The simpler, but highly informative, polymorphism detected by E25B1.8 (DXS452) also eliminates an "intralocus" recombination seen with S232. We conclude that (1) males with STS deletions and complex phenotypes are partially deleted for DXS278, (2) DXS237 and part of DXS278 lie within 800 kb of STS, and (3) a repeat sequence within or around pCRI-S232 is probably located in multiple X-chromosomal locations spanning at least 2-3 Mb.