High-resolution mapping of probes near the X-linked lymphoproliferative disease (XLP) locus

Fluorescence in situ hybridization (FISH) was employed in high-resolution mapping of probes near the X-linked lymphoproliferative disease (XLP) locus. The map includes the DXS42, DXS12, DXS6, DXS982, DXS739, DXS75, DXS100, DXS10, and DXS177 loci. Metaphase analysis showed that DXS12 and DXS42 mapped to proximal Xq25, while DXS10 and DXS177 mapped to proximal Xq26.1. DXS6, DXS982, DXS739, DXS75, and DXS100 were in Xq25. The order of probes deduced from interphase FISH was: Xq24-(DXS12, DXS42)-DXS6-DXS982-DXS739-DXS75-DXS100+ ++-DXS10-DXS177-Xq26.2. We estimate that the entire region between DXS12 and DXS177 is about 7 Mb. Our previous study indicated that all three XLP deletions (63-3, 66-1, and 43-4) lacked DXS739. We now report that DXS75 and DXS982 are also missing in these deletions. Using interphase FISH measurements, we estimate that 2 Mb are absent in 63-3, and 4 Mb are absent in 66-1 and 43-4. This FISH map confines the XLP candidate gene region to a 2-Mb interval between DXS6 and DXS100 and places DXS100 distal to the XLP locus. This study also demonstrates that small probes (0.6 to 3.6 kb) can be utilized in FISH.