A 4.3 Mb YAC Contig in Human Xp11.2: Long-Range Restriction Mapping and Identification of CpG Islands.

The Xp11.2 region o the human X chromosome contains genes involved in a number of inherited diseased, with at least one locus that escapes X chromosome inactivation, as well as abnormal methylation polymorphism. We isolated a series of yeast artificial chromosome (YAC) clones by hybridization screening with DNA probes localized within this region and assembled them into a 4.3 Mb contig spanning from Xp11.21 to Xp11.23 by a combination of Alu-PCR fingerprinting, STS-PCR and DNA probe cross hybridization. On the basis of these overlapping YAC clones we have constructed the long-range restriction map of this interval and placed exactly some DNA markers. Four CpG-dense regions between ARAF1 and OATL2 were identified based on the long-range restriction mapping, which indicated the distribution of genes within this interval. It should assist in the future nucleic acid sequence analysis and novel gene identification in this region.

Construction and Physical Mapping of the 35 cM YAC Contigs for the Region of Xp11.2 - p21.3.

One hundred and fifty-one YACs were selected from three libraries with a series of STS and other DNA probes of the human X chromosome p11.2 - p21.3 region. The YAC contigs, spanning about 35cM in all and generally cover the whole region, were constructed based on the physical analysis of the positive clones. A total of seventy-seven DNA markers of this region were located and ordered on this map with an average 454 kb spacing, in which fifty-three were polymorphic markers with an average 0.6 cM genetic spacing. These results facilitate the search for novel genes and the sequence analysis of this region.