Mapping of dentin-specific acidic phosphoprotein and integrin-binding sialoprotein in sheep defines an inversion breakpoint with respect to human chromosome 4Q

Genes from sheep chromosome 6 map to human chromosome 4 in the region exten ding from 4p16 to 4q26, However, there is an inversion of gene order in the central portion of the chromosome with one breakpoint dose to secreted pho sphoprotein 1 (SPP1), Genes for SPP1, integrin-binding sialoprotein (IBSP) and dentin-specific acidic phosphoprotein (DMP1) are located close together in a YAC contig in the human. RFLP markers were developed for DMP1 and IBS P in sheep and located on the sheep linkage map to further define the break point region. There were no recombinants between SPP1 and IBSP indicating t hat these loci are dose together in sheep, as in humans. DMP1 was located a pproximately 80 cM from SPP1 in sheep, 7 cM from the microsatellite BMC4203 . In the human YAC contig, the order of these genes is SPP1-IBSP-DMP1 with 340 kb separating SPP1 and IBSP and 150 kb between IBSP and DMP1. Therefore , one breakpoint for the inversion in gene order between the sheep and the human has been narrowed to a region of 150 kb on the human map.