Extensive conservation of sex chromosome organization between cat and human revealed by parallel radiation hybrid mapping.

A radiation hybrid (RH)-derived physical map of 25 markers on the feline X chromosome (including 19 Type I coding loci and 6 Type II microsatellite markers) was compared to homologous marker order on the human and mouse X chromosome maps. Complete conservation of synteny and marker order was observed between feline and human X chromosomes, whereas the same markers identified a minimum of seven rearranged syntenic segments between mouse and cat/human X chromosome marker order. Within the blocks, the feline, human, and mouse marker order was strongly conserved. Similarly, Y chromosome locus order was remarkably conserved between cat and human Y chromosomes, with only one marker (SMCY) position rearranged between the species. Tight linkage and a conserved gene order for a segment encoding three genes, DFFRY-DBY-UTY in human, mouse, and cat Y chromosomes, coupled with demonstrated deletion effects of these genes on reproductive impairment in both human and mouse, implicates the region as critical for Y-mediated sperm production.