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

Abstract

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.

Figure 1

RH map of the domestic cat X chromosome and comparisons with human and mouse X chromosomes. Feline RH intermarker distances are expressed in centirays (cR₅₀₀₀), whereas human markers are labeled with their centiray positions on the RH framework (cR₃₀₀₀). Markers ordered with odds ≥1000:1 are underlined and in bold-face, whereas markers ordered with odds ≥100:1 are in boldface type only. Human loci positioned previously by our laboratory (Chen et al., in prep.) or for this study are labeled with an F (Frederick). In cases of multiple discordant human RH map positions reported in the database, a range of centiray positions is given. Because of the highly rearranged nature of the mouse X chromosome compared to human and cat, mouse X loci have been positioned adjacent to their respective cat homologs for clarity, with map positions (in cM) labeled next to the locus name.

Figure 2

RH map of the domestic cat Y chromosome and comparisons with human and mouse Y chromosome physical maps. RH intermarker distances for the cat RH map are expressed in centirays (cR₅₀₀₀). Markers ordered with odds ≥1000:1 are underlined and in bold-face, whereas markers ordered with odds ≥100:1 are in bold-face type only. Human and mouse maps, based on information from Lahn and Page (1997) and Mazeyrat et al. (1998), are meant to be proportionate to intergenic spacing, yet they do not necessarily reflect true physical distances.