High-resolution gene maps of individual equine chromosomes are essential to identify genes governing traits of economic importance in the horse. In pursuit of this goal we herein report the generation of a dense map of horse chromosome 22 (ECA22) comprising 83 markers, of which 52 represent specific genes and 31 are microsatellites. The map spans 831 cR over an estimated 64 Mb of physical length of the chromosome, thus providing markers at ∼770 kb or 10 cR intervals. Overall, the resolution of the map is to date the densest in the horse and is the highest for any of the domesticated animal species for which annotated sequence data are not yet available. Comparative analysis showed that ECA22 shares remarkable conservation of gene order along the entire length of dog chromosome 24, something not yet found for an autosome in evolutionarily diverged species. Comparison with human, mouse, and rat homologues shows that ECA22 can be traced as two conserved linkage blocks, each related to individual arms of the human homologue-HSA20. Extending the comparison to the chicken genome showed that one of the ECA22 blocks that corresponds to HSA20q shares synteny conservation with chicken chromosome 20, suggesting the segment to be ancestral in mammals and birds.
Bibliographical noteFunding Information:
This project was funded by grants from the Texas Higher Education Board (ARP 010366-0162-2001, B.P.C.; ATP 000517-0306-2003, B.P.C., J.E.W.), NRICGP/USDA Grant 2003-03687 (B.P.C.), the Texas Equine Research Foundation (B.P.C., L.C.S.), the Link Endowment (B.P.C., L.C.S.), the American Quarter Horse Association, and the Dorothy Russell Havemeyer Foundation. Additional support was available from the USDA-NRSP-8 Coordinators Fund. We thank Dr. Pat Venta, Michigan State University, for design and supply of several primer pairs.
- Comparative map
- Gene mapping
- RH map