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SOS Rhino : In the News : Horse-rhino similarities discussed at genetics convention
 

Horse-rhino similarities discussed at genetics convention

  Joe Naiman
Village News Correspondent
Village News
www.thevillagenews.com

5/13/2005 2:20:51 PM

The similarities between horses and rhinoceroses were discussed as part of a pair of presentations at the Plant and Animal Genome conference January 15-19 in San Diego. Teri Lear of the University of Kentucky's Maxwell H. Gluck Equine Research Center gave a presentation titled "Using Horse Gene Mapping Tools to Study Chromosome Evolution in Perissodactyls" during the equine session January 16. Lear was joined by Marlys Houck, Dr. Oliver Ryder, and Julie Fronczek of the San Diego Zoological Society's Conservation and Research for Endangered Species and Judy Lundquist of the Gluck Equine Research Center in a poster presentation titled "Comparative Gene Mapping of Endangered Rhinoceros Species." The research was funded by the Morris Animal Foundation. Most rhinoceros species are endangered but have difficulty reproducing in captivity. The involvement of chromosomal factors in the poor reproductive rate of captive rhinos has not yet been determined. It is theorized that rhinos with incompatible or abnormal chromosomes may be bred inadvertently, resulting in fewer offspring. The order Perissodactyla includes both rhinoceroses and equids as well as tapirs, and the researchers mapped domestic horse genes to rhinoceros chromosomes. The use of 77 horse BAC clones representing all chromosomal arms allowed for the creation of comparative maps for the Indian, Sumatran, Northern White, Southern White, Northern Black, and Eastern Black rhinoceros species, and the work has identified a high degree of gene order conservation, both among different rhinoceros species and between the rhinoceros and the domestic horse. Equids have between 32 and 66 chromosomes while the various species of rhinoceros all have between 82 and 84 chromosomes (the Javan rhino species is too rare to have obtained genetic samples, so chromosomal information is not known for that species). The researchers undertook the study to see if they could identify differences between rhinoceros species. "We really haven't seen many differences at all," Houck said. "The genes are highly conserved." Centromere positions, however, are significantly different between rhinos and horses, possibly due to both inversions and centromere repositioning. That made the team's work more difficult. "The other thing we were trying to identify was the Y chromosome in the rhino group," Houck said. The researchers have been less successful in identifying that chromosome. "The sequence similarities might not be enough to get good hybridization with the horse gene probes that we are using," Lear said. "We will try to fill in the gaps in the comparative map." The work was funded by a two-year Morris Animal Foundation grant which began in 2003. "Hopefully in the next month we will have completed the project," Lear said. Lear was able to capitalize on previous horse genomics work. "It's nice that the horse genome is being developed," she said. "Not only does it give us information on how genomes evolve over millions of years of evolution, but it will also give us information on the differences between the genomes." In addition to possibly improving rhinoceros breeding efforts, the work may be of benefit to the equine community. "Because horses and rhinoceroses respond differently to infectious diseases, what we learn about differences in their genomes might give us insight on how to keep horses healthier," Lear said. Lear and Houck hope to expand the genetic research to the third family in the order Perissodactyla, the Tapiridae. "If we look at tapirs, we might see something similar to or intermediate to the equids or rhinoceroses," Lear said.

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