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Doctoral thesis, 1999

Comparative genome analysis in the horse

Raudsepp, Terje


Comparative genome analysis is one of the ways to investigate the equine genome. In the present work this was carried out by mapping specific genes to horse chromosomes and by detecting homologous chromosomal segments between horse and other species. Zoo-FISH on equine metaphase chromosomes using human whole chromosome painting probes (WCPs) for the first time delineated homologous segments between the karyotypes of the two species. The homology was further refined using microdissected chromosome arm specific paints (ASPs) for HSA2, 5, 6, 16 and 19. The Zoo-FISH studies serve as a basis to extrapolate and efficiently transfer gene mapping data from the advanced gene maps of human/mouse to that of the horse.
An important part of any genome mapping project is mapping ofspecific genes. In this thesis four genes were added to the horse physical map: IGF2 using an equine specific probe, and MC1R, KIT, PDGFRA using heterologous (porcine) probes. Successful use of heterologous large insert genomic BAC clones for the assignment of individual genes across distantly related species was the first such report in farm animals, and opens new avenues for developing comparative maps in the absence of species specific gene probes. The comparative gene mapping work was further extended to donkey - another equid species. These results represent the first mapping data in the donkey and provide interesting comparative information with the closely related horse genome.
Comparison between the karyotypes of the two equid species was expanded by generating fifteen microdissected equine chromosome specific probes (all meta- and submetacentric autosomes and the sex chromosomes) and hybridizing them to donkey metaphase chromosomes. Eight of the equine WCPs showed one-to-one correspondence with the donkey chromosomes, one to a single arm, while six to 2-3 arms on separate chromosomes. The results provided an insight into how the two genomes are organized in relation to each other, with respect to the equine chromosomes used in the present study. An important outcome of the results was indirect deduction of homology between human and donkey karyotypes. The latter gives a basis for comparison of the donkey genome with other mammalian species.
​​​​​​​Accumulating Zoo-FISH data between human and several non-primate species help to understand how different mammalian genomes are organized in relation to each other. Analysis of comparative chromosome painting data between distantly related species enabled identification of evolutionarily conserved whole chromosomes, large chromosomal segments and contiguous synteny combinations, that very likely comprise the karyotype of an eutherian ancestor. The equine genome comprises the focus for all investigations within the thesis, and therefore the results are discussed with special emphasis on the horse.


horse; human; Zoo-FISH; gene mapping; heterologous FISH; chromosome microdissection; donkey; karyotype evolution

Published in

Acta Universitatis Agriculturae Sueciae. Veterinaria
1999, number: 42
ISBN: 91-576-5405-0
Publisher: Swedish University of Agricultural Sciences

Authors' information

Raudsepp, Terje
Swedish University of Agricultural Sciences, Department of Animal Breeding and Genetics

UKÄ Subject classification

Genetics and Breeding

URI (permanent link to this page)