Equidae is a small family which comprises horses, African and Asiatic asses, and zebras. Despite equids having diverged quite recently, their karyotypes underwent rapid evolution which resulted in extensive differences among chromosome complements in respective species. Comparative mapping using whole-chromosome painting probes delineated genome-wide chromosome homologies among extant equids, enabling us to trace chromosome rearrangements that occurred during evolution. In the present study, we performed subchromosomal comparative mapping among seven Equidae species, representing the whole family. Region-specific painting and bacterial artificial chromosome probes were used to determine the orientation of evolutionarily conserved segments with respect to centromere positions. This allowed assessment of the configuration of all fusions occurring during the evolution of Equidae, as well as revealing discrepancies in centromere location caused by centromere repositioning or inversions. Our results indicate that the prevailing type of fusion in Equidae is centric fusion. Tandem fusions of the type telomere-telomere occur almost exclusively in the karyotype of Hartmann's zebra and are characteristic of this species' evolution. We revealed inversions in segments homologous to horse chromosomes 3p/10p and 13 in zebras and confirmed inversions in segments 4/31 in African ass, 7 in horse and 8p/20 in zebras. Furthermore, our mapping results suggested that centromere repositioning events occurred in segments homologous to horse chromosomes 7, 8q, 10p and 19 in the African ass and an element homologous to horse chromosome 16 in Asiatic asses. Centromere repositioning in chromosome 1 resulted in three different chromosome types occurring in extant species. Heterozygosity of the centromere position of this chromosome was observed in the kiang. Other subtle changes in centromere position were described in several evolutionary conserved chromosomal segments, suggesting that tiny centromere repositioning or pericentric inversions are quite frequent in zebras and asses.

Department of Genetics and Reproduction Veterinary Research Institute Brno Czech Republic

See more in PubMed

Anim Genet. 2005 Dec;36(6):507-10 PubMed

Genomics. 2006 Jun;87(6):772-6 PubMed

Hereditas. 1995;123(3):269-74 PubMed

Chromosome Res. 2007;15(6):807-13 PubMed

Science. 2009 Nov 6;326(5954):865-7 PubMed

Nature. 2011 Jan 27;469(7331):529-33 PubMed

Chromosome Res. 2002;10(7):571-7 PubMed

Chromosome Res. 2008;16(1):89-107 PubMed

Mamm Genome. 2005 Aug;16(8):631-49 PubMed

Chromosome Res. 2002;10(7):527-34 PubMed

Chromosome Res. 2009;17(6):783-90 PubMed

Mol Biol Evol. 1986 Nov;3(6):535-46 PubMed

Cytogenet Genome Res. 2002;96(1-4):206-9 PubMed

Cytogenet Cell Genet. 2001;93(3-4):291-6 PubMed

Cytogenet Genome Res. 2009;126(1-2):165-72 PubMed

Cytogenet Genome Res. 2007;116(4):263-8 PubMed

Nat Rev Genet. 2007 Dec;8(12):950-62 PubMed

Cytogenet Cell Genet. 1978;20(1-6):332-50 PubMed

Proc Natl Acad Sci U S A. 2008 Sep 23;105(38):14477-81 PubMed

Cytogenet Genome Res. 2003;102(1-4):217-21 PubMed

Cytogenet Genome Res. 2003;102(1-4):235-43 PubMed

Cytogenet Genome Res. 2010;129(4):305-9 PubMed

Chromosome Res. 2000;8(8):659-70 PubMed

Cytogenet Genome Res. 2003;102(1-4):222-5 PubMed

Heredity (Edinb). 2012 Jan;108(1):59-67 PubMed

Chromosome Res. 2004;12(1):65-76 PubMed

J Anim Breed Genet. 2005 Apr;122 Suppl 1:78-86 PubMed

Cytogenet Cell Genet. 2001;93(1-2):127-30 PubMed

Cytogenet Genome Res. 2012;137(2-4):208-17 PubMed

PLoS Genet. 2010 Feb 12;6(2):e1000845 PubMed

Genomics. 2006 Jun;87(6):777-82 PubMed

Biotechniques. 1999 Aug;27(2):362-7 PubMed

J Mol Evol. 1998 Dec;47(6):772-83 PubMed

Comparative chromosome painting in Chacoan peccary, Catagonus wagneri