Putative fragile sites in the horse karyotype

The present study reports on the chromosomal expression and localization of aphidicolin-induced fragile sites in the standard karyotype of river buffalo (Bubalus bubalis, 2n = 50) with the aim of establishing a ‘fragile site map’ of the species. Totally, 400 aphidicolin-induced breakages were analyzed from eight young and clinically healthy animals, four males and four females; these breakages were localized in 106 RBG-negative chromosome bands or at the band-interband regions. The number of breakages per chromosome did not vary statistically ‘among’ the animals investigated but the differences among individual chromosomes were highly significant thus indicating that the chromosomal distribution of the breakages is not random and appears only partially related to chromosome length. Fragile sites were statistically determined as those chromosomal bands showing three or more breakages. In the river buffalo karyotype, 51 fragile sites were detected and localized on the standardized ideogram of the species. The most fragile bands were as follows: 9q213 with 24 breakages out of 400; 19q21 with 16, 17q21 and inacXq24 with 15, 15q23 with 13 and 13q23 with 12 breaks, respectively. Previous gene mapping analysis in this species has revealed that the closest loci to these fragile sites contain genes such as RASA1 and CAST (9q214), NPR3 and C9 (19q19), PLP and BTK (Xq24-q25), OarCP09 (15q24), and EDNRB (13q22) whose mutations are responsible for severe phenotypic malformations and immunodeficiency in humans as well as in mice and meat quality in pigs. Further cytogenetic and molecular studies are needed to fully exploit the biological significance of the fragile sites in karyotype evolution of domestic animals and their relationships with productive and reproductive efficiency of livestock.

mentioning

confidence: 99%

Chromosomal expression and localization of aphidicolin-induced fragile sites in the standard karyotype of river buffalo (Bubalus bubalis)

Nicodemo

Coppola²,

Pauciullo³

et al. 2008

“…The BrdU-sensitive fragile site, FRA13B, and aphidicolin-induced FRA13C, both localize to HSA13q21 [Hecht et al, 1990]. Fragility at this site was also observed in horses [Rønne, 1992] and in the cattle karyotype at the border between BTA12q22 and 12q23 [DiBerardino et al, 1983].…”

Section: Bovidaementioning

confidence: 82%

“…The table was constructed on the basis of comparative banding, cytogenetic map databases publicly available for each species, and previously published data. For example, conservation of a fragile site at HSAXq27 with horse, rabbit, and dog was suggested by Rønne [1992] along with shared fragility at Xq22 and HSA17q21/ECA13q21. Additional orthologous fragile sites have been described among primates, and between human and mouse [reviewed in Durkin and Glover, 2007;Helmrich et al, 2007].…”

Section: Domestic Animal Fragile Sitesmentioning

confidence: 99%

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Fragile Sites in Domestic Animal Chromosomes: Molecular Insights and Challenges

Riggs

Rønne²

2009

Fragile sites are intriguing cytogenetic phenomena that have been extensively investigated in human and laboratory animal chromosomes over the past 40 years, but domestic animal species have been studied sporadically. Interest in the field has been recently renewed as increasing numbers of fragile site regions are cloned and characterized at the molecular level. Despite much effort, mechanisms by which specific DNA sequence confers fragility to a chromosome region remain unclear. Recent advancements in sequencing and mapping of domestic animal genomes provide tools for molecular characterization of fragile sites in animal chromosomes. Future comparative efforts may contribute insight into both the mechanisms that underlie chromosome fragility, and forces that drive rearrangements observed throughout evolution, and somatic changes that can result in disease or impair fertility.

“…The breakpoint region just distal to the centromere on ECA16 is near the HSA3q:3p inversion boundary and may represent yet another fusion or fission site contributing to the evolution of ECA16. Rønne (1992) identified 12 putative fragile sites in the horse. While fragile sites were identified on ECA1, ECA4, and ECA16, none of these sites correspond with the breakpoints described in this report.…”

Section: Discussionmentioning

confidence: 99%

Three autosomal chromosome translocations associated with repeated early embryonic loss (REEL) in the domestic horse (Equus caballus)

Lear

Lundquist

Zent

et al. 2008

Repeated early embryonic loss (REEL) represents a considerable economic loss to the horse industry. Mares that experience REEL may be overlooked as poten- tial carriers of a chromosome abnormality. Here we report three different autosomal translocations in Thoroughbred mares presented for chromosome analysis because of REEL. The karyotypes were 64,XX,t(1;21), 64,XX,t(16;22), and 64,XX,t(4;13), respectively. In order to confirm the chromosomes involved in the translocations, to map the breakpoints, and to determine if the translocations were reciprocal, genes surrounding the breakpoints were identified using existing maps and from the newly assembled horse genome sequence. Bacterial artificial chromosomes containing the genes of interest were identified and mapped to the translocation chromosomes by fluorescence in situ hybridization (FISH). FISH confirmed that the t(16;22) and t(4;13) translocations were reciprocal, while the t(1;21) was not. The breakpoints on horse chromosomes 1 and 16 appear to be the same or near breakpoints previously identified in translocations. These breakpoints are at the fusion boundary of human chromosomes 10 and 15 on horse chromosome 1 and at human chromosome 3p and 3q on horse chromosome 16. These sites may represent ancient breakpoints reused during equid evolution. Overall, chromosome abnormalities may have a greater influence on mare fertility than previously known. Thus, it is important to karyotype subfertile mares exhibiting REEL.