Repetitive sequences form a substantial and still enigmatic part of the mammalian genome. We isolated repetitive DNA blocks of the X chromosomes of three species of the family Bovidae: Kobus defassa (KDEXr sequence), Bos taurus (BTAXr sequence) and Antilope cervicapra (ACEXr sequence). The copy numbers of the isolated sequences were assessed using qPCR, and their chromosomal localisations were analysed using FISH in ten bovid tribes and in outgroup species. Besides their localisation on the X chromosome, their presence was also revealed on the Y chromosome and autosomes in several species. The KDEXr sequence abundant in most Bovidae species also occurs in distant taxa (Perissodactyla and Carnivora) and seems to be evolutionarily older than BTAXr and ACEXr. The ACEXr sequence, visible only in several Antilopini species using FISH, is probably the youngest, and arised in an ancestor common to Bovidae and Cervidae. All three repetitive sequences analysed in this study are interspersed among gene-rich regions on the X chromosomes, apparently preventing the crossing-over in their close vicinity. This study demonstrates that repetitive sequences on the X chromosomes have undergone a fast evolution, and their variation among related species can be beneficial for evolutionary studies.

• Keywords
• Bovidae, FISH, X chromosome, laser microdissection, qPCR, repetitive sequence, sequence analysis,
• MeSH
• Antelopes * genetics   MeSH
• Y Chromosome genetics   MeSH
• DNA MeSH
• Humans MeSH
• Chromosomes, Human, X MeSH
• Repetitive Sequences, Nucleic Acid genetics   MeSH
• Cattle genetics   MeSH
• Deer * genetics   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Cattle genetics   MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA MeSH

The recurrent occurrence of sex-autosome translocations during mammalian evolution suggests common mechanisms enabling a precise control of meiotic synapsis, recombination and inactivation of sex chromosomes. We used immunofluorescence and FISH to study the meiotic behaviour of sex chromosomes in six species of Bovidae with evolutionary sex-autosome translocations (Tragelaphus strepsiceros, Taurotragus oryx, Tragelaphus imberbis, Tragelaphus spekii, Gazella leptoceros and Nanger dama ruficollis). The autosomal regions of fused sex chromosomes showed normal synapsis with their homologous counterparts. Synapsis in the pseudoautosomal region (PAR) leads to the formation of characteristic bivalent (in T. imberbis and T. spekii with X;BTA13/Y;BTA13), trivalent (in T. strepsiceros and T. oryx with X/Y;BTA13 and G. leptoceros with X;BTA5/Y) and quadrivalent (in N. dama ruficollis with X;BTA5/Y;BTA16) structures at pachynema. However, when compared with other mammals, the number of pachynema lacking MLH1 foci in the PAR was relatively high, especially in T. imberbis and T. spekii, species with both sex chromosomes involved in sex autosome translocations. Meiotic transcriptional inactivation of the sex-autosome translocations assessed by γH2AX staining was restricted to their gonosomal regions. Despite intraspecies differences, the evolutionary fixation of sex-autosome translocations among bovids appears to involve general mechanisms ensuring sex chromosome pairing, synapsis, recombination and inactivation.

• Keywords
• Bovidae, Histone modification, Meiosis, Recombination, Sex-autosome translocation, Sex-chromosome inactivation, Synapsis, X chromosome, Y chromosome,
• MeSH
• Fluorescent Antibody Technique MeSH
• In Situ Hybridization, Fluorescence MeSH
• Chromosome Painting MeSH
• Meiosis genetics   MeSH
• Chromosome Pairing genetics   MeSH
• Sex Chromosomes genetics   MeSH
• Ruminants genetics   MeSH
• Chromosome Segregation genetics   MeSH
• Translocation, Genetic * MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Satellite sequences present in the centromeric and pericentric regions of chromosomes represent useful source of information. Changes in satellite DNA composition may coincide with the speciation and serve as valuable markers of phylogenetic relationships. Here, we examined satellite DNA clones isolated by laser microdissection of centromeric regions of 38 bovid species and categorized them into three types. Sat I sequences from members of Bovini/Tragelaphini/Boselaphini are similar to the well-documented 1.715 sat I DNA family. Sat I DNA from Caprini/Alcelaphini/Hippotragini/Reduncini/Aepycerotini/Cephalophini/Antilopini/Neotragini/Oreotragini form the second group homologous to the common 1.714 sat I DNA. The analysis of sat II DNAs isolated in our study confirmed conservativeness of these sequences within Bovidae. Newly described centromeric clones from Madoqua kirkii and Strepsiceros strepsiceros were similar in length and repetitive tandem arrangement but showed no similarity to any other satellite DNA in the GenBank database. Phylogenetic analysis of sat I sequences isolated in our study from 38 bovid species enabled the description of relationships at the subfamily and tribal levels. The maximum likelihood and Bayesian inference analyses showed a basal position of sequences from Oreotragini in the subfamily Antilopinae. According to the Bayesian inference analysis based on the indels in a partitioned mixed model, Antilopinae satellite DNA split into two groups with those from Neotragini as a basal tribe, followed by a stepwise, successive branching of Cephalophini, Aepycerotini and Antilopini sequences. In the second group, Reduncini sequences were basal followed by Caprini, Alcelaphini and Hippotragini.

• MeSH
• Species Specificity MeSH
• Phylogeny * MeSH
• Genetic Variation MeSH
• Animals, Domestic MeSH
• In Situ Hybridization, Fluorescence MeSH
• Molecular Sequence Data MeSH
• Repetitive Sequences, Nucleic Acid genetics   MeSH
• DNA, Satellite genetics   MeSH
• Base Sequence MeSH
• Sequence Analysis, DNA MeSH
• Sequence Homology, Nucleic Acid MeSH
• Cattle genetics   MeSH
• Animals MeSH
• Check Tag
• Cattle genetics   MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA, Satellite MeSH

In this study, we investigated repetitive sequences localized on Y chromosomes. Repetitive DNA sequences represent a substantial part of the eukaryotic genome and, among them, a large portion comprises sequences repeated in tandem. Efficient and rapid isolation of repeat units is possible due to a laser microdissection technique used for Y chromosome separation, followed by polymerase chain reaction (PCR), cloning, and sequence analysis. We applied the derived repeat units to members of nine tribes within the Bovidae. Apart from the Y chromosomes of Bos taurus and Bubalus bubalis, where we used known sequences of repetition, the derived sequences were used as probes for fluorescent in situ cross-hybridization to members of the nine tribes of the Bovidae. We investigated the distribution of repeat units within the tribes and their localization on the Y chromosome. Sharing of sequence variants would indicate common descent, while the rapid horizontal evolution should allow discrimination between closely related species or subspecies.

• MeSH
• Y Chromosome chemistry   genetics   MeSH
• Species Specificity MeSH
• Fluorescent Dyes chemistry   MeSH
• Phylogeny MeSH
• In Situ Hybridization, Fluorescence veterinary   MeSH
• Laser Capture Microdissection methods   veterinary   MeSH
• Metaphase MeSH
• Evolution, Molecular MeSH
• Genetics, Population methods   MeSH
• Repetitive Sequences, Nucleic Acid * MeSH
• Base Sequence MeSH
• Sequence Analysis, DNA methods   veterinary   MeSH
• Sequence Alignment MeSH
• Sex Factors MeSH
• Cattle classification   genetics   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Cattle classification   genetics   MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Fluorescent Dyes MeSH