Abstract: The interspersed repeat content of mammalian genomes has been best characterized in human, mouse and cow. In this study, we carried out de novo identification of repeated elements in the equine genome and identified previously unknown elements present at low copy number. The equine genome contains typical eutherian mammal repeats, but also has a significant number of hybrid repeats in addition to clade-specific Long Interspersed Nuclear Elements (LINE). Equus caballus clade specific LINE 1 (L1) repeats can be classified into approximately five subfamilies, three of which have undergone significant expansion. There are 1115 full-length copies of these equine L1, but of the 103 presumptive active copies, 93 fall within a single subfamily, indicating a rapid recent expansion of this subfamily. We also analysed both interspersed and simple sequence repeats (SSR) genome-wide, finding that some repeat classes are spatially correlated with each other as well as with G+C content and gene density. Based on these spatial correlations, we have confirmed that recently-described ancestral vs. clade-specific genome territories can be defined by their repeat content. The clade-specific Short Interspersed Nuclear Element correlations were scattered over the genome and appear to have been extensively remodelled. In contrast, territories enriched for ancestral repeats tended to be contiguous domains. To determine if the latter territories were evolutionarily conserved, we compared these results with a similar analysis of the human genome, and observed similar ancestral repeat enriched domains. These results indicate that ancestral, evolutionarily conserved mammalian genome territories can be identified on the basis of repeat content alone. Interspersed repeats of different ages appear to be analogous to geologic strata, allowing identification of ancient vs. newly remodelled regions of mammalian genomes.
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This study investigates the diversity and distribution of repeated elements within the horse genome, finding that these can indicate conserved chromosomal areas and reveal information about the horse’s evolutionary history.
Research Goals
The core aim of the research was to identify and understand the interspersed repeat elements in the horse (Equus caballus) genome.
The study also sought to identify any unknown repeat elements in the equine genome and ascertain their characteristics.
An investigation into how repeat classes relate spatially with each other, gene density, and G+C content was conducted.
The research attempted to confirm whether ancestral or clade-specific genome territories defined by their repeat content existed.
Findings
The horse genome contains typical eutherian mammal repeats and a significant number of hybrid repeats. It also possesses clade-specific Long Interspersed Nuclear Elements (LINE).
The researchers identified five subfamilies of Equus caballus clade specific LINE 1 (L1) repeats. Three of these subfamilies had notably expanded.
Out of 103 active copies of equine L1, 93 belonged to a single subfamily, indicating a recent rapid expansion.
Analysis showed that some repeat classes are spatially correlated with each other, gene density, and G+C content.
Ancient territories of the genome were consecutive, while newer territories were scattered throughout the genome, suggesting they had been extensively remodelled.
Comparison with the human genome yielded similar results, indicating that these territories are evolutionarily conserved within mammals and can be identified through their repeat content.
Significance
The research illustrates how the investigation of interspersed repeats in a genome can provide insights into the evolutionary history of a species.
The existence of particular repeated elements within the horse genome can provide essential information on the evolutionary dynamics of genome remodeling, such as identifying ‘new’ and ‘old’ regions of the genome.
Cite This Article
APA
Adelson DL, Raison JM, Garber M, Edgar RC.
(2010).
Interspersed repeats in the horse (Equus caballus); spatial correlations highlight conserved chromosomal domains.
Anim Genet, 41 Suppl 2, 91-99.
https://doi.org/10.1111/j.1365-2052.2010.02115.x
School of Molecular and Biomedical Science, University of Adelaide, North Terrace, Adelaide, South Australia, Australia. david.adelson@adelaide.edu.au
Raison, J M
Garber, M
Edgar, R C
MeSH Terms
Animals
Base Composition
Chromosomes, Mammalian
Genome
Horses / genetics
Microsatellite Repeats
Retroelements
Citations
This article has been cited 11 times.
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