Genome Diversity and the Origin of the Arabian Horse

The Arabian horse, one of the world\u27s oldest breeds of any domesticated animal, is characterized by natural beauty, graceful movement, athletic endurance, and, as a result of its development in the arid Middle East, the ability to thrive in a hot, dry environment. Here we studied 378 Arabian horses from 12 countries using equine single nucleotide polymorphism (SNP) arrays and whole-genome re-sequencing to examine hypotheses about genomic diversity, population structure, and the relationship of the Arabian to other horse breeds. We identified a high degree of genetic variation and complex ancestry in Arabian horses from the Middle East region. Also, contrary to popular belief, we could detect no significant genomic contribution of the Arabian breed to the Thoroughbred racehorse, including Y chromosome ancestry. However, we found strong evidence for recent interbreeding of Thoroughbreds with Arabians used for flat-racing competitions. Genetic signatures suggestive of selective sweeps across the Arabian breed contain candidate genes for combating oxidative damage during exercise, and within the Straight Egyptian subgroup, for facial morphology. Overall, our data support an origin of the Arabian horse in the Middle East, no evidence for reduced global genetic diversity across the breed, and unique genetic adaptations for both physiology and conformation

Y-Chromosomal Insights into Breeding History and Sire Line Genealogies of Arabian Horses

The Y chromosome is a valuable genetic marker for studying the origin and influence of paternal lineages in populations. In this study, we conducted Y-chromosomal lineage-tracing in Arabian horses. First, we resolved a Y haplotype phylogeny based on the next generation sequencing data of 157 males from several breeds. Y-chromosomal haplotypes specific for Arabian horses were inferred by genotyping a collection of 145 males representing most Arabian sire lines that are active around the globe. These lines formed three discrete haplogroups, and the same haplogroups were detected in Arabian populations native to the Middle East. The Arabian haplotypes were clearly distinct from the ones detected in Akhal Tekes, Turkoman horses, and the progeny of two Thoroughbred foundation sires. However, a haplotype introduced into the English Thoroughbred by the stallion Byerley Turk (1680), was shared among Arabians, Turkomans, and Akhal Tekes, which opens a discussion about the historic connections between Oriental horse types. Furthermore, we genetically traced Arabian sire line breeding in the Western World over the past 200 years. This confirmed a strong selection for relatively few male lineages and uncovered incongruences to written pedigree records. Overall, we demonstrate how fine-scaled Y-analysis contributes to a better understanding of the historical development of horse breeds.Peer Reviewe

Refining the evolutionary tree of the horse Y chromosome

The Y chromosome carries information about the demography of paternal lineages, and thus, can prove invaluable for retracing both the evolutionary trajectory of wild animals and the breeding history of domesticates. In horses, the Y chromosome shows a limited, but highly informative, sequence diversity, supporting the increasing breeding influence of Oriental lineages during the last 1500 years. Here, we augment the primary horse Y-phylogeny, which is currently mainly based on modern horse breeds of economic interest, with haplotypes (HT) segregating in remote horse populations around the world. We analyze target enriched sequencing data of 5 Mb of the Y chromosome from 76 domestic males, together with 89 whole genome sequenced domestic males and five Przewalski's horses from previous studies. The resulting phylogeny comprises 153 HTs defined by 2966 variants and offers unprecedented resolution into the history of horse paternal lineages. It reveals the presence of a remarkable number of previously unknown haplogroups in Mongolian horses and insular populations. Phylogenetic placement of HTs retrieved from 163 archaeological specimens further indicates that most of the present-day Y-chromosomal variation evolved after the domestication process that started around 4200 years ago in the Western Eurasian steppes. Our comprehensive phylogeny significantly reduces ascertainment bias and constitutes a robust evolutionary framework for analyzing horse population dynamics and diversity

Molecular characterization of the apoptosis-related SH3RF1 and SH3RF2 genes and their association with exercise performance in Arabian horses

Abstract Background Apoptosis plays an important role in the regulation of healthy tissue growth and development as well as in controlling the maintenance of homeostasis in exercising muscles. During an intensive physical effort, the regulation of cell death by apoptosis results in the replacement of unaccustomed muscle cells by new cells that are better suited to exercise. The aim of this study was to determine the expression of two genes (SH3FR1 and SH3RF2) that control apoptosis in muscle tissues during training periods characterized by different intensities. The gene expression levels were estimated using real-time PCR method in skeletal muscle biopsies collected from 15 Arabian horses (untrained, after an intense gallop phase, and at the end of the racing season). An association study was performed on 250 Arabian horses to assess the effect of the SH3RF2:c.796 T > C (p.Ser266Pro) variant on race performance traits in flat gallop-racing. Results A gene expression analysis confirmed a significant decrease (p  C missense variant was associated with selected racing performance traits, which is important information during the evaluation of horses’ exercise predisposition. The association results and frequencies of the CT and TT genotypes suggest the possibility of using SH3RF2 variant in selection to improve the racing performance of Arabian horses

Wpływ różnych czynników na poziom alfa1-antytrypsyny u żrebiąt pełnej krwi angielskiej

Acute phase proteins (APP) are an integral part of the acute phase response. Alpha 1 antitrypsin is considered to be one of the most important acute-phase protein activated by trauma, stress, or inflammatory processes. The objective of the present study was to estimate the impact of various factors (sex, month of life and sire effect) on concentration of alpha 1 antitrypsin in serum of Thoroughbred foals. A total of 624 samples, collected from 39 foals were obtained in monthly intervals from first to 16 month of life and measured by STIC method (specific trypsin inhibitory captivity). The obtained results indicated the significant impact of analyzed age periods on the AAT level. Furthermore, the variation in AAT level in analyzed periods corresponded to significant changes in foals diet and maintaining. Alpha 1 antitrypsin concentration was also affected by sire effects and sex of foals. In the most investigated age periods, the impact of sire on alpha 1 antitrypsin content in serum of his progeny has been shown. The obtained results might be useful in explanation of differences in serum AAT concentration in foals during early ontogenesis which probably is a critical period that has an influence on racing performance of young horses.Wpływ różnych czynników na poziom alfa-1-antytrypsyny u źrebiąt pełnej krwi angielskiej. Białka ostrej fazy (APP) są integralną częścią tzw.: odpowiedzi ostrej fazy na stan zapalny. Alfa-1-antytrypsyna (ATT) jest uważana za jedno najważniejszych białek ostrej fazy aktywowane przez uraz, stres lub procesy zapalne. W związku z tym celem niniejszego badania była ocena wpływu różnych czynników (płeć, miesiąc życia i ojciec) na stężenia ATT w surowicy krwi źrebiąt pełnej krwi angielskiej. Materiał do badań stanowiło 624 próbek kri, zebranych od 39 źrebiąt będących potomstwem czterech ogierów, uzyskanych w odstępach miesięcznych od pierwszego do 16 miesiąca życia. Stężenie ATT oznaczono metodą STIC. Uzyskane wyniki wskazały na znaczący wpływ wieku źrebiąt na poziom AAT. Co więcej, różnice w poziomie AAT w analizowanych okresach przypadały w okresach znaczących zmian u źrebiąt. Ponadto w większości badanych okresów, wykazano wpływ ojca na stężenie ATT u potomstwa. Uzyskane wyniki mogą być przydatne w celu wyjaśnienia różnic w koncentracji AAT w surowicy krwi u źrebiąt w okresie wczesnej ontogenezy która jest krytycznym okresem, mającym wpływ na wyniki użytkowe młodych koni

Genome Diversity and the Origin of the Arabian Horse

Abstract The Arabian horse, one of the world’s oldest breeds of any domesticated animal, is characterized by natural beauty, graceful movement, athletic endurance, and, as a result of its development in the arid Middle East, the ability to thrive in a hot, dry environment. Here we studied 378 Arabian horses from 12 countries using equine single nucleotide polymorphism (SNP) arrays and whole-genome re-sequencing to examine hypotheses about genomic diversity, population structure, and the relationship of the Arabian to other horse breeds. We identified a high degree of genetic variation and complex ancestry in Arabian horses from the Middle East region. Also, contrary to popular belief, we could detect no significant genomic contribution of the Arabian breed to the Thoroughbred racehorse, including Y chromosome ancestry. However, we found strong evidence for recent interbreeding of Thoroughbreds with Arabians used for flat-racing competitions. Genetic signatures suggestive of selective sweeps across the Arabian breed contain candidate genes for combating oxidative damage during exercise, and within the “Straight Egyptian” subgroup, for facial morphology. Overall, our data support an origin of the Arabian horse in the Middle East, no evidence for reduced global genetic diversity across the breed, and unique genetic adaptations for both physiology and conformation