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Topic:Genetics
Genetics in horses encompasses the study of hereditary traits and the genetic makeup that influences various characteristics and health conditions in equine populations. This field involves the analysis of genes and their functions, inheritance patterns, and the impact of genetic variations on traits such as coat color, performance ability, and susceptibility to diseases. Research in equine genetics employs techniques such as genome mapping, sequencing, and genetic testing to identify specific genes and mutations associated with these traits. This page gathers peer-reviewed research studies and scholarly articles that explore the genetic basis of equine traits, the methodologies used in genetic research, and the implications for breeding, health management, and conservation of horse breeds.
Cytosine methylation of sperm DNA in horse semen after cryopreservation. Semen processing may contribute to epigenetic changes in spermatozoa. We have therefore addressed changes in sperm DNA cytosine methylation induced by cryopreservation of stallion semen. The relative amount of 5-methylcytosine relative to the genomic cytosine content of sperm DNA was analyzed by ELISA. In experiment 1, raw semen (n = 6 stallions, one ejaculate each) was shock-frozen. Postthaw semen motility and membrane integrity were completely absent, whereas DNA methylation was similar in raw (0.4 ± 0.2%) and shock-frozen (0.3 ± 0.1%) semen (not significant). In experiment 2, three ej...
Type of Inflammation Differentially Affects Expression of Interleukin 1β and 6, Tumor Necrosis Factor-α and Toll-Like Receptors in Subclinical Endometritis in Mares. Mares that fail to conceive or lose their embryos, without showing typical signs of clinical endometritis, should be suspected of subclinical endometritis (SE). In this study, the question was addressed: does SE fully activate selected mechanisms of innate immunity in mares? For this aim, expression of mRNAs for Toll-like Receptor 2 and 4 (TLR 2/4), interleukin 1β (IL-1β), interleukin 6 (IL-6) and tumor necrosis factor α (TNF) was examined in control mares versus either mares suffering from chronic endometritis (ChE) or subacute suppurative endometritis (SSE). The concentrations of IL-1β, ...
Host genetic influence on papillomavirus-induced tumors in the horse. The common equine skin tumors known as sarcoids have been causally associated with infection by bovine papillomavirus (BPV). Additionally, there is evidence for host genetic susceptibility to sarcoids. We investigated the genetic basis of susceptibility to sarcoid tumors on a cohort of 82 affected horses and 270 controls genotyped on a genome-wide platform and two custom panels. A Genome Wide Association Study (GWAS) identified candidate regions on six chromosomes. Bayesian probability analysis of the same dataset verified only the regions on equine chromosomes (ECA) 20 and 22. Fine mapping us...
Genome-wide association mapping of heritable temperament variation in the Tennessee Walking Horse. Temperament is a key criterion in the selection of horses for both leisure and competitive riding to ensure optimal performance and safety. The Tennessee Walking Horse (TWH) is described as a calm, docile breed and is often used as a trail, show and pleasure horse. However, among horse owners and caretakers, there are anecdotes supporting familial and disciplinal typical behaviors and personalities. To investigate the contribution of genetics to temperament, we collected a behavior questionnaire, brief training history and identifying information for 276 TWH, as well as blood or hair samples f...
Loci impacting polymorphic gait in the Tennessee Walking Horse. Following domestication, man selected the horse primarily for the purpose of transportation rather than consumption; this selective strategy created divergent traits for locomotion. At intermediate speeds, beyond the flat walk, the horse can perform a range of diagonal and lateral 2-beat or 4-beat gait patterns. The Tennessee Walking Horse (TWH) is the only U.S. breed able to perform an even-timed 4-beat gait (the "running-walk") at intermediate speeds; however, within the breed, there is remaining variation in gait type. To investigate the contribution of genetics to this unique trait, blood ...
Is Malassezia nana the main species in horses’ ear canal microbiome? The objective of this study was to characterize genotypically Malassezia spp. isolated from the external ear canal of healthy horses. Fifty-five horses, 39 (70.9%) males and 16 (29.1%) females, from different breeds and adults were studied. External ear canals were cleaned and a sterile cotton swab was introduced to collect cerumen. A total of 110 samples were cultured into Dixon medium and were incubated at 32°C for up to 15 days. Macro- and micromorphology and phenotypic identification were performed. DNA was extracted, strains were submitted to polymerase chain reaction technique, and the ...
Proteome of equine oviducal fluid: effects of ovulation and pregnancy. The equine oviduct plays a pivotal role in providing the optimal microenvironment for early embryonic development, but little is known about the protein composition of the oviducal fluid in the horse. The aim of the present study was to provide a large-scale identification of proteins in equine oviducal fluid and to determine the effects of ovulation and pregnancy. Four days after ovulation, the oviducts ipsilateral and contralateral to the ovulation side were collected from five pregnant and five non-pregnant mares. Identification and relative quantification of proteins in the oviducal fluid ...
Revelation of Influencing Factors in Overall Codon Usage Bias of Equine Influenza Viruses. Equine influenza viruses (EIVs) of H3N8 subtype are culprits of severe acute respiratory infections in horses, and are still responsible for significant outbreaks worldwide. Adaptability of influenza viruses to a particular host is significantly influenced by their codon usage preference, due to an absolute dependence on the host cellular machinery for their replication. In the present study, we analyzed genome-wide codon usage patterns in 92 EIV strains, including both H3N8 and H7N7 subtypes by computing several codon usage indices and applying multivariate statistical methods. Relative synon...
Genetic relationship between the Nordestino horse and national and international horse breeds. Knowledge of genetic diversity and relationships between breeds is very important for conservation programs. Hair samples were collected from 393 individual Nordestino horses and genotyped using 14 microsatellite markers in order to investigate the genetic relationship between this breed and 66 international horse breeds. There was high allelic diversity and inbreeding coefficient within population values were not significant, which was probably due to crossbreeding. Despite the Nordestino horse population being in Hardy-Weinberg equilibrium, a global deficit of heterozygotes was observed. Thi...
In vitro production of Trypanosoma equiperdum antigen and its evaluation for use in serodiagnosis of dourine. A modified Baltz's in vitro cultivation system for the propagation of Trypanosoma equiperdum strain OVI was established to develop a replacement for the conventional production procedure of dourine diagnostic antigen in rats. To increase trypanosome yields we designed an optimized culture medium by addition of supplemental compounds. Trypanosomes were adapted to this medium by two succeeding cultivation steps which led to a substantial proliferation rate and an increased cell density tolerance, respectively. As a result, adapted parasites could be propagated to maximum cell densities of >2...
Stenamoeba polymorpha, a New Species Isolated from Domesticated Horse Equus ferus caballus. A new species of lobosean amoeba, Stenamoeba polymorpha n. sp., was isolated from the diarrheic stool of a domesticated horse in Great Falls Virginia, U.S. It shares characteristics with the five other described Stenamoeba species. However, electron microscopy revealed S. polymorpha has a substantially thickened cell surface lamina. Under light microscopy, the amoebae had a dynamic polymorphic appearance because hyaloplasm readily formed and resorbed subpseudopodia from any peripheral region of the cell. While in locomotion, the amoebae produced subpseudopodia that led and alternated the dire...
Embryo-maternal communication during the first 4 weeks of equine pregnancy. The first month of equine pregnancy covers a period of rapid growth and development, during which the single-cell zygote metamorphoses into an embryo with a functional circulation and precursors of many important organs, enclosed within extraembryonic membranes responsible for nutrient uptake and gaseous exchange. After exiting the oviduct, the conceptus must influence uterine physiology to ensure adequate nutrition and preparation for implantation, while continued development results in the chorioallantois superseding the yolk sac as the primary interface for maternal interaction and exchange...
Genetic variability of the equine casein genes. The casein genes are known to be highly variable in typical dairy species, such as cattle and goat, but the knowledge about equine casein genes is limited. Nevertheless, mare milk production and consumption is gaining importance because of its high nutritive value, use in naturopathy, and hypoallergenic properties with respect to cow milk protein allergies. In the current study, the open reading frames of the 4 casein genes CSN1S1 (αS1-casein), CSN2 (β-casein), CSN1S2 (αS2-casein), and CSN3 (κ-casein) were resequenced in 253 horses of 14 breeds. The analysis revealed 21 nonsynonymous nucle...
The microbiome associated with equine periodontitis and oral health. Equine periodontal disease is a common and painful condition and its severe form, periodontitis, can lead to tooth loss. Its aetiopathogenesis remains poorly understood despite recent increased awareness of this disorder amongst the veterinary profession. Bacteria have been found to be causative agents of the disease in other species, but current understanding of their role in equine periodontitis is extremely limited. The aim of this study was to use high-throughput sequencing to identify the microbiome associated with equine periodontitis and oral health. Subgingival plaque samples from 24 h...
Screening of whole genome sequences identified high-impact variants for stallion fertility. Stallion fertility is an economically important trait due to the increase of artificial insemination in horses. The availability of whole genome sequence data facilitates identification of rare high-impact variants contributing to stallion fertility. The aim of our study was to genotype rare high-impact variants retrieved from next-generation sequencing (NGS)-data of 11 horses in order to unravel harmful genetic variants in large samples of stallions. Methods: Gene ontology (GO) terms and search results from public databases were used to obtain a comprehensive list of human und mice genes pred...
Missense Mutation in the Ligand-Binding Domain of the Horse Androgen Receptor Gene in a Thoroughbred Family with Inherited 64,XY (SRY+) Disorder of Sex Development. Disorders of sex development (DSD) have long been documented in domestic animal species including horses. However, there is only a single report of an androgen receptor (AR) mutation causative of such a DSD syndrome in a horse pedigree. Here, we present a new familial AR mutation in horses. A missense mutation (c.2042G>C) at AR exon 4 explains the segregation of the DSD in a Thoroughbred horse pedigree. The mutation, expected to affect the ligand-binding domain of the AR protein, led to complete androgen insensitivity of 64,XY SRY+, testicular DSD individuals. Additionally, the design of a ...
The origin of Chinese domestic horses revealed with novel mtDNA variants. The origin of domestic horses in China was a controversial issue and several hypotheses including autochthonous domestication, introduction from other areas, and multiple-origins from both introduction and local wild horse introgression have been proposed, but none of them have been fully supported by DNA data. In the present study, mitochondrial DNA (mtDNA) sequences of 714 Chinese indigenous horses were analyzed. The results showed that Chinese domestic horses harbor some novel mtDNA haplogroups and suggested that local domestication events may have occurred, but they are not the dominant ha...
Plasmid Profiles of Virulent Rhodococcus equi Strains Isolated from Infected Foals in Poland. Rhodococcus equi is an important bacterial pathogen in foals up to 6 months old, widespread in horse farms all over the world. It was found that only virulent R. equi strains expressing 15-17 kDa virulence-associated protein (VapA) and having large virulence plasmid of 85-90 kb containing vapA gene are pathogenic for horses. To date, 12 plasmid types have been reported in VapA positive strains from horses. There are no data concerning plasmid types of Polish field R. equi strains isolated from horses and horse farm environment. The aim of the study is to determine plasmid profiles of virulent ...
Identification of genes with nonsynonymous SNP in Jeju horse by whole-genome resequencing reveals a functional role for immune response. Jeju horse (Natural Monument number 347) is a breed of horse that has experienced long-term isolation and domestication in Jeju Island, South Korea. We evaluated genetic features of this breed, including SNP, by whole-genome resequencing using an Illumina HiSeq 2000. A total of 5,986,852 SNP were identified in 4 Jeju horses and were divided into homozygous and heterozygous SNP (2,357,099 and 3,629,753 SNP, respectively). It revealed that 63.8% of these SNP resided in intergenic regions. Immune response genes with nonsynonymous SNP were overrepresented in Jeju horses as evidenced by Gene Ontolo...
Using an Inbred Horse Breed in a High Density Genome-Wide Scan for Genetic Risk Factors of Insect Bite Hypersensitivity (IBH). While susceptibility to hypersensitive reactions is a common problem amongst humans and animals alike, the population structure of certain animal species and breeds provides a more advantageous route to better understanding the biology underpinning these conditions. The current study uses Exmoor ponies, a highly inbred breed of horse known to frequently suffer from insect bite hypersensitivity, to identify genomic regions associated with a type I and type IV hypersensitive reaction. A total of 110 cases and 170 controls were genotyped on the 670K Axiom Equine Genotyping Array. Quality control ...
Development of a new fertility prediction model for stallion semen, including flow cytometry. Several laboratories routinely use flow cytometry to evaluate stallion semen quality. However, objective and practical tools for the on-field interpretation of data concerning fertilizing potential are scarce. A panel of nine tests, evaluating a large number of compartments or functions of the spermatozoa: motility, morphology, viability, mitochondrial activity, oxidation level, acrosome integrity, DNA integrity, "organization" of the plasma membrane, and hypoosmotic resistance, was applied to a population of 43 stallions, 33 of which showing widely differing fertilities (19%-84% pregnancy rat...
An Overview of Ten Italian Horse Breeds through Mitochondrial DNA. The climatic and cultural diversity of the Italian Peninsula triggered, over time, the development of a great variety of horse breeds, whose origin and history are still unclear. To clarify this issue, analyses on phenotypic traits and genealogical data were recently coupled with molecular screening. Methods: To provide a comprehensive overview of the horse genetic variability in Italy, we produced and phylogenetically analyzed 407 mitochondrial DNA (mtDNA) control-region sequences from ten of the most important Italian riding horse and pony breeds: Bardigiano, Esperia, Giara, Lipizzan, Maremm...
Characterization of Genetic Variability of Venezuelan Equine Encephalitis Viruses. Venezuelan equine encephalitis virus (VEEV) is a mosquito-borne alphavirus that has caused large outbreaks of severe illness in both horses and humans. New approaches are needed to rapidly infer the origin of a newly discovered VEEV strain, estimate its equine amplification and resultant epidemic potential, and predict human virulence phenotype. We performed whole genome single nucleotide polymorphism (SNP) analysis of all available VEE antigenic complex genomes, verified that a SNP-based phylogeny accurately captured the features of a phylogenetic tree based on multiple sequence alignment, an...
Polarisation of equine pregnancy outcome associated with a maternal MHC class I allele: Preliminary evidence. Identification of risk factors which are associated with severe clinical signs can assist in the management of disease outbreaks and indicate future research areas. Pregnancy loss during late gestation in the mare compromises welfare, reduces fecundity and has financial implications for horse owners. This retrospective study focussed on the identification of risk factors associated with pregnancy loss among 46 Thoroughbred mares on a single British stud farm, with some but not all losses involving equid herpesvirus-1 (EHV-1) infection. In a sub-group of 30 mares, association between pregnancy ...
Phaeohyphomycosis due to Pyrenophora phaeocomes and Drechslera nobleae in an Appaloosa mare. A 21-year-old Appaloosa mare was presented with a pigmented cutaneous mass at the base of the right side of the neck. The diagnosis of phaeohyphomycosis due to pigmented fungi, known as Pyrenophora phaeocomes and Drechslera nobleae, was made based on a histopathology report followed by polymerase chain reaction (PCR) and 18S rRNA gene sequencing. The mass was surgically excised with clean margins, which is usually curative. Une jument Appaloosa âgée de 21 ans a été présentée avec une masse cutanée pigmentée à la base du côté droit du cou. Le diagnostic de phæohyphomycose causée p...
A methicillin-resistant Staphylococcus aureus (MRSA) Sequence Type 8, spa type t11469 causing infection and colonizing horses in Italy. A Methicillin-resistantStaphylococcus aureus(MRSA) was isolated in Italy from a pathological sample of a mare presenting chronic purulent sinusitis and that had undergone frontal-sinus surgery three months before. Humans, horses, dogs and environmental samples were subsequently collected at the mare's stable and at the Veterinary Hospital, where the mare was operated/hospitalized, and screened for the presence of MRSA that was detected from other horses and from the environment at both sites. All the MRSA isolates belonged to clonal complex (CC)8, ST8-t11469-SCCmec-IVa, and showed similar phen...
Differential expression of microRNAs in bovine papillomavirus type 1 transformed equine cells. Bovine papillomavirus (BPV) types 1 and 2 play an important role in the pathogenesis of equine sarcoids (ES), the most common cutaneous tumour affecting horses. MicroRNAs (miRNAs), small non-coding RNAs that regulate essential biological and cellular processes, have been found dysregulated in a wide range of tumours. The aim of this study was to identify miRNAs associated with ES. Differential expression of miRNAs was assessed in control equine fibroblasts (EqPalFs) and EqPalFs transformed with the BPV-1 genome (S6-2 cells). Using a commercially available miRNA microarray, 492 mature miRNAs we...
Embryo aggregation does not improve the development of interspecies somatic cell nuclear transfer embryos in the horse. The low efficiency of interspecies somatic cell nuclear transfer (iSCNT) makes it necessary to investigate new strategies to improve embryonic developmental competence. Embryo aggregation has been successfully applied to improve cloning efficiency in mammals, but it remains unclear whether it could also be beneficial for iSCNT. In this study, we first compared the effect of embryo aggregation over in vitro development and blastocyst quality of porcine, bovine, and feline zona-free (ZF) parthenogenetic (PA) embryos to test the effects of embryo aggregation on species that were later used as en...
Claudin-1, -2, -4, and -5: comparison of expression levels and distribution in equine tissues. Claudins, which are known as transmembrane proteins play an essential role in tight junctions (TJs) to form physical barriers and regulate paracellular transportation. To understand equine diseases, it is helpful to measure the tissue-specific expression of TJs in horses. Major equine diseases such as colic and West Nile cause damage to TJs. In this study, the expression level and distribution of claudin-1, -2, -4, and -5 in eight tissues were assessed by Western blotting and immunohistochemistry methods. Claudin-1 was primarily identified in the lung, duodenum, and uterus, claudin-2 was evenl...
Mitochondrial DNA Copy Number in Spermatozoa of Fertile Stallions. Predicting male fertility on non-invasive sperm traits is of big importance to human and animal reproduction strategies. Combining the wide range of parameters monitored by computer-assisted sperm analysis (CASA) with some molecular traits (e.g. mtDNA content) may help to identify markers of the male fertility. The aim of this study was to characterize variation in the mtDNA copy number in equine sperm and to investigate whether mtDNA content is correlated with quality traits of stallion spermatozoa and the age of the male. Ejaculates collected from 53 fertile stallions were divided into four ...
