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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.
Clinical ophthalmic challenges in the horse: a retrospective view forward. The author reviews some aspects of vision and ophthalmic disease in the horse and considers how some recent developments in ocular immunobiology and molecular pathology in other species may give pointers toward an understanding of disease processes in the horse.
Molecular characterization of the Babesia caballi rap-1 gene and epidemiological survey in horses in Israel. Equine piroplasmosis imposes great concerns for the equine industry regarding international horse movement, and therefore requires reliable diagnostic tools. Recent studies from South Africa and Jordan, including a preliminary study in Israel, reported extremely low seroprevalence to Babesia caballi (B. caballi) (0-1%) using the acceptable rhoptry-associated protein-1 (RAP-1) cELISA. In accordance with the study from South Africa demonstrating a significant heterogeneity in the rap-1 gene sequence of South African B. caballi isolates, the objectives of this study were to phylogenetically chara...
Sex determination in horses – current status and future perspectives. In the equine species, sex determination of the conceptus is of growing interest for the breeding industry. In horses, the sex ratio of the offspring depends on changes in body condition of the mother at conception and under natural conditions may thus markedly deviate from an expected 1:1 ratio. Insemination with sex-sorted spermatozoa allows a pronounced shift of the sex ratio but at present pregnancy rates are low and vary considerably under field conditions. In equine embryo transfer programmes, sex determination in embryos before transfer via genetic methods is a promising approach with h...
Expression of aldo-keto reductase 1C23 in the equine corpus luteum in different luteal phases. Regression of the corpus luteum (CL) is characterized by a decay in progesterone (P4) production (functional luteolysis) and disappearance of luteal tissues (structural luteolysis). In mares, structural luteolysis is thought to be caused by apoptosis of luteal cells, but functional luteolysis is poorly understood. 20α-hydroxysteroid dehydrogenase (20α-HSD) catabolizes P4 into its biologically inactive form, 20α-hydroxyprogesterone (20α-OHP). In mares, aldo-keto reductase (AKR) 1C23, which is a member of the AKR superfamily, has 20α-HSD activity. To clarify whether AKR1C23 is associated wi...
The utility of low-density genotyping for imputation in the Thoroughbred horse. Despite the dramatic reduction in the cost of high-density genotyping that has occurred over the last decade, it remains one of the limiting factors for obtaining the large datasets required for genomic studies of disease in the horse. In this study, we investigated the potential for low-density genotyping and subsequent imputation to address this problem. Results: Using the haplotype phasing and imputation program, BEAGLE, it is possible to impute genotypes from low- to high-density (50K) in the Thoroughbred horse with reasonable to high accuracy. Analysis of the sources of variation in imput...
Phylogenetic analysis of Staphylococcus aureus CC398 reveals a sub-lineage epidemiologically associated with infections in horses. In the early 2000s, a particular MRSA clonal complex (CC398) was found mainly in pigs and pig farmers in Europe. Since then, CC398 has been detected among a wide variety of animal species worldwide. We investigated the population structure of CC398 through mutation discovery at 97 genetic housekeeping loci, which are distributed along the CC398 chromosome within 195 CC398 isolates, collected from various countries and host species, including humans. Most of the isolates in this collection were received from collaborating microbiologists, who had preserved them over years. We discovered 96 bi-a...
Extended-spectrum β-lactamase, carbapenemase and AmpC producing Enterobacteriaceae in companion animals. Organisms in the family Enterobactericeae including, Escherichia coli, commonly cause community and hospital-associated infections in both humans and companion animals. The increasing prevalence of infections with organisms producing broad spectrum β-lactamses such as the ESBLs (particularly the CTX-M type), AmpC and carbapenemase enzymes are threatening the future of the β-lactam drugs. While a number of organisms within the Enterobacteriaceae producing these enzymes have been isolated from cats, dogs and horses, E. coli, including isolates indistinguishable from strains found in people, ha...
Characterization of a mucoid clone of Streptococcus zooepidemicus from an epizootic of equine respiratory disease in New Caledonia. Streptococcus equi subspecies zooepidemicus (Sz) is a tonsillar and mucosal commensal of healthy horses with the potential to cause opportunistic infections of the distal respiratory tract stressed by virus infection, transportation, training or high temperature. The invasive clone varies from horse to horse with little evidence of lateral transmission in the group. Tonsillar isolates are non-mucoid although primary isolates from opportunist lower respiratory tract infections may initially be mucoid. In this study, a novel stably mucoid Sz (SzNC) from a clonal epizootic of respiratory disease ...
The use of a novel combination of diagnostic molecular and cytogenetic approaches in horses with sexual karyotype abnormalities: a rare case with an abnormal cellular chimerism. Sex chromosome aberrations are known to cause congenital abnormalities and unexplained infertility in horses. Most of these anomalies remain undiagnosed because of the complexity of the horse karyotype and the lack of specialized laboratories that can perform such diagnoses. On the other hand, the utilization of microsatellite markers is a technique widely spread in horse breeding, mostly because of their usage in parentage tests. We studied the usage of a novel combination of diagnostic approaches in the evaluation of a very uncommon case of chromosomal abnormalities in a Spanish purebred col...
In vitro metabolism of testosterone in the horse liver and involvement of equine CYPs 3A89, 3A94 and 3A95. Testosterone (TES) 6-β-hydroxylation is a significant metabolic step in the biotransformation of TES in human liver microsomes and reflects cytochrome P450 (CYP) 3A4/5 specific metabolic activity. Several CYP3A enzymes have been annotated in the horse genome, but functional characterization is missing. This descriptive study investigates TES metabolism in the horse liver in vitro and the qualitative contribution of three CYP3A isoforms of the horse. Metabolism of TES was investigated by using equine hepatocyte primary cultures and liver microsomes. Chemical inhibitors were used to determine t...
Advancing maternal age predisposes to mitochondrial damage and loss during maturation of equine oocytes in vitro. In many mammalian species, reproductive success decreases with maternal age. One proposed contributor to this age-related decrease in fertility is a reduction in the quantity or functionality of mitochondria in oocytes. This study examined whether maternal age or (in vitro maturation). IVM affect the quantity of mitochondria in equine oocytes. Oocytes were collected from the ovaries of slaughtered mares categorized as young (<12 years) or aged (≥12 years) and either denuded and prepared for analysis immediately (not-IVM) or matured in vitro for 30 hours before preparation (IVM). The m...
Comparative analysis of the methanogen diversity in horse and pony by using mcrA gene and archaeal 16s rRNA gene clone libraries. Comparative analysis of methanogen compositions in the feces of horse and pony was carried out by constructing the α -subunit of methyl coenzyme-M reductase (mcrA) gene and 16S ribosomal RNA gene (16S rRNA) clone libraries. The mcrA clone library analysis indicated that Methanomicrobiales was predominant in both horse and pony. Furthermore, most of the clones of the 16S rRNA gene library showed that Methanomicrobiales was also predominant in horse and pony, but the LIBSHUFF analysis showed that the horse and pony libraries were significantly different (P < 0.05). Most of operational taxono...
Genome-wide detection of copy number variations among diverse horse breeds by array CGH. Recent studies have found that copy number variations (CNVs) are widespread in human and animal genomes. CNVs are a significant source of genetic variation, and have been shown to be associated with phenotypic diversity. However, the effect of CNVs on genetic variation in horses is not well understood. In the present study, CNVs in 6 different breeds of mare horses, Mongolia horse, Abaga horse, Hequ horse and Kazakh horse (all plateau breeds) and Debao pony and Thoroughbred, were determined using aCGH. In total, seven hundred CNVs were identified ranging in size from 6.1 Kb to 0.57 Mb across a...
Epidemiology and Genetic Characterization of H3N8 Equine Influenza Virus Responsible for Clinical Disease in Algeria in 2011. An outbreak of equine influenza (EI) was reported in Algeria between May and July, 2011. The outbreak started in Tiaret, in west province of Algeria, and spread to the other parts of the country affecting almost 900 horses in many provinces. The population studied was composed of 325 horses from different groups of age. Clinical sign expression was age dependent. Indeed, a morbidity rate of 14.9% was observed in horses under 15 months old and a rate of 4.95% in horses over 8 years old. Interestingly, the morbidity rate raised sharply to reach 100% in horses aged between 18 months and 7 yea...
Recent advances in understanding the pathogenesis of Lawsonia intracellularis infections. Proliferative enteropathy is an infectious disease caused by an obligate intracellular bacterium, Lawsonia intracellularis, and characterized by thickening of the intestinal epithelium due to enterocyte proliferation. The disease is endemic in swine herds and has been occasionally reported in various other species. Furthermore, outbreaks among foals began to be reported on breeding farms worldwide within the past 5 years. Cell proliferation is directly associated with bacterial infection and replication in the intestinal epithelium. As a result, mild to severe diarrhea is the major clinical si...
Genetic risk factors for insidious equine recurrent uveitis in Appaloosa horses. Appaloosa horses are predisposed to equine recurrent uveitis (ERU), an immune-mediated disease characterized by recurring inflammation of the uveal tract in the eye, which is the leading cause of blindness in horses. Nine genetic markers from the ECA1 region responsible for the spotted coat color of Appaloosa horses, and 13 microsatellites spanning the equine major histocompatibility complex (ELA) on ECA20, were evaluated for association with ERU in a group of 53 Appaloosa ERU cases and 43 healthy Appaloosa controls. Three markers were significantly associated (corrected P-value <0.05): a S...
Comparative genomic analyses reveal a lack of a substantial signature of host adaptation in Rhodococcus equi (‘Prescottella equi’). Rhodococcus equi ('Prescottella equi') is a pathogenic actinomycete primarily infecting horses but has emerged as an opportunistic human pathogen. We have sequenced the genome of the type strain of this species, R. equi strain C7(T) , and compared the genome with that of another foal isolate 103S and of a human isolate ATCC 33707. The R. equi strains are closely related to each other and yet distantly related to other rhodococci and Nocardia brasiliensis. The comparison of gene contents among R. equi strains revealed minor differences that could be associated with host adaptation from foals to...
Equine bone marrow-derived mesenchymal stromal cells are heterogeneous in MHC class II expression and capable of inciting an immune response in vitro. The horse is a valuable species to assess the effect of allogeneic mesenchymal stromal cells (MSCs) in regenerative treatments. No studies to date have examined recipient response to major histocompatibility complex (MHC)-mismatched equine MSCs. The purposes of this study were to immunophenotype MSCs from horses of known MHC haplotype and to compare the immunogenicity of MSCs with differing MHC class II expression. Methods: MSCs and peripheral blood leukocytes (PBLs) were obtained from Thoroughbred horses (n=10) of known MHC haplotype (ELA-A2, -A3, and -A9 homozygotes). MSCs were cultured thro...
A chromosomal region on ECA13 is associated with maxillary prognathism in horses. Hereditary variations in head morphology and head malformations are known in many species. The most common variation encountered in horses is maxillary prognathism. Prognathism and brachygnathism are syndromes of the upper and lower jaw, respectively. The resulting malocclusion can negatively affect teeth wear, and is considered a non-desirable trait in breeding programs. We performed a case-control analysis for maxillary prognathism in horses using 96 cases and 763 controls. All horses had been previously genotyped with a commercially available 50 k SNP array. We analyzed the data with a mixe...
Worldwide frequency distribution of the ‘Gait keeper’ mutation in the DMRT3 gene. For centuries, domestic horses have represented an important means of transport and served as working and companion animals. Although their role in transportation is less important today, many horse breeds are still subject to intense selection based on their pattern of locomotion. A striking example of such a selected trait is the ability of a horse to perform additional gaits other than the common walk, trot and gallop. Those could be four-beat ambling gaits, which are particularly smooth and comfortable for the rider, or pace, used mainly in racing. Gaited horse breeds occur around the glob...
Genetic and environmental analysis of dystocia and stillbirths in draft horses. Genetic parameters and environmental factors were estimated for foaling ease (FE) and stillbirths (SBs) in four breeds of draft horses based on 11 229, 38 877, 35 764 and 13 274 FE and SB scores recorded between 1998 and 2010 for Ardennais (A), Breton (B), Comtois (C) and Percheron (P), respectively. Incidences for the three FE categories were: easy or without help 91.0% (A) to 95.4% (B), difficult 3.4% (B) to 7.1% (A) and intervention of a veterinarian 1.1% (B) to 1.9% (A). The frequency of SB ranged between 5.4% (B) and 9.4% (A). A multiple-trait threshold animal model was used that included...
Genetic polymorphism of Hucul horse population based on 17 microsatellite loci. Short tandem repeat (STR) loci, i.e. microsatellites are a class of genetic markers commonly used for population studies and parentage control. This study determined the usefulness of microsatellite markers recommended by International Society for Animal Genetics (ISAG) for identification and pedigree analysis in horses based on the example of Polish Hucul horse population (Equus caballus). The set of seventeen microsatellites loci was tested (AHT4, AHT5, ASB2, HMS2, HMS3, HMS6, HMS7, HTG10, HTG4, HTG6, HTG7, VHL20, ASB17, ASB23, CA425, HMS1, LEX3) for 216 individuals. All samples were genotyp...
Sequence analysis of the equine ACTN3 gene in Australian horse breeds. The sarcomeric α-actinins, encoded by the genes ACTN2 and ACTN3, are major structural components of the Z-line and have high sequence similarity. α-Actinin-2 is present in all skeletal muscle fibres, while α-actinin-3 has developed specialized expression in only type 2 (fast, glycolytic) fibres. A common single nucleotide polymorphism (SNP) in the human ACTN3 gene (R577X) has been found to influence muscle performance in elite athletes and the normal population. For this reason, equine ACTN3 (eACTN3) is considered to be a possible candidate that may influence horse performance. In this stud...
Anthelmintic resistance in important parasites of horses: does it really matter? Parascaris equorum and cyathostomins are currently considered the most important parasites of horses and have traditionally been controlled with anthelmintics belonging to three drug classes: benzimidazoles, the tetrahydropyrimidine pyrantel, and macrocyclic lactones. Unfortunately, resistance to benzimidazoles, and to a lesser extent pyrantel, is widespread in cyathostomins around the world. Furthermore, resistance to macrocyclic lactones appears to be in the early stages of development in cyathostomins in multiple locations. In contrast, P. equorum populations have remained susceptible to th...
Long-range electron transfer with myoglobin immobilized at Au/mixed-SAM junctions: mechanistic impact of the strong protein confinement. Horse muscle myoglobin (Mb) was tightly immobilized at Au-deposited ~15-Å-thick mixed-type (1:1) alkanethiol SAMs, HS-(CH₂)₁₁-COOH/HS-(CH₂)₁₁-OH, and placed in contact with buffered H₂O or D₂O solutions. Fast-scan cyclic voltammetry (CV) and a Marcus-equation-based analysis were applied to determine unimolecular standard rate constants and reorganization free energies for electron transfer (ET), under variable-temperature (15-55 °C) and -pressure (0.01-150 MPa) conditions. The CV signal was surprisingly stable and reproducible even after multiple temperature and pressure cycl...
Membrane culture and reduced oxygen tension enhances cartilage matrix formation from equine cord blood mesenchymal stromal cells in vitro. Ongoing research is aimed at increasing cartilage tissue yield and quality from multipotent mesenchymal stromal cells (MSC) for the purpose of treating cartilage damage in horses. Low oxygen culture has been shown to enhance chondrogenesis, and novel membrane culture has been proposed to increase tissue yield and homogeneity. The objective of this study was to evaluate and compare the effect of reduced oxygen and membrane culture during in vitro chondrogenesis of equine cord blood (CB) MSC. Methods: CB-MSC (n = 5 foals) were expanded at 21% oxygen prior to 3-week differentiation in membrane or...
Immunophenotypic characterization and tenogenic differentiation of mesenchymal stromal cells isolated from equine umbilical cord blood. Mesenchymal stem cells (MSCs) isolated from umbilical cord blood (UCB) in equines have not been well characterized with respect to the expression of pluripotency and mesenchymal markers and for tenogenic differentiation potential in vitro. The plastic adherent fibroblast-like cells isolated from 13 out of 20 UCB samples could proliferate till passage 20. The cells expressed pluripotency markers (OCT4, NANOG, and SOX2) and MSC surface markers (CD90, CD73, and CD105) by RT-PCR, but did not express CD34, CD45, and CD14. On immunocytochemistry, the isolated cells showed expression of CD90 and CD73...
Primer effect in the detection of mtDNA heteroplasmy: insights from horse Cytochrome b gene. Heteroplasmy, the presence of bi-allelic mtDNA types within an individual, has been previously detected in the D-loop region and Cytochrome b gene (Cytb) of mitochondrial DNA using PCR-RFLP. However, heteroplasmy was absent in thousands of equine mtDNA sequences deposited in GenBank. To address whether heteroplasmy widely exists in mitochondria of Chinese indigenous horses, we generated the data set of the target sites in Cytb region with Sanger sequencing and PCR-RFLP method as well. In this study, 23 heteroplasmic individuals were detected in 430 Chinese local horses. Both site and length he...
During cooled storage the extender influences processed autophagy marker light chain 3 (LC3B) of stallion spermatozoa. To investigate the role of the processed autophagy marker light chain 3 (LC3B) protein in sperm survival in stallion semen processing during cooled storage, split ejaculates were diluted in two different extenders, KMT and INRA 96, and LC3B processing and sperm quality evaluated during incubation at 5°C for five days. After 3 days of incubation there was a drop in total motility in both extenders, although the percentage of progressive motile sperm was greater (P<0.05) in samples extended in INRA96. On Day 5 of cooled storage all sperm parameters decreased significantly independent of the ...
