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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.
History of Lipizzan horse maternal lines as revealed by mtDNA analysis. Sequencing of the mtDNA control region (385 or 695 bp) of 212 Lipizzans from eight studs revealed 37 haplotypes. Distribution of haplotypes among studs was biased, including many private haplotypes but only one haplotype was present in all the studs. According to historical data, numerous Lipizzan maternal lines originating from founder mares of different breeds have been established during the breed's history, so the broad genetic base of the Lipizzan maternal lines was expected. A comparison of Lipizzan sequences with 136 sequences of domestic- and wild-horses from GenBank showed a clusterin...
Progesterone induces acrosome reaction in stallion spermatozoa via a protein tyrosine kinase dependent pathway. Progesterone (P(4)) is a physiological inducer of the acrosome reaction (AR) in stallion spermatozoa. However, the capacitation-dependent changes that enable progesterone binding, and the nature of the signaling cascade that is triggered by progesterone and results in induction of the AR, are poorly understood. The aim of the current study was, therefore, to investigate the protein kinase dependent signaling cascades involved in progesterone-mediated induction of the AR in stallion spermatozoa. In addition, we aimed to determine whether bicarbonate, an inducer of sperm capacitation, acted via ...
Comparative study of tyrosine radicals in hemoglobin and myoglobins treated with hydrogen peroxide. The reactions of hydrogen peroxide with human methemoglobin, sperm whale metmyoglobin, and horse heart metmyoglobin were studied by electron paramagnetic resonance (EPR) spectroscopy at 10 K and room temperature. The singlet EPR signal, one of the three signals seen in these systems at 10 K, is characterized by a poorly resolved, but still detectable, hyperfine structure that can be used to assign it to a tyrosyl radical. The singlet is detectable as a quintet at room temperature in methemoglobin with identical spectral features to those of the well characterized tyrosyl radical in photosystem...
Quantification and distribution of equine oocyte cortical granules during meiotic maturation and after activation. In vitro fertilization (IVF) is being routinely used in humans and several domestic species, however, limited success has been achieved in the horse. Although immature equine oocytes are capable of completing meiosis in vitro, subsequent fertilization, and embryonic development of those oocytes are questionable. The lack of development of these oocytes could be attributed to an impaired cytoplasmic maturation. In the horse, the study of oocyte cytoplasmic maturation and post-fertilization development has been hindered by the lack of progress in IVF. In mammalian oocytes, migration of cortical ...
Comparison between glycerol and ethylene glycol for the cryopreservation of equine spermatozoa: semen quality assessment with standard analyses and with the hypoosmotic swelling test. The aims of this study were to compare glycerol (G) at customary concentrations and ethylene glycol (EG) as cryoprotectants for stallion semen in a skimmed milk (SM) extender, to test different EG concentrations and to compare the results of manual and computerized analysis with the hypoosmotic swelling (HOS) test. Ejaculates from two stallions were collected over 3 weeks (6 ejaculates per stallion), diluted in a SM based extender, divided into 4 fractions, centrifuged and diluted again to a concentration of 100 x 10(6) mL(-1) progressive motile spermatozoa (PMS) in addition with the cryoprote...
Early evaluation of dressage ability in different breeds. Dressage is one of the Olympic equestrian sports practiced in several countries using different horse breeds. Specific characteristics of the walk, trot and canter are required for dressage. It has been assumed that some of these traits could be selected for genetically and contribute to dressage performance. The purpose of this study was to compare the walk, trot and conformation characteristics in young horses of different breeds used for dressage. A total of 142 horses age 3 years were classified into 3 groups of breeds (German, French and Spanish saddle horses) and tested using the same pr...
Age-related changes and inheritance of lactate transport activity in red blood cells. In red blood cell membranes, the activity of the main lactate carrier, H+-monocarboxylate co-transporter (MCT), varies interindividually and its distribution is bimodal. To show the repeatability of MCT activity, 2 to 5 blood samples were taken, at an interval of approximately 1 year, from 51 Standardbred horses, age 2 weeks-8 years, for a total of 128 observations. The horses could be divided into low (LT) and high (HT) lactate transport activity groups. Age significantly affected (P<0.05) MCT activity such that activity was highest in foals, reached a nadir at 2-3 years, and tended to inc...
Induction of hyaluronan synthase 2 by human chorionic gonadotropin in mural granulosa cells of equine preovulatory follicles. In contrast to other species, the preovulatory rise in gonadotropins in mares causes a remarkable expansion of the entire granulosa cell layer in vivo, suggesting that hyaluronan (HA) synthesis may be regulated in mural granulosa cells in this species. The objectives of this study were to clone and characterize equine hyaluronan synthase 2 (HAS2) and investigate the regulation of its transcript and of HA synthesis in equine follicles during human chorionic gonadotropin (hCG)- induced ovulation. Results showed that the equine HAS2 cDNA contains a 5'-untranslated region of 436 bp, an open readin...
Distribution of mecA-harboring staphylococci in healthy mares. The prevalence of staphylococci that harbor the mecA gene responsible for methicillin resistance was examined in healthy breeding mares. Staphylococci often cause diseases of horses such as metritis, keratitis, and abscess. Methicillin-resistant staphylococci would make antibiotic treatments ineffective, so it may be significant to know the distribution of mecA-harboring staphylococci in mares. Isolation of mecA-harboring staphylococci was achieved from nares and pasterns of 100 mares in Hokkaido, Japan. From 13% of the mares, mecA-harboring staphylococci, including 15 isolates of Staphylococc...
Anthelmintic resistance in nematodes of horses. Suppressive anthelmintic treatment strategies originally designed to control Strongylus vulgaris in horses were extremely successful in reducing morbidity and mortality from parasitic disease. Unfortunately, this strategy has inadvertently resulted in the selection of drug-resistant cyathostomes (Cyathostominea), which are now considered the principal parasitic pathogens of horses. Resistance in the cyathostomes to benzimidazole drugs is highly prevalent throughout the world, and resistance to pyrantel appears to be increasingly common. However, there are still no reports of ivermectin resista...
Lack of parthenogenesis by Amblyomma cajennense (Acari: Ixodidae). Some reproductive parameters of adult stages of Amblyomma cajennense ticks were studied. The capacity of virgin females to reproduce by parthenogenesis was evaluated, during an experimental infestation, in absence of males, on a horse (Equus cabalus). Ticks were spread either completely free or in limited sites on the body of the animal. The engorged virgin females showed longer feeding periods and lighter body weights than those that had been fertilized. Some of these unmated females produced smaller egg masses, which had no embryonary development. On the other hand, females that had been ins...
Construction of a stable non-mucoid deletion mutant of the Streptococcus equi Pinnacle vaccine strain. Streptococcus equi causes equine strangles, a purulent lymphadenopathy of the head and neck. An avirulent, non-encapsulated strain (Pinnacle) has been used widely in North America as an intranasal vaccine. The aim of the study was to create a specific mutation of the hyaluronate synthase (hasA) gene in Pinnacle to permanently abolish the production of capsule and provide an easily recognisable genetic marker. An internal fragment of hasA was generated by PCR and cloned into pTW100 (Microscience, UK). An encapsulated revertant of Pinnacle was then transformed with the recombinant plasmid by ele...
Kinetic barriers to the folding of horse cytochrome C in the reduced state. To determine the kinetic barrier in the folding of horse cytochrome c, a CO-liganded derivative of cytochrome c, called carbonmonoxycytochrome c, has been prepared by exploiting the thermodynamic reversibility of ferrocytochrome c unfolding induced by guanidinium hydrochloride (GdnHCl), pH 7. The CO binding properties of unfolded ferrocytochrome c, studied by 13C NMR and optical spectroscopy, are remarkably similar to those of native myoglobin and isolated chains of human hemoglobin. Equilibrium unfolding transitions of ferrocytochrome c in the presence and the absence of CO observed by both e...
Cytogenetic localization of 136 genes in the horse: comparative mapping with the human genome. The aim of this study was to increase the number of type I markers on the horse cytogenetic map and to improve comparison with maps of other species, thus facilitating positional candidate cloning studies. BAC clones from two different sources were FISH mapped: homologous horse BAC clones selected from our newly extended BAC library using consensus primer sequences and heterologous goat BAC clones. We report the localization of 136 genes on the horse cytogenetic map, almost doubling the number of cytogenetically mapped genes with 48 localizations from horse BAC clones and 88 from goat BAC clon...
Reclassification of equine isolates previously reported as Actinobacillus equuli, variants of A. equuli, Actinobacillus suis or Bisgaard taxon 11 and proposal of A. equuli subsp. equuli subsp. nov. and A. equuli subsp. haemolyticus subsp. nov. Members of Bisgaard taxon 11 have been isolated from horses. These bacteria are of importance in the veterinary clinic and also to the medical profession, since they may be isolated from infected wounds of humans bitten by horses. Six strains from different continents were identified as taxon 11, with 16S rRNA similarities between 98.0 and 99.7%. A single isolate that represented the so-called (+)L-arabinose-positive Actinobacillus equuli isolated from a diseased foal showed 99.9% 16S rRNA similarity to the type strain of A. equuli. DNA-DNA hybridizations showed that (+)L-arabinose-positive st...
Characterization of the NRAMP1 (SLC11A1) gene in the horse (Equus caballus L.). The complete coding cDNA sequence of the horse NRAMP1 (SLC11A1) gene was determined (GenBank accession number AF354445). The nucleotide sequence of the horse NRAMP1 gene is similar to sequences of this gene in other species. The gene contains 15 exons whose total length of 1,635 bp corresponds to 544 amino acids constituting the resulting putative protein. Hydrophobicity profile analysis of the deduced horse NRAMP1 gene product showed a nearly identical structure with the mouse NRAMP1 protein. The gene was found to be located on the short arm of ECA 6p12-13 by fluorescence in situ hybridizatio...
Linkage of the grey coat colour locus to microsatellites on horse chromosome 25. The progressive loss of colour in the hair of grey horses is controlled by a dominantly inherited allele at the Grey locus (GG). In this study, two paternal Quarter Horse (QH) families segregating for the GG allele were genotyped with a set of 101 microsatellite markers spanning the 31 autosomes and the X chromosome. This genome scan demonstrated linkage of Grey to COR018 (RF=0.02, LOD=12.04) on horse chromosome 25 (ECA25). Further chromosome-specific analysis of seven total QH families confirmed the linkage of Grey to a group of ECA25 markers and the map order of NVHEQ43-(0.24)-UCDEQ405-(0.09...
Phylogenetic relationships of Argentinean Creole horses and other South American and Spanish breeds inferred from mitochondrial DNA sequences. South American horses constitute a direct remnant of the Iberian horses brought to the New World by the Spanish conquerors. The source of the original horses was Spain, and it is generally assumed that the animals belonged to the Andalusian, Spanish Celtic, Barb or Arabian breeds. In order to establish the relationship between Argentinean and Spanish horses, a portion of the mitochondrial D-loop of 104 animals belonging to nine South American and Spanish breeds was analysed using SSCP and DNA sequencing. The variability found both within and between breeds was very high. There were 61 polymorp...
Assignment of the horse grey coat colour gene to ECA25 using whole genome scanning. The dominant grey coat colour gene of horses has been mapped using a whole genome scanning approach. Samples from a large half-sibling pedigree of Thoroughbred horses were utilized in order to map the grey coat colour locus, G. Multiplex groups of microsatellite markers were developed and used to efficiently screen the horse genome at a resolution of approximately 22 cM, based on an estimated map length for the horse genome of 2720 cM. The grey gene was assigned to chromosome 25 (ECA25), one of the smaller acrocentric horse chromosomes. Based on the current state of knowledge of conserved synt...
Greater genetic variability in Argentine Creole than in Thoroughbred horses based on serum protein polymorphisms. Genetic polymorphism was analyzed for five blood proteins: albumin - Al, esterase - Es, alpha(1)B-glycoprotein - Xk, transferrin - Tf and hemoglobin - Hb in 200 Thoroughbred (TB) and 124 Argentine Creole (AC) horses. Of the five systems examined, Tf and Hb were not in Hardy-Weinberg equilibrium in either breed and Es was not in equilibrium in the Creole breed. Genetic variability, estimated as average heterozygosity, was higher in AC (H = 0.585 +/- 0.131) than in TB (H = 0.353 +/- 0.065). The genetic differentiation between these two populations (F(ST)) was 0.109. Thus, of the total genetic di...
Nucleation rate determination by a concentration pulse technique: application on ferritin crystals to show the effect of surface treatment of a substrate. The nucleation of horse spleen ferritin (HSF) crystals on substrates was investigated using a new modification of the double pulse technique. The influence of three different structureless substrates (glass, glass covered by methyl groups and poly-L-lysin template) on the nucleation was studied. The boundaries in the phase-diagram, which separate zones of crystal nucleation and growth were obtained by keeping pH = 5.0, and using CdSO(4) as crystallizing agent. The steady-state nucleation rates were determined. The energy required for critical nuclei formation was evaluated (10(-13) erg) and th...
Correlation between the osmotic second virial coefficient and solubility for equine serum albumin and ovalbumin. The Haas - Drenth - Wilson (HDW) (Haas et al., 1999) theoretical model was used to correlate osmotic second virial coefficient (B) values with solubility (S) values for equine serum albumin (ESA) and ovalbumin for corresponding solution conditions. The best fit from the theoretical model was compared to experimental S versus B data. B values were experimentally measured using static light scattering. Solubilities of ESA were estimated using a sitting drop method. When the experimental data for S versus B were plotted, an excellent fit for ESA was obtained according to the HDW model. The result...
Equine epitheliogenesis imperfecta in two american saddlebred foals is a lamina lucida defect. Necropsy of two American Saddlebred fillies diagnosed with epitheliogenesis imperfecta (EI) revealed missing patches of epithelium of the skin and oral mucosa as well as dental abnormalities. Examination of the digestive tract did not reveal signs of pyloric atresia in either foal. Histopathologic examination revealed separation of the epidermis from the dermis. In both foals a division within the lamina lucida of the basal lamina was observed by transmission electron microscopy. In comparison with an age-specific control, the ultrastructure of intact skin from the EI-affected foals showed abn...
Foal with Overo lethal white syndrome born to a registered quarter horse mare. A 16-hour-old white foal, born to a registered quarter horse mare, was examined for signs of colic. The foal had Overo lethal white syndrome, which causes ileocolonic agangliosis. This was confirmed by DNA testing. Since there is no treatment for Overo lethal white syndrome, the foal was euthanized.
Molecular epidemiology of VapA-positive Rhodococcus equi in thoroughbred horses in Kagoshima, Japan. The prevalence of virulent R. equi having 15- to 17-kDa antigens (VapA) in fecal isolates from 13 thoroughbred foals and their dams on 5 farms in Kagoshima, Japan, and the plasmid profiles of VapA-positive isolates by restriction fragment digestion patterns were investigated to compare the genotypic variation among virulence plasmids of R. equi isolates from Japan. In total, 218 (24.6%) of 886 isolates from the feces of the 13 foals and 13 (12.5%) of 104 isolates from the feces of their dams demonstrated VapA-positive R. equi. Plasmid DNA preparations of 231 virulent isolates from foals and da...
Detection of equine Babesia spp. gene fragments in Dermacentor nuttalli Olenev 1929 infesting mongolian horses, and their amplification in egg and larval progenies. Babesia equi (EMA-1) and Babesia caballi (BC48) gene fragments were amplified by polymerase chain reaction (PCR), in blood samples, and partially fed-females and egg and larval progenies of Dermacentor nuttalli, collected from horses in Altanbulag, Tuv Province, Mongolia. While Babesia parasite DNA was detected in some horse blood samples during the first PCR, all positive cases in partially fed-female ticks, eggs and larvae were confirmed by nested PCR. Present study reinforces earlier similar findings in unfed D. nuttalli ticks collected from an open space vegetation in Bayanonjuul, Tuv Prov...
