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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.
A dinucleotide mutation in the endothelin-B receptor gene is associated with lethal white foal syndrome (LWFS); a horse variant of Hirschsprung disease. Lethal white foal syndrome (LWFS) is a congenital anomaly of horses characterized by a white coat colour and aganglionosis of the bowel, which is similar to Hirschsprung disease (HSCR). We decided to investigate possible mutations of the endothelin-B receptor gene ( EDNRB ) in LWFS as recent studies in mutant rodents and some patients have demonstrated EDNRB defects. First, we identified a full-length cDNA for horse EDNRB . This cDNA fragment contained a 1329 bp open reading frame which encoded 443 amino acid residues. The predicted amino acid sequence was 89, 91 and 85% identical to human, bo...
A dinucleotide mutation in the endothelin-B receptor gene is associated with lethal white foal syndrome (LWFS); a horse variant of Hirschsprung disease. Lethal white foal syndrome (LWFS) is a congenital anomaly of horses characterized by a white coat colour and aganglionosis of the bowel, which is similar to Hirschsprung disease (HSCR). We decided to investigate possible mutations of the endothelin-B receptor gene ( EDNRB ) in LWFS as recent studies in mutant rodents and some patients have demonstrated EDNRB defects. First, we identified a full-length cDNA for horse EDNRB . This cDNA fragment contained a 1329 bp open reading frame which encoded 443 amino acid residues. The predicted amino acid sequence was 89, 91 and 85% identical to human, bo...
Cloning of equine interleukin 1 receptor antagonist and determination of its full-length cDNA sequence. To clone equine interleukin 1 receptor antagonist (IL-1ra) and determine its full-length cDNA sequence. Methods: A cDNA library derived from lipopolysaccharide-stimulated equine monocytes was screened by means of plaque hybridization to radiolabeled equine IL-1ra DNA probes generated by means of the polymerase chain reaction. The cDNA nucleotide sequence for equine IL-1ra was determined by use of the dideoxy chain termination technique, analyzed by use of computer software for sequence characteristics, and compared with sequences reported for IL-1ra of other species. Results: The cDNA of equin...
CLoning of equine interleukin 1 alpha and equine interleukin 1 beta and determination of their full-length cDNA sequences. To clone equine interleukin 1 alpha (IL-1 alpha) and equine interleukin 1 beta (IL-1 beta) and determine their full-length cDNA sequences. Methods: The mRNA isolated from lipopolysaccharide-stimulated cultured equine monocytes was reverse transcribed, and a cDNA library was constructed in a lambda phage. The cDNA library was screened by means of plaque hybridization with radiolabeled human IL-1 alpha and IL-1 beta cDNA probes. The cDNA nucleotide sequences for equine IL-1 alpha and equine IL-1 beta were determined by use of the dideoxy chain termination technique. The cDNA sequences were analy...
Intrafollicular insulin-like growth factor-binding protein levels in equine ovarian follicles during preovulatory maturation and regression. The profiles of insulin-like growth factor-binding proteins (IGFBPs) in follicular fluid have been characterized in a number of mammals (rats, pigs, sheep, cattle, humans) and are good indicators of follicular status. We studied the IGFBP profiles of equine serum and ovarian follicular fluid recovered at various stages of the follicular phase. The levels of IGFBPs were related to the morphology and the steroidogenic activity of the follicles. Follicular fluids were recovered by ultrasound-guided follicular aspiration. In the first experiment, the dominant follicles of 10 mares were partly punc...
Production and characterization of Ehrlichia risticii, the agent of Potomac horse fever, from snails (Pleuroceridae: Juga spp.) in aquarium culture and genetic comparison to equine strains. We report on the production and characterization of Ehrlichia risticii, the agent of Potomac horse fever (PHF), from snails (Pleuroceridae: Juga spp.) maintained in aquarium culture and compare it genetically to equine strains. Snails were collected from stream waters on a pasture in Siskiyou County, Calif., where PHF is enzootic and were maintained for several weeks in freshwater aquaria in the laboratory. Upon exposure to temperatures above 22 degrees C the snails released trematode cercariae tentatively identified as virgulate cercariae. Fragments of three different genes (genes for 16S rRN...
Comparisons of three probability formulae for parentage exclusion. Three general formulae calibrate the average capability of marker systems to dispute falsely reported pedigree records in uniparous species. The most familiar exclusion formula applies to paternity, although the same formula applies equally to maternity. Another formula faults the relationship of a single offspring with its putative parent; for example, where the genotype of the other parent is not available. The remaining formulae excludes both of the falsely recorded parents of a substituted offspring. Simplified forms of the three general formulae facilitate the calculation of maximal avera...
Characterization of the haemolytic activity of Streptococcus equi. The haemolytic activity of Streptococcus equi, the cause of equine strangles, was characterized. Production of haemolysin in Todd Hewitt broth was dependent on an equine serum supplement and the logarithmic phase of growth after which activity declined sharply. RNA core also induced haemolysin production from cells harvested at the end of the logarithmic phase of growth. Haemolysis was not affected by cholesterol, was only slightly increased in reducing conditions and was completely inactivated by trypan blue, identifying the haemolytic activity as streptolysin S-like (SLS-like). Purification ...
A conserved structural element in horse and mouse IGF2 genes binds a methylation sensitive factor. The equine IGF2 gene has been cloned and characterised. It spans a 9 kb region, which is substantially less than the corresponding human gene. Three coding exons and three untranslated leader exons, all highly homologous to those in other species, were identified. Downstream of the polyadenylation site in exon 6, a dinucleotide repeat sequence was identified. Three putative promoters (P1-P3) were localised in the 5' region of the gene. RNase protection analysis revealed two active promoters in fetal tissues, P2 and P3, whereas P3 was the only promoter active in adult tissues. This represents a...
Equine infectious anemia virus transactivator is a homeodomain-type protein. Lentiviral transactivator (Tat) proteins are essential for viral replication. Tat proteins of human immunodeficiency virus type 1 and bovine immunodeficiency virus form complexes with their respective RNA targets (Tat responsive element, TAR), and specific binding of the equine anemia virus (EIAV) Tat protein to a target TAR RNA is suggested by mutational analysis of the TAR RNA. Structural data on equine infectious anemia virus Tat protein reveal a helix-loop-helix-turn-helix limit structure very similar to homeobox domains that are known to bind specifically to DNA. Here we report results of...
A missense mutation in the endothelin-B receptor gene is associated with Lethal White Foal Syndrome: an equine version of Hirschsprung disease. Lethal White Foal Syndrome is a disease associated with horse breeds that register white coat spotting patterns. Breedings between particular spotted horses, generally described as frame overo, produce some foals that, in contrast to their parents, are all white or nearly all white and die shortly after birth of severe intestinal blockage. These foals have aganglionosis characterized by a lack of submucosal and myenteric ganglia from the distal small intestine to the large intestine, similar to human Hirschsprung Disease. Some sporadic and familial cases of Hirschsprung Disease are due to muta...
Cumulus expansion, chromatin configuration and meiotic competence in horse oocytes: a new hypothesis. When recovered from the follicle, horse oocytes may be categorised as having either a compact or an expanded cumulus. Cumulus expansion is strongly associated with follicle atresia. Oocytes with expanded and compact cumuli have similar proportions in the germinal vesicle stage when recovered from the follicle. However, during in vitro culture, a higher proportion of oocytes with expanded cumuli mature, and they do so more quickly, than do oocytes with compact cumuli. Using Hoechst 33258 to label chromatin, in the germinal-vesicle stage horse oocytes can be divided into those in which the nucle...
Arthroscopic removal of palmar/plantar osteochondral fragments (POF) in the metacarpo- and metatarso-phalangeal joints of standardbred trotters–outcome and possible genetic background to POF. A clinical material of 133 Standardbred horses with palmar/plantar osteochondral fragments (POF) in the metacarpo- and metatarsophalangeal joints were studied. All horses had their fragments removed with arthroscopic surgery. 102 of the horses were 3 years old or younger when surgery was performed. Anatomical localisations of the fragments were in agreement with earlier reports. There was no statistical significant difference in month of birth in the POF--group compared to the total population. Eighty % of the horses that had raced before surgery came back to racing. The racing performance rel...
Treatment of equine oocytes with A23187 after intracytoplasmic sperm injection. In vitro matured horse oocytes with a first polar body (n = 68) were each injected with a single spermatozoon and divided into 2 groups: Group 1 oocytes were treated with 10 microM calcium ionophore A23187 for 5 min while Group 2 oocytes received no activation treatment. After culture in vitro for 2 days, significantly more oocytes treated with A23187 (5/24, 21%) cleaved than oocytes without activation treatment (2/44, 5%, P<0.05). All 7 cleaved zygotes from both treatment groups were transferred to recipient mares but no pregnancies resulted.
Parentage testing of Day 10 equine embryos by amplified PCR analysis of microsatellites. Paternity analysis was performed on the DNA of 21 equine embryos collected nonsurgically 10 days after ovulation from known mares, but involving 3 possible sires. After extraction, the DNA of each embryo was typed by radioactive PCR amplification using 10 characterised microsatellites; HMS 1, 2, 5, 6, 7 and 8 (Guérin et al. 1994) and HTG 3, 4, 6 and 10 (Marklund et al. 1994). The 21 dams and 3 sires were genotyped using DNA extracted from blood and amplified by PCR. After electrophoresis and autoradiography of the PCR products of the embryo and parents, the alleles of the embryo were compared...
Spontaneous multiple ovulation and development of multiple embryonic vesicles in a mare. A Warmblood mare was observed to ovulate spontaneously 12 follicles within 2 days, none of which exceeded 22 mm in diameter. On Days 13 and 17 after ovulation, 6 embryonic vesicles were identified in the uterus by ultrasonography but by Day 26, 5 of the vesicles had disappeared. Development of the surviving conceptus was monitored until Day 42. Plasma progesterone concentrations rose to 14 ng/ml on Day 7, decreased over the next 8 days and then plateaued to around 4-6 ng/ml until Day 70. The occurrence of multiple spontaneous ovulations was diagnosed repeatedly in this mare. However, the devel...
Effect of anti-freeze protein (AFP) on the cooling and freezing of equine embryos as measured by DAPI-staining. Equine embryos recovered on Day 6 after ovulation were cooled to +4 degrees C, or frozen with AFP alone or together with glycerol. Twenty embryos (140-200 microm in diameter) were randomly assigned to 6 treatment groups. In the first 3 groups, the embryos were cooled from room temperature to +4 degrees C at a rate of 3 degrees C/min and warmed again at a rate of 32 degrees C/min in a programmable freezer. In the second 3 groups, the embryos were frozen using a standard protocol, stored in liquid nitrogen for 5-7 days and then thawed in a 37 degrees C waterbath. After cooling/warming or freezin...
A single base transversion in the flanking region of an equine microsatellite locus affects amplification of one allele. The equine dinucleotide microsatellite HMS7 is part of a microsatellite panel utilized in a parentage verification programme at the Veterinary Genetics Laboratory (Davis, California, USA). Apparent non-Mendelian inheritance was noted when a Quarter Horse mare was excluded as the parent of two offspring based on analysis of the HMS7 locus. The mare's DNA type qualified her as a parent of the offspring at an additional 20 microsatellite loci. The three animals appeared homozygous for HMS7 with each possessing an allele different from that of the other two animals. Polymerase chain reaction prime...
[Activities of the enzymes LDH, gamma-GT, GOT, GPT and lactoperoxidase in the milk of breeding mares during the course of lactation]. Milk samples were collected from 44 mares (trotters, warm blood horses, quarter horses) during lactation between the 1st and 90th day p.p. at 20 defined days. The activity of the enzymes LDH, gamma-GT, GOT, GPT and lactoperoxidase was investigated. The aim of this study was to find out the changes of these parameters during lactation and whether an influence of race, conception, date of foaling, age and number of lactations existed on the enzyme activities in mare's milk. The following results were obtained: In mare's milk the LDH-activity was highest (xg = 629 x 1.5 +/- 1 U/l) on the 1st day ...
Interindividual variation in total and carrier-mediated lactate influx into red blood cells. To study in standardbred horses interindividual variation in the influx of lactate into red blood cells, venous blood samples were collected from 89 horses from 2 wk to 9 yr of age. For 62 horses, the rate of influx was normally distributed with a mean rate of 4.09 nmol.mg protein-1.min-1 at a lactate concentration of 10 mM, and the respective value for the other 27 horses was 0.58 nmol.mg protein-1.min-1. At 30 mM of lactate, the rates were 8.71 and 1.97 nmol.mg protein-1.min-1, respectively. This bimodal distribution was independent of age. In horses with high transport activity, the monocar...
Adenosine and hypoxanthine transport in horse erythrocytes: evidence for a polymorphism in the transport of hypoxanthine via a sodium-dependent cotransporter. The inward transport of two purines, adenosine and hypoxanthine, at 37 degrees C by horse erythrocytes was compared. No mediated transport of adenosine was detected in horse erythrocytes, nor was saturable, high-affinity binding of the potent facilitated-diffusion inhibitor nitrobenzylthioinosine demonstrable in horse erythrocyte membranes. In contrast, erythrocytes from most horses possessed a saturable sodium-dependent hypoxanthine transporter (apparent K(m), 100 +/- 28 microM; Vmax, 0.20 +/- 0.08 mmol (l cells)-1 h-1; means +/- S.E.M., n = 5). Guanine inhibited hypoxanthine influx (apparent...
An aspartic proteinase expressed in the equine placenta. This manuscript describes the cloning of a novel aspartic proteinase expressed in the placenta of the horse (order Perrisodactyla). Evidence for similar genes in the cat (Carnivora) and ruminants (Artiodactyla), indicates that these molecules have been conserved within widely divergent species with distinct types of placentation. Since ePAG is produced by the outer cell layer (trophoblast) of the placenta, it can tentatively be grouped with the pregnancy-associated glycoproteins (PAG) of cattle, sheep, and pig. The high sequence identity that ePAG shares with pepsinogens as well as the PAG, in...
Isolation of Actinobacillus equuli from the oral cavity of healthy horses and comparison of isolates by restriction enzyme digestion and pulsed-field gel electrophoresis. Swab samples were collected from the oral cavity of 174 horses in 10 farms and cultured selectively for Actinobacillus equuli. A. equuli could be isolated from 37% of all samples, varying between 12 and 88% in the different farms. Eight horses were sampled repeatedly for several days, with a variation in isolation frequency between 50 and 88%. Isolates were compared by restriction enzyme digestion and Pulsed-Field Gel Electrophoresis. A high degree of strain variability was found within each horse population as well as some variability over time between strains isolated from the same horse.
Biological characterization of Rev variation in equine infectious anemia virus. Sequence analysis identified significant variation in the second exon of equine infectious anemia virus (EIAV) rev. Functional analysis indicated that limited amino acid variation in Rev significantly altered the export activity of the protein but did not affect Rev-dependent alternative splicing. EIAV Rev can mediate export through two independent cis-acting Rev-responsive elements (RREs), and differences among Rev variants were more pronounced when both RREs were present. Variation in Rev may be an important mechanism for regulation of virus replication in vivo and may contribute to changes ...
Characterization of a microsatellite in the promoter region of the IGF1 gene in domestic horses and other equids. Insulin-like growth factor 1 (IGF1) regulates growth and metabolic functions in vertebrates. A dinucleotide repeat sequence located at the promoter region of the IGF1 gene has been reported in several vertebrate species and may affect the control of the transcriptional activity of this gene. The genotypes of animals from seven horse breeds were determined in order to study the potential association of allelic forms of this microsatellite with adult body size differences found in domestic horses. Among these breeds, five alleles were found. Breed-specific differences in adult body size could no...
