A karyotype in horses refers to the complete set of chromosomes present in the cells of a horse, typically organized in a systematic arrangement for analysis. Horses generally have 64 chromosomes, comprising 31 pairs of autosomes and one pair of sex chromosomes. Karyotyping is employed to study chromosomal abnormalities that may affect equine development, fertility, and overall health. It provides insights into genetic disorders, hereditary conditions, and breed-specific traits. This page compiles peer-reviewed research studies and scholarly articles that explore the methodology, findings, and implications of karyotype analysis in equine genetics.
Lear TL, Trembicki KA, Ennis RB.Giemsa-11 (G-11) staining and in situ hybridization were used to identify the equine chromosome complement of horse x mouse somatic cell hybrids. The presence of horse chromosomes in somatic cell hybrids was determined by differential G-11 staining. The slides were then destained and hybridized with biotinylated total horse (Equus caballus) genomic DNA without suppression. Fluorescence detection permitted rapid confirmation of horse chromosomal DNA in the hybrid cells.
The Journal of hereditySeptember 1, 1991
Volume 82, Issue 5 369-377 doi: 10.1093/oxfordjournals.jhered.a111106
Wichman HA, Payne CT, Ryder OA, Hamilton MJ, Maltbie M, Baker RJ.We describe a molecular model for rapid chromosomal evolution that proposes tandemly repeated DNA sequences as a driving force. A prediction of this model is that when extensive rearrangements of euchromatin have been facilitated by heterochromatin, genomes will be characterized by tandemly repeated sequences that have actively changed chromosomal fields by intragenomic movement. Alternatively, it is proposed that in conservative chromosomal lineage each class of tandemly repeated sequences will be restricted to a specific chromosomal field. To provide baseline data to test this model we exami...
Blythe LL, Hultgren BD, Craig AM, Appell LH, Lassen ED, Mattson DE, Duffield D.A clinical, viral, hematologic , and genetic study was conducted over a 4-year period on a family of Appaloosas with high incidence of clinical ataxia and pathologic features of equine degenerative myeloencephalopathy. Marginal to deficient serum vitamin E (alpha-tocopherol) and blood selenium values were the only other consistent antemortem abnormalities in the affected horses. Members of this family were all descendants of a clinically normal mare and were raised in 3 separate environments with variable quality of feed. All horses had access to pasture grasses. Normal chromosomal karyotypes ...
Kenney RM, Kent MG, Garcia MC, Hurtgen JP.A total of 174 stallions were subjected to a standard fertility examination and classified as fertile, subfertile or sterile. All stallions were phenotypical males involved in breeding programmes with no detectable abnormalities in their reproductive organs. Fertile stallions had no history of any breeding problem. Subfertile stallions were referred with a history of a breeding problem that was subsequently determined not to be attributable to the mares or infectious diseases. They were divided into chromosomally normal and abnormal groups on the basis of karyotype. The relative DNA content of...
Bowling AT, Millon LV.The phenotypic effects in a yearling Arab filly of a newly described equine autosomal trisomy syndrome for chromosome 30 (65,XX,+30) consisted of small size and severe angular deviation of front legs accompanied by mild polydactyly, but no mental dullness. This case was associated with advanced maternal age. Additional banding studies of a second trisomy case confirmed the assignment to chromosome 26 (64,XX,-26,+t(26q26q)) and evidence of her fertility was presented.
Stewart-Scott IA, Pearce PD, Burkin DJ.Sex chromosome abnormalities have been detected in a further five mares with clinical histories of small ovaries and absent or irregular oestrous cycles. Three mares had 63,XO karyotypes (X monosomy) and two were sex chromosome mosaics with karyotypes of 63,XO/64,XY and 63,XO/64,XX/64,XY respectively. A sex chromosome abnormality (X monosomy) has also been found in a filly where it was suspected because of her short stature.
Richer CL, Power MM, Klunder LR, McFeely RA, Kent MG.The following decisions concerning the banded karyotype of the horse (Equus caballus) were made at the second International conference for Standardization of Domestic Animal Karyotypes, held at Jouy-en Josas, France, 22nd-26th May 1989: (1) numbering of the chromosomes was modified to correspond to an arrangement into only two groups (the non-acrocentrics and the acrocentrics) within which the autosomes are placed according to length alone; (2) a more compact karyotype arrangement was adopted: chromosomes 1 to 5 on the first row, 6 to 10 on the second, 11 to 13, and, at the far right, X and Y ...
Cribiu EP, Chaffaux S.With the exception of bovine freemartinism, intersexuality is rarely reported in domestic animals. The few cases of intersexuality reported here in dogs, cattle, goats, sheep and horses were classified according to the karyotype. The XX intersexes described here included goats which were either polled male pseudohermaphrodites or true hermaphrodites and dogs which were female pseudohermaphrodites. Among the XY intersexes studied, one dog was a true hermaphrodite, whereas the others were male pseudohermaphrodites, all mares showed gonadal dysgenesis and one cow was a female pseudohermaphrodite....
Hinrichs K, Riera FL, Klunder LR.Embryo transfer was performed in three mares with gonadal dysgenesis. Karyotypes of the mares were as follows: Mare 1, 63,XX, 64,XX, 65,XX; Mare 2, 63,X; and Mare 3, 65,XXX. The mares were administered progesterone in oil, 300 mg intramuscularly daily, starting 1 or 2 days after donor mare ovulation. Embryos were transferred on day 7 after donor ovulation. Mare 1 became pregnant after the first embryo transfer and had a normally developing fetus on necropsy on day 45 of gestation. Mare 3 became pregnant after the third embryo transfer, but the embryo was lost between day 14 and day 18 of gesta...
Messier PE, Drouin R, Richer CL.We present an immunochemical technique for the detection of 5-bromo-2'-deoxyuridine (BrdU) incorporated discontinuously into the chromosomal DNA. A monoclonal anti-BrdU antibody and a protein A-gold complex were used to produce chromosome banding of human and equine chromosomes, specific for electron microscopy (EM). Well-defined bands, symmetry of sister chromatids, concordance between homologues, and band patterns similar to those observed by light microscopy facilitate chromosome identification and karyotyping. From prophase to late metaphase, chromosomes condense and bands appear to fuse. ...
Zong E, Fan G.Generally speaking, the majority of F1 hybrids between the horse and donkey are sterile and do conform to the hypothesis of gametogenic breakdown. The results of our own research, nevertheless, lead us to conclude that there is variability in degree of sterility and fertility for both F1 and B1 individuals, with a gradual advance from sterility to fertility being seen. This is the subject we will discuss from the point of view of oestrus, ovulation, mating, pregnancy, spermatogenesis, endocrine activity, isozymes and karyotypic analysis in this paper.
Moreno-Millan M, Delgado Bermejo JV, Lopez Castillo G.An X-trisomy has been detected in an intersexuality Spanish-bred horse by using G- and C-banding methods. The external characteristics and the behavioural and physiological irregularities of the horse are described. This is the first time that an association between an X-trisomy and a case of intersexuality has been reported in any domestic animal.
Herzog A, Höhn H, Klug E, Hecht W.In a 7 months old foal with a male pseudohermaphroditism the cytogenetic investigation revealed a XO/XYY-mosaic with a centric fusion of the Y-chromosomes.
Power MM.The results of Y chromosome measurements in 31 horses are presented. The Y chromosome was identified using G-, R-, and C-banding techniques. From G-banded metaphase spreads, total X and Y chromosome and separate proximal (P) and distal (D) Y-band measurements were made. Within this group, the Y/X ratio (%) for each animal varied from 18.93 to 43.95, with an overall mean of 34.85 and a coefficient of variation (CV) of 16.12. The overall mean P/X ratio (%) was 23.57 with a CV of 20.57, compared with an overall mean D/X ratio (%) of 11.26 with a CV of 15.18. The group studied included 27 Thorough...
Safronova LD, Pimenova TI.The cytogenetic study performed has shown that karyotyping of meiotic cells can be based on the synaptonemal complexes (SC) of spreading pachytene spermatocytes of bull and of horse. The horse SC karyotype has not been previously described. A comparison of the relative length of SC with metaphase chromosomes of bull and horse somatic cells has revealed the correspondence of the chromosome length in pachytene of meiosis and metaphase, which is in agreement with the data on house mouse and Chinese hamster. The method of spreading pachytene cells may be of great practical importance in studies of...
Gill JJ, Kempski HM, Hallows BJ, Warren AM.IT is well known that chromosomal abnormalities are
frequently associated with infertility in the mare (Table 1). The
most commonly reported abnormality is 6 3 x 0 which can
occur in a mosaic or non-mosaic form. Various other
aneuploidies of the sex chromosomes have been reported but
the 6SXXX genotype appears to be rare. Chandley et a1 (1975)
and Chandley (1984) have reported two 65XXX animals and
Walker (1979) a 64XW6SXXW6SXXY one.
This paper reports a mosaic 64XXh5XXX animal and
emphasises the need for more cytogenetic analysis in the
horse.
Long SE.Nine reproductively normal mares, 25 infertile mares and one set of heterosexual twins were examined cytogenetically using conventional giemsa staining, C-banding and G-banding. It was concluded that G-banding was necessary to identify even gross anomalies. Three (12 per cent) of the infertile mares, but none of the controls, had a chromosomal anomaly. One was 63,XO, one a 63,XO/64,XX mixoploid and one a 64,XY sex reversed male. It is argued that a cytogenetic examination is a useful diagnostic technique but that routine screening of the whole population would be uneconomic.
Kent MG, Elliston KO, Shroeder W, Guise KS, Wachtel SS.In situ hybridization with a cloned banded krait sex-specific repetitive DNA probe (Bkm) indicates a high concentration of Bkm sequences on the horse Y chromosome in both normal XY males and XY sex-reversed females. Lesser, but still significant, concentrations of Bkm sequences were mapped to horse chromosomes 3, 4, and 30.
White KL, Thomson DL, Wood TC.An indirect immunofluorescence assay was used to detect the presence of H-Y antigen on equine blastocysts. A total of 33 blastocyst stage horse embryos were collected 6 to 7 days post-ovulation by trans-cervical flush and were immediately evaluated for the presence of H-Y antigen. Additionally, 17 embryos, were collected and cultured for 72 h to the expanded blastocyst stage and similarly evaluated. Embryos were placed in medium containing monoclonal antibodies to H-Y antigen followed by incubation in medium containing 1/10 (v/v) fluorescein isothiocyanate conjugated goat anti-mouse IgM Fc spe...
Romagnano A, Richer CL, King WA, Betteridge KJ.To define the time of X-chromosome inactivation in the horse, 122 conceptuses were collected transcervically between Days 6 and 28 (ovulation = Day 0) and subjected to cytogenetic analysis: 59 of the embryos were divided and in 41 of these separate cytogenetic analysis of the embryonic disc and remaining tissues was possible. Conceptuses were measured and photographed before capsule removal, culture in the presence of 5-bromodeoxyuridine and subsequent fixation for cytogenetic analysis. On average, 15 slides were prepared per conceptus. C-banding was used to determine the sex of each conceptus...
Bowling AT, Millon L, Hughes JP.Chromosomal abnormality was detectable in 98 of 180 mares aged 3 years or over with gonadal dysgenesis. The most common abnormality was X monosomy (63,X). The second most common abnormality was a karyotype indistinguishable by G- or C-banding from that of a male horse (64,XY). Two mares demonstrated structural abnormality of one X chromosome [64,X,del(Xp)] which has not previously been reported in horses. One of these foaled a filly with the same karyotype as her dam. Blood typing confirmed parentage of the foal. This is the only example in our experience of fertility in a mare with gonadal dy...
Power MM.Two unrelated chromosome abnormalities were found in equine half sibs. The proposita, Case 1, which was short in stature and infertile, had a de novo unbalanced X;15 translocation involving loss of Xp. Replication studies indicated that the translocated X was preferentially late replicating and that this late replication spread variably into the autosomal segment. Case 2, a half brother of the proposita, was short in stature, had cryptorchidism, and was trisomic for chromosome 28. Cytogenetic analysis of the dam, the sire of Case 1, and two other phenotypically normal half sibs revealed normal...
Romagnano A, Richer CL, Messier PE, Jean P.Silver staining shows the presence in the domestic horse of six NORs located on chromosomes 1, 26 and 31 as identified after R-banding. Following electron microscopy, the argyrophilic material was observed outside the terminal secondary constrictions (satellite stalks) on the terminal portion of the short arm of chromosome 1, outside the secondary constrictions on the proximal region of the long arms of chromosome 31, and beside the proximal region of the long arms of chromosome 26. Satellite staining applied to these chromosomes appears to reveal only the active NORs.
Mäkinen A, Katila T, Kuokkanen MT.Only one X chromosome was found in each of the lymphocyte metaphases studied in an infertile mare. Karyotype analysis was made with the CBG and GTG banding techniques. The most obvious clinical abnormality was gonadal hypoplasia.
Kent MG, Shoffner RN, Buoen L, Weber AF.The XY sex-reversal syndrome occurs when a phenotypic mare is born that has the karyotype of a stallion. The syndrome is manifested by both genotypic and phenotypic heterogeneity. The sex-reversed genetic condition occurs frequently within certain pedigrees where XY females have been found and can be readily detected by chromosome karyotyping. The phenotypic spectrum ranges from the feminine mare with a reproductive tract that is within normal limits to the greatly masculinized mare. Pedigree analysis suggests that there are two modes of inheritance: (1) an X-linked recessive or autosomal sex-...
Short RV.The infertility of the mule has proved a continuing challenge to scientific thought. Since the chromosomal differences between the two parental species are so great as to render normal meiosis impossible, it is postulated that all mules and hinnies are sterile. The problem now is to explain how mules and hinnies can occasionally produce spermatozoa or ova. The appearance of the mule was sufficient to persuade the ancients that both parents, not just the male, must contribute to the make-up of the offspring. The mule has also taught us that, when the number of oocytes in the ovary is reduced, t...
Blue MG.The objective of this study was to investigate an hypothesis that chromosome anomalies are an important cause of prenatal loss in the mare. An attempt was made to analyse, cytogenetically, a series of 26 equine abortuses. Cell cultures were prepared from a range of tissues, but failed to grow, and chromosome analysis was therefore not possible for any of these specimens. Consequently, a study was made of the metaphase chromosomes prepared from 22 equine embryos after their surgical removal from mares' uteri. The karyotypes prepared for each specimen were normal. The current findings are discus...
Romagnano A, Richer CL, King WA, Betteridge KJ.To define the time of X-chromosome inactivation in the horse, 122 conceptuses were collected transcervically between Days 6 and 28 (ovulation = Day 0) and subjected to cytogenetic analysis: 59 of the embryos were divided and in 41 of these separate cytogenetic analysis of the embryonic disc and remaining tissues was possible. Conceptuses were measured and photographed before capsule removal, culture in the presence of 5-bromodeoxyuridine and subsequent fixation for cytogenetic analysis. On average, 15 slides were prepared per conceptus. C-banding was used to determine the sex of each conceptus...
McFeely RA.The karyotype of the horse consists of 64 chromosomes; 18 pairs have a terminal centromere and 13 pairs a non-terminal centromere. Identification of individual chromosomes is enhanced by the use of band-staining techniques which allow recognition of minor structural rearrangements of chromatin material. Seven previously reported cases of male pseudohermaphroditism with chromosome studies are reviewed. Three were genetic females, one was basically an XX/XY chimaera, one was an XX/XXY chimaera, and one was an XXXY. Also reviewed is an infertile mare with 63 chromosomes and no distinguishable sex...
Bugno M, Klukowka-Rötzler J, Słota E, Witarski W, Gerber V, Leeb T.The physical localization of the epidermal growth factor receptor (EGFR) gene was performed on donkey chromosomes. Bacterial artificial chromosome DNA containing the equine EGFR gene was used to map this gene by fluorescent in situ hybridization on donkey metaphase chromosomes. The gene was mapped on donkey 1q21.1 region.
Witarski W, Kij B, Nowak A, Bugno-Poniewierska M.A hucul mare with reproductive abnormalities was examined during karyotype analysis. The karyotype was analysed based on evaluation of 860 metaphase plates in chromosome preparations. The use of fluorescence in situ hybridization (FISH) with an X chromosome painting probe showed premature X chromosome separation in 9.5% cases of examined chromosome spreads. In this report, we present the first identify premature centromere division (PCD) as a possible cause of abnormal X chromosome morphology in horses and as a probable cause of reproductive difficulties.
Bornstein S.Two intersex horses were characterized externally by vulva and “enlarged clitoris-hypoplastic penis” and internally by uterus and testicles. Both had a normal female karyotype 64/XX. One of the horses whose body measurements were in accordance with mares of the same breed, showed a distinct stallion behaviour.
Dunn HO, Smiley D, Duncan JR, McEntee K.The karyotypes of a Welsh pony and a Standardbred were 64,XX/64,XY and 63,XO/64,XY respectively. Both intersexes were true hermaphrodites with bilateral ovotestes. Neither intersex showed stallion-like behaviour. Each one had an underdeveloped penis, bilateral seminal vesicles and uterine tissue. It would appear that the chimerism in these equine intersexes resulted from double fertilization or fusion of blastocysts. Mosaicism in the Standardbred is a possibility, resulting from loss of a Y chromosome by anaphase lag in an early embryonic XY cell.
Zhao CJ, Qin YH, Lee XH, Wu Ch.An alleged male foal of a female mule, whose sire and grandparents were unknown, was identified for its pedigree. Parentage testing was conducted by comparing polymorphism of 12 microsatellite DNA sites and mitochondrial D-loop sequences of the male foal and the female mule. Both the sequence analysis of species-specific DNA fragments and a cytogenetic analysis were performed to identify the species of the foal and its parents. The results showed that the alleged female mule is actually a hinny, and the male foal, which possesses 62 chromosomes, qualifies as an offspring of the female hinny an...
Kent MG, Elliston KO, Shroeder W, Guise KS, Wachtel SS.In situ hybridization with a cloned banded krait sex-specific repetitive DNA probe (Bkm) indicates a high concentration of Bkm sequences on the horse Y chromosome in both normal XY males and XY sex-reversed females. Lesser, but still significant, concentrations of Bkm sequences were mapped to horse chromosomes 3, 4, and 30.
Basrur PK, Kanagawa H, Podliachouk L.An intersex horse exhibiting cell types of different sex chromosome constitution was subjected to further studies in order to determine whether the house was a mosaic or a chimera. Cultures of gonadal tissue and peripheral blood revealed mainly 64/XX and 64/XY cells, the former predominating in both tissues. The frequency of drumstick-bearing poly-morphonuclear neutrophils in the intersex horse was similar to that noted in normal mares. Blood type analysis using 17 naturally occurring agglutinins and hemolysins revealed partial agglutinations with three antibodies for the factors of the A syst...
Lindgren G, Breen M, Godard S, Bowling A, Murray J, Scavone M, Skow L, Sandberg K, Guérin G, Binns M, Ellegren H.We report fluorescence in-situ hybridization (FISH) and somatic cell hybrid mapping data for 13 different horse genes (ANP, CD2, CLU, CRISP3, CYP17, FGG, IL1RN, IL10, MMP13, PRM1, PTGS2, TNFA and TP53). Primers for PCR amplification of intronic or untranslated regions were designed from horse-specific DNA or mRNA sequences in GenBank. Two different horse bacterial artificial chromosome (BAC) libraries were screened with PCR for clones containing these 13 Type I loci, nine of which were found in the libraries. BAC clones were used as probes in dual colour FISH to confirm their precise chromosom...
Safronova LD, Pimenova TI.The cytogenetic study performed has shown that karyotyping of meiotic cells can be based on the synaptonemal complexes (SC) of spreading pachytene spermatocytes of bull and of horse. The horse SC karyotype has not been previously described. A comparison of the relative length of SC with metaphase chromosomes of bull and horse somatic cells has revealed the correspondence of the chromosome length in pachytene of meiosis and metaphase, which is in agreement with the data on house mouse and Chinese hamster. The method of spreading pachytene cells may be of great practical importance in studies of...
Wnuk M, Oklejewicz B, Lewinska A, Zabek T, Bartosz G, Slota E, Bugno-Poniewierska M.The fluorescence in situ hybridization (FISH) technique is widely used in animal cytogenetics. Contrary to FISH procedure, primed in situ DNA synthesis (PRINS) does not require the DNA probe preparation (design, synthesis, gel purification of PCR products and labeling). The PRINS method with primers used as 'DNA probes' is both PCR-sensitive and allows for chromosomal localization of DNA sequences. Here, we show the application of PRINS reaction with one unlabeled oligonucleotide pair to identify 18S rDNA loci in three different animal species: domestic pig (Sus scrofa), red fox (Vulpes vulpes...
Al-Jaru A, Goodwin W, Skidmore J, Raudsepp T, Khazanehdari K.Chromosome configurations and chiasma frequency during the metaphase I stage of spermatogenesis in the male horse are characterized in this work. The genome-wide frequency and distribution of chiasmata was detected as 49.45 ± 2.07 for 14 fertile stallions. All X and Y chromosomes shared a single chiasma at their pseudoautosomal region, while 1-4 chiasmata were observed in autosomal chromosomes. The chiasma frequency and distribution were further studied for 8 different bivalents identified by FISH in 5 fertile stallions. Genetic length was calculated from chiasmata data for the whole genome a...
Mäkelä O, Gustavsson I, Hollmén T.Chromosomal analysis is not a routine examination in equine
practice. It is indicated, however, in infertile or subfertile
mares with small, inactive ovaries (Chandley et a/. 1975;
Power 1986).
The most commonly reported abnormalities in mares
concern sex chromosomes such as 63,XO and mosaic
63,XO/64,XX giving sterile mares and 64,XY resulting in
gonadal dysgenesis, sex reversal and testicular feminisation
(Power 1990). The phenotypic manifestations of a horse with
these karyotypic abnormalities are usually quite mild
compared with the corresponding abnormalities in man. These
mild ...
Richer CL, Romagnano A.Both dynamic G-banding and cell synchronization produced by bromodeoxyuridine (BrdU), were applied to equine chromosomes. BrdU incorporated during the first half of the S-phase is taken up into the R-bands that are early replicating. These bands, which have incorporated BrdU, cannot contract as usual and remain elongated; only the other regions of the chromosome, i.e., the G-bands, contract normally and are sharply defined. BrdU also can be used for cell synchronization. The addition of BrdU in a high concentration, 15 hours before harvest, and its removal 11 hours later, has two effects: init...
Maia L, Dias MC, de Moraes CN, de Paula Freitas-Dell'Aqua C, da Mota LS, Santiloni V, da Cruz Landim-Alvarenga F.Cryopreservation is a feasible alternative to maintaining several cell lines, particularly for immediate therapeutic use, transportation of samples, and implementation of new in vitro studies. This work parts from the hypothesis that the medium of cryopreservation composed by 90% of conditioned medium (CM) supports cryopreservation of equine umbilical cord intervascular matrix mesenchymal stem cells (UCIM-MSCs), allowing the maintenance of the biological properties for the establishment of cell banks intended for therapeutic use and in vitro studies. Thus, we evaluated the viability, apoptosis...
Howden KJ.A Thoroughbred mare was presented for stallion-like behavior. Reproductive and ultrasonographic evaluation, testosterone assays, and karyotyping confirmed a diagnosis of androgen insensitivity syndrome (64, XY--testicular feminization). Surgery to remove abdominal testicles was successful in alleviating the behavioral abnormality. This condition is discussed with reference to the current literature. Une jument Thoroughbred a été présentée parce qu’elle avait un comportement d’étalon. Une évaluation reproductrice et échographique, des dosages de testostérone et un caryotypage ont c...
Perrocheau M, Boutreux V, Chadi-Taourit S, Di Meo GP, Perucatti A, Incarnato D, Cribiu EP, Guérin G, Iannuzzi L.The INRA and the CHORI-241 horse BAC libraries were screened by hybridization with DNA probes and/or directly by PCR with primers designed in consensus sequences of genes localized at the end of each human chromosome. BAC clones were retrieved and 36 could be FISH mapped after the expected gene was confirmed in each BAC by sequencing. Our results show that 16 BACs can be considered to be at telomeric or centromeric positions in the horse and 15 were found at the boundary of actually defined conserved segments even-though often located within conserved syntenic fragments between horse and human...
Ghosh S, Kjöllerström J, Metcalfe L, Reed S, Juras R, Raudsepp T.We present cytogenetic and genotyping analysis of a Thoroughbred foal with congenital neurologic disorders and its phenotypically normal dam. We show that the foal has non-mosaic trisomy for chromosome 26 (ECA26) but normal 2n = 64 diploid number because two copies of ECA26 form a metacentric derivative chromosome der(26q;26q). The dam has normal 64,XX karyotype indicating that der(26q;26q) in the foal originates from errors in parental meiosis or post-fertilization events. Genotyping ECA26 microsatellites in the foal and its dam suggests that trisomy ECA26 is likely of maternal origin and tha...
Kuiper H, Blum N, Distl O.In a 1.5-year-old Oldenburg horse, a clitoris-like structure instead of a penis was identified in the prepuce. The external genital organs did not show any abnormalities at visual inspection except that exteriorization of the penis was not possible, not even under general anesthesia. The horse's owner observed a continuous dripping of urine and a tendency to mild colics beginning 2 weeks after birth. Testosterone concentration was 0.01 ng/ml and therefore under the threshold for geldings, and the horse did not respond to the application of gonadotropin-releasing hormone (GnRH). The inner genit...
Messier PE, Drouin R, Richer CL.We present an immunochemical technique for the detection of 5-bromo-2'-deoxyuridine (BrdU) incorporated discontinuously into the chromosomal DNA. A monoclonal anti-BrdU antibody and a protein A-gold complex were used to produce chromosome banding of human and equine chromosomes, specific for electron microscopy (EM). Well-defined bands, symmetry of sister chromatids, concordance between homologues, and band patterns similar to those observed by light microscopy facilitate chromosome identification and karyotyping. From prophase to late metaphase, chromosomes condense and bands appear to fuse. ...
Neuhauser S, Handler J, Schelling C, Pieńkowska-Schelling A.Chromosomal abnormalities are notable causes of infertility in horses. Mares show various degrees of estrous behavior, and ultrasound examination often reveals an underdeveloped genital tract. This article reports investigations on fertility in a Haflinger sibship with a healthy, normally developed, fertile mare with at least three healthy offspring. Chromosomal analysis performed incidentally and blinded for this mare revealed 63,X/64,XX/65,XXX mosaicism. Two closely related mares were also mosaics (63,X/64,XX), and one of them was a carrier of a marker chromosome. Repeated examinations of th...
Rubes J, Borkovec L, Horínová Z, Urbanová J, Proroková I, Kulíková L.Cytogenetic examinations were carried out in 13 cattle farms, two herds of horses, one stag farm and 13 pig farms in areas with different levels of environmental contamination. The frequency of aberrant cells per 100 mitoses was 3.67 +/- 1.89 in pigs (n = 260) and 4.16 +/- 2.4 in herbivores (n = 497). This is a significant difference (p < 0.01). Ten times higher frequencies of chromatid exchanges were found in pigs. The examined herds were classified into three groups by the level of environmental contamination (satisfactory, impaired and severely impaired environment). Significant differen...
Haynes SE, Reisner AH.Although no major structural or numerical abnormalities were found in the karyotypes of 12 aborted equine fetuses, two unrelated abortuses each carried a large polymorphism for the amount of heterochromatin in chromosome 1. In both karyotypes this chromosome was shown to be larger than its homolog. To determine the nature of the extra DNA in these chromosomes, equine DNA was isolated and characterized by buoyant density analysis. Equine mainband DNA had a buoyant density in neutral CsCl of 1.699 g/cm3, while the highly repetitive (dG+dC)-rich fraction had a buoyant density of 1.715 g/cm3. A ra...
Pompermayer E, Ysebaert MP, Vinardell T, Oikawa MA, Jonhson JP, Fernandes T, David F.A two-year-old Arabian horse presented for abnormal external genitalia and dangerous stallion-like behavior was diagnosed with disorder of sexual development (DSD), also known as intersex/hermaphroditism. Standing 1-stage surgical procedure performed under sedation, and local anesthesia to concurrently eliminate stallion-like behavior, risk of neoplastic transformation of intraabdominal gonads, and to replace ambiguous external genital with a functional, and cosmetically more acceptable anatomy. Step-1) Laparoscopic abdominal exploration and gonadectomy; Step-2) Rudimentary penis resection and...
Valera M, Karlau A, Anaya G, Bugno-Poniewierska M, Molina A, Encina A, Azor PJ, Demyda-Peyrás S.Sex chromosomal abnormalities are a well-established cause of reproductive failure in domestic horses. Because of its difficult diagnosis, the Pura Raza Español breeding program established a routine screening for chromosomal abnormalities in all the horses prior to enrolling in the studbook. This genomic procedure combines an initial assessment based on the results from Short Tandem Repeat (STR) parentage testing followed by a Single-Nucleotide Polymorphism (SNP) based copy number aberration (CNA) confirmative analysis in positive cases. Using this methodology, we identified five new individ...
While the centromeric function is conserved and epigenetically specified by CENP-A, centromeric DNA, typically composed of satellite repeats, is highly divergent and rapidly evolving. In the species of the genus Equus (horses, asses and zebras), also known as equids, the numerous centromeres devoid of satellite repeats enabled us to carry out molecular analysis of centromeric chromatin establishing a unique model system for mammalian centromere biology. In this review, after a brief description of the rapid evolution of equids, we outline one of our most relevant initial discoveries: the posit...
