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Bugno-Poniewierska M, Jankowska M, Raudsepp T, Kowalska K, Pawlina-Tyszko K, Szmatola T. Molecular cytogenetic screening of sex chromosome abnormalities in young horse populations. Equine Vet J 2024; 56:786-795. [PMID: 38785417 DOI: 10.1111/evj.14097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Accepted: 03/21/2024] [Indexed: 05/25/2024]
Abstract
BACKGROUND Chromosomal abnormalities occur in the equine population at a rate of approximately 2%. The use of molecular cytogenetic techniques allows a more accurate identification of chromosomal abnormalities, especially those with a low rate of abnormal metaphases, demonstrating that the actual incidence in equine populations is higher. OBJECTIVES Estimation of the number of carriers of karyotypic abnormalities in a sample from a population of young horses of various breeds, using molecular cytogenetic techniques. STUDY DESIGN Cross-sectional. METHODS Venous blood samples were collected from 500 young horses representing 5 breeds (Purebred Arabian, Hucul, Polish primitive horse [Konik], Małopolska, Coldblood, Silesian). Chromosomes and DNA were obtained from blood lymphocytes and evaluated by fluorescence in situ hybridisation (FISH) and PCR, using probes and markers for the sex chromosomes and select autosomes. RESULTS Nineteen horses, 18 mares and 1 stallion, were diagnosed with different chromosomal abnormalities: 17 cases of mosaic forms of sex chromosome aneuploidies with a very low incidence (0.6%-4.7%), one case of a SRY-negative 64,XY sex reversal mare, and one mare with X-autosome translocation. The percentage of sex chromosomal aberrations was established as 3.8% in the whole population, 6.08% in females and 0.49% in males. MAIN LIMITATIONS Limited sample size, confined to horses from Poland. CONCLUSIONS The rate of sex chromosomal abnormalities we identified was almost double that reported in previous population studies that used classical chromosome staining techniques. FISH allowed the detection of aneuploid cell lines which had a very low incidence. The FISH technique is a faster and more precise method for karyotype examination; however, it is usually focused on only one or two chromosomes while banding karyotyping includes the entire chromosome set.
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Affiliation(s)
- Monika Bugno-Poniewierska
- Department of Animal Reproduction, Anatomy and Genomics, University of Agriculture in Krakow, Krakow, Poland
| | - Magdalena Jankowska
- Department of Animal Molecular Biology, National Research Institute of Animal Production, Balice, Poland
| | - Terje Raudsepp
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, Texas, USA
| | - Katarzyna Kowalska
- Department of Animal Molecular Biology, National Research Institute of Animal Production, Balice, Poland
| | - Klaudia Pawlina-Tyszko
- Department of Animal Molecular Biology, National Research Institute of Animal Production, Balice, Poland
| | - Tomasz Szmatola
- Department of Animal Molecular Biology, National Research Institute of Animal Production, Balice, Poland
- Centre of Experimental and Innovative Medicine, University of Agriculture in Krakow, Krakow, Poland
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Shilton CA, Kahler A, Roach JM, Raudsepp T, de Mestre AM. Lethal variants of equine pregnancy: is it the placenta or foetus leading the conceptus in the wrong direction? Reprod Fertil Dev 2022; 35:51-69. [PMID: 36592981 DOI: 10.1071/rd22239] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Embryonic and foetal loss remain one of the greatest challenges in equine reproductive health with 5-10% of established day 15 pregnancies and a further 5-10% of day 70 pregnancies failing to produce a viable foal. The underlying reason for these losses is variable but ultimately most cases will be attributed to pathologies of the environment of the developing embryo and later foetus, or a defect intrinsic to the embryo itself that leads to lethality at any stage of gestation right up to birth. Historically, much research has focused on the maternal endometrium, endocrine and immune responses in pregnancy and pregnancy loss, as well as infectious agents such as pathogens, and until recently very little was known about the both small and large genetic variants associated with reduced foetal viability in the horse. In this review, we first introduce key aspects of equine placental and foetal development. We then discuss incidence, risk factors and causes of pregnancy loss, with the latter focusing on genetic variants described to date that can impact equine foetal viability.
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Affiliation(s)
- Charlotte A Shilton
- Department of Comparative Biomedical Sciences, The Royal Veterinary College, Hawkshead Lane, Herts, AL9 7TA, UK
| | - Anne Kahler
- Department of Comparative Biomedical Sciences, The Royal Veterinary College, Hawkshead Lane, Herts, AL9 7TA, UK
| | - Jessica M Roach
- Department of Comparative Biomedical Sciences, The Royal Veterinary College, Hawkshead Lane, Herts, AL9 7TA, UK
| | - Terje Raudsepp
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843-4458, USA
| | - Amanda M de Mestre
- Department of Comparative Biomedical Sciences, The Royal Veterinary College, Hawkshead Lane, Herts, AL9 7TA, UK
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Horse Clinical Cytogenetics: Recurrent Themes and Novel Findings. Animals (Basel) 2021; 11:ani11030831. [PMID: 33809432 PMCID: PMC8001954 DOI: 10.3390/ani11030831] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 03/12/2021] [Accepted: 03/13/2021] [Indexed: 12/17/2022] Open
Abstract
Clinical cytogenetic studies in horses have been ongoing for over half a century and clearly demonstrate that chromosomal disorders are among the most common non-infectious causes of decreased fertility, infertility, and congenital defects. Large-scale cytogenetic surveys show that almost 30% of horses with reproductive or developmental problems have chromosome aberrations, whereas abnormal karyotypes are found in only 2-5% of the general population. Among the many chromosome abnormalities reported in the horse, most are unique or rare. However, all surveys agree that there are two recurrent conditions: X-monosomy and SRY-negative XY male-to-female sex reversal, making up approximately 35% and 11% of all chromosome abnormalities, respectively. The two are signature conditions for the horse and rare or absent in other domestic species. The progress in equine genomics and the development of molecular tools, have qualitatively improved clinical cytogenetics today, allowing for refined characterization of aberrations and understanding the underlying molecular mechanisms. While cutting-edge genomics tools promise further improvements in chromosome analysis, they will not entirely replace traditional cytogenetics, which still is the most straightforward, cost-effective, and fastest approach for the initial evaluation of potential breeding animals and horses with reproductive or developmental disorders.
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Shilton CA, Kahler A, Davis BW, Crabtree JR, Crowhurst J, McGladdery AJ, Wathes DC, Raudsepp T, de Mestre AM. Whole genome analysis reveals aneuploidies in early pregnancy loss in the horse. Sci Rep 2020; 10:13314. [PMID: 32769994 PMCID: PMC7415156 DOI: 10.1038/s41598-020-69967-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 07/20/2020] [Indexed: 01/10/2023] Open
Abstract
The first 8 weeks of pregnancy is a critical time, with the majority of pregnancy losses occurring during this period. Abnormal chromosome number (aneuploidy) is a common finding in human miscarriage, yet is rarely reported in domestic animals. Equine early pregnancy loss (EPL) has no diagnosis in over 80% of cases. The aim of this study was to characterise aneuploidies associated with equine EPL. Genomic DNA from clinical cases of spontaneous miscarriage (EPLs; 14-65 days of gestation) and healthy control placentae (various gestational ages) were assessed using a high density genotyping array. Aneuploidy was detected in 12/55 EPLs (21.8%), and 0/15 healthy control placentae. Whole genome sequencing (30X) and digital droplet PCR (ddPCR) validated results. The majority of these aneuploidies have never been reported in live born equines, supporting their embryonic/fetal lethality. Aneuploidies were detected in both placental and fetal compartments. Rodents are currently used to study how maternal ageing impacts aneuploidy risk, however the differences in reproductive biology is a limitation of this model. We present the first evidence of aneuploidy in naturally occurring equine EPLs at a similar rate to human miscarriage. We therefore suggest the horse as an alternative to rodent models to study mechanisms resulting in aneuploid pregnancies.
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Affiliation(s)
- Charlotte A Shilton
- Department of Comparative Biomedical Sciences, The Royal Veterinary College, University of London, London, UK
| | - Anne Kahler
- Department of Comparative Biomedical Sciences, The Royal Veterinary College, University of London, London, UK
| | - Brian W Davis
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, USA
| | | | | | | | - D Claire Wathes
- Department of Production and Population Health, The Royal Veterinary College, University of London, Hatfield, UK
| | - Terje Raudsepp
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, USA
| | - Amanda M de Mestre
- Department of Comparative Biomedical Sciences, The Royal Veterinary College, University of London, London, UK.
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Abstract
Reproductive disorders are genetically heterogeneous and complex; available genetic tests are limited to chromosome analysis and 1 susceptibility gene. Cytogenetic analysis should be the first test to confirm or rule out chromosomal aberrations. No causative genes/mutations are known. The only available genetic test for stallion subfertility is based on a susceptibility gene FKBP6. The ongoing progress in equine genomics will improve the status of genetic testing. However, because subfertile phenotypes do not facilitate collection of large numbers of samples or pedigrees, and clinical causes of many cases remain unknown, further progress requires constructive cross-talk between geneticists, clinicians, breeders, and owners.
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Affiliation(s)
- Terje Raudsepp
- Department of Veterinary Integrative Biosciences, Molecular Cytogenetics Laboratory, Texas A&M University, College of Veterinary Medicine and Biomedical Sciences, Veterinary Research Building Room 306, 588 Raymond Stotzer Parkway, College Station, TX 77843-4458, USA.
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Ghosh S, Das PJ, Avila F, Thwaits BK, Chowdhary BP, Raudsepp T. A Non-Reciprocal Autosomal Translocation 64,XX, t(4;10)(q21;p15) in an Arabian Mare with Repeated Early Embryonic Loss. Reprod Domest Anim 2015; 51:171-4. [PMID: 26547799 DOI: 10.1111/rda.12636] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Accepted: 10/06/2015] [Indexed: 11/30/2022]
Abstract
Balanced autosomal translocations are a known cause for repeated early embryonic loss (REEL) in horses. In most cases, carriers of such translocations are phenotypically normal, but the chromosomal aberration negatively affects gametogenesis giving rise to both genetically balanced and unbalanced gametes. The latter, if involved in fertilization, result in REEL, whereas gametes with the balanced form of translocation will pass the defect into next generation. Therefore, in order to reduce the incidence of REEL, identification of translocation carriers is critical. Here, we report about a phenotypically normal 3-year-old Arabian mare that had repeated resorption of conceptuses prior to day 45 of gestation and was diagnosed with REEL. Conventional and molecular cytogenetic analyses revealed that the mare had normal chromosome number 64,XX but carried a non-mosaic and non-reciprocal autosomal translocation t(4;10)(q21;p15). This is a novel translocation described in horses with REEL and the first such report in Arabians. Previous cases of REEL due to autosomal translocations have exclusively involved Thoroughbreds. The findings underscore the importance of routine cytogenetic screening of breeding animals.
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Affiliation(s)
- S Ghosh
- Texas A&M University, College Station, TX, USA
| | - P J Das
- National Research Centre on Yak, Dirang, Arunachal Pradesh, India
| | - F Avila
- Department of Veterinary Population Medicine, University of Minnesota, St. Paul, MN, USA
| | | | | | - T Raudsepp
- Texas A&M University, College Station, TX, USA
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Lear TL, Raudsepp T, Lundquist JM, Brown SE. Repeated Early Embryonic Loss in a Thoroughbred Mare with a Chromosomal Translocation [64,XX,t(2;13)]. J Equine Vet Sci 2014. [DOI: 10.1016/j.jevs.2014.01.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Bugno M, Słota E, Pieńkowska-schelling A, Schelling C. Identification of chromosome abnormalities in the horse using a panel of chromosome-specific painting probes generated by microdissection. Acta Vet Hung 2009; 57:369-81. [PMID: 19635709 DOI: 10.1556/avet.57.2009.3.3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Fluorescent in situ hybridisation (FISH) using a panel of molecular probes for all chromosome pairs obtained by chromosome microdissection of the domestic horse ( Equus caballus ) was used to diagnose karyotype abnormalities in 35 horses (32 mares, 2 stallions and 1 intersex), which were selected for the study due to infertility (23 horses), reduced fertility (10 horses) and developmental anomalies (2 horses). The use of the FISH technique with probes for each horse chromosome pair enabled the diagnosis of many different chromosome aberrations in this population. Among the horses analysed, 21 animals had normal karyotype - 64,XX (19 mares) and 64,XY (2 stallions). Fourteen animals, constituting 40% of the population studied, showed the following chromosome abnormalities: 63,X (1 mare); 63,X/64,XX (6 mares); 63,X/64,XX/65,XXX (3 mares); 63,X/65,XXX (1 mare); 64,XX/65,XX+Xp (1 mare); 63,X/64,XX/65,XX+Xq (1 mare), and 63,X/64,XX/65,XX+delY (1 intersex). When only the mares studied because of complete infertility were taken into consideration, this proportion exceeded 56%. Due to the increased frequency of the above-mentioned aberrations in the mosaic form of two or more lines, it was necessary to analyse a large number (100-300) of metaphase spreads. The use of specific molecular probes obtained by chromosome microdissection made these diagnoses much easier.
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Affiliation(s)
- Monika Bugno
- 1 National Research Institute of Animal Production Department of Immuno- and Cytogenetics Krakowska 1 32-083 Balice/Kraków Poland
| | - Ewa Słota
- 1 National Research Institute of Animal Production Department of Immuno- and Cytogenetics Krakowska 1 32-083 Balice/Kraków Poland
| | | | - Claude Schelling
- 3 Vetsuisse Faculty University of Zurich Department of Veterinary Medicine Zurich Switzerland
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9
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Lear TL, Lundquist J, Zent WW, Fishback WD, Clark A. Three autosomal chromosome translocations associated with repeated early embryonic loss (REEL) in the domestic horse (Equus caballus). Cytogenet Genome Res 2008; 120:117-22. [PMID: 18467834 DOI: 10.1159/000118749] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/05/2007] [Indexed: 11/19/2022] Open
Abstract
Repeated early embryonic loss (REEL) represents a considerable economic loss to the horse industry. Mares that experience REEL may be overlooked as potential carriers of a chromosome abnormality. Here we report three different autosomal translocations in Thoroughbred mares presented for chromosome analysis because of REEL. The karyotypes were 64,XX,t(1;21), 64,XX,t(16;22), and 64,XX,t(4;13), respectively. In order to confirm the chromosomes involved in the translocations, to map the breakpoints, and to determine if the translocations were reciprocal, genes surrounding the breakpoints were identified using existing maps and from the newly assembled horse genome sequence. Bacterial artificial chromosomes containing the genes of interest were identified and mapped to the translocation chromosomes by fluorescence in situ hybridization (FISH). FISH confirmed that the t(16;22) and t(4;13) translocations were reciprocal, while the t(1;21) was not. The breakpoints on horse chromosomes 1 and 16 appear to be the same or near breakpoints previously identified in translocations. These breakpoints are at the fusion boundary of human chromosomes 10 and 15 on horse chromosome 1 and at human chromosome 3p and 3q on horse chromosome 16. These sites may represent ancient breakpoints reused during equid evolution. Overall, chromosome abnormalities may have a greater influence on mare fertility than previously known. Thus, it is important to karyotype subfertile mares exhibiting REEL.
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Affiliation(s)
- T L Lear
- Maxwell H. Gluck Equine Research Center, Veterinary Science Department, University of Kentucky, Lexington, KY, USA.
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10
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Lear T, Bailey E. Equine clinical cytogenetics: the past and future. Cytogenet Genome Res 2008; 120:42-9. [DOI: 10.1159/000118739] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/11/2008] [Indexed: 11/19/2022] Open
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11
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Homolka D, Ivanek R, Capkova J, Jansa P, Forejt J. Chromosomal rearrangement interferes with meiotic X chromosome inactivation. Genome Res 2007; 17:1431-7. [PMID: 17717048 PMCID: PMC1987340 DOI: 10.1101/gr.6520107] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Heterozygosity for certain mouse and human chromosomal rearrangements is characterized by the incomplete meiotic synapsis of rearranged chromosomes, by their colocalization with the XY body in primary spermatocytes, and by male-limited sterility. Previously, we argued that such X-autosomal associations could interfere with meiotic sex chromosome inactivation. Recently, supporting evidence has reported modifications of histones in rearranged chromosomes by a process called the meiotic silencing of unsynapsed chromatin (MSUC). Here, we report on the transcriptional down-regulation of genes within the unsynapsed region of the rearranged mouse chromosome 17, and on the subsequent disturbance of X chromosome inactivation. The partial transcriptional suppression of genes in the unsynapsed chromatin was most prominent prior to the mid-pachytene stage of primary spermatocytes. Later, during the mid-late pachytene, the rearranged autosomes colocalized with the XY body, and the X chromosome failed to undergo proper transcriptional silencing. Our findings provide direct evidence on the MSUC acting at the mRNA level, and implicate that autosomal asynapsis in meiosis may cause male sterility by interfering with meiotic sex chromosome inactivation.
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Affiliation(s)
- David Homolka
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Robert Ivanek
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Jana Capkova
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Petr Jansa
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
| | - Jiri Forejt
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, 142 20 Prague 4, Czech Republic
- Corresponding author.E-mail ; fax 420-24106-2154
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Lear TL, Layton G. Use of zoo-FISH to characterise a reciprocal translocation in a thoroughbred mare: t(1;1 6)(q16;q21.3). Equine Vet J 2002; 34:207-9. [PMID: 11902765 DOI: 10.2746/042516402776767295] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- T L Lear
- Maxwell H. Gluck Equine Research Centre, Department of Veterinary Science, University of Kentucky, Lexington 40546, USA
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Bowling AT, Breen M, Chowdhary BP, Hirota K, Lear T, Millon LV, Ponce de Leon FA, Raudsepp T, Stranzinger G. International system for cytogenetic nomenclature of the domestic horse. Report of the Third International Committee for the Standardization of the domestic horse karyotype, Davis, CA, USA, 1996. Chromosome Res 1997; 5:433-43. [PMID: 9421259 DOI: 10.1023/a:1018408811881] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- A T Bowling
- School of Veterinary Medicine, University of California, Davis 95616-8744, USA
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