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Waqas MS, Arroyo E, Tibary A. Diagnostic Approach to Equine Testicular Disorders. Vet Sci 2024; 11:243. [PMID: 38921990 PMCID: PMC11209109 DOI: 10.3390/vetsci11060243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Revised: 05/24/2024] [Accepted: 05/24/2024] [Indexed: 06/27/2024] Open
Abstract
Management of breeding stallions is crucial to equine reproduction. The longevity of the breeding career is the ultimate objective, whether the stallion is used for natural cover or for semen collection and artificial insemination. Stud farm veterinarians should be aware of the techniques used to evaluate testicular function and the diagnostic approach to testicular disorders in cases of emergency. This paper presents the clinical methods used to evaluate testicular health, including palpation, ultrasonography, biopsy, and fine-needle aspiration. The discussion of testicular disorders is broken down into four categories: congenital disorders (cryptorchidism, monorchidism, and testicular hypoplasia), differential diagnosis of scrotal enlargement, differential diagnosis of causes of progressive testicular enlargement, and differential diagnosis of testicular asymmetry or reduction in size with an emphasis on testicular degeneration. The sudden increase in testicular size is often accompanied by severe clinical signs and is a major cause for referral of stallion for surgery. Testicular disorders are illustrated with clinical cases seen by the authors.
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Affiliation(s)
- Muhammad-Salman Waqas
- Comparative Theriogenology, Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Center for Reproductive Biology, Washington State University, Pullman, WA 99163, USA;
| | - Eduardo Arroyo
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610, USA;
| | - Ahmed Tibary
- Comparative Theriogenology, Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Center for Reproductive Biology, Washington State University, Pullman, WA 99163, USA;
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Holmlund H, Yamauchi Y, Ruthig VA, Cocquet J, Ward MA. Return of the forgotten hero: the role of Y chromosome-encoded Zfy in male reproduction. Mol Hum Reprod 2023; 29:gaad025. [PMID: 37354519 PMCID: PMC10695432 DOI: 10.1093/molehr/gaad025] [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: 05/03/2023] [Revised: 06/06/2023] [Indexed: 06/26/2023] Open
Abstract
The Y-linked zinc finger gene ZFY is conserved across eutherians and is known to be a critical fertility factor in some species. The initial studies of the mouse homologues, Zfy1 and Zfy2, were performed using mice with spontaneous Y chromosome mutations and Zfy transgenes. These studies revealed that Zfy is involved in multiple processes during spermatogenesis, including removal of germ cells with unpaired chromosomes and control of meiotic sex chromosome inactivation during meiosis I, facilitating the progress of meiosis II, promoting spermiogenesis, and improving assisted reproduction outcomes. Zfy was also identified as a key gene in Y chromosome evolution, protecting this chromosome from extinction by serving as the executioner responsible for meiosis surveillance. Studies with targeted Zfy knock-outs revealed that mice lacking both homologues have severe spermatogenic defects and are infertile. Based on protein structure and in vitro assays, Zfy is expected to drive spermatogenesis as a transcriptional regulator. The combined evidence documents that the presence of at least one Zfy homologue is required for male fertility and that Zfy2 plays a more prominent role. This knowledge reinforces the importance of these factors for mouse spermatogenesis and informs our understanding of the human ZFY variants, which are homologous to the mouse Zfy1 and Zfy2.
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Affiliation(s)
- Hayden Holmlund
- Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI, USA
| | - Yasuhiro Yamauchi
- Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI, USA
| | - Victor A Ruthig
- Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI, USA
| | - Julie Cocquet
- Institut Cochin, INSERM, U1016, CNRS UMR8104, Universite Paris Cite, Paris, France
| | - Monika A Ward
- Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI, USA
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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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Ruiz-Herrera A, Waters PD. Fragile, unfaithful and persistent Ys-on how meiosis can shape sex chromosome evolution. Heredity (Edinb) 2022; 129:22-30. [PMID: 35459933 PMCID: PMC9273583 DOI: 10.1038/s41437-022-00532-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 03/27/2022] [Accepted: 03/28/2022] [Indexed: 12/28/2022] Open
Abstract
Sex-linked inheritance is a stark exception to Mendel's Laws of Heredity. Here we discuss how the evolution of heteromorphic sex chromosomes (mainly the Y) has been shaped by the intricacies of the meiotic programme. We propose that persistence of Y chromosomes in distantly related mammalian phylogroups can be explained in the context of pseudoautosomal region (PAR) size, meiotic pairing strategies, and the presence of Y-borne executioner genes that regulate meiotic sex chromosome inactivation. We hypothesise that variation in PAR size can be an important driver for the evolution of recombination frequencies genome wide, imposing constraints on Y fate. If small PAR size compromises XY segregation during male meiosis, the stress of producing aneuploid gametes could drive function away from the Y (i.e., a fragile Y). The Y chromosome can avoid fragility either by acquiring an achiasmatic meiotic XY pairing strategy to reduce aneuploid gamete production, or gain meiotic executioner protection (a persistent Y). Persistent Ys will then be under strong pressure to maintain high recombination rates in the PAR (and subsequently genome wide), as improper segregation has fatal consequences for germ cells. In the event that executioner protection is lost, the Y chromosome can be maintained in the population by either PAR rejuvenation (extension by addition of autosome material) or gaining achiasmatic meiotic pairing, the alternative is Y loss. Under this dynamic cyclic evolutionary scenario, understanding the meiotic programme in vertebrate and invertebrate species will be crucial to further understand the plasticity of the rise and fall of heteromorphic sex chromosomes.
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Affiliation(s)
- Aurora Ruiz-Herrera
- Genome Integrity and Instability Group, Institut de Biotecnologia i Biomedicina (IBB), Universitat Autònoma de Barcelona (UAB), Cerdanyola del Vallès, 08193, Spain.
- Departament de Biologia Cel·lular, Fisiologia i Immunologia, Universitat Autònoma de Barcelona (UAB), Cerdanyola del Vallès, 08193, Spain.
| | - Paul D Waters
- School of Biotechnology and Biomolecular Sciences, Faculty of Science, UNSW Sydney, Sydney, NSW, 2052, Australia.
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Molecular Cytogenetic and Y Copy Number Analysis of a Reciprocal ECAY-ECA13 Translocation in a Stallion with Complete Meiotic Arrest. Genes (Basel) 2021; 12:genes12121892. [PMID: 34946841 PMCID: PMC8701272 DOI: 10.3390/genes12121892] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 11/23/2021] [Accepted: 11/25/2021] [Indexed: 12/13/2022] Open
Abstract
We present a detailed molecular cytogenetic analysis of a reciprocal translocation between horse (ECA) chromosomes Y and 13 in a Friesian stallion with complete meiotic arrest and azoospermia. We use dual-color fluorescence in situ hybridization with select ECAY and ECA13 markers and show that the translocation breakpoint in ECAY is in the multicopy region and in ECA13, at the centromere. One resulting derivative chromosome, Y;13p, comprises of ECAY heterochromatin (ETSTY7 array), a small single copy and partial Y multicopy region, and ECA13p. Another derivative chromosome 13q;Y comprises of ECA13q and most of the single copy ECAY, the pseudoautosomal region and a small part of the Y multicopy region. A copy number (CN) analysis of select ECAY multicopy genes shows that the Friesian stallion has significantly (p < 0.05) reduced CNs of TSPY, ETSTY1, and ETSTY5, suggesting that the translocation may not be completely balanced, and genetic material is lost. We discuss likely meiotic behavior of abnormal chromosomes and theorize about the possible effect of the aberration on Y regulation and the progression of meiosis. The study adds a unique case to equine clinical cytogenetics and contributes to understanding the role of the Y chromosome in male meiosis.
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Castaneda C, Juras R, Kjöllerström J, Hernandez Aviles C, Teague SR, Love CC, Cothran EG, Varner DD, Raudsepp T. Thoroughbred stallion fertility is significantly associated with FKBP6 genotype but not with inbreeding or the contribution of a leading sire. Anim Genet 2021; 52:813-823. [PMID: 34610162 DOI: 10.1111/age.13142] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/09/2021] [Indexed: 12/12/2022]
Abstract
This is a follow-up study to validate the previously detected association of the FKBP6 gene with stallion subfertility. Using a select cohort of 150 Thoroughbred stallions with detailed breeding records, we confirm significant association (P < 0.0001) between low per-cycle pregnancy rates (≤50%) and a combined A/A-A/A genotype of SNPs chr13:11 353 372G>A and chr13:11 353 436A>C in FKBP6 exon 5. We also show that stallion subfertility and the combined genotype A/A-A/A are not associated with the level of genetic diversity based on 12 autosomal microsatellite markers, or with pedigree-based inbreeding rate, or the extent of contribution of a leading Thoroughbred sire, Northern Dancer, in a stallion's pedigree. We develop a TaqMan allelic discrimination assay for the two SNPs to facilitate accurate and high-throughput genotyping. We determine allele, genotype and combined genotype frequencies of FKBP6 exon 5 SNPs in a global cohort of 518 Thoroughbreds (76% stallions or geldings and 24% mares) and show that the frequency of the A/A-A/A genotype is 4%. Because there is no similar association between the FKBP6 exon 5 genotype and stallion subfertility in Hanoverians, we suggest that the two SNPs are not causative but rather tagging a breed-specific haplotype with genetic variants unique to Thoroughbreds. Further WGS-based research is needed to identify the molecular causes underlying the observed genotype-phenotype association in Thoroughbred stallions.
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Affiliation(s)
- C Castaneda
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, 77843, USA
| | - R Juras
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, 77843, USA
| | - J Kjöllerström
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, 77843, USA
| | - C Hernandez Aviles
- Department of Large Animal Clinical Sciences, Texas A&M University, College Station, TX, 77843, USA
| | - S R Teague
- Department of Large Animal Clinical Sciences, Texas A&M University, College Station, TX, 77843, USA
| | - C C Love
- Department of Large Animal Clinical Sciences, Texas A&M University, College Station, TX, 77843, USA
| | - E G Cothran
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, 77843, USA
| | - D D Varner
- Department of Large Animal Clinical Sciences, Texas A&M University, College Station, TX, 77843, USA
| | - T Raudsepp
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, 77843, USA
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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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Ghosh S, Carden CF, Juras R, Mendoza MN, Jevit MJ, Castaneda C, Phelps O, Dube J, Kelley DE, Varner DD, Love CC, Raudsepp T. Two Novel Cases of Autosomal Translocations in the Horse: Warmblood Family Segregating t(4;30) and a Cloned Arabian with a de novo t(12;25). Cytogenet Genome Res 2020; 160:688-697. [PMID: 33326979 DOI: 10.1159/000512206] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 10/07/2020] [Indexed: 11/19/2022] Open
Abstract
We report 2 novel autosomal translocations in the horse. In Case 1, a breeding stallion with a balanced t(4p;30) had produced normal foals and those with congenital abnormalities. Of his 9 phenotypically normal offspring, 4 had normal karyotypes, 4 had balanced t(4p;30), and 1 carried an unbalanced translocation with tertiary trisomy of 4p. We argue that unbalanced forms of t(4p;30) are more tolerated and result in viable congenital abnormalities, without causing embryonic death like all other known equine autosomal translocations. In Case 2, two stallions produced by somatic cell nuclear transfer from the same donor were karyotyped because of fertility issues. A balanced translocation t(12q;25) was found in one, but not in the other clone. The findings underscore the importance of routine cytogenetic screening of breeding animals and animals produced by assisted reproductive technologies. These cases will contribute to molecular studies of translocation breakpoints and their genetic consequences in the horse.
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Affiliation(s)
- Sharmila Ghosh
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | | | - Rytis Juras
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | - Mayra N Mendoza
- Estación Experimental Agraria Chincha, Dirección de Recursos Genéticos y Biotecnología, Instituto Nacional de Innovación Agraria, Ica, Peru
| | - Matthew J Jevit
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | - Caitlin Castaneda
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | - Olivia Phelps
- Powder River Veterinary Hospital & Supply, Kaycee, Wyoming, USA
| | - Jessie Dube
- Powder River Veterinary Hospital & Supply, Kaycee, Wyoming, USA
| | - Dale E Kelley
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | - Dickson D Varner
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | - Charley C Love
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA
| | - Terje Raudsepp
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA,
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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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