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Animal genetics2010; 41 Suppl 2; 41-52; doi: 10.1111/j.1365-2052.2010.02101.x

Molecular heterogeneity of XY sex reversal in horses.

Abstract: Male-to-female 64,XY sex reversal is a frequently reported chromosome abnormality in horses. Despite this, the molecular causes of the condition are as yet poorly understood. This is partially because only limited molecular information is available for the horse Y chromosome (ECAY). Here, we used the recently developed ECAY map and carried out the first comprehensive study of the Y chromosome in XY mares (n=18). The integrity of the ECAY in XY females was studied by FISH and PCR using markers evenly distributed along the euchromatic region. The results showed that the XY sex reversal condition in horses has two molecularly distinct forms: (i) a Y-linked form that is characterized by Y chromosome deletions and (ii) a non-Y-linked form where the Y chromosome of affected females is molecularly the same as in normal males. Further analysis of the Y-linked form (13 cases) showed that the condition is molecularly heterogeneous: the smallest deletions spanned about 21 kb, while the largest involved the entire euchromatic region. Regardless of the size, all deletions included the SRY gene. We show that the deletions were likely caused by inter-chromatid recombination events between repeated sequences in ECAY. Further, we hypothesize that the occurrence of SRY-negative XY females in some species (horse, human) but not in others (pig, dog) is because of differences in the organization of the Y chromosome. Finally, in contrast to the Y-linked SRY-negative form of equine XY sex reversal, the molecular causes of SRY-positive XY mares (5 cases) remain as yet undefined.
© 2010 The Authors, Journal compilation © 2010 Stichting International Foundation for Animal Genetics.
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Publication Date: 2010-11-26 PubMed ID: 21070275DOI: 10.1111/j.1365-2052.2010.02101.xGoogle Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research focuses on exploring the molecular reasons behind XY sex reversal in horses. This condition often leads to male horses developing as females. The scientists used advanced technology to study the Y chromosome in horses and discovered that there are two distinct forms of this condition.

Molecular Varieties of XY Sex Reversal

  • The research found two distinct molecular forms for the occurrence of XY sex reversal in horses. This discovery was made through a comprehensive study of the Y chromosome using the newly developed equine Y chromosome (ECAY) map.
  • The first form of the condition is Y-linked, characterized by deletions on the Y chromosome. The other is a non-Y-linked form where the Y chromosome in affected females is the same as in normal males.

Y-Linked Form and Its Characteristics

  • Further analyzes on the Y-linked form revealed that the condition is not homogeneous at the molecular level. The deletions on the Y chromosome varied in size, ranging from about 21 kilobases to deletions enveloping the entire euchromatic region.
  • The SRY gene, pivotal for male development, was included in all deletions regardless of the size. The study conceptually infers that these deletions were most likely caused by recombination events between repeated sequences on the equine Y chromosome.

Speculation About SRY-Negative Instances

  • The research paper also theorizes on why SRY-negative XY females are found in some species like horses and humans but not in others like pigs and dogs. It speculates that the reasons lie in the differences in the structural organization of the Y chromosome.

Unclear Causes of SRY-Positive XY Mares

  • In contrast to the Y-linked SRY-negative equine XY sex reversal, the molecular causes for SRY-positive XY mares are still undefined. The study stresses the need for continued research in this area to get more clarity on the causes of the condition.

Cite This Article

APA
Raudsepp T, Durkin K, Lear TL, Das PJ, Avila F, Kachroo P, Chowdhary BP. (2010). Molecular heterogeneity of XY sex reversal in horses. Anim Genet, 41 Suppl 2, 41-52. https://doi.org/10.1111/j.1365-2052.2010.02101.x

Publication

Animal genetics
ISSN: 1365-2052
NlmUniqueID: 8605704
Country: England
Language: English
Volume: 41 Suppl 2
Pages: 41-52

Researcher Affiliations

Raudsepp, T
  • Department of Veterinary Integrative Biosciences, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4458, USA. traudsepp@cvm.tamu.edu
Durkin, K
    Lear, T L
      Das, P J
        Avila, F
          Kachroo, P
            Chowdhary, B P

              MeSH Terms

              • Animals
              • Chromosome Deletion
              • Chromosomes, Artificial, Bacterial
              • Cloning, Molecular
              • Cytogenetic Analysis
              • Disorders of Sex Development / genetics
              • Disorders of Sex Development / veterinary
              • Female
              • Genetic Heterogeneity
              • Horse Diseases / genetics
              • Horses / genetics
              • Sex-Determining Region Y Protein / genetics
              • Y Chromosome

              Citations

              This article has been cited 20 times.
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