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American journal of veterinary research2001; 62(1); 97-103; doi: 10.2460/ajvr.2001.62.97

Incidence of the endothelin receptor B mutation that causes lethal white foal syndrome in white-patterned horses.

Abstract: To determine incidence of the Ile118Lys endothelin receptor B (EDNRB) mutation responsible for overo lethal white syndrome (OLWS) and its association with specific types of white patterning. Methods: 945 horses of white-patterned bloodlines and 55 solid-colored horses of other breeds. Methods: Horses were genotyped by use of allele-specific polymerase chain reaction to determine incidence of the Ile118Lys EDNRB mutation. Results: Genotypes detected were homozygous Ile118, homozygous Lys118, and heterozygous. All foals with OLWS were homozygous for the Ile118Lys EDNRB mutation, and adults that were homozygous were not found. White patterning was strongly associated with EDNRB genotype. Color patterns with highest incidence (> 94%) of heterozygotes were frame overo, highly white calico overo, and frame blend overo. White-patterned bloodlines with lowest incidence of heterozygotes (< 21 %) were tobiano, sabino, minimally white calico overo, splashed white overo, nonframe blend overo, and breeding-stock solid. The mutation was not detected in solid-colored horses from breeds without white patterning. Conclusions: In homozygotes, the Ile118Lys EDNRB mutation causes OLWS. In heterozygotes, the mutation is usually responsible for a frame overo phenotype. The frame pattern can be combined with other white patterns, making accurate estimation of EDNRB genotype by visual inspection difficult. Wide range of incidence of heterozygotes in various subtypes of white-patterned horses indicates different genetic control of these color patterns. Determination of EDNRB genotype by use of a DNA-based test is the only way to determine with certainty whether white-patterned horses can produce a foal affected with OLWS.
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Publication Date: 2001-02-24 PubMed ID: 11197568DOI: 10.2460/ajvr.2001.62.97Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

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.

The research sought to explore the prevalence of a specific genetic mutation linked to lethal white foal syndrome in particular horse breeds with varied white patterns. It was discovered that the mutation often appears in frame overo phenotype, making identification challenging due to the combination of various white patterns.

Study Methodology

  • The study included a sample of 945 white-patterned horses and 55 solid-colored horses from different breeds.
  • They used allele-specific polymerase chain reaction to establish the incidence of the Ile118Lys EDNRB mutation in the subjects.
  • During the research, it was observed that the horses’ genotypes could be divided into homozygous Ile118, homozygous Lys118, and heterozygous.

Results

  • All the foals suffering from overo lethal white syndrome (OLWS) were homozygous for the Ile118Lys EDNRB mutation.
  • No adult horses were found to be homozygous for the mutation.
  • The study points out a strong association between white patterning in horses and the EDNRB genotype.
  • Color patterns such as frame overo, highly white calico overo, and frame blend overo displayed the highest incidence of heterozygotes, with more than 94% of them showing these patterns.
  • Minimal incidence (< 21%) of heterozygotes was notable in breeds such as tobiano, sabino, minimally white calico overo, splashed white overo, nonframe blend overo, and breeding-stock solid.
  • The Ile118Lys EDNRB mutation was not detected in solid-colored horses from breeds without white patterning.

Conclusions

  • The study concluded that the Ile118Lys EDNRB mutation induces OLWS in homozygotes.
  • For heterozygotes, this mutation is generally linked to a frame overo phenotype.
  • The frame pattern could blend with other white patterns, which complicates accurate determination of the EDNRB genotype by visual inspection.
  • The results indicated a diverse range of heterozygotes in different subtypes of white-patterned horses, suggesting different genetic controls of these color patterns.
  • The only way to definitely determine whether a white-patterned horse can produce a foal affected by OLWS is by using a DNA-based test for the EDNRB genotype.

Cite This Article

APA
Santschi EM, Vrotsos PD, Purdy AK, Mickelson JR. (2001). Incidence of the endothelin receptor B mutation that causes lethal white foal syndrome in white-patterned horses. Am J Vet Res, 62(1), 97-103. https://doi.org/10.2460/ajvr.2001.62.97

Publication

American journal of veterinary research
ISSN: 0002-9645
NlmUniqueID: 0375011
Country: United States
Language: English
Volume: 62
Issue: 1
Pages: 97-103

Researcher Affiliations

Santschi, E M
  • Department of Clinical and Population Sciences, College of Veterinary Medicine, University of Minnesota, St Paul 55108, USA.
Vrotsos, P D
    Purdy, A K
      Mickelson, J R

        MeSH Terms

        • Amino Acid Substitution
        • Animals
        • Female
        • Fetal Death / genetics
        • Fetal Death / veterinary
        • Genes, Lethal
        • Genetic Carrier Screening
        • Hair Color / genetics
        • Homozygote
        • Horse Diseases / embryology
        • Horse Diseases / genetics
        • Horses / genetics
        • Isoleucine
        • Lysine
        • Mutation
        • Pregnancy
        • Receptor, Endothelin B
        • Receptors, Endothelin / genetics
        • Syndrome

        Citations

        This article has been cited 6 times.
        1. Obradovic NA, McFadden A, Martin K, Vierra M, McLoone K, Martin E, Thomas A, Everts RE, Brooks SA, Lafayette C. Three Novel KIT Polymorphisms Found in Horses with White Coat Color Phenotypes. Animals (Basel) 2025 Mar 22;15(7).
          doi: 10.3390/ani15070915pubmed: 40218308google scholar: lookup
        2. McFadden A, Vierra M, Martin K, Brooks SA, Everts RE, Lafayette C. Spotting the Pattern: A Review on White Coat Color in the Domestic Horse. Animals (Basel) 2024 Jan 30;14(3).
          doi: 10.3390/ani14030451pubmed: 38338094google scholar: lookup
        3. Gianino GM, Valberg SJ, Perumbakkam S, Henry ML, Gardner K, Penedo C, Finno CJ. Prevalence of the E321G MYH1 variant for immune-mediated myositis and nonexertional rhabdomyolysis in performance subgroups of American Quarter Horses. J Vet Intern Med 2019 Mar;33(2):897-901.
          doi: 10.1111/jvim.15393pubmed: 30623495google scholar: lookup
        4. Strain GM. The Genetics of Deafness in Domestic Animals. Front Vet Sci 2015;2:29.
          doi: 10.3389/fvets.2015.00029pubmed: 26664958google scholar: lookup
        5. Haase B, Signer-Hasler H, Binns MM, Obexer-Ruff G, Hauswirth R, Bellone RR, Burger D, Rieder S, Wade CM, Leeb T. Accumulating mutations in series of haplotypes at the KIT and MITF loci are major determinants of white markings in Franches-Montagnes horses. PLoS One 2013;8(9):e75071.
          doi: 10.1371/journal.pone.0075071pubmed: 24098679google scholar: lookup
        6. Brosnahan MM, Brooks SA, Antczak DF. Equine clinical genomics: A clinician's primer. Equine Vet J 2010 Oct;42(7):658-70.
          doi: 10.1111/j.2042-3306.2010.00166.xpubmed: 20840582google scholar: lookup
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