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Equine veterinary journal2021; 54(5); 952-957; doi: 10.1111/evj.13521

Prevalence of the E321G MYH1 variant in Brazilian Quarter Horses.

Abstract: In the Quarter Horse (QH), myosin heavy chain myopathy (MYHM), which is characterised by nonexertional rhabdomyolysis or immune-mediated myositis (IMM) with acute muscle atrophy, is strongly associated with the missense E321G MYH1 mutation. Objective: To document the existence of MYHM in the Brazilian QH population, this study includes a case report of two related QH foals with the E321G MYH1 mutation that had clinical signs of MYHM, with histological confirmation of IMM in one of the foals. This prompted an investigation the aim of which was to determine the allele frequency of the E321G MYH1 variant across QHs using a DNA archive in Brazil. Study design Cross sectional. Methods: To estimate the allele frequency of the E321G MYH1 variant in Brazilian QHs, 299 DNA samples from QHs used in different disciplines (reining, barrel racing, halter, cutting and racing) were analysed. DNA fragments containing the region with the mutation were amplified by PCR and used for direct genomic sequencing. Results: Of the 299 genotyped QHs, 44 animals (14.7%) were heterozygous (My/N) for the E321G MYH1 variant, and 255 (85.3%) were homozygous for the wild-type allele (N/N), implying an allele frequency of 0.074. Reining horses had a significantly higher prevalence of heterozygosity than horses in other disciplines (P = .008). Conclusions: The DNA samples were collected from 2010 to 2014. As only registered QHs were evaluated, the results may not reflect the actual incidence in the general population of Brazilian QHs. Conclusions: The reported cases of MYHM and the high prevalence of the MYH1 mutation found in the assessed Brazilian QH population, particularly in reining QHs, suggests that MYHM should be included in genetic screening. Reasonable control measures are important to prevent an increase in the incidence of MYHM in QHs in Brazil.
© 2021 EVJ Ltd.
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Publication Date: 2021-10-28 PubMed ID: 34606642DOI: 10.1111/evj.13521Google 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 study investigates the occurrence and frequency of the E321G MYH1 genetic mutation, which is associated with a condition known as myosin heavy chain myopathy (MYHM) in Brazilian Quarter Horses. The researchers found that this mutation was present in a significant number of these horses, suggesting that genetic screening for this mutation could be beneficial in managing this horse breed in Brazil.

Background and Objective

  • The researchers were investigating a specific genetic mutation (E321G MYH1) in Quarter Horses in Brazil. This mutation is associated with myosin heavy chain myopathy (MYHM), a condition characterised by nonexertional rhabdomyolysis or immune-mediated myositis (muscle inflammation) leading to acute muscle atrophy.
  • This investigation was prompted by two related cases of Quarter Horses with this mutation, who showed signs of MYHM.
  • The objective was to document the existence of MYHM in the Brazilian Quarter Horse population, and to determine how common this genetic variant is among these horses.

Methodology

  • The researchers tested DNA samples from 299 Quarter Horses, used in different equestrian disciplines including reining, barrel racing, halter, cutting and racing.
  • They performed a Polymerase Chain Reaction (PCR) to amplify DNA fragments containing the region where the mutation occurs and later analysed these fragments via genomic sequencing.

Results

  • Of the 299 horses tested, 44 horses (approximately 14.7%) were found to be heterozygous for the E321G MYH1 variant, which means they had one copy of the wild-type gene and one copy of the mutated gene.
  • The rest, 255 horses (or 85.3%) were homozygous for the wild-type gene, implying they had no mutation.
  • The allele frequency, meaning the frequency of the mutation in the population, was found to be 0.074.
  • Importantly, the prevalence of heterozygosity was significantly higher in horses used for reining compared to those used in other disciplines.

Conclusion and Implications

  • Despite the data being collected from registered Quarter Horses only between 2010 and 2014, and therefore may not fully represent the whole population of Brazilian Quarter Horses, the study conclusion suggests a high prevalence of the MYH1 mutation in the tested population.
  • These findings imply that the disease, MYHM, could become more prevalent in Brazilian Quarter Horses if not controlled.
  • Therefore, the researchers recommend that MYHM should be included in genetic screening practices for Quarter Horses in Brazil, as a prevention measure against an increase in the incidence of this condition.

Cite This Article

APA
de Albuquerque AL, Zanzarini Delfiol DJ, Andrade DGA, Albertino LG, Sonne L, Borges AS, Valberg SJ, Finno CJ, Oliveira-Filho JP. (2021). Prevalence of the E321G MYH1 variant in Brazilian Quarter Horses. Equine Vet J, 54(5), 952-957. https://doi.org/10.1111/evj.13521

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 54
Issue: 5
Pages: 952-957

Researcher Affiliations

de Albuquerque, Ana L
  • Department of Veterinary Clinical Science, School of Veterinary Medicine and Animal Science, São Paulo State University (UNESP), Botucatu, Brazil.
Zanzarini Delfiol, Diego J
  • School of Veterinary Medicine, Universidade Federal de Uberlândia, Uberlândia, Brazil.
Andrade, Danilo G A
  • Department of Veterinary Clinical Science, School of Veterinary Medicine and Animal Science, São Paulo State University (UNESP), Botucatu, Brazil.
Albertino, Lukas G
  • Department of Veterinary Clinical Science, School of Veterinary Medicine and Animal Science, São Paulo State University (UNESP), Botucatu, Brazil.
Sonne, Luciana
  • Sector of Veterinary Pathology, Veterinary Faculty, Federal University of Rio Grande Sul, Porto Alegre, Brazil.
Borges, Alexandre S
  • Department of Veterinary Clinical Science, School of Veterinary Medicine and Animal Science, São Paulo State University (UNESP), Botucatu, Brazil.
Valberg, Stephanie J
  • Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA.
Finno, Carrie J
  • Department of Population Health and Reproduction, School of Veterinary Medicine, University of California-Davis, Davis, California, USA.
Oliveira-Filho, Jose P
  • Department of Veterinary Clinical Science, School of Veterinary Medicine and Animal Science, São Paulo State University (UNESP), Botucatu, Brazil.

MeSH Terms

  • Animals
  • Brazil / epidemiology
  • Cross-Sectional Studies
  • DNA
  • Horse Diseases / epidemiology
  • Horse Diseases / genetics
  • Horses / genetics
  • Prevalence

Grant Funding

  • Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

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This article includes 15 references
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Citations

This article has been cited 3 times.
  1. Durward-Akhurst SA, Valberg SJ. Myosin Heavy Chain Myopathy and Immune-Mediated Muscle Disorders. Vet Clin North Am Equine Pract 2025 Apr;41(1):61-75.
    doi: 10.1016/j.cveq.2024.10.005pubmed: 39880733google scholar: lookup
  2. Valberg SJ, Velez-Irizarry D, Williams ZJ, Pagan JD, Mesquita V, Waldridge B, Maresca-Fichter H. Novel Expression of GLUT3, GLUT6 and GLUT10 in Equine Gluteal Muscle Following Glycogen-Depleting Exercise: Impact of Dietary Starch and Fat. Metabolites 2023 Jun 1;13(6).
    doi: 10.3390/metabo13060718pubmed: 37367876google scholar: lookup
  3. Valberg SJ, Schultz AE, Finno CJ, Bellone RR, Hughes SS. Prevalence of clinical signs and factors impacting expression of myosin heavy chain myopathy in Quarter Horse-related breeds with the MYH1(E321G) mutation. J Vet Intern Med 2022 May;36(3):1152-1159.
    doi: 10.1111/jvim.16417pubmed: 35426178google scholar: lookup
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