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Home / Equine Research Bank / BMC Genet / Equine Multiple Congenital Ocular Anomalies maps to a 4.9 me...
BMC genetics2008; 9; 88; doi: 10.1186/1471-2156-9-88

Equine Multiple Congenital Ocular Anomalies maps to a 4.9 megabase interval on horse chromosome 6.

Abstract: Equine Multiple Congenital Ocular Anomalies (MCOA) syndrome consists of a diverse set of abnormalities predominantly localized to the frontal part of the eye. The disease is in agreement with a codominant mode of inheritance in our horse material. Animals presumed to be heterozygous for the mutant allele have cysts originating from the temporal ciliary body, peripheral retina and/or iris. In contrast, animals predicted to be homozygous for the disease-causing allele possess a wide range of multiple abnormalities, including iridociliary and/or peripheral retinal cysts, iridocorneal angle abnormalities, cornea globosa, iris hypoplasia and congenital cataracts. MCOA is most common in the Rocky Mountain horse breed where it occurs at a high frequency among Silver colored horses. The Silver coat color is associated with mutations in PMEL17 that resides on ECA6q23. To map the MCOA locus we analyzed 11 genetic markers on ECA6q and herein describe a chromosome interval for the MCOA locus. Results: We performed linkage analysis within 17 paternal half-sib families of the Rocky Mountain horse breed. More than half of the 131 offspring had the Cyst phenotype and about one third had MCOA. Segregation data were obtained by genotyping 10 microsatellite markers most of which are positioned on ECA6q22-23, as well as the missense mutation for the Silver phenotype in PMEL17. Significant linkage was found between the MCOA locus and eight of the genetic markers, where marker UPP5 (Theta = 0, z = 12.3), PMEL17ex11 (Theta = 0, z = 19.0) and UPP6 (Theta = 0, z = 17.5) showed complete linkage with the MCOA locus. DNA sequencing of PMEL17 in affected and healthy control individuals did not reveal any additional mutations than the two mutations associated with the Silver coat color. Conclusions: The MCOA locus can with high confidence be positioned within a 4.9 megabase (Mb) interval on ECA6q. The genotype data on UPP5, PMEL17ex11 and UPP6 strongly support the hypothesis that horses with the Cyst phenotype are heterozygous for the mutant allele and that horses with the MCOA phenotype are homozygous for the mutant allele.
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Publication Date: 2008-12-19 PubMed ID: 19099555PubMed Central: PMC2653074DOI: 10.1186/1471-2156-9-88Google 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.

The research investigates the genetic origins of Equine Multiple Congenital Ocular Anomalies (MCOA) in horses, locating the responsible gene within a 4.9 megabase interval on horse chromosome 6.

Background on MCOA

  • MCOA is a syndrome manifested through a range of eye abnormalities, particularly located in the frontal part of the horse’s eye.
  • This genetic disorder is primarily observed in the Rocky Mountain horse breed, especially in those with Silver coat color.
  • The different repercussions of the disorder depend on whether the horse is heterozygous or homozygous for the genetic mutation causing the syndrome.
  • Heterozygous animals typically have cysts originating from several parts of the eye whereas homozygous animals may experience more severe abnormalities such as cornea globosa, iris hypoplasia, and congenital cataracts.

Investigation of Genetic Markers

  • The study analyzed 11 genetic markers on ECA6q, the horse chromosome region where PMEL17, the gene associated with the Silver coat color, resides.
  • A total of 17 paternal half-sib families of the Rocky Mountain horse breed were subjected to a linkage analysis.
  • Of the 131 offspring horses, over half showed the cyst phenotype associated with the mutant allele, while about one third were diagnosed with MCOA.
  • The diagnosis was confirmed by genotyping 10 microsatellite markers positioned mainly on ECA6q22-23, as well as the missense mutation responsible for the Silver phenotype in PMEL17.

Linkage Analysis and Conclusions

  • The MCOA locus showed significant linkage with eight of the genetic markers, but complete linkage was found with three specific markers: UPP5, PMEL17ex11, and UPP6.
  • No other mutations were detected in PMEL17, apart from the two already associated with the Silver coat color.
  • Based on these results, researchers concluded that the MCOA locus is very likely located within a 4.9 megabase (Mb) interval on ECA6q.
  • This data provides strong evidence that horses with the Cyst phenotype are heterozygous for the mutant allele and horses diagnosed with MCOA are homozygous for the mutant allele.

Cite This Article

APA
Andersson LS, Juras R, Ramsey DT, Eason-Butler J, Ewart S, Cothran G, Lindgren G. (2008). Equine Multiple Congenital Ocular Anomalies maps to a 4.9 megabase interval on horse chromosome 6. BMC Genet, 9, 88. https://doi.org/10.1186/1471-2156-9-88

Publication

BMC genetics
ISSN: 1471-2156
NlmUniqueID: 100966978
Country: England
Language: English
Volume: 9
Pages: 88

Researcher Affiliations

Andersson, Lisa S
  • Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden. Lisa.Andersson@hgen.slu.se
Juras, Rytis
    Ramsey, David T
      Eason-Butler, Jessica
        Ewart, Susan
          Cothran, Gus
            Lindgren, Gabriella

              MeSH Terms

              • Alleles
              • Animals
              • Chromosome Mapping
              • Chromosomes, Mammalian / genetics
              • Eye Abnormalities / genetics
              • Eye Abnormalities / veterinary
              • Genetic Markers
              • Genotype
              • Horses / genetics
              • Microsatellite Repeats
              • Pedigree
              • Phenotype
              • Sequence Analysis, DNA

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