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Home / Equine Research Bank / Mamm Genome / Targeted analysis of four breeds narrows equine Multiple Con...
Mammalian genome : official journal of the International Mammalian Genome Society2011; 22(5-6); 353-360; doi: 10.1007/s00335-011-9325-7

Targeted analysis of four breeds narrows equine Multiple Congenital Ocular Anomalies locus to 208 kilobases.

Abstract: The syndrome Multiple Congenital Ocular Anomalies (MCOA) is the collective name ascribed to heritable congenital eye defects in horses. Individuals homozygous for the disease allele (MCOA phenotype) have a wide range of eye anomalies, while heterozygous horses (Cyst phenotype) predominantly have cysts that originate from the temporal ciliary body, iris, and/or peripheral retina. MCOA syndrome is highly prevalent in the Rocky Mountain Horse but the disease is not limited to this breed. Affected horses most often have a Silver coat color; however, a pleiotropic link between these phenotypes is yet to be proven. Locating and possibly isolating these traits would provide invaluable knowledge to scientists and breeders. This would favor maintenance of a desirable coat color while addressing the health concerns of the affected breeds, and would also provide insight into the genetic basis of the disease. Identical-by-descent mapping was used to narrow the previous 4.6-Mb region to a 264-kb interval for the MCOA locus. One haplotype common to four breeds showed complete association to the disease (Cyst phenotype, n = 246; MCOA phenotype, n = 83). Candidate genes from the interval, SMARCC2 and IKZF4, were screened for polymorphisms and genotyped, and segregation analysis allowed the MCOA syndrome region to be shortened to 208 kb. This interval also harbors PMEL17, the gene causative for Silver coat color. However, by shortening the MCOA locus by a factor of 20, 176 other genes have been unlinked from the disease and only 15 genes remain.
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Publication Date: 2011-04-05 PubMed ID: 21465164PubMed Central: PMC3098992DOI: 10.1007/s00335-011-9325-7Google Scholar: Lookup
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  • Comparative Study
  • 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.

This research focuses on the heritable eye disorder in horses known as Multiple Congenital Ocular Anomalies (MCOA). Using genetic mapping, the researchers have narrowed down the locations on the genetic code where this disorder might originate. This information can help breeders maintain desirable traits in horses while avoiding the health issues associated with the MCOA disorder.

Understanding MCOA in Horses

  • MCOA, or Multiple Congenital Ocular Anomalies, is a genetically inherited eye disorder in horses with symptoms including a wide range of eye anomalies. Homozygous horses (those with two identical alleles for the disease) exhibit this syndrome, while heterozygous horses (those with differing alleles) tend to show only the cyst-forming attributes of the disease.
  • This disorder is known to occur most frequently in the Rocky Mountain Horse breed, but it’s not exclusive to them. Horses carrying this disease often exhibit a Silver coat color, though a definitive link between the coat color and the disease hasn’t been found.

Genetic Mapping of MCOA

  • The researchers utilized a technique called identical-by-descent mapping to find the location of the MCOA genetic component on a horse’s chromosome. This allowed them to narrow down the previously known 4.6-Mb region to a 264-kb segment on the chromosome where the MCOA gene can be found.
  • This smaller section of genes isn’t just found in Rocky Mountain Horses, but also in three other breeds, helping to confirm its link to the disease.

Narrowing Down the MCOA Locus

  • The researchers further investigated and screened the genes found within the 264-kb region and found two specific candidate genes: SMARCC2 and IKZF4. Genotyping and segregation analysis of these genes allowed them to shrink the suspected cause for the MCOA syndrome down to an even smaller 208-kb region on the horse’s chromosome.
  • The researchers note that this narrowed-down region also contains PMEL17, the gene responsible for the Silver coat color in horses. This made it a viable candidate for further scrutiny given the commonly observed link between the MCOA syndrome and Silver coat color in affected horses.
  • By successfully narrowing down the suspected area for MCOA syndrome within the horse’s chromosome, the researchers were able to disassociate 176 other genes from the disease. Now only 15 genes, including PMEL17, remain linked to the disease. This offers a more specialized area for future research in better understanding and dealing with MCOA syndrome in horses.

Cite This Article

APA
Andersson LS, Lyberg K, Cothran G, Ramsey DT, Juras R, Mikko S, Ekesten B, Ewart S, Lindgren G. (2011). Targeted analysis of four breeds narrows equine Multiple Congenital Ocular Anomalies locus to 208 kilobases. Mamm Genome, 22(5-6), 353-360. https://doi.org/10.1007/s00335-011-9325-7

Publication

Mammalian genome : official journal of the International Mammalian Genome Society
ISSN: 1432-1777
NlmUniqueID: 9100916
Country: United States
Language: English
Volume: 22
Issue: 5-6
Pages: 353-360

Researcher Affiliations

Andersson, Lisa S
  • Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Undervisningsplan 4A, PO Box 7023, 750 07 Uppsala, Sweden.
Lyberg, Katarina
    Cothran, Gus
      Ramsey, David T
        Juras, Rytis
          Mikko, Sofia
            Ekesten, Björn
              Ewart, Susan
                Lindgren, Gabriella

                  MeSH Terms

                  • Animals
                  • Base Sequence
                  • Chromosome Mapping
                  • Chromosomes, Mammalian / genetics
                  • Eye Abnormalities / genetics
                  • Eye Abnormalities / veterinary
                  • Genetic Loci / genetics
                  • Genotype
                  • Haplotypes / genetics
                  • Horse Diseases / genetics
                  • Horses
                  • Microsatellite Repeats / genetics
                  • Molecular Sequence Data
                  • Polymorphism, Single Nucleotide / genetics
                  • Sequence Analysis, DNA
                  • Species Specificity
                  • Syndrome
                  • Transcription Factors / genetics

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                  Citations

                  This article has been cited 3 times.
                  1. Le L, Sirés-Campos J, Raposo G, Delevoye C, Marks MS. Melanosome Biogenesis in the Pigmentation of Mammalian Skin. Integr Comp Biol 2021 Oct 14;61(4):1517-1545.
                    doi: 10.1093/icb/icab078pubmed: 34021746google scholar: lookup
                  2. Reissmann M, Musa L, Zakizadeh S, Ludwig A. Distribution of coat-color-associated alleles in the domestic horse population and Przewalski's horse. J Appl Genet 2016 Nov;57(4):519-525.
                    doi: 10.1007/s13353-016-0352-7pubmed: 27194311google scholar: lookup
                  3. Andersson LS, Wilbe M, Viluma A, Cothran G, Ekesten B, Ewart S, Lindgren G. Equine multiple congenital ocular anomalies and silver coat colour result from the pleiotropic effects of mutant PMEL. PLoS One 2013;8(9):e75639.
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