OMIA 001199-9838 : Coat colour, extension in Camelus dromedarius
In other species: cattle , dog , horse , red fox , pig , sheep , jaguar , jaguarundi , American black bear , woolly mammoth , domestic cat , rabbit , domestic guinea pig , goat , Arctic fox , rock pocket mouse , oldfield mouse , gray squirrel , lesser earless lizard , little striped whiptail , water buffalo , domestic yak , alpaca , , coyote , reindeer , Geoffroy's cat , Colocolo , ass , Mongolian gerbil , raccoon dog , fallow deer , zebu , lorises , antarctic fur seal
Category: Pigmentation phene
Links to MONDO diseases: No links.
Mendelian trait/disorder: yes
Considered a defect: no
Key variant known: yes
Year key variant first reported: 2018
Cross-species summary: The extension locus encodes the melanocyte-stimulating hormone receptor (MSHR; now known as MC1R). This receptor controls the level of tyrosinase within melanocytes. Tyrosinase is the limiting enzyme involved in synthesis of melanins: high levels of tyrosinase result in the production of eumelanin (dark colour, e.g. brown or black), while low levels result in the production of phaeomelanin (light colour, e.g. red or yellow). When melanocyte-stimulating hormone (MSH) binds to its receptor, the level of tyrosinase is increased, leading to production of eumelanin. The wild-type allele at the extension locus corresponds to a functional MSHR, and hence to dark pigmentation in the presence of MSH. As explained by Schneider et al. (PLoS Genet 10(2): e1004892; 2015), "The most common causes of melanism (black coat) mutations are gain-of-function alterations in MC1R, or loss-of function alterations in ASIP, which encodes Agouti signaling protein, a paracrine signaling molecule that inhibits MC1R signaling". Mutations in MC1R have been associated with white colouring in several species.
Molecular basis: Adopting the comparative candidate gene approach, Almathen et al. (2018) sequenced the MC1R gene in "91 animals from ten Arabian camel populations, that included the four predominant coat color phenotypes observed in the dromedary (light brown, dark brown, black and white)". They identified a missense variant (c.901C>T; p.R301C) associated with white versus non-white: "All nonwhite individuals (black, dark, and light brown, n = 70) were homozygous for the 901C allele, whereas all white dromedaries (Wodh population, n = 21) were either homozygous for the 901T (n = 8) or heterozygous (n = 13) for the 901C/T alleles . . . (P < 0.0001, df = 1)."
Alshanbari et al. (2019) reported that "heterozygosity for . . . [the] missense mutation c.901C > T in MC1R is sufficient for the white coat color suggesting a possible dominant negative effect."
|Symbol||Description||Species||Chr||Location||OMIA gene details page||Other Links|
|MC1R||melanocortin 1 receptor (alpha melanocyte stimulating hormone receptor)||Camelus dromedarius||21||NC_044531.1 (30985552..30990919)||MC1R||Homologene, Ensembl, NCBI gene|
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WARNING! Inclusion of a variant in this table does not automatically mean that it should be used for DNA testing. Anyone contemplating the use of any of these variants for DNA testing should examine critically the relevant evidence (especially in breeds other than the breed in which the variant was first described). If it is decided to proceed, the location and orientation of the variant sequence should be checked very carefully.
Since October 2021, OMIA includes a semiautomated lift-over pipeline to facilitate updates of genomic positions to a recent reference genome position. These changes to genomic positions are not always reflected in the ‘acknowledgements’ or ‘verbal description’ fields in this table.
|OMIA Variant ID||Breed(s)||Variant Phenotype||Gene||Allele||Type of Variant||Source of Genetic Variant||Reference Sequence||Chr.||g. or m.||c. or n.||p.||Verbal Description||EVA ID||Inferred EVA rsID||Year Published||PubMed ID(s)||Acknowledgements|
|1009||White coat colour||MC1R||missense||Naturally occurring variant||c.901C>T||p.(R301C)||KU179867; c.901C>T; p.R301C||2018||29893870|
Note: the references are listed in reverse chronological order (from the most recent year to the earliest year), and alphabetically by first author within a year.
|2019||Alshanbari, F., Castaneda, C., Juras, R., Hillhouse, A., Mendoza, M.N., Gutiérrez, G.A., Ponce de León, F.A., Raudsepp, T. :|
|Comparative FISH-mapping of MC1R, ASIP, and TYRP1 in New and Old World camelids and association analysis with coat color phenotypes in the dromedary (Camelus dromedarius). Front Genet 10:340, 2019. Pubmed reference: 31040864. DOI: 10.3389/fgene.2019.00340.|
|2018||Almathen, F., Elbir, H., Bahbahani, H., Mwacharo, J., Hanotte, O., Almathen, F., Elbir, H., Bahbahani, H., Mwacharo, J., Hanotte, O. :|
|Polymorphisms in MC1R and ASIP genes are associated with coat color variation in the Arabian camel. J Hered 109:700-706, 2018. Pubmed reference: 29893870. DOI: 10.1093/jhered/esy024.|
- Created by Frank Nicholas on 28 Aug 2018
- Changed by Frank Nicholas on 05 Jun 2019