Coat Color Genotypes and Risk and Severity of Melanoma in Gray Quarter Horses
Article first published online: 22 JUL 2013
Copyright © 2013 by the American College of Veterinary Internal Medicine
Journal of Veterinary Internal Medicine
Volume 27, Issue 5, pages 1201–1208, September/October 2013
How to Cite
Teixeira, R.B.C., Rendahl, A.K., Anderson, S.M., Mickelson, J.R., Sigler, D., Buchanan, B.R., Coleman, R.J. and McCue, M.E. (2013), Coat Color Genotypes and Risk and Severity of Melanoma in Gray Quarter Horses. Journal of Veterinary Internal Medicine, 27: 1201–1208. doi: 10.1111/jvim.12133
- Issue published online: 13 SEP 2013
- Article first published online: 22 JUL 2013
- Manuscript Accepted: 22 MAY 2013
- Manuscript Revised: 8 APR 2013
- Manuscript Received: 10 OCT 2012
- Morris Animal Foundation. Grant Number: D10-EQ028
- University of Minnesota Equine Center
- NIH-NIAMS. Grant Number: 1K08AR055713-01A2
- ASIP ;
- MC1R ;
Both graying and melanoma formation in horses have recently been linked to a duplication in the STX17 gene. This duplication, as well as a mutation in the ASIP gene that increases MC1R pathway signaling, affects melanoma risk and severity in gray horses.
To determine if melanoma susceptibility in gray Quarter Horses (QH) is lower than gray horses from other breeds because of decreased MC1R signaling resulting from a high incidence of the MC1R chestnut coat color allele in the QH population.
A total of 335 gray QH with and without dermal melanomas.
Blood or hair root samples were collected from all horses for DNA extraction and genotyping for STX17, ASIP, and MC1R genotypes. Age, sex, and external melanoma presence and grade were recorded. The effect of age and genotype on melanoma presence and severity was evaluated by candidate gene association.
Melanoma prevalence (16%) and grade (0.35) in this QH cohort was lower than that reported in other breeds. Age was significantly associated with melanoma prevalence (P = 5.28 × 10−11) and severity (P = 2.2 × 10−13). No significant effect of MC1R genotype on melanoma prevalence or severity was identified. An effect of ASIP genotype on melanoma risk was not detected. Low STX17 homozygosity precluded evaluation of the gray allele effect.
Conclusion and clinical importance
Melanoma prevalence and severity is lower in this population of gray QH than what is reported in other breeds. This could be because of the infrequent STX17 homozygosity, a mitigating effect of the MC1R mutation on ASIP potentiation of melanoma, other genes in the MC1R signaling pathway, or differences in breed genetic background.