OMIA 001884-9796 : Coat colour, white markings in Equus caballus

Mendelian trait/disorder: no

Mode of inheritance: Multifactorial

Considered a defect: no

Key variant known: no

Inheritance: Woolf (1989) and (1990) provided evidence supporting multifactorial inheritance of white markings. Rieder et al. (2008) reported "Heritabilities and genetic correlations for [white head and anterior and posterior leg markings] were high (h(2) > 0.5). A strong positive correlation was found between the chestnut allele at the melanocortin-1-receptor gene locus and the extent of white markings. Segregation analysis revealed that our data fit best to a model including a polygenic effect and a biallelic locus with a dominant-recessive mode of inheritance. The recessive allele was found to be the white trait-increasing allele."

Mapping: Rieder et al. (2008) reported "Multilocus linkage disequilibrium analysis allowed the mapping of the putative major locus to a chromosomal region on ECA3q harboring the KIT gene."

A GWAS conducted by Haase et al. (2013) on 1,077 Franches-Montagnes horses from Switzerland, each phenotyped using a standard scale for the extent of white markings on head, fore limbs and hind limbs, and each genotyped with the Illumina 50K equine SNP chip, identified seven QTL which together accounted for 54% of the genetic variance in total white markings. The three QTL with largest effect corresponded to the know coat-colour genes MC1R, KIT and MITF, the latter two alone contributing 26% of the genetic variance.

Molecular basis: By examining phylogenetic relationships of MITF and KIT haplotypes, Haase et al. (2013) concluded "that KIT and MITF act in an additive manner and that accumulating mutations at these loci progressively increase the extent of white markings".

Breed: Franches-Montagnes.


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.
2013 Haase, B., Signer-Hasler, H., Binns, M.M., Obexer-Ruff, G., Hauswirth, R., Bellone, R.R., Burger, D., Rieder, S., Wade, C.M., Leeb, T. :
Accumulating Mutations in Series of Haplotypes at the KIT and MITF Loci Are Major Determinants of White Markings in Franches-Montagnes Horses. PLoS One 8:e75071, 2013. Pubmed reference: 24098679. DOI: 10.1371/journal.pone.0075071.
2008 Rieder, S., Hagger, C., Obexer-Ruff, G., Leeb, T., Poncet, PA. :
Genetic analysis of white facial and leg markings in the Swiss Franches-Montagnes Horse Breed. J Hered 99:130-6, 2008. Pubmed reference: 18296388. DOI: 10.1093/jhered/esm115.
1997 Woolf, C.M. :
Directional and anteroposterior asymmetry of common white markings in the legs of the arabian horse - response to selection Genetica 101:199-208, 1997. Pubmed reference: 9692229.
1995 Woolf, C.M. :
Influence of stochastic events on the phenotypic variation of common white leg markings in the Arabian horse: implications for various genetic disorders in humans. J Hered 86:129-35, 1995. Pubmed reference: 7751597.
1993 Woolf, C.M. :
Does Homozygosity Contribute to the Asymmetry of Common White Leg Markings in the Arabian Horse? Genetica 89:25-33, 1993.
1992 Woolf, C.M. :
Common White Facial Markings in Arabian Horses That Are Homozygous and Heterozygous for Alleles at the A-Loci and E- Loci Journal of Heredity 83:73-77, 1992. Pubmed reference: 1552160.
1991 Woolf, C.M. :
Common White Facial Markings in Bay and Chestnut Arabian Horses and Their Hybrids Journal of Heredity 82:167-169, 1991. Pubmed reference: 2013690.
1990 Woolf, C.M. :
Multifactorial Inheritance of Common White Markings in the Arabian Horse Journal of Heredity 81:250-256, 1990. Pubmed reference: 2273238.
1989 Woolf, C.M. :
Multifactorial Inheritance of White Facial Markings in the Arabian Horse Journal of Heredity 80:173-178, 1989. Pubmed reference: 2732451.

Edit History

  • Created by Frank Nicholas on 13 Oct 2013
  • Changed by Frank Nicholas on 13 Oct 2013