Dominant White 31 (W31)
Gene or Region: KIT
Reference Variant: No insertion (n)
Mutant Variant: Insertion
Affected Breeds: Quarter Horse
Research Confidence: High - Mutations in KIT have been well-documented to cause white spotting in both the horse and other species
Explanation of Results: W31/W31 = homozygous for Dominant White 31, white markings expressed W31/n = heterozygous for Dominant White 31, white markings expressed n/n = no variant detected
General Description for Dominant 31
Dominant White 31 (W31) is found in Quarter Horses and may result in white markings on the face (bald face), legs, and belly spots.
W31 Founder: Cookin Merada
W31 Phenotype: White markings on face (bald face), legs, belly spots
Gene Information
KIT is a tyrosine kinase receptor that is vital for normal development. Mutations in other species have led to white spotting, anemia, sterility, and certain types of tumors. However, no negative health effects associated with dominant white have ever been documented in the horse. The various W alleles encompass a variety of mutations, all resulting in changes to the encoded protein.
References
Haase B et al., “Allelic heterogeneity at the equine KIT locus in dominant white (W) horses.” (2007) PLoS Genet. 3: e195.
Haase B et al., “Seven novel KIT mutations in horses with white coat colour phenotypes.” (2009) Anim Genet. 40: 623-9.
Holl H et al., “De novo mutation of KIT discovered as a result of a non-hereditary white coat colour pattern.” (2010) Anim Genet. 41: 196-8.
Haase B et al., “Five novel KIT mutations in horses with white coat colour phenotypes.” (2011) Anim Genet. 42: 337-9.
Hauswirth R et al., “Novel variants in the KIT and PAX3 genes in horses with white-spotted coat colour phenotypes.” (2013) Anim Genet. 44: 763-5.
Holl H et al., “A novel splice mutation within equine KIT and the W15 allele in the homozygous state lead to all white coat color phenotypes.” (2017) Anim Genet. DOI: 10.1111/age.12554
Durig N et al., “Whole genome sequencing reveals a novel deletion variant in the KIT gene in horses with white spotted coat colour phenotypes.” (2017) Anim Genet. In press.
More Horse Color Genetics
Dun / Non-Dun
Dun (D) is a dilution that affects both black and red pigment types. Two non-dun (nd1 & nd2) variants have been discovered, with nd1 being associated with primitive markings (such as a characteristic dorsal stripe) in non-dilute horses, and nd2 showing neither dilution nor primitive markings.