Dominant White 17 (W17)
Gene or Region: KIT
Reference Variant: T,A (N)
Mutant Variant: A,G (W4)
Affected Breeds: Japanese Draft
Research Confidence: High - Mutations in KIT have been well-documented to cause white spotting in both the horse and other species
Explanation of Results: W17/W17 = homozygous for Dominant White 17, white markings expressed W17/n = heterozygous for Dominant White 17, white markings expressed n/n = no variant detected
General Description for Dominant White 17
Dominant White 17 (W17) is found in Japanese Draft horses and may result in a completely white coat with one blue eye.
W17 Founder: Not stated (born 2010)
W17 Phenotype: Completely white with one blue eye
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.