Dominant White 23 (W23)
Gene or Region: KIT
Reference Variant: C (N)
Mutant Variant: G (W23)
Affected Breeds: Arabian
Research Confidence: High - Mutations in KIT have been well-documented to cause white spotting in both the horse and other species
Explanation of Results: W23/W23 = homozygous for Dominant White 23, white markings expressed W23/n = heterozygous for Dominant White 23, white markings expressed n/n = no variant detected
General Description for Dominant White 23
Dominant White 23 (W23) is found in Arabian horses and may result in a mostly white coat color. this coat color is considered extinct.
W23 Founder: Boomori Simply Stunning
W23 Phenotype: Mostly white
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
Silver
Silver (Z) is a dilution that only affects black pigmentation. Horses often have a lighter mane and tail. Silver foals are born with striped hooves and white eyelashes. Bay silver horses retain the normal reddish body color combined with diluted legs, which is often misidentified as a chestnut.