Dominant White 19 (W19)
Gene or Region: KIT
Reference Variant: T (N)
Mutant Variant: C (W19)
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: W19/W19 = homozygous for Dominant White 19, Large white markings to completely white; blue eyes likely *documented cases indicate that this combination may include congenital birth defects including slowed growth, immunodeficiency, infertility and may be in many cases lethal recessive W19/n = heterozygous for Dominant White 19, white markings expressed n/n = no variant detected
General Description for Dominant White 19
Dominant White 19 (W19) is found in Arabian horses and may result in a bald face with extended white on legs and belly spots.
W19 Founder: Not stated
W19 Phenotype: Bald face, extended white on 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.