Splashed White 1 (SW1)
Gene or Region: MITF
Reference Variant: T (N)
Mutant Variant: ATAATAACCTA (SW1)
Affected Breeds: Many
Research Confidence: High - Mutations in MITF and PAX3 have been well-documented to cause white spotting in both the horse and other species, even humans!
Explanation of Results: SW1/SW1 = homozygous for Splashed White 1, white markings expressed SW1/n = heterozygous for Splashed White 1, white markings expressed n/n = no variant detected
General Description
Splashed White 1 (SW1) is found in many breeds and presents as normal markings in a heterozygous horse and typical splashed white markings in a homozygous horse.
SW1 Discovered In: Unknown
SW1 Phenotype: Normal markings in heterozygous horses; typical Splashed White markings in homozygous horses
Gene Information
MITF is a transcription factor that serves to activate several key genes involved in the development of pigmentation. Mutations in both the horse and in other species have led to white spotting, deafness, and sterility.
References
McFadden, A., Martin, K., Foster, G., Vierra, M., Lundquist, E., Everts, R., Martin, E., Volz, E., McLoone, K., Brooks, S., Lafayette, C. (2023) Two Novel Variants in MITF and PAX3 Associated with Splashed White Phenotypes in Horses. Journal of Equine Veterinary Science, July 2023.
Patterson, et. al., "Non-frameshift deletion on MITF is associated with a novel splashed white spotting pattern in horses (Equus caballus)" (2022) Anim Genet. 2022 Jun 7. doi: 10.1111/age.13225
Henkel, et al., "Whole-genome sequencing reveals a large deletion in the MITF gene in horses with white spotted coat colour and increased risk of deafness" (2019) Anim Genet. 50: 172-4.
Hauswirth R et al., “Mutations in MITF and PAX3 cause "splashed white" and other white spotting phenotypes in horses.” (2012) PLoS Genet. 8: e1002653.
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.
Magdesian, KG et al., "A de novo MITF deletion explains a novel splashed white phenotype in an American Paint Horse." (2020) The American Genetic Association