Splashed White 6 (SW6)
Gene or Region: MITF
Reference Variant: -
Mutant Variant: chr16:21551060_21559770del
Affected Breeds: Quarter Horse & Paint Horse
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: SW6/SW6 = homozygous for Splashed White 6, likely white markings expressed, UNOBSERVED SW6/n = heterozygous for Splashed White 6, white markings expressed n/n = no variant detected
General Description of Splashed White 6
Splashed White 6 (SW6) is found in Quarter and Paint Horses and may result in a bald white face, blue eyes, white socks, body markings, and potentially deafness.
Phenotype: heterozygous expressed as bald/white face, two blue eyes, often white socks and body markings, high incidence of deafness; homozygous not described
Gene Information
MITF is a transcription factor that serves to activate several key genes involved in the development of pigmentation.
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
Magdesian KG, Tanaka J, Bellone RR. A De Novo MITF Deletion Explains a Novel Splashed White Phenotype in an American Paint Horse. J Hered. 2020 May 20;111(3):287-293. doi: 10.1093/jhered/esaa009. PMID: 32242630; PMCID: PMC7238438.