• About This Guide
  
• How This Guide is Being Developed
  
• Philosophy of this guide
  
• Using this Guide
  
• Thinking Scientifically
  
• About the Author
  
• Documented Genes
  
• What is a documented gene?
  
• Black/Red (MC1R)
  
• Bay (ASIP)
  
• Cream/Pearl (SLC45A2)
  
• Dun (TBX3)
  
• Gray (STX17)
  
• Silver (PMEL17)
  
• Champagne (SLC36A1)
  
• Roan/Tobiano/Sabino/White Spotting (KIT)
  
• Splash White (MITF/PAX3)
  
• Leopard Complex (TRPM1/ECA3P)
  
• Frame (EDNRB)
  
• Tiger Eye (SLC24A5)
  
• Height Regulation (HMGA2/LCORL)
  
• Mushroom (MFSD12)
  
• Hypothetical Genes
  
• What is a hypothetical gene?
  
• Borrowed Genes
  
• Glossaries
  
• Glossary of Colors
  
• Glossary of Terms
  

Splash White (MITF/PAX3)

• Last updated: 2026-02-11

  Common Names: Splash, or Splash White: 1/2/3/4/5/6/7/8/9/10 and M

  Scientific Name: Microphthalmia-associated transcription factor (MITF) and Paired box 3 (PAX3)

  Equine Chromosome: MITF on 16, PAX3 on 6

  General Overview:

  There are currently 11 documented variations of splash. Splash 1,3,5,6,7,8,9 and M are located on MITF. Splash 2, 4 and 10 are located on PAX3. [1,2,3,4,5,6,7,8] The MITF and PAX3 variants are similar enough in behavior that they are both treated as a single phenotype called splash white.

  
  

  Splash mutations result in face markings that range from blazes to fully bald faces. They often have one or more blue eyes. Splash white horses normally have high white leg markings on 3 or more legs. Minimal expressions of splash may be indistinguishable from other common markings. When homozygous, splash white horses have extensive white markings, normally covering the entirety of the legs and face, often including the belly, and sometimes resulting in completely white horses.

  
  

  Splash white markings are frequently linked to deafness. Larger white markings, particularly those that cover the ears are the most likely to result in deaf individuals. [1] 

  
  

  Currently only splash white 1, 2, 3, and M are found in HorseGeneticsGame.com.

• Specific Alleles:
  Splash 1 is located on MITF and has been found in a wide variety of breeds including stock horses, warmbloods, icelandics, miniatures and more.

  
  

  Splash 2 is located on PAX3.[1] The mutation was originally thought to be isolated to Paints and Quarter horses due to a lab error.[9] The gene has since been found in other breeds as well. This mutation was originally thought to be homozygous lethal, but is now known to be at least partially viable. Homozygous individuals are normally deaf and may have deformities. [3,10] My personal conjecture is that this mutation is probably sometimes embryonic lethal and sometimes not depending on other developmental factors. Splash 2 is currently homozygous lethal in HorseGeneticsGame.com

  
  

  Splash M is located on MITF. It was found in a single Franches-Montagnes horse who has since been gelded. He appeared to have a de novo mutation, with neither of his parents sharing the same allele. [1] Since there are no other splash M horses and never will be another this form was not given a number in the sequence. It is instead known as splash M or macchiato. In HorseGeneticsGame.com splash M horses have a diluted body color with large leg and face markings with laced edges. They can potentially have blue eyes. 

  
  

  Splash 3 horses descend from the AQHA stallion TD Kid. It results in large white markings when heterozygous and is probably homozygous lethal. [1]

  
  

  Splash 4 is a rare PAX3 mutation found in the Iza Last Jet line of appaloosa horses. It causes large blazes and partially blue eyes. It is potentially homozygous lethal. [2]

  
  

  Splash 5, 6 and 7 are mutations of MITF found in quarter horses and paint horses. They produce large amounts of leg markings, face white, blue eyes and frequent deaf individuals when heterozygous. All are presumed homozygous lethal with themselves and with other loud MITF mutations. [4,5,6]

  
  

  Splash 8 is a mutation of MITF found in a single family of thoroughbreds. This variant produces moderate bald faces, leg white and blue eyes. Some are known to be deaf. Its lethality when homozygous is unknown. [7]

  
  

  Splash 9 is an MITF mutation found in Pura Raza Española horses. It results in moderate bald faces, leg white and blue eyes. Deafness has not been found in splash 9 horses so far. Its lethality when homozygous is unknown.[8]

  
  

  Splash 10 is a PAX3 mutation found in Pura Raza Española horses.It results in moderate bald faces, leg white and blue eyes. Deafness has not been found in splash 10 horses so far. Its lethality when homozygous is unknown.[8]

  
  

• Lethality:

  What follows is what I have come to understand from reading a large number of papers on splash white and its mechanics. I do not know of any study that lays this information out directly.

  
  

  Mutations become lethal when a critical to life developmental process no longer works. MITF and PAX3 both perform important actions in the body. Like with a car, a lot of things can break and the car can keep running. At some point though, just too many systems have failed and the engine will no longer start. There are no clean cut rules about splash white lethality. Less white means less parts of the process are broken. More white means more of it is broken and it’s more likely that the combination is lethal.

  
  

  The more white produced by an allele of splash the more likely it is to be lethal when homozygous or when combined with other splash mutations. Two loud splash alleles are more likely to be lethal than two more minimal splash alleles. As splash has incomplete dominance a specific combination may be lethal in some cases but not others. Combining an MITF mutation with a PAX3 mutation is less lethal than combining two MITF or two PAX3 mutations.

• Citations:

  1. Hauswirth R, Haase B, Blatter M, Brooks SA, Burger D, Drögemüller C, Gerber V, Henke D, Janda J, Jude R, Magdesian KG, Matthews JM, Poncet PA, Svansson V, Tozaki T, Wilkinson-White L, Penedo MC, Rieder S, Leeb T. Mutations in MITF and PAX3 cause "splashed white" and other white spotting phenotypes in horses. PLoS Genet. 2012;8(4):e1002653. doi: 10.1371/journal.pgen.1002653. Epub 2012 Apr 12. Erratum in: PLoS Genet. 2019 Aug 2;15(8):e1008321. doi: 10.1371/journal.pgen.1008321. PMID: 22511888; PMCID: PMC3325211. https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1002653 
  2. Hauswirth R, Jude R, Haase B, Bellone RR, Archer S, Holl H, Brooks SA, Tozaki T, Penedo MC, Rieder S, Leeb T. Novel variants in the KIT and PAX3 genes in horses with white-spotted coat colour phenotypes. Anim Genet. 2013 Dec;44(6):763-5. doi: 10.1111/age.12057. Epub 2013 May 9. PMID: 23659293.https://www.researchgate.net/publication/236673503_Novel_variants_in_the_KIT_and_PAX3_genes_in_horses_with_white-spotted_coat_colour_phenotypes 
  3. Avila, F., Hughes, S.S., Magdesian, K.G., Penedo, M.C.T, and Bellone, R.R. 2022. Breed Distribution and Allele Frequencies of Base Coat Color, Dilution, and White Patterning Variants across 28 Horse Breeds. Genes 13(9):1641. https://www.researchgate.net/publication/363564721_Breed_Distribution_and_A
  4. Henkel J, Lafayette C, Brooks SA, Martin K, Patterson-Rosa L, Cook D, Jagannathan V, Leeb T. Whole-genome sequencing reveals a large deletion in the MITF gene in horses with white spotted coat colour and increased risk of deafness. Anim Genet. 2019 Apr;50(2):172-174. doi: 10.1111/age.12762. Epub 2019 Jan 15. PMID: 30644113. https://www.semanticscholar.org/paper/Whole-genome-sequencing-reveals-a-large-deletion-in-Henkel-Lafayette/092bc279d1aa976992fbc3c708a675efc5997533 
  5. 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. https://pubmed.ncbi.nlm.nih.gov/32242630/ 
  6. Patterson Rosa, L., Martin, K., Vierra, M., Foster, G., Brooks, S. A., & Lafayette, C. (2022). Non-frameshift deletion on MITF is associated with a novel splashed white spotting pattern in horses (Equus caballus). Animal Genetics, 53(4), 538–540. doi: 10.1111/age.13225
  7.  Bellone RR, Tanaka J, Esdaile E, Sutton RB, Payette F, Leduc L, Till BJ, Abdel-Ghaffar AK, Hammond M, Magdesian KG. A de novo 2.3 kb structural variant in MITF explains a novel splashed white phenotype in a Thoroughbred family. Anim Genet. 2023 Dec;54(6):752-762. doi: 10.1111/age.13352. Epub 2023 Sep 12. PMID: 37697831. https://onlinelibrary.wiley.com/doi/full/10.1111/age.13352 
  8. McFadden A, Martin K, Foster G, Vierra M, Lundquist EW, Everts RE, Martin E, Volz E, McLoone K, Brooks SA, Lafayette C. Two Novel Variants in MITF and PAX3 Associated With Splashed White Phenotypes in Horses. J Equine Vet Sci. 2023 Sep;128:104875. doi: 10.1016/j.jevs.2023.104875. Epub 2023 Jul 3. PMID: 37406837. https://www.researchgate.net/publication/372087978_Two_Novel_Variants_in_MITF_and_PAX3_Associated_with_Splashed_White_Phenotypes_in_Horses 
  9. Hauswirth R, Haase B, Blatter M, Brooks SA, Burger D, Drögemüller C, Gerber V, Henke D, Janda J, Jude R, Magdesian KG, Matthews JM, Poncet PA, Svansson V, Tozaki T, Wilkinson-White L, Penedo MCT, Rieder S, Leeb T. Correction: Mutations in MITF and PAX3 Cause "Splashed White" and Other White Spotting Phenotypes in Horses. PLoS Genet. 2019 Aug 2;15(8):e1008321. doi: 10.1371/journal.pgen.1008321. Erratum for: PLoS Genet. 2012;8(4):e1002653. doi: 10.1371/journal.pgen.1002653. PMID: 31374075; PMCID: PMC6677290.https://pmc.ncbi.nlm.nih.gov/articles/PMC6677290/ 
  10. “Splashed Whites and Lethals: What Is Happening on Facebook? | Etalon Equine Genetics.” Etalondx.com, 2024, etalondx.com/news-media/homozygous-sw2-raises-concerns/. Accessed 11 Feb. 2026.

• Examples:

  A range of splash expressions