HorseGeneticsGame User Guide

Roan/Tobiano/Sabino/White Spotting (KIT)

Last updated: 2026-01-23

Common Names: KIT, Tobiano, Roan, White Spotting, Sabino, Dominant White

Scientific Name: tyrosine-protein kinase KIT (KIT)

Equine Chromosome: 3

General Overview:

Of all the genes associated with color in horses none is more dynamic and with more known alleles than KIT. A staggering 40+ forms have been discovered and it is expected many more are still to be found.

Kit mutations cause standard looking white markings on the feet and face in more minimal forms, and large lacey broken markings that stretch up into the body in louder forms. Some forms of KIT result in completely white horses. Roaning, speckles and ticking are very common. Rarely horses with KIT mutations will present with blue eyes but it is still unclear if this is the result of KIT mutations or other white marking genes.

Some studies have also found that e/e horses can present with louder KIT markings than black and bay horses. [21]
Sabino vs. Dominant White vs. White Spotting

Before KIT gene testing was possible, many white markings that shared a similar lacey edged texture were given the name sabino. This helped distinguish them from other known white spotting patterns like tobiano and frame. The first KIT mutation to be documented was sabino-1 in 2005. [6]

Then in 2007 four new KIT mutations were located and named dominant white 1 through 4 as they appeared to be completely dominant and homozygous lethal.[7] This follows naming conventions for other similar genes from other species. It was assumed that the term sabino would be applied to non-homozygous lethal variants while the term dominant white would be used for the homozygous lethal variants.

This assumption was upended in 2009 when seven new mutations were all documented in a single paper, all of which were added to the Dominant White series.[8] Since that time, all future sabino and max white style KIT mutations have been added to the W number sequence. When it became clear that not all of these mutations were in fact dominant or homozygous lethal some geneticists chose to start referring to them as white spotting.

Technically only horses with sabino-1 should be called sabino, but the term sabino is widely used by horse people and many choose to continue to use the term. Alternatively, some use "sabino-like" to describe markings that are similar to the sabino-1 in appearance but do not test as sabino. Technically the term dominant white should be used for any KIT mutation that is fully or nearly fully white when heterozygous and lethal when homozygous. White spotting should be used for KIT mutations that are not homozygous lethal. The problem is often it can be really unclear what category a mutation falls into.

All four terms, sabino, sabino-like, dominant white, and white spotting, are ok to use in most situations. It is a good idea to know what each term means and to use the most correct one you are able to. It’s not however something to overly stress about and even the genetic labs don’t always use the terms consistently.

HorseGeneticsGame.com uses sabino and white spotting for color naming.
Specific Alleles:

Tobiano - Tobiano is not actually a mutation of KIT but is instead an inversion in part of the regulatory area for KIT. Tobiano horses have large rounded patches of color on a white background. [1] Tobiano horses tend to have dark colored heads, chests, and flanks. Homozygous tobianos may be more prone to clusters of smaller spots called cat tracks or paw prints.

Roan 1,2,3 - Roan causes the body of the horse to have evenly dispersed white hairs, while the head, legs, mane, and tail are all left self colored. There are three currently known variants of roan. Roan 1 (R1), roan 2 (R2), and roan 3 (R3) all require one copy to show, and can be safely combined with each other. [2,3,4]

Roan 1 is found in a large number of breeds including those found in Europe, and North and South America. [3]

Roan 2 is limited to North American stock horse breeds. Famous sires with this variant include Metallic Cat and Peptoboonsmal.[3]

Roan 3 is found primarily in quarter horses. Famous sires with this variant include Zippos Mr Good Bar, VS Code Blue, and VS Code Red.[4]

There is a chance, because of the way gene testing works, that all 3 known roan types are actually the same functional mutation with different markers. [3,4]

HorseGenticsGame.com currently only uses R to represent all 3 known roan variants.

Sabino-1 - Sabino-1 (SB1) is found in a wide number of breeds and when heterozygous creates moderate to loud white markings that are lacy edged and roany in texture. Homozygous sabino horses have extensive white markings covering 90% or more of the horse. [6]
White 1 - Found in Franches-Montagnes that descend from the stallion Cigale, this variant results in mostly white horses and is homozygous lethal. [7]

White 2 - Found in Thoroughbreds that descend from the stallion Kentucky Colonel, this variant results in mostly white horses and is homozygous lethal. [7]

White 3 - Found in Arabians that descend from the stallion R Khasper, this variant results in mostly white horses and is homozygous lethal. [7]

White 4 - Found in Camarillo White Horse that descend from the stallion Sultan, this variant results in mostly white horses and is homozygous lethal. [7]

White 5 - Found in Thoroughbreds that descend from the stallion Puchilingui. Horses with W5 are roughly 40% to 60% white. It can combine with minimal KIT mutations like W20 to produce all white individuals. It is presumed to be homozygous lethal with itself and other mutations of KIT that are also homozygous lethal. [8]

White 6 - Found only in the Thoroughbred mare Marumatsu Live. She never produced any foals and the W6 variant passed with her. She was mostly white with heavy chestnut speckles over the majority of her body. [8]

White 7 - Found in Thoroughbreds that descend from the mare Turf Club. W7 horses are 60 to 90% white, with color along the top line and extensive speckles of color over the body. Some all white W7 horses are also known but it is unclear if they have an additional KIT mutation. W7 is suspected to be homozygous lethal. [8]

White 8 - Found in Icelandic horses that descend from Þokkadís vom Rosenhof. W8 horses tend to have 20 to 40% white often with heavy lacing, ticking, and colored speckles. It can produce all white horses when combined with other white mutations. It is probably not homozygous lethal. [8]

White 9- W9 is found in a single line of Holstein horses. [8]

White 10 - Found in Quarter and Paint horses that descended from GQ Santana. W10 horses have 90% plus white coverage with very limited speckling on the body hair. W10 is homozygous lethal. [8]

White 11 - Found in a single line South German Draft horses. [8]

White 12 - Found in a single Thoroughbred which is now deceased. The foal died at 5 weeks with possible complications from his KIT mutation. This variant is extinct. [9]

White 13 - Found in Quarter Horses and Miniature Horse breeds. Heterozygous horses are completely white, and are homozygous lethal.[10]

White 14 - Found in Thoroughbreds that descend from the mare Shirayukihime. Heterozygous horses are all white, or mostly white with moderately sized lacey patches of color over the body. [10]

White 15 - Found in Arabians that descend from the stallion Khartoon Khlassic. Heterozygous individuals tend to have white faces and legs, and white spots on the neck underside and belly. Homozygous individuals tend to be entirely white. [10]

White 16 - Found in Oldenburgs that descend from the mare Celine. Horses with one copy are 30%+ white, with white legs and face, and many markings through the entire body. Many individuals are also completely white, and it is unclear if they are interacting with other KIT mutations or not. The lethality of this mutation is unclear. [10]

White 17 - Found in a single all white Japanese Draft horse. [10]

White 18 - Found in warmbloods that descend from the Swiss mare Colorina Von Hoff. She was approximately 60% white with heavy speckling. It is unclear if she ever had offspring. [11]

White 19 - Found in Arabian horses that descend from the mare Fantasia Vu. Heterozygous horses have 4 white legs, moderate face markings, and frequent lacey belly spotting. They are 20 to 50% white. Homozygous horses are completely white and may have associated health problems. [11]

White 20 - Found in most breeds and is the most common of all KIT mutations. W20 horses can range from no white at all to around 20% white, and homozygous individuals may be visually indistinguishable from heterozygous individuals. Some W20 horses have belly spots, which can be more common when homozygous. W20 has a boosting effect and can make other KIT mutations significantly louder. [11]

White 21 - Found in Icelandic horses that descend from the stallion Ellert frá Baldurshaga. W21 causes extensive roaning throughout the body. [12]

White 22 - Found in Thoroughbreds that descend from the mare Not Quite White. Horses with one copy range from 20 to 40% white, with heavy roaning. Can produce completely white horses when paired with w20 and other minimal white KIT mutations. Appears to be lethal when homozygous. [13]

White 23 - Found in Arabians that descend from the stallion Boomori Simply Stunning. W23 horses are all white. This mutation is thought to be extinct. [14]

White 24 - Found in Italian Trotters the descended from the stallion Via Lattea. Results in completely white individuals when heterozygous. [15]

White 25 - Found in Australian Thoroughbreds that descend from the mare Laughyoumay. Results in near or completely white individuals when heterozygous. [16]

White 26 - Found in Australian Thoroughbreds that descend from the mare Marbrowell. Produces partially white coats with heavy roaning when heterozygous. [16]
White 27 - Found in Australian Thoroughbreds that descend from the mare Milady Fair. Produces extensive speckles on an white background. [16]

White 28 - Found in a single German Riding Pony. [17]

White 29 - N/A skipped number. In HorseGeneticsGame.com W29 is used for horses that descend from the 1 millionth horse created in the game.

White 30 - Found in Berber horses that descend from the stallion Aghilasse. Produces an all white coat when heterozygous.[18]

White 31 - Found in Quarter Horses that descend from the stallion Cookin Merada. Produces face, leg, belly and body markings with highly irregular edges. [19]

White 32 - Found in Quarter Horses and Paints that descend from the mare Small Town Scandal. Produces face legs and belly white when heterozygous. Homozygous horses are 90% plus white with extensive roany speckles. [19]

White 33 - Found in a single Standardbred mare. [20]

White 34 - Found in a large number of breeds. Causes large blazes, socks and belly spots when heterozygous. [21]

White 35 - Found in the “A Sudden Holiday” family of quarter horses. Causes minimal white markings. [22]

White 36 - N/A skipped number.

White 37 - Found in Anglo-Arabian horses the descend from the stallion Viconte des Neigas. [23]

White 38 - Found in Polish Sport horses the descend from the mare Greenlough Melody G. [23]

White 39 - Found in a stock type mare named Oakbank Pretty as a Penny with extensive full body roaning and 95%+ white. [23]
HorseGeneticGame.com Specific Mutations

Donkey Dominant White (DDW)- is a real allele of KIT found in domestic donkeys. [24] It causes completely white individuals when heterozygous and is lethal with all other KIT mutations including roan.

Powder White (PW) - Is an imaginary allele created for HorseGeneticsGame.com. It adds roaning from the top down on a horse, like powdered snow, and is not lethal when combined with any other KIT mutations.

Manchado (M) - Is a spotting pattern found in South America and Argentina especially. It produces dramatic full body speckles and patches throughout the entire body. The current cause is unknown. In HorseGeneticsGame.com this color is represented by KITM. It is dominant in game but probably recessive in real life.
Horses with more than 2 KIT alleles

A frequent point of confusion I see involves horses testing positive for more than two kit alleles (mutations). Of course each horse only has two copies of KIT, one on each copy of chromosome 3, but KIT is a very large gene. KIT itself is approximately 82 kilobases long [7] with its various mutations distributed across not only the entire length of the gene but also spanning into its regulatory regions as well. [1]

Some mutations of KIT have occurred on top of previously existing mutations, like W22 which is a mutation that happened on the previously existing W20 allele. [26] That means all W22 horses will also test as having W20. [25] It’s two mutations occupying a single gene on a single chromosome.

Crossover events can also happen, where two previously distinct KIT mutations become linked on the same chromosome in some lines. This has been documented with compound W32SB1, W32W20, W32W35, W34W35 and even W19W34W35 variants.[25]

HorseGeneticsGame.com does not currently have compound KIT alleles.
Lethality:

What follows is what I have come to understand from reading a large number of papers on KIT 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. KIT performs an important action 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 KIT 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.

KIT mutations range widely in just how broken they are. White 35 causes extremely minimal white markings on its own and boosts the expression of other KIT mutations. It is probably lethal when combined with the max white KIT mutations and probably not lethal with moderate white causing mutations. Mutations that produce all white individuals with only a single copy are definitely going to be lethal with other high white KIT mutations and might also be lethal with roan, or even tobiano.

The more white produced by an allele of KIT the more likely it is to be lethal when homozygous or when combined with other KIT mutations. Two loud KIT alleles are more likely to be lethal than two more minimal KIT alleles. As KIT has variable expressivity, a specific combination may be lethal in some cases but not others.
Citations:
1. Brooks SA, Lear TL, Adelson DL, Bailey E. A chromosome inversion near the KIT gene and the Tobiano spotting pattern in horses. Cytogenet Genome Res. 2007;119(3-4):225-30. doi: 10.1159/000112065. Epub 2008 Feb 1. PMID: 18253033. https://pubmed.ncbi.nlm.nih.gov/18253033/
2. Voß, K.; Tetens, J.; Thaller, G.; Becker, D. Coat Color Roan Shows Association with KIT Variants and No Evidence of Lethality in Icelandic Horses. Genes 2020, 11, 680. https://doi.org/10.3390/genes11060680
3. Everts, R.E.; Caron, R.; Foster, G.; McLoone, K.; Martin, K.; Brooks, S.A.; Lafayette, C. Identification of Two Genetic Haplotypes Associated with the Roan Coat Color in the American Quarter Horse and Other Equine Breeds. Animals 2025, 15, 1705. https://doi.org/10.3390/ani15121705
4. Everts, R.E.; Caron, R.; Foster, G.; McLoone, K.; Simiele, L.; Martin, K.; Brooks, S.A.; Lafayette, C. Identification of a Novel Haplotype Associated with Roan Coat Color in American Quarter Horses. Animals 2025, 15, 2386.
5. https://www.preprints.org/manuscript/202506.2208?fsuid=%2317HZ9P%23b2eda092-7826-4044-89bd-8f15377678b7:9d9546d3-de99-4707-aee6-fc4330ab9959:1768821949850::1%23/1797312171
6. Brooks SA, Bailey E. Exon skipping in the KIT gene causes a Sabino spotting pattern in horses. Mamm Genome. 2005 Nov;16(11):893-902. doi: 10.1007/s00335-005-2472-y. Epub 2005 Nov 11. PMID: 16284805. https://pubmed.ncbi.nlm.nih.gov/16284805/
7. Haase B, Brooks SA, Schlumbaum A, Azor PJ, Bailey E, Alaeddine F, et al. (2007) Allelic Heterogeneity at the Equine KIT Locus in Dominant White (W) Horses. PLoS Genet 3(11): e195. https://doi.org/10.1371/journal.pgen.0030195
8. Haase B, Brooks SA, Tozaki T, Burger D, Poncet PA, Rieder S, Hasegawa T, Penedo C, Leeb T. Seven novel KIT mutations in horses with white coat colour phenotypes. Anim Genet. 2009 Oct;40(5):623-9. doi: 10.1111/j.1365-2052.2009.01893.x. Epub 2009 May 6. PMID: 19456317. https://pubmed.ncbi.nlm.nih.gov/19456317/
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. https://onlinelibrary.wiley.com/doi/10.1111/j.1365-2052.2010.02135.x
10. Haase B et al., “Five novel KIT mutations in horses with white coat colour phenotypes.” (2011) Anim Genet. 42: 337-9. https://www.researchgate.net/publication/51109575_Five_novel_KIT_mutations_in_horses_with_white_coat_colour_phenotypes
11. 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/figure/Coat-colour-phenotypes-of-horses-with-different-genotypes-a-Appaloosa-horse-carrying_fig1_236673503
12. Haase B, Jagannathan V, Rieder S, Leeb T. A novel KIT variant in an Icelandic horse with white-spotted coat colour. Anim Genet. 2015 Aug;46(4):466. doi: 10.1111/age.12313. Epub 2015 Jun 9. PMID: 26059442. https://www.researchgate.net/publication/278045151_A_novel_KIT_variant_in_an_Icelandic_horse_with_white-spotted_coat_colour
13. Dürig N, Jude R, Holl H, Brooks SA, Lafayette C, Jagannathan V, Leeb T. Whole genome sequencing reveals a novel deletion variant in the KIT gene in horses with white spotted coat colour phenotypes. Anim Genet. 2017 Aug;48(4):483-485. doi: 10.1111/age.12556. Epub 2017 Apr 26. PMID: 28444912. https://pubmed.ncbi.nlm.nih.gov/28444912/
14. Holl H.M., Brooks S.A., Carpenter M.L., Bustamante C.D., Lafayette C. A novel splice mutation within equine KIT and the W15 allele in the homozygous state lead to all white coat color phenotypes. Anim. Genet. 2017;48:497–498. doi: 10.1111/age.12554. https://pubmed.ncbi.nlm.nih.gov/28378922/
15. Capomaccio S., Milanesi M., Nocelli C., Giontella A., Verini-Supplizi A., Branca M., Silvestrelli M., Cappelli K. Splicing site disruption in the KIT gene as strong candidate for white dominant phenotype in an Italian Trotter. Anim. Genet. 2017;48:727–728. doi: 10.1111/age.12590. https://pubmed.ncbi.nlm.nih.gov/28856698/
1. Hoban R., Castle K., Hamilton N., Haase B. Novel KIT variants for dominant white in the Australian horse population. Anim. Genet. 2018;49:99–100. doi: 10.1111/age.12627.
2. Hug P., Jude R., Henkel J., Jagannathan V., Leeb T. A novel KIT deletion variant in a German Riding Pony with white-spotting coat colour phenotype. Anim. Genet. 2019;50:761–763. doi: 10.1111/age.12840.
3. Martin K., Patterson Rosa L., Vierra M., Foster G., Brooks S.A., Lafayette C. De novo mutation of KIT causes extensive coat white patterning in a family of Berber horses. Anim. Genet. 2021;52:135–137. doi: 10.1111/age.13017.
4. Patterson Rosa L., Martin K., Vierra M., Foster G., Lundquist E., Brooks S.A., Lafayette C. Two Variants of KIT Causing White Patterning in Stock-Type Horses. J. Hered. 2021;112:447–451. doi: 10.1093/jhered/esab033.
5. Esdaile E., Till B., Kallenberg A., Fremeux M., Bickel L., Bellone R.R. A de novo missense mutation in KIT is responsible for dominant white spotting phenotype in a Standardbred horse. Anim. Genet. 2022;53:534–537. doi: 10.1111/age.13222. https://onlinelibrary.wiley.com/doi/abs/10.1111/age.13222
6. Patterson Rosa L., Martin K., Vierra M., Lundquist E., Foster G., Brooks S.A., Lafayette C. A KIT Variant Associated with Increased White Spotting Epistatic to MC1R Genotype in Horses (Equus caballus) Animals. 2022;12:1958. doi: 10.3390/ani12151958. https://www.mdpi.com/2076-2615/12/15/1958
7. McFadden A., Martin K., Foster G., Vierra M., Lundquist E.W., Everts R.E., Martin E., Volz E., McLoone K., Brooks S.A., et al. 5′UTR Variant in KIT Associated With White Spotting in Horses. J. Equine Vet. Sci. 2023;127:104563. doi: 10.1016/j.jevs.2023.104563.
8. Obradovic NA, McFadden A, Martin K, Vierra M, McLoone K, Martin E, Thomas A, Everts RE, Brooks SA, Lafayette C. "Three Novel KIT Polymorphisms Found in Horses with White Coat Color Phenotypes." (2025) Animals. 15(7), 915; 15(7), 915. https://www.mdpi.com/2076-2615/15/7/915.
9. Haase, B., Rieder, S., & Leeb, T. (2015). Two variants in the KIT gene as candidate causative mutations for a dominant white and a white spotting phenotype in the donkey. Animal Genetics, 46(3), 321-324. doi: 10.1111/age.12282
10. McFadden, A.; Vierra, M.; Robilliard, H.; Martin, K.; Brooks, S.A.; Everts, R.E.; Lafayette, C. Population Analysis Identifies 15 Multi-Variant Dominant White Haplotypes in Horses. Animals 2024, 14, 517. https://doi.org/10.3390/ani14030517
11. W22 Dürig, N.; Jude, R.; Holl, H.; Brooks, S.A.; Lafayette, C.; Jagannathan, V.; Leeb, T. Whole genome sequencing reveals a novel deletion variant in the KIT gene in horses with white spotted coat colour phenotypes. Anim. Genet. 2017, 48, 483–485.
Examples:

Blue Roan E/? a/a R/?, Brown Roan E/? A/? R/?

Bay Roan E/? A/? R/?, Red Roan e/e R/?

Bay Tobiano E/? A/? To/-

Bay heterozygous sabino-1 E/? A/? SB1/-, Bay homozygous sabino-1 E/? A/? SB1/SB1

Bay heterozygous W20 E/? A/? W20/-, Bay homozygous W20 E/? A/? W20/W20

Bay W1 E/? A/? W1/-, Bay W5 E/? A/? W5/-

Bay W8 E/? A/? W8/-, Bay Manchado E/? A/? M/-

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