Equine coat color genetics
This article needs additional citations for verification. (October 2022)
Equine coat color genetics determine a horse's coat color. Many colors are possible, but all variations are produced by changes in only a few genes. The "base" colors of the horse are determined by the Extension locus, which in recessive form (e) creates a solid chestnut or "red" coat. When dominant (E), a horse is black. The next gene that strongly affects coat color, Agouti, when present on a horse dominant for E, limits the black color to the points, creating a shade known as Bay that is so common and dominant in horses that it is informally grouped as a "base" coat color.
Over these three "base" colors can be any number of dilution genes and patterning genes. The dilution genes include the wildtype dun gene, believed to be one of the oldest colors extant in horses and donkeys. Depending on whether it acts on a bay, black, or chestnut base coat, it produces the colors known as bay dun, grullo, and red dun. Another common dilution gene is the cream gene, responsible for palomino, buckskin, and cremello horses. Less common dilutions include Pearl, champagne and silver dapple. Some of these genes also lighten eye color. Genes that affect the distribution of melanocytes create patterns of white spotting or speckling such as in roan, pinto, leopard, white or white spotting, and even some white markings. Finally, the gray gene causes depigmentation of the hair shaft, slowly adding white hairs over the course of several years until the horse's body hair is near or completely white.
Some of these patterns have complex interactions. For example, a single horse may carry both dilution and white patterning genes, or carry genes for more than one spotting pattern. Horses with a gray gene can be born any color and their hair coat will lighten and change with age.
Most wild equids are dun, as were many horses and asses before domestication of the horse. Some were non-dun with primitive markings, and non-dun 1 is one of the oldest coat color mutations, and has been found in remains from 42,700 years ago, along with dun. Non-dun 2, the version of the dun gene that most domestic horses have, is thought to be much more recent, possibly from after domestication. Leopard complex patterns also predate domestication, having been found in horse remains from 20,000 years ago. The mutations that create black and bay color also predate domestication. The mutations causing chestnut, sabino 1, and tobiano pinto are all at least 5000 years old, occurring about the same time as horse domestication. Silver and cream dilutions appeared at least 2,600 years ago, and pearl appeared at least 1400 years ago. The gray mutation is also post-domestication but thought to be thousands of years old as well.
Heritable characteristics are transmitted, encoded, and used through a substance called DNA, which is stored in almost every cell in an organism. Proteins are molecules that do a variety of different things in organisms. The DNA instructions for how to make a protein are called a gene. A change to the sequence of DNA is called a mutation. Mutations are not inherently bad; genetic diversity itself ultimately comes from mutations. Mutations that happen within a gene create alternate forms of that gene, which are called alleles. Alleles of a gene are simply slightly different versions of the instructions on how to make that gene's protein. The term "allele" is sometimes replaced with the word "modifier", because different alleles tend to modify the horse's appearance in some way. DNA is organized into storage structures called chromosomes. A chromosome is simply a very long piece of DNA, and a gene is a much shorter piece of it. With some rare exceptions, a gene is always found at the same place within a chromosome, which is called its locus. For the most part, chromosomes come in pairs, one chromosome from each parent. When both chromosomes have the same allele for a certain gene, that individual is said to be homozygous for that gene. When the two alleles are different, it is heterozygous. A horse homozygous for a certain allele will always pass it on to its offspring, while a horse that is heterozygous carries two different alleles and can pass on either one. A trait that is only expressed when the gene is homozygous for its allele is called recessive, and a trait that has the same effect no matter whether there is one copy or two is called dominant.
Often, the dominant allele is represented by an uppercase letter and the recessive allele by a lowercase letter. For instance, in silver dapple, this is Z for the dominant silver trait and z for the recessive non-silver trait. However, sometimes the alleles are distinguished by which is the "normal" or wild type allele and which is a more recent mutation. In our example z (non-silver) would be wild type and Z would be a mutation. Wild type alleles can be represented as + or n, so Zz, Zz+, Z/+, and Z/n are all valid ways to describe a horse heterozygous for silver. Wild type notation is mainly useful when there is no clear dominant/recessive relationship, such as with cream and frame overo, or when there are many alleles on the same gene, such as with MITF, which has four known alleles. Using n is also common in the results of genetic tests, where a negative result usually means none of the known mutations were found, but does not rule out undiscovered mutations.
Genes affecting coat color generally do so by changing the process of producing melanin. Melanin is the pigment that colors the hairs and skin of mammals. There are two chemically distinct types of melanin: pheomelanin, which is a red to yellow color, and eumelanin, which is brown to black. Melanin is not a protein and therefore there is no gene that changes its structure directly, but there are many proteins involved in the production of melanin or the formation of melanocytes during embryonic development. Mutations that change the structure of proteins with a role in melanin production can result in slightly different variations of melanin. Genes affecting melanocytes, the cells that produce the pigment melanin, do not alter the structure of melanin but instead affect where and whether it is produced.
Extension and agouti
The genes extension and agouti together affect the placement of the two types of pigment, black eumelanin and "red" (coppery brown) pheomelanin.
The extension gene codes for a molecule called the Melanocortin 1 receptor, or MC1R. This receptor straddles the membrane of pigment cells, and when activated it signals the cell to produce black pigment instead of red. A recessive mutation to extension removes this functionality, causing the solid red color of chestnut horses. Extension does not affect skin color. The dominant, wildtype, allele of extension is called E, and the non-extension mutation is called e. Extension is epistatic to agouti, meaning that if a horse has two e alleles, it will be chestnut no matter what genotype it has at agouti.
The agouti gene codes for a molecule called the agouti-signaling protein, or ASIP. This molecule interacts with MC1R, the receptor coded by extension, to block the signal for black pigment production. The signal for black pigment comes from a melanocyte-stimulating hormone, which is present throughout the horse. ASIP is not present everywhere, which allows some areas to be black while others are red. ASIP can also be limited by the phase of hair growth, allowing the tips of the hairs to be black while the base is red. This can be observed in horses which have their winter coats clipped. When shaved close, the black tip is shorn off leaving the phaeomelanic bottom of the shaft. This produces a dull, orange-gold appearance on the body coat which is lost with the spring shed. This is not usually seen in dark bays, which have little red in the hair shaft. A mutation to agouti removes the ability to block the black signal, resulting in a fully black horse. The dominant, wildtype, allele of agouti is called A, and the non-agouti mutation is called a.
|ee||any||Chestnut, or depending on other genes red dun, palomino, cremello, gold champagne, and others.|
|EE or Ee||aa||Black, or depending on other genes grullo, smoky cream, silver dapple, classic champagne, and others.|
|EE or Ee||AA or Aa||Bay, or depending on other genes bay dun, buckskin, perlino, silver bay, amber champagne, and others.|
Extension is found on equine chromosome 3 as part of a linkage group with roan, tobiano, and the KIT gene. Extension is also sometimes called "red factor" and can be identified through DNA testing. Horses with the genotype E/E are sometimes called "homozygous black", however depending on the agouti genotype there is no guarantee that any offspring can be black coated, only that no offspring will be "red".
A study that compared horse genotypes to their coat color phenotypes did find a statistically significant connection that suggested that lighter bay shades were heterozygous for the Extension mutation (E/e) and darker bay shades were homozygous.
Mutations that break protein function generally lead to recessively inherited lighter or redder coat colors in various mammals, while mutations that cause MC1R to be constantly active result in dominantly inherited black coats. In horses, both known mutations break the protein and therefore result in red coats.
Various mutations in the human MC1R gene result in red hair, blond hair, fair skin, and susceptibility to sunburnt skin and melanoma. Polymorphisms of MC1R also lead to light or red coats in mice, cattle, and dogs, among others. The Extension locus was first suggested to have a role in horse coat color determination in 1974 by Stefan Adalsteinsson. Researchers at Uppsala University, Sweden, identified a missense mutation in the MC1R gene that resulted in a loss-of-function of the MC1R protein. Without the ability to produce a functional MC1R protein, eumelanin production could not be initiated in the melanocyte, resulting in coats devoid of true black pigment. Since horses with only one copy of the defective gene were normal, the mutation was labeled e.
There are three known alleles of extension, the wildtype E, and two recessive alleles e and ea which cause chestnut color. The E allele can also be called E+ or EE, and the e allele may also be called Ee.
Of the two known mutations, the first to be discovered was e, and is a change of a single cytosine to thymine at base pair 901 which results in the serine in position 83 being changed to a phenylalanine. In 2000 ea was found, which is a change of a single guanine to adenine at base pair 903, resulting in aspartate being changed to asparagine at position 84 in the polypeptide. Visually there is no difference between the two.
In many species, successive pulses of ASIP block contact between α-MSH and MC1R, resulting in alternating production of eumelanin and pheomelanin; hairs are banded light and dark as a result. In other species, ASIP is regulated such that it only occurs in certain parts of the body. The light undersides of most mammals are due to the carefully controlled action of ASIP. In mice, two mutations on Agouti are responsible for yellow coats and marked obesity, with other health defects. Additionally, the Agouti locus is the site of mutations in several species that result in black-and-tan pigmentations.
One genetics testing lab began offering a test for another allele At, thought to be responsible for seal brown, but it was later found to be inaccurate and is no longer offered.
Dun is one of several genes that control the saturation or intensity of pigment in the coat. Dun is unique in that it is simple dominant, affects eumelanin and pheomelanin equally, and does not affect the eyes or skin. Horses with the dominant D allele (D/D or D/d genotype) exhibit hypomelanism of the body coat, while d/d horses have otherwise intense, saturated coat colors. The mane, tail, head, legs, and primitive markings are not diluted. Zygosity for Dun can be determined with a DNA test.
The Dun locus is TBX3 on equine chromosome 8. The molecular cause behind the dun coat colors is not entirely understood, but the dilution effect comes from the placement of pigment in only part of the hair. The associated coat colors were assigned to the Dun locus in 1974 by Stefan Adalsteinsson, separate from Cream, with the presence of dun dilution indicated by the dominant D allele. The dominant D allele is relatively rare compared to the alternative d allele, and for this reason, the dominant allele is often treated as a mutation. However, the pervasive coat color among wild equids is dun, and researchers from Darwin to modern day consider dun to be the wildtype state.
An older non-dun mutation was found in 2015 and named non-dun 1. It creates primitive markings but does not dilute the base color, and is co-dominant with the more common non-dun 2 but recessive to dun.
- D/D (+/+, D+/D+) wildtype, homozygous dominant. Visually, the horse may be bay dun, grullo, red dun, palomino dun, amber dun, gray, and so on. Such a horse will always pass on the D allele and will therefore always have dun offspring.
- D/d (+/d, D+/Dd) wildtype, heterozygous. Visually indistinguishable from the homozygous D horse.
- d/d (Dd/Dd) non-dun, homozygous recessive. The entire coat, barring the influence of other alleles, is a rich, saturated color. The primitive markings are no longer visible. The horse may be chestnut, bay, black, gray, palomino, and so on.
Cream is another one of the genes that control the saturation or dilution of pigment in the coat. Cream differs from Dun in that it affects the coat, skin, and eyes, and unlike Dun, is dosage dependent rather than simple dominant. Furthermore, the effects on eumelanin and pheomelanin are not equal. Horses with the homozygous recessive genotype (C/C) are not affected by cream. Heterozygotes (CCr/C) have one cream allele and one wildtype non-cream allele. Such horses, sometimes called "single-dilutes", exhibit dilution red pigment in the coat, eyes, and skin to yellow or gold, while eumelanin is largely unaffected. Homozygotes (CCr/CCr) have two cream alleles, and are sometimes called "double-dilutes." Homozygous creams exhibit strong dilution of both red and black pigment in the coat, eyes, and skin to ivory or cream. The skin is rosy-pink and the eyes are pale blue. Cream is now identifiable by DNA test.
The Cream locus is occupied by the Solute carrier family 45, member 2 (SLC45A2) gene, also called the Membrane associated transport protein or Matp gene. The Matp gene encodes a protein illustrated to have roles in melanogenesis in humans, mice, and medaka, though the specific action is not known.
Mutations in the human Matp gene result in several distinct forms of Oculocutaneous albinism, Type IV as well as normal variations in skin and hair color. Mice affected by a condition homologous to cream, called underwhite, exhibit irregularly shaped melanosomes, which are the organelles within melanocytes that directly produce pigment. The first descriptions of the dosage-dependent genetic control of the palomino coat color occurred early on in equine coat color inheritance research. However, the distinction between Dun and Cream remained poorly understood until Stefan Adalsteinsson wrote Inheritance of the palomino color in Icelandic horses in 1974. The mutation responsible, a single nucleotide polymorphism in Exon 2 resulting in an aspartic acid-to-asparagine substitution (N153D), was located and described in 2003 by a research team in France.
- C/C homozygous wildtype. Visually, the horse may be any color other than the cream dilute shades of palomino, buckskin, smoky black, cremello, perlino, smoky cream, and so on.
- CCr/C heterozygous. The colors most commonly associated with this genotype are palomino, buckskin, and smoky black, though the phenotype may vary depending on other factors. Any pheomelanin in the coat is diluted to yellow or gold, and the eyes and skin are often slightly lighter than unaffected horses.
- CCr/CCr homozygous. The colors most commonly associated with this genotype are cremello, perlino, and smoky cream. Regardless, the coat will be cream- or ivory-colored, and the skin a rosy-pink. The eyes are pale blue.
Champagne is a gene that controls the saturation or dilution of pigment in the coat. Unlike Cream, Champagne is not strongly dosage-dependent, and affects both types of pigment equally. Champagne differs from Dun in that it affects the color of the coat, skin, and eyes, and in that the unaffected condition is the wildtype. Horses with the dominant CH allele (CH/CH or CH/ch genotype) exhibit hypomelanism of the body coat, such that phaeomelanin is diluted to gold and eumelanin is diluted to tan. Affected horses are born with blue eyes which darken to amber, green, or light brown, and bright pink skin which acquires darker freckling with maturity. The difference in phenotype between the homozygous (CH/CH) and heterozygous (CH/ch) horse may be subtle, in that the coat of the homozygote may be a shade lighter, with less mottling. Horses with the homozygous recessive genotype (ch/ch) are not affected by champagne. Champagne is now identifiable by DNA test.
The Champagne locus is occupied by the Solute carrier family 36, member 1 (SLC36A1) gene, which encodes the Proton-coupled amino acid transporter 1 (PAT1) protein. This protein is one of many which is involved in active transport. The gene associated with the Cream coat colors is also a solute carrier, and orthologous genes in humans, mice, and other species are also linked to coat color phenotypes. The single nucleotide polymorphism responsible for the champagne phenotype is a missense mutation in exon 2, in which a C is replaced with a G, such that a threonine is replaced with arginine. This mutation was identified and described by an American research team in 2008.
- ch/ch (N/N) wildtype, homozygous recessive. Visually, the horse may be any color other than the champagne shades.
- CH/ch (CH/N) heterozygous. The colors most commonly associated with this genotype are gold champagne, amber champagne, and classic champagne, though the exact phenotype depends on a variety of factors. At birth, the skin is bright pink and the eyes bright blue, darkening to freckled and light brown or green, respectively, with age. Both red and black pigment in the hair are also diluted.
- CH/CH homozygous champagne. Homozygotes, which will never produce non-champagne offspring, are indistinguishable from heterozygotes except that their freckling may be sparser, and their coats a shade lighter.
Alleles and effects
|Locus||Alleles||Effect of combined pairs of alleles|
|EE, Ee, or Eea: Horse forms black pigment in skin and hair, and may be black, seal brown, or bay.|
ee, eea, or eaea: Horse is chestnut; it has black pigment in skin, but red pigment in hair.
|Agouti: Restricts eumelanin, or black pigment, to "points," allowing red coat color to show on body. No visible effect on red horses, as there is no black pigment to restrict.|
AA or Aa horse is bay, black hair shows only in points pattern (usually mane, tail, legs, sometimes tips of ears).
aa: If horse has E allele, then horse will be uniformly black.
C, Prl, or n
|Cr/Cr: Horse is a double dilute cream (cremello, perlino, or smoky cream) and will have creamy off-white hair with pale eyes and skin.|
Cr/n: Horse is a single dilute cream (palomino, buckskin, or smoky black) with red pigment diluted to gold.
prl/prl: Horse is pearl. Red is lightened to an apricot color, and skin coloration is pale.
Cr/prl: Horse is a pseudo-double cream with pale skin and eyes.
n/n: Horse has normal, undiluted, coloration.
ND2 or d
|DD, D/ND1, or Dd: Dun gene Wildtype dilution. Horse shows a diluted body color to pinkish-red, yellow-red, yellow or mouse gray and has dark points called primitive markings including dorsal stripe, shoulder stripe and leg barring.|
ND1/ND1: Horse is not diluted but does have a darker dorsal stripe and may have other primitive markings.
ND1/d: Horse is not diluted, but has faint primitive markings.
dd: Horse has undiluted coat color with no primitive markings.
|Champagne: A rare but dominant dilution gene that creates pumpkin-colored freckled skin, amber, greenish, or blue eyes, and gives a bronze cast to hair. The skin surrounding the eye must be pink with freckles in adulthood. |
ChCh or Chch: Champagne dilution evident (See Genetic Formulas Chart below.)
chch: No champagne dilution 
|PMEL or SILV
|ZZ or Zz: Silver dapple - Dilutes eumelanin or black pigment. Converts black to brown with white mane and tail or results in silver coloring.|
zz: No silver dapple.
|Mu/Mu or Mu/mu: Mushroom - Dilutes red pigment to a sandy-gray color.|
mu/mu: No mushroom effect.
|GG or Gg: gray gene. Horse shows progressive silvering with age to white or flea-bitten, but is born a non-gray color. Pigment is always present in skin and eyes at all stages of silvering. Gray horses range from white to dark gray depending on age and the proportion of white hairs in the coat. Horses' coats gray in a manner similar to graying in human hair.|
gg: Horse does not gray with aging.
(Frame Overo/Lethal white syndrome)
|O or Fr
o or fr
|Oo: Frame Overo pattern - Pinto horse pattern that forms a solid frame around white spotting. White is usually horizontal in orientation with jagged edges, color crosses the back and legs, face is often white. The Overo "O" allele is different from overo as a color pattern classification in those registries which also include the splashed white and sabino genes under the heading "overo."|
oo: No overo pattern present.
OO: Homozygous overo is lethal white syndrome, characterized by an incomplete colon and the inability to defecate, which leads to death or humane euthanization within days of birth.
|Inversion starting about 100k bp downstream of KIT
|TOTO or TOto: Tobiano, a form of pinto patterning. Produces regular and distinct ovals or rounded patterns of white and color with a somewhat vertical orientation. White extends across the back, down the legs, but face and tail are usually dark.|
toto: No tobiano pattern present.
|KIT or CD117
|Complicated. See white and sabino.|
W/W: Thought to be lethal. Embryo reabsorbed or fetus dies en utero.
W/n, W5/W20, W20/W22, or SB1/SB1: Horse has pink skin and white hair, usually with brown or dark eyes. Hair coat is white from birth. There may be some patches of color, which may fade to white as the horse grows older. When this is caused by SB1 it may be referred to as "maximum sabino".
SB1/n - Classic sabino has assorted pinto or roan-like markings. Recognized by abundant white on the legs, belly spots or body spots that can be flecked or roaned, chin spots, or white on the face extending past the eyes. Sabino is registered as overo by some registries, but is not frame overo and does not cause overo lethal white syndrome.
n/n: Horse is fully pigmented.
Note: The above applies when W is one of W1, W2, W3, W4, W9, W10, W11, W13, W14, W17, W23, W24, or W25. See white for a description of the other W alleles.
|Near or at KIT
|RnRn or Rnrn: roan pattern of white hair mixed in with base color. Head and lower legs remain dark. It used to be thought that roan was homozygous lethal, but since then living homozygous roan horses have been found.|
rnrn: No roan pattern.
|Appaloosa or Leopard spotting gene. Produces coat spotting patterns, mottling over otherwise dark skin, striped hooves and white sclera around the eye. Can also produce varnish roan.|
LpLp: Fewspot, snowcap, or heavily varnish roaned horse.
Lplp: Leopard, blanket, or varnish roan horse.
lplp: No leopard complex traits.
|PATN1/PATN1 or PATN1/n: Combined with the leopard complex, produces a leopard/fewspot or near-leopard/near-fewspot horse. It has no visible effect on lplp horses.|
n/n: Horse is solid or varnish roan, unless it carries other (as yet undiscovered) PATN genes.
(Splashed white, macchiato)
|SW1/SW1: Classic splashed white.|
SW1/n: White markings on head and legs.
SW3/SW3: May be embryonic lethal.
SW3/n: Splashed white.
Macchiato/n: The macchiato allele has been found in a single stallion named Apache, who had a white pattern in similar places as for splashed white, a dilution, deafness, and reduced fertility. It is likely that this mutation will not be passed on.
n/n: No splashed white or macchiato.
|SW2/SW2: Previously thought to be lethal, but a single SW2/SW2 horse has been found.|
SW2/n: Splashed white, but usually not as loud as a classic splash.
SW4/SW4: Might be lethal.
SW4/n: Splashed white or broad blaze.
n/n: No splashed white.
Notable color combinations
|Bay||E/-||A/-||d/d||ch/ch||z/z||n/n or n/prl|
|Chestnut||e/e||-/-||d/d||ch/ch||-/-||n/n or n/prl|
|Black||E/-||a/a||d/d||ch/ch||z/z||n/n or n/prl|
|Bay dun||E/-||A/-||D/-||ch/ch||z/z||n/n or n/prl|
|Red dun||e/e||-/-||D/-||ch/ch||-/-||n/n or n/prl|
|Grullo (Blue dun)||E/-||a/a||D/-||ch/ch||z/z||n/n or n/prl|
|Amber champagne||E/-||A/-||d/d||Ch/-||z/z||n/n or n/prl|
|Gold champagne||e/e||-/-||d/d||Ch/-||-/-||n/n or n/prl|
|Classic champagne||E/-||a/a||d/d||Ch/-||z/z||n/n or n/prl|
|Silver bay||E/-||A/-||d/d||ch/ch||Z/-||n/n or n/prl|
|Silver black||E/-||a/a||d/d||ch/ch||Z/-||n/n or n/prl|
|Bay pseudo-double pearl||E/-||A/-||d/d||ch/ch||z/z||Cr/prl|
|Apricot (Chestnut pearl)||e/e||-/-||d/d||ch/ch||-/-||prl/prl|
|Chestnut pseudo-double pearl||e/e||-/-||d/d||ch/ch||-/-||Cr/prl|
|Black pseudo-double pearl||E/-||a/a||d/d||ch/ch||z/z||Cr/prl|
- ^ a b Pruvost, Melanie; Bellone, Rebecca; Benecke, Norbert; Sandoval-Castellanos, Edson; Cieslak, Michael; Kuznetsova, Tatyana; Morales-Muñiz, Arturo; O'Connor, Terry; Reissmann, Monika; Hofreiter, Michael; Ludwig, Arne (15 November 2011). "Genotypes of predomestic horses match phenotypes painted in Paleolithic works of cave art". Proceedings of the National Academy of Sciences. 108 (46): 18626–18630. Bibcode:2011PNAS..10818626P. doi:10.1073/pnas.1108982108. PMC 3219153. PMID 22065780.
- ^ a b c Imsland, Freyja; McGowan, Kelly; Rubin, Carl-Johan; Henegar, Corneliu; Sundström, Elisabeth; Berglund, Jonas; Schwochow, Doreen; Gustafson, Ulla; Imsland, Páll; Lindblad-Toh, Kerstin; Lindgren, Gabriella; Mikko, Sofia; Millon, Lee; Wade, Claire; Schubert, Mikkel; Orlando, Ludovic; Penedo, Maria Cecilia T; Barsh, Gregory S; Andersson, Leif (February 2016). "Regulatory mutations in TBX3 disrupt asymmetric hair pigmentation that underlies Dun camouflage color in horses". Nature Genetics. 48 (2): 152–158. doi:10.1038/ng.3475. PMC 4731265. PMID 26691985.
- "A horse of a different color: Genetics of camouflage and the dun pattern". ScienceDaily (Press release). December 21, 2015.
- ^ a b Wutke, Saskia; Benecke, Norbert; Sandoval-Castellanos, Edson; Döhle, Hans-Jürgen; Friederich, Susanne; Gonzalez, Javier; Hallsson, Jón Hallsteinn; Hofreiter, Michael; Lõugas, Lembi; Magnell, Ola; Morales-Muniz, Arturo; Orlando, Ludovic; Pálsdóttir, Albína Hulda; Reissmann, Monika; Ruttkay, Matej; Trinks, Alexandra; Ludwig, Arne (23 December 2016). "Spotted phenotypes in horses lost attractiveness in the Middle Ages". Scientific Reports. 6 (1): 38548. Bibcode:2016NatSR...638548W. doi:10.1038/srep38548. PMC 5141471. PMID 27924839.
- ^ Rosengren Pielberg, Gerli; Golovko, Anna; Sundström, Elisabeth; Curik, Ino; Lennartsson, Johan; Seltenhammer, Monika H; Druml, Thomas; Binns, Matthew; Fitzsimmons, Carolyn; Lindgren, Gabriella; Sandberg, Kaj; Baumung, Roswitha; Vetterlein, Monika; Strömberg, Sara; Grabherr, Manfred; Wade, Claire; Lindblad-Toh, Kerstin; Pontén, Fredrik; Heldin, Carl-Henrik; Sölkner, Johann; Andersson, Leif (August 2008). "A cis-acting regulatory mutation causes premature hair graying and susceptibility to melanoma in the horse". Nature Genetics. 40 (8): 1004–1009. doi:10.1038/ng.185. PMID 18641652. S2CID 6666394.
- "Genetics Of White Horses Unraveled: One Mutation Makes Ordinary Horses Turn Grey, Then White, Very Young". ScienceDaily (Press release). July 23, 2008.
- ^ Micillo, Raffaella; Panzella, Lucia; Koike, Kenzo; Monfrecola, Giuseppe; Napolitano, Alessandra; d'Ischia, Marco (17 May 2016). "'Fifty Shades' of Black and Red or How Carboxyl Groups Fine Tune Eumelanin and Pheomelanin Properties". International Journal of Molecular Sciences. 17 (5): 746. doi:10.3390/ijms17050746. PMC 4881568. PMID 27196900.
- ^ a b Online Mendelian Inheritance in Man (OMIM): MELANOCORTIN 1 RECEPTOR; MC1R - 155555
- ^ a b c "Red Factor". UC Davis Veterinary Genetics Laboratory. Retrieved Nov 20, 2021.
- ^ Wolf Horrell, Erin M.; Boulanger, Mary C.; D'Orazio, John A. (31 May 2016). "Melanocortin 1 Receptor: Structure, Function, and Regulation". Frontiers in Genetics. 7: 95. doi:10.3389/fgene.2016.00095. PMC 4885833. PMID 27303435.
- ^ Online Mendelian Inheritance in Man (OMIM): AGOUTI SIGNALING PROTEIN; ASIP - 600201
- ^ Sponenberg, D. Phillip; Bellone, Rebecca (2017). "Introduction". Equine Color Genetics (4th ed.). John Wiley & Sons. pp. 1–21. doi:10.1002/9781119130628.ch1. ISBN 978-1-119-13062-8.
- ^ a b Rieder S, Taourit S, Mariat D, Langlois B, Guérin G (2001). "Mutations in the agouti (ASIP), the extension (MC1R), and the brown (TYRP1) loci and their association to coat color phenotypes in horses (Equus caballus)". Mammalian Genome. 12 (6): 450–455. doi:10.1007/s003350020017. PMID 11353392. S2CID 2012676.
- ^ "Agouti (Bay/Black)". UC Davis Veterinary Genetics Laboratory. Retrieved Nov 20, 2021.
- ^ Voß, Katharina; Tetens, Julia; Thaller, Georg; Becker, Doreen (2020). "Coat Color Roan Shows Association with KIT Variants and No Evidence of Lethality in Icelandic Horses". Genes. 11 (6): 680. doi:10.3390/genes11060680. PMC 7348759. PMID 32580410.
- ^ Fontanesi, L.; Tazzoli, M.; Beretti, F.; Russo, V. (October 2006). "Mutations in the melanocortin 1 receptor (MC1R) gene are associated with coat colours in the domestic rabbit (Oryctolagus cuniculus)". Animal Genetics. 37 (5): 489–493. doi:10.1111/j.1365-2052.2006.01494.x. PMID 16978179.
- ^ Fontanesi, Luca; Beretti, Francesca; Riggio, Valentina; Dall'Olio, Stefania; González, Elena Gómez; Finocchiaro, Raffaella; Davoli, Roberta; Russo, Vincenzo; Portolano, Baldassare (December 2009). "Missense and nonsense mutations in melanocortin 1 receptor (MC1R) gene of different goat breeds: association with red and black coat colour phenotypes but with unexpected evidences". BMC Genetics. 10 (1): 47. doi:10.1186/1471-2156-10-47. PMC 2748843. PMID 19706191.
- ^ Robbins, L.S.; Nadeau, J. H.; Johnson, K. R.; Kelly, M. A.; Roselli-Rehfuss, L.; Baack, E.; Mountjoy, K. G.; Cone, R. D. (1993). "Pigmentation phenotypes of variant extension locus alleles result from point mutations that alter MSH receptor function". Cell. 72 (6): 827–834. doi:10.1016/0092-8674(93)90572-8. PMID 8458079. S2CID 12179800.
- ^ Joerg, H; Fries, H. R.; Meijerink, E.; Stranzinger, G. F. (1996). "Red coat color in Holstein cattle is associated with a deletion in the MSHR gene". Mammalian Genome. 7 (4): 317–318. doi:10.1007/s003359900090. PMID 8661706. S2CID 2497765.
- ^ Newton, JM; Wilkie, A. L.; He, L.; Jordan, S. A.; Metallinos, D. L.; Holmes, N. G.; Jackson, I. J.; Barsh, G. S. (2000). "Melanocortin 1 receptor variation in the domestic dog". Mammalian Genome. 11 (1): 24–30. doi:10.1007/s003350010005. PMID 10602988. S2CID 1755908.
- ^ a b c Adalsteinsson, Stefán (January 1974). "Inheritance of the Palomino Color in Icelandic Horses". Journal of Heredity. 65 (1): 15–20. doi:10.1093/oxfordjournals.jhered.a108448. PMID 4847742.
- ^ Marklund, L; Moller MJ; Sandberg K; Andersson L (Dec 1996). "A missense mutation in the gene for melanocyte-stimulating hormone receptor (MC1R) is associated with the chestnut coat color in horses". Mammalian Genome. 7 (12): 895–9. doi:10.1007/s003359900264. PMID 8995760. S2CID 29095360.
- ^ Wagner; Reissmann (2000). "New polymorphism detected in the horse MC1R gene". Animal Genetics. 31 (4): 289–290. doi:10.1046/j.1365-2052.2000.00655.x. PMID 11086549.
- ^ Rendo F, Iriondo M, Manzano C, Estonba A (16 December 2009). "Identification of horse chestnut coat color genotype using SNaPshot". BMC Research Notes. 2: 255. doi:10.1186/1756-0500-2-255. PMC 2805676. PMID 20015355.
- ^ Drogemuller, C; Giese, A.; Martins-Wess, F.; Wiedemann, S.; Andersson, L.; Brenig, B.; Fries, R.; Leeb, T (2006). "The mutation causing the black-and-tan pigmentation phenotype of Mangalitza pigs maps to the porcine ASIP locus but does not affect its coding sequence" (PDF). Mammalian Genome. 17 (1): 58–66. doi:10.1007/s00335-005-0104-1. PMID 16416091. S2CID 22542101.
- ^ "at Spontaneous Allele Detail". The Jackson Laboratory. 2009-05-23. Retrieved 2009-05-26.
- ^ "Equine Testing Services". Pet DNA Services of AZ. Archived from the original on 2009-05-22. Retrieved 2009-05-26.
- ^ a b "Dun Zygosity Test". UC Davis Veterinary Genetics Laboratory. Retrieved 2009-05-27.
- ^ Locke, M. M.; Penedo, M. C. T.; Bricker, S. J.; Millon, L. V.; Murray, J. D. (October 2002). "Linkage of the grey coat colour locus to microsatellites on horse chromosome 25: Linkage mapping of horse grey locus". Animal Genetics. 33 (5): 329–337. doi:10.1046/j.1365-2052.2002.00885.x. PMID 12354140.
- ^ Darwin, C.R. (1861). On the origin of species (3 ed.). London: John Murray. pp. 181–185. ISBN 0-8014-1319-2.
- ^ Ludwig A, Pruvost M, Reissmann M, Benecke N, Brockmann GA, Castaños P, Cieslak M, Lippold S, Llorente L, Malaspinas AS, Slatkin M, Hofreiter M (2009-04-24). "Coat Color Variation at the Beginning of Horse Domestication". Science. 324 (5926): 485. Bibcode:2009Sci...324..485L. doi:10.1126/science.1172750. PMC 5102060. PMID 19390039.
- ^ a b "Cream". UC Davis Veterinary Genetics Laboratory. Retrieved 2019-04-18.
- ^ a b c Mariat, Denis; Sead TAOURIT; Gérard GUÉRIN (2003). "A mutation in the MATP gene causes the cream coat colour in the horse". Genetics Selection Evolution. INRA, EDP Sciences. 35 (1): 119–133. doi:10.1051/gse:2002039. PMC 2732686. PMID 12605854.
- ^ Online Mendelian Inheritance in Man (OMIM): MEMBRANE-ASSOCIATED TRANSPORTER PROTEIN; MATP - 606202
- ^ Sweet HO, Brilliant MH, Cook SA, Johnson KR, Davisson MT (1998). "A new allelic series for the underwhite gene on mouse chromosome 15". Journal of Heredity. 89 (6): 546–51. doi:10.1093/jhered/89.6.546. PMID 9864865.
- ^ Wriedt-Ski, Chr. (December 1925). "Vererbungsuntersuchungen beim Pferd" [Heredity Studies in the Horse]. Zeitschrift für Induktive Abstammungs- und Vererbungslehre (in German). 37 (1): 88–101. doi:10.1007/BF01763328. S2CID 21565876.
- ^ a b c d e f Cook, D; Brooks S; Bellone R; Bailey E (2008). Barsh, Gregory S. (ed.). "Missense Mutation in Exon 2 of SLC36A1 Responsible for Champagne Dilution in Horses". PLOS Genetics. 4 (9): e1000195. doi:10.1371/journal.pgen.1000195. PMC 2535566. PMID 18802473.
- ^ "Identifying the Champagne Colored Horse". International Champagne Horse Registry. Retrieved 2009-05-26.
- ^ "Genetics of Champagne Coloring." The Horse online edition, accessed May 31, 2007 at http://www.thehorse.com/viewarticle.aspx?ID=9686
- ^ Tanaka; Leeb; Mack; Jagannathan; Flury; Bachmann; McDonnell; Penedo; Bellone (Jan 2019). A Frameshift Variant in MFSD12 Explains the Mushroom Coat Color Dilution in Shetland Ponies. XXVII Plant and Animal Genome Conference. San Diego.
- ^ Brooks; Lear; Adelson; Bailey (2007). "A chromosome inversion near the KIT gene and the Tobiano spotting pattern in horses". Cytogenetic and Genome Research. 119 (3–4): 225–230. doi:10.1159/000112065. PMID 18253033. S2CID 22835035.
- ^ Mau, C.; Poncet, P. A.; Bucher, B.; Stranzinger, G.; Rieder, S. (2004). "Genetic mapping of dominant white (W), a homozygous lethal condition in the horse (Equus caballus)". Journal of Animal Breeding and Genetics. 121 (6): 374–383. doi:10.1111/j.1439-0388.2004.00481.x.
- ^ Marklund, S.; Moller, M.; Sandberg, K.; Andersson, L. (1 March 1999). "Close association between sequence polymorphism in the KIT gene and the roan coat color in horses". Mammalian Genome. 10 (3): 283–288. doi:10.1007/s003359900987. PMID 10051325. S2CID 32790547.
- ^ "Roan Zygosity Test". Veterinary Genetics Laboratory. UC Davis Veterinary Medicine.
- ^ Vickery, Donna. "A discussion of equine roan color genetics". Hancock Horses.
- ^ a b "UC Davis Splashed White".
- ^ "Center for Animal Genetics Macchiato".
- ^ a b Hauswirth; Haase; Blatter (2012). "Mutations in MITF and PAX3 Cause "Splashed White" and Other White Spotting Phenotypes in Horses". PLOS Genetics. 8 (4): e1002653. doi:10.1371/journal.pgen.1002653. PMC 3325211. PMID 22511888.
- "Horse coat color tests" from the UC Davis Veterinary Genetics Lab
- "Introduction to Coat Color Genetics" from Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis. Web Site accessed January 12, 2008
- "Horse Color Calculator" From Animal Genetics Incorporated. This creates the possible coat coloring of the offspring from the imputed color of sire and dam.
- "Horse Genome Project" A quick summary of horse color genetics.