The MATP (membrane-associated transporter protein) gene, or SLC45A2, is a dilution gene in horses.

Alleles

The MATP gene has five currently known alleles.

The CR-allele (cream) is incomplete dominant. One copy dilutes red pigment, while black is not or only very slightly affected. Two copies of cream strongly dilute both red and black pigment, leading to a cream colored horse.

The prl-allele (pearl) is recessive and dilutes the coat color to an apricot-like color. Pearl and cream also interact with each other (CR/prl) and produce pseudo-double cream dilutes.

The sun-allele (sunshine) is recessive. Similar to pearl, CR/sun produces pseudo-double cream dilutes. Two copies of sunshine are expected to lead to a lighter coat, with lighter skin and eyes.

The sno-allele (snowdrop) is recessive. It strongly dilutes both black and red pigment.

The wild-type n-allele leads to the production of normal amounts of pigment.

MATP Color
CR/n
 Palomino, smoky black, buckskin
CR/CR
 Cremello, smoky cream, perlino
prl/n
 Not diluted
prl/prl
 Chestnut pearl, black pearl, bay pearl
CR/prl
 Palomino pearl, smoky black pearl, buckskin pearl
sun/n
 Not diluted
CR/sun
 Palomino sunshine, smoky black sunshine, buckskin sunshine
sno/n
 Not diluted
sno/sno
 Chestnut snowdrop, black snowdrop, bay snowdrop
n/n
 Not diluted

Mehanisms

Pigment cells, called melanocytes, produce the pigments in the hair and skin of horses. The production of pigments can be influenced at different stages, changing the type (black or red) or the amount (dilutions/ white patterns) of pigment that is made.

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The production of black and red pigment involves several different steps. Some of these steps are shared between the two, and some are unique to each pigment type. This is why certain genes will affect all base colors, while others only affect either red or black pigment: they affect different steps.

MATP

Inside the melanocytes are subunits, or organelles, called melanosomes. Pigment production takes place inside these melanosomes.

The MATP gene codes for a protein that regulates the pH of melanosomes. Hereby, MATP can influence the first step of pigment production. Changes in the MATP protein can lead to differences in pigmentation and result in diluted coat colors in a variety of species.

Alleles Mutation Effect
CR
 Point mutation/ substitution (c.457 G => A)
missense mutation		 Diluted pigment
prl
 Point mutation/ substitution (c.985 G => A)
missense mutation		 Diluted pigment, mottling
sun
 Point mutation/ substitution (c.985 G => A)
missense mutation		 Diluted pigment
sno
 Point mutation/ substitution (c.568 G => A)
missense mutation		 Diluted pigment
n
 / Diluted pigment

Colors

Cream
Cream is a dilution, located on the same gene as pearl, sunshine and snowdrop. It lightens the base coat of horses and leads to the colors palomino, buckskin, smoky black, cremello, perlino and smoky cream.
Equine ColorsHannelore Roodhooft
Pearl
Pearl is a dilution, located on the same gene as cream, sunshine and snowdrop. It lightens the base coat of horses and creates the colors chestnut pearl, black pearl and bay pearl.
Equine ColorsHannelore Roodhooft
Sunshine
Sunshine is a dilution, located on the same gene as cream, pearl and snowdrop. It lightens the base coat of horses when combined with cream.
Equine ColorsHannelore Roodhooft
Snowdrop
Snowdrop is a dilution, located on the same gene as cream, pearl and sunshine. It lightens the base coat of horses.
Equine ColorsHannelore Roodhooft

Read more:
Color genes | TBX3 gene

Back to Dilutions

Articles

  1. Locke, M. M., Ruth, L. S., Millon, L .V., Penedo, M. C. T., Murray, J. D., & Bowling, A. T.; The cream dilution gene, responsible for the palomino and buckskin coat colours, maps to horse chromosome 21. Animal Genetics (2001); doi: 10.1046/j.1365-2052.2001.00806.x
  2. Mariat, D., Taourit, S., & Guérin, G.; A mutation in the MATP gene causes the cream coat colour in the horse. Genetics Selection Evolution (2003); doi: 10.1051/gse:2002039
  3. Sevane, N., Sanz, C.R., Dunner, S., Sevane, N., Sanz, C.R., Dunner, S.; Explicit evidence for a missense mutation in exon 4 of SLC45A2 gene causing the pearl coat dilution in horses; Animal Genetics (2019); Doi: 10.1111/age.12784