Gene or Region: SLC36A1
Reference Variant: C (N)
Mutant Variant: G (CH)
Affected Breeds: Several
Research Confidence: High - Findings reproduced in multiple studies
Explanation of Results: CH/CH = Homozygous Champagne CH/n = Heterozygous Champagne n/n = Non-Champagne
Champagne is a variant of SLC36A1 that reduces the amount of both black and red pigments. CH is an example of a dominant allele, indicating that horses with two copies (CH/CH) or one copy (CH/n) display the same degree of coat color dilution. Foals are born with light skin and blue eyes, both of which somewhat darken with age. Adult champagnes have pink “pumpkin” skin with visible mottling on hairless regions, as well as amber, green, or light brown eyes.
While the coat color produced by CH is visually similar to the effect of a single CR allele, cream horses tend to develop dark skin and eyes. However, horses with two prl alleles also retain lightened skin and eye color. Additionally, horses with one CR and one prl allele strongly resemble horses with one CR and at least one CH allele. Since CH is a dominant trait and prl is recessive, knowing the colors of the parents can help indicate which dilution a horse has – a champagne horse always must have at least one champagne parent. In cases where the coat color of the parents are unclear or unknown, genetic testing can be used to identify the dilution.
SLC36A1 is a transporter protein whose role in the pigmentation system is not well understood. To date, the champagne mutation is the only variant associated with a coat color phenotype in the scientific literature. This mutation was found to be in perfect association within the original study population of 183 horses, and further commercial testing has not found champagne horses negative for this allele. This SNP is a single base substitution that results in an amino acid change that likely alters the function of the encoded protein.
Genotype and Phenotype
Black with champagne (E/_ a/a CH/): Classic Champagne Bay with champagne (E/ A/_ CH/): Amber Champagne Chestnut with champagne (e/e CH/): Gold Champagne
Cook D et al., “Missense mutation in exon 2 of SLC36A1 responsible for champagne dilution in horses.” (2008) PLoS Genet. 4: e1000195.
Congential Stationary Night Blindness (CSNB) is characterized by the inability to see well in low light and no-light situations. It is linked to Leopard Complex Spotting (LP), where homozygous horses (LP/LP) will have CSNB. Congential Stationary Night Blindness is present at birth and is non-progressive.
Cream (CR) is a dilution that is characterized by lightening both black-based and red-based horses. A single CR allele lightens red pigment to gold but does not affect Black pigment. Two CR alleles results in extreme dilution of the hair, skin, and eyes of any color, though black-based horses tend to retain more pigment than red-based horses.