Champagne gene
The champagne gene is a simple dominant allele responsible for a number of rare horse coat colors.
Horses with the champagne gene have a lightened hair coat and specific eye and skin color traits.
However the 2008 study that mapped the gene and identified it as a dominant trait noted in passing that homozygotes may have less mottling or a slightly lighter hair color.
[5] It is visually difficult to distinguish from classic champagne, and can be confirmed by a DNA test negative for the recessive black (a) allele at Agouti.
The mane and tail may also have "frosting" or light edges, a trait that also occurs in bay duns and some buckskins.
[8][9] Dark gold champagnes can be confused with red dun, while those with paler manes and tails were historically called "pumpkin-skinned palominos."
[10] This sheen makes champagnes difficult to photograph accurately, as the appearance of the coat depends on the lighting.
"[11] The freckles - not mottles, splotches, specks, or blotches - are dark and may have a purple cast, and are small and numerous.
[1] The color qualities of the skin are most evident around the eyes and muzzle, under the tail, and on the udder or sheath.
However, the lightening of these parts of the horse due to the champagne gene is not known to be linked to any health or genetic defects.
However, different traits may interact; they may suppress, enhance, obscure or cancel out various tell-tale clues to the genetic identity of a coat color.
A single copy of the cream gene dilutes red pigment in the coat to gold or yellow, and has a slight effect on the skin and eye color.
The coats are distinguishable from non-champagne duns in that they are several shades lighter, black pigment is chocolate rather than slate, and they may exhibit a sheen.
Horses with the leopard gene or Appaloosas exhibit starkly mottled skin around the muzzle, eyes, anus and sheath or udder.
Many older grays develop the "fleabitten" trait, in which small, interspersed flecks of red occur and often increase in density with age, even as the rest of the coat loses pigment.
At birth, palominos may have pink skin and blue or grey eyes, however these darken within days or weeks.
[26] Occasionally, chestnuts are also born with blue eyes and pink skin, and as gold champagnes often have chestnut-colored foal coats, the two can be difficult to distinguish.
Duns do not exhibit unusually colored skin, though buckskins, like palominos, may be born with blue eyes that darken within days or weeks.
However, Grullos, in absence of any other dilution factors, are not born with pink skin and blue eyes, while champagnes always have these traits.
Grullos, like all duns, will possess primitive markings, and their coats are typically a cooler, slate shade, while classic and sable champagnes are chocolate-toned.
These horses may resemble red duns, however red duns have distinct primitive markings and do not possess pinkish freckled skin or hazel eyes as adults, nor the bright pink skin and bright blue eyes of champagne foals.
Blue-eyed creams, as their name suggests, have blue eyes from birth through adulthood and also have pink skin.
The mottles are substantially larger than the freckles of champagne skin, and leopard complex horses do not necessarily have light eyes.
Further back, the foundation mare of the American Cream Draft horse breed, "Old Granny", was born around 1905 in Iowa.
[29] Her cream-colored coat, pink skin and amber eyes are defining standards for the breed of her descendants, which are now known to be gold champagne.
[36] The champagne locus is on exon 2 of the SLC36A1 gene, which is on chromosome 14 (ECA14); a single nucleotide polymorphism (SNP) exchanges a C for a G at base 76 (c.188C>G) resulting in a missense mutation.
On a protein level, this SNP is predicted to result in the replacement of a threonine with arginine at amino acid 63 (T63R).
[38] SLC36A1 is a member of a loosely united group of over 300 proteins responsible for active transport and facilitated diffusion called the Solute carrier family.
On the other hand, genes in horses which produce white spotting, such as Frame and Sabino1, interrupt or limit the migration of melanocytes from the neural crest.
In other words, the skin, eyes, and hair of horses with the champagne mutation do not lack melanocytes, melanosomes, or melanins, but rather exhibit hypomelanism.
