General Description

Cream (CR, sometimes seen as “Crème”) and pearl (prl, sometimes called “apricot” or “Barlink factor”) are variants of the SLC45A2/MATP gene that reduce the overall amount of pigmentation, thus diluting the color of the horse. The CR allele is an example of incomplete dominance – a single copy (CR/n) behaves differently than two copies (CR/CR). Heterozygous creams (CR/n) have red pigments diluted to gold, with black pigments mostly unaffected. However, homozygous creams (CR/CR) show an extreme dilution of the hair, skin, and eyes of any color, though black based horses tend to retain more pigment than red based horses.

Genotype and Phenotype

Black with single cream (E/_ a/a CR/N): Smoky Black Black with double cream (E/_ a/a CR/CR): Smoky Cream

Bay with single cream (E/_ A/_ CR/N): Buckskin Bay with double cream (E/_ A/_ CR/CR): Perlino

Chestnut with single cream (e/e CR/N): Palomino Chestnut with double cream (e/e CR/CR): Cremello

-Other dilutions, modifiers, and spotting genes can further alter the color of a horse – for simplicity, we have not named all possible combinations! -Unlike most equine coat colors, pearl does not currently have a commonly used set of names. Pearl horses are often registered as the corresponding champagne or cream coat colors.

Gene Information

SLC45A2 is a transporter protein involved in pigment synthesis. Mutations in this gene have been well documented to result in a variety of dilution and albino coat colors in many species. Both mutations are single base substitutions that change an amino acid, and thus likely alter the function of the encoded protein.

References

Mariat D et al., “A mutation in the MATP gene causes the cream coat colour in the horse.” (2003) Genet Sel Evol. 35: 119-33.

Bailey E & Brooks S. “Color Diluting Genes.” (2013) Horse Genetics, CABI International, Boston, MA, 42-52.

Stamatelakys I. “Precious Pearls” (2009) Paint Horse Journal. May 2009, 76-83.