Cream (CR)

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.

Prl is an example of a recessive trait – two copies are needed to see an affect. While a single prl allele does not affect the coat color, some horses show skin lightening/freckling. Prl homozygotes (prl/prl) are visually similar to horses with the champagne dilution, displaying diluted hair, skin, and eye color. A horse with one CR and one prl allele is known as a compound heterozygote, and appears similar to double cream or cream plus champagne dilutions.

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Genotype and Phenotype (Color Names)

Black with single cream (E/_ a/a CR/N): smoky black

Black with double cream (E/_ a/a CR/CR): smoky cream

Black with single pearl (E/_ a/a prl/N): black or black pearl

Black with double pearl (E/_ a/a prl/prl): classic pearl

Black with one cream one pearl (E/_ a/a CR/prl): smoky black pearl

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Bay with single cream (E/_ A/_ CR/N): buckskin

Bay with double cream (E/_ A/_ CR/CR): perlino

Bay with single pearl (E/_ A/_ prl/N): bay or bay pearl

Bay with double pearl (E/_ A/_ prl/prl): amber pearl

Bay with one cream one pearl (E/_ A/_ CR/prl): buckskin pearl

Chestnut with single cream (e/e CR/N): palomino

Chestnut with double cream (e/e CR/CR): cremello

Chestnut with single pearl (e/e prl/N): chestnut or chestnut pearl

Chestnut with double pearl (e/e prl/prl): gold pearl

Chestnut with one cream one pearl (e/e CR/prl): palomino pearl

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* 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.

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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.

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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.