Solid Black Coat

The solid black coat color is the result of an alteration in the ASIP gene.

Definition

This coloration is characterized by being solid and dark, predominantly eumelanin, and does not show the banding pattern typical of the agouti allele. The genetic variant is located in the ASIP gene, which regulates the distribution of the pigments eumelanin (black/brown) and pheomelanin (red/yellow) by inhibiting melanocortin 1 receptor (MC1R) signaling.

Genetic basis

The solid black coat in cats is also known as the non-agouti allele phenotype. Inheritance of this trait is autosomal recessive, which means that the cat must receive two copies of the c.123_124del deletion in the ASIP gene to express a completely black coat. If a cat inherits only one copy of this variant, it retains a small percentage of ASIP gene activity, which may result in a brindle pattern in the coat due to the presence of some pheomelanin bands.

Other relevant information

The ASIP gene produces the agouti protein, which acts as a paracrine signaling molecule, binding to the MC1R receptor and inhibiting eumelanin production while favoring pheomelanin production. In the absence of agouti protein function, eumelanin production is continuous, resulting in a uniform black coat. This trait can be masked by the expression of a variant related to orange coloration at the O locus on the X chromosome, which can influence pigment distribution and alter coat appearance.

Bibliography

Eizirik E, Yuhki N, Johnson WE, et al. Molecular genetics and evolution of melanism in the cat family. Curr Biol. 2003;13(5):448-453.

Schmidt-Küntzel A, Nelson G, David VA, et al. A domestic cat X chromosome linkage map and the sex-linked orange locus: mapping of orange, multiple origins and epistasis over nonagouti. Genetics. 2009 Apr;181(4):1415-25.