Dominant black coat

The dominant black coat trait is characterized by the presence of a solid black coat.

Definition

This trait expresses a specific pigmentation phenotype consisting of a solid black coat. The variant responsible for the trait is found in the CBD103 gene (known as the K locus) which expresses a protein with high affinity for the MC1R gene, and through this interaction, can modify the pigmentation pattern of the dog's coat.

Genetic basis

The dominant black coat variant, also known as the "KB" allele, is located at the K locus. The presence of one or two copies of the c.231_233del variant results in the expression of the trait in dogs, as it is a dominant trait. If only one copy of the c.231_233del variant is found, the phenotype known as "brindle", characterised by alternating black/brown and red/yellow stripes in various shades, is likely to be expressed. If no copy of the variant is found, a coat pattern dependent on locus A (Agouti) will be expressed.

Other relevant information

The "KB" variant promotes the synthesis of black pigment (eumelanin) by inhibiting the expression of the A locus, and to do so, requires the expression of a single copy of the variant. In the absence of any KB variant, the A locus can be expressed and inhibit eumelanin synthesis by altering the functionality of the MC1R gene. However, although the A locus may be expressed, the final phenotype could also be influenced by the genotypes of the E and B loci. Breeds that commonly possess the trait are Belgian Sheepdog, Newfoundland, Black Russian Terrier, Irish Water Spaniel, Labrador Retriever, German Shorthaired Pointer, Schipperke, Portuguese Water Dog and Boykin Spaniel.

Bibliography

Candille SI, Kaelin CB, Cattanach BM,et al. A -defensin mutation causes black coat color in domestic dogs. Science. 2007 Nov 30;318(5855):1418-23."

Kerns JA, Cargill EJ, Clark LA,et al. Linkage and segregation analysis of black and brindle coat color in domestic dogs. Genetics. 2007 Jul;176(3):1679-89.