Home / Veterinary / Diseases and genes

Canine solid coats (black, brown-chocolate)

Dermatological · Dog

A set of dog coat pigmentation traits, not a disease. 'Solid black' (K locus) and 'brown/chocolate' (B locus) are two independent traits. The K locus (CBD103 gene) regulates eumelanin production and determines whether the coat is solid black; the B locus (TYRP1 gene) determines brown/chocolate versus black colouration. The test makes it possible to know each breeding animal's alleles and predict offspring colours.
Inheritance patternMendelian trait. K locus (CBD103) with allele hierarchy KB > kbr > ky; the KB allele (solid black) is dominant. B locus (TYRP1) of autosomal recessive inheritance: two b alleles (b/b) are required for the brown/chocolate coat.
Gene / MutationK locus (CBD103): 3-bp deletion in exon 2 predicting an in-frame deletion of a glycine (ΔG23); KB allele (dominant black), together with kbr (brindle) and ky (OMIA:001416-9615). B locus (TYRP1): variants b^s (stop codon Q331ter, exon 5), b^d (deletion of Pro345, exon 5) and b^c (S41C, exon 2) (OMIA:001249-9615); b^h has also been described in the Siberian Husky.
PenetranceThe concept of disease penetrance does not apply: the effect on colour depends on the genotype, but the final coat phenotype results from interaction with other loci (for example A/agouti and E/extension). Therefore the K and B genotype alone does not predict the animal's entire colour.
Sample typesangre con EDTA
Codevtwu
Turnaround time20 days
Price55,86 €
Breedstodas las razas

Incidence

Multi-breed canine panel: covers the B locus (brown/chocolate) and the associated nose/liver. No universal allele frequencies are published; they vary greatly by breed, line and country and must not be extrapolated.

Clinical signs

Not applicable: it is a phenotypic trait (coat colour), not a clinical picture. It does not cause disease and does not require treatment.

History

The K locus was described when a 3-bp deletion in the CBD103 gene (orthologue of DEFB103) associated with dominant black in the dog was identified in 2007 (Candille et al. 2007). The B locus was linked to the TYRP1 gene, in which Schmutz et al. (2002) identified several variants associated with brown colour. Additional TYRP1 variants have since been described, such as that of the Siberian Husky (Van Buren et al. 2021).

Breeder management

- It is a coat-colour test: it must not be used to cull breeding animals on health grounds\n- Interpret K and B together with the other pigmentation loci (A, E) to predict the colour of the offspring\n- Inform breeders that being a carrier of b or ky does not imply disease\n- Do not mate based only on colour if there are other priority health traits in the breed

Specialist notes

It is not a pathology. The K locus (CBD103) determines solid black/brindle/permit agouti; the B locus (TYRP1) determines brown versus black. The result must be interpreted in the context of the rest of the pigmentation genotype and not as a clinical diagnosis.

References

1. Candille SI et al. 2007. A beta-defensin mutation causes black coat color in domestic dogs. Science. PMID: 17947548
2. Schmutz SM et al. 2002. TYRP1 and MC1R genotypes and their effects on coat color in dogs. Mammalian Genome. PMID: 12140685
3. Van Buren SL et al. 2021. A novel TYRP1 mutation associated with brown coat color in Siberian huskies. Animal Genetics. PMID: 33421162
4. OMIA:001416-9615. Coat colour, dominant black. Online Mendelian Inheritance in Animals.
5. OMIA:001249-9615. Coat colour, brown, TYRP1-related. Online Mendelian Inheritance in Animals.
Price: 55,86 € · Turnaround time: 20 days

← Back to the search