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B locus (Be; Liver) – Lancashire Heeler Type
| Acronym: | Be locus |
| Gene: | TYRP1 |
| Mutation: | c.1025T>G |
| Inheritance: | Autosomal Recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Coat color in dogs is an important characteristic along with hair length, growth pattern, and curl. Coat color is determined by the expression of two melanin pigments, eumelanin (black/brown) and pheomelanin (yellow/red). The tyrosinase-related protein 1 (TYRP1) is a gene with a central role in the regulation of coat color determination in various species, including dogs, and is commonly referred to as the B (brown) Locus. TYRP1 is located in melanocytes, which are specialized cells that produce a pigment called melanin and its mutation causes disruption in regular eumelanin (black pigment) synthesis and results in brown dilution also known as liver color. Five different variants that contribute to brown color have been identified in dogs so far. A variant of TYRP1 that has been described in Lancashire Heeler dogs causes a liver color phenotype due to a single base change resulting in a dysfunctional protein. Dogs carrying the mutation usually have brown coat color and brown noses and foot pads.
The brown liver coat color in Lancashire Heeler dogs has an autosomal recessive mode of inheritance. That means only dogs with two mutated variants will show brown coat color since two copies of brown are needed to change the appearance of eumelanin (black pigment) to brown in both hair follicles and skin. However, the TYRP1 mutation does not affect red/yellow pigment (phaeomelanin) and the final coat color of the dog may also depend on possible mutations within the genes responsible for its synthesis. Genetic testing can identify carriers and help breeders in future mating pairs selection.
Results Reported As
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References:
Wright, H. E., Schofield, E., Mellersh, C. S., Burmeister, L. M. (2019). A novel TYRP1 variant is associated with liver and tan coat colour in Lancashire Heelers. Animal genetics, 50(6), 783. https://doi.org/10.1111/age.12839
Brancalion, L., Haase, B., Wade, C. M. (2022). Canine coat pigmentation genetics: a review. Animal genetics, 53(1), 3–34. https://doi.org/10.1111/age.13154