trait in dogs. Instead, TYRP1 (tyrosinase related protein 1) was found to be responsible. This enzyme is localised to melanosomes, the cellular organelles that produce and store pigments, and serves to catalyze oxidation of eumelanin precursors.

In dogs, three mutations in the TYRP1 gene have been identified, one resulting in a truncation of the protein, the other two leading to an amino acid deletion