Effects of Cocoa Genotypes on Coat Color, Platelets and Coagulation Parameters in French Bulldogs.

A nonsense variant in , c.2420G>A or p.Trp807*, was recently discovered as the cause for a brown coat color termed cocoa in French Bulldogs. Here, we studied the genotype-phenotype correlation regarding coat color in mutant dogs that carried various combinations of mutant alleles at other coat color genes. Different combinations of and genotypes resulted in subtly different shades of brown coat colors. As variants in humans cause the Hermansky-Pudlak syndrome type 3, which in addition to oculocutaneous albinism is characterized by a storage pool deficiency leading to bleeding tendency, we also investigated the phenotypic consequences of the variant in French Bulldogs on hematological parameters. mutant dogs had a significantly lowered platelet dense granules abundance. However, no increased bleeding tendencies in daily routine were reported by dog owners. We therefore conclude that in dogs, the phenotypic effect of the variant is largely restricted to pigmentation. While an effect on platelet morphology is evident, we did not obtain any indications for major health problems associated with the cocoa coat color in French Bulldogs. Further studies will be necessary to definitely rule out very subtle effects on visual acuity or a clinically relevant bleeding disorder.