Cocoa (Co Locus) French Bulldog Type

General Information: The Co Locus (Co) cocoa phenotype in French Bulldogs is characterized by a dark brown eumelanin pigment that affects the coat, skin, and nose, distinguished from traditional chocolate colors by its genetic basis in the HPS3 gene rather than the B locus associated with liver color. This gene affects the maturation and transport of melanosomes, the organelles responsible for pigment distribution. Puppies with the cocoa mutation may appear greyish-brown at birth, transitioning to a richer dark brown as they mature. Unlike the liver color, which can vary across different breeds, the cocoa color in French Bulldogs is unique and has been observed to intensify with age, often accompanied by green to amber eye color changes.

Gene / Testing Information: Genetic testing for the Co Locus (Co) cocoa coat color in French Bulldogs involves analysis of the HPS3 gene. This mutation is autosomal recessive, meaning a dog needs to inherit two copies of the mutated gene (one from each parent) to display the cocoa phenotype. Carriers of one copy of the mutation (Co/co) do not exhibit the cocoa color but can pass the mutation to their offspring. Breeding two carriers results in a 25% chance of producing offspring with the cocoa coat color. Since the mutation is specific to the French Bulldog and its genetic interaction with other coat color genes like the B locus (TYRP1 gene) remains poorly understood, it is important for breeders to test breeding pairs to avoid the unintentional breeding of affected puppies and manage the propagation of this trait responsibly. The current genetic tests can reliably identify carriers and dogs affected by the mutation, helping breeders make informed decisions to maintain healthy and diverse genetic lines.