Hr Locus (FOXI3 Hairless Gene Test, Mexican Hairless, Peruvian Hairless and Chinese Crested Type)

General Information: The Hr Locus (Hr) mutation within the FOXI3 gene leads to canine ectodermal dysplasia, characterized by hairlessness and missing or abnormally shaped teeth. Affected dogs, which include breeds like the Chinese Crested, Peruvian Hairless, and Mexican Xoloitzcuintle, exhibit varying degrees of hairlessness, typically with tufts of hair on their head, feet, and tail. These dogs often have long, brittle toenails and may suffer from severe dental abnormalities, with many teeth missing or malformed. This condition is dominantly inherited, meaning that a dog only needs one copy of the mutated gene to express the hairless trait. However, dogs with two copies of the mutation typically do not survive to birth, resulting in reduced litter sizes.

Gene / Testing Information: Genetic testing for the FOXI3 gene mutation at the Hr Locus (Hr) is crucial for determining whether a dog is a carrier of the hairless trait. This trait is inherited in an autosomal semi-dominant manner, meaning that a dog with one copy of the mutation will exhibit hairlessness, while two copies are embryonically lethal. When breeding two hairless dogs, each puppy has a 25% chance of inheriting two copies of the gene and not surviving, a 50% chance of inheriting one copy and being hairless, and a 25% chance of inheriting no copies and being fully coated. Reliable genetic testing is essential for responsible breeding practices, ensuring that breeders can make informed decisions to avoid the risk of producing affected puppies and manage the desired traits within the breeding lines.