Genetic basis - The curly coat phenotype in dogs is caused by a missense mutation in the KRT71 gene, specifically the R151W (Arginine to Tryptophan at position 151) variant. KRT71 encodes keratin 71, a type II keratin protein expressed in the inner root sheath of hair follicles, which is crucial for hair follicle shape and hair texture. This particular mutation alters the structure of keratin 71, leading to changes in hair shape that produce a curly or wavy coat. The mutation is inherited in an incomplete dominance manner: dogs with one copy of the R151W allele often show wavy coats, while those with two copies typically have curly coats.
Pathophysiology - The R151W variant disrupts the normal keratin filament formation in hair follicles, causing the hair shaft to curl due to altered follicle morphology. The shape of the hair shaft changes from a typical round to a more flattened or oval shape, which bends and twists the hair, producing curls. Coat curl intensity and appearance may also depend on other genetic factors, hair length, and texture.
Complications - No direct complications have been strongly associated with the R151W variant itself. However, keratin mutations in other species and some variants in dogs can be linked to follicular dysplasia or hair coat abnormalities. Generally, this variant is considered a cosmetic change affecting hair texture rather than a health concern.
Why This Matters to Breeders and Vets - Knowing a dog’s KRT71 R151W status helps breeders predict coat type outcomes and manage breeding programs to achieve desired coat aesthetics. For vets, awareness assists in understanding coat phenotypes and ruling out hair coat problems related to more serious skin or follicular issues. Genetic testing for this variant is commonly offered to breeders and helps maintain breed standards where curly or wavy coats are preferred.