"The long and the short of it: evidence that FGF5 is a major determinant of canine 'hair-itability'"

This study focused on determining if a mutation in the FGF5 gene is responsible for the recessive long-haired phenotype in dogs.

Studies have shown that hair length in dogs is determined by at least two major autosomal genes. At one of these points, referred to as L, the dominant allele causes short hair, while the recessive allele causes longer hair. At the second location, the allele for long hair is dominant to the allele for short hair. This gene is dominantly epistatic (a genotype at one location affects the expression of the genotype at another location).

Most dog breed standards allow only one hair length, but breeds allow various hair lengths because long hair is thought to be a recessive phenotype. In Pembroke Welsh corgis, however, long hair does not conform to the breed standard. These long-haired corgis, called fluffies, do not fit with the original herding function of corgis because mud and water would get stuck in their long hair, preventing proper herd work.

The only known mutant gene that causes excessively long hair the one which encodes fibroblast growth factor 5 (FGF5). This gene is supposed to allow the catagen (regression) phase to occur after the anagen (growth) phase. In mice, if FGF5 is knocked out, there is an extended anagen phase, causing long hair length. Because the angora phenotype in mice is similar to the L locus in dogs, normal and fluffy corgis were studied to determine if the FGF5 mutation causes excessive long hair in dogs, as well. Other purebred dogs were also studied.

DNA samples were extracted from Pembroke Welsh corgis, collies, Border collies, German shepherds, miniature long-haired and smooth dachshunds, Thai ridgebacks, pugs, Pomeranians, basenjis, bulldogs, golden retrievers, and Labrador retrievers.

The FGF5 sequence was obtained, revealing that it has three exons. The sequence of exon 1 revealed two differences between the sequence of a normal corgi and that of a fluffy.

Actual hair length, in addition to the inherited allele, is also affected by other modifier genes and environmental factors. Despite breeding against long hair, the recessive long hair allele has persisted in Pembroke Welsh corgis.

 

Housley, D. J. E., and P. J. Venta. "The long and the short of It: evidence that FGF5 Is a major determinant of canine 'hair'-itability." Animal Genetics 37.4 (2006): 309-15. Wiley Online Library. Web. 16 Nov. 2015.