Discovery of Four New FGF5 Variants Causing Long Hair in the Dog

The long hair phenotype of the dog is ascribed to variants in the fibroblast growth factor 5 (<i>FGF5</i>) gene. Currently, there are five variant alleles known, Lh1 through Lh5, with any combination of these alleles resulting in a long-haired phenotype in dogs. Recently, genotyping of several long-haired dogs for the known Lh1-Lh5 variants yielded unexpected results as these dogs contained no or only one variant in the <i>FGF5</i> gene known to result in the long-hair phenotype. Analysis of the coding region for the <i>FGF5</i> gene identified four novel variants associated with the long-haired phenotype. One dog of mixed ancestry had an insertion of G very similar to and near to the long-hair variant Lh4, NC_006614.4: g.37352832insCC. A group of 24 Tibetan Mastiffs showed the Lh1 variant NC_006614.4:g.37372096C>A in 11 dogs only, and no other known Lh variant. Within the coding frame of the <i>FGF5</i> gene, three unknown variants were discovered that were predicted to have a phenotypic effect. These new variants were inherited in a Mendelian fashion and, in combination with one of the known <i>FGF5</i> alleles, likely predict the long-hair phenotype. Lastly, eight of the 24 Tibetan Mastiff dogs carried three <i>FGF5</i> variants.