Long hair (FGF5 gene, Norwegian Forest Cat)

The distinctive long fur that covers the body, limbs and tail of cats such as the Norwegian forest cat has been associated with a single gene known as FGF5.

Definition

This trait refers to the genetic variant responsible for long hair on the body, legs and tail of cats. This variant is found in the FGF5 gene, which is involved in the regulation of hair growth in the hair follicle.

Genetic basis

A unique mutation has been described in the FGF5 gene that causes the long coat typical of Norwegian forest cats: c.406C>T (also known as M2 allele). The variant is recessive, therefore, long hair will be expressed in those cats that have two copies of the variant. Different variants have been identified in the FGF5 gene which, when combined with this variant in compound heterozygosis (one copy of each variant), could also generate a longer coat phenotype.

Other relevant information

The FGF5 gene is crucial for the regulation of the hair growth cycle. Mutations in this gene prolong the anagen phase (growth phase) of the hair cycle, resulting in longer hair. This is because FGF5 acts as a "switch" that normally stops hair growth at the end of the anagen phase. Without proper FGF5 function, hair continues to grow longer than normal.

Bibliography

Kehler JS, David VA, Schäffer AA, et al. Four independent mutations in the feline fibroblast growth factor 5 gene determine the long-haired phenotype in domestic cats. J Hered. 2007;98(6):555-566.