Test Detail

Inherited phenotypic trait that determines the long or semi-long coat of the cat. It is not a disease: it depends on loss-of-function variants in the FGF5 gene, which regulate the hair follicle cycle. Short hair is dominant and long hair recessive, so that a long-haired cat is homozygous for one variant or a compound heterozygote for two different variants. Five variants (M1-M5) associated with the phenotype are known in different breeds.

M1-M5 alleles described in different long-haired breeds. M4 is the most widespread and also appears in heterozygosity in some short-haired breeds (e.g. British Shorthair and Devon Rex; Kehler et al., 2007). Allele frequencies per breed are variable and in many breeds are not published: limited data.

It does not produce clinical signs: it is a coat trait.\n- Long or semi-long coat, with variation in length and texture according to breed and genotype\n- Homogeneous length or in different layers depending on the variants present\n- There is no pain, lesion or associated systemic alteration

The long-haired phenotype was mapped in 2007 to a region of chromosome B1 containing the FGF5 gene (Kehler et al., 2007). That same year, Drögemüller et al. identified mutations in FGF5 associated with hair length in the cat. Kehler et al. (2007) described four independent mutations (M1-M4) in different breeds, and Shaffer et al. (2021) added a fifth variant (M5) specific to the Maine Coon. The FGF5 DNA test was incorporated into feline panels as a phenotype test, not a health test.

- Test breeding animals of long-haired breeds or with unexpected long-haired cases.\n- Remember that long hair requires two loss-of-function alleles: homozygosity for one variant or compound heterozygosity (two different variants).\n- Two short-haired carrier cats can have long-haired offspring.\n- Choose the test that includes the relevant variants for the breed (in the Maine Coon, include M5).\n- It is a phenotype test: it should not be used as a health screen.

The FGF5 test predicts hair length, not health. There are at least five variants (M1-M5): a long-haired cat may be homozygous for one or a compound heterozygote for two. M5 is specific to the Maine Coon and may not be detected in panels that only include M1-M4. The phenotype is influenced by age, sex and other genes, so a result discordant with the phenotype should be interpreted with caution.

1. Drögemüller C, Rüfenacht S, Wichert B, et al. Mutations within the FGF5 gene are associated with hair length in cats. Anim Genet. 2007;38(3):218-221. PMID: 17433015.
2. 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. PMID: 17767004.
3. Shaffer GD, Ballif BC, Meurs KM, et al. Identification of a novel missense mutation in the fibroblast growth factor 5 gene associated with longhair in the Maine Coon Cat. Hum Genet. 2021;140(11):1517-1523. PMID: 34599367.
4. OMIA:000439-9685. Hair, long in Felis catus. https://omia.org/OMIA000439/9685/