Feline long hair

Hair length in cats is associated with the FGF5 gene. In total, 5 different variants of the FGF5 gene (M1, M2, M3, M4 and M5) have been detected to be associated with long hair in different cat breeds. All these variants show autosomal recessive inheritance. Cats that do not carry any variant of this gene (genotype N/N) have short hair.

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M1

The M1 variant (ins356T) is unique to the Ragdoll breed.

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M2

The M2 variant (c.406C > T) was discovered in Norwegian Forest Cats.

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M3

The M3 variant (c.del474T) is unique to the Ragdoll and Maine Coon breeds.

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M4

The M4 variant (c.475A > C) is the most common variant found in most long-haired cat breeds.

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M5 (Genomia does not currently test for M5)

The M5 variant (c.577G>A) is specific to Maine Coon cats.

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Shorthaired cats carry the N/N genotype or carry 1 copy of the variant gene (heterozygous genotypes N/M1, N/M2, N/M3, N/M4, N/M5). Short-haired individuals carrying 1 copy of the variant gene can produce long-haired offspring with appropriate crossbreeding (mating with another heterozygote, compound heterozygote or recessive homozygote).

The expression of long-hair may be due to the presence of two copies of the variant FGF5 gene. The individual (recessive homozygote) carries the genotype M1/M1, M2/M2, M3/M3, M4/M4 or M5/M5.

In addition, long hair may be present in a compound heterozygote, an individual whose genotype consists of two distinct variants of the FGF5 gene (M1/M3, M1/M4, M2/M4, M3/M4, M3/M5, M4/M5). Theoretically, it is also expressed in M1/M2, M1/M5, M2/M3, M2/M5 combinations if they are crosses of different breeds.

Recessive homozygotes and compound heterozygotes when mated with other long-haired cats always give long-haired offspring.

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Reference:

Drögemüller C, Rüfenacht S, Wichert B, Leeb T (2007) Mutations within the FGF5 gene are associated with hair length in cats. Anim Genet 38(3):218–221. [PubMed: 17433015]

Kehler JS, David VA, Schäffer AA, Bajema K, Eizirik E, Ryugo DK, Hannah SS, O'Brien SJ, MenottiRaymond M (2007) Four independent mutations in the feline fibroblast growth factor 5 gene determine the long-haired phenotype in domestic cats. J Hered 98(6):555–566. [PubMed: 17767004]

Shaffer, Griffin D., et al. "Identification of a novel missense mutation in the fibroblast growth factor 5 gene associated with longhair in the Maine Coon Cat." Human Genetics 140.11 (2021): 1517-1523.