Amber coat colour in Norwegian Forest Cats

In Norwegian Forest Cats, a unique gene variant in MCR 1-gene (E-locus) has been found that results in kittens that are born with black/brown or blue/apricot colour. The same gene variant of E-locus (Extension), the substitution of Asp for Asn in MCR receptor, is also known in other mammals, for example in red-haired humans or in horses (chestnut colour). Among the cats, just the Norwegian Forest Cats are the only carries of this mutation.

As the kittens mature, the black/blue strips gradually turn to yellow and golden coloration. The original black or blue coat colour remains only on the tail tip. The coat colour can develop during the whole period of the cat physical development - by three years of age. The intensity of amber coloration in Norwegian Forest Cats varies. Some cats have lighter and some darker colour. Special features of these cats are the slate-grey coloured paw pads and light grey strips on the feet.

The amber coat colour (amber variant in MCR1 gene - is marked as allele e) is inherited autosomal recessively; it is expressed only in homozygous cats, an individual with both amber alleles (e/e).

Example of amber color:

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Amber genotypes - summary:

• E/E: no copy of a gene variant for amber coloration is present
• E/e: one copy of a gene variant for Amber coloration is present (if bred with another amber carrier, 25% of the kittens will be Amber, in the absence of Orange-gene)
• e/e: two copies of a gene variant for amber coloration are present (if two homozygous individuals are bred, all kittens will be Amber coloured, in the absence of Orange-gene)

In cats, locus O (Orange) responsible for red or orange colour have been described; the traits of O-locus are X-linked inherited (inheritance X-linked to female chromosome); Genomia does not perform tests for the O-locus. In the presence of at least one O-allele (orange) and the genotype d/d, the full red colour becomes diluted to light cream.

The amber coloration is subordinate to the dominant O-locus:

• Amber is expressed only in individuals with e/e genotype, who are not carriers of dominant orange; cats and tom-cats with genotype e/e will have amber colour.
• Tom-cats with the orange gene will have red colour caused by the O-locus.
• Cats with one copy of the orange gene will be amber or tortoise coloured.
• Cats with two copies of the orange gene will have red colour caused by the O-locus.

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References:

M. Peterschmitt at al.: Mutation in the melanocortin 1 receptor is associated with amber
colour in the Norwegian Forest Cat