Her Dresses and Colours | siberien-chat.com

Coats and Colours of the Siberian Cat
(Felis catus)

Genetic Origins and Phenotypic Diversity

The history of the modern Siberian cat has its origins in the reconstitution of the Russian cat population after the Second World War. Hundreds of cats were introduced into the country to compensate for major losses, naturally causing mating between these exogenous individuals and the native populations, particularly those in the forest regions of Siberia. This cross-breeding dynamic has generated a hardy feline population, characterised by great morphological robustness and high phenotypic variability. The Siberian cat is thus a natural breed whose polymorphous genetic heritage is the combined result of natural selection and selection directed by supervised breeding programmes.

There are currently two types of Siberian cat: the Classic Siberian and the Neva Masquerade (or Newskaja Maskaradnaja), the latter being a colour variant of the former.

The first appearances of the color point gene in Siberian cats historically coincide with those of traditional coats (brown tabby, silver tabby, red tabby, etc.). At that time, an external genetic contribution, notably via the Persian or the Burmese Sacred, seems unlikely. The first colour point Persian was not imported from Russia until 1991, and the Sacred of Burma population had been reduced to a single breeding pair (Orloff and Xénia de Kaabaa) by the end of the war, as recorded in the Livre Officiel des Origines Félines (LOOF).

However, recent crosses, whether natural or the result of targeted breeding programmes, have enriched the Siberian gene pool. These contributions have led to the appearance of new loci responsible for phenotypes such as blue eyes, colour point patterns and white expression.

It is because of this genetic evolution that the Neva Masquerade is now recognised as a colour in its own right within the Siberian breed. Its name refers to the Neva, the river bordering the city of St Petersburg, where the first specimens were observed.

Two recognisable phenotypes: Classique and Neva Masquerade

The Siberian cat has two distinct but genetically compatible phenotypes:

Classic Siberian: A wide variety of colours and patterns, excluding alleles not permitted by the breed standards (see "genetic exclusions" section). Eye colour varies from green to copper.

Neva Masquerade: This is a colour variation of the Siberian, whose uniqueness lies in the homozygous expression of the cs/cs locus, responsible for the Color Point pattern. Expression of this locus results in heat-sensitive pigmentation limited to the extremities of the body (ears, tail, face, limbs), giving these cats their "masked" appearance. The eyes are invariably blue.

Crosses between individuals with both phenotypes are authorised. As the cs gene is recessive, heterozygous carriers (cs/c+) do not present the pointed phenotype but may transmit it. In other words, the kittens resulting from these unions may or may not inherit the color point gene, and present one or other of the two phenotypes, while carrying the genetic heritage of both lines.

Genetic Mechanisms of Dress Inheritability

From a genetic point of view :

The gene responsible for the color point phenotype is a mutation in the TYR gene, coding for tyrosinase, a key enzyme in melanin synthesis. This mutation, transmitted in an autosomal recessive fashion (cs/cs), causes heat-sensitive pigmentation: only the coldest parts of the body (extremities) are coloured, while the central areas remain light. The blue eyes of Neva Masquerade are also due to a lack of melanisation of the iris associated with this mutation. The gene is silent in heterozygotes (C/cs), who retain a classic phenotype despite being carriers.

The coat diversity observed in the Siberian is governed by a complex interaction of several genetic loci, including :

Locus A (Agouti): determines the presence (A) or absence (a) of the tabby pattern (agouti vs non-agouti).

Locus B (Brown Series): regulates eumelanic pigmentation (dark, chocolate, cinnamon).

Locus D (Dilution): modifies pigment intensity (e.g. black → blue).

Locus Cs (Color point): thermosensitive mutation of tyrosinase resulting in the pointed phenotype.

W and S locus: responsible for white patterns (complete dominance for W, incomplete for S).

The expression of the colour point phenotype is directly influenced by peripheral body temperature, with colder areas being more heavily pigmented.

Official codification of non-accepted dresses

In an attempt to broaden the phenotypic palette, some breeders have introduced illegal crosses with other breeds. Although these practices have led to the appearance of exotic colours (chocolate, lilac, etc.), they are formally banned by standardisation bodies.

These alleles are generally the result of unauthorised crosses with breeds such as the British Shorthair, Persian or Oriental. Individuals carrying these genes are excluded from official breeding and considered not to conform to standards.

These hybrids not only run the risk of altering the Siberian's hardiness, but also of introducing genetic pathologies hitherto absent from the breed.

In accordance with the Livre Officiel des Origines Félines (LOOF), the following colours are therefore formally prohibited as they do not come from the original genetic heritage of the Siberian breed :