Polydactyl cat

Cats with this genetically inherited trait are most commonly found along the East Coast of North America (in the United States and Canada) and in South West England and Wales.

Some cases of polydactyly are caused by mutations in the ZRS, a genetic enhancer that regulates expression of the sonic hedgehog (SHH) gene in the limb.

[4] The condition seems to be most commonly found in cats along the East Coast of North America (in the United States and Canada)[5] and in Western England and Wales.

[5] Although there is some controversy over whether the most common variant of the trait originated as a mutation in New England or was brought there from Britain, there seems to be agreement that it spread widely as a result of cats carried on ships originating in Boston, Massachusetts, and the prevalence of polydactyly among the cat population of various ports correlates with the dates when they first established trade with Boston.

In the case of preaxial polydactyly of the Maine Coon cat (Hemingway mutant) a mutation of the cis-regulatory element ZRS (ZPA regulator sequence) is associated.

Normally SHH is expressed in an organiser region, called the zone of polarizing activity (ZPA) on the posterior limb side.

In the concrete preaxial form of the Hemingway (Hw) mutant the variation is induced by a single point mutation in a noncoding cis-regulatory element for SHH.

In an extensive phenotypic variation like this, one or more complete digits at each single limb are developed including nerves, blood vessels, muscles and ligaments.

The summarized small random changes on all layers build the raw material and the process steps for the generation of the plastic variation.