W locus (Dominant white and White spotting) – Cat Coat color
The cat displays several distinctive white pigmentation phenotypes that have been under selection by cat fanciers: Dominant White, uniform white coat, often accompanied by blue irises and deafness, white spotting (or piebald): variable distribution of white areas on the body, and gloving: white pigmentation restricted to the paws. Albinism, the complete absence of pigment, is known to be caused by a distinct locus from White, called “C“.
The dominant white gene is associated with developmental defects where melanocytes fail to migrate to the skin during embryologic development. The number of melanocytes are greatly reduced, but not always absent (hence temporary smudges of colour on the heads of some kittens). This can result in one or both blue eyes and in degenerative changes of the ear resulting in partial or total deafness.
Dominant white (W) masks other colour and pattern alleles hence solid white cats may genetically be solid or patterned cats in any colour. The underlying colour will show up in any offspring that don’t inherit the Dominant white allele.
The white spotting gene (S) creates white markings on a solid or patterned cat. The white spotting gene is variable in expression from white locket (face/ paws/legs/white stomach) through to solid white covering 40-60 % of the body to high grade spotting (van pattern) where most of the body is white, other than the head and tail that can resemble dominantno white, however it is rarely associated with deafness. Homozygosity vs heterozygosity for the ws allele appears to have an influence on the degree of white pigmentation.
A separate recessive gene (G) has been identified for Birman white gloving. There are hypothetical genes for other white mitted patterns and for the York Chocolate white pattern. There are believed to be genes, as yet unidentified, for the white throat locket and white brisket spots.
David, V.A., Menotti-Raymond, M., Wallace, A.C., Roelke, M., Kehler, J., Leighty, R., Eizirik, E., Hannah, S.S., Nelson, G., Schäffer, A.A., et al. (2014). Endogenous retrovirus insertion in the KIT oncogene determines white and white spotting in domestic cats. G3 (Bethesda) 4, 1881–1891.