Dominant White and White Spotting Cat (W-locus, S-locus, Salmiak & Gloving, KIT gene mutations)

Dominant White and White Spotting Cat (W-locus, S-locus, Salmiak & Gloving, KIT gene mutations)

In cats, the gene for the protein ‘v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homolog’ (KIT) plays a significant role in the body’s development. Several different dominant mutations to this gene impede the travel of pigment-producing cells across the developing skin, resulting in areas of white, unpigmented fur. For this reason, KIT is also known as the White Locus (W-locus) or Spotting Locus (S-Locus). Previously, it was thought that W-locus and S-locus were located on different genes but recently is has been discovered that both mutations are located in the KIT gene. They have been combined in a single locus (W-locus) as different alleles. Other genes that influence the pattern of White Spotting are still unknown. Additionally, not all white spots or patterns result from the KIT-gene as other genes can also have mutations that result in depigmentation phenotypes. Lastly albino cats are not related to white spotting or dominant white. Albino is a different mutation, in another gene (C-locus).

There are several mutations in the KIT gene that lead to white pattern phenotypes. All variants are related with pigment loss and therefore show a white pattern, but the pattern differs from each variant.

Dominant White or Full White (W or DW)

Animals with a Dominant White (W or DW) allele, result in an all-white phenotype and blue eyes. This phenotype is dominant over all other variants. As KIT is involved in several different phases of development, including the ears, cats with one or especially two copies of the DW allele often have hearing problems, and may be entirely deaf. A combination of W-alleles has also a higher risk of hearing defects.

White Spotting (Ws)

The White Spotting (Ws) allele, results in white spots over parts of the cat’s body, typically concentrated around the belly. White spotting is autosomal dominant over the wild type, but not dominant over the dominant white variant. Homozygote Ws-cats have the same phenotype as homozygotes, although sometimes it is believed that they have more white. Other genes that influence the exact pattern of Ws are still unknown. Therefore, patterns can vary wildly, especially when other modifying genes are present.

Gloving (G or Wg)

Gloving is a white spotting pattern responsible for the characteristic white paws of the Birman cat breed, where the trait is almost fixed in the population. It is an autosomal recessive trait, meaning that a cat must have two copies of the gloving allele to show gloving. The allele has also been found at a very low level in other breeds which lack white paws, indicating that the Birman breed must also have other variants which influence the Gloving phenotype which do not (always) occur in combination with these alleles in other breeds.

Salmiak

Recently discovered in Finland (2024), The salmiak allele (Wsal) is a rare recessive allele. A cat needs two copies to show the salmiak coat pattern. The coat of a Salmiak cat is quite unique and striking. It is characterized by a gradient, where the fur is predominantly the base colour at the roots and gradually transitions to white at the tips. This creates a “frosted” or “salted” appearance. It can look like a tuxedo, with white hair below the chin and front, and more gradation as you go further from the front to the back.

Inheritance Dominant White and White Spotting

The KIT-gene has three variants (alleles). The DW allele is dominant over the alleles Ws and N (Normal); allele Ws is dominant over allele N.

Inheritance Gloving

Inheritance Salmiak

Additional information

It is important to know that not all KIT mutations have been detected yet. Research is still ongoing and in time, hopefully other mutations will be found that can explain other whitening patterns in specific breeds.

Relevant tests

• K303
• K406
• K509