Researchers have identified a previously unknown coat color in domestic cats named salmiak or salty liquorice. It is distinguished by a striking black-to-white gradient on individual hairs or a salt-and-pepper coat pattern. This discovery signals a significant development in the field of feline genetics. It also challenges prior understanding of coat color inheritance.
The Salmiak Cats: This New Cat Color is Linked to Rare Genetic Deletion and Reveals the Hidden Role of Noncoding DNA in Fur Coloration
Background
Domestic cats technically come in two colors. These are black and orange. All other variants are a combination of these two, a dilution of these two due to the dilution gene, or both. Hence, when a salt-and-pepper coat pattern appears, scientists assumed that this is a new expression of the dilution gene and is associated with already known pigmentation genes.
These salt-and-pepper cats are now termed as salty liquorice or salmiak cats. The color pattern was first spotted in 2007. It was later brought to the attention of feline researchers headed by feline geneticist Heidi Anderson in 2019. The team has since been figuring out exactly what causes the expression of this cat coat color and pattern. They finally figured it out.
Salmiak cats display fur that begins black at the root and fades to white at the tip. This results in a salt-and-pepper appearance. The team of Anderson tested 4 of these cats for known color-coat genes and mutations. None of the known mutations were present. 2 salmiak cats then underwent whole-genome sequencing. A wider cat population testing followed.
Findings
The whole-genome sequencing of two salmiak cats uncovered a 95-kilobase deletion located about 65 kilobases downstream of the KIT gene. The KIT gene is well-documented in its involvement in pigmentation traits. This new variant is found not in the gene itself but in a nearby noncoding regulatory region. A population testing was done to confirm this.
Analyzed DNA from 180 domestic cats along with 3 salmiak cats using PCR genotyping showed a perfect match between the homozygous state of the deletion and the presence of the salmiak coat. This led researchers to designate the newly discovered variant as wsal—a novel recessive allele at the KIT locus. The salmiak mutation is essentially a recessive trait.
The aforementioned means that a cat must inherit the mutation from both parents in order to exhibit the unique fur pattern. Heterozygous carriers do not display any visible traits. This renders the mutation more difficult to trace in feline populations without genetic testing. The following is a summary of the important findings by Anderson and her team:
• Novel Recessive Allele: The ~95 kb deletion is a recessive mutation—cats need two copies or wt/wt to display the salmiak coat.
• Distinct From Known KIT Variants: This variant is unique and not found in domestic cats with other white-spotting patterns.
• Genotype–Phenotype Correlation: Every homozygous cat displayed the salmiak trait. This essentially confirms a causative link.
It is important to underscore the fact that the 95-kilobase deletion impacts gene regulation rather than altering the KIT protein itself. Specifically, because it removes regulatory DNA, it changes where and when pigment cells deposit melanin along each hair shaft. This causes the characteristic salt-and-pepper or fade from dark at the root to white at the tip.
Implications
The discovery carries considerable implications for both science and cat breeding. It enhances the current understanding of how coat colors and patterns are influenced by noncoding regulatory DNA. This also offers an opportunity to intentionally preserve and propagate the rare salmiak trait through informed genetic selection and planning.
Results of the findings are published in the August 2024 issue of Animal Genetics. The researcher emphasizes how regulatory DNA regions, often overlooked in traditional genetic studies, can have significant phenotypic effects. The researchers believe that further investigation into similar noncoding mutations may unveil additional hidden patterns in domestic animals.
The salmiak discovery not only introduces a visually captivating coat type but also contributes to the growing body of knowledge regarding gene regulation and inheritance in domestic cats. The advancements in genetic tools are seen to produce more breakthrough discoveries in the future and reshape the understanding of animal diversity.
FURTHER READING AND REFERENCE
- Anderson, H., Salonen, M., Toivola, S., Blades, M., Lyons, L. A., Forman, O. P., Hytönen, M. K., and Lohi, H. 2024. “A New Finnish Flavor of Feline Coat Coloration, ‘Salmiak,’ is Associated with a 95‐kb Deletion Downstream of the KIT Gene.” Animal Genetics. 55(4): 676-680. DOI: 1111/age.13438