In a collaborative study led by Christopher B. Kaelin of the HudsonAlpha Institute of Biotechnology and Stanford University, published in the most recent issue of Science Magazine, researchers identified a gene called Taqpep that determines whether the pattern of a cat’s coat will form blotchy spots or sleek mackerel stripes.
The researchers discovered that the gene has a different but analogous effect on cheetahs. The gene variant that produces thin stripes on a domestic cat gives a cheetah its distinctive spots. The blotchy gene variant will result in a cheetah with thick black stripes along its back.
A tabby cat’s hairs are not one uniform color, but have bands of lighter and darker pigment along each strand. Taqpep affects whether the bands of pigment are wide or narrow. A mackerel tabby – one with stripes – has more hairs with wide bands of light pigment. The common mutation to Taqpep that causes blotched tabbies results in more hairs with wide bands of dark pigment.
The discovery of this gene helps to explain the molecular process that produces these variations in cat patterns. According to one of the study’s researchers, Stephen O’Brien, this is a new development: “What this is, is the first connection of a gene involved in pattern formation in cats to their molecular status.” The study demonstrates that Taqpep determines the rate at which pigment molecules are activated, rather than the type or quantity of pigment molecules.
The researchers found that both cats and cheetahs develop their distinctive markings about seven weeks into gestation. This is the exact point at which a fetal cat’s hair follicles are developed enough to start pushing hair past the skin. Therefore, a cat will begin to express its coat pattern long before it is born, with its genes determining a consistent coat pattern throughout the cat’s life.
Historical records suggest that the mutation to Taqpep that causes the blotchy tabby pattern is relatively new in genetic terms. According to the Science article, most artistic depictions of tabby cats in the Middle Ages showed a mackerel striped pattern. However, in 1758, the geneticist Linnaeus described the blotchy pattern as characteristic. While humans have been living alongside domestic cats for several thousand years, it seems that blotchy tabbies have only become common in the past 300 or 400 years.
The study did not draw any conclusions about why genetic variations in coat pattern occur, but the researchers provide several hypotheses. Coat patterns provide camouflage to both domestic cats and cheetahs, increasing their chances of survival. An attractive coat pattern sometimes also encourages humans to care for a domestic cat.
But O’Brien suggests another possible application for his study’s findings about the genetics of pigmentation. In an interview with NPR, O’Brien says there might be a connection between the pattern of an animal’s coat and its resistance to disease, and that the next step might be to investigate the correlation between Taqpep mutations and immunity. This research might have implications beyond the family pet as well. As O’Brien states, “It’s curious that they have this kind of variation not only in cats, but we also have this kind of variation even in humans.” If O’Brien is correct, this genetic mutation might be more than cosmetic, and it might help to prevent disease in humans as well as in cats.