![]() Just like that, a dark hair falls out and is replaced with – a new dark hair. ![]() A full grown cheetah has the same number of spots it did as a juvenile. The color stamp persists even as the constituent cells divide, and in this way, the pattern of stripes on a kitten remains in the cat it becomes. In a cat fetus, a follicle is developmentally destined to give rise to a hair that’s either light or dark, called its “pattern element identity.” Then a bath of local hormone signals sets the color hair-by-hair. From this molecular tango arose Jackie’s stripes.Ī hair follicle arises from stem cells, which divide and are pushed upward as they specialize, accumulating keratin protein and melanin pigments. An activator coloring a cell triggers an inhibitor that diffuses away and suppresses pigment deposition in neighboring cells. His “reaction-diffusion mechanism” envisioned activator and inhibitor molecules overseeing deposition of pigments before birth templating coat color patterns. A hypothesis explaining how this complex coloring may arise dates from the early 1950s from a seemingly unlikely source – Alan Turing of computer science fame.Īlso a theoretical biologist, Turing posited that patterns such as the coat colors of large cats could arise from molecules that turn each other on and off as they move through a developing body’s tissues at different rates. These are called periodic color patterns. ![]() The colors of cats are more intricate than the hues of humanity, with striations and spots of light and dark creating the distinctive coat patterns of ocelots, jaguars, cheetahs, and of course the leopard’s spots of fable fame. The overall color reflects the proportions of black−brown eumelanin and red−yellow pheomelanin. Humans of different skin colors have about the same number of melanocytes, but the cells produce differing amounts of the two variations of melanin pigment. Local-acting hormones determine the output of pigments from cells called melanocytes, but the number of melanocytes tends to be the same in all individuals of a species. In mammals the situation is more complex. It’s a little like following the directions in a paint-by-numbers kit and watching an image emerge as small areas of color become confluent. The work revealed a novel mechanism behind the origin of stripes, like Jackie’s in the photograph.Ĭolor is easier to study in fish, in which individual pigment cells denote a specific color, and the organization of the cells forms patterns. ![]() To trace the origins of the common striped coat pattern, the team analyzed gene expression in single skin cells from fetuses collected from feral cats in trap-neuter-release programs being spayed – half of such females are pregnant. However, the biology underlying mammalian color pattern has long been a mystery, one in which we have now gained new insight using domestic cats,” said Barsh, who is editor-in-chief of PLoS Genetics. “The genes that control simple color variation, like albinism or melanism, are the same in all mammals for the most part. Their findings appear in Nature Communications. Now Christopher Kaelin, Kelly McGowan, and Gregory Barsh, from the HudsonAlpha Institute for Biotechnology, have discovered how the tabby cat got its stripes: from a signal in the fetus. In 1902’s Just So Stories, Rudyard Kipling famously explained how the leopard got his spots in what would today be deemed an extremely racist fable.
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