Two new studies identify the genetics behind orange house cats:
Now two papers, published concurrently on Thursday in Current Biology,reveal a remarkably unique genetic pathway that has never been seen in other felines—or any other mammals. With their colleagues, two separate groups at Stanford University and Kyushu University in Japan independently arrived at the same surprising conclusion: a tiny deletion in a cat’s X chromosome increased the activity of a gene called Arhgap36, which scientists had never previously associated with pigmentation. In this case, it appeared to be coaxing the cat’s melanin-producing cells to shift orange.
These findings close decades’ worth of investigations surrounding house cats with a ginger hue—a coat coloration that had “been recognized for more than a century [as] kind of an exception to the genetic rules that explain coloration in most mammals,” says Christopher Kaelin, a geneticist and lead author of the Stanford study.
That’s partly because what seemed to be causing orange fur in cats wasn’t so much an “orange gene” as it was an “orange mutation” in an unknown gene, Kaelin says.
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Orange and tortoiseshell cats’ tendency toward amusing, friendly and sometimes mischievous behavior is a running joke among cat owners, but there’s no scientific evidence linking coat colors and behavioral differences, Barsh says. Researchers aren’t yet sure if the mutation could play a role in this—it’s a question they’d like to ask next, however. “Because Arhgap36 is expressed not only in pigment cells but also in the brain and hormonal glands, an interesting possibility is that its altered expression causes changes in neuronal activity and even behavior,” Sasaki suggests.
See Gayoung Lee, This Strange Mutation Explains the Mystifying Color of Orange Cats (‘Your orange cat may host a never-before-seen genetic pathway for color pigmentation, according to new studies’), Scientific American, May 15, 2025.