Summary: After decades of mystery, researchers have finally identified the gene behind orange fur in domestic cats: a deletion mutation in the X-linked gene ARHGAP36. This mutation increases gene activity in pigment-producing skin cells, shifting fur color toward orange by altering pigment production pathways.
The discovery explains why most orange cats are male and why females with one copy of the gene develop calico or tortoiseshell coats. The study also suggests the orange gene may influence more than just coat color, with possible effects on brain and hormonal activity.
Key Facts:
Orange Gene Identified: A deletion in ARHGAP36 drives orange fur by boosting gene activity in melanocytes.
Sex-Linked Expression: The gene is on the X chromosome, explaining why most orange cats are male.
Beyond Color: The mutation may affect other body systems due to ARHGAP36‘s broader roles.
Source: Kyushu University
From Tama, Japan’s most famous stationmaster calico cat, to the lasagna-loving, ginger Garfield, cats with orange fur are both cultural icons and beloved pets. But their distinctive color comes with a genetic twist—most orange tabbies are male, while calicos and tortoiseshells are nearly always female.
The discovery explains why most orange cats are male and why females with one copy of the gene develop calico or tortoiseshell coats. The study also suggests the orange gene may influence more than just coat color, with possible effects on brain and hormonal activity.
Key Facts:
Orange Gene Identified: A deletion in ARHGAP36 drives orange fur by boosting gene activity in melanocytes.
Sex-Linked Expression: The gene is on the X chromosome, explaining why most orange cats are male.
Beyond Color: The mutation may affect other body systems due to ARHGAP36‘s broader roles.
Source: Kyushu University
From Tama, Japan’s most famous stationmaster calico cat, to the lasagna-loving, ginger Garfield, cats with orange fur are both cultural icons and beloved pets. But their distinctive color comes with a genetic twist—most orange tabbies are male, while calicos and tortoiseshells are nearly always female.
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00:00After decades of mystery, researchers have finally identified the gene behind orange
00:05fur in domestic cats, a deletion mutation in the X-linked gene RGAP36.
00:11This mutation increases gene activity in pigment-producing skin cells,
00:15shifting for color toward orange by altering pigment production pathways.
00:20Orange gene identified, a deletion in RGAP36 drives orange fur by boosting gene activity
00:26in melanocytes.
00:27Sex-linked expression, the fact that the gene is located on the X chromosome explains why
00:33the majority of orange cats are male.
00:36Beyond color, the mutation may affect other body systems due to RGAP36 as broader roles.
00:42Source, Kyushu University, the findings are confirmed by a second independent study by researchers
00:48at Stanford University, U.S., with both papers publishing simultaneously in Current Biology
00:54on May 15, 2025.
00:57Identifying the gene has been a long-time dream, so it's a joy to have finally cracked it,
01:02says Professor Hiroyuki Sasaki, lead author of the study, self-proclaimed cat lover, and
01:08geneticist at Kyushu University's Medical Institute of Bioregulation and the Institute for Advanced
01:13Study.
01:14For over a century, scientists have suspected that the orange gene is located on the X chromosome.
01:20Male cats with only one X chromosome will have orange coats if they inherit the orange gene.
01:27Females with two X chromosomes need two copies of the gene to be fully orange, making them
01:33less common.
01:34If females inherit one orange and one black gene, they develop the patchy or mottled coats seen
01:40in calicos and tortoiseshells.
01:42According to Sasaki's explanation, these ginger and black patches form because, early in development,
01:49one X chromosome is randomly switched off in each cell.
01:52As cells divide, this creates areas with different active coat color genes, resulting in distinct
01:59patches.
02:00The effect is so visual that it has become the textbook example of X chromosome inactivation,
02:05even though the responsible gene was unknown.
02:09Armed with funding from a successful crowdfunding campaign, Sasaki therefore set out to find
02:14the elusive gene.
02:15His team analyzed DNA from 18 cats, 10 with orange fur and 8 without, and found that all
02:21orange cats shared a specific deletion in the RGAP36 gene, while the non-orange cats did
02:27not.
02:27This pattern held true in 49 additional cats, including samples from an international cat
02:33genome database.
02:34They also found that in mice, cats, and humans, the RGAP36 gene is chemically marked for silencing
02:41during X chromosome in NAC.