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Two independent research teams identified a 5-kilobase DNA deletion near the Arhgap36 gene as the likely cause of orange fur in domestic cats. The gene’s location on the X chromosome helps explain why orange coats and orange-black patchwork patterns differ between male and female cats.
Two independent research teams have identified a 5-kilobase DNA deletion near the Arhgap36 gene as the likely genetic cause of orange fur in domestic cats, resolving a question that had remained open for more than 60 years. The mutation is on the X chromosome, helping explain why orange coats and orange-black patterns appear differently in male and female cats.
One team, led by Stanford University geneticist Greg Barsh, found that skin cells associated with orange fur produced about 13 times as much Arhgap36 RNA as comparable cells from cats without orange hair. The researchers initially expected to find a change in the gene’s protein-coding sequence. Instead, they identified a deletion in a nearby, non-protein-coding region that appears to affect the gene’s activity.
In the team’s database of 188 cats, the deletion was present in all 145 orange cats examined. The sample also included six calico or tortoiseshell cats and 37 cats without orange fur. The researchers said the findings provide strong evidence that the deletion causes sex-linked orange coloration; the sample is evidence for the link, not a count of all orange cats.
A second team led by Kyushu University geneticist Hidehiro Toh also identified Arhgap36. Its findings indicate that increased activity of the gene suppresses genes involved in pigment production, shifting color from dark eumelanin toward the reddish-yellow pigment pheomelanin. Both studies were published in the journal Current Biology.
Why Orange Patterns Differ by Sex
The X-chromosome location helps account for a familiar pattern: most orange cats are male, while females with orange fur often have patches or marbling of orange alongside black. Male cats generally have one X chromosome, so a version carrying the orange mutation can affect their coat broadly. Female cats generally have two X chromosomes, one inherited from each parent.
In female mammals, cells typically switch off one of their two X chromosomes at random. In a cat with different versions of the relevant gene on its X chromosomes, some skin-cell populations can express the orange-associated version while others express the other version. This can produce the patchwork seen in tortoiseshell and calico coats. Calico cats also carry a separate white-spotting mutation that affects the distribution of pigment-producing cells.
The genetic result also puts limits on what can be concluded from orange cats’ popular reputation for being less intelligent. The source report says there is no scientific support for a link between this coat-color mutation and cognition, and reports no obvious negative effects on health or mental wellbeing tied to the mutation.
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A Longstanding Coat-Color Puzzle
Orange fur has been difficult to fit into ordinary explanations of cat coat-color inheritance. The X-linked pattern was suspected, but researchers had not pinpointed the genetic change responsible. The findings were first shared in preprint studies in 2024, according to the report, before the work appeared in Current Biology in 2025.
The studies connect the mutation to pigment activity rather than to a change in the protein-coding portion of Arhgap36. The reported deletion is in a non-protein-coding region, and the teams’ results point to altered gene expression in melanocytes, the cells that produce pigment. This distinction helps explain how a DNA change outside a protein-coding sequence can still affect visible fur color.
“It’s been a genetic mystery, a conundrum.”
— Greg Barsh, Stanford University geneticist, quoted by Science in 2024
Limits of the Genetic Evidence
The results provide strong evidence for the mutation’s role, but the reported database covered 188 cats, not every breed or population. The source material does not provide enough detail to assess how broadly the sample represents cats worldwide, or whether other genetic factors affect the exact shade and distribution of orange fur.
The work also does not support conclusions about behavior or intelligence based on coat color. While the report says no obvious health or mental-wellbeing consequences have been linked to the mutation, it does not describe a dedicated long-term health study of orange cats. The precise effects of Arhgap36 in other tissues, beyond the pigment cells discussed in the research, are not established here.
Further Work on Cat Pigmentation
The two papers establish a genetic explanation for orange fur and a framework for understanding sex-linked coat patterns. Further research could test the finding across larger and more varied cat populations and clarify how Arhgap36 changes pigment-related gene activity in melanocytes.
No additional study or follow-up date is specified in the source material. For now, the key confirmed development is the publication of two independent studies in Current Biology, with the teams identifying the same X-linked deletion near Arhgap36 as the likely basis of orange coloration.
Key Questions
What genetic change is linked to orange cat fur?
Researchers identified a 5-kilobase deletion near the Arhgap36 gene. The deletion is in a non-protein-coding region and is associated with increased Arhgap36 activity in skin cells that produce orange fur.
Why are most orange cats male?
The mutation is on the X chromosome. Male cats generally have one X chromosome, while females generally have two; random X-chromosome inactivation in female cells can create patches of different coat colors.
Why can female cats be calico or tortoiseshell?
In females with different relevant versions on their two X chromosomes, groups of skin cells can express different versions as one X chromosome is switched off in each cell. That can produce orange-and-black patches or marbling. Calico coats also involve a separate white-spotting mutation.
Does the orange-fur mutation affect a cat’s intelligence?
The source report says there is no scientific evidence that the mutation is linked to intelligence. The familiar claim about orange cats being less bright is anecdotal, not a finding of these studies.
Source: hn
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