Stanford and Kyushu Scientists Identify Gene Mutation Behind Orange Cats

Two independent research teams have pinpointed the genetic cause of orange fur in domestic cats. A study led by Christopher Kaelin at Stanford University in the United States and a parallel study by Hidehiro Toh at Kyushu University in Japan, both published in *Current Biology*, found a roughly 5,000‑base‑pair deletion in a regulatory region of the X‑linked gene **ARHGAP36**. The deletion acts as a molecular switch, triggering abnormal activation of the gene in melanocytes, which boosts production of the pigment feomelanin and suppresses eumelanin, resulting in the characteristic orange coat.

The mutation also explains why orange cats are overwhelmingly male: because the trait is X‑linked, a single copy of the altered X chromosome in males (XY) produces the orange phenotype, while females (XX) would need the mutation on both X chromosomes to display the color fully. The findings resolve a century‑old mystery about the inheritance and molecular basis of the orange coat in felines.