Scientists Uncover Genetic Basis of Orange Cat Fur After Over a Century

Two independent studies identify a mutation in the ARHGAP36 gene as the cause of orange coloring in cats, solving a 110-year-old genetic mystery.

Researchers from Stanford University and Kyushu University pinpointed a mutation in the ARHGAP36 gene, located on the X chromosome, as the cause of orange fur in cats.
The mutation leads to overexpression of the gene in pigment-producing cells, resulting in the production of yellowish-red pheomelanin pigments instead of darker eumelanin pigments.
The discovery confirms a 1912 hypothesis linking orange coat color inheritance to the X chromosome, explaining why most orange cats are male and tortoiseshell cats are predominantly female.
The studies reveal that in female cats, random X chromosome inactivation creates the patchwork patterns seen in calico and tortoiseshell coats.
This breakthrough also highlights a previously unknown role of the ARHGAP36 gene in pigmentation, offering new insights into feline genetics and evolutionary biology.