Unraveling the genetic code behind cats' orange hue
Two independent research teams have finally figured out what makes cats orange. It turns out a special gene is responsible for the unique coloration of domestic cats, ending years of searching for the answer to this mystery.
The two research teams discovered that a missing segment of DNA in the non-coding part of a cat's genome causes them to have their distinctive orange coloration. “It's been a genetic mystery, a conundrum,” said Greg Barsh, a geneticist from Stanford University, in an interview with Science Alert.
What are the details of the Arhgap36 gene discovery?
Barsh and his colleagues found that the skin cells of cats with orange patches of fur express RNA from a gene called Arhgap36 13 times more than the skin cells of non-orange cats. Instead of a mutation in the protein-coding section, researchers identified a deletion (a gene mutation involving the loss of a DNA segment) in the preceding sequence that affects gene expression.
"The 5 kilobase deletion was present in every orange cat the researchers examined out of a database of 188 cats," noted the research team in their analysis. Their work is available online and is awaiting review on bioRxiv.
Does orange fur equal male cat?
The gene mutation is on the X chromosome, explaining the differences in coloration between male and female cats. Most orange cats are males, while females with orange fur often have patches of various colours. “These observations provide strong genetic and genomic evidence that the 5 kb deletion causes sex-linked orange coloration,” wrote Barsh and his team in their paper.
For thousands of years, people have wondered how a black and orange cat could be the parents of kittens with diverse colours. Males from this pairing are usually orange or black, while females can have calico or tortoiseshell colouring. The research confirmed that the mutation responsible for orange fur is located on the X chromosome, leading to differences in coloration between sexes.
Orange cats have a reputation for being less intelligent, but there is no scientific evidence linking fur colour to intelligence. The Arhgap36 gene is known to cause developmental issues in other animals, but in orange cats, it is over-expressed only in pigment cells.
