Posted on 12/11/2024 10:04:27 PM PST by Red Badger
After 60 years of searching, geneticists have finally identified the gene behind the marmalade coloration in domestic cats.
Two independent teams of researchers found any fiery-hued fuzz on our beloved clawed floofs is likely the result of a missing segment of DNA in a non-protein-coding part of the cat's genome.
"It's been a genetic mystery, a conundrum," Stanford University geneticist Greg Barsh told Sara Reardon at Science.
Barsh and his colleagues discovered cat skin cells from which orange fur sprouts express 13 times as much RNA from a gene called Arhgap36, compared with skin cells from cats with no orange hair.
Expecting to find the protein-coding section of the overproductive Arhgap36 gene had mutated, the researchers were surprised to find it was the sequence preceding it that instead contained a deletion, presumably affecting the rest of the gene's expression.
The 5 kilobase deletion was present in every orange cat the researchers examined out of a database of 188 cats, which included 145 orange, 6 calico/tortoishell, and 37 nonorange cats.
One finding didn't come as a surprise. As long predicted, the mutated gene is located on the cat's X chromosome, explaining why the orange color appears so differently between the sexes. Most orange cats are male, while most female cats with some orange fur end up with patchworks of different colors.
Calico Cat
"Taken together, these observations provide strong genetic and genomic evidence that the 5 kb deletion causes sex-linked orange," Barsh and team write in their paper.
Ever since humans first co-habitated with cats nearly 10,000 years ago, it's been a curiosity that a black cat and an orange cat can be parents to an unexpected array of kitten colors. Male kittens from this pairing are mostly either orange or black, as might be expected. But female kittens can have a calico's patchwork of black, orange and white, or a tortoiseshell's marbling of orange scattered through black fur.
A tortoiseshell cat. (Yosei G/Unsplash)
Both teams confirmed the mutation responsible for orange fur is on the X chromosome, which is why such clear differences in colored patterning can appear between the sexes.
Unlike males that end up with just one copy of this mutation on their solitary X chromosome, females end up with two copies, one on each the X's they receive from each parent.
Mammals randomly inactivate one of the two X chromosomes in each of their cells to avoid expressing an excess of the chromosome's products. This leaves female orange kitties with an active orange mutation in some of their developing skin-cell tissues, right next to neighboring cells in which the X chromosome with the mutated gene is deactivated.
On rare occasions that both X chromosomes carry the mutation, the female grows into furry fireball as ginger as any male.
Orange cats happen to have a hilarious reputation for not being the brightest of their species. Anecdotes aside, such links between kitty coloration and cognition are scientifically unsupported, with no obvious negative consequences from this mutation in health or mental wellbeing.
Arhgap36 is known to cause developmental problems in other animals when it is over- or under-functioning. But it seems that in orange cats, the gene is overexpressed only in developing and mature pigment cells called melanocytes.
"The difference between tortoiseshell and calico cats is the presence of an additional white spotting mutation in calico that affects the ability of developing melanocytes to survive as they migrate away from the neural crest, allowing melanocyte clones that do survive to expand in a larger body region," Barsh and colleagues explain.
The second study, led by Kyushu University geneticist Hidehiro Toh, also identified Arhgap36 as the orange cat fur gene. They found greater expression of this gene suppresses color pigment genes, shifting the dark brown to black eumelanin pigments to the reddish to yellow pheomelanin pigments.
Both papers are now online awaiting peer review on bioRxiv here and here.
https://doi.org/10.1101/2024.11.21.624608
https://doi.org/10.1101/2024.11.19.624036
My Bugs the Cat was as orange as could be. Not a white hair on him. He was also Manx and the most beautiful cat I ever saw. Crazy smart. The mutations mentioned make me wonder about susceptibility
to cancer.
I lost him a year ago. He was only 5.
I taught him to enjoy riding in the car and he and I ran from the Almeda fire together with nothing but that car. He was very independent and the experience was too hard on him.
So many places refused us a bed because I had a cat. I would have never survived the horrible places we had to endure without him!
The hardest thing I ever survived was watching him die. He would cling to my arm. He comforted me when I cried.
I lost everything. My home, my family, friends, my income and future. But the greatest loss I ever survived was Bugs.
I never imagined a pet could come to mean so much.
Well, maybe for an orange cat....
(Currently have two rescues: a Calico and a Tuxedo - both are alpha females and DO NOT get along, so they each give the obligatory "HISSS" as they pass each other in the hall.)
My cat is a lush solid black. The most super affectionate cat I have ever had; loves the dogs, and after a few days, loves other kittens. I think she thinks she’s the mother to everyone.
The other cat is an orange and white tabby. Pros - gets along with every other animal no matter their size. He’s extremely loving. He comes back to the house like clockwork. Cons- he NEVER stops meowing if he wants something. I mean it is loud and lasts for hours. Even the vet remarked about it when we took the cat to get neutered. he’s also a bit destructive and careless.
Both cats love each other.
For all I put up with that orange cat, he better be hunting mice big time when he’s outside.
Wow. I’m so sorry. Glad you had Bugs to get you through.
Cats are some darned odd critters. That’s what’s so cool about having them around, they have a WIDE range of personalities.
Did this study take any taxpayer money?
Does this color of cat have any advantage when crossing highways?
Those of us with beloved pets understand what you are saying.
On same gene branch known to incite evil behavior.
And, I like cats. Orange ones are just naughty.
Might be why the blue haired TWOT’s hate DJTrump so much.
Yep our orange “Tigger” was a rescue from the shelter. He is a real lover. He has a set routine that he follows everyday. Very predicable. He is probably one of the best we’ve ever had.
This article could have been written about my kitten experience from back in 2019. I've got a few gingers (3 - male) and a tortoiseshell (1 - female) all from the same litter. Daughter brought them home as foster pets when they were the size of mice. She nursed them to health feeding with medicine droppers. After several months, when they were growing and ready to go back to the shelter, we came to the realization that these little critters became part of our family and we couldn't part with them.
That’s great...do they ever gang up on the tortiseshell kitty as an outsider????
(I would think not...Siblings trumps Markings every time!)
And yep-keeping them long enough makes them yours without fail...:)
The tortiseshell is totally an outsider. She has arguments with the gingers, but they get along OK. The 3 brother gingers are very loving to each other. Like someone said earlier on this thread they all have their own personalities, just like people.
Great montage, especially the last (AI) image!
My orange coon cat Patrick was very clairvoyant. I could say something to him and he often displayed how accurately he understood. Miss him so much.
Their faces really resemble one another very closely.
Hilarious! So smart!
LOL!
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