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
Well thank goodness they finally figured it out!
Not true about orange cats stupid.
My orange cat is very smart..........
Is this where we get redheads from? A gene mutation? Otoh my experience with orange cats is they are usually bad asses and rule the feral hood. Never bet against an orange cat in a fight.never.
Hahahahah...now I have these two brothers from the same litter:
Agree. I had an orange cat who was very smart. And he knew it.
He was full of mischief and such a delight.
Little more than I needed to know there.
The black cat portrayal is correct for at least one of my blackies but the orange as not to bright isn’t so. Surly, lazy, slow moving, lovable lugs is more like it but not dumb at all.
Mine is a Calico Tabby Orange and White. She guards my chickens and kills rats and mice for tuna..............
Tabby cats, of all colours, tend to be about the middle of the road. Not stupid, but not genius either.
Although, individual cats may vary in intelligence within their breed.
I find orange tabby cats to be the most people oriented cats.
BTTT
We adopted a stray orange cat several years ago. She was probably about 12 weeks old, has always been pretty aloof. Not affectionate at all. Still, you get attached. My adult son moved in with us, and one day brought home a black, gold and cream kitten. She has more energy than the energizer bunny. Goes flying through the house like she’s on fire. Affectionate, too. She was old enough that she went into heat about a month after he brought her home. Now we have to get her spayed, too. I wish our orange cat had her personality...
PLEASE: No Trump jests (i.e., “Orange Cat Bad”, etc.!).
.
My orange fatty thinks he’s still a kitten climbing the Christmas tree. It’s destroyed ugh. But gingers are characters that’s for sure. Love em.
Sweet. We got a tuxedo and an orange cat from the same shelter and they get along so great, thankfully.
That’s been my experience with them too. Very friendly and affectionate.
My third favourite cat was a Tuxedo cat. His name was Tucker. Unfortunately, my parents took in my nephews huge cat and he stressed my Tucker into going into liver failure. I was so upset that I made my nephew take it back.
My orange boy (more of a dusty orange) is the biggest cuddler in the world. We named him George Harrison because, like the Beatle, he’s so laid back. Best cat of the 3 we’ve had!!
I never heard that orange cats are stupid. But they are known to have feisty personalities. I have always specialized in tortie and whites, which are said to have "tortitude". They certainly are not docile. They are always getting into something. But they are super affectionate, too. And SMART.
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