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A new study may have discovered exactly what makes orange cats special – although it is not for the reason you think.
Ginger kittens are known among cat owners to be particularly friendly and fiery. To geneticists, however, the unique character of this house cats comes in the unusual way that they get their color. Now, scientists say they have untangled a long -standing mystery by identifying the specific DNA transfer responsible for this golden shade – and the variant has been found in any other animal.
The genetic variant is described for the first time in an article published on May 15 in the journal Current biology.
“This is a really unusual type of mutation,” said Christopher Kaelin, author of the main study, a main scientist in genetics at the University of Stanford in California.
The vast majority of entirely orange cats are men, which led scientists to reason in decades that the genetic code of the orange color is transported to the X chromosome. As for other mammals, female cats have two X chromosomes, while males have an X and a Y. Any male cat carrying the orange trait on its chromosome X will be completely orange. A woman should inherit the line on the two chromosomes (one of her parents) to be completely orange, which makes her less likely. Instead, most of the orange fur female cats have uneven – calicot or turtle – patterns that may include black and white.
But where the mutation exists on the X chromosome, and how it gives birth to orange coloring, has been an enigma so far. As a rule, mutations that lead to yellow or orange fur in animals (and red hair in humans) occur in genes that control color. And these genes are not transported to the X chromosome. “This suggested that by identifying the molecular cause, we could learn something new and interesting, which turned out to be the case,” said Greg Barsh, a professor of genetics and pediatrics in Stanford.
The results not only elucidated the particular origins of the charismatic coloring of certain cats, but also revealed new perspectives on a familiar gene.
The first step was to identify genetic mutations that are unique to orange cats and could give birth to their color. For a decade, Kaelin frequented cat shows, asking the owners of ginger cats if he could take animal DNA samples with swinging of the cheek. (It is also interested in models similar to those found in wild cats such as leopards and ocelots, which are common in popular breeds such as Bengal cats and toygers.)
By comparing his DNA collection with feline genomes that have been sequenced in the last five to 10 years, he and his research team have found 51 genetic variations on the X chromosome shared by orange males. But 48 were also found in non -orange cats, which left three probable candidates for the elusive transfer.
One was a small deletion of pairs of 5,076 bases which removed approximately 0.005% of the X chromosome in a region which does not seem to code for a particular protein. The deletion was not located in a gene, where mutations are generally found. However, the mutation lies between two sites associated with a neighboring gene called ARHGAP36, which regulates an important hormonal signaling pathway Used by almost all mammal cells and tissues. There was no known link with pigmentation. The gene is not even excited in cells producing pigments.
To find out how the gene affects color, Kaelin studied its actions in the living tissues collected in sterilization and sterilization clinics which were otherwise thrown. Experiments have shown that, in one way or another, the active deletion ARHGAP36 in pigment cells, where it blocks the production of black pigment so that cells produce in place of Orange.
The variant has not been found in other animals, including wild cats that have given birth to domestic cats.
“It is a genetic exception that was noticed over a hundred years ago,” Kaelin said in a statement from the University of Stanford. “It is really this comparative genetic puzzle that motivated our interest in orange linked to sex.”
This singularity suggests that the mutation probably occurred once during domestication, then was raised selective, said Kaelin. “We see the same mutation in all orange cats that we have examined in a large geographical area, so there is only one mutation that happened,” he said. “And we know that the mutation is quite old because there are representations of Calicotys cats in Chinese art which dates from the 12th century.” He added that prehistoric DNA specialists could be able to use the new results to identify when and where the mutation appeared originally.
“The identified variants could serve as precious tools in the genetics of populations to trace the history of domestic feline evolution,” said Hannes Lohi, professor of veterinary bioscience and genetics at the University of Helsinki in Finland. Lohi was not involved in the study.
In the meantime, Kaelin and his collaborators want to understand how a small deletion which is not itself in a gene can change the activity of a gene nearby.
“The objective is, of course, that we will learn the mutation,” noted Barsh, “but we also want to know more about mutational mechanisms in general: why is it so unusual and the same mechanism could occur in other genes that cause other phenotypes in other animals?” He stressed that there are many conditions in humans who are considered genetic, but for which no genetic mutation has been identified. Perhaps, it postulates, the problem is not only that we have not located mutations, but that we do not understand all the ways whose mutations can cause diseases of disease in the first place.
And could the unusual genetics of orange cats perhaps explain their particular personalities? So far, Kaelin says that he and his colleagues have no reason to think so, although other researchers can use the results of the new study to seek associations between the behavior and color of the coat. “I think orange cats have really convinced their owners that they are different, but they have not yet convinced,” he said.
Amanda Schupak is a health and health journalist in New York.