Over 60 yearsscientists try to identify the responsible gene of the red color in the cloak of cats. Unlike human beings, in felines – as in many other pets – the color of the hair is closely tied to sex. Male cats are almost always those to show off a completely red fur, while females have more frequently tricolor cloaks or red-black.
Research
Recently, two distinct research groups have managed, independently, to identify the genetic mutation which determines the coloring rack. During the study, they also identified an unsuspected protein connected to this stretch. The results, still awaiting scientific revision, have been published on the platform “BIORXIV “.
What happens in nature
When a red cloak cat mates with a black one, from the litter, both plain kittens and with multicolored coat, such as red and black or tricolor can be born. In most cases, the little ones with mixed fur they are femaleswhile males tend to be of a single color. This phenomenon is explained by genetics: the genes that determine red and black colors are on the chromosome x.
Since females have two X chromosomes, each cell can activate one of the two in a random way, giving rise to different color patches on the body. The males, on the other hand, having only one X chromosome (and a y), show only one colorinherited from the parent who provided that chromosome.
Mutation
In many mammals, including humans, it is a mutation in the gene that codes the MC1R protein – a melanocortin receptor – to determine the red coloring of hair or hair. In cats things go differently. In domestic felines, in fact, the gene that produces MC1R is not located on the X chromosome, and most cats with a red mantle do not have mutations at all in this gene. A peculiarity that for years has left the geneticists perplexed. “It was really a genetic enigma“, he explained Greg Barshgeneticist of Stanford University, in an interview with Science. Barsh took part in one of the recent studies that have tried to solve this mystery.
An unsuspected protein
Together with his team, Barsh has obtained leather champions from four feline embryos – some with a red cloak, others with a non -red cloak – taken from veterinary clinics during sterilization interventions. Analyzing the cells responsible for pigment production, they measured the amount of RNA associated with the genes active in those tissues. The results were surprising: in red cats, a gene called Arhgap36located on the X chromosome, showed about RNA levels 13 times higher Compared to non -red cats. A figure that strongly suggests its direct role in determining the fawn coloring of the cloak.
A second study, conducted by Professor Hiroyuki Sasakibiologist at the University of Kyushu in Japan, confirmed similar results by analyzing the genomes of over 280 cats from different parts of the world. Also in this case, attention has focused on the gene Arhgap36. Curiously, the DNA of the gene itself is identical both in red cats and in those of other colors. However, researchers found that red cats produce much more RNA associated with this gene. The reason is not a mutation of the gene itself, but the lack – in the red cats – of a segment of DNA located nearby, which normally regulates and limits the production of RNA. Without this control, the gene activity increases, leading to the characteristic fawn color.
A step forward in research
To date, nobody had ever hypothesized a link between the ARHGAP36 gene and the pigmentation of the skin or hair. To make the discovery even more surprising is the fact that, in general, a gene deletion – that is, the loss of a portion of regulatory DNA – tends to reduce the activity of a gene, not to increase it.
“It is rather unusual that the absence of a regulatory segment makes a more active gene“, commented the geneticist Carolyn Brown
of the University of British Columbia, interviewed by Science. While not having participated directly in the studies, Brown underlined the originality of this discovery in the field of animal genetics.