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TUESDAY, September 14, 2021 (HealthDay News) – Your favorite cat may seem like little like its relatives in the wild, but they all share a key gene that gives them their distinctive looks.
Why the fur of cats is decorated with stripes, spots and spots has long been a mystery. Now researchers have identified a specific gene that all domestic cats, wild big cat species, and possibly even other mammals, have and that regulates the development of these coat patterns.
“Color patterns are one of those unsolved biological mysteries; there is no suitable model organism to study it – mice have no stripes or spots, ”said lead author Dr. Gregory Barsh, Professor Emeritus of Genetics at Stanford Medicine in California. “The color patterns and variability that you see in animals like tigers, cheetahs and zebras have asked us some key questions.”
Barsh’s team wanted to understand the genetic and cellular mechanisms that underlie these patterns and how they evolved to produce today’s diversity of shapes and forms.
When examining fetal cat tissue, the researchers found a “premattern” in the skin of cats that was thicker where dark fur would appear and thinner where light fur was.
“We call this ‘establishment’ and it happens long before color appears and long before the hair follicles are mature,” Barsh said in a Stanford press release.
The researchers used this as a map showing which cells played a role in the formation of the pattern and when it was formed. When they examined the genetic makeup of individual cells, they found that a gene called DKK4 was active in thickened skin, but not in thinner skin.
Then the investigators examined Abyssinian cats. They are known for their fuzzy-colored fur, darker markings squeezed together like pencil shades of gray on an orange-brown fur.
This appearance is called “tickled”, unlike that of tabby cats. And researchers discovered that it was caused by mutations in the DKK4 gene.
“If you remove DKK4, the dark areas won’t go away completely, but they’ll get smaller and denser,” Barsh said.
Even all white or all black cats are patterned under their fur.
The researchers explained that two different processes create a color pattern. The first creates the pattern as a cat embryo is developing. The second translates this pattern into pigment that is produced in the hair follicles.
The pigment is absent in white cats. For other single-colored cats, instructions override the pattern to produce only the one color, the study authors said.
How DKK4 “paints” the color patterns of domestic cats is still a mystery, but scientists know that it interacts with an essential class of proteins called WNTs.
WNTs and DKK4 work together to form the pre-pattern when an embryo is only 2 to 3 millimeters long. While DKK4 is involved in marking the areas with pigmented hair, it is unclear how these areas of the skin “remember” which target pigment to produce.
“This is one of the big unanswered questions in our work – how to combine the process of prepattern formation with the process that implements the pattern later in development,” said Barsh. “That’s something we’re actively trying to figure out.”
Nor is it the only answer to why cats have color differences.
Researchers previously identified another gene that controls the variation in coat color in tabby cats. It’s also the gene responsible for differentiating between cheetahs and king cheetahs, which have thicker, more distinctive coat patterns.
“There are other genes that are responsible, for example, why some cats have spots and why some cats have stripes,” Barsh said.
The research team noted that they plan to investigate this further.
The results were published in Nature Communications on September 7th.
More information
Scientific American provides some details about cat behavior.
SOURCE: Stanford Medicine, press release, September 7, 2021
