Your sedentary lap cat doesn’t seem to have much in common with its wild relatives who roam the African savannah. But researchers at Stanford Medicine have discovered a specific gene that controls much of the development of the stripes, spots, and spots that adorn all of a cat’s fur.
“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 Gregory Barsh, MD, PhD, Professor Emeritus of Genetics. “The color patterns and variability seen in animals like tigers, cheetahs and zebras have raised some key questions for us: What are the genetic and cellular mechanisms that lead to these patterns, and how have they changed during the mammalian evolution? create the amazing variety of shapes and forms that we see today? “
Barsh and his team answered part of this question: They identified a gene, DKK4, that helps regulate the early development of different coat patterns in domestic cats. DKK4, the team suggests, is likely to be involved in color patterns in all cats and perhaps other mammals as well.
The researchers’ results were published in Nature Communications on September 7th. Barsh is the lead author. Research Scientists Christopher Kaelin, PhD, and Kelly McGowan, MD, PhD, are co-lead authors.
What makes cats tick (ed)?
The researchers previously identified another gene that controls the variation in coat color in tabby cats. It’s the same gene that sets the difference between cheetahs and king cheetahs, which have thicker, more distinctive coat patterns.
“We knew from studying domestic cats that there were other genes that contribute to the formation of color patterns; we just didn’t know what they were, ”said Barsh.
They found a clue in the fetal cat tissue that seemed to guess the color of the coat: a thickening of the skin tissue in certain areas. These thickened regions form a “preliminary pattern” that mimics the possible color patterns in the fur of an adult cat. The thick area marks the later darker fur areas; the thin area marks the spots that are becoming lighter.
“We call this ‘establishment’ and it happens long before color appears and long before the hair follicles are mature,” Barsh said.
There are other genes that determine why, for example, some cats have spots and why some cats have stripes.
The preliminary sample provided the researchers with a kind of map that showed the cells involved in the pattern formation and the time at which the pattern was formed. The researchers then examined the genetic makeup of individual cells in the thick and thin regions of the skin. DKK4 was particularly active in the thickened skin, but not in the skin that remained relatively thin.
But to really capture the connection between DKK4 and early pattern formation, the team turned to the Abyssinian cat. Abyssinians are known to have a fuzzy color in their fur, with tiny, darker markings squeezed together as if someone had used a pencil to lightly shade a gray layer on their orange-brown fur. Barsh and his team identified disruptive mutations in the DKK4 gene that are responsible for the apparent lack of tabby markings in the Abyssinian cat, an appearance known as “ticked”.
“If you remove DKK4, the dark areas won’t go away completely, but they will get smaller and denser,” said Barsh.