Evolution: the power of a few genes (Evolution)

by David Turell , Monday, May 22, 2023, 18:29 (549 days ago) @ David Turell

Feathers or no feathers:

https://www.sciencealert.com/tweaking-just-a-few-genes-transforms-scales-into-feathers?...

"The feathers, fur, and scales that adorn different members of the animal kingdom may look quite different, but they're all made of the same basic stuff. And, as it turns out, it only takes a relatively simple genetic tweak to produce one instead of the other.

"By targeting the sonic hedgehog (Shh) gene, geneticists Michel Milinkovitch and Rory Cooper of the University of Geneva in Switzerland altered embryonic chickens to grow feathers instead of scales on their usually squamous feet.

"And the alteration is permanent. Once hatched, the chicken's unusually feathery feet will stay that way for life.

"'We demonstrate that stage-specific transient agonism of sonic hedgehog (Shh) pathway signaling in chicken triggers a complete and permanent transition from reticulate scales to feathers on the ventral surfaces of the foot and digits," the researchers write.

"'Resulting ectopic feathers are developmentally comparable to feathers adorning the body, with down-type feathers transitioning into regenerative, bilaterally symmetric contour feathers in adult chickens."

"Previously, Milinkovitch's lab has demonstrated that the various keratinized skin appendages (hair, feathers, and so forth) have the same evolutionary origin in the ancestral reptilian hundreds of millions of years ago that later diversified into the incredible variety of animals living in the world today.

"And in all these animals, the development of these structures begins as structures known as placodes in the skin, which thicken and then start to grow into the scales, spines, or whatever appendage that animal tends to have.

"Shh plays a key role in the development of these skin appendages. The signaling pathway is an important one with its fingers in many embryonic pies, mediating the development of body shapes and structures, patterning, differentiation, and growth.

"For instance, Shh is an important factor in feather form and diversification, flight feather positioning in birds, and the development of hair follicles in mice.

***

"The researchers say this has implications for our understanding of how animals evolved and diversified. Natural variations in Shh signaling are probably an evolutionary driver of skin appendage diversity, and this diversity was not particularly difficult to achieve.

"'Our results indicate that an evolutionary leap – from scales to feathers – does not require large changes in genome composition or expression," Milinkovitch says.

"'Instead, a transient change in expression of one gene, Shh, can produce a cascade of developmental events leading to the formation of feathers instead of scales.'"

Comment: this shows some evolutionary advances have simple genes behind them. But we do not know how the genes do it as a series of biochemical reactions. Still a black box between gene and results.