A change took this fish from wings to limbs

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How ok It may have happened millions of years ago, however, which has long been an evolutionary mystery that has surprised scientists.

Now, American scientists say they have stumbled upon a possible answer.

By combining a single gene, researchers at Harvard University and Boston Children’s Hospital have engineered the zebrafish, which has shown the introduction of organ-like appendages.

To explain how animals transitioned from sea to land, scientists have traditionally looked at the fossil record. But over the past 30 years, scientists have discovered changes in genes that may be responsible for the change from fin to modern organ.

“The most surprising to me is that a dramatic change to the fin skeleton and musculature is possible with just one mutation,” said Brent Hawkins, a postdoctoral researcher at Harvard University and Boston Children’s Hospital and the first author of the study. In the magazine cell.

“Prior to this discovery, fin-to-limb infection was thought to involve manifold changes in a myriad of genes,” he noted via email.

“Of course this change was still a very gradual and complex process, but our mutants point out that it can also involve quick jumps, and that developing animals are able to incorporate new bones fairly easily.”

This depiction, depicted (from left) by researchers of the study, shows how a human organ has many long bones that allow for a wide range of movement; The final skeleton of a normal zebrafish with no articulation; And with a mutant zebrafish, new bones are growing away from the body in a pattern similar to that of organs.

innate ability

While previous research has identified genes that are required to make the bones of the fin and limb, no one has previously found a genetic change that causes a fin to move on a more limb-like pattern. , Explained via email to Hawkins.

The mutation the researchers found causes a change in the pectoral fin bones of the zebrafish, which connects slightly to the fish shoulder joint similar to how the human hand connects to the shoulder.

A new set of long bones – called medial radials – develops, forming a joint similar to the human elbow. Genetic changes include new muscles and joints that are found in organs but not simple wings.

The discovery of scientists has shown that the fish, which had lost the machinery necessary to develop body parts, actually maintains an innate capacity to build these structures.

Thumbnail-shaped zebrafish have become the mainstay of genetic research. They can easily lay in large numbers and breed easily, with a single mating pair producing hundreds of eggs each week. These fish are soft and easy to handle, as well as their eggs and embryos are translucent and easy to examine.

Researchers randomly mutated the zebrafish gene and then screened the fish systematically to find those that underwent interesting changes in their form – in this case organ-like structures.

They then trace DNA to which genes were affected before using the CRISPR gene editing tool – a method of modifying genes that won the Nobel Prize for Chemistry last year.

This genetic link between feathers and limbs, with more research, highlights how some animals transition from sea to land and what genetic mechanics are required to make it.

One question the team hopes to investigate next is whether the new bones change how zebrafish fins work and how the fish move.

Hawkins said, “Such complex and coordinated changes can lead to quite shocking results from changing one letter of DNA, and suggests that our fishery ancestors had latent ability to make raw genetic material and organs.”