Fish DNA Makes Limbs Sprout in Mice

[Buster's Uncle]

Fish DNA Makes Limbs Sprout in Mice
By Tia Ghose, LiveScience Staff Writer  | LiveScience.com – 22 hrs ago...


The genome of a primitive fish that was once thought to have died when the dinosaurs did has now been sequenced by scientists — and when put into mice, some of the fish DNA caused mice to sprout limbs.

The new analysis, described today (April 17) in the journal Nature, could help to reveal how primitive fish swapped their fins for limbs when they moved from land to sea.

The fish, called a coelacanth, seems to carry snippets of DNA that can turn on genes that code for forelimbs and hind limbs in mice. The new discovery could shed light on how four-legged creatures, called tetrapods, evolved. [Image Gallery: The Freakiest Fish]

"It really is a cornerstone from which we can view tetrapod evolution," said study co-author Chris Amemiya, a geneticist at the Benaroya Research Institute in Seattle, Wash.

Living fossil

The coelacanth was once thought to have gone extinct about 70 million years ago, roughly around the time dinosaurs vanished. But in 1938, a fish trawler brought a bluish-purple, 3.3-foot-long (1 meter) fish with fleshy fins to the South African naturalist Marjorie Courtenay-Latimer. It turned out to be an African coelacanth.

 

Over the next several decades, scientists unearthed a few hundred of the elusive creatures living around the Comoros Islands in the Indian Ocean, as well as off parts of Indonesia.

The coelacanth intrigued scientists because it was a kind of "living fossil": It had changed so little over the last 400 million years that it might reveal how fish first grew limbs and walked on land.

Deepening the mystery, other research showed that fish, mice and other animals carry many of the same genes. But in fish, those genes code for fins, whereas in land-based animals, they create limbs.

Mysterious genes

Because the fish were so endangered, it was difficult to study their body plan in detail. But Amemiya and his colleagues managed to get tissue samples from a coelacanth from the Comoros Islands.

Using that tissue, the team sequenced the primitive fish's genome and analyzed it. They found a small snippet of DNA called an enhancer that was present in both coelacanths and four-legged creatures, but missing in other fish.

The enhancer was part of the "dark matter" of the genome — the large fraction of the genome that doesn't code for proteins, but somehow turns genes on and off.

When they put the DNA snippet into mice, it seemed to turn on the genes to make the forelimbs and hind limbs in mice, Amemiya told LiveScience.

Limb beginnings

The coelacanth's genome may harbor many more secrets to the evolution of limbs, said Nancy Manley, a developmental geneticist at the University of Georgia, who was not involved in the study.

"The genome really sets a path forward for the next 10 or 20 years," said Scott Edwards, an evolutionary biologist at Harvard University, who was not involved in the study.

But coelacanths aren't the only primitive fish that could shed light on limb evolution. Another bizarre fish called the lungfish may actually be more closely related to four-legged creatures, "so that's going to be an important species to look at," Edwards told LiveScience.

http://news.yahoo.com/fish-dna-makes-limbs-sprout-mice-170846629.html

Are we talking EXTRA limbs or what?  Mice tend to grow legs already...

[Buster's Uncle]

Scientists decode DNA of 'living fossil' fish
By MALCOLM RITTER | Associated Press – 21 hrs ago...

This 2008 image made available by the Smithsonian's National Museum of Natural History shows an African coelacanth (Latimeria chalumnae). Scientists have decoded the DNA of the celebrated "living fossil'' fish, an achievement that should help researchers study how today's land animals with backbones evolved from fishy ancestors. The African coelacanth is closely related to the fish lineage that led to mammals, amphibians, reptiles and birds, and it hasn't changed much from its ancestors of even 300 million years ago, researchers said. So it can give an indirect glimpse of the ancient fish that made the move to land. (AP Photo/Smithsonian, Chip Clark)

NEW YORK (AP) — Scientists have decoded the DNA of a celebrated "living fossil" fish, gaining new insights into how today's mammals, amphibians, reptiles and birds evolved from a fish ancestor.

The African coelacanth (SEE-lah-kanth) is closely related to the fish lineage that started to move toward a major evolutionary transformation, living on land And it hasn't changed much from its ancestors of even 300 million years ago, researchers said.

At one time, scientists thought coelacanths died out some 70 million years ago. But in a startling discovery in 1938, a South African fish trawler caught a living specimen. Its close resemblance to its ancient ancestors earned it the "living fossil" nickname.

And in line with that, analysis shows its genes have been remarkably slow to change, an international team of researchers reported Wednesday in the journal Nature.

Maybe that's because the sea caves where the coelacanth lives provide such a stable environment, said Kerstin Lindblad-Toh, senior author of the paper and a gene expert at the Broad Institute in Cambridge, Mass.

Modern coelacanths make up two endangered species that live off the east coast of Africa and off Indonesia. They grow to more than 5 feet long and have fleshy fins.

The coelacanth's DNA code, called its genome, is slightly smaller than a human's. Using it as a starting point, the researchers found evidence of changes in genes and in gene-controlling "switches" that evidently aided the move onto land. They involve such things as sense of smell, the immune system and limb development.

Further study of the genome may give more insights into the transition to living on land, they said. Their analysis concluded that a different creature, the lungfish, is the closest living fish relative of animals with limbs, like mammals, but they said the lungfish genome is too big to decode.

The water-to-land transition took tens of millions of years, with limbs developing in primarily aquatic animals as long as nearly 400 million years ago, by some accounts, and a true switchover to life on land by maybe 340 million years ago, said researcher Ted Daeschler.

Daeschler, curator of vertebrate zoology at the Academy of Natural Sciences of Drexel University in Philadelphia, who didn't participate in the new work, said genome research provides a way to tackle some previously unanswerable questions in evolution.

He emphasized that DNA is best used in combination with fossils.

"This is a great detective tool," he said. "You might collect DNA evidence at a crime scene, but you can't ignore the dead body.... With paleontology, we have the dead bodies."

http://news.yahoo.com/scientists-decode-dna-living-fossil-fish-183629802.html

[Unorthodox]

Oh, god.  WHY are we shoving fish DNA into mice? 

All this island of DR Moreau crap gives me the willies. 

[Buster's Uncle]

I wouldn't want an extra willie.