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U. scientist bring back ancient gene

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At top and bottom left are two mice in which a gene named Hoxb1 has been disabled. The gene controls the development of nerves needed for facial control.

At top and bottom left are two mice in which a gene named Hoxb1 has been disabled. The gene controls the development of nerves needed for facial control.

Peter Tvrdik, University of Utah

For the first time, scientists at the University of Utah have re-created a gene that was lost in evolution.

A report on the experiment by the U.'s Mario Capecchi and Petr Tvrdik is in Monday's edition of the journal Developmental Cell. The project amounts to "reverse engineering," according to the magazine.

A university news release says this experiment shows some workings of evolution on a molecular level. It also notes the study could raise the possibility of a new type of gene therapy.

Perhaps, according to the U., a related gene could be inserted into a mutant, disease-causing gene, restoring normal function.

According to the news release, early animals had 13 of the genes called Hox genes. Jawed fish retain this configuration. But in animals that evolved from jawed fish, including humans, the Hox gene split into four sets of 13, meaning 52 genes altogether.

However, as these genes specialized, some lost function. In humans and other mammals, Capecchi told the Deseret Morning News, there are 39 Hox genes.

Mice and humans have Hox genes called Hoxa1 and Hoxb1, which derived from the original Hox genes.

"A1 is involved in making early part of the hind brain" during development of the embryo, he said.

B1 comes into play about two days later than a1 in an embryo's development. It helps make neurons in the brain that are involved in control of facial muscles. Before the Hox genes split into four groups, between 480 million years ago and 530 million years ago, one gene did what the a1 and b1 genes now do.

"This is a very common thing that happens during evolution," Capecchi said, with genes duplicating and acquiring new functions.

Through experimentation — snipping and splicing a1 and b1 genes or simply destroying the b1 gene — Capecchi and Tvrdik re-created the ancestral gene.

Mice that had no b1 gene were left without facial muscle function. If a blast of air is squirted into their faces, they cannot blink their eyes or ears. "It has complete facial paralysis," Capecchi said.

But a mouse with the re-created gene is "pretty normal, even if we eliminate the late gene from that mouse." It has typical mouse reactions to a squirt of air, wincing, closing its eyes and folding its ears back.

"It's not quite as good as the normal animal," Capecchi said, as it no longer has the genetic specialization that developed after the genes split up.

How is it different?

"We're looking at that in much greater detail now," he said. "It moves its face perfectly normally, it opens and closes its eyes, it pushes back its ears and so on."

But on a molecular scale, the gene is functioning in areas where it should not. It causes some other genes to turn off that would not be switched off with a normal animal. Still, he said, "it's fairly subtle."

If one of the mice with the re-created ancient gene were in the wild, it would possibly have a slower reaction when an owl swooped in.

"My guess is, out in the field it wouldn't be as capable," Capecchi said.

E-MAIL: bau@desnews.com