Link between reptile, human heart evolution

September 4, 2009 9:10:34 AM PDT
Researchers at the Gladstone Institute have made a major discovery on the evolution of the human heart. They have uncovered the reason why our hearts have developed differently than those of cold-blooded reptiles -- a discovery that could eventually lead to new treatments for genetic heart defects.

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It takes a lot to turn heads on this branch of the evolutionary tree, but word that researchers have isolated a protein that helps differentiate humans from reptiles is bound to grab some attention.

"First of all, we've answered the question which has been, how have hearts evolved from three-chamber arrangement to four-chamber arrangement," said Benoit Bruneau, Ph.D. with San Francisco's Gladstone Institute.

Bruneau and his team examined a protein called TBX5. They believe it turns on the genes that prompt the hearts of humans and other mammals to divide down the middle, creating the four chambers necessary for warm-blooded circulation which moves blood much faster to maintain a constant body temperature.

To test their theory, they genetically altered the protein in mice to more closely match those found in reptiles.

"By doing so we transformed the mouse heart into what looked like a frog heart," said Bruneau. "And so we thought that was a pretty amazing result and thought, well, maybe there's an evolutionary connection."

Beyond providing an insight into the evolution of cold-blooded creatures, Bruneau's team believes the discovery could eventually have life-saving implications here in the warm-blooded world.

"The gene that we studied in this work is a gene that is involved in human congenital heart defects," he said. "So when it's mutated people have either holes in the heart or they have arrhythmia or a variety of congenital heart defects."

He believes that with advanced study, researchers might someday be able to develop gene therapies to prevent heart defects before babies are born.

"That in itself is really hard to tell. But certainly what we've been able to accomplish is the first step towards that," he said.

Heart defects are the most common birth defect, occurring in one out of every 100 births worldwide. One of the deadliest defects involves infants born with a single chamber heart, similar to those found in some reptiles.

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