Master mechanism behind regeneration of body parts discovered

Washington, Oct 20 (ANI): Using zebrafish as a model, researchers at the University of Michigan have discovered how the process of regeneration of body parts works.

Some animals have the unique ability to regenerate their lost body parts. For example, Newts can lose a leg and grow a new one identical to the original. Zebrafish can re-grow fins. These animals and others also can repair damaged heart tissue and injured structures in the eye.

Humans, however, have only rudimentary regenerative abilities, so scientists hoping eventually to develop ways of repairing or replacing damaged body parts are keenly interested in understanding the mechanism behind regeneration.

They have found that some of the same genes underlie the process in different types of tissues. Genes involved in fin regeneration and heart repair are also required for rebuilding damaged light receptors in the eye, they found, suggesting that a common molecular mechanism guides the process, no matter what body part is damaged.

The researchers briefly exposed zebrafish to intense light, which destroys the light receptors in their eyes, just as staring into the sun harms human eyes. But unlike humans, who remain blinded if the damage is severe enough, zebrafish repair the damage with new nerve cells (neurons).

The researchers suspected they develop from cells in the retina called Muller glia, known to have the ability to give rise to nerve cells, and in previous work another graduate student in Raymond's lab confirmed the suspicion.

In the current work, Zhao Qin, a graduate student in the department of Molecular, Cellular and Developmental Biology, wanted to find what prompts Muller glia to start the regeneration process.

To get at the question, she looked at patterns of gene expression in Muller glia from damaged, regenerating zebrafish retinas and from undamaged zebrafish retinas to see which genes are expressed differently in damaged and undamaged retinas.

"Of course I found a lot of genes - a total of 953, but two were of particular interest," Qin said.

The two genes, hspd1 and mps1, had been found in other studies to be required for fin and heart regeneration in zebrafish, and Qin's work showed that they also were switched on in Muller glia from damaged zebrafish retinas.

Co-author Pamela Raymond said: "This suggests that, although we don't fully understand it yet, there might be a bigger molecular program, involving not just these two genes but a number of cooperating genes that are required for injury-triggered regeneration."

The study has been published in the Proceedings of the National Academy of Sciences.

It will be presented on Oct. 19 at the annual meeting of the Society for Neuroscience in Chicago. (ANI)