The findings, available in the online edition of the journal Nature, may aid scientists in their understanding of how a progenitor cell, or stem cell, decides to become a heart cell, as well as offer researchers a way to predict how other microRNAs in the body control the production of important proteins. The discoveries could provide clues important to understanding both stem cell biology and congenital heart disease.

In order for cells to produce the proteins that carry out all of life's functions, the information contained in genes is first copied by special enzymes into messenger RNA, or mRNA. Information in mRNA then is used to make a particular protein.

Scientists believe microRNAs seek out and bind to mRNA, fine tuning the amount of protein that mRNAs manufacture. In some cases, microRNAs shut down protein production altogether.

The UT Southwestern researchers discovered that a microRNA called miR-1 targets the mRNA of the gene Hand2, a key regulator of heart formation. The microRNA turns off production of the Hand2 protein at precisely the right time to allow the proper development of heart muscle.

"We think that Hand2 is necessary in the early stages of embryonic development to allow proliferation and expansion of a pool of muscle progenitor cells that can eventually develop into the heart," said Dr. Deepak Srivastava, senior author of the paper. "But at some point production of Hand2 needs to be shut off so the cells can go on to the next stage in their development and differentiate into heart muscle cells. We identified Hand2 as the target for this particular microRNA."

Dr. Srivastava is a former professor of pediatrics and molecular biology at UT Southwestern, where h
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Contact: Amanda Siegfried
amanda.siegfried@utsouthwestern.edu
214-648-3404
UT Southwestern Medical Center
12-Jun-2005