microRNAs and Heart Function         Nature Med. 13, 486–491 and 613–618 (2007)      Tiny RNA molecules known as microRNAs regulate everything from development to stress responses — they also play an important role in heart function, two studies report.      Baofeng Yang and Zhiguo Wang of the Harbin Medical University in China and their colleagues report that people with coronary artery disease express more of a microRNA named miR-1. Overexpressing miR-1 in rats promoted irregular heartbeats; inhibiting miR-1 relieved the condition.      Meanwhile, a team led by Cesare Peschle of the Italian National Institute of Health in Rome and Gianluigi Condorelli of the University of California, San Diego, has shown that patients with a pathological thickening of heart muscle known as cardiac hypertrophy produce less of another miRNA, miR-133. Inhibiting miR-133 in mice triggered the condition, whereas overexpressing miR-133 prevented it.

microRNAs Evolved before multicellualrity  - Genes Dev. 21, 1190–1203 (2007)      MicroRNAs have shown up for the first time in a unicellular organism, suggesting that they evolved before multicellularity.  Previous searches in yeast and bacteria have failed to find any microRNAs, but Yijun Qi of the National Institute of Biological Sciences and Xiu-Jie Wang of the Chinese Academy of Sciences, both in Beijing, and their colleagues have now isolated some from the unicellular green alga Chlamydomonas reinhardtii.  The team showed that several of these microRNAs cleave specific messenger RNAs, a key part of the mechanism by which microRNAs regulate gene expression. What's more, expression of some microRNAs changed during gamete formation, suggesting a role in the reproductive process.