Small gene class influence cell behaviour

Geneticists at Dartmouth Medical School have discovered a family of unusually small genes that act in the finely tuned yet remarkably versatile orchestration of development and behaviour, adding still another dimension to the diversity and complexity of the cell.

Unlike most genes, these do not encode for proteins, but rather produce tiny regulatory RNAs, dubbed microRNAs because they are far smaller than other RNA molecules. If as abundant and varied in all species as they seem, this novel class of regulators offers promising and potentially far-reaching opportunities to understand critical steps in development.

Victor Ambros, professor of genetics, and Rosalind Lee, a research associate, are behind the research, the same team who identified the first of these little RNAs in a microscopic roundworm a decade ago.

Until recently, that original small RNA, the product of the worm lin-4 gene, was the only example. Now Lee and Ambros report that "there are dozens, probably hundreds of little genes like lin-4."

Each RNA is a copy of a gene, part of the cell's DNA (deoxyribonucleic acid). Organisms have thousands of genes that collectively hold information for all the components of an organism. The Dartmouth researchers found 15 new genes in the worm, C. elegans, which all fit this microRNA family and document evidence for many more. Moreover, analysis showed that two of these particular small RNAs are also found in humans, including one that could play a role in the development of heart tissue.

The work demonstrates that these microRNAs, are extensive and diverse classes of regulators. "Each microRNA is probably matched to one or more other genes whose expression it controls. Their potential importance to control development or physiology is really enormous. If there are hundreds of these in humans and each has two or three targets that it regulates, then there could be many hundreds of genes whose activity is being regulated this way." said Ambros. "It's important to find all the human microRNA genes and understand what they do."