“A small modulatory dsRNA specifies the fate of adult neural stem cells”, by Kuwabara et al. (Cell 2004; 116: 779 – 793) & reviewed by Mark Mayhew.

Epigenetics involves modifications to the genome that generally result in silencing of gene expression. In this study, a novel small RNA has been discovered that is involved in the activation of gene expression. These so-called small modulatory RNAs (smRNAs) interact with a transcriptional repressor of neuron-specific genes, NRSF/REST, & an associated DNA sequence element, NRSE/RE-1, found in the promoter region of these genes. Interestingly, upon binding of smRNAs, NRSF/REST remains attached to NRSE/RE-1 & subsequently activates gene expression. This gene expression induces differentiation of neurons from progenitor or “stem” cells. Experimentation has shown that smRNAs are sufficient & necessary for this process. smRNAs are an exciting discovery & have a potential application in “stem” cell therapies which seek to replace CNS neurons that have been damaged through injury or disease.