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Nature Cell Biology 8, 112 (1 February 2006) | doi:10.1038/ncb0206-112

microRNA signals cell fate

Myrto Raftopoulou

In signalling networks, a positive-feedback loop can form when a weak or transient signal enhances expression of components of its pathway to amplify or stabilize a particular cellular response. Li and Carthew (Cell 123, 1267; 2005) recently described an alternative, double-negative feedback mechanism in the fly eye that involves interplay of a transcription factor with a microRNA (miRNA) to drive developmental decisions.