Two microRNAs, single-stranded RNA fragments known to influence gene expression, have been shown to regulate cell fate decisions. The findings may have implications for the generation of induced pluripotent stem cells.

One of the microRNAs, miR-145, triggers the differentiation of neural crest stem cells into vascular smooth muscle, and is also needed to reprogram adult fibroblasts into smooth muscle cells, Deepak Srivastava and colleagues report online this week in Nature. T

he findings are evidence that a single microRNA can efficiently coax stem cells to form a specific cell type, and regulate the reprogramming of cells into an alternative fate.

The team also shows that miR-145 and another microRNA, miR-143, help repress proliferation and promote differentiation of smooth muscle cells.  The two microRNAs target a network of transcription factors that includes Klf4, one of the key ingredients in the recipe to induce pluripotent stem (iPS) cells.  iPS cells - mature cells reprogrammed into a stem cell-like state - are attractive because they represent an ethical, potentially patient-matched source of stem cells.

DOI: 10.1038/nature01895