Reprogrammed by a frog

Dolly, Polly, and friends proved that somatic cells are potentially totipotent, but the reprogramming that a somatic cell nucleus must undergo during cloning remains an error-prone black box. James Byrne, John Gurdon, and colleagues (University of Cambridge, UK) have now shown that the biochemically tractable frog oocyte system can be used to model reprogramming. A modified version of their protocol might allow the isolation of elusive reprogramming factors and, eventually, the reprogramming of somatic human cells for self-transplantation of stem cells.

The Cambridge group chose frog oocytes because, unlike most eggs, oocytes are not at all active in replication but very strongly so in transcription. To see if this transcriptional activity extended to reprogramming, Gurdon microinjected the oocytes with various cells: first mouse fetal fibroblasts, then mouse adult thymic cells, and finally human...