Stimulus-triggered Acquisition of Pluripotency


Haruko Obokata, a biologist at RIKEN, grabbed headlines last month by discovering a phenomenon termed stimulus-triggered acquisition of pluripotency or STAP cells. The finding took the science community by surprise as it revealed that just squeezing or bathing cells in acidic conditions could turn them into pluripotent stem cells.

Role of transcription factors has been long appreciated in inducing pluripotency but none had considered the importance of external stress. Obokata got the insight when she noticed that cells squeezed through a capillary tube shrunk to size comparable to stem cells. So, she stressed out cells in all possible manners. In addition to squeezing and low pH, exposure to a bacterial toxin also induced the shift to pluripotency. To convince peers that the pluripotent cells were induced and not pre-existing, she converted T cells to pluripotent cells and also grew whole mouse from embryo injected with labelled STAP cells. Her finding hints at the possibility that the pluripotent cells normally observed in our body are created as our body’s response to stress.

Fluorescently tagged STAP cells were injected in mouse embryos. The pluripotency is verified by the fact that glowing cells show up in every tissue of resulting mouse.
Fluorescently tagged STAP cells were injected in mouse embryos. The pluripotency is verified by the fact that glowing cells show up in every tissue of resulting mouse.

The most surprising discovery was that STAP cells can even form placental tissue, something that neither iPS cells nor embryonic stem cells could do. 25% of the cells survived the stress of which 30% were converted, far above the 1% in the case of iPS cells. The clinical importance of these cells is immense.

The papers behind the finding came under a lot of scrutiny for irreproducibility of results and duplication of images. The authors have admitted to the wrong images of placenta, which they would correct soon, but stated that the irreproducibility was due to the fact that acid bathing cells isn’t as simple as it sounds. As the investigations are on, it is hoped that the whole phenomenon doesn’t come out to be a cooked-up affair.

Read the full article here:
Obokata. H., Wakayama. T., Vacanti. C. A. et al.; Stimulus-triggered fate conversion of somatic cells into pluripotency; Nature 505, 641-647; 30 January 2014; doi: 10.1038/nature12968

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