What are the limits of an embryo’s powers? Scientists seem to marvel at how cells from early embryos can do remarkable things – and indeed, it is astonishing that they can grow an entire new person from a single cell.
I chatted to one researcher who has tested whether the first two cells in an embryo are the same — or whether, after this very first division in the dawn of the embryo’s life, one cell is already headed towards one fate and the other has a different cellular career in mind. There’s actually quite a debate about this amongst developmental biologists.
Jiying Hao separated the two cells of mouse embryos and tested whether both cells could grow into a line of embryonic stem cells, or just one of them could. She found only two cases, amongst many attempts, in which both cells produced stem cells – compared with numerous cases in which one cell could and the other could not. So even at this stage, the two cells seem to have different aptitudes.
For more weirdness, you can count on fertility doctor Panos Zavos, who regularly courts controversy. He had a poster up (and a recent paper) in which he stretched embryos even further, although I couldn’t find anyone to talk to about it. The team took two cell mouse embryos, split them in half and let each half grow into a new two-cell embryo. Then they split them again and repeated. And again. At each stage, they tested whether some of the embryos were able to develop further.
After the first split, 74% of cells grew into new embryos. But after each subsequent split, less of the cells were able to grow into a fresh embryo – as if their regenerative superpowers were slowly being sapped.
Hao struggled to tell me how her study could be used. Perhaps it means you can’t chop a human embryo in half (or in half again and again) and create artificial twins without consequences. Or something.
But I promised weird stuff with embryos and here it is.
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