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| Nadav Sharon in his lab. (Photo by the Hebrew University of Jerusalem) |
How is it that a disc-like cluster of cells transforms within the first month of pregnancy into an elongated embryo? This mechanism is a mystery that man has tried to unravel for millennia.
The first significant step towards understanding the issue was made nearly a century ago in experiments conducted by the German embryologists Hans Spemann and Hilde Mangold. The two used early newt embryos and identified a group of cells within them which, upon transplantation, formed a two-headed tadpole.
In trying to understand why this happened, they concluded that what occurred is that the transplanted cells organized the vicinity into which they were placed to form a typical embryonic shape. They therefore dubbed such cells “organizer” cells. The newt embryo possessed both its own organizers and the transplanted ones, both of which organized nearby cells to form a head structure.
