[
Science,
1984]
The end of 1983 saw the completion of a major project in developmental biology. All the cell divisions, deaths, and migrations that generate the embryonic, then the larval, and finally the adult forms of the roundworm Caenorhabditis elegans have now been traced. It is the first time the complete cell lineage of an organism of this degree of complexity, one that contains many of the diverse cell types found in all higher animals, has been determined.
[
New York Times,
1991]
Through a microscope, they look like tiny crystal serpents, curving and slithering across the dish with an almost opiated languor, doubling back on themselves as though discovering their tails for the first time, or bumping up against a neighbor clumsily and then slowly recoiling. Beneath their translucent skin the pulsing muscle cells and nerve fibers are clearly visible, a sight so strange and so exquisite that it is hard to believe these creatures are common roundworms, found in gardens and compost heaps everywhere. And it is harder still to believe that such slippery squiggles of life are fast changing the face of fundamental biology.
[
Nature,
2001]
In all animals, the process of programmed cell suicide (apoptosis) is coordinated by enzymes known as caspases, which cut up key substrates in the cell. The dying cell is then neatly packaged, engulfed by neighbouring "phagocytic" cells, and cleared from the body without fanfare, leaving no evidence of the catastrophic events that preceded. It has always been assumed that there is a "point of no return" in this death cascade - at or shortly before the time at which caspases are activated - beyond which the process of cell execution proceeds inexorably. This view is challenged by Reddien et al. and Hoeppner et al. on pages 198 and 202 of this issue. It seems that cells in which caspases have been activated can in fact progress through a state of being "mostly dead", a stage that physically resembles the early phase of apoptosis but from