[
Nature,
1996]
Classical results in experimental embryology established long ago that cells of the developing animal have a regional identity. They can be characterized not only as 'skin', 'nerve' and 'bone', but also as 'arm' and 'leg'. But how cells know what body region they belong to, and what to do there, is not known. Results reported in this issue and in Development describe unexpected properties of a key player, one of the Hox genes-the dynamic, lineage-based regulation of a Hox gene in the nematode Caenorhabditis elegans is at odds with a traditional view of Hox genes as relatively fixed markers of regional identity.
[
Nature,
1999]
Animal evolution is commonly viewed as producing diverse, environmentally adapted bodies to propagate the germ line. The evolutionary theory of ageing suggests that genetic limits to lifespan may be inadvertent consequences of evolutionary selection for maximizing that propagation. In other words, trade-offs occur that favour reproductive success over post-reproductive longevity; lifespan should be inversely correlated with fecundity when progeny production diverts resources from the maintenance of somatic (non-reproductive) cells. The germ line contains all the genetic information to specify the soma. But it is also possible that there are other, environmentally modulated instructions for life history that the germ line conveys to the soma to maximize reproduction.
[
Science,
1996]
Geoffrey Gold, a physiologist at the Monell Chemical Senses Center in Philadelphia, had wanted for years to put to rest a nagging question: How do odors trigger olfactory neurons to fire off action potentials to the brain? The dogma for the past 5 years had been that odors fall into two catagories, each of which acts via a different inracellular messenger molecule. But Gold believed this view was wrong, and that all odors work by increasing the production of the intracellular messenger cyclic AMP (cAMP). One day last spring, Gold got a phone call out of the blue from neurobiologist John Ngai, at the University of California (UC), Berkeley, offering the possibility of answering this question. It was my dream come true," says Gold. ......
[
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