[
Nature,
2001]
The degredation of DNA is one of the hallmarks of programmed cell death (apoptosis). When forced to commit suicide, apoptotic cells - like good secret agents - grimly destroy their "instruction book," chewing up their genomic DNA into tiny morsels. Until now, only two DNA-destroying enzymes (nucleases) with a clear role in cell death were known, one in mammals and one in the nematode worm Caenorhabditis elegans. But, on pages 90-99 of this issue, Li and colleagues and Parrish and co-workers show that another nuclease, endonuclease G (endoG), also contributes to the carnage, and might even influence the likelihood that a cell will live or die.
[
Dev Cell,
2002]
Presenilins mediate they-secretase cleavage of Notch transmembrane receptors as well as the transmembrane P-amyloid precursor protein (PAPP), but they are not thought to accomplish this alone. Recent genetic screens in C. elegans, presented in this issue of Developmental Cell, identify two genes that are essential to gamma-secretase activity and may interact with presenilins.
[
J Cell Biol,
2007]
Cells must break symmetry to acquire polarity. Microtubules have been implicated in the induction of asymmetry in several cell types, but their role in the Caenorhabditis elegans zygote, a classic polarity model, has remained uncertain. One study (see Tsai and Ahringer on p. 397 of this issue) brings new light to this problem by demonstrating that severe loss of microtubules impairs polarity onset in C. elegans.