When communal cell death fails in mutant chimeric flies, epithelial tissue remains in patches (circled) across the wing.

Mass suicides are not the reserve of cults, it appears. On page 567, Link and colleagues report that cells do it too.

Cellular suicide—known as apoptosis—is necessary during development for sculpting the shape of organs and limbs. Most of the time, individual cell suicides are dotted throughout the tissue, and cell corpses are then cleared away by phagocytosis.

Link et al., however, have now captured by live imaging a mass cellular suicide in flies. Epithelial wing cells died in a wave that swept across the developing wing in a matter of minutes. The dead cells were not phagocytosed but were instead swept into the wing veins, which drain into the body.

The authors hypothesize that a released signaling factor or mechanosensory response propagates the swift en masse suicides. A mutant screen for defects in this collective cell death has not yet identified any such instigators but has revealed novel cell death genes, including homeodomain-interacting protein kinase. This gene's product functions in collective cell death and in more conventional examples of programmed cell death.

The authors speculate that communal cell death might be a more widespread phenomenom. Massive cellular suicides might occur, for example, in mammals during development or after rapid hormonal changes, such as mammary gland involution after nursing and the shedding of the uterine lining at menstruation.