Visualizing apoptosis in embryos and the germline of Caenorhabditis elegans

Visualizing apoptosis in developing embryos or the germline of Caenorhabditis elegans is remarkably easy because of the transparency of the organism. The invariant pattern of cell division and programmed cell death during development makes it possible to quantify small but reproducible changes in apoptosis, which are easy to detect by light microscopy because of the refractile properties of dying cells. Although apoptotic death is easy to visualize and quantify in the germline of adult hermaphrodites, the pattern of cell death is variable, especially when triggered by stress. The most convenient method for visualization of apoptosis in vivo is light microscopy, which requires immobilizing live embryos or adult animals on slides. This protocol describes the basic methods for visualizing and analyzing apoptosis in living animals.