Immunostaining for markers of apoptosis in the Caenorhabditis elegans germline

The transparency of Caenorhabditis elegans makes it an ideal organism for visualizing proteins by immunofluorescence microscopy; however, the tough cuticle of worms and the egg shell surrounding embryos pose challenges in achieving effective fixation so that antibodies can diffuse into cells. In this protocol, we describe immunostaining of apoptosis-related proteins in the C. elegans adult germline using fluorescent reagents. Protein localization and abundance can be determined in various mutant backgrounds and under a variety of conditions, such as exposure to genotoxic stress. The number of antibodies specific to C. elegans proteins is quite limited compared with other organisms, but there is a growing list of immunological reagents directed against proteins in other organisms that cross-react with the homologous C. elegans proteins.