Optical imaging of cell fusion and fusion proteins in Caenorhabditis elegans

Cell fusion is a very dynamic process in which the entire membrane and cellular contents of two or more cells merge into one. Strategies developed to understand the component processes that make up a full fusion event require imaging to be performed over a range of space and time scales. These strategies must cover detection of nanometer-sized pores, monitoring cytoplasmic diffusion and the dynamic localization of proteins that induce fusion competence, and three-dimensional reconstruction of multinucleated cells. Caenorhabditis elegans' small size, predictable development, and transparent body make this organism optimal for microscopic investigations. In this chapter, focus is placed on light microscopy techniques that have been used thus far to study developmental fusion events in C. elegans and the insights that have been gained from them. There is also a general overview of the developmental timing of the cell fusion events. Additionally, several protocols are described for preparing both fixed and live specimens at various developmental stages of C. elegans for examination via optical microscopy.