Cell fusion is an important naturally occurring process crucial for proper development. This process includes the fusion of sperm and oocytes during fertilization as well as the fusion of several mononuclear cells to form a syncytium. Throughout development in C. elegans 300 of the 1090 somatic cells born, undergo cell fusion. Cell fusion is not required for the proper differentiation of a cell, failure of cell fusion can result in animals with defects in morphology, behavior, or fertility. Although there is fusion among many different types of cells, the initial fusion of cell membranes in all cases requires one gene in particular,
eff-1. Cell fusion is a well studied process in C. elegans and data supports a model where cells are by nature destined to fuse but developmental regulation at the level of transcription and post-translation prevent this program from occurring.