The story of cell fusion: big lessons from little worms

The ability of two or more cells to unite to form a new syncytial cell has been utilized in metazoans throughout evolution to form many complex organs, such as muscles, bones and placentae. This requires migration, recognition and adhesion between cells together with fusion of their plasma membranes and rearrangement of their cytoplasmic contents. Until recently, understanding of the mechanisms of cell fusion was restricted to fusion between enveloped viruses and their target cells. The identification of new factors that take part in developmental cell fusion in C. elegans opens the way to understanding how cells fuse and what the functions of this process are. In this review, we describe current knowledge on the mechanisms and putative roles of developmental cell fusion in C. elegans and how cell fusion is regulated, together with other intercellular processes to promote organogenesis.