Exocytosis, endocytosis, and development.

During development, metazoans are faced with the daunting task of generating many different cell types in a temporally and spatially precise manner. This orderly process of cell generation relies on creating localized signals that activate or inhibit specific cellular pathways. Recent work has shown that some of these localized signals require the targeted secretion of proteins, or their uptake by endocytosis. The importance of these protein trafficking pathways in localized signal generation is further substantiated by endo- and exocytosis mutants which can phenocopy many developmental mutants. Genetic and molecular techniques that increase our ability to inhibit exocytosis and endocytosis in a temporal and cell-type specific manner are likely to further elucidate the complexities of development.