Cell to cell communication plays an essential role during pattern formation and morphogenesis of the diverse tissues and organs of the body. In invertebrates, such as the fruitfly Drosophila, the direct communication of closely apposed cells is mediated by gap junctions which are composed of oligomers of the innexin family of transmembrane channel proteins. Few data exist about the developmental role of the eight innexin genes which have been found in the Drosophila genome. We have investigated the role of the innexin 2 and ogre genes during gastrointestinal development of the fly embryo. Our findings suggest that innexins are involved in the formation of the proventriculus, an organ that develops at the foregut/midgut boundary by migration of primordial cells and subsequent infolding of epithelial tissue layers.