During oocyte development in insects, the oocytes accumulate yolk proteins through endocytosis in a process called vitellogenesis. Anderson and Woodruff analyzed endocytic uptake in ovarioles from Oncopeltus fasciatus. The presence of electrical coupling betweeen the epithelium and oocytes was confirmed in vitellogenic oocytes and previtellogenic oocytes. However, only during the vitellogenic stage of oogenesis are the gap junctions opened sufficiently to allow dye coupling between the two cells. Closure of the gap junctions with pharmacological agents or by acidification of the cells inhibited endocytosis, detected as the uptake of fluorescent dextran-containing blood. Endocytosis resumed under conditions in which the gap junctions were inhibited if the oocytes were injected with epithelial cell cytoplasm. Thus, epithelial cells produce a factor that is transmitted to the oocytes through the gap junctions that stimulates oocyte endocytosis. The fact that the gap junctions do not open until just before vitellogenesis suggests that the regulation of signaling between the cells may be through the regulation of the opening and closure of the gap junctions. For more information about signals that can regulate gap junctions see the Perspective by Hossain in the STKE Archive.
K. L. Anderson, R. I. Woodruff, A gap junctionally transmitted epithelial cell signal regulates endocytic yolk uptake in Oncopeltus fasciatus. Dev. Biol. 239, 68-78 (2001). [Online Journal]
M. Z. Hossain, A. L. Boynton, Regulation of Cx43 gap junctions: The gatekeeper and the password. Science's STKE (2000), http://stke.sciencemag.org/cgi/content/full/OC_sigtrans;2000/54/pe1. [Abstract] [Full Text]