Immunocytochemical localization of a follicle specific protein of the hawkmoth Manduca sexta

Abstract A follicle specific protein (FSP-I) from the hawkmoth Manduca sexia , has been localized in developing follicles by immuno-fluorcscence and immuno-gold labeling techniques. At the light microscopical level, the protein was demonstrated to be present in both the basolateral and apical parts of foilicular epithelial cells, as well as in clearly defined, spherical compartments in the cortex of the developing oocyte. Immuno-gold labeling at the electron microscopical level revealed the localization of FSP-I in cndoplasmic compartments of the foilicular epithelial cells, in the extracellular matrix of the follicle and in endocytic compartments of the oocyte. Our results indicate that M. sexta FSP-I is synthctizcd and secreted by the foilicular epithelial cells, after which it is taken up by the developing oocyte through endocytic routes.