IMMUNOCYTOCHEMICAL LOCALIZATION OF A FOLLICLE SPECIFIC PROTEIN OF THE HAWKMOTH MANDUCA-SEXTA

A follicle specific protein (FSP-I) from the hawkmoth Manduca sexta, has been localized in developing follicles by immuno-fluorescence and immune-gold labeling techniques. At the light microscopical level, the protein was demonstrated to be present in both the basolateral and apical parts of follicular 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 endoplasmic compartments of the follicular 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 synthetized and secreted by the follicular epithelial cells, after which it is taken up by the developing oocyte through endocytic routes.