The distribution of clathrin during amphibian oogenesis

The distribution and content of clathrin during amphibian oogenesis was studied by indirect immunofluorescence and competitive ELISA assays. The antibody used for these studies was specific for the clathrin heavy chain and was capable of recognizing the antigen in a crude homogenate of amphibian oocytes. When this antibody was used to localize clathrin in fixed tissue slices of HCG-stimulated ovaries, differences were detected in the staining patterns of various sized oocytes. In cells less than 0.5 mm in diameter, the reaction appeared as a punctate pattern throughout the cytosol with a less intense reaction occurring in the region of the oolemma. As cell size increased, the intensity of the stain associated with the oolemma also increased, and the cytosolic reaction correspondingly decreased. To determine if this difference in intensity was due to an increase in clathrin concentration, competitive ELISA assays were carried out on extracts of variously sized oocytes. The results indicate that clathrin is preferentially synthesized in differently sized oocytes and that changes in the distribution and content of clathrin during oogenesis are related to developmental events occurring as the oocyte becomes progressively more specialized.