Cytokeratin filaments from a major cytoskeletal system in the Xenopus oocyte and early embryo. Using wholemount immunocytochemistry Dr. klymkowsky has discovered a dramatic asymmetry in the organization of cytokeratin filaments in both the oocyte and early embryo. During oocyte maturation cytokeratin filaments break down. Cytokeratin breakdown appears to be regulated post-translationally and is induced by maturation promoting factor (MPF). Dr. Klymkowsky will determine whether MPF acts directly or indirectly to disrupt cytokeratin organization using an in vitro assay system. With fertilization cytokeratin filaments reform; this asymmetrically organized embryonic cytokeratin system persists until the end of gastrulation. To define the function of cytokeratin filaments in the embryo, he will develop new monoclonal anticytokeratin antibodies. The epitopes of these antibodies will be mapped on the cytokeratin protein and its effects on cytokeratin filament integrity and embryonic development will be determined. This will enable him to define regions of the cytokeratin molecule involved in cytokeratin filament organization and function. Dr. Klymkowsky has already identified two monoclonal anticytokeratin antibodies that specifically disrupt normal gastrulation in Xenopus. To define further the mechanism by which these antibodies act, he will use light and electron microscopy to characterize the movement and morphology of cells during gastrulation and immunocytochemistry to examine cytokeratin organization within the embryo. Injection of antibodies into specific blastomeres will be used to determine the regions of the gastrulating embryo affected by these antibodies. Together these studies offer an opportunity for defining the functions of cytokeratins, understanding how their organization if controlled and for furthering our understanding of the major morphogenetic event of vertebrate development, gastrulation. %%% One of the most dramatic events during the maturation of the egg in the amphibian, Xenopus is the reorganization of the subcellular cytokeratin-type intermediate filaments. The resulting mature egg is asymmetric and this asymmetry defines the axis of the mature organism. Clearly the events leading to the setting up of this polarity are key events in development.
