Reserch Projects


 Fertilization is an intercellular recognition event between sperm and eggs, which elicits genetic diversity in the next generation. This event consists of several processes such as a species- and allo-recognition process between sperm and egg-coats, a sperm penetration through a vitelline coat, fusion of plasma membrane and fusion of pronuclei. Fusion of cells of the same species and different individuals is a characteristic phenomenon in life. We are focusing on the molecular mechanisms of fertilization by biochemical and molecular biological approaches. Mainly we use ascidians and sea urchins as the experimental marine animals, and attempt to elucidate the role of sperm proteases and the novel extracellular ubiquitin-proteasome system in fertilization and gametegenesis. Although ascidians are generally hermaphrodite and spawning eggs and sperms nearly simultaneously, several species, including Halocynthia roretzi and Ciona intestinalis, are strictly self-sterile. We are very interested in these phenomena and we are now investigating the molecular mechanisms how non-self cells are recognized in ascidians regardless of the lack of the acquired immune system such as MHCs or antibodies.

Molecular Mechanisms of Fertilization


Self/nonself-Recognition Systems in Ascidians


Ubiquitin-Proteasome System






Recent Publication