The life of many multicellular organisms begins with the union (fertilization) of germ cells (the eggs and the spermatozoa). The processes during which the spermatozoa and eggs are produced are called spermatogenesis and oogenesis, respectively. These processes are indispensable for organisms that use sexual reproduction to maintain the species beyond the limited life of individuals. In contrast to the somatic cells that compose and maintain the organisms, the germ cells function to extend life to the next generation. The eggs and spermatozoa are highly differentiated cells, but in some aspects they are undifferentiated cells that retain the ability to become various kinds of cells. The germ cells thus mysteriously have the properties of being both differentiated and undifferentiated, and with the aid of these cells, organisms can maintain the species.
In addition to the contribution of germ cells to the continuity of life, the recombination of genes during oogenesis and spermatogenesis and the blending of genes by fertilization give diversity to organisms. Consequently, the germ cells are responsible for both the continuity and the diversity of life. Investigations into the mechanisms by which the germ cells are produced and fertilized should lead to an understanding of the mechanisms that assure two major contradictory characteristics of life: being able to reproduce those equal to the self and to produce those different from the self.
Our laboratory was established in 1993 for studying gametogenesis, gamete maturation, and fertilization, using fish and amphibians as experimental animals. Our research effort in recent years concentrates on the following four subjects.