Is there a germ line determinant?

Many aspects of germ line development are conserved among animal species. In most species, primordial germ cells (PGCs) are set aside early in development of the embryo and in species as diverse as Xenopus, Drosophila and C. elegans, PGCs form in a specialized cytoplasm, the germ plasm, which is synthesized during oogenesis. Germ cells generally arise at a position in the embryo separate from that of the primordium of the somatic gonad and migrate through different tissue to reach the somatic gonad. Eventually germ cells undergo meiosis and differentiate into either egg or sperm. Although many genes have been identified in various species that affect the development of germ cells, we understand little about what determines the germ cell's unique fate. Some genes such as vasa, nanos and DAZ/boule are specifically expressed in germ cells of many species including C elegans, Drosophila, zebrafish, Xenopus and mouse. However, the role these genes play in germ cell development may vary in different organisms. We will report on a series of extensive genetic screens to identify genes that affect germ cell formation and migration in Drosophila and will compare the conclusions derived from these studies to those obtained in other systems.