Migration,proliferation and potency of primordial germ cells

In most species, the cells allocated to the germ line, the primordial germ cells (PGCs) arise very early in embryo-genesis, and migrate to join the somatic cells at the site where the gonad will form. In three widely studied animals; the mouse, the frog and Drosophila, the PGCs associate with the developing gut, from which they migrate during the period of organogenesis to the gonads. During this migration, the germ cell population increases by an amount which is more or less constant for a particular species. Genes important in the control of PGC migration and population are being identified in two ways. In invertebrates, and to a lesser extent in mice, genetic approaches have identified important loci or gene products. Culturing PGCs in a variety of conditions has been an alternative approach in mouse embryos. From these latter studies, it is now known that a number of growth factors, released from surrounding tissues, control many aspects of PGC behaviour, including their proliferation, migration, potency, and survival. Attention is also focusing on changes in PGC adhesiveness during migration.