Characteristics of murine primordial germ cells and their relation with hemopoiesis.

Primordial germ cells (PGC) are a population of cells characterised by a po sitive reaction to alkaline phosphatase, usually present in the mouse embry o at 7.5 days post coitum (dpc). These cells migrate through various tissue s before they become incorporated into the gonadal ridges. Hematopoiesis is a complex developmental system in which the hemopoietic stem cells (HSC) w ere experimentally shown to have been derived from a single multipotent ste m call. PGC, as well as HSC are regulated by a range of growth factors that control both proliferative and differentiative processes. Leukemia inhibit ory factor (LIF) is a cytokine that regulates the differentiation and the t otipotentional phenotype of PGC. Recently, other growth factors, such as st em cell factor (SCF), macrophage growth factor (MGF), and forskolin (FRKL) have been proposed as the possible in vivo and in vitro regulators for PGCs and HSCs. Induction of hematopoiesis in an embryonic germ cell derived fro m PGCs indicates that germ cells acquire the potentiality to differentiate toward hematopoietic cells. The coincidental presence of both PGCs and HSCs at the sites where early hemopoiesis is established, together with similar growth factor requirements support the hypothesis that PGCs may also be co nsidered hemopoiesis initiating cells.