Primordial germ cell specification: the importance of being 'blimped'.

In mouse embryos, the expression of Blimp1 has recently revealed a population of allocated primordial germ cell precursors 24 hours earlier than previously thought. Those 'blimped' precursors have been shown to give rise, by mitotic division, to germ cells only and no other cell lineages. Here, we try to understand the events that lead to Blimp1 expression in the primordial germ cell precursors and speculate on what can be the role of Blimp1 during primordial germ cell specification and gastrulation in the mouse. Finally, we discuss the possible involvement of Blimp1 in the two know modes of germ line segregation (epigenesis and preformation).