Mature mouse gametes can be traced back to a small population of cells in the embryo known as primordial germ cells (PGCs). The PGC-specific expression of the his-tochemical marker alkaline phosphatase has led to a description of their embryonic development. At 7 days postcoitus (dpc), PGCs are located caudal to the primitive streak, near the base of the allantois. These cells migrate through the dorsal mesentery and enter the developing fetal gonad, the genital ridge, between 10.5 and 12.5 dpc. This period of migration is accompanied by rapid proliferation, with an estimated doubling time of 16 h. By 13.5 dpc, the final population of approximately 25 000 germ cells is present in the genital ridges. In the male, germ cells enter a mitotic arrest, while in females, germ cells arrest at meiotic prophase I.
PGCs can be transiently cultured on feeder layers expressing the transmembrane-bound isoform of steel factor (SLF), the product of the murine Sl locus. SLF, together with leukemia inhibitory factor (LIF), promotes PGC survival by suppressing apoptosis. Basic fibroblast growth factor (bFGF) is also active in PGC cultures, promoting germ cell proliferation. If PGCs are cultured with SLF, LIF, and bFGF, they can form permanent cell lines, termed embryonic germ (EG) cells. EG cells share many properties with embryonic stem cells, including the ability to colonize the germ line. Cheap Diskus Advair
We have undertaken a more thorough examination of the effects of bFGF in PGC culture, both to better understand the role of fibroblast growth factors (FGFs) in PGC development and to expedite the isolation of EG cell types from other species. Our results strongly suggest that bFGF can work directly on PGCs, as opposed to an indirect effect exerted through the feeder layer or through somatic cells plated along with PGCs. Moreover, mitotic PGCs express an FGF receptor activity. FGF-binding activity appears to be regulated in a developmental- and sex-specific manner.