GSK-3 signaling is involved in proliferation of chicken primordial germ cells

Primordial germ cells (PGCs) are precursors of sperms and oocytes and responsible for passing the genetic information from one generation to the next. Chicken PGCs segregate from somatic cells in early embryo and could be isolated and cultured in vitro, making it a useful tool to produce genetically modified animals. However, the number of PGCs isolated from embryo is limited and these cells are not efficient to proliferation in vitro. GSK-3 plays an important role in multiple intracellular signaling pathways and inhibition of GSK-3-mediated β-catenin phosphorylation is known to reduce apoptosis and promote proliferation in T cells and embryo stem cells (ESC). In this study, we investigate the effect of GSK-3 inhibitor on the proliferation of PGCs in vitro and found significant increases of cell proliferation in the culture supplemented with CHIR. We further found that CHIR regulates PGC cell cycle by activating Wnt signaling and antagonizing the apoptosis of PGCs by inhibition of the expression of caspase-3 and Beclin-1. PGCs treated with CHIR expressed the germ cell-related markers and retain the capability to colonize the embryonic gonad after re-introduction to vasculature of HH stage-15 embryos. These results suggest that GSK-3 is involved in cell renewal and apoptosis in chicken PGCs.