Primordial germ cells (PGCs), that are greatly similar to embryonic stem cells (ES) in term of their gene expression profile, appear very different from other types of multipotent stem cells in chromatin level. H3K9me2, which is under direct control of G9 a and its partner GLP, is dramatically decreased in the PGC genome. We designed a polycistronic lentiviral vector for simultaneous overexpression of Stella, Oct4 and Nanos2 in recipient cells. This resulted in increased mRNA expression of Prdm14 and Nanog, and decreased G9a mRNA expression. We consider these findings as a primary step for reprogramming the recipient cells towards germline progenitor cells. We propose that the level of this histone modification pattern could be decreased as a consequence of G9a downregulation. Decreasing the level of H3K9me2 as a critical step for facilitating transition between the different stemness states, creating a new epigenetic memory for the early germ cells.

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