High resolution multi-scale profiling of embryonic germ cell-like cells derivation reveals pluripotent state transitions in humans
Primordial germ cells (PGCs) are the embryonic precursors of the gametes. In mice and rats, PGCs can readily acquire pluripotency in vitro by forming embryonic germ cells (EGCs). To date, a comparable in vitro system has not been established in humans, despite the fact that human PGCs (hPGCs) readily undergo pluripotent conversion in the context of germ cell tumorigenesis. Here we report that hPGC-like cells (hPGCLCs) undergo conversion to human embryonic germ-like cells (hEGCLCs) upon exposure to the same inductive signals previously used to derive mouse EGCs. This defined, feeder-free culture system allows efficient derivation of human EGCLCs which can be expanded and maintained in standard human pluripotent stem cell medium. hEGCLCs are transcriptionally similar to human pluripotent stem cells (hPSCs) and can differentiate into all three germ layers, as well as giving rise to PGCLCs once more - demonstrating the interconvertibility of pluripotent states. This is also evident at the epigenetic level, as the initial DNA demethylation that occurs in hPGCLCs is largely reversed in hEGCLCs, restoring DNA methylation to the level observed in hPSCs. This new in vitro model captures the transition from the pluripotent stem cell state to a germ cell identity and back again, and therefore represents a highly tractable system to study pluripotent and epigenetic transitions, including those which occur during human germ cell tumorigenesis. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=195 HEIGHT=200 SRC="FIGDIR/small/632914v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@14572bcorg.highwire.dtl.DTLVardef@6fa7c1org.highwire.dtl.DTLVardef@6eaa99org.highwire.dtl.DTLVardef@1822307_HPS_FORMAT_FIGEXP M_FIG C_FIG In briefWe report the first fully defined system to efficiently convert hPGCLCs to a pluripotent stem cell (PSC) state. We tracked pluripotent state transitions by multi-omic analysis and provided a high-resolution map of the transcriptional and epigenomic transitions upon entry to and exit from the human germline. HighlightsO_LIEfficient derivation of hEGCLC in fully defined feeder-free conditions C_LIO_LISingle-cell transcriptomic profiling of transitions from the hPSC state to hPGCLCs and back. C_LIO_LILongitudinal DNA methylation profiling highlights the overall reversibility of epigenetic states C_LIO_LIMulti-omic gene regulatory network analysis identifies key regulators of pluripotent transitions C_LI