Tripartite Inhibition of SRC-WNT-PKC Signalling Consolidates Human Naive Pluripotency
Different conditions have been devised to isolate MEK/ERK signalling independent human naive pluripotent stem cells (PSCs) that are distinct from conventional primed PSCs and better correspond to pre-implantation developmental stages. While the naive conditions described thus far endow human PSCs with different extents of naivety features, isolating human pluripotent cells that retain characteristics of ground state pluripotency while maintaining differentiation potential and genetic integrity, remains a major challenge. Here we engineer reporter systems that allow functional screening for conditions that can endow both the molecular and functional features expected from human naive pluripotency. We establish that simultaneous inhibition of SRC-NF{kappa}B, WNT/{beta}CATENIN and PKC signalling pathways is essential for enabling expansion of teratoma competent fully naive human PSCs in defined or xeno-free conditions. Divergent signalling and transcriptional requirements for maintaining naive pluripotency were found between mouse and human. Finally, we establish alternative naive conditions in which MEK/ERK inhibition is substituted with inhibition for NOTCH/RBPj signalling, which allow obtaining alternative human naive PSCs with diminished risk for loss of imprinting and deleterious global DNA hypomethylation. Our findings set a framework for the signalling foundations of human naive pluripotency and may advance its utilization in future translational applications. Highlights of key findingsO_LICombined inhibition of SRC, WNT and PKC signaling consolidates human naive pluripotency C_LIO_LIStable expansion of DNA/RNA methylation-independent and TGF/ACTIVIN-independent human naive PSCs C_LIO_LIOpposing roles for ACTIVIN and WNT/{beta}CATENIN signaling on mouse vs. human naive pluripotency C_LIO_LI2i and MEK/ERKi independent alternative human naive PSC conditions via inhibiting NOTCH/RBPj signaling C_LI