Activin A in Combination with ERK1/2 MAPK Pathway Inhibition Sustains Propagation of Mouse Embryonic Stem Cells

Activin/Nodal/TGF-β signaling pathway plays a major role in maintaining mouse epiblast stem cells (mEpiSCs). The mEpiSC medium which contains Activin A and bFGF induces differentiation of mouse embryonic stem cells (mESCs) to mEpiSC. Here we show that Activin A also has an ability to efficiently propagate mESCs without differentiation to mEpiSCs when combined with a MEK inhibitor PD0325901. mESCs cultured in Activin+PD retained high-level expression of naive pluripotency-related transcription factors. Genome-wide analysis revealed that the gene expression profile of mESCs cultured in Activin+PD resembles that of mESCs cultured in 2i. mESCs cultured in Activin+PD also showed features which are related to naive pluripotency of mESCs, including the preferential usage of the Oct4 distal enhancer and the self-renewal response to Wnt pathway activation. Our finding reveals a role of Activin/Nodal/TGF-β signaling in stabilizing self-renewal gene regulatory networks in mESCs. To compare the gene expression patterns of mESCs cultured in Activin+PD, 2i and LIF+BMP4 and mEpiSCs, we performed genome-wide gene expression analysis by using Affymetrix GeneChip oligonucleotide microarrays Total RNA was isolated with RNeasy Mini kit (Invitrogen). During the isolation, on-column DNaseI digestion was performed. Biotinylated sense-strand DNA was synthesized with GeneChip WT PLUS Reagent kit (Affymetrix), hybridized to Mouse Gene 2.0 ST Array (Affymetrix) and analyzed by GeneChip Scanner 7G System (Affymetrix). The data were analyzed by GeneSpringGX11.5 software (Agilent).