The Trans‐Spliced Long Noncoding RNA tsRMST Impedes Human Embryonic Stem Cell Differentiation Through WNT5A‐Mediated Inhibition of the Epithelial‐to‐Mesenchymal Transition

The trans‐spliced noncoding RNA RMST (tsRMST) is an emerging regulatory lncRNA in the human pluripotency circuit. Previously, we found that tsRMST represses lineage‐specific transcription factors through the PRC2 complex and NANOG in human pluripotent stem cells (hESCs). Here, we demonstrate that tsRMST also modulates noncanonical Wnt signaling to suppress the epithelial‐to‐mesenchymal transition (EMT) and in vitro differentiation of embryonic stem cells (ESCs). Our results demonstrate that disruption of tsRMST expression in hESCs results in the upregulation of WNT5A, EMT, and lineage‐specific genes/markers. Furthermore, we found that the PKC inhibitors Go6983 and Go6976 inhibited the effects of WNT5A, indicating that WNT5A promotes the EMT and in vitro differentiation although conventional and novel PKC activation in hESCs. Finally, we showed that either antiserum neutralization of WNT5A or Go6983 treatment in tsRMST knockdown cells decreased the expression of mesenchymal and lineage‐specific markers. Together, these findings indicate that tsRMST regulates Wnt and EMT signaling pathways in hESCs by repressing WNT5A, which is a potential EMT inducer for promoting in vitro differentiation of hESCs through PKC activation. Our findings provide further insights into the role of trans‐spliced RNA and WNT5A in hESC differentiation, in which EMT plays an important role. Stem Cells 2016;34:2052–2062 In hESCs, tsRMST forms a complex with NANOG and SUZ12 to repress noncanonical Wnt ligand WNT5A. When the tsRMST complex is downregulated, differentiation‐related transcription factors are activated to promote differentiation, and activated WNT5A further strengthens differentiation via EMT through activating the PKC cascade.