Importance of WNT-dependent signaling for derivation and maintenance of primed pluripotent bovine embryonic stem cells†

Abstract

The WNT signaling system plays an important but paradoxical role in the regulation of pluripotency. In the cow, IWR-1, which inhibits canonical WNT activation and has WNT-independentactions, promotes the derivation of primed pluripotent embryonic stem cells from the blastocyst.Here, we describe a series of experiments to determine whether derivation of embryonic stem cellscould be generated by replacing IWR-1 with other inhibitors of WNT signaling. Results confirmthe importance of inhibition of canonical WNT signaling for the establishment of pluripotentembryonic stem cells in cattle and indicate that the actions of IWR-1 can be mimicked by theWNT secretion inhibitor IWP2 but not by the tankyrase inhibitor XAV939 or WNT inhibitoryprotein dickkopf 1. The role of Janus kinase-mediated signaling pathways for the maintenanceof pluripotency of embryonic stem cells was also evaluated. Maintenance of pluripotency ofembryonic stem cells lines was blocked by a broad inhibitor of Janus kinase, even though the cellsdid not express phosphorylated signal transducer and activator of transcription 3 (pSTAT3). Furtherstudies with blastocysts indicated that IWR-1 blocks the activation of pSTAT3. A likely explanationis that IWR-1 blocks differentiation of embryonic stem cells into a pSTAT3+ lineage. In conclusion,results presented here indicate the importance of inhibition of WNT signaling for the derivationof pluripotent bovine embryonic stem cells, the role of Janus kinase signaling for maintenance ofpluripotency, and the participation of IWR-1 in the inhibition of activation of STAT3.