SETD3 regulates endoderm differentiation of mouse embryonic stem cells through canonical Wnt signaling pathway.

With self-renewal and pluripotency features, embryonic stem cells (ESCs) provide an invaluable tool to investigate early cell fate decisions. Pluripotency exit and lineage commitment depend on precise regulation of gene expression that requires coordination between transcription (TF) and chromatin factors in response to various signaling pathways. SET domain-containing 3 (SETD3) is a methyltransferase that can modify histones in the nucleus and actin in the cytoplasm. Through an shRNA screen, we previously identified SETD3 as an important factor in the meso/endodermal lineage commitment of mouse ESCs (mESC). In this study, we identified SETD3-dependent transcriptomic changes during endoderm differentiation of mESCs using time-course RNA-seq analysis. We found that SETD3 is involved in the timely activation of the endoderm-related gene network. The canonical Wnt signaling pathway was one of the markedly altered signaling pathways in the absence of SETD3. The assessment of Wnt transcriptional activity revealed a significant reduction in Setd3-deleted (setd3∆) mESCs coincident with a decrease in the nuclear pool of the key TF β-catenin level, though no change was observed in its mRNA or total protein level. Furthermore, a proximity ligation assay (PLA) found an interaction between SETD3 and β-catenin. We were able to rescue the differentiation defect by stably re-expressing SETD3 or activating the canonical Wnt signaling pathway by changing mESC culture conditions. Our results suggest that alterations in the canonical Wnt pathway activity and subcellular localization of β-catenin might contribute to the endoderm differentiation defect of setd3∆ mESCs.