Tcf3 Regulates Embryonic Stem Cell Pluripotency and Self-Renewal by the Transcriptional Control of Multiple Lineage Pathways

¹ Stem Cell and Developmental Biology, Genome Institute of Singapore, 60 Biopolis Street, Singapore
² Bioinformatics Institute, 30 Biopolis Street, Singapore
³ Stem Cell and Developmental Biology, Genome Institute of Singapore, 60 Biopolis Street, Singapore; Harvard Institutes of Medicine, Harvard Medical School, Boston, MA 02115, USA

^* To whom correspondence should be addressed. E-mail: limb1{at}gis.a-star.edu.sg.

	Abstract

The Wnt signaling pathway is necessary both for maintaining undifferentiated stem cells, as well as directing their differentiation. In mouse embryonic stem cells (ESCs), Wnt signaling preferentially maintains ‘stemness’ under certain permissive conditions. Tcf3 is a component of the Wnt signaling and a dominant downstream effector in ESCs. Despite the wealth of knowledge regarding the importance of Wnt signaling underlying stem cells functions, the precise mechanistic explanation by which the effects are mediated is unknown. In this study, we identified new regulatory targets of Tcf3 using a whole genome approach and found that Tcf3 transcriptionally represses many genes important for maintaining pluripotency and self-renewal, as well as those involved in lineage commitment and stem cell differentiation. This effect is in part mediated by the co-repressors TLE2 and CtBP. Notably, Tcf3 binds to and represses the Oct4 promoter, and this repressive effect requires both the Groucho and CtBP interacting domains of Tcf3. Interestingly, we find that in mouse pre-implantation development embryos, Tcf3 expression is co-regulated with Oct4 and Nanog, and becomes localized to the inner cell mass of the blastocyst. These data demonstrate an important role for Tcf3 in modulating the appropriate level of gene transcription in ESCs, and during embryonic development.