The co-occupancy of Tcf3 with Oct4, Sox2 and Nanog on embryonic stem cell (ESC) 
chromatin indicated that Tcf3 has been suggested to play an integral role in a 
poorly understood mechanism underlying Wnt-dependent stimulation of mouse ESC 
self-renewal of mouse ESCs. Although the conventional view of Tcf proteins as 
the β-catenin-binding effectors of Wnt signalling suggested Tcf3-β-catenin 
activation of target genes would stimulate self-renewal, here we show that an 
antagonistic relationship between Wnt3a and Tcf3 on gene expression regulates 
ESC self-renewal. Genetic ablation of Tcf3 replaced the requirement for 
exogenous Wnt3a or GSK3 inhibition for ESC self-renewal, demonstrating that 
inhibition of Tcf3 repressor is the necessary downstream effect of Wnt 
signalling. Interestingly, both Tcf3-β-catenin and Tcf1-β-catenin interactions 
contributed to Wnt stimulation of self-renewal and gene expression, and the 
combination of Tcf3 and Tcf1 recruited Wnt-stabilized β-catenin to Oct4 binding 
sites on ESC chromatin. This work elucidates the molecular link between the 
effects of Wnt and the regulation of the Oct4/Sox2/Nanog network.