Fig. 3

β-Catenin-independent transactivator activity of Tcf7l1 contributes to cardiomyocyte programming. a Genetic elements in Tcf7l1-teton ESCs. Endogenous Tcf7l1 alleles are null. Reverse tetracycline-controlled transactivator (rtTA) transgene driven by CMV promoter. Tcf7l1 transgene driven by tetracycline responsive promoter TRE-CMV. In presence of tetracycline/doxycycline, Tcf7l1 transgene is transactivated. Four versions of Tcf7l1 (wt, Tcf7l1dN, Tcf7l1-En, and Tcf7l1-VP16) transgenes compared. b Western blot confirmation of transgene induction by 24-h supplemental dox. c Scheme of dox supplementation. d Tcf7l1dN and Tcf7l1-VP16 augmented formation of α-Actinin-positive cardiomyocytes. e Representative α-Actinin staining results of (c). f Tcf7l1dN and Tcf7l1-VP16 upregulated Nkx2–5 expression, whereas Tcf7l1-En downregulated it. Nkx2–5 gene expression assayed by real-time RT-PCR. N ≥ 3; *p < 0.05 versus control cells. CMV cytomegalovirus, DAPI 4′,6-diamidino-2-phenylindole, wt wildtype