Use of InSTAT3 KO ESCs to study mesoderm lineage differentiation. (a) Schematic diagram of experimental strategy was illustrated here. (b) Size and morphologies of EBs in unstimulated EBs (Dox -) and STAT3 KO EBs (Dox +). Following STAT3 deletion, the size of STAT3 KO EBs (Dox +) was not significantly different compared to unstimulated EBs (Dox -), suggesting that STAT3 has no effect on the cell growth and morphology of EBs formed when STAT3 was deleted. (c) Deletion of STAT3 led to significant reduction in the expression of mesodermal markers when STAT3 was deleted from day 0 onwards of cardiomyocyte differentiation of ESCs. Number of EB clones used for qPCR was 30 EBs at each time point.