Starved mouse CPCs were treated with S1P (3µM) for 3 days and Mef2C, GATA4 and GATA6 expression levels were measured by qPCR. Fold changes over control at time 0 are graphed. Pharmacological inhibition (10µM, CCG-293971) (A) or silencing (B) of MRTF-A attenuate the effect of S1P on cardiac gene expression. *p≤0.05, **p≤0.01, ***p≤0.005 vs. S1P treated by unpaired t-test; n=8, 3 independent experiments. (C) CPCs were transfected with a plasmid encoding MRTF-A (0.5 µg). Overexpression of MRTF-A for 48 hours induced cardiac gene expression in CPCs. n=12, 4 independent experiments. *p≤0.05 and ***p≤0.005 vs. control at time 0 by unpaired T-test. (D) qPCR analysis of gene expression in S1PR KO CPCs following 3 days of S1P stimulation *p≤0.05 **p≤0.01 vs. WT S1P treated by unpaired t-test; n = 9, 3 independent experiments