A) Schematic of full-length and dominant negative mDia1. FH, formin homology domain; GBD, GTPase-binding domain; DID, diaphanous inhibitory domain; DAD, diaphanous autoinhibitory domain. B) 10T1/2 cells transfected with DNmDia or empty expression vector were serum-starved, and treated with sphingosine-1-phosphate (S1P) for 16 hr. Endogenous SMC marker expression was detected by immunoblotting. C) 10T1/2 cells expressing mCherry empty vector (EV) or mCherry-DNmDia were serum-starved, treated with S1P for 4 min, and then fixed. Localization of endogenous MRTF-A was determined by immunohistochemistry. D) Quantification of MRTF-A nuclear localization from three separate S1P-treated experiments with over 100 cells counted per condition. * p < 0.05.