In addition to the established direct role of SRF, myocardin, and other transcriptional activators and repressors on SMC contractile gene expression (bottom right3), levels of the contractile protein, αSMA, are fine-tuned through the activity of a TGFβ / NRG-1-ICD / circActa2 / miR-548f-5p axis. TGFβ stimulates NRG1 expression and cleavage, promoting nuclear translocation of NRG-1-ICD. Nuclear NRG-1-ICD recruits Ikzf1 and forms a stable transcriptional complex that interacts with the first intron of the Acta2 gene inducing circActa2 formation. circActa2 functions as a miRNA “sponge,” interacting with and repressing miR-548f-59, which targets αSMA mRNA for degradation, thereby resulting in increased αSMA levels and enhanced SMC contractile function. NRG-1, neuregulin-1; NRG-1-ICD, neuregulin-1 intracellular domain; circActa2, circular RNA Acta2; TGFβ, transforming growth factor-β; SRF, serum response factor; MyoCD, myocardin; miR-548f-5p, microRNA-548f-5p; αSMA, smooth muscle alpha actin (Acta2).