TGFB1 and atrial fibrillation: In disease, however, activating stimuli such as transforming growth factor beta 1 (TGFβ) induce a phenotypic transition of fibroblasts towards α-smooth muscle actin (αSMA)-positive myofibroblasts (Baum and Duffy 2011; Tallquist and Molkentin 2017), which excessively secrete collagen and release cytokines leading to local inflammation, cardiac dysfunction, and arrhythmias such as atrial fibrillation (Jalife and Kaur 2015; Künzel et al. 2020).