The work pointed to involvement of retinoic acid signaling in cardiomyocyte cell polarity in mutant MYL4 (Figure 3E) and demonstrated that MYL4 associated with F-actin in atrial biopsies from human subjects in normal sinus rhythm, while MYL4 shifted to the sarcolemma in biopsies from AF patients. Here, MYL4 is linked to atrial fibrillation.