PRRX1 and atrial fibrillation: The PRRX1 protein is highly expressed in the cardiovascular system throughout embryonic development, predominantly in the mesenchymal tissues, including the heart, endothoracic great arteries and pulmonary veins (Leussink et al., 1995; Bergwerff et al., 1998; Libório et al., 2011), a common source of ectopic beats triggering AF in the majority of patients (Haïssaguerre et al., 1998).