DLK1 and cardiovascular disorder: On the contrary, in pericardial tissue specimens from another cohort of patients undergoing cardiothoracic surgery for residual cardiovascular disease (i.e., coronary artery disease or cardiac valve failure), we found substantial and consistent DLK1 expression (n = 12 patients) in the pericardium, where DLK1 localised to discrete stretches of mesothelial cells (Figure 1C).