POU5F1 and atrial fibrillation: This is consistent with the reports that cells isolated from early gestational weeks [1, 3, 8] as well as from late mid-trimester [21] express the markers of pluripotency, Oct-4 and Nanog, although decreased Oct-4 expression has been found in AF cell cultures between 15 and 22 weeks of gestation at 8–10 passages [29].