NIPBL and atrial septal defect: Overall our results show that when cells derived from cardiogenic mesoderm, endoderm, or subpopulations of both are made deficient in Nipbl, heart defects, primarily ASD, always develop at a frequency of approximately 30%, the same incidence as observed in mice that are globally Nipbl-deficient (Figs 3 and 5A, and S1 Data).