a, Scheme of cardiac differentiation showing timing of IAA and BMP4 addition. Cardiac troponin T (cTnT) immunostaining of an auxin inducible degron strain of BRM (Brm-AID) at D10 of differentiation induced with two different BMP4 concentrations with or without IAA present throughout the differentiation. b, Immunostaining with cTnT shows that Brg1 loss is not rescued by addition of increasing the amount of BMP4. Scale bars are 200μm. c-e, Heat maps showing differential enrichment of ATAC-seq peaks of WT and BRM KO cells at D4 (c), D6(d) and D10 (e) of cardiac differentiation with normal (1x) and high (4x) BMP4 concentrations. Boxed regions show restoration of WT-like chromatin in KO cells at high BMP4 condition. Vertical lanes show replicate data. f-g, Browser tracks show chromatin accessibility in WT and Brm−/− cells along with H3K27ac marks in cardiomyocytes and neural precursor cells (purple track) near indicated cardiac genes (f) and neural genes (g).