Mouse Embryonic Stem Cell Culture

Mouse ES cells (JM8.N4, RRID: CVCL_J962) were used for all experiments and obtained as previously described (15 (link)). ES cells were cultured on 0.1% gelatin-coated plates in ESC DMEM (Corning 10101CV, contains 4.5 g/l glucose, 110 mg/l sodium pyruvate, glutagro, and 15 mg/l phenol red) with 15% FBS (HyClone), 0.1 mM MEM non-essential amino acids (Gibco), 2 mM l-glutamine (Gibco), 0.1 mM 2-mercaptoethanol (Sigma), 1× Penicillin Streptomycin solution (Corning), and 1000 units/ml of ESGRO LIF (Chem-icon). ESCs were fed daily, cultured at 37°C in a 5% CO₂ incubator, and passaged every 2 days by trypsinization. For Leptomycin B treatment, cells were treated with 10 ng/ml Leptomycin B (Sigma) at 37°C in a 5% CO₂ incubator for 1 hour. For all imaging experiments, cells were imaged in DMEM without phenol red (Gibco 31053028, contains 4.5 g/l glucose) with 110 mg/l sodium pyruvate (Gibco) and all other components previously listed.