8 well slide chambers

Live-cell imaging was adapted from^{45 (link)}. HeLa H2B–mCherry and tubulin–eGFP cells were transfected with siRNA oligonucleotides in 8-well µ-slide chambers (Ibidi). The cells were imaged for 48 h starting at 24 h post-transfection (approx.), using a Plan-Apochromat 20 × NA 0.8 objective and a 488-nm and 561-nm diode lasers on a LSM 5 live confocal microscope (Zeiss) equipped with a heating and CO₂ incubation system (Ibidi). ZEN software (Zeiss) was used to acquire images from seven 3.6-µm-spaced optical z-sections at various positions every 3 min. Then, single position files were generated from the maximum intensity projections in ZEN and converted into image sequences with free licensed AxioVision software (LE64; V4.9.1.0). Segmentation, annotation, classification and tracking of cells progressing through mitosis were performed using the Cecog analyser (http://www.cellcognition.org/software/cecoganalyzer)^{32 (link)}. The subsequent analysis was performed in Microsoft excel and GraphPad Prism. Three independent experiments were performed.

H9c2 and SW-13 cells were split one day before transfection and were cultured in 8-well µSlide chambers (ibidi, Gräfelfing, Germany). Lipofectamin 3000 (Thermo Fisher Scientific) was used according to the manufacturer’s instruction for cell transfection. In total, 250 ng of the plasmid was used per well, and the ratio of Lipofectamin 3000 to plasmid was 3:1.
HiPSC-derived cardiomyocytes were washed with phosphate-buffered saline (PBS) and treated with accutase (Sigma-Aldrich, St. Louis, MO, USA) for 6 min at 37 °C. Afterwards, the cardiomyocytes were resuspended in culture medium and centrifuged at 200x g for 5 min. After resuspension, the cardiomyocytes were cultured in Geltrex-coated µSlide chambers (ibidi). Lipofectamin 3000 (Thermo Fisher Scientific) was used to transfect iPSC-derived cardiomyocytes. The cardiomyocytes were incubated after transfection in µSlide chambers (ibidi) for 24 h.