Long-term, in toto live imaging of the developing mouse heart

Abstract Mapping holistic cell behaviors sculpting mammalian heart has been a goal, but so far only successes in transparent invertebrates and lower vertebrates. Using a live-imaging system comprising a customized vertical light-sheet microscope equipped with a culture module, a heartbeat-gated imaging strategy, and a digital image processing framework, we realized imaging of developing mouse hearts with uninterrupted cell lineages for up to 1.5 days. Four-dimensional landscapes of cell behaviors revealed a blueprint for ventricle chamber formation in which biased outward migration of outermost cardiomyocytes coupled with cell intercalation and horizontal division. The trabeculae, an inner muscle architecture, was developed through early fate segregation and transmural cell arrangement involving both oriented cell division and directional migration. Thus, live-imaging reconstruction affords a transformative means for deciphering mammalian organogenesis.