Seminar

Notch activates cell cycle reentry and progression in quiescent cardiomyocytes.

Dr. Victor Campa

The inability of heart muscle to regenerate by replication of existing cardiomyocytes has engendered considerable interest in identifying developmental or other stimuli capable of sustaining the proliferative capacity of immature cardiomyocytes or stimulating division of postmitotic cardiomyocytes. It is generally accepted that Notch participates in cardiac morphogenesis by inhibiting differentiation and promoting proliferation of cardiac precursors. We found that reactivation of Notch signalling causes embryonic stem cell-derived and neonatal ventricular cardiomyocytes to enter the cell cycle. The proliferative response of neonatal ventricular cardiomyocytes declines as they mature, such that late activation of Notch triggers the DNA damage checkpoint and G2/M interphase arrest. Notch induces RBP-J-dependent expression of cyclin D1 but, unlike other inducers, also shifts its subcellular distribution from the cytosol to the nucleus. Nuclear localization of cyclin D1 is independent of RBP-J. Thus, the influence of Notch on nucleocytoplasmic localization of cyclin D1 is an unanticipated property of the Notch intracellular domain that is likely to regulate the cell cycle not only during cardiogenesis but also in other contexts, including tumorigenesis.