Cardiomyocyte orientation modulated by the Numb family proteins–N-cadherin axis is essential for ventricular wall morphogenesis.pdf

The formation of ridge-like trabeculae from the myocardium is central to heart formation, as it allows for the increase in muscle mass before the formation of coronary circulation. We found that cardiomyocytes display spatiotemporal orientation during trabecular formation. Cardiomyocytes in the Numb and Numblike double knockout display abnormal cellular orientation. The knockout hearts display reduced membrane localized N-cadherin due to attenuated N-cadherin recycling to the membrane. When chick N-cadherin is overexpressed in the knockouts via a mosaic model, the defects of cellular orientation and trabeculation were at least partially rescued, suggesting that Numb and Numblike regulate cellular orientation and trabeculation via N-cadherin. Cellular orientation might modulate the directionality of cellular migration, mitotic spindle orientation, and cellular organization during heart morphogenesis.