Figure 7.

Cell intercalation in the notochord requires two distinct cell activities, cell contraction in the cell body (grey arrows in A) and polarized protrusive activity (black arrows). Contraction events are driven by the myosin IIB-dependent cortical actin network (green lines in B) organized into dynamic foci (purple), and interacting with myosin IIB at adhesion sites (red). Integrating this episodic cell shortening with polarized protrusive activity and dynamically regulated myosin IIB-dependent adhesion leads to cell intercalation (white arrows in C) and tissue level convergence and extension (black arrows). The extracellular matrix of the notochord-somite boundary is lateral in each case.