An analysis of contractile and protrusive cell behaviors at the superficial surface of the zebrafish neural plate.

Background: The forces underlying convergence and internalization of the teleost neural plate remain unknown. To help understand this morphogenesis, we analyzed collective and individual cell behaviors at the superficial surface of the neural plate as internalization begins to form the neural keel in the hindbrain region of the zebrafish embryo.

Results: Convergence to the midline is not accompanied by anteroposterior elongation at this stage, and it is characterized by oscillatory contractile behaviors at the superficial surface of the neural plate, a punctate distribution of Cdh2 and medially polarized actin-rich protrusions at the surface of the neural plate. We also characterize the intimate relationship and dynamic protrusive cell behaviors between the surfaces of the motile neural plate and the stationary overlying non-neural enveloping layer.

Conclusions: Superficial neural plate cells are coupled by a punctate distribution of Cdh2-rich adhesions. At this surface, cells tug on neighbors using oscillatory contractions. Oscillatory contractions accompany convergence and shrinkage of the cells' superficial surface for internalization during keeling. Some shrinkage for internalization occurs without oscillations. The deep surface of the overlying non-neural enveloping layer is in contact with the superficial surface of the neural plate, suggesting that it may constrain the neural plate movements of convergence and internalization.