MARCKS and F-actin distribution during prosencephalic neural tube closure. Neurulating chick embryos transverse cryosections, at the level of the presumptive prosencephalon. Double labeling of MARCKS, using a polyclonal antibody, and actin filaments, using phalloidin. Arrows, median and dorsolateral hinge points. ec, ectoderm; ov, optic vesicles primordia. Scale bar: 60 μm.