MARCKS and F-actin distribution during rhombencephalic and spinal neural tube closure. Neurulating chick embryos transverse cryosections, at the level of the presumptive rhombencephalon (A-F) and spinal cord (G-L). Double labeling of MARCKS, using a polyclonal antibody, and actin filaments, using phalloidin. Arrows: median and dorsolateral hinge points. ec, ectoderm; en, endoderm; n, notochord; s, somite. Scale bar: 60 μm.