A morphological and experimental study of the mesencephalic neural crest cells in the mouse embryo using wheat germ agglutinin-gold conjugate as the cell marker.

The distribution of the mesencephalic neural crest cells in the mouse embryo was studied by mapping the colonization pattern of WGA-gold labelled cells following specific labelling of the neuroectoderm and grafting of presumptive neural crest cells to orthotopic and heterotopic sites. The result showed that (1) there were concomitant changes in the morphology of the neural crest epithelium during the formation of neural crest cells, in the 4- to 7-somite-stage embryos, (2) the neural crest cells were initially confined to the lateral subectodermal region of the cranial mesenchyme and there was minimal mixing with the paraxial mesoderm underneath the neural plate, (3) labelled cells from the presumptive crest region colonized the lateral cranio-facial mesenchyme, the developing trigeminal ganglion and the pharyngeal arch, (4) the formation of neural crest cells was facilitated by the focal disruption of the basal lamina and the cell-cell interaction specific to the neural crest site and (5) the trigeminal ganglion was colonized not only by neural crest cells but also by cells from the ectodermal placode.