Morphogenesis entails cellular interactions orchestrated by molecules present within and on cells as well as in the extracellular environment. Previous work in our laboratory has focused on the contribution of several extracellular (ECM) molecules to the development of specific organ systems in the long-tailed monkey. Current studies have been expanded to examine the role of cell adhesion molecules, which mediate ligation between cells, in the early macaque embryo. We have explored the ontogeny of the cranial neural crest, a specialized population of cells which is formed by epithelial-mesenchymal transformation and contributes to the craniofacial skeleton, thymus and heart. The distribution of neural cell adhesion molecule (N-cam) during cranial neural crest cell migration was examined by peroxidase immunocytochemistry in serially-sectioned embryos. These observations were correlated with changes in the integrity of the neural tube basement membrane (BM) as evidenced by laminin (LM) and collagen-IV (col-IV) immunoreactivity. Preliminary results indicate that during the height of crest emigration from the hindbrain in stages 10 and 11 (4-20 somites), there are discontinuities in the bm at the tips of the neural folds and newly-formed neural tube; groups of N-CAM-positive cells are observed exiting from the neuroepithelium through these bm breaks. The mesenchyme of the pharyngeal arches, which are known destinations of cranial crest cells, is also specifically stained with N-CAM. By stage 12 (21-29 somites), the BM of the hindbrain neuroepithelium is stained continuously with both LM and col-IV; N-CAM reactivity is most evident in the sensory pre-ganglia (trigeminal, facioacoustic and glossopharyngeal) associated with the first three pharyngeal arches. These studies indicate that coordinated interplay between extracellular molecules (LM and col-IV) and cell surface moieties (N-CAM) is involved in the morphogenesis of the primate cranial neural crest.
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