ANALYSIS OF HINDBRAIN NEURAL CREST MIGRATION IN THE LONG-TAILED MONKEY (MACACA-FASCICULARIS)

Neural crest cells make a substantial contribution to normal craniofac ial development. Despite advances made in identifying migrating neural crest cells in avian embryos and, more recently, rodent embryos, know ledge of crest cell migration in primates has been limited to what was obtained by conventional morphological techniques. In order to determ ine the degree to which the nonhuman primate fits the mammalian patter n, we studied the features of putative neural crest cell migration in the hindbrain of the long-tailed monkey (Macaca fascicularis) embryo. Cranial crest cells were identified on the basis of reported distribut ional and morphological criteria as well as by immunocytochemical dete ction, of the neural cell adhesion molecule (N-CAM) that labels a subp opulation of these cells. The persistent labeling of a sufficient numb er of crest cells with antibodies to N-CAM following their exit from t he rostral preotic and post-otic regions of the hindbrain facilitated tracking them along subectodermal pathways to their respective destina tions in the first, second and third pharyngeal arches. Peroxidase imm unocytochemistry was also employed to localize laminin and collagen-IV in neuroepithelial basement membranes. At stage 10 (8-11 somites), cr est emigration occurred in areas of unfused neural folds through focal disruptions in the neuroepithelial basement membrane in both the rost ral and pre-otic regions, although there was little evidence of crest migration in the post-otic hindbrain. By stage 11 (16-17 somites), the neural folds were fused (pre- and post-otic hindbrain) or in the proc ess of fusing (rostral hindbrain), yet crest cell emigration was appar ent in all three areas through discontinuities in the basement membran e. Emigration was essentially complete at stage 12 (21 somites) as ind icated by nearly continuous cranial neural tube basement membranes. At this stage the pre-ganglia (trigeminal, facioacoustic and glossophary ngeal) were consistently stained with N-CAM. The current study has pro vided new information on mammalian neural crest in a well-established experimental model for normal and abnormal human development. includin g its use as a model for the retinoic acid syndrome. In this regard, t he current results provide the basis for probing the mechanisms of ret inoid embryopathy which may involve perturbation of hindbrain neural c rest development.