The neurobiological function of the feto-specific binding protein, alpha-fetoprotein (AFP) in normal and abnormal neural tube differentiation and development will be investigated. Emphasis will be placed on the possible involvement of AFP in the cellular mechanisms which may underlie such major congenital malformations of the central nervous system as the open neural tube defects, "spina bifida" and anencephaly. The role of intra- and extra-neuronal AFP in such cytological aspects of neural development as neurogenesis, neuronal migration and neuronal differeniation and the mechanism of its uptake by neurons will be studied in vitro (with in vivo corroboration wherever possible) in both the normal mouse and in a mutant ("curly-tail"), genetically predisposed to open neural tube defects. LOng-term, organotypic cultures (homologous explant pairs) of the fetal mouse neural tube and spinal cord of various ages (E-8 to E-15) will be studied morphologically in living and stained preparations at both the light and electron microscopic levels by a wide variety of histological techniques which include: Nissl, Golgi-Cox and neurofibrillary stains; 3H-steroid and 3H-thymidine autoradiography and immunofluorescence. Findings will be correlated with biochemical measures for quantification. The uptake (internalization) of AFP in vitro will be studied by 125-I binding studies and autoradiography and by ultrastructural immunocytochemistry in order to evaluate both the manner of uptake and the cellular mechanisms and organelles involved. This new and unique approach is concerned with a possible active role for AFP normal and abnormal neural tube development and departs from the traditional view of its serving only incidentally as a pre-natal diagnostic marker. These studies question whether or not there is something unusual in neural tube defects about the biology of AFP or in the tissue responses to it either as a result of the defect, as a concomitant or, in fact, as the primary event. These studies seek to determine: where, when, what and how does AFP act, it at all, in normal neural tube development and how this may differ in neural tube defects. This unique approach can provide new and heretofore, unavailable information regarding the cellulr neurobiology of open neural tube defects, the most common and catastrophic birth defects of man.