An analysis of neural tube formation and its defects induced by vitamin A in chick embryo, using monoclonal antibodies

S34 MONOCLONAL ANTIBODIES WHICH HAVE HIGH AFFINITY TO THE TISSUES DERIVED FROM ECTODERM AND MESODERM IN AMPHIBIAN EMBRYOS * HARUMASA OKAMOTO and SHOHEI MITANI , Department of Neurobiology, Institute of Brain Research, School of Medicine, University of Tokyo, 7-3-1 Hongo, Tokyo. In amphibian embryos, three germ layers are established as a result of gastrulation movement. Subsequently, the ectoderm gives rise to either the nervous or epidermal tissues; while the mesoderm yields muscular, notochordal or mesenchymal tissues. Detailed analysis of the determination process in early differentiation of the respective tissue has been hampered, partly by lack of a suitable probe. The application of hybridoma technology seems promising in this respect, since monoclonal antibodies that might distinguish the tissue primordia of interest would allow a quantitative analysis of the early differentiation process. We generated monoclonal antibodies to the early embryo of Xenopus laevis, and determined their histological specificities on frozen sections with the aid of indirect immunofluorescence. Mice were immunized with crude particulate fractions from neurula stage embryos. One of the antibodies (EMI) shows high affinity to the tissues derived from ecto- and mesoderm in general, and probably to the primordial germ cells as well. The other one (El) binds exclusively to the epidermal cells. The E1 antigen is first detected at the early neurula stage in the presumptive epidermal cell layer; whereas the EMI antigen is already present in the unfertilized egg, where the antigen is localized mainly in the animal hemisphere and also in a small region around the vegetal pole. By tracing the antigen distribution during subsequent development, it is indicated that the main EMI antigen in the egg is segregated into the ecto- and mesodermal cytoplasm, and the vegetal pole antigen into germ cell cytoplasm respectively. The ecto/meso- versus endodermal polarity might be represented in the unfertilized egg in a form of animal-vegetative polarity.

AN ANALYSIS OF NEURAL TUBE VITAMIN A IN C H I C K E M B R Y O ,

FORMATION AND ITS DEFECTS INDUCED USING MONOCLONAL ANTIBODIES

KUNIHIKO OBATA and SHINOBU C. F U J I T A Gunma University School of Medicine, Maebashi, G u n m a 371, J a p a n .

BY

, Department of P h a r m a c o l o g y , 3-39-22 Showa-machi,

Differentiation of the neural plate, and formation of t h e neural tube were investigated on 2-3 day chick embryos with immunohistochemistry, using monoclonal antibodies (MAbs) w h i c h were produced against embryonic nervous tissue. Ependyma-specific MAb 94A2 stained the ventricular surface o f t h e n e u r a l p l a t e as s o o n as it w a s d i f f e r e n t i a t e d from the ectoderm. This suggests that the ependymal l a y e r p l a y s a r o l e in s u b s e q u e n t formation of the neural tube. Injection of v i t a m i n A (0.1-0.5 mg retinoic acid) into albumen before, or 1 day after the beginning of i n c u b a t i o n , resulted in s e r i o u s m a l f o r m a t i o n of t h e n e u r a l t u b e . It c o n s i s t e d of a collection of several small tubes. Basement membrane surrounded the collection as a w h o l e . Tubulin arrangement in t h e tube cells, and formation of the notochord and somites, appeared normal. Therefore, it w a s h y p o t h e s i z e d that disorganization of the ependyma was involved in t h e v i t a m i n A-induced neural tube defects of chick embryo.