Anti-retinoic acid monoclonal antibody localizes all-trans-retinoic acid in target cells and blocks normal development in early quail embryo.

Avian cardiovascular development is vitamin A-dependent, and retinoic acid has been suggested to be active in this important developmental event. We report here that a monoclonal antibody against all-trans-retinoic acid blocks normal embryonic development in the quail causing cardiovascular abnormalities typical of avian vitamin A deficiency. In whole-mount preparations of stage 5 normal quail embryos the fluorescence associated with the antiretinoic acid monoclonal antibody localizes in Hensen's node and in caudal area. In stage 7-8 embryos fluorescence localizes in heart-forming areas as well as in head mesenchyme, in Hensen's node, in nephrotome, and in caudal area. These studies are the first to localize endogenous all-trans-retinoic acid during very early stages of normal avian development. We propose that all-trans-retinoic acid is biosynthesized in its target cells during early avian embryo-genesis and that the availability of this signal molecule is spatiotemporally regulated. We conclude that all-trans-retinoic acid or a closely related metabolite is the physiological form of vitamin A required for normal cardiovascular development and for other very early developmental events in the quail embryo.