In vitro control of embryonic axis formation by activin A, concanavalin A,and retinoic acid in Xenopus laevis

We have demonstrated that the tissue differentiation patterns along the dor soventral and anteroposterior axes can be controlled by a combination of ac tivin A, concanavalin A (Con A), and retinoic acid. Xenopus blastula animal caps, normally fated to form epidermal tissues, differentiated into ventra l mesoderm tissues such as coelomic epithelium and blood-like cells followi ng treatment with activin A (0.5 ng/ml). Dorsal mesoderm tissues like muscl e and notochord, were induced by graded addition of Con A. Conversely, Con A (1 mg/ml) induced anterior neural tissues, forebrain accompanied by eyes and cement glands, in the animal caps. Posterior neural tissues, hindbrain with ear vesicles and spinal cord, were induced by graded addition of activ in A. Retinoic acid was also capable of shifting the Con A-induced anterior neural tissues to more posterior tissue phenotypes, however, its caudalizi ng activity was slightly different from that of activin A. These results su ggest that the concentration gradients of these three factors can regulate the differentiation patterns along the embryonic axes. The present study pr ovides a suitable test system for analyzing the establishment of the fundam ental body plan in early vertebrate development.