Peanut lectin receptors in the early amphibian embryo: regional markers for the study of embryonic induction.

The regional and temporal specificity of peanut agglutinin binding was determined for early amphibian embryos. With the onset of neurulation, a receptor appears on the epidermis, but remains absent from the neural plate. A second type of receptor, largely masked by sialic acid, appears throughout the extracellular matrix. In the axolotl, the epidermal receptor is epimucin and the matrix receptor is fibronectin plus other components. Both receptors are autonomously expressed, on schedule, by appropriate explants of gastrula tissue. Expression of the epidermal receptor is suppressed after exposure to a neural inducing signal. This shows that the epidermal PNA receptor is a reliable marker of epidermal character and that neural induction affects the program of macromolecular synthesis within hours of the graft.