Protein kinase C mediates neural induction in Xenopus laevis

Inductive cell interactions are essential in early embryonic development, but virtually nothing is known about the molecular mechanisms involved. Recently factors resembling fibroblast growth factor and transforming growth factor-beta were shown to be involved in mesoderm induction in Xenopus laevis, suggesting that membrane receptor-mediated signal transduction is important in induction processes. Here we report direct measurements of protein kinase C (PKC) activity in uninduced ectoderm, and in neuroectoderm shortly after induction by the involuting mesoderm, in Xenopus laevis embryos. Membrane-bound PKC activity increased three to fourfold in the induced neuroectoderm while the cytosolic PKC activity was decreasing, indicating that PKC activity was translocated during neural induction. A similar time- and dose-dependent translocation of activity was seen after incubation with the PKC activator 12-O-tetradecanoyl phorbol-13-acetate, which also induced neural tissue in competent ectoderm, suggesting that PKC is involved in the response to the endogenous inducing signal during neural induction.