Figure 3.

A new model for neural induction in Xenopus laevis embryos. In this model Ca²⁺ plays a central role, by directly activating Ca²⁺ target genes such as xPRMT1b, which in turn control neural gene transcription either directly or via the activation of a Ca²⁺/calmodulin kinase type II. The Ca²⁺ signals may also inhibit the BMP signalling pathway by activating a calcineurin, which prevents the phosphorylation of Smads (see text for more details). The activation of the DHP-Ca²⁺ channels is performed by an as yet unidentified mechanism (indicated by the ‘?’) at the level of the binding of BMP by neural inducers.