Fig. 8. Model for signal integration mediated by Smad7 in Xenopus laevis ectoderm. A proposed model of signaling integration in the context of neuralization might be mediated by Smad7. In this model, BMP signaling leads to the activation of both the Smad and TAK1 pathways. BMP signaling can be inhibited by 51-B6, a cerberus/gremlin-related factor (E. B., I. M.-S., C. R. A. and A. H. B., unpublished). We postulate that the transcriptional activation of TAB3 modulates the activity of TAK1, and might activate the NFkB and JNK pathways, as has been demonstrated for TAB2 in other contexts (Mazars et al., 2001; Wang et al., 2001). In addition, this switch might derepress some MAPK pathways, as TAK1/TAB1 complexes signal through p38 MAPK. Additional mechanisms to activate neural gene expression involve the HMG-X transcription factor and a variety of RNA-binding proteins implicated in post-transcriptional control. Red lines depict inhibitory signaling interactions. Green lines depict stimulatory signaling, either transcriptionally or through biochemical activation. Pink indicates genes identified in the array.