Fig. 8. Three possible models for TGFß signaling in the developing vasculature. (A) TGFß could activate both the SMAD and TAK1 pathways, which would then converge on a common target. (B) TGFß could signal through SMADs, leading to the activation of TAK1. (C) The TGFß/SMAD and TAK1 pathways could be acting independently, but synergistically, to regulate vascular development.