Fig. 10. Interactions between T-box genes and vab-7 in C. elegans. vab-7 expression is activated (probably indirectly) at the posterior of embryos by TBX-8 and TBX-9 working together. VAB-7, in turn, functions to repress mab-9 expression in posterior cells. Meanwhile, at the anterior of embryos, vab-7 is itself repressed by the action of TBX-30. This repression is likely to be direct, acting through T-box binding sites in the vab-7 5' regulatory region.