Fig. 10. A proposed role for zic genes in the developing midbrain. Expression of zic2a and zic5 is activated through canonical Wnt signaling in the dorsal midbrain. Activation of zic tectal expression is mediated through Tcf/Lefs, including Lef1 and Tcf7 acting through an enhancer in the downstream zic5 (D5) region. Zics subsequently control proliferation in the alar plate.