Fig4A. [doi:10.1002/dvdy.21536] Copyright: This image is from Fogel JL; Chiang C; Huang X; Agarwala S, "Ventral specification and perturbed boundary formation in the mouse midbrain in the absence of Hedgehog signaling." Dev Dyn 2008; 237: 1359-72. Reprinted with permission of Wiley-Liss Inc. [PMID:18429041]