Fig. 2. AP differential response to Otx2 overexpression generates dose-dependent AP-graded increase of mesDA neurons. (A-L) TH immunohistochemistry performed at four anatomical levels corresponding to the posterior pretectum (A,E,I), anterior (B,F,J), intermediate (C,G,K) and posterior (D,H,L) mesencephalon. (M-P) Graphic representation showing the percentage of the tOtx2^bov/+ mesDA neurons detected in the two mutants at the anatomical levels corresponding to the histological sections shown. Abbreviations: SNpc, substantia nigra pars compacta; VTA, ventral tegmental area. The broken line demarcates the SNpc (A,E,I) or the VTA (B-D,F-H,J-L) territories analyzed for the cell-counting of TH⁺ cells.