Fig. 2. Distinct temporal dependence of medial-to-lateral-derived ventral cell types on Shh signaling. (A-H) Immunohistochemistry for dopaminergic (Th, green) and serotonergic (5-HT, red) neurons on E18.5 sagittal sections. Sections are counterstained with Hoechst (blue), the mid/hindbrain is outlined. (A-H) Both cell types are greatly reduced in Smo-En1 cko and Gli2-En1 cko but not in Smo-Nes cko mutants (arrows). The number of serotonergic neurons in the posterior hindbrain is normal (arrowheads). Arrowhead in C indicates Th-positive neurons in the locus coeruleus. (I-P) In situ hybridization for Nkx2.2 and Isl1 on horizontal sections of E10.5 and E12.5 mes. (I-L) The ventral (V) populations of Isl1- and Nkx2.2-positive cells are not induced in Smo-En1 cko mes (K,L, red arrowheads). (M-P) In Smo-Nes cko mes, Isl1- and Nkx2.2-positive cells are generated but slightly reduced (O,P, red arrowheads). (J,L,N,P) Dorsal (D) Isl1-expressing cells in control and mutants (black arrowheads). (Q) The plane of section (I-P) is indicated in the schematic. Scale bars: 50 µm.