Expression of TH components and mature neuronal markers. In situ hybridizations were performed on serial cryosections cut in the coronal plane and collected from near the central retina (level of the optic nerve) at Stage 31. Composites of the ISH are shown for Dio2 (A), Dio3 (B) and Lim1 (C). The arrow in C indicates the location of the beginning of Lim1 migrating cells. Composites of ISH on a second set of serial sections at Stage 31 are shown for Dio2 (D), Dio3 (E) and Visinin (F). Arrows under panel C indicate the center and peripheral portions of all of the retinas in the figure. Representative scale bars for 100 μm are shown.