Expression of TH components and early neurogenesis markers. Section ISH composites of Stage 26 chick retinal cryosections cut in the coronal plane using the following probes: TRb (A, A'), Otx2 (B, B'), NeuroD (C, C'), Cath5 (D, D'), Brn3b (E, E'), Crx (F, F'), and Shh (G, G'). The arrows at the bottom of the low magnification sections indicate the central and peripheral retina. Zoomed-in views (using Adobe Photoshop) from the indicated portions of each section are shown on the right. Arrows point toward positive cells for the indicated probes.