Figure 6. Expression of sdk genes in developing zebrafish retina. In situ hybridization using cryosections of 48, 72 and 96 hpf zebrafish retina is shown for A–C) sdk1a, D–F) sdk1b, G–I) sdk2a, and J–L) sdk2b. Consistent labeling for all sdk genes was found in the INL, the GCL (arrows in all panels), and the CMZ (asterisks); however, strong expression in the ONL was observed only for (I) sdk2a, and (L) sdk2b at 96 (arrows, compare L, I to C–F). All images displayed are of sections processed with antisense probe. Abbreviations: hpf=hours post fertilization; Sdk=sidekick; ONL=outer nuclear layer; INL=inner nuclear layer; GCL=ganglion cell layer; CMZ=ciliary marginal zone. Scale bar in A=50 μm (applies to all).