Immunoperoxidase localization of sonic hedgehog (Shh) in the normal human infant retina, and dysplastic retina. A) Ganglion cell layer from a region of normal retina of an infant with retinoblastoma. Shh is localized in the ganglion cell soma as punctate cytoplasmic staining (arrows). Shh was not detected in other regions of the retina, or in sections similarly treated with non-immune serum (data not illustrated). B) Region of normally laminated retina from the present case showed cytoplasmic shh in neurons residing in the inner nuclear layer (arrows). C) The region comprising dysplastic rosettes did not stain for Shh. Outer nuclear layer (ONL), outer plexiform layer (OPL), inner nuclear layer (INL), inner plexiform layer (IPL), and ganglion cell layer (GCL).