Fig. 2. Presence of NrCAM in the embryonic retina. Laser scanning micrograph of a flat-mounted retina (E4) stained for NrCAM.(A) NrCAM is selectively present on RGC axons. Because of the developmental gradient from the central to the peripheral retina, only single axons and thin axon bundles are present in the periphery, converging to increasingly thicker bundles towards the optic fissure. The inset shows an overview of the retina and position of the micrograph; the upper left square delineates the peripheral region of the retina shown enlarged in B; the lower right square the central region shown in C. (B,C) Top and corresponding side views of (B) peripheral and (C) central retina regions. NrCAM is present on the very young, still short RGC axons in the peripheral retina, and is already restricted to the axonal compartment in this early phase of axon formation. In the central retina, NrCAM is exclusively present on axons of RGCs; their somata (forming the GCL) are not stained. OFL, optic fibre layer; GCL, ganglion cell layer; NEC, neuroepithelial cells. Scale bars: (A) 100 µm, (inset) 500 µm; (B,C) 25 µm.