(A and B) Sagittal sections of E18.5 cortex from control and NesKO mice. (A) Staining with anti-PTBP2 antibody, control cortex shows PTBP2 expression in all neuronal nuclei, whereas NesKO cortex has lost PTBP2 expression in the vast majority of neurons. (B) H&E staining showing that NesKO cortex has similar thickness and largely normal morphology. Scale bar = 100 μM. (C) Nissl stained coronal sections of E18.5 cortex of wild-type and NesKO brain at two rostral–caudal planes. In the knockout brain, several major axonal tracks including the lateral olfactory tract (lot), internal capsule (ic) and external capsule (ec) were reduced, and the anterior commisure (ac) was missing. Corpus collosum, the major axon bundle connecting the two hemispheres, was present in the knockout brain. Scale bar = 250 μM. Staining was done on at least four knockout mice and four wild-type littermate controls from two litters.