PNNs are normally formed in the Has3^−/− brain. A, Cortical sections of WT and Has3^−/− mice were stained with FITC-conjugated WFA (WFA), and antibodies to aggrecan (Agc), brevican (Brev), phosphacan (Phos), or tenascin-R (TN-R). Scale bar, 30 μm. B, The number of neurons bearing PNNs was determined in the cortex (Cortex) and the hippocampus (Hippocampus), as described in Materials and Methods. There are no statistical differences in the number of PNNs between WT and Has3^−/− mice (Student's t test; n = 5 per genotype). C, Representative confocal images of PNN-bearing neurons double-labeled with FITC-conjugated WFA (WFA) and anti-aggrecan antibody (Agc). Note that staining patterns of PNNs are indistinguishable between WT and Has3^−/− neurons. Scale bar, 5 μm.