Genes differentially expressed in cortex between knock-out (KO) and wild-type (WT) lines ( p < 0.01). Genes enriched in glutamate (cluster 1) and GABA (cluster 2) neurons (MNED; t test; p < 0.01). Cluster 3, Genes enriched in glia (detected by literature search and confirmed in MNED as overexpressed in whole tissue, compared with the 12 neuronal populations). Cluster 4, Genes found in MNED but not consistently different between glutamate and GABA neuronal classes (MNED; p > 0.01). Cluster 5, Genes not found in MNED. Several genes including Egr1 and neurogranin (Nrgn) were previously shown to be enriched in excitatory neurons (Chaudhuri et al., 1995; Singec et al., 2004).