To provide additional validation for these findings, we analyzed raw data from a previous study32 (Methods) to identify genes with higher expression in differentiated rat oligodendrocytes relative to oligodendrocyte precursors. We observed that this group of genes was significantly enriched in M9 in every network (P ≤ 1.4 × 10−16; Supplementary Table 7). We obtained a third set of experimentally validated astrocyte markers33 and observed that this set was significantly enriched in M15 in every network (P ≤ 1.5 × 10−8; Supplementary Table 7). Using data from two independent proteomics studies, we searched all modules for over-representation of genes encoding proteins that are preferentially localized to the synapse34 (Methods). We observed significant enrichment for genes encoding synaptic proteins in M16 in every network (P ≤ 4.7 × 10−6 and P ≤ 1.6 × 10−3; Supplementary Table 7). Finally, we noted that established markers of oligodendrocytes (for example, PLP1, MAG, OLIG2, MOG, MOBP, CNP), astrocytes (for example, GFAP, GJA1, GLUL, GLUD1, SLC1A2, AQP4) and neurons (for example, MAP2, MAP1B, SYT1, NRXN1, SLC1A1 and NRCAM) were all correctly determined to be significant
