data sets associated with the genome segments in each SOM map unit (hexagonal cells) can then be visualised in the same framework to learn how each additional kind of data is distributed on the chromatin state map. Figure 7B shows CAGE/TSS expression data overlaid on the randomly initialised (left) and trained map (right) panels. In this way the trained SOM highlighted cell type-specific TSS clusters (bottom panels of Figure 7B), indicating that there are sets of tissue specific TSSs that are distinguished from each other by subtle combinations of ENCODE chromatin data. Many of the ultra-fine-grained state classifications revealed in the SOM are associated with specific gene ontology (GO) terms (right panel of Figure 7C). For instance, the left panel of Figure 7C, identifies 10 SOM map units enriched with genomic regions associated with genes associated with the GO term ‘immune response’. The central panel identifies a different set of map units enriched for the GO term “sequence-specific TF activity”. The two map units most enriched for this GO term, indicated by the darkest green colouring, contain genes with segments that are high in H3K27me3 in H1 hESC cells, but that differ in H3K27me3 levels in HUVEC cells. Gene function
