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 analysis with the GO ontology tool (GREAT72) reveals that the map unit with high H3K27me3 in both cell types is enriched in TF genes with known neuronal functions, whereas the neighbouring map unit is enriched in genes involved in body patterning. The genome browser shots at the bottom of Figure 7C pick out an example region for each of the two SOM map units illustrating the difference in H3K27me3 signal. Overall, we have 228 distinct GO terms associated with specific segments across one or more states (Ali Mortazavi, personal communication), and can assign over one third of genes to a GO annotation solely on the basis of its multi-cellular histone patterns. Thus the SOM analysis provides a fine-grained map of chromatin data across multiple cell types, which can then be used to relate chromatin structure to other data-types at differing levels of resolution (for instance, the large cluster of units containing any active TSS, its sub-clusters composed of units enriched
