vast majority of genes do not exhibit highly differentiated expression variation between populations, however every pairwise combination of populations has genes with highly structured expression variation. Analysis of the union of probes exhibiting top 5% VST scores from each pairwise population comparison indicates a significant enrichment of Gene Ontology (GO) terms, including nucleus, protein binding, RNA binding, nucleotide binding, RNA splicing (Table S2). Each of the eight populations also exhibited significant population-specific GO term enrichment when top population-specific VST scores were analyzed (Table S3). For example, CEU exhibits an enrichment in immune response (GO:0006955, p-value 6.7×10−6) and regulation of immune response (GO:0050776, p-value 4.05×10−5), indicating strong structure of expression variation for genes of these categories in CEU versus other populations, and that this structure is not seen between any other populations. We also addressed the question of whether those functions which are significantly differentiated in one population inform differentiation in a closely-related population (i.e., differentiation of function may be shared by closely-related populations). For example, differentiation might be similar for each of CHB and JPT when individually compared to all the other six populations (or for LWK, MKK, and YRI). In general, GO terms corresponding to genes which are significantly
