Supplementing the results of hierarchical clustering, we found evidence for both region-specific and pan-regional cis-eQTL signals. In favor of the latter, the majority (55%) of our signals were found only by averaging expression values across all ten brain regions, indicating that there was sufficient sharing of weak eQTL signals among regions to benefit from an increase in signal-to-noise ratio through averaging. Almost all regional cis-eQTL signals seen in more than one brain region were also identified from the average-all analysis (Fig. 2a). Figure 3a gives one example of a pan-regional signal.
