Increasing the sample size of the current study will likely yield a larger number of QTLs, particularly those with small to moderate effect size. It would also be of interest to extend this initial work to other tissues, which will not only be important in defining tissue specific QTLs, but also will afford us the opportunity to examine QTLs at transcripts not typically detected in brain. Additionally, we have limited our sampling to a population that represents only a small component of worldwide human genetic diversity [26]. Adding tissues from other populations would provide an understanding of genetic control of expression in different groups and a framework for interpretation of GWAS results in these groups. Furthermore, inter-population comparison would help refine the basis by which differences in genetic architecture affect expression. We also note that our coverage of DNA modifications is currently incomplete as there are other epigenetic modifications, such as acetylation, that are not currently accessible to high throughput techniques, and many more methylation sites exist than assayed here. Whether genotypic differences influence other components of the epigenome is
