There were eQTLs that could be detected only in one tissue type and in some cases these are due to differences in gene expression. This is true for genes such as MAPT, which encodes for the tau protein that is expressed largely in post-mitotic neurons. Therefore, there will be cases where, when interrogating GWAS data it will be important to examine the target tissue of interest, thus affirming the need to look at brain for studies related to neurological or psychiatric phenotypes.
