We have demonstrated the use of peripheral blood RNA samples for the detection of cis-eQTLs and have shown that there is strong allelic concordance with cis-eQTLs that also had been detected in a HapMap B cell line dataset. These results indicate that a meta-analysis with larger sample size and hence statistical power results in a considerable increase in the detected cis-eQTL even though the arrays that had been used were different. Some cis-eQTLs can be observed across multiple tissue types, in all cases in the same allelic direction, suggesting a major conserved function. However most of the detected cis-eQTLs in these datasets were only detected in one of the two tissues, suggesting that more insight can be gained in the functional consequences of genetic variation by performing genetical genomics studies using different types of cells and tissues. This point is particularly relevant for identifying the function of risk variants for common diseases: for example study immune tissues for immune-mediated diseases, adipose tissue for obesity traits [8], brain tissue for neurological traits [10]. Genetical genomics experiments performed in outbred human populations
