In conclusion, we present unique twin data using thousands of eQTLs in multiple tissues that extend our understanding of the architecture and regulation of gene expression in multiple ways. We highlight the importance of studying low frequency / rare regulatory variants in complex traits by detecting and mapping missing heritability of gene expression beyond the common cis-variants. We also show that a substantial proportion of gene expression heritability is trans to the structural gene and identify several replicating trans-variants which seem to act predominantly in a tissue-restricted manner and are potentially regulators of many genes.
