Imputing gene expression in uncollected tissues within and beyond GTEx

Gene expression and its regulation can vary substantially across tissue types.  In order to generate new knowledge about gene expression in human tissues, the Genotype-Tissue Expression (GTEx) program has collected transcriptome data in a wide variety of tissue types from post-mortem donors. Many tissue types are hard to access and are not collected on every GTEx individual. The accessibility of certain tissue types also greatly limits the feasibility and scale of multitissue expression studies in non-GTEx populations.  We develop a multitissue imputation approach to impute gene expression in uncollected or inaccessible tissues. By analyzing data from nine selected tissue types in the GTEx pilot project, we demonstrate that transcriptome data from uncollected GTEx tissues can be imputed by harnessing eQTL and tissue-tissue correlation. More importantly, we show that using GTEx data as a reference, one can impute expression in inaccessible tissues in other expression studies.