Firstly, a TWAS was performed using models of genetically predicted mRNA expression across twelve brain regions from GTEx, cortical samples from the PsychENCODE consortium, and whole blood GTEx samples. This was the most well-powered approach as there were 57 596 mRNA models, that is genetically predicted models of expression, available to test, with the number of unique genes totalling 11242, 12183, and 5915, for GTEx brain, PsychENCODE brain, and GTEx whole blood samples, respectively (online Supplementary Table S1). TWAS tested the association between genetically predicted expression of these mRNA and the odds of AN. Correcting for all 57 596 genetic models of mRNA expression (p < 8.68 × 10−7) revealed 40 association signals (14 unique genes), with several genes revealed in multiple brain regions (online Supplementary Table S1). We note here that ‘signals’ refers to any detected association in a tissue, which is different from unique genes as genes often have GReX models available to test in multiple tissues. The most significant association signals were found in a gene dense region on chromosome 3 (Fig. 1), in line with expectation
