Dopamine Perturbation of LCLs

LCLs of the study sample were derived at Rutgers University Cell and DNA Repository (RUCDR)^{36 (link)}. For each LCL, we measured EBV (viral) load (copy number), viable cell count (to index growth rate), and ATP level (to index energy status) at cell harvest (for use as covariates in expression analyses), which are known to have an effect on gene expression in LCLs^{41 (link)}. For the initially processed 515 SZ cases and 692 controls, RNAseq was carried out in five large batches; further detailed methodology was previously described^{37 (link)}. For DA perturbation (the pilot on four LCLs and the large-scale RNAseq samples), we grew cells in independent wells (on 6-well plates) in the presence or absence of DA at indicated concentrations. DA perturbation lasted 24 h. To block DA effects, we pre-treated the cells with the DA receptor antagonists for 6 h before adding DA to the cell culture medium. These DA blockers included: D1-like receptor (D1 or D5) antagonist SCH23390 (200 nM; ~100-fold saturation concentration^{42 (link)}) and D2-like receptor (D2, D3, or D4) antagonist spiperone (200 nM; ~100-fold saturation concentration^{43 (link)}). We purchased DA, SCH23390, and spiperone from Sigma-Aldrich. We included batch as a possible confounding variable in the analysis, i.e., as a covariate.