a, Human induced pluripotent stem cell (iPSC), neural progenitor cell (NPC), neuronal, and astrocyte lines were grown in independent cultures and treated with therapeutic dosages of VPA (0.5mM, 1mM) or vehicle for 72 hours. TRANK1 mRNA expression was determined by reverse transcription polymerase chain reaction(RT-PCR). VPA treatment significantly increased TRANK1 expression in iPSCs, NPCs, and astrocytes, but not in neurons (*P<0.05, **P <0.01). b, TRANK1 expression in rat E18 hippocampal neurons cultured for 8d before treatment was also unaffected by VPA, even after 48h or 5 days of treatment at 2 mM dose. c, TRANK1 expression in HeLa cells was significantly increased by treatment with 1 mM or 2 mM VPA after stable shRNA knockdown of TRANK1. **P<0.01 TRANK1 shRNA knockdown vs no target shRNA control. ## P<0.01 VPA (1mM or 2 mM) treated vs untreated condition. ^^ P<0.01 shRNA TRANK1_66 knockdown vs no target control shRNA on 2mM VPA treatment condition. d, Lithium (1 mM) had no effect on TRANK1 expression in any of the 4 cell types tested. e, Neural progenitor cells (NPCs) carrying the risk allele (G) showed reduced TRANK1 mRNA expression (left) that was rescued by 72 h of VPA treatment at dosages of 0.5 mM (middle) or 1 mM (right). Values are expressed as mean relative ΔCT difference ± S.E.M. Comparisons: baseline, GG vs AA, p<0.0001; baseline, GG vs AG, p<0.05; baseline, GG vs VPA 0.5 mM, GG, p<0.05; baseline GG vs VPA 1 mM, GG, p<0.01. n =3 for GG carries; n = 3 for AA carries; n =5 for AG carries. f, Western blot: Qualitative increase in binding of anti-TRANK1 antibody to 274 kDa protein band extracted from NPCs in A-allele carriers vs G-allele carriers at both untreated and after treatment with 1 mM VPA conditions; n =3 for each condition. g, Quantification of western blot signal intensities with image J, **P<0.01 VPA treated vs untreated, # P<0.05 allele AA and AG vs GG at rs9834970. h, No relationship between rs9834970 genotype and TRANK1 mRNA counts (n=22) in human postmortem dorsolateral prefrontal cortex from RNA seq.