Phosphoinositide-3-kinase regulatory subunit 1 gene polymorphisms are associated with schizophrenia and bipolar disorder in the Han Chinese population.

Schizophrenia (SCZ) and bipolar disorder (BD) are severe psychiatric disorders that share many genetic risk factors. This study aimed to investigate the association of phosphoinositide-3-kinase regulatory subunit1 (PIK3R1) gene rs3756668 and rs3730089 polymorphisms with SCZ and BD risks and determine the expression levels of PIK3R1. A total of 548 SCZ cases, 512 BD cases, and 598 healthy controls were included in this study. Single nucleotide polymorphisms (SNPs) were genotyped using the Sequenom MassARRAY platform, and quantitative reverse transcription polymerase chain reaction was conducted to examine the mRNA expression of PIK3R1. The genotypic distribution of rs3756668 in the BD group was significantly different from that in the healthy controls (P = 0.038). After adjustment for gender and age was made, rs3730089 was significantly associated with the risk of SCZ [AA/(AG + GG): OR = 2.25, P = 0.040; AA/GG: OR = 2.27, P = 0.038]. The SNP rs3756668 was associated with the susceptibility of BD (AA+GG/AG: OR = 0.73, P = 0.011) and the association remained after adjusting for gender and age. The mRNA level of PIK3R1 was significantly upregulated in patients with BD compared with that in the control group (P < 0.001). In terms of the diagnostic value of PIK3R1 for BD, the receiver operating characteristic curve analysis showed an area under the curve of 0.809 with 74.0% sensitivity and 73.9% specificity. PIK3R1 may be the shared susceptibility gene of SCZ and BD and may be a potential diagnostic biomarker for BD.