Isoform specific differences in phospholipase C beta 1 expression in the prefrontal cortex in schizophrenia and suicide

Abstract

Our previous study demonstrated that phospholipase C beta 1 mRNA was down-regulated in Brodmann's area 46 from subjects with schizophrenia. However, phospholipase C beta 1 protein has also been shown to be lower in Brodmann's area 8 and 9 from teenage suicide subjects, creating a potential confound in interpreting the findings in schizophrenia due to the high suicide rate associated with this disorder. To begin to reconcile and consolidate these findings, in this study, we measured mRNA and protein levels of phospholipase C beta 1 variants a and b in Brodmann's area 46 and Brodmann's area 9 from subjects with schizophrenia, many of whom were suicide completers, and determined the diagnostic specificity of observed findings. Consistent with our previous study, levels of phospholipase C beta 1 a and b mRNA, but not protein, were lower in Brodmann's area 46 from subjects with schizophrenia. In Brodmann's area 9, phospholipase C beta 1a protein levels were lower in subjects with schizophrenia, while phospholipase C beta 1b mRNA was higher and protein was lower in those that had died of suicide. Altered protein levels in Brodmann's area 9 appeared to be diagnostically specific, as we did not detect these changes in subjects with bipolar disorder, major depressive disorder or suicide completers with no diagnosis of mental illness. We further assessed the relationship between phospholipase C beta 1 and levels of muscarinic receptors (CHRMs) that signal through this protein, in both human and Chrm knockout mouse central nervous system tissue, and found no strong relationship between the two. Understanding central nervous system differences in downstream effector pathways in schizophrenia may lead to improved treatment strategies and help to identify those at risk of suicide.

Fig. 1

PLCB1a and PLCB1b mRNA (left) and PLCB1a and PLCB1b protein (right) levels in cohort 1 measured in tissue from BA46, analysed as Sz vs. control (a–d), as suicide completers vs. non-suicide (e–h), and with Sz subjects divided into MRDS and non-MRDS compared to control (i–l). Error bars show median (Mdn) and IQR

Fig. 2

PLCB1a and PLCB1b mRNA (left), and PLCB1a and PLCB1b protein (right) levels in cohort 1 measured in tissue from BA9, analysed as Sz vs. control (a–d), as suicide completers vs. non-suicide (e–h), and with Sz subjects divided into MRDS and non-MRDS compared to control (i–l). Error bars show median (Mdn) and IQR

Fig. 3

PLCB1a and PLCB1b protein levels in cohort 2 measured in tissue from BA9 (a–d) and BA26 (e–h), analysed as subjects with MDD, BD, and subjects who died of suicide who had no history of psychiatric illness (suicide no Dx), compared to control (a), (b), (e), (f), and with all subjects in this cohort divided into suicide completers vs. non-suicide (c), (d), (g), (h). Error bars show median (Mdn) and IQR

Fig. 4

PLCB1 a and b mRNA (a), and PLCB1a (b) and PLCB1b (c) protein, levels measured in CNS from Chrm1, 2, 4 and 5 knockout (^−/−) mice compared to WT mice. Error bars show median (Mdn) and IQR. Western blot image (d) of 5 ug human or mouse cortical homogenate, run in duplicate, probed with anti-PLCB1 antibody