Elsevier

Brain, Behavior, and Immunity

Volume 53, March 2016, Pages 194-206
Brain, Behavior, and Immunity

Full-length Article
Altered neural signaling and immune pathways in peripheral blood mononuclear cells of schizophrenia patients with cognitive impairment: A transcriptome analysis

https://doi.org/10.1016/j.bbi.2015.12.010Get rights and content

Highlights

  • WNT pathway was down-regulated in CD and SZ groups, but not in the CS group.

  • Suppression of WNT signaling was a defining feature of cognitive decline in SZ.

  • CS, CD and SZ were characterized by the up-regulated pathways in immune dysfunction.

  • CS, CD and SZ were characterized by the up-regulated pathways in energy metabolism.

Abstract

Cognitive deficits are a core feature of schizophrenia and contribute significantly to functional disability. We investigated the molecular pathways associated with schizophrenia (SZ; n = 47) cases representing both ‘cognitive deficit’ (CD; n = 22) and ‘cognitively spared’ (CS; n = 25) subtypes of schizophrenia (based on latent class analysis of 9 cognitive performance indicators), compared with 49 healthy controls displaying ‘normal’ cognition. This was accomplished using gene-set analysis of transcriptome data derived from peripheral blood mononuclear cells (PBMCs). We detected 27 significantly altered pathways (19 pathways up-regulated and 8 down-regulated) in the combined SZ group and a further 6 pathways up-regulated in the CS group and 5 altered pathways (4 down-regulated and 1 up-regulated) in the CD group. The transcriptome profiling in SZ and cognitive subtypes were characterized by the up-regulated pathways involved in immune dysfunction (e.g., antigen presentation in SZ), energy metabolism (e.g., oxidative phosphorylation), and down-regulation of the pathways involved in neuronal signaling (e.g., WNT in SZ/CD and ERBB in SZ). When we looked for pathways that differentiated the two cognitive subtypes we found that the WNT signaling was significantly down-regulated (FDR < 0.05) in the CD group in accordance with the combined SZ cohort, whereas it was unaffected in the CS group. This suggested suppression of WNT signaling was a defining feature of cognitive decline in schizophrenia. The WNT pathway plays a role in both the development/function of the central nervous system and peripheral tissues, therefore its alteration in PBMCs may be indicative of an important genomic axis relevant to cognition in the neuropathology of schizophrenia.

Introduction

Schizophrenia is a severely debilitating psychiatric disorder characterized by delusions, hallucinations, and deficits in cognitive function. Recent genome-wide association (GWA) studies have identified a growing number of genetic loci associated with schizophrenia (Purcell et al., 2009, Ripke et al., 2011, Ripke et al., 2013, Ripke et al., 2014, Shi et al., 2009, Stefansson et al., 2009) which are implicated in biological processes relating to calcium signaling, immune system function (e.g., many variants in the extended major histocompatibility complex [MHC] region), and long intergenic noncoding RNAs. We have previously shown that one recent genetic variant regulating miR-137 (Green et al., 2013) is associated with a cognitive deficit subtype of schizophrenia. However, the precise functional implication of associated variants remains to be determined, and requires investigation of gene expression regulation, at both transcriptional and post-transcriptional levels. In this study we explore the biological pathways associated with cognitive subtypes of schizophrenia using gene-set analysis of high throughput expression profiles from patient derived PBMCs.

Gene expression changes are evident in several brain regions from post-mortem tissues, and have also been reported in studies using peripheral blood mononuclear cells (PBMCs; for a recent review, see (Sequeira et al., 2012). Findings from both types of study converge on biological processes involved in cell cycle, intracellular signaling, oxidative stress and metabolism, phosphatidylinositol signaling, and ubiquitin proteasome system dysregulation (Bousman et al., 2010, Craddock et al., 2007, McCurdy et al., 2006). Briefly, transcriptome profiling of both fresh PBMCs and lymphoblastoid cell lines have demonstrated unique gene expression signatures related to these processes that discriminate schizophrenia from bipolar disorder, and healthy control groups (Tsuang et al., 2005); more recently, candidate blood biomarkers for two key psychotic symptoms in schizophrenia (hallucinations and delusions) were identified (Kurian et al., 2011), alongside the detection of blood-based gene expression signature using a supervised classifier in association with diagnosis of schizophrenia (Takahashi et al., 2010). Notably, PBMCs play important roles in the immune system, which is increasingly acknowledged in contributing to higher cognitive functions (Wolf et al., 2009). PBMCs express a number of brain associated proteins including receptors for brain derived neurotrophic factor, glucocorticoids, catecholamines, serotonin, dopamine and acetylcholine (McKenna et al., 2002), and many neurons express receptors for signaling molecules of the immune system such as cytokines (Guyon et al., 2008, Kronfol and Remick, 2000, Muller and Ackenheil, 1998).

The emerging studies of PBMCs in schizophrenia have reported dysregulated gene expression of actin assembly factor DAAM2 (Kuzman et al., 2009), a splice variant of NRG1, involved in neurological function and higher levels of sensory and motor neuron derived factor (SMDF) (Petryshen et al., 2005); other implicated genes are involved in processes of neurotransmission and presynaptic function (e.g., dopamine receptor D2 [DRD2]), the inwardly rectifying potassium channel (Kir2.3), and neuropeptide Y (NPY1R) (Middleton et al., 2005a, Vawter et al., 2004a, Zvara et al., 2005). More recently, our study using the largest PBMC cohort to date has reported differential expression of a substantial number of genes involved in the immune system (Gardiner et al., 2013), consistent with a recent mRNA sequencing study implicating a number of immune pathways in schizophrenia, such as antigen presentation and chemokine signaling (Xu et al., 2012).

In this context, there has not yet been a systematic investigation of gene expression profiles associated with putative cognitive subtypes of schizophrenia. While cognitive deficits are a core feature of schizophrenia, there remains substantial heterogeneity among schizophrenia patients in the severity of cognitive impairments. The potential to detect specific biological associations with cognitive subtypes of schizophrenia has been demonstrated in two independent cohorts (Green et al., 2013, Hallmayer et al., 2005, Morar et al., 2011), and in a similar vein, it has been recognised that better use of phenotypic information can increase the power of GWA studies considerably (van der Sluis et al., 2013). In this study we explore the biological pathways associated with cognitive subtypes of schizophrenia using gene-set analysis of high throughput expression profiles from patient derived PBMCs.

Section snippets

Participants

Participant data was obtained from the Australian Schizophrenia Research Bank (ASRB), an established register of participants and research data collected by scientific collaborators across five Australian states and territories, with written informed consent obtained from all participants (Loughland et al., 2010). Ethical approval for this project was obtained from the Hunter Area Health Services Human Research Ethics Committee. ASRB participation required that participants be fluent in English

Results

Demographic, clinical, and cognitive characteristics of the schizophrenia subtypes CS and CD along with healthy controls are presented in Table 1. CS, CD groups and healthy controls showed no differences in age, gender, and RQI (all p > 0.05). ANOVA revealed no difference between CS and CD subtypes in terms of duration of illness or antipsychotic treatment; Fisher’s exact test showed no difference in the type of antipsychotic medications being used by CS and CD subtypes (all p > 0.05). The

Discussion

In this study we investigated transcriptional variation in relation to putative cognitive subtypes in schizophrenia (SZ). In simple gene level analysis, the ‘cognitive deficit’ (CD) subtype showed 130 DEGs, 106 of which were also found to be differentially expressed in the SZ group as a whole; however, the ‘cognitively spared’ (CS) subgroup displayed very little difference to the control group (HC) with only 4 DEGs surviving multiple correction (ZNF827, HINT2, LOC653103, YWHAB). Functional

Role of funding

This research was supported by the Schizophrenia Research Institute, the Hunter Medical Research Institute and the Neurobehavioral Genetics Unit, utilizing infrastructure funding from NSW Ministry of Health. It was supported by a MC Ainsworth Research Fellowship in Epigenetics (MC); a NARSAD Young Investigator Award Samples and clinical and demographic data for this study were provided by the Australian Schizophrenia Research Bank (Chief Investigators: Carr V, Schall U, Scott R, Jablensky A,

Acknowledgments

PBMCs were processed by Melissa Tooney, Trish Collinson, Amy Martin, and Janelle Collins-Langworthy.

References (92)

  • M.R. Kuzman et al.

    Genome-wide expression analysis of peripheral blood identifies candidate biomarkers for schizophrenia

    J. Psychiatr. Res.

    (2009)
  • R.D. McCurdy et al.

    Cell cycle alterations in biopsied olfactory neuroepithelium in schizophrenia and bipolar I disorder using cell culture and gene expression analyses

    Schizophr. Res.

    (2006)
  • F. McKenna et al.

    Dopamine receptor expression on human T- and B-lymphocytes, monocytes, neutrophils, eosinophils and NK cells: a flow cytometric study

    J. Neuroimmunol.

    (2002)
  • S. Mexal et al.

    Differential modulation of gene expression in the NMDA postsynaptic density of schizophrenic and control smokers

    Brain Res. Mol. Brain Res.

    (2005)
  • U. Meyer

    Developmental neuroinflammation and schizophrenia

    Prog. Neuropsychopharmacol. Biol. Psychiatry

    (2013)
  • B.J. Miller et al.

    Meta-analysis of cytokine alterations in schizophrenia: clinical status and antipsychotic effects

    Biol. Psychiatry

    (2011)
  • N. Muller et al.

    Psychoneuroimmunology and the cytokine action in the CNS: implications for psychiatric disorders

    Prog. Neuropsychopharmacol. Biol. Psychiatry

    (1998)
  • S. Potvin et al.

    Inflammatory cytokine alterations in schizophrenia: a systematic quantitative review

    Biol. Psychiatry

    (2008)
  • D.M. Santarelli et al.

    Upregulation of dicer and microRNA expression in the dorsolateral prefrontal cortex Brodmann area 46 in schizophrenia

    Biol. Psychiatry

    (2011)
  • S.G. Schwab et al.

    Further evidence for association of variants in the AKT1 gene with schizophrenia in a sample of European sib-pair families

    Biol. Psychiatry

    (2005)
  • D.R. Seib et al.

    Loss of Dickkopf-1 restores neurogenesis in old age and counteracts cognitive decline

    Cell Stem Cell

    (2013)
  • P.A. Sequeira et al.

    The first decade and beyond of transcriptional profiling in schizophrenia

    Neurobiol. Dis.

    (2012)
  • M. Takahashi et al.

    Diagnostic classification of schizophrenia by neural network analysis of blood-based gene expression signatures

    Schizophr. Res.

    (2010)
  • D.L. Thiselton et al.

    AKT1 is associated with schizophrenia across multiple symptom dimensions in the Irish study of high density schizophrenia families

    Biol. Psychiatry

    (2008)
  • M.P. Vawter et al.

    Microarray screening of lymphocyte gene expression differences in a multiplex schizophrenia pedigree

    Schizophr. Res.

    (2004)
  • J.Q. Wu et al.

    Cognition impairment in schizophrenia patients with tardive dyskinesia: association with plasma superoxide dismutase activity

    Schizophr. Res.

    (2014)
  • J.Q. Wu et al.

    Free radicals, antioxidant defense systems, and schizophrenia

    Prog. Neuropsychopharmacol. Biol. Psychiatry

    (2013)
  • Z. Zhao et al.

    Insulin receptor deficits in schizophrenia and in cellular and animal models of insulin receptor dysfunction

    Schizophr. Res.

    (2006)
  • H.M. Abdul et al.

    Cognitive decline in Alzheimer’s disease is associated with selective changes in calcineurin/NFAT signaling

    J. Neurosci.

    (2009)
  • R. Akaho et al.

    Support for an association between HLA-DR1 and schizophrenia in the Japanese population

    Am. J. Med. Genet.

    (2000)
  • D.B. Allison et al.

    Microarray data analysis: from disarray to consolidation and consensus

    Nat. Rev. Genet.

    (2006)
  • S.N. Bajestan et al.

    Association of AKT1 haplotype with the risk of schizophrenia in Iranian population

    Am. J. Med. Genet. B Neuropsychiatr. Genet.

    (2006)
  • Y. Benjamini et al.

    Controlling the false discovery rate: a practical and powerful approach to multiple testing

    J. R. Stat. Soc. Ser. B

    (1995)
  • C.A. Bousman et al.

    Preliminary evidence of ubiquitin proteasome system dysregulation in schizophrenia and bipolar disorder: convergent pathway analysis findings from two independent samples

    Am. J. Med. Genet. B Neuropsychiatr. Genet.

    (2010)
  • C.A. Bousman et al.

    Negative symptoms of psychosis correlate with gene expression of the WNT/beta-catenin signaling pathway in peripheral blood

    Psychiatry J.

    (2013)
  • R.M. Craddock et al.

    Altered T-cell function in schizophrenia: a cellular model to investigate molecular disease mechanisms

    PLoS One

    (2007)
  • S. de Jong et al.

    Expression QTL analysis of top loci from GWAS meta-analysis highlights additional schizophrenia candidate genes

    Eur. J. Hum. Genet.

    (2012)
  • P. Du et al.

    Lumi: a pipeline for processing Illumina microarray

    Bioinformatics

    (2008)
  • S.L. Eastwood et al.

    Differential expression of calcineurin A subunit mRNA isoforms during rat hippocampal and cerebellar development

    Eur. J. Neurosci.

    (2005)
  • E.S. Emamian et al.

    Convergent evidence for impaired AKT1-GSK3beta signaling in schizophrenia

    Nat. Genet.

    (2004)
  • E. Gardiner et al.

    Imprinted DLK1-DIO3 region of 14q32 defines a schizophrenia-associated miRNA signature in peripheral blood mononuclear cells

    Mol. Psychiatry

    (2012)
  • D.J. Gerber et al.

    Evidence for association of schizophrenia with genetic variation in the 8p21.3 gene, PPP3CC, encoding the calcineurin gamma subunit

    Proc. Natl. Acad. Sci. U.S.A.

    (2003)
  • S.J. Glatt et al.

    Comparative gene expression analysis of blood and brain provides concurrent validation of SELENBP1 up-regulation in schizophrenia

    Proc. Natl. Acad. Sci. U.S.A.

    (2005)
  • M. Gomez Ravetti et al.

    Uncovering molecular biomarkers that correlate cognitive decline with the changes of hippocampus’ gene expression profiles in Alzheimer’s disease

    PLoS One

    (2010)
  • M.J. Green et al.

    Genome-wide supported variant MIR137 and severe negative symptoms predict membership of an impaired cognitive subtype of schizophrenia

    Mol. Psychiatry

    (2013)
  • M.Z. Haider et al.

    Human leukocyte antigen (HLA) DRB1 alleles in Kuwaiti Arabs with schizophrenia

    Am. J. Med. Genet.

    (2000)
  • Cited by (29)

    • Evidence that a working memory cognitive phenotype within schizophrenia has a unique underlying biology.

      2022, Psychiatry Research
      Citation Excerpt :

      This research provides some validation to searching for levels of gene expression in blood that may be differentially associated with clusters of impaired versus intact cognitive performance in subgroups within disorders that include people with clear cognitive impairments, such as schizophrenia. It is therefore significant that one study has reported that blood levels of RNA for genes, which act to suppress WNT signalling could be used to predict cognitive impairment in patients with the disorder (Wu et al., 2016). Another study reported levels of RNA for genes involved in immune or inflammatory mechanisms being linked to deficits in verbal working memory in schizophrenia (Ukkola-Vuoti et al., 2019).

    • Integrating genome-wide association study and methylation functional annotation data identified candidate genes and pathways for schizophrenia

      2020, Progress in Neuro-Psychopharmacology and Biological Psychiatry
      Citation Excerpt :

      Recent evidence indicated that schizophrenia was related to immune reactions caused by prenatal infection exert potential long-lasting immune disturbances, leading to cognitive impairments and neuroanatomical alterations (Kneeland and Fatemi, 2013). A transcriptome study found that the differentially expressed genes of SCZ patients were enriched in immune system process (GO:0002376) (Wu et al., 2016). The cell adhesion molecules (CAMs) pathway was also detected for SCZ.

    • Gene expression changes related to immune processes associate with cognitive endophenotypes of schizophrenia

      2019, Progress in Neuro-Psychopharmacology and Biological Psychiatry
      Citation Excerpt :

      Furthermore, immune pathways, including antigen processing and presentation, genes (MCH-region, e.g. HLA-G gene) showed enrichment in a study of schizophrenia patients with cognitive impairment (Wu et al., 2016). Thus there is a growing body of evidence suggesting that the aetiology of schizophrenia may involve infectious or autoimmune processes from epidemiological (Feigenson et al., 2014), genome-wide loci (Schizophrenia Working Group of the Psychiatric Genomics, 2014), genetic and proteomic (Chan et al., 2017), and gene expression (Gardiner et al., 2013; Schmitt et al., 2011; Wu et al., 2016; Xu et al., 2012) approaches. Several cognitive endophenotypes, including general intelligence, information processing speed, and memory, has been used to study cognitive performance in schizophrenia (Hubbard et al., 2016), and in healthy individuals (Ibrahim-Verbaas et al., 2016; Luciano et al., 2011; Sniekers et al., 2017).

    • HLA typing using genome wide data reveals susceptibility types for infections in a psychiatric disease enriched sample

      2018, Brain, Behavior, and Immunity
      Citation Excerpt :

      It is possible that the repertoire of peptide antigens displayed by the same HLA variant differs between patients with schizophrenia and controls. This mechanism is supported by gene expression and SNP studies in schizophrenia that have implicated genes involved in the molecular pathway for the processing, transport or loading of peptide antigens onto MHC (Fellerhoff and Wank, 2009; Wu et al., 2016). The ubiquitin system is also involved in antigen processing in herpes virus infections (Loureiro and Ploegh, 2006), and hence the dysfunction of protein ubiquitination observed in schizophrenia might also extend to antigen presentation (Rubio et al., 2013).

    View all citing articles on Scopus
    View full text