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Peripheral samples, such as blood and skin, have been used for decades in psychiatric research as surrogates for central nervous system samples. Although the validity of the data obtained from peripheral samples has been questioned and other state-of-the-art techniques, such as human brain imaging, genomics, and induced pluripotent stem cells, seem to reduce the value of peripheral cells, accumulating evidence has suggested that revisiting peripheral samples is worthwhile. Here, we re-evaluate the utility of peripheral samples and argue that establishing an understanding of the common signaling and biological processes in the brain and peripheral samples is required for the validity of such models. First, we present an overview of the available types of peripheral cells and describe their advantages and disadvantages. We then briefly summarize the main achievements of omics studies, including epigenome, transcriptome, proteome, and metabolome analyses, as well as the main findings of functional cellular assays, the results of which imply that alterations in neurotransmission, metabolism, the cell cycle, and the immune system may be partially responsible for the pathophysiology of major psychiatric disorders such as schizophrenia. Finally, we discuss the future utility of peripheral samples for the development of biomarkers and tailor-made therapies, such as multimodal assays that are used as a battery of disease and trait pathways and that might be potent and complimentary tools for use in psychiatric research. [ABSTRACT FROM AUTHOR]

Background: Schizophrenia and bipolar disorder together affect approximately 2.5% of the world population, and their etiologies are thought to involve multiple genetic variants and environmental influences. The analysis of gene expression patterns in brain may provide a characteristic signature for each disorder. Methods: RNA samples from the dorsolateral prefrontal cortex (Brodmann area 46) consisting of individuals with schizophrenia (SZ), bipolar disorder (BPD), and control subjects were tested on the Codelink Human 20K Bioarray platform. Selected transcripts were validated by quantitative real-time polymerase chain reaction (PCR). The strong effects of age, gender, and pH in the analysis of differential gene expression were controlled by analysis of covariance (ANCOVA). Criteria for differential gene expression were 1) a gene was significantly dysregulated in both BPD and SZ compared with control subjects and 2) significant in ANCOVA analysis with samples that have a pH above the median of the sample. Results: A list of 78 candidate genes passed these two criteria in BPD and SZ and was overrepresented for functional categories of nervous system development, immune system development and response, and cell death. Five dysregulated genes were confirmed with quantitative Q-PCR in both BPD and SZ. Three genes were highly enriched in brain expression (AGXT2L1, SLC1A2, and TU3A). The distribution of AGXT2L1 expression in control subjects versus BPD and SZ was highly significant (Fisher''s Exact Test, p < 10−06). Conclusions: These results suggest a partially shared molecular profile for both disorders and offer a window into discovery of common pathophysiology that might lead to core treatments. [Copyright &y& Elsevier]

There are major concerns that specific agonal conditions, including coma and hypoxia, might affect ribonucleic acid (RNA) integrity in postmortem brain studies. We report that agonal factors significantly affect RNA integrity and have a major impact on gene expression profiles in microarrays. In contrast to agonal factors, gender, age, and postmortem factors have less effect on gene expression profiles. The Average Correlation Index is proposed as a method for evaluating RNA integrity on the basis of similarity of microarray profiles. Reducing the variance due to agonal factors is critical in investigating small but validated gene expression differences in messenger RNA levels between psychiatric patients and control subjects. [Copyright &y& Elsevier]

• Homer1a , but not the long variant of the Homer1 gene, exhibits robust circadian oscillation in mouse brain. • Circadian oscillation of Homer1a gene is independent of core clock regulator BMAL1. • Response of Homer1a gene to sleep deprivation stress is blunted in the absence of BMAL1. • Phosphorylation of CREB is attenuated in brain of Bmal1 -null mice, and is recovered by sleep deprivation stress. Accumulating evidence points to a significant link between disrupted circadian rhythms and neuronal disfunctions, though the molecular mechanisms underlying this connection are virtually unexplored. The transcript Homer1a , an immediate early gene related to postsynaptic signaling, has been demonstrated to exhibit robust circadian oscillation in the brain, which supports the hypothesis that Homer1a mediates the communication between circadian inputs and neuronal activity. Here, we determined how the circadian clock is implicated in Homer1a gene regulation by using circadian clock Bmal1 -mutant mice either in the presence or absence of stress stimulation. The Homer1 gene generates multiple transcripts, but only the short variant Homer1a responds to acute stress with sleep deprivation (SD) in mice. Chromatin immunoprecipitation assays revealed that both transcription factor CREB and the circadian clock component BMAL1 bind to the Homer1 promoter in mouse brain. Importantly, circadian Homer1a gene expression is unaltered in the absence of BMAL1, while its immediate early response to SD relies on BMAL1. Deletion of Bmal1 results in attenuated CREB activity in mouse brain, which appears to contribute to decreased expression of Homer1a in response to SD. In conclusion, Homer1a undergoes bimodal control by the circadian clock and CREB. [ABSTRACT FROM AUTHOR]

Background: miR-137 dysregulation has been implicated in the etiology of schizophrenia, but its functional role remains to be determined. Methods: Functional magnetic resonance imaging scans were acquired on 48 schizophrenia patients and 63 healthy volunteers (total sample size N = 111 subjects), with similar mean age and sex distribution, while subjects performed a Sternberg Item Response Paradigm with memory loads of one, three, and five numbers. Dorsolateral prefrontal cortex (DLPFC) retrieval activation for the working memory load of three numbers, for which hyperactivation had been shown in schizophrenia patients compared with control subjects, was extracted. The genome-wide association study confirmed schizophrenia risk single nucleotide polymorphism rs1625579 (miR-137 locus) was genotyped (schizophrenia: GG n = 0, GT n = 9, TT n = 39; healthy volunteers: GG = 2, GT n = 15, and TT n = 46). Fisher’s exact test examined the effect of diagnosis on rs1625579 allele frequency distribution (p = nonsignificant). Mixed model regression analyses examined the effects of diagnosis and genotype on working memory performance measures and DLPFC activation. Results: Patients showed significantly higher left DLPFC retrieval activation on working memory load 3, lower working memory performance, and longer response times compared with controls. There was no effect of genotype on working memory performance or response times in either group. However, individuals with the rs1625579 TT genotype had significantly higher left DLPFC activation than those with the GG/GT genotypes. Conclusions: Our study suggests that the rs1625579 TT (miR-137 locus) schizophrenia risk genotype is associated with the schizophrenia risk phenotype DLPFC hyperactivation commonly considered a measure of brain inefficiency. [ABSTRACT FROM AUTHOR]

In this study, the authors sought to replicate the findings of reduced synaptosomal associated protein 25 kDa (SNAP-25) immunoreactivity in the hippocampus of patients with schizophrenia. The authors also measured N-methyl-d-aspartate (NMDA) receptor 1 (NR1) receptor subunit to determine if glutamatergic synapses were involved with the loss of SNAP-25. We found 49% less SNAP-25 immunointensity in the schizophrenic group (n=7) compared to the control (n=8) or bipolar groups (n=4) (P=.004). There was no change in NMDA NR1 levels in the three groups. The authors confirm the previous report of less SNAP-25 immunoreactivity in the hippocampus using a different cohort of patients with schizophrenia. It also appears that NMDA NR1 was unchanged, indicating that the overall level of NMDA glutamatergic synapses in hippocampus is normal. These data add to evidence suggesting that in schizophrenia the molecular pathology of the hippocampus involves presynaptic components. [Copyright &y& Elsevier]

Background The genetic risk factors of schizophrenia (SCZ), a severe psychiatric disorder, are not yet fully understood. Multiple lines of evidence suggest that mitochondrial dysfunction may play a role in SCZ, but comprehensive association studies are lacking. We hypothesized that variants in nuclear-encoded mitochondrial genes influence susceptibility to SCZ. Methods We conducted gene-based and gene-set analyses using summary association results from the Psychiatric Genomics Consortium Schizophrenia Phase 2 (PGC-SCZ2) genome-wide association study comprising 35,476 cases and 46,839 control subjects. We applied the MAGMA method to three sets of nuclear-encoded mitochondrial genes: oxidative phosphorylation genes, other nuclear-encoded mitochondrial genes, and genes involved in nucleus-mitochondria crosstalk. Furthermore, we conducted a replication study using the iPSYCH SCZ sample of 2290 cases and 21,621 control subjects. Results In the PGC-SCZ2 sample, 1186 mitochondrial genes were analyzed, among which 159 had p values < .05 and 19 remained significant after multiple testing correction. A meta-analysis of 818 genes combining the PGC-SCZ2 and iPSYCH samples resulted in 104 nominally significant and nine significant genes, suggesting a polygenic model for the nuclear-encoded mitochondrial genes. Gene-set analysis, however, did not show significant results. In an in silico protein-protein interaction network analysis, 14 mitochondrial genes interacted directly with 158 SCZ risk genes identified in PGC-SCZ2 (permutation p = .02), and aldosterone signaling in epithelial cells and mitochondrial dysfunction pathways appeared to be overrepresented in this network of mitochondrial and SCZ risk genes. Conclusions This study provides evidence that specific aspects of mitochondrial function may play a role in SCZ, but we did not observe its broad involvement even using a large sample. [ABSTRACT FROM AUTHOR]

Background Conventional antidepressants usually require several weeks to achieve a full clinical response in patients with major depressive disorder, an illness associated with dysregulated circadian rhythms and a high incidence of suicidality. Two rapid-acting antidepressant strategies, low-dose ketamine (KT) and sleep deprivation (SD) therapies, dramatically reduce depressive symptoms within 24 hours in a subset of major depressive disorder patients. However, it is unknown whether they exert their actions through shared regulatory mechanisms. To address this question, we performed comparative transcriptomics analyses to identify candidate genes and relevant pathways common to KT and SD. Methods We used the forced swim test, a standardized behavioral approach to measure antidepressant-like activity of KT and SD. We investigated gene expression changes using high-density microarrays and pathway analyses (Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, Gene Set Enrichment Analysis) in KT- and SD-treated mice compared with saline-treated control male mice. Results We show that KT and SD elicit common transcriptional responses implicating distinct elements of the circadian clock and processes involved in neuronal plasticity. There is an overlap of 64 genes whose expression is common in KT and SD. Specifically, there is downregulation of clock genes including Ciart, Per2, Npas4, Dbp, and Rorb in both KT- and SD-treated mice. Conclusions We demonstrate a potential involvement of the circadian clock in rapid antidepressant responses. These findings could open new research avenues to help design chronopharmacological strategies to treat major depressive disorder. [ABSTRACT FROM AUTHOR]

Major depressive disorder (MDD) is a leading cause of disability worldwide characterized by altered neuronal activity in brain regions involved in the control of stress and emotion. Although multiple lines of evidence suggest that altered stress-coping mechanisms underlie the etiology of MDD, the homeostatic control of neuronal excitability in MDD at the molecular level is not well established. In this review, we examine past and current evidence implicating dysregulation of the polyamine system as a central factor in the homeostatic response to stress and the etiology of MDD. We discuss the cellular effects of abnormal metabolism of polyamines in the context of their role in sensing and modulation of neuronal, electrical, and synaptic activity. Finally, we discuss evidence supporting an allostatic model of depression based on a chronic elevation in polyamine levels resulting in self-sustained stress response mechanisms maintained by maladaptive homeostatic mechanisms. [ABSTRACT FROM AUTHOR]

Abstract: The geographic origins of populations can be identified by their maternally inherited mitochondrial DNA (mtDNA) haplogroups. This study compared human cybrids (cytoplasmic hybrids), which are cell lines with identical nuclei but mitochondria from different individuals with mtDNA from either the H haplogroup or L haplogroup backgrounds. The most common European haplogroup is H while individuals of maternal African origin are of the L haplogroup. Despite lower mtDNA copy numbers, L cybrids had higher expression levels for nine mtDNA-encoded respiratory complex genes, decreased ATP (adenosine triphosphate) turnover rates and lower levels of reactive oxygen species production, parameters which are consistent with more efficient oxidative phosphorylation. Surprisingly, GeneChip arrays showed that the L and H cybrids had major differences in expression of genes of the canonical complement system (5 genes), dermatan/chondroitin sulfate biosynthesis (5 genes) and CCR3 (chemokine, CC motif, receptor 3) signaling (9 genes). Quantitative nuclear gene expression studies confirmed that L cybrids had (a) lower expression levels of complement pathway and innate immunity genes and (b) increased levels of inflammation-related signaling genes, which are critical in human diseases. Our data support the hypothesis that mtDNA haplogroups representing populations from different geographic origins may play a role in differential susceptibilities to diseases. [Copyright &y& Elsevier]

Abstract: MicroRNAs (miRNAs) are small non-coding RNAs that act as potent regulators of gene expression. A recent GWAS reported the rs1625579 SNP, located downstream of miR-137, as the strongest new association with schizophrenia [Ripke S, Sanders AR, Kendler KS, Levinson DF, Sklar P, Holmans PA, et al. Genome-wide association study identifies five new schizophrenia loci. Nat Genet 2011;43:969–76.]. Prior to this GWAS finding, a schizophrenia imaging-genetic study found miR-137 target genes significantly enriched for association with activation in the dorsolateral prefrontal cortex (DLPFC) [Potkin SG, Macciardi F, Guffanti G, Fallon JH, Wang Q, Turner JA, et al. Identifying gene regulatory networks in schizophrenia. Neuroimage 2010;53:839–47.]. We investigated the expression levels of miR-137 and three candidate target genes (ZNF804A, CACNA1C, TCF4) in the DLPFC of postmortem brain tissue from 2 independent cohorts: (1) 26 subjects (10 control (CTR), 7 schizophrenia (SZ), 9 bipolar disorder (BD)) collected at the UCI brain bank; and (2) 99 subjects (33 CTR, 35 SZ, 31 BD) obtained from the Stanley Medical Research Institute (SMRI). MiR-137 expression in the DLPFC did not differ between diagnoses. We also explored the relationship between rs1625579 genotypes and miR-137 expression. Significantly lower miR-137 expression levels were observed in the homozygous TT subjects compared to TG and GG subjects in the control group (30% decrease, p-value = 0.03). Moreover, reduced miR-137 levels in TT subjects corresponded to increased levels of the miR-137 target gene TCF4. The miR-137 expression pattern in 9 brain regions was significant for regional effect (ANOVA p-value = 1.83E-12), with amygdala and hippocampus having the highest miR-137 expression level. In conclusion, decreased miR-137 expression is associated with the SZ risk allele of rs1625579, and potential regulation of TCF4, another SZ candidate gene. This study offers additional support for involvement of miR-137 and downstream targets as mechanisms of risk for psychiatric disorders. [Copyright &y& Elsevier]

Abstract: Gene expression profiles of postmortem brain tissue represent important resources for understanding neuropsychiatric illnesses. The impact(s) of quality covariables on the analysis and results of gene expression studies are important questions. This paper addressed critical variables which might affect gene expression in two brain regions. Four broad groups of quality indicators in gene expression profiling studies (clinical, tissue, RNA, and microarray quality) were identified. These quality control indicators were significantly correlated, however one quality variable did not account for the total variance in microarray gene expression. The data showed that agonal factors and low pH correlated with decreased integrity of extracted RNA in two brain regions. These three parameters also modulated the significance of alterations in mitochondrial-related genes. The average F-ratio summaries across all transcripts showed that RNA degradation from the AffyRNAdeg program accounted for higher variation than all other quality factors. Taken together, these findings confirmed prior studies, which indicated that quality parameters including RNA integrity, agonal factors, and pH are related to differences in gene expression profiles in postmortem brain. Individual candidate genes can be evaluated with these quality parameters in post hoc analysis to help strengthen the relevance to psychiatric disorders. We find that clinical, tissue, RNA, and microarray quality are all useful variables for collection and consideration in study design, analysis, and interpretation of gene expression results in human postmortem studies. [Copyright &y& Elsevier]

Stimulation of group I metabotropic glutamate receptors (mGluRs) has been shown to protect against N-methyl-d-aspartate receptor-mediated cell death, but the underlying cellular mechanism is unknown. Using cDNA microarrays we have now compared gene expressions in organotypic hippocampal slice cultures after neuroprotective activation of group I mGluRs with (S)-3,5-dihydroxyphenylglycine (DHPG; 10 μM, 2 h) with untreated control cultures. Total RNA was extracted from the cultures immediately after the neuroprotective treatment, reverse transcribed to cDNA with incorporation of [32]P-dCTP, and then hybridized to the arrays. Of a total of 1128 genes on the Neuroarray, 33 genes displayed significant changes in expression after DHPG-treatment (six up- and 27 downregulated). These genes have been associated with regulation of synaptic excitation, inflammation, cell adhesion, cell death, and transcription. The small GTPase RAB5B associated with endocytosis emerged as a primary candidate gene for neuroprotection, and its expression was confirmed by Western blot analysis and real time polymerase chain reaction. By providing insight into genes involved in neuroprotection these data may help to identify novel therapeutic targets. [Copyright &y& Elsevier]