Post-mortem Brains Of Schizophrenic Patients Research Articles

Altering the expression balance of hnRNP C1 and C2 changes the expression of myelination-related genes

The expression level of hnRNP C1/C2 protein has been reported to be significantly decreased in the post-mortem brain of schizophrenic patients. In this study, we investigated whether overexpression of the hnRNP C variants hnRNP C1 and C2 changed the expression of myelination-related genes in the human neuroblastoma cell line SK-N-SH. In both hnRNP C1- and C2-overexpressing cells, the expression of quaking (QKI)-6 and QKI-7 significantly increased or decreased compared to the control, respectively. Intriguingly, QKI-5 and myelin basic protein were markedly up- or down-regulated by overexpressing hnRNP C2, respectively. Our findings are the first to demonstrate distinct functions of hnRNP C1 and C2, and may be helpful in understanding the functions of these molecules. These findings indicate that altered expression levels of hnRNP C in the brain of patients with schizophrenia could be involved in the pathophysiology of this disease through alteration of the QKI isoform and myelin basic protein expression.

A putative cis-acting polymorphism in the NOS1 gene is associated with schizophrenia and NOS1 immunoreactivity in the postmortem brain

Schizophrenia is a devastating neurodevelopmental disorder whose genetic influences remain elusive. Recent genome-wide scans revealed that rare structural variants disrupted multiple genes in neurodevelopmental pathways, which strongly implicate nitric oxide (NO) signaling in schizophrenia. NO acts as a second messenger of N-methyl-D aspartate receptor activation, which further interacts with both dopaminergic and serotonergic pathways. NO is mainly synthesized by neuronal nitric oxide synthase (NOS1) in the brain, and its gene locus, 12q24.2, has attracted much attention as a major linkage region for schizophrenia. Genetic variations of NOS1 have also been associated with schizophrenia, and differential expression of NOS1 was observed in the postmortem brain of schizophrenic patients. Here, we explored the hypothesis that a putative cis-acting G-84A single nucleotide polymorphism (SNP; rs41279104) in the exon 1c promoter region of the NOS1 gene is associated with the levels of NOS1 immunoreactivity in postmortem prefrontal cortex specimens regardless of disease phenotype. Individuals with the A-allele of this SNP showed significantly lower levels of NOS1 immunoreactivity than did GG homozygotes ( p = 0.002). Furthermore, a case–control study using 720 individuals in a Japanese population revealed a significant association between the SNP and schizophrenia (genotypic p = 0.0013 and allelic p = 0.0011). Additionally, the average of onset age in schizophrenic patients with the A-allele was significantly earlier than GG homozygotes ( p = 0.018). When the analyses took gender into account, this significance was more significant for female. These findings provide further evidences that NOS1 is associated with a biological susceptibility gene to schizophrenia.

Postnatal effect of embryonic neurogenesis disturbance on reelin level in organotypic cultures of rat hippocampus

Despite a delayed emergence of the symptoms, schizophrenia is thought to be a late consequence of early disturbances during development. Several reports have found decreased levels of reelin in the cortex and the hippocampus of postmortem brains of schizophrenic patients. In the rat, intraperitoneal injection of the anti-mitotic agent methylazoxymethanol (MAM) during intra-uterine development (embryonic day 17) induces cytoarchitectural abnormalities in the hippocampus and the cortex and behavioural changes reminiscent of positive, negative and cognitive symptoms of schizophrenia. We aimed to examine whether a transient prenatal disturbance of neurogenesis induces postnatal changes in the expression of reelin in the hippocampus. Cellular modifications were explored using hippocampal organotypic slice cultures, which allow for conservation of the in vivo cytoarchitecture. MAM effect on hippocampal neurogenesis was confirmed by birthdating experiments. After 3 weeks in vitro, reelin was expressed by calretinin-negative cells. The number of reelin-positive neurons was increased whereas the total neuron number was decreased in the stratum oriens in the E17 MAM-exposed animals as compared to the control group. Not only an increase in the number of cells expressing reelin was observed, but there was also a slight increase in reelin mRNA levels in hippocampal pyramidal cells of MAM-exposed animals. In contrast, there was no significant change in the dentate gyrus. These results show that transient prenatal disturbance of neurogenesis induces long-term modifications in specific areas of the hippocampus and in particular in the number of neurons expressing reelin. They also confirm the value of organotypic slices to study postnatal maturation in the hippocampus.

Hypermethylation of the reelin (RELN) promoter in the brain of schizophrenic patients: A preliminary report

DNA methylation changes could provide a mechanism for DNA plasticity and dynamism for short-term adaptation, enabling a type of cell memory to register cellular history under different environmental conditions. Some environmental insults may also result in pathological methylation with corresponding alteration of gene expression patterns. Evidence from several studies has suggested that in schizophrenia and bipolar disorder, mRNA of the reelin gene (RELN), which encodes a protein necessary for neuronal migration, axonal branching, synaptogenesis, and cell signaling, is severely reduced in post-mortem brains. Therefore, we investigated the methylation status of the RELN promoter region in schizophrenic patients and normal controls as a potential mechanism for down regulation of its expression. Ten post-mortem frontal lobe brain samples from male schizophrenic patients and normal controls were obtained from the Harvard Brain Tissue Resources Center. DNA was extracted using a standard phenol-chloroform DNA extraction protocol. To evaluate differences between patients and controls, we applied methylation specific PCR (MSP) using primers localized to CpG islands flanking a potential cyclic AMP response element (CRE) and a stimulating protein-1 (SP1) binding site located in the promoter region. For each sample, DNA extraction, bisulfite treatment, and MSP were independently repeated at least four times to accurately determine the methylation status of the target region. Forty-three PCR trials were performed on the test and control samples. MSP analysis of the RELN promoter revealed an unmethylated signal in all reactions (43 of 43) using DNA from the frontal brain tissue, derived from either the schizophrenic patients or normal controls indicating that this region of the RELN promoter is predominantly unmethylated. However, we observed a distinct methylated signal in 73% of the trials (16 of 22) in schizophrenic patients compared with 24% (5 of 21) of controls. Thus, the hypermethylation of the CpG islands flanking a CRE and SP1 binding site observed at a significantly higher level (t = -5.07, P = 0.001) may provide a mechanism for the decreased RELN expression, frequently observed in post-mortem brains of schizophrenic patients. We also found an inverse relationship between the level of DNA methylation using MSP analysis and the expression of the RELN gene using semi-quantitative RT-PCR. Despite the small sample size, these studies indicate that promoter hypermethylation of the RELN gene could be a significant contributor in effecting epigenetic alterations and provides a molecular basis for the RELN gene hypoactivity in schizophrenia. Further studies with a larger sample set would be required to validate these preliminary observations.

Low GSK-3β in schizophrenia as a consequence of neurodevelopmental insult

Glycogen synthase kinase-3 (GSK-3) is a protein kinase highly abundant in brain and involved in signal transduction cascades, particularly neurodevelopment. Its activity and protein levels have been reported to be over 40% lower in postmortem frontal cortex of schizophrenic patients. GSK-3β in occipital cortex of schizophrenic patients was not reduced, suggesting regional specificity. There was no reduction in GSK-3β protein levels in fresh and immortalized lymphocytes and both GSK-3 activity and GSK-3β mRNA levels in fresh lymphocytes from schizophrenic patients. In the schizophrenia-related neonatal ventral hippocampal lesion rat model, we measured GSK-3β protein levels and GSK-3 activity in the frontal cortex. GSK-3β protein levels in lesioned rats were significantly lower than in sham rats, favoring perinatal insult as a cause of low GSK-3β in schizophrenia. Taken together, these studies suggest that low GSK-3 in postmortem brain of schizophrenic patients is a late consequence of perinatal neurodevelopmental insult in schizophrenia. In rats, acute or chronic cold restraint stress did not change GSK-3β protein levels. Chronic treatment of rats with lithium, valproate, haloperidol or clozapine did not change rat cortical GSK-3β protein levels ex vivo, supporting the concept that low GSK-3β in schizophrenia is not secondary to stress or drug treatment. Our initial findings of low GSK-3β protein levels in postmortem brain have been replicated by another group. Our own group has found additionally that GSK-3β mRNA levels were 40% lower in postmortem dorsolateral prefrontal cortex (DLPFC) of schizophrenic patients, supporting our previous findings. Further studies will be aimed at determining whether nonspecific neonatal damage or only specific factors cause low GSK-3 as a late effect. We plan to study whether low GSK-3β activity is associated with biochemical effects such as elevated β-catenin levels.

Differential effects of long-term treatment with clozapine or haloperidol on GABA A receptor binding and GAD 67 expression

One of the most consistent findings in postmortem studies of schizophrenia is increased GABA A receptor binding and reduced glutamic acid decarboxylase (GAD 67) expression. Due to long-term antipsychotic treatment before death, these findings may reflect not only the consequences of schizophrenia but also medication effects. To differentiate between these options, we used an animal model and evaluated long-term effects of typical (haloperidol) and atypical (clozapine) antipsychotic drugs on the GABAergic system. A total of 33 adult male rats were treated in three cohorts over a period of 6 months. One cohort of 11 animals received clozapine (45 mg/kg/day), another one received haloperidol (1.5 mg/kg/day) and a third one received pH-adapted minimal concentrations of HCl in the drinking water. Receptor autoradiography of the GABA A receptor ([ 3H]-muscimol binding) and in situ hybridization in adjacent sections with 35S-labeled cRNA probes of the γ-aminobutyric acid (GABA)-producing enzyme, GAD 67, was performed. While haloperidol increased GABA A receptor binding in striatum and nucleus accumbens (NA), it suppressed GABA A receptor binding in temporal (TEMPC) and parietal (PARC) cortex. Clozapine induced GABA A receptor binding in infralimbic cortex (ILC) and similar like haloperidol in anterior cingulate cortex (ACC), two regions of the limbic cortex. In addition, either drug increased gene expression of GAD 67. It is concluded that antipsychotic drugs differentially alter the GABAergic system, strongly suggesting that drug effects are partially responsible for the up-regulation of GABA A receptor binding in certain brain regions as observed in postmortem brains of schizophrenic patients. However, the reduced GAD 67 expression seen in postmortem brains does not appear to reflect drug effects, since our animal model demonstrated increased gene expression.

Selective reduction of a PDZ protein, SAP‐97, in the prefrontal cortex of patients with chronic schizophrenia

Many postsynaptic density proteins carrying postsynaptic density-95/discs large/zone occludens-1 (PDZ) domain(s) interact with glutamate receptors to control receptor dynamics and synaptic plasticity. Here we examined the expression of PDZ proteins, synapse-associated protein (SAP) 97, postsynaptic density (PSD)-95, chapsyn-110, GRIP1 and SAP102, in post-mortem brains of schizophrenic patients and control subjects, and evaluated their contribution to schizophrenic pathology. Among these PDZ proteins, SAP97 exhibited the most marked change: SAP97 protein levels were decreased to less than half that of the control levels specifically in the prefrontal cortex of schizophrenic patients. In parallel, its binding partner, GluR1, similarly decreased in the same brain region. The correlation between SAP97 and GluR1 levels in control subjects was, however, altered in schizophrenic patients. SAP102 levels were also significantly reduced in the hippocampus of schizophrenic patients, but this reduction was correlated with sample storage time and post-mortem interval. There were no changes in the levels of the other PDZ proteins in any of the regions examined. In addition, neuroleptic treatment failed to mimic the SAP97 change. These findings suggest that a phenotypic loss of SAP97 is associated with the postsynaptic impairment in prefrontal excitatory circuits of schizophrenic patients.

Multicolor fluorescent in situ hybridization on post-mortem brain in schizophrenia as an approach for identification of low-level chromosomal aneuploidy in neuropsychiatric diseases

Fluorescence in situ hybridization (FISH) of DNA-DNA or DNA-RNA using post-mortem brain samples is one approach to study low-level chromosomal aneuploidy and selective expression of specific genes in the brain of patients with neuropsychiatric diseases. We have performed a pilot molecular-cytogenetic analysis of post-mortem brain of schizophrenic patients. Multicolor FISH on two post-mortem brain samples of normal individuals and six schizophrenic individuals (area 10 of cortex) was applied. A set of DNA probes for FISH included: (i) centromeric alphoid DNA probes for chromosomes 7, 8, 13 and 21, 18, X and Y; (ii) classical satellite DNA probes for chromosomes 1 and 16; and (iii) region-specific DNA probes for chromosomes 13, 21 and 22. A statistically significant level of aneuploidy (up to 0.5–4% of neurons) involving chromosomes X and 18 was detected in two post-mortem brains of patients with schizophrenia. These results indicate that low-level chromosomal aneuploidy could be involved in the pathogenesis of schizophrenia. FISH could be applied to extended studies of chromosomal aneuploidy, abnormal patterns of chromosomal organization and functional gene expression in situ in the neurons of the brain in different psychiatric and neurodevelopmental diseases. Schizophrenia and Rett syndrome might be considered as psychiatric diseases of special interest for molecular-cytogenetic analysis as both of them could be associated with mutations in genes involving regulation of neurodevelopmental processes in the brain.

Viral link to schizophrenia

Unexpectedly high levels of retroviral RNA have been detected in the cerebrospinal fluid of people suffering from schizophrenia, according to a recent study published in Proceedings of the National Academy of Sciences. Robert Yolken and colleagues (John Hopkins School of Medicine, Baltimore, MD, USA) also detected the viral RNA in samples taken from post-mortem brains of schizophrenic patients. Control samples from normal individuals contained no trace of the pathogen. The RNA detected was produced by HERV-W, an endogenous retrovirus. The authors speculate that re-activation of these latent components of the human genome might contribute to the pathology of schizophrenia. If this theory is proven, it could lead to new strategies for the treatment of this neurological condition. PoN

Abnormal expression of brain-derived neurotrophic factor and its receptor in the corticolimbic system of schizophrenic patients.

Previous neuropathological studies have revealed that the corticolimbic system of schizophrenic patients expresses abnormal levels of various synaptic molecules, which are known to be influenced by the neuronal differentiation factors, neurotrophins. Therefore, we determined levels of neurotrophins and their receptors in the postmortem brains of schizophrenic patients and control subjects in relation to molecular impairments in schizophrenia. Among the neurotrophins examined, levels of brain-derived neurotrophic factor (BDNF) were elevated specifically in the anterior cingulate cortex and hippocampus of schizophrenic patients, but levels of nerve growth factors and neurotrophin-3 showed no change in any of the regions examined. In parallel, the expressions of TrkB receptor and calbindin-D, which are both influenced by BDNF, were reduced significantly in the hippocampus or the prefrontal cortex. However, neuroleptic treatment did not appear to mimic the neurotrophic change. Neither withdrawal of drug treatment in patients nor chronic administration of haloperidol to rats altered levels of BDNF. These findings suggest that neurotrophic abnormality is associated with the corticolimbic structures of schizophrenic patients and might provide the molecular substrate for pathological manifestations of the illness.

Schizophrenia and the serotonin-2A receptor promoter polymorphism

Serotonin-2A (5-HT 2A) receptors have received much investigative attention in schizophrenia because (1) several studies have shown a decrease in the number of 5-HT 2A receptors in the prefrontal cortex of postmortem brains of schizophrenic patients; (2) atypical antipsychotic drugs are antagonists for 5-HT 2A receptors; and (3) a positive association between a T to C polymorphism at position 102 of the 5-HT 2A receptor gene and schizophrenia has been reported. A G to A polymorphism at position −1438 of the 5-HT 2A receptor gene was studied in 119 schizophrenic patients and 106 healthy control subjects, all of whom were Japanese. The genotype and allele frequencies did not differ between the patients and control subjects. Furthermore, the genotype frequency did not differ according to diagnostic subtype, family history, age at onset of illness, or daily dosage of antipsychotic medication. Our results suggest that the polymorphism does not contribute to the etiology or clinical characteristics of schizophrenia. However, the gene is greater than 20 kbp in length, and thus it is possible that other areas that affect expression of the gene may vary. We found that the −1438G/A variant was in linkage disequilibrium with the T102C polymorphism.

Inositol levels are decreased in postmortem brain of schizophrenic patients

Background: A previous study reported decreased levels of inositol in frontal cortex of postmortem brain from bipolar patients and suicide victims. The aim of the present study was to test the specificity of this finding. Methods: Inositol and the enzyme that synthesizes it, inositol monophosphatase, were measured in postmortem brain tissue from frontal and occipital cortex and cerebellum from 10 schizophrenic patients and the previously reported controls. Inositol levels were assayed gas-chromatographically as trimethylsilyl derivatives with mannitol as an internal standard. Inositol monophosphatase activity in brain homogenates was measured as the difference between phosphate release from inositol-1-phosphate in the absence and in the presence of Li +. Results: Inositol was significantly reduced in all three areas in the schizophrenic patients’ brains; inositol monophosphatase was unchanged. Postmortem interval did not correlate with inositol levels and did not differ between control group and schizophrenic patients. Conclusions: These results suggest an abnormality of second messenger precursor availability in common with schizophrenia and affective psychopathology.

Iron, copper, zinc, magnesium, and calcium in postmortem brain tissue from schizophrenic patients

The regional distribution of iron, copper, zinc, magnesium, and calcium in postmortem brain of schizophrenic patients was compared with that of matched controls. In none of the brain regions investigated (caudate nucleus, hippocampus, amygdala, cortex, corpus mamillare, gyrus cinguli, and hypothalamus) were significant differences observed between these two groups. In the total group, region-specific differences were found for iron, copper, zinc, and calcium, but not for magnesium. Gender differences were observed only for zinc. There was no correlation between a neuroleptic-free period before death and the content of any of the metals investigated, except for a positive correlation between copper in the hippocampus and a neuroleptic-free period. The results of the present study suggest that there are no profound differences in the content of iron, copper, zinc, magnesium, and calcium in postmortem brains between controls and schizophrenic patients.

Increased prevalence of the cavum septum pellucidum in magnetic resonance scans and post-mortem brains of schizophrenic patients

A cavum septum pellucidum (CSP) has been regarded as an incidental finding of little clinical importance. However, an association between this developmental anomaly and a diagnosis of psychosis has previously been reported. We determined the prevalence of the CSP in parallel studies of brain scans obtained with magnetic resonance (MR) imaging and in the post-mortem brains of schizophrenic patients compared with normal controls. We found a significantly increased prevalence of the CSP in both the MR scans and postmortem brains of schizophrenic patients compared with controls. In the MR study, 17 of 81 (21%) schizophrenic patients but only 1 of 46 (2%) control subjects had a CSP. In the post-mortem study, 17 of 28 (61%) schizophrenic patients and 12 of 39 (31%) normal controls had a CSP. The increased prevalence of a CSP in schizophrenic patients further indicates that anomalous development of the limbic system is an important aspect of this disorder.

Increased prevalence of the cavum septum pellucidum in MRI scans and postmortem brains of schizophrenic patients

Increased prevalence of the cavum septum pellucidum in MRI scans and postmortem brains of schizophrenic patients

Search for cytomegalovirus in the post-mortem brains of schizophrenic patients using the polymerase chain reaction

Search for cytomegalovirus in the post-mortem brains of schizophrenic patients using the polymerase chain reaction