Somal size of immunolabeled pyramidal cells in the prefrontal cortex of subjects with schizophrenia

NECAB family of neuronal calcium-binding proteins in health and disease

The N-terminal EF-hand calcium-binding proteins 1-3 (NECAB1-3) constitute a family of predominantly neuronal proteins characterized by the presence of at least one EF-hand calcium-binding domain and a functionally less well characterized C-terminal antibiotic biosynthesis monooxygenase domain. All three family members were initially discovered due to their interactions with other proteins. NECAB1 associates with synaptotagmin-1, a critical neuronal protein involved in membrane trafficking and synaptic vesicle exocytosis. NECAB2 interacts with predominantly striatal G-protein-coupled receptors, while NECAB3 partners with amyloid-β A4 precursor protein-binding family A members 2 and 3, key regulators of amyloid-β production. This demonstrates the capacity of the family for interactions with various classes of proteins. NECAB proteins exhibit distinct subcellular localizations: NECAB1 is found in the nucleus and cytosol, NECAB2 resides in endosomes and the plasma membrane, and NECAB3 is present in the endoplasmic reticulum and Golgi apparatus. The antibiotic biosynthesis monooxygenase domain, an evolutionarily ancient component, is akin to atypical heme oxygenases in prokaryotes but is not well-characterized in vertebrates. Prokaryotic antibiotic biosynthesis monooxygenase domains typically form dimers, suggesting that calcium-mediated conformational changes in NECAB proteins may induce antibiotic biosynthesis monooxygenase domain dimerization, potentially activating some enzymatic properties. However, the substrate for this enzymatic activity remains uncertain. Alternatively, calcium-mediated conformational changes might influence protein interactions or the subcellular localization of NECAB proteins by controlling the availability of protein-protein interaction domains situated between the EF hands and the antibiotic biosynthesis monooxygenase domain. This review summarizes what is known about genomic organization, tissue expression, intracellular localization, interaction partners, and the physiological and pathophysiological role of the NECAB family.

NECAB1-3, parvalbumin, calbindin, and calretinin in the hippocampus of the European mole

Many calcium-binding proteins are expressed in a region-and cell-type specific manner in the mammalian hippocampus. Neuronal calcium-binding proteins (NECABs) are also expressed in hippocampal neurons, but few species have been investigated, with partly controversial findings. We here describe NECAB1, NECAB2 and NECAB3 as well as parvalbumin, calbindin, and calretinin in the European mole, and compare staining patterns of these proteins with those in mouse and other species. While subtle differences are present, NECAB staining in the European mole was generally similar to those in mouse. Common to European moles, mice, and other species we investigated, large hilar polymorphic cells, likely to represent mossy cells, were positive for all three NECABs. NECAB1 and 2 are suitable as markers for these cells along the entire septotemporal axis of the hippocampus. In the European mole, parvalbumin, calbindin and calretinin showed traits that have been described in other species before, albeit in a unique combination. In summary, we provide the first description of distribution of these proteins in the hippocampus of the European mole. This subterranean, insectivorous, and solitary living species belongs to the Order of Eulipotyphla. Despite many similarities with other subterranean species from the rodent order in terms of lifestyle, its hippocampus is cytoarchitecturally much more elaborated than in, e.g., mole-rats. It remains an open question if the hippocampal structure of the European mole reflects evolutionary constraints or ecology. Our descriptive study highlights the diversity in hippocampal cytoarchitecture even in small mammalian species.

Scaling of smaller pyramidal neuron size and lower energy production in schizophrenia

BACKGROUND

Dorsolateral prefrontal cortex (DLPFC) dysfunction in schizophrenia appears to reflect alterations in layer 3 pyramidal neurons (L3PNs), including smaller cell bodies and lower expression of mitochondrial energy production genes. However, prior somal size studies used biased strategies for identifying L3PNs, and somal size and levels of energy production markers have not been assessed in individual L3PNs.

STUDY DESIGN

We combined fluorescent in situ hybridization (FISH) of vesicular glutamate transporter 1 (VGLUT1) mRNA and immunohistochemical-labeling of NeuN to determine if the cytoplasmic distribution of VGLUT1 mRNA permits the unbiased identification and somal size quantification of L3PNs. Dual-label FISH for VGLUT1 mRNA and cytochrome C oxidase subunit 4I1 (COX4I1) mRNA, a marker of energy production, was used to assess somal size and COX4I1 transcript levels in individual DLPFC L3PNs from schizophrenia (12 males; 2 females) and unaffected comparison (13 males; 1 female) subjects.

STUDY RESULTS

Measures of L3PN somal size with NeuN immunohistochemistry or VGLUT1 mRNA provided nearly identical results (ICC = 0.96, p < 0.0001). Mean somal size of VGLUT1-identified L3PNs was 8.7% smaller (p = 0.004) and mean COX4I1 mRNA levels per L3PN were 16.7% lower (p = 0.01) in schizophrenia. These measures were correlated across individual L3PNs in both subject groups (rrm = 0.81-0.86).

CONCLUSIONS

This preliminary study presents a novel method for combining unbiased neuronal identification with quantitative assessments of somal size and mRNA levels. We replicated findings of smaller somal size and lower COX4I1 mRNA levels in DLPFC L3PNs in schizophrenia. The normal scaling of COX4I1 mRNA levels with somal size in schizophrenia suggests that lower markers of energy production are secondary to L3PN morphological alterations in the illness.

Identification of hub genes and construction of diagnostic nomogram model in schizophrenia

Schizophrenia (SCZ), which is characterized by debilitating neuropsychiatric disorders with significant cognitive impairment, remains an etiological and therapeutic challenge. Using transcriptomic profile analysis, disease-related biomarkers linked with SCZ have been identified, and clinical outcomes can also be predicted. This study aimed to discover diagnostic hub genes and investigate their possible involvement in SCZ immunopathology. The Gene Expression Omnibus (GEO) database was utilized to get SCZ Gene expression data. Differentially expressed genes (DEGs) were identified and enriched by Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and disease ontology (DO) analysis. The related gene modules were then examined using integrated weighted gene co-expression network analysis. Single-sample gene set enrichment (GSEA) was exploited to detect immune infiltration. SVM-REF, random forest, and least absolute shrinkage and selection operator (LASSO) algorithms were used to identify hub genes. A diagnostic model of nomogram was constructed for SCZ prediction based on the hub genes. The clinical utility of nomogram prediction was evaluated, and the diagnostic utility of hub genes was validated. mRNA levels of the candidate genes in SCZ rat model were determined. Finally, 24 DEGs were discovered, the majority of which were enriched in biological pathways and activities. Four hub genes (NEUROD6, NMU, PVALB, and NECAB1) were identified. A difference in immune infiltration was identified between SCZ and normal groups, and immune cells were shown to potentially interact with hub genes. The hub gene model for the two datasets was verified, showing good discrimination of the nomogram. Calibration curves demonstrated valid concordance between predicted and practical probabilities, and the nomogram was verified to be clinically useful. According to our research, NEUROD6, NMU, PVALB, and NECAB1 are prospective biomarkers in SCZ and that a reliable nomogram based on hub genes could be helpful for SCZ risk prediction.

Preliminary findings suggest the number and volume of supragranular and infragranular pyramidal neurons are similar in the anterior superior temporal area of control subjects and subjects with autism

We investigated the cytoarchitecture of the anterior superior temporal area (TA2) of the postmortem cerebral cortex in 9 subjects with autism and 9 age-matched typically developing subjects between the ages of 13 and 56 years. The superior temporal gyrus is involved in auditory processing and social cognition and its pathology has been correlated with autism. We quantified the number and soma volume of pyramidal neurons in the supragranular layers and pyramidal neurons in the infragranular layers in each subject. We did not find significant differences in the number or volume of supragranular or infragranular neurons in the cerebral cortex of subjects with autism compared to typically developing subjects. This report does not support an alteration of supragranular to infragranular neurons in autism. However, further stereological analysis of the number of cells and cell volumes in specific cortical areas is needed to better establish the cellular phenotype of the autistic cerebral cortex and to understand its clinical relevance in autism.

Prefrontal cortical dendritic spine pathology in schizophrenia and bipolar disorder

IMPORTANCE

Prior studies have demonstrated reduced dendritic spine density in the dorsolateral prefrontal cortex (DLPFC) in schizophrenia. However, it remains unclear how generalizable this finding is in schizophrenia and if it is seen in bipolar disorder, a historically distinct psychiatric condition.

OBJECTIVE

To assess whether spine loss is present in the DLPFC of individuals with schizophrenia and individuals with bipolar disorder.

DESIGN, SETTING, AND PARTICIPANTS

This study used postmortem human brain tissue from individuals with schizophrenia (n=14), individuals with bipolar disorder (n=9), and unaffected control participants (n=19). Tissue samples containing the DLPFC (Brodmann area 46) were Golgi-stained, and basilar dendrites of pyramidal cells in the deep half of layer III were reconstructed.

MAIN OUTCOMES AND MEASURES

The number of spines per dendrite, spine density, and dendrite length were compared across groups. We also assessed for the potential effects of clinical and demographic variables on dendritic parameters.

RESULTS

The mean (SD) spine density was significantly reduced (ie, by 10.5%) in individuals with bipolar disorder (0.28 [0.04] spines/μm) compared with control participants (0.31 [0.05] spines/μm) (P=.02). In individuals with schizophrenia, the mean (SD) spine density was also reduced (by 6.5%; 0.29 [0.03] spines/μm) but just missed significance when compared with control participants (P=.06). There was a significant reduction in the mean (SD) number of spines per dendrite in both individuals with schizophrenia (72.8 [24.9] spines per dendrite) and individuals with bipolar disorder (68.9 [12.9] spines per dendrite) compared with controls (92.8 [31.1] spines per dendrite) (individuals with schizophrenia vs controls: 21.6% reduction [P=.003]; individuals with bipolar disorder vs controls: 25.8% reduction [P=.005]). In addition, both individuals with schizophrenia and individuals with bipolar disorder had a reduced mean (SD) dendrite length (246.5 [67.4] and 245.6 [29.8] μm, respectively) compared with controls (301.8 [75.1] μm) (individuals with schizophrenia vs controls: 18.3% reduction [P=.005]; individuals with bipolar disorder vs controls: 18.6% reduction [P=.005]).

CONCLUSIONS AND RELEVANCE

Dendritic spine loss in the DLPFC was seen in both individuals with schizophrenia and individuals with bipolar disorder, suggesting that the 2 disorders may share some common pathophysiological features.

The glutamate hypothesis of schizophrenia: evidence from human brain tissue studies

A number of studies have indicated that antagonists of the N-methyl-d-aspartate subtypes of glutamate receptors can cause schizophrenia-like symptoms in healthy individuals and exacerbate symptoms in individuals with schizophrenia. These findings have led to the glutamate hypothesis of schizophrenia. Here we review the evidence for this hypothesis in postmortem studies of brain tissue from individuals affected by schizophrenia, summarizing studies of glutamate neuron morphology, of expression of glutamate receptors and transporters, and of the synthesizing and metabolizing enzymes for glutamate and its co-agonists. We found consistent evidence of morphological alterations of dendrites of glutamatergic neurons in the cerebral cortex of subjects with schizophrenia and of reduced levels of the axon bouton marker synaptophysin. There were no consistent alterations of mRNA expression of glutamate receptors, although there has been limited study of the corresponding proteins. Studies of the glutamate metabolic pathway have been limited, although there is some evidence that excitatory amino acid transporter-2, glutamine synthetase, and glutaminase have altered expression in schizophrenia. Future studies would benefit from additional direct examination of glutamatergic proteins. Further advances, such as selective testing of synaptic microdomains, cortical layers, and neuronal subtypes, may also be required to elucidate the nature of glutamate signaling impairments in schizophrenia.

Hierarchical temporal processing deficit model of reality distortion and psychoses

We posit in this article that hierarchical temporal processing deficit is the underlying basis of reality distortion and psychoses. Schizophrenia is a prototypical reality distortion disorder in which the patient manifests with auditory hallucinations, delusions, disorganized speech and thinking, cognitive impairment, avolition and social and occupational dysfunction. Reality distortion can be present in many other disorders including bipolar disorder, major depression and even dementia. Conceptually, schizophrenia is a heterogeneous entity likely to be because of numerous causes similar to dementia. Although no single symptom or set of symptoms is pathognomonic, a cardinal feature in all patients with schizophrenia is chronic distortion of reality. The model that we have proposed accounts for the varied manifestations of reality distortion including hallucinations and delusions. In this paper we consider the implications of this model for the underlying biology of psychoses and also for the neurobiology of schizophrenia and suggest potential targets to consider for the etiology and pathophysiology of reality distortion, especially in the context of schizophrenia.

Selective alterations in postsynaptic markers of chandelier cell inputs to cortical pyramidal neurons in subjects with schizophrenia

Markers of GABA neurotransmission between chandelier neurons and their synaptic targets, the axon initial segment (AIS) of pyramidal neurons, are altered in the dorsolateral prefrontal cortex (dlPFC) of subjects with schizophrenia. For example, immunoreactivity for the GABA membrane transporter (GAT1) is decreased in presynaptic chandelier neuron axon terminals, whereas immunoreactivity for the GABA(A) receptor alpha2 subunit is increased in postsynaptic AIS. To understand the nature and functional significance of these alterations, we determined the density, laminar distribution, and length of AIS immunoreactive (IR) for ankryin-G and betaIV spectrin, two proteins involved in the regulation of synapse structure and ion channel clustering at AIS, in dlPFC area 46 from 14 matched triads of subjects with schizophrenia or major depressive disorder (MDD) and normal comparison participants. The density of ankyrin-G-IR AIS in the superficial, but not in the deep, cortical layers was significantly decreased by 15-19% in the subjects with schizophrenia relative to the other participant groups. In contrast, no group differences were present in the density of betaIV spectrin-IR AIS. The length of labeled AIS did not differ across participant groups for either ankyrin-G or betaIV spectrin. The density of ankyrin-G-IR AIS was not altered in the dlPFC of macaque monkeys chronically exposed to antipsychotic medications. Given the important role of ankyrin-G in the recruitment and stabilization of sodium channels and other integral membrane proteins to AIS, our findings suggest that these processes are selectively altered in superficial layer pyramidal neurons in subjects with schizophrenia.

Schizophrenia is a disorder of higher order hierarchical processing

Schizophrenia is a mental disorder in which the patient manifests with auditory hallucinations, paranoid or bizarre delusions, and disorganized speech and thinking. It is associated with significant social dysfunction. There are many hypotheses regarding schizophrenia. Most of these focus on schizophrenia as a manifestation of abnormalities from genetic [Mulle JG. Genomic structural variation and schizophrenia. Curr Psychiatry Rep 2008;10(2):171-7], viral [Fruntes V, Limosin F. Schizophrenia and viral infection during neurodevelopment: a pathogenesis model? Med Sci Monit 2008;14(6):RA71-7], neurochemical [e.g. dopamine (Lewis DA, Akil M. Cortical dopamine in schizophrenia: strategies for postmortem studies. J Psychiatr Res 1997;31(2):175-95) or interactions between neurotransmitters (Duncan GE, Sheitman BB, Lieberman JA. An integrated view of pathophysiological models of schizophrenia. Brain Res Brain Res Rev 1999;29(2):250-64)] or brain structural [Kotrla KJ, Weinberger DR. Brain imaging in schizophrenia. Annu Rev Med 1995;46:113-22] origins. Most of these hypotheses do not account for how or why these presumed causes lead to the manifestations of schizophrenia. We argue that brain structure and function is compatible with a hierarchical processing structure that forms the basis for perception and thought in healthy humans. We propose that perturbations of the types listed above lead to disruption of higher levels of perception and hierarchical temporal processing by the brain and that this constitutes the core deficit in schizophrenia. We present evidence that this model explains many of the features of schizophrenia and we make a series of predictions about schizophrenia.

Neuroplasticity of neocortical circuits in schizophrenia

The core features of schizophrenia include deficits in cognitive processes mediated by the circuitry of the dorsolateral prefrontal cortex (DLPFC). These deficits are associated with a range of molecular and morphological alterations in the DLPFC, each of which could be a cause, consequence, or compensation in relation to other changes, and thus reflect the neuroplasticity of the brain in response to the underlying disease process. In this review, we consider disturbances in excitatory, inhibitory, and modulatory connections of DLPFC circuitry from the perspective of disease- and development-related neuroplasticity and discuss their implications for the identification of novel therapeutic targets.

Transcriptome alterations in schizophrenia: disturbing the functional architecture of the dorsolateral prefrontal cortex

The availability of methods for quantifying tissue concentrations of messenger RNAs in the postmortem of the human brain has provided a number of new findings in schizophrenia. However, understanding how these findings actually relate to the disease process of schizophrenia requires knowledge both of the factors that might give rise to such changes in gene expression and of the impact of these changes on the function of the affected neural circuits. Consequently, this chapter provides a review of the potential causes and consequences of some of the schizophrenia-related transcriptome changes in the dorsolateral prefrontal cortex, a brain region implicated in the pathophysiology of certain core cognitive deficits in this illness.

Evidence of altered neurogranin immunoreactivity in areas 9 and 32 of schizophrenic prefrontal cortex

Schizophrenia is a complex and poorly understood neuropsychiatric disorder. Much research has begun to implicate the prefrontal cortex in the disease. Using immunocytochemistry we determined if neurogranin, a protein found in dendrites, spines and cell bodies and an upstream regulator of calcium was altered in areas 9 and 32 of schizophrenic prefrontal cortex. We examined its expression in pyramidal cells in layers III and V. Tissues from 7 controls and 7 schizophrenics (from our original MAP2 study, Jones, L., Johnson, N., Byne, W., 2002. Alterations in MAP2 staining in area 9 and 32 of schizophrenic prefrontal cortex. Psych. Res. 114, 137-148) matched for age, sex and postmortem interval were examined. Using area fraction analysis we quantified the immunostaining. Additionally, we counted the number of positively stained pyramidal cells in the same 7 pairs. Neurogranin immunostaining was dramatically reduced in both layers III (72%) and V (50%) in area 9. In area 32 there was a more modest reduction in both layers III (36%) and V (40%). There was no difference in either brain region or layer in the density of positively stained pyramidal cells. These data confirm mounting evidence suggesting dendritic loss in the prefrontal cortex and suggest that the loss of protein does not appear to be due to a change in the number of cells producing the protein but rather in the amount of protein being produced. Additionally, these data suggest that the loss of neurogranin may alter the calcium-calmodulin dependent pathways due to its role as a regulator of calmodulin suggesting a link between structural and functional alterations of the pyramidal cells in the prefrontal cortex.