Gene Expression Analysis Implicates a Death Receptor Pathway in Schizophrenia Pathology

An increase in apoptotic events may underlie neuropathology in schizophrenia. By data-mining approaches, we identified significant expression changes in death receptor signaling pathways in the dorsolateral prefrontal cortex (DLPFC) of patients with schizophrenia, particularly implicating the Tumor Necrosis Factor Superfamily member 6 (FAS) receptor and the Tumor Necrosis Factor [ligand] Superfamily member 13 (TNFSF13) in schizophrenia. We sought to confirm and replicate in an independent tissue collection the noted mRNA changes with quantitative real-time RT-PCR. To test for regional and diagnostic specificity, tissue from orbital frontal cortex (OFC) was examined and a bipolar disorder group included. In schizophrenia, we confirmed and replicated significantly increased expression of TNFSF13 mRNA in the DLPFC. Also, a significantly larger proportion of subjects in the schizophrenia group had elevated FAS receptor expression in the DLPFC relative to unaffected controls. These changes were not observed in the bipolar disorder group. In the OFC, there were no significant differences in TNFSF13 or FAS receptor mRNA expression. Decreases in BH3 interacting domain death agonist (BID) mRNA transcript levels were found in the schizophrenia and bipolar disorder groups affecting both the DLPFC and the OFC. We tested if TNFSF13 mRNA expression correlated with neuronal mRNAs in the DLPFC, and found significant negative correlations with interneuron markers, parvalbumin and somatostatin, and a positive correlation with PPP1R9B (spinophilin), but not DLG4 (PSD-95). The expression of TNFSF13 mRNA in DLPFC correlated negatively with tissue pH, but decreasing pH in cultured cells did not cause increased TNFSF13 mRNA nor did exogenous TNFSF13 decrease pH. We concluded that increased TNFSF13 expression may be one of several cell-death cytokine abnormalities that contribute to the observed brain pathology in schizophrenia, and while increased TNFSF13 may be associated with lower brain pH, the change is not necessarily causally related to brain pH

Altered Disrupted-in-Schizophrenia-1 function affects the development of cortical parvalbumin interneurons by an indirect mechanism.

<div><p><i>Disrupted-in-Schizophrenia-1 (DISC1)</i> gene has been linked to schizophrenia and related major mental illness. Mouse Disc1 has been implicated in brain development, mainly in the proliferation, differentiation, lamination, neurite outgrowth and synapse formation and maintenance of cortical excitatory neurons. Here, the effects of two loss-of-function point mutations in the mouse <i>Disc1</i> sequence (Q31L and L100P) on cortical inhibitory interneurons were investigated. None of the mutations affected the overall number of interneurons. However, the 100P, but not the 31L, mutation resulted in a significant decrease in the numbers of interneurons expressing parvalbumin mRNA and protein across the sensory cortex. To investigate role of Disc1 in regulation of parvalbumin expression, mouse wild-type Disc-1 or the 100P mutant form were electroporated <i>in utero</i> into cortical excitatory neurons. Overexpression of wild-type Disc1 in these cells caused increased densities of parvalbumin-expressing interneurons in the electroporated area and in areas connected with it, whereas expression of Disc1-100P did not. We conclude that the 100P mutation prevents expression of parvalbumin by a normally sized cohort of interneurons and that altering Disc1 function in cortical excitatory neurons indirectly affects parvalbumin expression by cortical interneurons, perhaps as a result of altered functional input from the excitatory neurons.</p></div

Molecular evidence of N-methyl-D-aspartate receptor hypofunction in schizophrenia

Blockade of N-methyl-D-aspartate receptors (NMDARs) produces behavior in healthy people that is similar to the psychotic symptoms and cognitive deficits of schizophrenia and can exacerbate symptoms in people with schizophrenia. However, an endogenous brain disruption of NMDARs has not been clearly established in schizophrenia. We measured mRNA transcripts for five NMDAR subunit mRNAs and protein for the NR1 subunit in the dorsolateral prefrontal cortex (DLPFC) of schizophrenia and control (n = 74) brains. Five NMDAR single-nucleotide polymorphisms (SNPs) previously associated with schizophrenia were tested for association with NMDAR mRNAs in postmortem brain and for association with cognitive ability in an antemortem cohort of 101 healthy controls and 48 people with schizophrenia. The NR1 subunit (mRNA and protein) and NR2C mRNA were decreased in postmortem brain from people with schizophrenia (P = 0.004, P = 0.01 and P = 0.01, respectively). In the antemortem cohort, the minor allele of NR2B rs1805502 (T5988C) was associated with significantly lower reasoning ability in schizophrenia. In the postmortem brain, the NR2B rs1805502 (T5988C) C allele was associated with reduced expression of NR1 mRNA and protein in schizophrenia. Reduction in NR1 and NR2C in the DLPFC of people with schizophrenia may lead to altered NMDAR stoichiometry and provides compelling evidence for an endogenous NMDAR deficit in schizophrenia. Genetic variation in the NR2B gene predicts reduced levels of the obligatory NR1 subunit, suggesting a novel mechanism by which the NR2B SNP may negatively influence other NMDAR subunit expression and reasoning ability in schizophrenia

Cognitive symptoms facilitatory for diagnoses in neuropsychiatric disorders: Executive functions and locus of control

Cognitive symptoms, considered in conjunction both with their regional brain and biomarkers as well as affective, attributional and neurode-velopmental components, demonstate ever-increasing complexity to facilitate conceptualization yet, unavoidably, bedevil diagnosis in neuropsychiatry even before considerations of the enigmatic processes in memory, such as executive function and working memory, are drawn into the myriads of equations that await remedial interpretations. Prefrontal and limbic regions of the brain are involved in a diversity of expressions of cognition, normal or dysfunctional, at synaptic, intracellular and molecular levels that mobilize a concatenation of signaling entities. Serotoninergic neurotransission at prefrontal regions directs cogntive-affective entities that mediate decision-making and goal-directed behaviour. Clinical, non-clinical and basic studies challenge attempts to consolidate the multitude of evidence in order to obtain therapeutic notions to alleviate the disordered status of the diagnosed and yet-to-be diagnosed individuals. Locus of control, a concept of some utility in health-seeking procedures, is examined in three self-report studies from the perspective of a cognitive-emotional situation through observations of ordinary, \u27healthy\u27 young and middle-aged individuals, to assess the predictors of internal and external locus of control. A notion based on high level executive functioning in the dorsolateral prefrontal cortex (DLPFC) in individuals characterised by internal locus of control is contrasted with a hypofunctional executive DLPFC, characterising individuals that express an external locus of control, is discussed