Association of DISC1, BDNF, and COMT polymorphisms with exploratory eye movement of schizophrenia in a Chinese Han population

Interactions Among Brain-Derived Neurotrophic Factor and Neuroimmune Pathways Are Key Components of the Major Psychiatric Disorders

The purpose of this review is to summarize the current knowledge regarding the reciprocal associations between brain-derived neurotrophic factor (BDNF) and immune-inflammatory pathways and how these links may explain the involvement of this neurotrophin in the immune pathophysiology of mood disorders and schizophrenia. Toward this end, we delineated the protein-protein interaction (PPI) network centered around BDNF and searched PubMed, Scopus, Google Scholar, and Science Direct for papers dealing with the involvement of BDNF in the major psychosis, neurodevelopment, neuronal functions, and immune-inflammatory and related pathways. The PPI network was built based on the significant interactions of BDNF with neurotrophic (NTRK2, NTF4, and NGFR), immune (cytokines, STAT3, TRAF6), and cell-cell junction (CTNNB, CDH1) DEPs (differentially expressed proteins). Enrichment analysis shows that the most significant terms associated with this PPI network are the tyrosine kinase receptor (TRKR) and Src homology region two domain-containing phosphatase-2 (SHP2) pathways, tyrosine kinase receptor signaling pathways, positive regulation of kinase and transferase activity, cytokine signaling, and negative regulation of the immune response. The participation of BDNF in the immune response and its interactions with neuroprotective and cell-cell adhesion DEPs is probably a conserved regulatory process which protects against the many detrimental effects of immune activation and hyperinflammation including neurotoxicity. Lowered BDNF levels in mood disorders and schizophrenia (a) are associated with disruptions in neurotrophic signaling and activated immune-inflammatory pathways leading to neurotoxicity and (b) may interact with the reduced expression of other DEPs (CTNNB1, CDH1, or DISC1) leading to multiple aberrations in synapse and axonal functions.

Genetic Advance in Depressive Disorder

Major depressive disorder (MDD) and bipolar disorder (BPD) are both chronic, severe mood disorder with high misdiagnosis rate, leading to substantial health and economic burdens to patients around the world. There is a high misdiagnosis rate of bipolar depression (BD) just based on symptomology in depressed patients whose previous manic or mixed episodes have not been well recognized. Therefore, it is important for psychiatrists to identify these two major psychiatric disorders. Recently, with the accumulation of clinical sample sizes and the advances of methodology and technology, certain progress in the genetics of major depression and bipolar disorder has been made. This article reviews the candidate genes for MDD and BD, genetic variation loci, chromosome structural variation, new technologies, and new methods.

Targeting mGlu Receptors for Optimization of Antipsychotic Activity and Disease-Modifying Effect in Schizophrenia

Metabotropic glutamate (mGlu) receptors are considered as candidate drug targets for the treatment of schizophrenia. These receptors form a family of eight subtypes (mGlu1 to -8), of which mGlu1 and -5 are coupled to G_q/11, and all other subtypes are coupled to G_i/o. Here, we discuss the possibility that selective ligands of individual mGlu receptor subtypes may be effective in controlling the core symptoms of schizophrenia, and, in some cases, may impact mechanisms underlying the progression of the disorder. Recent evidence indicates that activation of mGlu1 receptors inhibits dopamine release in the meso-striatal system. Hence, selective positive allosteric modulators (PAMs) of mGlu1 receptors hold promise for the treatment of positive symptoms of schizophrenia. mGlu5 receptors are widely expressed in the CNS and regulate the activity of cells that are involved in the pathophysiology of schizophrenia, such as cortical GABAergic interneurons and microglial cells. mGlu5 receptor PAMs are under development for the treatment of schizophrenia and cater the potential to act as disease modifiers by restraining neuroinflammation. mGlu2 receptors have attracted considerable interest because they negatively modulate 5-HT_2A serotonin receptor signaling in the cerebral cortex. Both mGlu2 receptor PAMs and orthosteric mGlu2/3 receptor agonists display antipsychotic-like activity in animal models, and the latter drugs are inactive in mice lacking mGlu2 receptors. So far, mGlu3 receptors have been left apart as drug targets for schizophrenia. However, activation of mGlu3 receptors boosts mGlu5 receptor signaling, supports neuronal survival, and drives microglial cells toward an antiinflammatory phenotype. This strongly encourages research of mGlu3 receptors in schizophrenia. Finally, preclical studies suggest that mGlu4 receptors might be targeted by novel antipsychotic drugs, whereas studies of mGlu7 and mGlu8 receptors in animal models of psychosis are still at their infancy.

Gene polymorphisms of DISC1 is associated with schizophrenia: Evidence from a meta-analysis

BACKGROUND

Previous studies suggest an association between Disrupted in schizophrenia 1 (DISC1) polymorphisms and schizophrenia (SCZ). However, the available data are often inconsistent, regarding the difference in sample size, ethnicity, genotyping method, etc. Thus, we carried out a meta-analysis to determine whether DISC1 polymorphisms contributed susceptibility to SCZ.

METHODS

A methodical literature review was operated using the English and Chinese core electronic databases. Odds ratios (ORs) with 95% confidence intervals (CIs) were applied to determine the correlation between DISC1 gene polymorphisms and SCZ susceptibility. Subgroup analyses were carried out by stratification of ethnicity. P values were Bonferroni adjusted to account for multiple testing. Publication bias was evaluated by funnel plots, Egger's test and the trim and fill method.

RESULTS

Meta-analyses results suggested that DISC1 polymorphisms (rs821616 and rs821597) increased SCZ risk in overall populations. In subgroups of ethnicity, DISC1 polymorphisms (rs821616 and rs821597) was associated with susceptibility to SCZ among the Chinese population (for rs821616: TT+AT vs. AA: OR=1.338, 95% CI=1.124-1.592, P=0.001; T vs. A: OR=1.300, 95% CI=1.124-1.504, P<0.000; for rs821597: AA+AG vs. GG: OR=1.508, 95% CI=1.268-1.794, P<0.001; A vs. G: OR=1.345, 95% CI=1.184-1.527, P<0.001). A positive correlation was also observed between the single marker rs821616 and SCZ among the Japanese population in the recessive model (TT vs. AT+AA: OR=1.524, 95% CI=1.185-1.959, P=0.001). There was no significant relationship between other DISC1 polymorphisms (rs3738401, rs2273890, rs3738398, rs3738402, rs2492367, rs843979, rs3737597, rs4658971, rs1538979, rs1000731 and rs3738399) and SCZ.

CONCLUSIONS

DISC1 polymorphisms increased a risk of SCZ, especially in the Chinese population. In order to further corroborate our findings, large well-designed epidemiological studies are needed.