The NCAN gene: schizophrenia susceptibility and cognitive dysfunction

Astrocyte-secreted neurocan controls inhibitory synapse formation and function

Astrocytes strongly promote the formation and maturation of synapses by secreted proteins. Several astrocyte-secreted synaptogenic proteins controlling excitatory synapse development were identified; however, those that induce inhibitory synaptogenesis remain elusive. Here, we identify neurocan as an astrocyte-secreted inhibitory synaptogenic protein. After secretion from astrocytes, neurocan is cleaved into N- and C-terminal fragments. We found that these fragments have distinct localizations in the extracellular matrix. The neurocan C-terminal fragment localizes to synapses and controls cortical inhibitory synapse formation and function. Neurocan knockout mice lacking the whole protein or only its C-terminal synaptogenic domain have reduced inhibitory synapse numbers and function. Through super-resolution microscopy, in vivo proximity labeling by secreted TurboID, and astrocyte-specific rescue approaches, we discovered that the synaptogenic domain of neurocan localizes to somatostatin-positive inhibitory synapses and strongly regulates their formation. Together, our results unveil a mechanism through which astrocytes control circuit-specific inhibitory synapse development in the mammalian brain.

Astrocyte-Secreted Neurocan Controls Inhibitory Synapse Formation and Function

Astrocytes strongly promote the formation and maturation of synapses by secreted proteins. To date, several astrocyte-secreted synaptogenic proteins controlling different stages of excitatory synapse development have been identified. However, the identities of astrocytic signals that induce inhibitory synapse formation remain elusive. Here, through a combination of in vitro and in vivo experiments, we identified Neurocan as an astrocyte-secreted inhibitory synaptogenic protein. Neurocan is a chondroitin sulfate proteoglycan that is best known as a protein localized to the perineuronal nets. However, Neurocan is cleaved into two after secretion from astrocytes. We found that the resulting N- and C-terminal fragments have distinct localizations in the extracellular matrix. While the N-terminal fragment remains associated with perineuronal nets, the Neurocan C-terminal fragment localizes to synapses and specifically controls cortical inhibitory synapse formation and function. Neurocan knockout mice lacking the whole protein or only its C-terminal synaptogenic region have reduced inhibitory synapse numbers and function. Through super-resolution microscopy and in vivo proximity labeling by secreted TurboID, we discovered that the synaptogenic domain of Neurocan localizes to somatostatin-positive inhibitory synapses and strongly regulates their formation. Together, our results unveil a mechanism through which astrocytes control circuit-specific inhibitory synapse development in the mammalian brain.

NLRP3 Influences Cognitive Function in Schizophrenia in Han Chinese

It has been proposed that immune abnormalities may be implicated with pathophysiology of schizophrenia. The nod-like receptor pyrin domain-contraining protein 3 (NLRP3) can trigger immune-inflammatory cascade reactions. In this study, we intended to identify the role of gene encoding NLRP3 (NLRP3) in susceptibility to schizophrenia and its clinical features. For the NLRP3 mRNA expression analysis, 53 drug-naïve patients with first-episode schizophrenia and 56 healthy controls were enrolled. For the genetic study, a total of 823 schizophrenia patients and 859 controls were recruited. Among them, 239 drug-naïve patients with first-episode schizophrenia were enrolled for clinical evaluation. There is no significant difference in NLRP3 mRNA levels between patients with schizophrenia and healthy controls (p = 0.07). We did not observe any significant differences in allele and genotype frequencies of rs10754558 polymorphism between the schizophrenia and control groups. We noticed significant differences in the scores of RBANS attention and total scores between the patients with different genotypes of rs10754558 polymorphism (p = 0.001 and p < 0.01, respectively). Further eQTL analysis presented a significant association between the rs10754558 polymorphism and NLRP3 in frontal cortex (p = 0.0028, p = 0.028 after Bonferroni correction). Although our findings did not support NLRP3 confer susceptibility to schizophrenia, NLRP3 may be a risk factor for cognitive impairment, especially attention deficit in this disorder.

A systematic review and meta-analysis of imaging genetics studies of specific reading disorder

The imaging genetics of specific reading disabilities (SRD) is an emerging field that aims to characterize the disabilities' neurobiological causes, including atypical brain structure and function and distinct genetic architecture. The present review aimed to summarize current imaging genetics studies of SRD, characterize the effect sizes of reported results by calculating Cohen's d, complete a Fisher's Combined Probability Test for genes featured in multiple studies, and determine areas for future research. Results demonstrate associations between SRD risk genes and reading network brain phenotypes. The Fisher's test revealed promising results for the genes DCDC2, KIAA0319, FOXP2, SLC2A3, and ROBO1. Future research should focus on exploratory approaches to identify previously undiscovered genes. Using comprehensive neuroimaging (e.g., functional and effective connectivity) and genetic (e.g., sequencing and epigenetic) techniques, and using larger samples, diverse stages of development, and longitudinal investigations, would help researchers understand the neurobiological correlates of SRD to improve early identification.

Molecular signature of extracellular matrix pathology in schizophrenia

Growing evidence points to a critical involvement of the extracellular matrix (ECM) in the pathophysiology of schizophrenia (SZ). Decreases of perineuronal nets (PNNs) and altered expression of chondroitin sulphate proteoglycans (CSPGs) in glial cells have been identified in several brain regions. GWAS data have identified several SZ vulnerability variants of genes encoding for ECM molecules. Given the potential relevance of ECM functions to the pathophysiology of this disorder, it is necessary to understand the extent of ECM changes across brain regions, their region- and sex-specificity and which ECM components contribute to these changes. We tested the hypothesis that the expression of genes encoding for ECM molecules may be broadly disrupted in SZ across several cortical and subcortical brain regions and include key ECM components as well as factors such as ECM posttranslational modifications and regulator factors. Gene expression profiling of 14 neocortical brain regions, caudate, putamen and hippocampus from control subjects (n = 14/region) and subjects with SZ (n = 16/region) was conducted using Affymetrix microarray analysis. Analysis across brain regions revealed widespread dysregulation of ECM gene expression in cortical and subcortical brain regions in SZ, impacting several ECM functional key components. SRGN, CD44, ADAMTS1, ADAM10, BCAN, NCAN and SEMA4G showed some of the most robust changes. Region-, sex- and age-specific gene expression patterns and correlation with cognitive scores were also detected. Taken together, these findings contribute to emerging evidence for large-scale ECM dysregulation in SZ and point to molecular pathways involved in PNN decreases, glial cell dysfunction and cognitive impairment in SZ.

ADAMTS-12: Functions and Challenges for a Complex Metalloprotease

Nineteen members of the ADAMTS family of secreted zinc metalloproteinases are present in the human degradome. A wide range of different functions are being attributed to these enzymes and the number of their known substrates is considerably increasing in recent years. ADAMTSs can participate in processes such as fertility, inflammation, arthritis, neuronal and behavioral disorders, as well as cancer. Since its first annotation in 2001, ADAMTS-12 has been described to participate in different processes displayed by members of this family of proteinases. In this sense, ADAMTS-12 performs essential roles in modulation and recovery from inflammatory processes such as colitis, endotoxic sepsis and pancreatitis. ADAMTS-12 has also been involved in cancer development acting either as a tumor suppressor or as a pro-tumoral agent. Furthermore, participation of ADAMTS-12 in arthritis or in neuronal disorders has also been suggested through degradation of components of the extracellular matrix. In addition, ADAMTS-12 proteinase activity can also be modified by interaction with other proteins and thus, can be an alternative way of modulating ADAMTS-12 functions. In this review we revised the most relevant findings about ADAMTS-12 function on the 20th anniversary of its identification.

Hyalectanase Activities by the ADAMTS Metalloproteases

The hyalectan family is composed of the proteoglycans aggrecan, versican, brevican and neurocan. Hyalectans, also known as lecticans, are components of the extracellular matrix of different tissues and play essential roles in key biological processes including skeletal development, and they are related to the correct maintenance of the vascular and central nervous system. For instance, hyalectans participate in the organization of structures such as perineural nets and in the regulation of neurite outgrowth or brain recovery following a traumatic injury. The ADAMTS (A Disintegrin and Metalloprotease domains, with thrombospondin motifs) family consists of 19 secreted metalloproteases. These enzymes also perform important roles in the structural organization and function of the extracellular matrix through interactions with other matrix components or as a consequence of their catalytic activity. In this regard, some of their preferred substrates are the hyalectans. In fact, ADAMTSs cleave hyalectans not only as a mechanism for clearance or turnover of proteoglycans but also to generate bioactive fragments which display specific functions. In this article we review some of the physiological and pathological effects derived from cleavages of hyalectans mediated by ADAMTSs.

Association of Cognitive Impairment With Anhedonia in Patients With Schizophrenia

Anhedonia is considered as one of the five dimensions of negative symptoms and mainly refers to the reduction of the capacity of feeling pleasure. Increasing evidence suggests that anhedonia in schizophrenia may be partly explained by cognitive impairment. However, the associations between specific cognitive impairment and anhedonia are not fully investigated. The purpose of this study was to examine anticipatory anhedonia, consummatory anhedonia, and their cognitive associations in schizophrenia. A total number of 100 patients with schizophrenia and 67 healthy volunteers were recruited. The clinical symptoms of schizophrenia were assessed. Anticipatory pleasure, consummatory pleasure, and cognitive functions of each participant were measured. Multiple linear regression analysis was performed to investigate the influencing factors of anhedonia in schizophrenia. The results showed no significant differences in sex, age, education year, body mass index (BMI), and marital status between the schizophrenia group and healthy control group (all P > 0.05). Both anticipatory and consummatory pleasure in the schizophrenia group were significantly lower than those in the healthy control group (all P < 0.05). Immediate memory, visual spanning, language, attention, and delayed memory were significantly poorer in the schizophrenia group (all P < 0.05). The results showed that language deficit is an independent risk factor for anticipatory anhedonia (B' = 0.265, P = 0.008, 95% CI: 0.038-0.244), while delayed memory deficit is an independent risk factor for consummatory anhedonia (B' = 0.391, P < 0.001, 95% CI:0.085-0.237). To the best of our knowledge, this is the first study that reported the specific cognitive associations of anhedonia in schizophrenia. The findings have added new evidence on the influencing factors of anhedonia and provided clues for the associations between clinical manifestations of schizophrenia.

Aberrant glycosylation in schizophrenia: a review of 25 years of post-mortem brain studies

Glycosylation, the enzymatic attachment of carbohydrates to proteins and lipids, regulates nearly all cellular processes and is critical in the development and function of the nervous system. Axon pathfinding, neurite outgrowth, synaptogenesis, neurotransmission, and many other neuronal processes are regulated by glycans. Over the past 25 years, studies analyzing post-mortem brain samples have found evidence of aberrant glycosylation in individuals with schizophrenia. Proteins involved in both excitatory and inhibitory neurotransmission display altered glycans in the disease state, including AMPA and kainate receptor subunits, glutamate transporters EAAT1 and EAAT2, and the GABA_A receptor. Polysialylated NCAM (PSA-NCAM) and perineuronal nets, highly glycosylated molecules critical for axonal migration and synaptic stabilization, are both downregulated in multiple brain regions of individuals with schizophrenia. In addition, enzymes spanning several pathways of glycan synthesis show differential expression in brains of individuals with schizophrenia. These changes may be due to genetic predisposition, environmental perturbations, medication use, or a combination of these factors. However, the recent association of several enzymes of glycosylation with schizophrenia by genome-wide association studies underscores the importance of glycosylation in this disease. Understanding how glycosylation is dysregulated in the brain will further our understanding of how this pathway contributes to the development and pathophysiology of schizophrenia.

Genetic impact of ZNF804A on cognitive function in patients with bipolar I disorder

Our previous genetic study identified a variant rs1344706 in the zinc finger protein 804A (ZNF804A) gene conferring susceptibility to bipolar disorder subtype I (BD-I) in Han Chinese. Literature documented that this variant may affect brain structure and function. As such, we attempted to identify whether the rs1344706 polymorphism influences cognitive function in patients with bipolar disorder I. We recruited 177 patients with bipolar disorder in remission period. Cognitive function was evaluated using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). The single nucleotide polymorphisms (SNP) rs1344706 was genotyped using TaqMan assays. Analysis of covariance (ANCOVA) analysis showed a significant genotypic effect on RBANS immediate memory (P = 0.002) and total score (P = 0.001). Post hoc analysis showed that the patients with T/T genotype have lower RBANS immediate memory and total scores than those with T/G or G/G genotypes. When the patients were stratified by sex, such significances are only seen in male patients, but not female patients. Our findings suggested a sex-specific effect of ZNF804A rs1344706 polymorphism on cognitive function in patients with bipolar disorder-I.

Interactions of Antibodies to the Gram-Negative Gastric Bacterium Helicobacter pylori with the Synaptic Calcium Sensor Synaptotagmin 5, Correlate to Impaired Vesicle Recycling in SiMa Human Neuroblastoma Cells

Due to molecular mimicry, maternal antibacterial antibodies are suspected to promote neurodevelopmental changes in the offspring that finally can cause disorders like autism and schizophrenia. Using a human first trimester prenatal brain multiprotein array (MPA), we demonstrate here that antibodies to the digestive tract bacteria Helicobacter pylori (α-HPy) and Campylobacter jejuni (α-CJe) interact with different synaptic proteins, including the calcium sensor synaptotagmin 5 (Syt5). Interactions of both antisera with Syt5 were confirmed by Western blot with a HEK293-cells overexpression lysate of this protein. Immunofluorescence and Western blotting revealed SiMa cells to express Syt5, which also co-migrated with a band/spot labeled by either α-HPy or α-CJe. Functionally, a 12-h pretreatment of SiMa cells with 10 μg/ml of either α-HPy or α-CJe resulted in a significant reduction of acetylcholine(ACh)-dependent calcium signals as compared to controls. Also ACh-dependent vesicle recycling was significantly reduced in cells pretreated with either α-HPy or α-CJe. Similar effects were observed upon pretreatment of SiMa cells with Syt5-specific antibodies. In conclusion, the present study supports the view that prenatal maternal antibacterial immune responses towards HPy and by this to Syt5 are able to cause functional changes, which in the end might contribute also to neurodevelopmental disorders.

Omega-3 fatty acids ameliorate cognitive dysfunction in schizophrenia patients with metabolic syndrome

Our previous study showed that metabolic abnormalities reduced the levels of brain-derived neurotrophic factor (BDNF) and deteriorated cognitive performance in patients with schizophrenia. Inflammation may play a key role in this process. Omega-3 fatty acids have been documented to ameliorate inflammation. Therefore, we hypothesized that omega-3 fatty acids may be of value in enhancing BDNF levels and improving cognitive function in patients with schizophrenia with metabolic syndrome (MetS). We recruited 80 patients with both schizophrenia and MetS who received long-term olanzapine monotherapy. The enzyme-linked immunosorbent assay was used to measure the plasma levels of C-reactive protein (CRP), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α). The patients were randomly assigned to the OMG-3 group (n = 40) or the placebo group (n = 40). Of the 80 patients who consented to the study, 72 completed this 12-week RCT. The primary outcome was the changes from baseline to 12 weeks in clinical characteristics and the levels of BDNF, CRP, IL-6 and TNF-α. There was a significant correlation between omega-3 fatty acid treatment and enhanced delayed memory factor in the RBANS assessment (F_group×time = 6.82; df = 1, 66; P = 0.01) when the patients completed this study. Along with cognitive improvement, omega-3 fatty acids enhanced BDNF (F_group×time = 4.93; df = 1, 66; P = 0.03) and reduced CRP (F_group×time = 17.11; df = 1, 66; P < 0.01), IL-6 (F_group×time = 9.71; df = 1, 66; P < 0.004) and TNF-α (F_group×time = 6.71; df = 1, 66; P = 0.012) levels after 12 weeks of treatment. The changes in BDNF levels are negatively correlated with the changes in TNF-α levels (r = -0.37, P = 0.03) but not with the changes in CRP and IL-6 levels. Our findings provide suggestive evidence that omega-3 fatty acids have beneficial effects on cognitive function in patients with MetS, which is paralleled by enhanced BDNF levels.

A Comprehensive Analysis of the Effect of SIRT1 Variation on the Risk of Schizophrenia and Depressive Symptoms

Depressive symptoms could be considered a mutual manifestation of major depressive disorder and schizophrenia. Rs3758391 is a functional locus of Sirtuin (SIRT1) involving depression etiology. In this study, we hypothesized that the SIRT1 SNP rs3758391 might be a hazard for schizophrenia pathogenesis, especially related to the appearance of depressive symptoms. We recruited 723 healthy controls and 715 schizophrenia patients, the occurrence of psychotic and depressive symptoms was evaluated by Calgary Depression Scale (CDSS) and PANSS. Meanwhile, qt-PCR was used to detect the mRNA levels of SIRT1 in peripheral blood of 197 olanzapine monotherapy schizophrenia patients. 45.6% of schizophrenia patients had depressive symptoms. In the patient group, mRNA levels of patients with depressive symptoms were significantly lower than those without depressive symptoms (P < 0.01). CDSS scores of schizophrenia patients with different rs3758391 genotypes were significantly different (P < 0.01). Post hoc comparisons indicated that the CDSS scores of rs3758391 C/C and C/T carriers were higher than those of T/T carriers (Ps < 0.01). In the occipital cortex, our eQTL analysis showed that there was a clear correlation between rs3758391 and the SIRT1 mRNA levels. Our preliminary findings provide suggestive evidence that SIRT1 makes schizophrenia patients more prone to depressive symptoms. This SNP might be a biomarker of depression in schizophrenia.

Neurocan genome-wide psychiatric risk variant affects explicit memory performance and hippocampal function in healthy humans

Alterations of the brain extracellular matrix (ECM) can perturb the structure and function of brain networks like the hippocampus, a key region in human memory that is commonly affected in psychiatric disorders. Here, we investigated the potential effects of a genome-wide psychiatric risk variant in the NCAN gene encoding the ECM proteoglycan neurocan (rs1064395) on memory performance, hippocampal function and cortical morphology in young, healthy volunteers. We assessed verbal memory performance in two cohorts (N = 572, 302) and found reduced recall performance in risk allele (A) carriers across both cohorts. In 117 participants, we performed functional magnetic resonance imaging using a novelty-encoding task with visual scenes. Risk allele carriers showed higher false alarm rates during recognition, accompanied by inefficiently increased left hippocampal activation. To assess effects of rs1064395 on brain morphology, we performed voxel-based morphometry in 420 participants from four independent cohorts and found lower grey matter density in the ventrolateral and rostral prefrontal cortex of risk allele carriers. In silico eQTL analysis revealed that rs1064395 SNP is linked not only to increased prefrontal expression of the NCAN gene itself, but also of the neighbouring HAPLN4 gene, suggesting a more complex effect of the SNP on ECM composition. Our results suggest that the NCAN rs1064395 A allele is associated with lower hippocampus-dependent memory function, variation of prefrontal cortex structure and ECM composition. Considering the well-documented hippocampal and prefrontal dysfunction in bipolar disorder and schizophrenia, our results may reflect an intermediate phenotype by which NCAN rs1064395 contributes to disease risk.

Homocysteine, but not MTHFR gene polymorphism, influences depressive symptoms in patients with schizophrenia

BACKGROUND

Methylenetetrahydrofolate reductase (MTHFR) is the key enzyme of folate metabolism in the process of one-carbon cycle and its deficiency results in elevated homocysteine concentration. In this study, we hypothesized that MTHFR C677T polymorphism and homocysteine concentration may play important roles in the development of depressive symptoms in schizophrenia.

METHODS

We recruited 715 patients with stable schizophrenia, and among them, 197 schizophrenia patients under olanzapine monotherapy were enrolled for homocysteine concentration analysis. The Positive and Negative Syndrome Scale (PANSS) and Calgary Depression Scale for Schizophrenia (CDSS) were employed to evaluate psychiatric and depressive symptoms.

RESULTS

When the 715 schizophrenia patients were evaluated by CDSS, 326 individuals (45.6%) had depressive symptoms. No significant differences were observed in C677T genotype and allele distributions between the schizophrenia with or without depression groups. Schizophrenia patients with depression have higher levels of homocysteine than those without depression (P = 0.019). There was a positive correlation between the homocysteine levels and CDSS score (r = 0.22, P = 0.002).

CONCLUSION

Our findings suggested that higher levels of homocysteine may be a risk factor for the development of depressive symptoms in schizophrenia patients.

FOXP2 contributes to the cognitive impairment in chronic patients with schizophrenia

The forkhead-box P2 (FOXP2), involving in language and memory function, has been identified as susceptibility to schizophrenia. However, no study examined the role of FOXP2 on cognitive impairment in schizophrenia. Total 1106 inpatients with schizophrenia and 404 controls were recruited and genotyped. Among them, 867 patients and 402 controls were assessed through the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). SHEsis software was used to investigate the association of FOXP2 rs10447760 with schizophrenia, followed by logistic regression. The model of covariance (ANCOVA) and multivariate analysis were conducted to investigate the effect of FOXP2 rs10447760 on cognitive impairment in schizophrenia. No differences in the genotypic and allelic frequencies of the FOXP2 rs10447760 were found between patients and controls (both p> 0.05). Except for the visuospatial/constructional score (p > 0.05), other five RBANS scores were lower in patients compared to controls (all p < 0.0001). Interestingly, we found immediate memory score was lower in patients carrying genotype CT compared to genotype CC (F=5.19, p=0.02), adjusting for confounding data. Our study suggested that FOXP2 rs10447760 has no effect on the susceptibility to schizophrenia, while it may be associated with its cognitive impairment, especially immediate memory in chronic schizophrenia.

Effects of omega-3 fatty acids on metabolic syndrome in patients with schizophrenia: a 12-week randomized placebo-controlled trial

RATIONALE

Individuals with schizophrenia are at increased risk of developing metabolic syndrome (MetS) due to their lifestyle and antipsychotic treatment. Our previous study showed that patients with both schizophrenia and MetS present an increased expression and production of tumor necrosis factor-alpha (TNF-alpha). Omega-3 fatty acids have a documented role in suppressing TNF-alpha; therefore, we hypothesized that they may be of value in relieving inflammation and improving metabolic disturbance in patients with both schizophrenia and MetS.

OBJECTIVES

This study employed a randomized placebo-controlled trial to investigate the effects of omega-3 fatty acids on MetS in patients with schizophrenia.

METHODS

We recruited 80 patients with both schizophrenia and MetS who received long-term olanzapine monotherapy. The patients were randomly assigned to the OMG-3 group (n = 40) or the placebo group (n = 40).

RESULTS

Patients with both schizophrenia and MetS had significantly higher levels of TNF-alpha than the control subjects (Z = - 4.37, P < 0.01). There was a significant correlation between omega-3 fatty acid treatment and reduced triglyceride (TG) levels (F_{group × time} = 13.42; df = 1, 66; P < 0.01) when the patients completed this study. Along with metabolic improvement, omega-3 fatty acids decreased TNF-alpha levels after 12 weeks of treatment (F_{group × time} = 6.71; df = 1, 66; P = 0.012). We also found that the extent of TNF-alpha decrease was significantly correlated with that of TG decrease (r = 0.38, P = 0.001).

CONCLUSIONS

Our findings provide suggestive evidence that omega-3 fatty acids have beneficial effects on TG metabolism in patients with both schizophrenia and MetS that parallel decreased inflammation levels.

Neurocan Inhibits Semaphorin 3F Induced Dendritic Spine Remodeling Through NrCAM in Cortical Neurons

Neurocan is a chondroitin sulfate proteoglycan present in perineuronal nets, which are associated with closure of the critical period of synaptic plasticity. During postnatal development of the neocortex dendritic spines on pyramidal neurons are initially overproduced; later they are pruned to achieve an appropriate balance of excitatory to inhibitory synapses. Little is understood about how spine pruning is terminated upon maturation. NrCAM (Neuron-glial related cell adhesion molecule) was found to mediate spine pruning as a subunit of the receptor complex for the repellent ligand Semaphorin 3F (Sema3F). As shown here in the postnatal mouse frontal and visual neocortex, Neurocan was localized at both light and electron microscopic level to the cell surface of cortical pyramidal neurons and was adjacent to neuronal processes and dendritic spines. Sema3F-induced spine elimination was inhibited by Neurocan in cortical neuron cultures. Neurocan also blocked Sema3F-induced morphological retraction in COS-7 cells, which was mediated through NrCAM and other subunits of the Sema3F holoreceptor, Neuropilin-2, and PlexinA3. Cell binding and ELISA assays demonstrated an association of Neurocan with NrCAM. Glycosaminoglycan chain interactions of Neurocan were required for inhibition of Sema3F-induced spine elimination, but the C-terminal sushi domain was dispensable. These results describe a novel mechanism wherein Neurocan inhibits NrCAM/Sema3F-induced spine elimination.

Further Evidence of an Association between NCAN rs1064395 and Bipolar Disorder

Genome-wide association studies suggest that rs1064395 in the neurocan gene (NCAN) is a potential risk factor for bipolar disorder (BPD), and further replication analyses in larger independent samples are needed. We herein analyzed rs1064395 in a Han Chinese sample of 1,146 BPD cases and 2,031 controls, followed by a meta-analysis of BPD samples from worldwide populations including a total of 15,318 cases and 91,990 controls. The meta-analysis found that rs1064395 showed a genome-wide significant association with BPD (p = 4.92 × 10^-9, OR = 1.126 for the A allele), although it did not reach the significance level in the Han Chinese sample (p = 0.415, OR = 1.070 for the A allele). We also examined the association between the single nucleotide polymorphisms and major depressive disorder (MDD) given the presumed genetic overlap between BPD and MDD, and rs1064395 was also associated with MDD (p = 0.0068, OR = 1.067 for the A allele) in a meta-analysis of 14,543 cases and 14,856 controls. Our data provide further evidence for the involvement of NCAN in the genetic susceptibility to BPD and also implicate its broader role in major mood disorders.

Brain-derived neurotrophic factor as a biomarker for cognitive recovery in acute schizophrenia: 12-week results from a prospective longitudinal study

RATIONALE

It is generally accepted that impaired cognitive function is a core feature of schizophrenia. There is evidence for the role of brain-derived neurotrophic factor (BDNF) in cognitive function. Olanzapine was reported to yield cognitive improvement in patients with schizophrenia.

OBJECTIVES

In this study, we performed a prospective, open-label, 12-week observation trial to investigate whether peripheral BDNF may represent a potential biomarker for the effect of cognitive improvement induced by olanzapine in patients with schizophrenia.

METHODS

In total, 95 patients with acute schizophrenia were enrolled in the study. We also recruited 72 healthy individuals for a control group. The Positive and Negative Syndrome Scale (PANSS) was used to evaluate symptom severity and treatment response. Cognitive function was evaluated using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Plasma BDNF levels were measured with an enzyme-linked immunosorbent assay.

RESULTS

Of the 95 patients consented into the study, 68 completed the 12-week follow up. Our results showed that schizophrenia patients with acute exacerbation had significantly poorer performance than that of the controls (Ps < 0.01). A significantly decreased plasma level of BDNF in patients was observed compared with the controls (F = 7.77, P = 0.006). A significant improvement in each PANSS subscore and total score was observed when the patients completed this study (Ps < 0.01). Additionally, 12-week olanzapine treatment exhibited significant improvements in RBANS immediate memory, attention, and total scores (P = 0.018, 0.001, and 0.007, respectively). Along with the clinical improvement, plasma BDNF levels after 12-week olanzapine monotherapy (4.67 ± 1.74 ng/ml) were also significantly increased compared with those at baseline (3.38 ± 2.11 ng/ml) (P < 0.01). Spearman's correlation analysis showed that the increase in plasma levels of BDNF is significantly correlated with the change in the RBANS total scores (r = 0.28, P = 0.02) but not with the change in the PANSS total scores (r = - 0.18, P = 0.13). There is a significant correlation of BDNF increase with the change of RBANS attention subscore (r = 0.27, P = 0.028).

CONCLUSIONS

Our findings suggest that olanzapine improves psychiatric symptoms and cognitive dysfunction, particularly attention and immediate memory, in patients with acute schizophrenia, in parallel with increased plasma BDNF levels. Plasma BDNF levels may be a potential biomarker for cognitive recovery in acute schizophrenia.

Interaction between BDNF and TNF-α genes in schizophrenia

OBJECTIVE

Our recent work reported that tumor necrosis factor-α (TNF-α) is negatively correlated with brain-derived neurotrophic factor (BDNF) in patients with schizophrenia. A previous study has shown that TNF-α could regulate the extracellular secretion of BDNF. Therefore, we hypothesized that the TNF-α gene (TNF-α) may interact with the BDNF gene (BDNF) to influence schizophrenia risk.

METHODS

We recruited 694 patients with schizophrenia from three mental hospitals in Eastern China and 725 healthy controls. The Positive and Negative Syndrome Scale (PANSS) was employed to evaluate symptom severity. The Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) was performed to assess cognitive function. The SNPs rs6265 in BDNF and rs1799964 in TNF-α were genotyped.

RESULTS

There were no significant differences in allele and genotype frequencies in either rs6265 or rs1799964 between the case and control groups. A significant association of rs6265 AA + AG × rs1799964 CC + CT with schizophrenia was observed (OR = 1.14, 95%CI: 1.02-1.27; P = .02). There were significant differences in the RBANS attention and total scores between the patients with rs6265A and rs1799964C alleles and those without these two alleles (P = .03 and P = .03 after Bonferroni correction, respectively).

CONCLUSION

Our findings provided preliminary evidence that the interaction of BDNF and TNF-α may confer susceptibility to schizophrenia and cognitive dysfunction.

Genetic association analysis of microRNA137 and its target complex 1 with schizophrenia in Han Chinese

Recent genome-wide association studies (GWAS) have identified a strong association signal of microRNA137 host gene (MIR137) with schizophrenia. MIR137 dysfunction results in downregulation of presynaptic target gene complexin 1 (CPLX1) and impairs synaptic plasticity in the hippocampus. In this study, we aimed to investigate whether the variants of MIR137 and CPLX1 confer susceptibility to schizophrenia in Han Chinese. This study employed 736 patients with schizophrenia patients and 751 well-matched healthy subjects for genetic analysis, and genotyped 12 SNPs within MIR137 and CPLX1. SZDB database was used to performed brain eQTL analysis. There were no significant differences of CPLX1 expression in hippocampus, prefrontal cortex or stratum between the schizophrenia patients and control subjects. No significant differences were observed in allele and genotype frequencies in studied SNPs between the case and control groups. Gene interaction analysis showed that MIR137 SNP rs1625579 did not affect schizophrenia susceptibility in interaction with the CPLX1 polymorphic variants. Our findings do not support MIR137 and CPLX1 conferring susceptibility to schizophrenia in Han Chinese.

Metabolic adverse effects of olanzapine on cognitive dysfunction: A possible relationship between BDNF and TNF-alpha

OBJECTIVE

There is accumulating evidence indicating that long-term treatment with second-generation antipsychotics (SGAs) results in metabolic syndrome (MetS) and cognitive impairment. This evidence suggests an intrinsic link between antipsychotic-induced MetS and cognitive dysfunction in schizophrenia patients. Olanzapine is a commonly prescribed SGA with a significantly higher MetS risk than that of most antipsychotics. In this study, we hypothesized that olanzapine-induced MetS may exacerbate cognitive dysfunction in patients with schizophrenia.

METHODS

A sample of 216 schizophrenia patients receiving long-term olanzapine monotherapy were divided into two groups, MetS and non-MetS, based on the diagnostic criteria of the National Cholesterol Education Program's Adult Treatment Panel III. We also recruited 72 healthy individuals for a control group. Cognitive function was evaluated using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Plasma brain-derived neurotrophic factor (BDNF) and tumor necrosis factor-alpha (TNF-alpha) were measured by an enzyme-linked immunosorbent assay for 108 patients and 47 controls.

RESULTS

Among the 216 schizophrenia patients receiving olanzapine monotherapy, MetS was found in 95/216 (44%). Patients with MetS had more negative symptoms, higher total scores in PANSS (Ps<0.05) and lower immediate memory, attention, delayed memory and total scores in RBANS (Ps<0.01). Stepwise multivariate linear regression analysis revealed that increased glucose was the independent risk factor for cognitive dysfunction (t=-2.57, P=0.01). Patients with MetS had significantly lower BDNF (F=6.49, P=0.012) and higher TNF-alpha (F=5.08, P=0.026) levels than those without MetS. There was a negative correlation between the BDNF and TNF-alpha levels in the patients (r=-0.196, P=0.042).

CONCLUSION

Our findings provide evidence suggesting that the metabolic adverse effects of olanzapine may aggravate cognitive dysfunction in patients with schizophrenia through an interaction between BDNF and TNF-alpha.