TCF4 sequence variants and mRNA levels are associated with neurodevelopmental characteristics in psychotic disorders

Exploration of Positive and Negative Schizophrenia Symptom Heterogeneity and Establishment of Symptom-Related miRNA-mRNA Regulatory Network: Based on Transcriptome Sequencing Data

Schizophrenia (SCZ) symptoms can be classified as positive and negative ones, each of which has distinct traits and possibly differences in gene expression and regulation. The co-expression networks linked to PANSS (Positive and Negative Syndrome Scale) scores were identified by weighted gene co-expression network analysis (WGCNA) using the expression profiles of miRNA and mRNA in the peripheral blood of first-episode SCZ patients. The heterogeneity between positive and negative symptoms was demonstrated using gene functional enrichment, gene-medication interaction, and immune cell composition analysis. Then, target gene prediction and correlation analysis of miRNA and mRNA constructed a symptom-related miRNA-mRNA regulatory network, screened regulatory pairs, and predicted binding sites. A total of six mRNA co-expression modules, two miRNA co-expression modules, and ten hub genes were screened to be significantly associated with positive symptoms; five mRNA co-expression modules and eight hub genes were correlated with negative symptoms. Positive symptom-related modules were significantly enriched in axon guidance, actin skeleton regulation, and sphingolipid signaling pathway, while negative symptom-related modules were significantly enriched in adaptive immune response, leukocyte migration, dopaminergic synapses, etc. The development of positive symptoms may have been influenced by potential regulatory pairings such as miR-98-5p-EIF3J, miR-98-5p-SOCS4, let-7b-5p-CLUH, miR-454-3p-GTF2H1, and let-7b-5p-SNX17. Additionally, immune cells were substantially connected with several hub genes for symptoms. Positive and negative symptoms in SCZ individuals were heterogeneous to some extent. miRNAs such as let-7b-5p and miR-98-5p might contribute to the incidence of positive symptoms by targeting mRNAs, while the immune system's role in developing negative symptoms may be more nuanced.

Disturbed Oligodendroglial Maturation Causes Cognitive Dysfunction in Schizophrenia: A New Hypothesis

BACKGROUND AND HYPOTHESIS

Cognitive impairment is a hallmark of schizophrenia, but no effective treatment is available to date. The underlying pathophysiology includes disconnectivity between hippocampal and prefrontal brain regions. Supporting evidence comes from diffusion-weighted imaging studies that suggest abnormal organization of frontotemporal white matter pathways in schizophrenia.

STUDY DESIGN

Here, we hypothesize that in schizophrenia, deficient maturation of oligodendrocyte precursor cells (OPCs) into mature oligodendrocytes substantially contributes to abnormal frontotemporal macro- and micro-connectivity and subsequent cognitive deficits.

STUDY RESULTS

Our postmortem studies indicate a reduced oligodendrocyte number in the cornu ammonis 4 (CA4) subregion of the hippocampus, and others have reported the same histopathological finding in the dorsolateral prefrontal cortex. Our series of studies on aerobic exercise training showed a volume increase in the hippocampus, specifically in the CA4 region, and improved cognition in individuals with schizophrenia. The cognitive effects were subsequently confirmed by meta-analyses. Cell-specific schizophrenia polygenic risk scores showed that exercise-induced CA4 volume increase significantly correlates with OPCs. From animal models, it is evident that early life stress and oligodendrocyte-related gene variants lead to schizophrenia-related behavior, cognitive deficits, impaired oligodendrocyte maturation, and reduced myelin thickness.

CONCLUSIONS

Based on these findings, we propose that pro-myelinating drugs (e.g., the histamine blocker clemastine) combined with aerobic exercise training may foster the regeneration of myelin plasticity as a basis for restoring frontotemporal connectivity and cognition in schizophrenia.

A typical variant in TCF4 exon 18 is not associated with Pitt-Hopkins syndrome but with a familial case of mild and nonspecific neurodevelopmental disorder

TCF4 gene encodes a class I helix-loop-helix transcription factor critical for the developing brain. Common polymorphisms in TCF4 and disruptive variants in the proximal region of the gene have been linked to relatively mild neuropsychiatric or neurodevelopmental disorders. In contrast, variants impacting distal exons are associated with Pitt-Hopkins syndrome (PTHS), a severe autosomal dominant condition characterized by profound intellectual disability, developmental delay, limited or absent speech, distinctive facies, and disordered breathing. Although phenotypic variability has been observed in PTHS, intellectual impairment and significant speech and motor delays are invariably present. In contrast to the typical de novo variants causing TCF4-related disorder and PTHS, we report a familial form of TCF4-related disorder where the missense variant arose de novo in the father and was inherited by two of his children. Although this family's variant's position in exon 18 predicted a typical PTHS phenotype, none of the affected individuals met the clinical diagnostic criteria for PTHS suggested by Zollino et al. in the first international consensus statement (as in the study by Zollino et al. in 2019). Rather, the three affected family members exhibited remarkably variable and milder phenotypes than would have been predicted from the position of their TCF4 variant. Thus, the clinical spectrum of PTHS-associated TCF4 variants may be broader than previously reported.

Rescue of behavioral and electrophysiological phenotypes in a Pitt-Hopkins syndrome mouse model by genetic restoration of Tcf4 expression

Pitt-Hopkins syndrome (PTHS) is a neurodevelopmental disorder caused by monoallelic mutation or deletion in the transcription factor 4 (TCF4) gene. Individuals with PTHS typically present in the first year of life with developmental delay and exhibit intellectual disability, lack of speech, and motor incoordination. There are no effective treatments available for PTHS, but the root cause of the disorder, TCF4 haploinsufficiency, suggests that it could be treated by normalizing TCF4 gene expression. Here, we performed proof-of-concept viral gene therapy experiments using a conditional Tcf4 mouse model of PTHS and found that postnatally reinstating Tcf4 expression in neurons improved anxiety-like behavior, activity levels, innate behaviors, and memory. Postnatal reinstatement also partially corrected EEG abnormalities, which we characterized here for the first time, and the expression of key TCF4-regulated genes. Our results support a genetic normalization approach as a treatment strategy for PTHS, and possibly other TCF4-linked disorders.

Genome-wide association studies-supported rs12966547 variant of the long noncoding RNA LOC105372125 is significantly associated with susceptibility to schizophrenia and bipolar disorder in Han Chinese women

OBJECTIVE

Genome-wide association studies have found that rs12966547 polymorphism was associated with susceptibility to schizophrenia in European populations. Recent studies showed that a genetic overlap may exist in schizophrenia and bipolar disorder. Here, we analyzed the associations between LOC105372125 rs12966547 polymorphism and schizophrenia and bipolar disorder in the Han Chinese population.

METHODS

Our study recruited 548 schizophrenia patients, 512 bipolar disorder patients, and 598 healthy controls. Genotyping of rs12966547 were performed using the Sequenom MassARRAY platform.

RESULTS

A significant association between rs12966547 polymorphism and susceptibility to bipolar disorder was observed after adjusting for sex and age (additive model: Padj = 0.040, recessive model: Padj = 0.044). However, no significant association was found between rs12966547 polymorphism and schizophrenia risk (all P > 0.05). In the analysis of gender, rs12966547 polymorphism was significantly associated with bipolar disorder (additive model: Padj = 0.027) and schizophrenia (dominant model: Padj = 0.039) in women. However, no significant association was found between rs12966547 polymorphism and the risk of bipolar disorder or schizophrenia in men (all Padj > 0.05).

CONCLUSIONS

Polymorphism of rs12966547 on the long noncoding RNA LOC10537215 are a shared genetic variant of schizophrenia and bipolar disorder in Han Chinese women.

PBLD inhibits angiogenesis via impeding VEGF/VEGFR2-mediated microenvironmental cross-talk between HCC cells and endothelial cells

Sustained anti-angiogenesis therapy increases the level of tumor hypoxia, leading to increased expression of HIF-1a, thereby contributing to the resistance to anti-angiogenesis therapy in hepatocellular carcinoma (HCC). Here, we report that phenazine biosynthesis-like domain-containing protein (PBLD) inhibits hypoxia-induced angiogenesis via ERK/HIF-1a/VEGF axis in HCC cells. Bioinformatic analysis of the TCGA database and clinical samples validation also identify a negative correlation between PBLD and angiogenesis-related genes expression including HIF-1a. Apart from the downregulation of HIF-1a/VEGF expression in HCC cells, PBLD also blocks VEGF receptor 2 (VEGFR2) on endothelial cells via HCC-derived exosomal miR-940. PBLD also activates TCF4 transcriptional promotion effects on miR-940 by directly interacting with it. Together, PBLD exerts an inhibitory effect on angiogenesis not only via blocking the VEGFR2 expression in endothelial cells, but also through downregulating HIF-1a-induced VEGF expression and secretion in HCC cells. These explorations may provide a theoretical basis for exploring new targets and strategies to overcome resistance to anti-angiogenesis therapy.

Shared Genetics and Causality Between Decaffeinated Coffee Consumption and Neuropsychiatric Diseases: A Large-Scale Genome-Wide Cross-Trait Analysis and Mendelian Randomization Analysis

Coffee or caffeine consumption has been associated with neuropsychiatric disorders, implying a shared etiology. However, whether these associations reflect causality remains largely unknown. To understand the genetic structure of the association between decaffeinated coffee consumption (DCC) and neuropsychiatric traits, we examined the genetic correlation, causality, and shared genetic structure between DCC and neuropsychiatric traits using linkage disequilibrium score regression, bidirectional Mendelian randomization (MR), and genome-wide cross-trait meta-analysis in large GWAS Consortia for coffee consumption (N = 329,671) and 13 neuropsychiatric traits (sample size ranges from 36,052 to 500,199). We found strong positive genetic correlations between DCC and lifetime cannabis use (LCU; Rg = 0.48, P = 8.40 × 10^-19), alcohol use disorder identification test (AUDIT) total score (AUDIT_T; Rg = 0.40, P = 4.63 × 10^-13), AUDIT_C score (alcohol consumption component of the AUDIT; Rg = 0.40, P = 5.26 × 10^-11), AUDIT_P score (dependence and hazardous-use component of the AUDIT; Rg = 0.28, P = 1.36 × 10^-05), and strong negative genetic correlations between DCC and neuroticism (Rg = -0.15, P = 7.27 × 10^-05), major depressed diseases (MDD; Rg = -0.15, P = 0.0010), and insomnia (Rg= -0.15, P = 0.0007). In the cross-trait meta-analysis, we identified 6, 5, 1, 1, 2, 31, and 27 shared loci between DCC and Insomnia, LCU, AUDIT_T, AUDIT_C, AUDIT_P, neuroticism, and MDD, respectively, which were mainly enriched in bone marrow, lymph node, cervix, uterine, lung, and thyroid gland tissues, T cell receptor signaling pathway, antigen receptor-mediated signaling pathway, and epigenetic pathways. A large of TWAS-significant associations were identified in tissues that are part of the nervous system, digestive system, and exo-/endocrine system. Our findings further indicated a causal influence of liability to DCC on LCU and low risk of MDD (odds ratio: 0.90, P = 9.06 × 10^-5 and 1.27, P = 7.63 × 10^-4 respectively). We also observed that AUDIT_T and AUDIT_C were causally related to DCC (odds ratio: 1.83 per 1-SD increase in AUDIT_T, P = 1.67 × 10^-05, 1.80 per 1-SD increase in AUDIT_C, P = 5.09 × 10^-04). Meanwhile, insomnia and MDD had a causal negative influence on DCC (OR: 0.91, 95% CI: 0.86-0.95, P = 1.51 × 10^-04 for Insomnia; OR: 0.93, 95% CI: 0.89-0.99, P = 6.02 × 10^-04 for MDD). These findings provided evidence for the shared genetic basis and causality between DCC and neuropsychiatric diseases, and advance our understanding of the shared genetic mechanisms underlying their associations, as well as assisting with making recommendations for clinical works or health education.

Functional consequences of TCF4 missense substitutions associated with Pitt-Hopkins syndrome, mild intellectual disability, and schizophrenia

Transcription factor 4 (TCF4) is a basic helix-loop-helix transcription factor essential for neurocognitive development. The aberrations in TCF4 are associated with neurodevelopmental disorders including schizophrenia, intellectual disability, and Pitt-Hopkins syndrome, an autism-spectrum disorder characterized by developmental delay. Several disease-associated missense mutations in TCF4 have been shown to interfere with TCF4 function, but for many mutations, the impact remains undefined. Here, we tested the effects of 12 functionally uncharacterized disease-associated missense mutations and variations in TCF4 using transient expression in mammalian cells, confocal imaging, in vitro DNA-binding assays, and reporter assays. We show that Pitt-Hopkins syndrome-associated missense mutations within the basic helix-loop-helix domain of TCF4 and a Rett-like syndrome-associated mutation in a transcription activation domain result in altered DNA-binding and transcriptional activity of the protein. Some of the missense variations found in schizophrenia patients slightly increase TCF4 transcriptional activity, whereas no effects were detected for missense mutations linked to mild intellectual disability. We in addition find that the outcomes of several disease-related mutations are affected by cell type, TCF4 isoform, and dimerization partner, suggesting that the effects of TCF4 mutations are context-dependent. Together with previous work, this study provides a basis for the interpretation of the functional consequences of TCF4 missense variants.

Association and Gene-Gene Interactions Study of Late-Onset Alzheimer's Disease in the Russian Population

Alzheimer's disease (AD) is a neurodegenerative disorder, and represents the most common cause of dementia. In this study, we performed several different analyses to detect loci involved in development of the late onset AD in the Russian population. DNA samples from 472 unrelated subjects were genotyped for 63 SNPs using iPLEX Assay and real-time PCR. We identified five genetic loci that were significantly associated with LOAD risk for the Russian population (TOMM40 rs2075650, APOE rs429358 and rs769449, NECTIN rs6857, APOE ε4). The results of the analysis based on comparison of the haplotype frequencies showed two risk haplotypes and one protective haplotype. The GMDR analysis demonstrated three significant models as a result: a one-factor, a two-factor and a three-factor model. A protein-protein interaction network with three subnetworks was formed for the 24 proteins. Eight proteins with a large number of interactions are identified: APOE, SORL1, APOC1, CD33, CLU, TOMM40, CNTNAP2 and CACNA1C. The present study confirms the importance of the APOE-TOMM40 locus as the main risk locus of development and progress of LOAD in the Russian population. Association analysis and bioinformatics approaches detected interactions both at the association level of single SNPs and at the level of genes and proteins.

Transcription factors in neurodevelopmental and associated psychiatric disorders: A potential convergence for genetic and environmental risk factors

Neurodevelopmental disorders (NDDs) are a heterogeneous and highly prevalent group of psychiatric conditions marked by impairments in the nervous system. Their onset occurs during gestation, and the alterations are observed throughout the postnatal life. Although many genetic and environmental risk factors have been described in this context, the interactions between them challenge the understanding of the pathways associated with NDDs. Transcription factors (TFs)-a group of over 1,600 proteins that can interact with DNA, regulating gene expression through modulation of RNA synthesis-represent a point of convergence for different risk factors. In addition, TFs organize critical processes like angiogenesis, blood-brain barrier formation, myelination, neuronal migration, immune activation, and many others in a time and location-dependent way. In this review, we summarize important TF alterations in NDD and associated disorders, along with specific impairments observed in animal models, and, finally, establish hypotheses to explain how these proteins may be critical mediators in the context of genome-environment interactions.

Transcription factor 4 and its association with psychiatric disorders

The human transcription factor 4 gene (TCF4) encodes a helix-loop-helix transcription factor widely expressed throughout the body and during neural development. Mutations in TCF4 cause a devastating autism spectrum disorder known as Pitt-Hopkins syndrome, characterized by a range of aberrant phenotypes including severe intellectual disability, absence of speech, delayed cognitive and motor development, and dysmorphic features. Moreover, polymorphisms in TCF4 have been associated with schizophrenia and other psychiatric and neurological conditions. Details about how TCF4 genetic variants are linked to these diseases and the role of TCF4 during neural development are only now beginning to emerge. Here, we provide a comprehensive review of the functions of TCF4 and its protein products at both the cellular and organismic levels, as well as a description of pathophysiological mechanisms associated with this gene.

Genome-wide association study of self-reported walking pace suggests beneficial effects of brisk walking on health and survival

Walking is a simple form of exercise, widely promoted for its health benefits. Self-reported walking pace has been associated with a range of cardiorespiratory and cancer outcomes, and is a strong predictor of mortality. Here we perform a genome-wide association study of self-reported walking pace in 450,967 European ancestry UK Biobank participants. We identify 70 independent associated loci (P < 5 × 10^-8), 11 of which are novel. We estimate the SNP-based heritability as 13.2% (s.e. = 0.21%), reducing to 8.9% (s.e. = 0.17%) with adjustment for body mass index. Significant genetic correlations are observed with cardiometabolic, respiratory and psychiatric traits, educational attainment and all-cause mortality. Mendelian randomization analyses suggest a potential causal link of increasing walking pace with a lower cardiometabolic risk profile. Given its low heritability and simple measurement, these findings suggest that self-reported walking pace is a pragmatic target for interventions aiming for general benefits on health.

Modulation of cognition and neuronal plasticity in gain- and loss-of-function mouse models of the schizophrenia risk gene Tcf4

The transcription factor TCF4 was confirmed in several large genome-wide association studies as one of the most significant schizophrenia (SZ) susceptibility genes. Transgenic mice moderately overexpressing Tcf4 in forebrain (Tcf4tg) display deficits in fear memory and sensorimotor gating. As second hit, we exposed Tcf4tg animals to isolation rearing (IR), chronic social defeat (SD), enriched environment (EE), or handling control (HC) conditions and examined mice with heterozygous deletion of the exon 4 (Tcf4Ex4δ^+/-) to unravel gene-dosage effects. We applied multivariate statistics for behavioral profiling and demonstrate that IR and SD cause strong cognitive deficits of Tcf4tg mice, whereas EE masked the genetic vulnerability. We observed enhanced long-term depression in Tcf4tg mice and enhanced long-term potentiation in Tcf4Ex4δ^+/- mice indicating specific gene-dosage effects. Tcf4tg mice showed higher density of immature spines during development as assessed by STED nanoscopy and proteomic analyses of synaptosomes revealed concurrently increased levels of proteins involved in synaptic function and metabolic pathways. We conclude that environmental stress and Tcf4 misexpression precipitate cognitive deficits in 2-hit mouse models of relevance for schizophrenia.

Genome-scale metabolic modelling predicts biomarkers and therapeutic targets for neuropsychiatric disorders

Distinguishing neuropsychiatric disorders is challenging due to the overlap in symptoms and genetic risk factors. People suffering from these disorders face personal and professional challenges. Understanding the dysregulation of brain metabolism under disease condition can aid in effective diagnosis and in developing treatment strategies based on the metabolism. In this study, we reconstructed the metabolic network of three major neuropsychiatric disorders, schizophrenia (SCZ), bipolar disorder (BD) and major depressive disorder (MDD) using transcriptomic data and constrained based modelling approach. We integrated brain transcriptomic data from six independent studies with a recent comprehensive genome-scale metabolic model Recon3D. The analysis of the reconstructed network revealed the flux-level alterations in the peroxisome-mitochondria-golgi axis in neuropsychiatric disorders. We also extracted reporter metabolites and pathways that distinguish these three neuropsychiatric disorders. We found differences with respect to fatty acid oxidation, aromatic and branched chain amino acid metabolism, bile acid synthesis, glycosaminoglycans synthesis and modifications, and phospholipid metabolism. Further, we predicted network perturbations that transform the disease metabolic state to a healthy metabolic state for each disorder. These analyses provide local and global views of the metabolic changes in SCZ, BD and MDD, which may have clinical implications.

[A new look at the genetics of neurocognitive deficits in schizophrenia]

The article presents current literature data on genetic studies of neurocognitive deficit in schizophrenia, including the genes of neurotransmitter systems (dopaminergic, glutamatergic, and serotonergic); genes analyzed in genome-wide association studies (GWAS), as well as other genetic factors related to the pathophysiological mechanisms underlying schizophrenia and neurocognitive disorders.

Tcf4 is required for correct brain development during embryogenesis

Tcf4 has been linked to autism, schizophrenia, and Pitt-Hopkins Syndrome (PTHS) in humans, suggesting a role for Tcf4 in brain development and importantly cortical development. However, the mechanisms behind its role in disease and brain development are still elusive. We provide evidence that Tcf4 has a critical function in the differentiation of cortical regions, corpus callosum and anterior commissure formation, and development of the hippocampus during murine embryonic development. In the present study, we show that Tcf4 is expressed throughout the developing brain at the peak of neurogenesis. Deletion of Tcf4 results in mis-specification of the cortical neurons, malformation of the corpus callosum and anterior commissure, and hypoplasia of the hippocampus. Furthermore, the Tcf4 mutant shows an absence of midline remodeling, underlined by the loss of GFAP-expressing midline glia in the indusium griseum and callosal wedge and midline zipper glia in the telencephalic midline. RNA-sequencing on E14.5 cortex material shows that Tcf4 functions as a transcriptional activator and loss of Tcf4 results in downregulation of genes linked to neurogenesis and neuronal maturation. Furthermore, many genes that are differentially expressed after Tcf4 ablation are linked to other neurodevelopmental disorders. Taken together, we show that correct brain development and neuronal differentiation are severely affected in Tcf4 mutants, phenocopying morphological brain defects detected in PTHS patients. The presented data identifies new leads to understand the mechanisms behind brain and specifically cortical development and can provide novel insights in developmental mechanisms underlying human brain defects.

Association between a TCF4 Polymorphism and Susceptibility to Schizophrenia

The basic helix-loop-helix (bHLH) transcription factor 4 (TCF4) had been identified as a susceptibility gene associated with schizophrenia (SCZ) by GWAS, but inconsistent results have been found in other studies. To validate these findings and to reveal the effects of different inheritance models, rs2958182, rs1261085, rs8766, and rs12966547 of the TCF4 gene were genotyped in the Northwest Han Chinese population (448 cases and 628 controls) via a multiplex polymerase chain reaction SNPscan assay. Single SNP, genotype, and association analyses with three different models were performed. We observed genotype and allele distributions of four SNPs that showed nonsignificant associations in the Northwest Han Chinese population. However, published datasets (51,892 cases and 68,498 controls) were collected and combined with our experimental results to ascertain the association of the TCF4 gene SNPs and SCZ, which demonstrated that rs2958182 (P=0.003) was a significant signal based on a systematic meta-analysis. To clarify the biological role of rs2958182, it is important to improve the understanding of the pathophysiology of SCZ.

The subcellular localization of bHLH transcription factor TCF4 is mediated by multiple nuclear localization and nuclear export signals

Transcription factor 4 (TCF4) is a class I basic helix-loop-helix (bHLH) transcription factor which regulates the neurogenesis and specialization of cells. TCF4 also plays an important role in the development and functioning of the immune system. Additionally, TCF4 regulates the development of Sertoli cells and pontine nucleus neurons, myogenesis, melanogenesis and epithelial-mesenchymal transition. The ability of transcription factors to fulfil their function often depends on their intracellular trafficking between the nucleus and cytoplasm of the cell. The trafficking is regulated by specific sequences, i.e. the nuclear localization signal (NLS) and the nuclear export signal (NES). We performed research on the TCF4 trafficking regulating sequences by mapping and detailed characterization of motifs potentially acting as the NLS or NES. We demonstrate that the bHLH domain of TCF4 contains an NLS that overlaps two NESs. The results of in silico analyses show high conservation of the sequences, especially in the area of the NLS and NESs. This high conservation is not only between mouse and human TCF4, but also between TCF4 and other mammalian E proteins, indicating the importance of these sequences for the functioning of bHLH class I transcription factors.

Genotype Variations of rs13381800 in TCF4 Gene and rs17039988 in NRXN1 Gene among a Sample of Iranian Patients with Schizophrenia

Objective: Schizophrenia is a complicated mental disorder that affects about 1% of the world's population. It is a complex disease and is approximately 80% inherited. One of the candidate genes in schizophrenia is transcription factor 4 (TCF4), which is positioned on chromosome 18 and is a transcription factor that plays a role in the transcription of Neurexin 1(NRXN1) gene, which is one of the candidate genes for developing schizophrenia. This case-control study aimed to investigate the correlation of TCF4 rs13381800 and NRXN1 rs17039988 polymorphisms with the risk of schizophrenia in a sample of Iranian patients with schizophrenia. Method : A total of 200 individuals were included in this study: 100 patients with schizophrenia (65 males and 35 females), with the mean age of 40.80 ± 11.298 years, and 100 as a control group (63 males and 37 females), with the mean age 32.92 ± 7.391 years. Allele specific polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) were done, respectively, for genotyping of rs13381800 (T/C) and rs17039988 (A/C) polymorphisms. Results: The results showed that the frequency of C / C genotype in rs13381800 in patients' group was 9%, while it was 13% in the control group. Also, the frequency of C / C genotype in rs17039988 was 9% in patients and 7% in control groups. Statistical analysis of polymorphisms showed no correlation between patients and controls in rs13381800 (OR = 1.51; CI = 95%; P = 0.366) and rs17039988 (OR = 0.76; CI = 95%; P = 0.602). Conclusion: No significant difference was found between rs13381800 and rs17039988 genotypes between patients and control groups in terms of gender, age and education in the patients group. Our study suggests that there was no correlation between desired polymorphisms with schizophrenia in the studied population.

Disruption of TCF4 regulatory networks leads to abnormal cortical development and mental disabilities

The TCF4 gene is the subject of numerous and varied investigations of it's role in the genesis of neuropsychiatric disease. The gene has been identified as the cause of Pitt-Hopkins syndrome (PTHS) and it has been implicated in various other neuropsychiatric diseases, including schizophrenia, depression, and autism. However, the precise molecular mechanisms of the gene's involvement in neurogenesis, particularly, corticogenesis, are not well understood. Here, we present data showing that TCF4 is expressed in a region-specific manner in the radial glia and stem cells of transient embryonic zones at early gestational ages in both humans and mice. TCF4 haploinsufficiency mice exhibit a delay in neuronal migration, and a significant increase in the number of upper-layer cortical neurons, as well as abnormal dendrite and synapse formation. Our research also reveals that TCF3 up-regulates Tcf4 by binding to the specific "E-box" and its flank sequence in intron 2 of the Tcf4 gene. Additionally, our transcriptome study substantiates that Tcf4 transcriptional function is essential for locomotion, cognition, and learning. By activating expression of TCF4 in the regulation of neuronal proliferation and migration to the overlaying neocortex and subsequent differentiation leading to laminar formation TCF4 fulfills its normal function, but if not, abnormalities such as those reported here result. These findings provide new insight into the specific roles of Tcf4 molecular pathway in neocortical development and their relevance in the pathogenesis of neuropsychiatric diseases.

Genetic Variability of TCF4 in Schizophrenia of Southern Chinese Han Population: A Case-Control Study

Objective: Schizophrenia is thought to be a neurodevelopmental disorder. As a key regulator in the development of the central nervous system, transcription factor 4 (TCF4) has been shown to be involved in the pathogenesis of schizophrenia. The aim of our study was to assay the association of TCF4 single nucleotide polymorphisms (SNPs) with schizophrenia and the effect of these SNPs on phenotypic variability in schizophrenia in Southern Chinese Han Population.

Methods: Four SNPs (rs9960767, rs2958182, rs4309482, and rs12966547) of TCF4 were genotyped in 1137 schizophrenic patients and 1035 controls in a Southern Chinese Han population using the improved multiplex ligation detection reaction (iMLDR) technique. For patients with schizophrenia, the severity of symptom phenotypes was analyzed by the five-factor model of the Positive and Negative Symptom Scale (PANSS). Cognitive function was assessed using the Brief Assessment of Cognition in Schizophrenia (BACS) scale.

Results: The results showed that the genotypes and alleles of the three SNPs (rs2958182, rs4309482, and rs12966547) were not significantly different between the control group and the case group (all P > 0.05). rs9960767 could not be included in the statistics for the extremely low minor allele frequency. However, the genotypes of rs4309482 shown a potential risk in the positive symptoms (P = 0.04) and excitement symptoms (P = 0.04) of the five-factor model of PANSS, but not survived in multiple test correction. The same potential risk was shown in the rs12966547 in positive symptoms of the PANSS (P = 0.03).

Conclusion: Our results failed to find the associations of SNPs (rs2958182, rs4309482, and rs12966547) in TCF4 with schizophrenia in Southern Chinese Han Population.

Effect of Trinucleotide Repeat Expansion on the Expression of TCF4 mRNA in Fuchs' Endothelial Corneal Dystrophy

Purpose

CTG trinucleotide repeat (TNR) expansion is frequently found in transcription factor 4 (TCF4) in Fuchs' endothelial corneal dystrophy (FECD), though the effect of TNR expansion on FECD pathophysiology remains unclear. The purpose of this study was to evaluate the effect of TNR expansion on TCF4 expression in corneal endothelium of patients with FECD.

Methods

Peripheral blood DNA and Descemet membrane with corneal endothelium were obtained from 203 German patients with FECD. The CTG TNR repeat length in TCF4 was determined by short tandem repeat (STR) assays and Southern blotting using genomic DNA. Genotyping of rs613872 in TCF4 was performed by PCR. TCF4 mRNA levels in corneal endothelium were evaluated by quantitative PCR using three different probes. Control corneal endothelial samples were obtained from 35 non-FECD subjects.

Results

The STR assay and Southern blotting showed that 162 of the 203 patients with FECD (80%) harbored CTG trinucleotide repeat lengths larger than 50. Quantitative PCR using all three probes demonstrated that TCF4 mRNA is significantly upregulated in the corneal endothelium of patients with FECD, regardless of the presence of TNR expansion. However, the length of the TNR tended to show a positive correlation with TCF4 expression level. No correlation was shown between the genotype of TCF4 SNP, rs613872, and the level of TCF4 expression.

Conclusions

Our findings showed that TCF4 mRNA is upregulated in the corneal endothelium of patients with FECD. Further studies on the effects of TCF4 upregulation on corneal endothelial cell function will aid in understanding the pathophysiology of FECD.

TCF4 and GRM8 gene polymorphisms and risk of schizophrenia in an Iranian population: a case-control study

TCF4 and GRM8, two significant genes involved in the normal nervous development and glutamate pathway, are thought to be involved in the pathogenesis of schizophrenia (SCZ). We aimed to explore the association of TCF4 and GRM8 gene polymorphisms with risk of SCZ. The rs8766 in TCF4 and rs712723 in GRM8 were selected for genotyping in a set of Iranian case-control samples including 215 patients and 220 matched healthy controls using polymerase chain reaction-restriction fragment length polymorphism. Although rs8766 increased the OR, we found that rs8766 allele and genotype frequencies were not significantly different between case and control groups and a significant association cannot be suggested for the selected SNP. However, allele C and genotype CC (allele C: OR 1.48, 95% CI 1.13-1.94; genotype CC: OR 1.71, 95% CI 1.09-2.68) of rs712723 polymorphism was found to have a significant association with risk of SCZ. Frequency of allele C (P = 0.003) and genotype CC (P = 0.017) was higher in the schizophrenic patients, while allele T (P = 0.003) and genotype TT (P = 0.028) frequencies were found lower in patients. Our findings indicate that rs712723 in GRM8 may play an important role in the pathogenesis of SCZ. However, our conclusion needs to be confirmed in other population.

Imaging genetics of schizophrenia in the post-GWAS era

Imaging genetics is a research methodology studying the effect of genetic variation on brain structure, function, behavior, and risk for psychopathology. Since the early 2000s, imaging genetics has been increasingly used in the research of schizophrenia (SZ). SZ is a severe mental disorder with no precise knowledge of its underlying neurobiology, however, new genetic and neurobiological data generate a climate for new avenues. The accumulating data of genome wide association studies (GWAS) continuously decode SZ risk genes. Global neuroimaging consortia produce collections of brain phenotypes from tens of thousands of people. In this context, imaging genetics will be strategically important both for the validation and discovery of SZ related findings. Thus, the study of GWAS supported risk variants as candidate genes to validate by neuroimaging is one trend. The study of epigenetic differences in relation to variations of brain phenotypes and the study of large scale multivariate analysis of genome wide and brain wide associations are other trends. While these studies hold a big potential for understanding the neurobiology of SZ, the problem of reproducibility appears as a major challenge, which requires standardizations in study designs and compensations of methodological limitations such as sensitivity and specificity. On the other hand, advancements of neuroimaging, optical and electron microscopy along with the use of genetically encoded fluorescent probes and robust statistical approaches will not only catalyze integrative methodologies but also will help better design the imaging genetics studies. In this invited paper, I will discuss the current perspective of imaging genetics and emerging opportunities of SZ research.

Expression of schizophrenia biomarkers in extraocular muscles from patients with strabismus: an explanation for the link between exotropia and schizophrenia?

Recent studies have implicated exotropia as a risk factor for schizophrenia. We determined whether schizophrenia biomarkers have abnormal levels of expression in extraocular muscles from patients with strabismus and explored whether differences in gene expression between medial and lateral rectus muscles may explain the specific association of schizophrenia with exotropia but not esotropia. Samples from horizontal extraocular muscles were obtained during strabismus surgery and compared with age- and muscle type-matched normal muscles from organ donors. We used PCR arrays to identify differences in gene expression among 417 signaling molecules. We then focused on established schizophrenia-related growth factors, cytokines, and regulators of the extracellular matrix. Among 36 genes with significantly altered gene expression in dysfunctional horizontal rectus muscles, over one third were schizophrenia-related: CTGF, CXCR4, IL1B, IL10RA, MIF, MMP2, NPY1R, NRG1, NTRK2, SERPINA3, TIMP1, TIMP2, and TNF (adjusted p value ≤ 0.016667). By PCR array, expression of three of these genes was significantly different in medial rectus muscles, while eleven were significantly altered in lateral rectus muscles. Comparing baseline levels between muscle types, three schizophrenia-related genes (NPY1R, NTRK2, TIMP2) had lower levels of expression in medial rectus muscles. Despite the surprisingly large number of schizophrenia-related genes with altered gene expression levels in dysfunctional muscles, the lack of specificity for medial rectus muscles undermines a model of shared, region-specific gene expression abnormalities between exotropia and schizophrenia, but rather suggests consideration of the alternative model: that exotropia-induced aberrant early visual experiences may enable and/or contribute as a causative factor to the development of schizophrenia.

Analysis of the joint effect of SNPs to identify independent loci and allelic heterogeneity in schizophrenia GWAS data

We have tested published methods for capturing allelic heterogeneity and identifying loci of joint effects to uncover more of the "hidden heritability" of schizophrenia (SCZ). We used two tools, cojo-GCTA and multi-SNP, to analyze meta-statistics from the latest genome-wide association study (GWAS) on SCZ by the Psychiatric Genomics Consortium (PGC). Stepwise regression on markers with p values <10^-7 in cojo-GCTA identified 96 independent signals. Eighty-five passed the genome-wide significance threshold. Cross-validation of cojo-GCTA by CLUMP was 76%, i.e., 26 of the loci identified by the PGC using CLUMP were found to be dependent on another locus by cojo-GCTA. The overlap between cojo-GCTA and multi-SNP was better (up to 92%). Three markers reached genome-wide significance (5 × 10^-8) in a joint effect model. In addition, two loci showed possible allelic heterogeneity within 1-Mb genomic regions, while CLUMP analysis had identified 16 such regions. Cojo-GCTA identified fewer independent loci than CLUMP and seems to be more conservative, probably because it accounts for long-range LD and interaction effects between markers. These findings also explain why fewer loci with possible allelic heterogeneity remained significant after cojo-GCTA analysis. With multi-SNP, 86 markers were selected at the threshold 10^-7. Multi-SNP identifies fewer independent signals, due to splitting of the data and use of smaller samples. We recommend that cojo-GCTA and multi-SNP are used for post-GWAS analysis of all traits to call independent loci. We conclude that only a few loci in SCZ show joint effects or allelic heterogeneity, but this could be due to lack of power for that data set.

Genetic Basis of Positive and Negative Symptom Domains in Schizophrenia

Schizophrenia is a highly heritable disorder, the genetic etiology of which has been well established. Yet despite significant advances in genetics research, the pathophysiological mechanisms of this disorder largely remain unknown. This gap has been attributed to the complexity of the polygenic disorder, which has a heterogeneous clinical profile. Examining the genetic basis of schizophrenia subphenotypes, such as those based on particular symptoms, is thus a useful strategy for decoding the underlying mechanisms. This review of literature examines the recent advances (from 2011) in genetic exploration of positive and negative symptoms in schizophrenia. We searched electronic databases PubMed, Web of Science, and Cumulative Index to Nursing and Allied Health Literature using key words schizophrenia, symptoms, positive symptoms, negative symptoms, cognition, genetics, genes, genetic predisposition, and genotype in various combinations. We identified 115 articles, which are included in the review. Evidence from these studies, most of which are genetic association studies, identifies shared and unique gene associations for the symptom domains. Genes associated with neurotransmitter systems and neuronal development/maintenance primarily constitute the shared associations. Needed are studies that examine the genetic basis of specific symptoms within the broader domains in addition to functional mechanisms. Such investigations are critical to developing precision treatment and care for individuals afflicted with schizophrenia.

Knockdown of the schizophrenia susceptibility gene TCF4 alters gene expression and proliferation of progenitor cells from the developing human neocortex

BACKGROUND

Common variants in the TCF4 gene are among the most robustly supported genetic risk factors for schizophrenia. Rare TCF4 deletions and loss-of-function point mutations cause Pitt-Hopkins syndrome, a developmental disorder associated with severe intellectual disability.

METHODS

To explore molecular and cellular mechanisms by which TCF4 perturbation could interfere with human cortical development, we experimentally reduced the endogenous expression of TCF4 in a neural progenitor cell line derived from the developing human cerebral cortex using RNA interference. Effects on genome-wide gene expression were assessed by microarray, followed by Gene Ontology and pathway analysis of differentially expressed genes. We tested for genetic association between the set of differentially expressed genes and schizophrenia using genome-wide association study data from the Psychiatric Genomics Consortium and competitive gene set analysis (MAGMA). Effects on cell proliferation were assessed using high content imaging.

RESULTS

Genes that were differentially expressed following TCF4 knockdown were highly enriched for involvement in the cell cycle. There was a nonsignificant trend for genetic association between the differentially expressed gene set and schizophrenia. Consistent with the gene expression data, TCF4 knockdown was associated with reduced proliferation of cortical progenitor cells in vitro.

LIMITATIONS

A detailed mechanistic explanation of how TCF4 knockdown alters human neural progenitor cell proliferation is not provided by this study.

CONCLUSION

Our data indicate effects of TCF4 perturbation on human cortical progenitor cell proliferation, a process that could contribute to cognitive deficits in individuals with Pitt-Hopkins syndrome and risk for schizophrenia.

Genetic Association of TCF4 and AKT1 Gene Variants with the Age at Onset of Schizophrenia

BACKGROUND

Age at onset (AAO) is a known prognostic indicator for schizophrenia and is hypothesized to correlate with cognition and symptom severity. TCF4 and AKT1 are schizophrenia risk genes involved in cognitive functions. The current study examined the interactive effects of TCF4 and AKT1 variants with gender, family history of psychiatric disorders and ethnicity on the AAO of schizophrenia.

METHODS

This study consisted of 322 patients with schizophrenia meeting the DSM-IV criteria. Six single nucleotide polymorphisms (SNPs) of TCF4 (rs12966547, rs8766, rs2958182, rs9960767, rs10401120 and rs17512836) and seven AKT1 SNPs (rs2498804, rs3803304, rs2494732, rs3730358, rs1130214, rs2498784 and rs3803300) were genotyped using the TaqMan® SNP genotyping-based assays method. The relationship of AAO with each variant was investigated using analyses of covariance.

RESULTS

Among the TCF4 variants, rs12966547 (p = 0.024) and rs8766 (p = 0.021) were significantly associated with earlier AAO. We found a lower average AAO in patients with the AA genotype of rs12966547, while the CT genotype of rs8766 was demonstrated to have a protective effect on AAO. For rs8766, there was significant gene × gender interaction (p = 0.012) in influencing AAO. However, these results were not significant after false discovery rate correction. Significant gene × ethnicity interactions were observed to influence AAO (p < 0.05). The Kaplan-Meier curve of the minor AA genotype of rs12966547 displayed a significant trend (p = 0.008) for onset after 19 years of age. Similarly, the minor CC genotype of rs8766 showed a significantly (p = 0.034) lower AAO compared to the TT genotype.

CONCLUSION

Our analyses suggest that individual risk genotypes may influence the risk of schizophrenia in an age-specific manner.

Functional neuroimaging effects of recently discovered genetic risk loci for schizophrenia and polygenic risk profile in five RDoC subdomains

Recently, 125 loci with genome-wide support for association with schizophrenia were identified. We investigated the impact of these variants and their accumulated genetic risk on brain activation in five neurocognitive domains of the Research Domain Criteria (working memory, reward processing, episodic memory, social cognition and emotion processing). In 578 healthy subjects we tested for association (i) of a polygenic risk profile score (RPS) including all single-nucleotide polymorphisms (SNPs) reaching genome-wide significance in the recent genome-wide association studies (GWAS) meta-analysis and (ii) of all independent genome-wide significant loci separately that showed sufficient distribution of all allelic groups in our sample (105 SNPs). The RPS was nominally associated with perigenual anterior cingulate and posterior cingulate/precuneus activation during episodic memory (P_FWE(ROI)=0.047) and social cognition (P_FWE(ROI)=0.025), respectively. Single SNP analyses revealed that rs9607782, located near EP300, was significantly associated with amygdala recruitment during emotion processing (P_FWE(ROI)=1.63 × 10^-4, surpassing Bonferroni correction for the number of SNPs). Importantly, this association was replicable in an independent sample (N=150; P_FWE(ROI)<0.025). Other SNP effects previously associated with imaging phenotypes were nominally significant, but did not withstand correction for the number of SNPs tested. To assess whether there was true signal within our data, we repeated single SNP analyses with 105 randomly chosen non-schizophrenia-associated variants, observing fewer significant results and lower association probabilities. Applying stringent methodological procedures, we found preliminary evidence for the notion that genetic risk for schizophrenia conferred by rs9607782 may be mediated by amygdala function. We critically evaluate the potential caveats of the methodological approaches employed and offer suggestions for future studies.

Polymorphisms of the TCF4 gene are associated with the risk of schizophrenia in the Han Chinese

Schizophrenia (SCZ) is a complex and severe mental disorder with highly heritability (80%). Several large genome-wide association studies have identified that the transcription factor 4 (TCF4) polymorphisms were strongly associated with SCZ. Therefore, the present study was to replicate the potential relationships between the TCF4 polymorphisms and SCZ. Furthermore, the study also investigated whether other variants were associated with SCZ in the Han Chinese. We conducted a case-control study including 499 patients and 500 healthy controls. Five SNPs were successfully genotyped and evaluated the association with SCZ by using χ² test and genetic model analysis. We found that the genotype "AG" of rs9320010 and "GA" of rs7235757 decreased SCZ risk (OR = 0.70, 95%CI = 0.50-0.99, P = 0.041; OR = 0.69, 95%CI = 0.49-0.97, P = 0.034, respectively). In the genetic model analysis, we also observed that the allele "A" of rs9320010 and "G" of rs7235757 were inversely related with the risk of SCZ in the dominant model (OR = 0.72, 95%CI = 0.52-0.98, P = 0.039; OR = 0.69, 95%CI = 0.50-0.96, P = 0.025, respectively). Further interaction and stratification analysis suggested that rs1452787 was notably correlated with increased SCZ risk in males (OR = 2.77, 95%CI = 1.43-5.35, P = 0.002). Our study indicated that rs9320010, rs7235757, and rs1452787 were prominently associated with SCZ. Further studies are required to verify our findings and focus on determining the biological functions of the SNPs. © 2016 Wiley Periodicals, Inc.

Association of CACNA1C and SYNE1 in offspring of patients with psychiatric disorders

Schizophrenia (SZ) and bipolar disorder (BD) are severe mental diseases associated with cognitive impairment, mood disturbance, and psychosis. Both disorders are highly heritable and share a common genetic background. The present study assesses, for the first time, differences in genotype frequencies of polymorphisms located in genes involved in neurodevelopment and synaptic plasticity between genetic high-risk individuals (offspring of patients with SZ or BD; N=100: 31 and 69, respectively) and control subjects (offspring of community controls; N=96). Individuals from both groups had similar ages, around 12 years. A higher percentage of men were included in the genetic high-risk group (58%) compared with the control group (40.6%). A total of 244 validated SNPs located in 35 candidate gene regions were analyzed in 196 participants. Multivariate methods based on logistic regression analysis were performed to assess differences in genotype frequencies. Bonferroni correction was applied for the multiple comparisons performed. Two polymorphisms, CACNA1C rs10848683 and SYNE1 rs214950, showed significant differences. The frequency of heterozygotes for CACNA1C rs10848683 in genetic high-risk individuals was double that in controls (OR=3.15; P=0.00016). For SYNE1 rs214950, higher frequencies of heterozygotes (OR=1.97) and homozygotes for the minor allele (OR=17.89; P=0.00020) were found in the genetic high-risk group than in the control group. In conclusion, polymorphisms in CACNA1C and SYNE1 could confer a greater risk of developing SZ and BD in individuals who are already at high risk because of their family history. This could help identify subjects with a very high genetic risk, in whom early detection and early intervention could lead to better prognosis.

A Genome-Wide Arrayed cDNA Screen to Identify Functional Modulators of α7 Nicotinic Acetylcholine Receptors

Cellular signaling is in part regulated by the composition and subcellular localization of a series of protein interactions that collectively form a signaling complex. Using the α7 nicotinic acetylcholine receptor (α7nAChR) as a proof-of-concept target, we developed a platform to identify functional modulators (or auxiliary proteins) of α7nAChR signaling. The Broad cDNA library was transiently cotransfected with α7nAChR cDNA in HEK293T cells in a high-throughput fashion. Using this approach in combination with a functional assay, we identified positive modulators of α7nAChR activity. We identified known positive modulators/auxiliary proteins present in the cDNA library that regulate α7nAChR signaling, in addition to identifying novel modulators of α7nAChR signaling. These included NACHO, SPDYE11, TCF4, and ZC3H12A, all of which increased PNU-120596-mediated nicotine-dependent calcium flux. Importantly, these auxiliary proteins did not modulate GluR1(o)-mediated Ca flux. To elucidate a possible mechanism of action, we employed an α7nAChR-HA surface staining assay. NACHO enhanced α7nAChR surface expression; however, the mechanism responsible for the SPDYE11-, TCF4-, and ZC3H12A-dependent modulation of α7nAChR has yet to be defined. This report describes the development and validation of a high-throughput, genome-wide cDNA screening platform coupled to FLIPR functional assays in order to identify functional modulators of α7nAChR signaling.

An examination of the language construct in NIMH's research domain criteria: Time for reconceptualization!

The National Institute of Mental Health's Research Domain Criteria (RDoC) Initiative "calls for the development of new ways of classifying psychopathology based on dimensions of observable behavior." As a result of this ambitious initiative, language has been identified as an independent construct in the RDoC matrix. In this article, we frame language within an evolutionary and neuropsychological context and discuss some of the limitations to the current measurements of language. Findings from genomics and the neuroimaging of performance during language tasks are discussed in relation to serious mental illness and within the context of caveats regarding measuring language. Indeed, the data collection and analysis methods employed to assay language have been both aided and constrained by the available technologies, methodologies, and conceptual definitions. Consequently, different fields of language research show inconsistent definitions of language that have become increasingly broad over time. Individually, they have also shown significant improvements in conceptual resolution, as well as in experimental and analytic techniques. More recently, language research has embraced collaborations across disciplines, notably neuroscience, cognitive science, and computational linguistics and has ultimately re-defined classical ideas of language. As we move forward, the new models of language with their remarkably multifaceted constructs force a re-examination of the NIMH RDoC conceptualization of language and thus the neuroscience and genetics underlying this concept. © 2016 The Authors. American Journal of Medical Genetics Part B: Neuropsychiatric Genetics Published by Wiley Periodicals, Inc.

Tcf4 transgenic female mice display delayed adaptation in an auditory latent inhibition paradigm

Schizophrenia (SZ) is a severe mental disorder affecting about 1 % of the human population. Patients show severe deficits in cognitive processing often characterized by an improper filtering of environmental stimuli. Independent genome-wide association studies confirmed a number of risk variants for SZ including several associated with the gene encoding the transcription factor 4 (TCF4). TCF4 is widely expressed in the central nervous system of mice and humans and seems to be important for brain development. Transgenic mice overexpressing murine Tcf4 (Tcf4tg) in the adult brain display cognitive impairments and sensorimotor gating disturbances. To address the question of whether increased Tcf4 gene dosage may affect cognitive flexibility in an auditory associative task, we tested latent inhibition (LI) in female Tcf4tg mice. LI is a widely accepted translational endophenotype of SZ and results from a maladaptive delay in switching a response to a previously unconditioned stimulus when this becomes conditioned. Using an Audiobox, we pre-exposed Tcf4tg mice and their wild-type littermates to either a 3- or a 12-kHz tone before conditioning them to a 12-kHz tone. Tcf4tg animals pre-exposed to a 12-kHz tone showed significantly delayed conditioning when the previously unconditioned tone became associated with an air puff. These results support findings that associate TCF4 dysfunction with cognitive inflexibility and improper filtering of sensory stimuli observed in SZ patients.

VRK2 gene expression in schizophrenia, bipolar disorder and healthy controls

BACKGROUND

Common variants in the Vaccinia-related kinase 2 (VRK2) gene have been associated with schizophrenia, but the relevance of its encoded protein VRK2 in the disorder remains unclear.

AIMS

To identify potential differences in VRK2 gene expression levels between schizophrenia, bipolar disorder, psychosis not otherwise specified (PNOS) and healthy controls.

METHOD

VRK2 mRNA level was measured in whole blood in 652 individuals (schizophrenia, n = 201; bipolar disorder, n = 167; PNOS, n = 61; healthy controls, n = 223), and compared across diagnostic categories and subcategories. Additionally, we analysed for association between 1566 VRK2 single nucleotide polymorphisms and mRNA levels.

RESULTS

We found lower VRK2 mRNA levels in schizophrenia compared with healthy controls (P<10(-12)), bipolar disorder (P<10(-12)) and PNOS (P = 0.0011), and lower levels in PNOS than in healthy controls (P = 0.0042) and bipolar disorder (P = 0.00026). Expression quantitative trait loci in close proximity to the transcription start site of the short isoforms of the VRK2 gene were identified.

CONCLUSIONS

Altered VRK2 gene expression seems specific for schizophrenia and PNOS, which is in accordance with findings from genome-wide association studies. These results suggest that reduced VRK2 mRNA levels are involved in the underlying mechanisms in schizophrenia spectrum disorders.

Common polygenic variation and risk for childhood-onset schizophrenia

Childhood-onset schizophrenia (COS) is a rare and severe form of the disorder, with more striking abnormalities with respect to prepsychotic developmental disorders and abnormities in the brain development compared with later-onset schizophrenia. We previously documented that COS patients, compared with their healthy siblings and with adult-onset patients (AOS), carry significantly more rare chromosomal copy number variations, spanning large genomic regions (>100 kb) (Ahn et al. 2014). Here, we interrogated the contribution of common polygenic variation to the genetic susceptibility for schizophrenia. We examined the association between a direct measure of genetic risk of schizophrenia in 130 COS probands and 103 healthy siblings. Using data from the schizophrenia and autism GWAS of the Psychiatric Genomic Consortia, we selected three risk-related sets of single nucleotide polymorphisms from which we conducted polygenic risk score comparisons for COS probands and their healthy siblings. COS probands had higher genetic risk scores of both schizophrenia and autism than their siblings (P<0.05). Given the small sample size, these findings suggest that COS patients have more salient genetic risk than do AOS.

TCF4 gene polymorphism is associated with cognition in patients with schizophrenia and healthy controls

BACKGROUND

Cognitive deficits have been identified as an important core feature of schizophrenia. Single nucleotide polymorphisms in the transcription factor 4 (TCF4) gene have been reported to be involved in the susceptibility to schizophrenia and be significantly related to cognitive deficits of schizophrenia and controls. This study examines whether the TCF4 rs2958182 polymorphism influences cognitive functions in chronic schizophrenia and controls.

METHODS

The presence of the TCF4 rs2958182 was determined in 976 patients and 420 controls using a case-control design. We assessed all the patients' psychopathology using the Positive and Negative Syndrome Scale (PANSS). Cognition was assessed in 777 patients and 399 controls by using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS).

RESULTS

There were marginally significant differences in the TCF4 rs2958182 allelic and genotypic distributions between patients and controls (χ2 = 3.48, p = 0.062 and χ2 = 0.036, p = 0.036, respectively). Cognitive test scores were significantly lower in patients than in controls on all scales (all p < 0.001) except for the visuospatial/constructional index (p > 0.05). There were significant genotype effects on delayed memory score (p = 0.013), the RBANS total score (p = 0.028) and language score (p = 0.034). Further analysis showed that the language score significantly differed according to the genotypic groups (A/A+T/A group versus T/T group) (p = 0.007) in patients but not in controls (p > 0.05), and the delayed memory score also significantly differed according to the genotypic groups (A/A+T/A group versus T/T group) (p = 0.021) in controls but not in patients (p > 0.05).

CONCLUSIONS

This study found that the A allele of the TCF4 rs2958182 polymorphism was the risk allele of schizophrenia, and was associated with lower cognitive performance in language in schizophrenia and delayed memory in controls. In contrast, the T allele of this polymorphism was found to be the schizophrenia risk allele in another study in Han Chinese people.

Investigation of the role of TCF4 rare sequence variants in schizophrenia

Transcription factor 4 (TCF4) is one of the most robust of all reported schizophrenia risk loci and is supported by several genetic and functional lines of evidence. While numerous studies have implicated common genetic variation at TCF4 in schizophrenia risk, the role of rare, small-sized variants at this locus-such as single nucleotide variants and short indels which are below the resolution of chip-based arrays requires further exploration. The aim of the present study was to investigate the association between rare TCF4 sequence variants and schizophrenia. Exon-targeted resequencing was performed in 190 German schizophrenia patients. Six rare variants at the coding exons and flanking sequences of the TCF4 gene were identified, including two missense variants and one splice site variant. These six variants were then pooled with nine additional rare variants identified in 379 European participants of the 1000 Genomes Project, and all 15 variants were genotyped in an independent German sample (n = 1,808 patients; n = 2,261 controls). These data were then analyzed using six statistical methods developed for the association analysis of rare variants. No significant association (P < 0.05) was found. However, the results from our association and power analyses suggest that further research into the possible involvement of rare TCF4 sequence variants in schizophrenia risk is warranted by the assessment of larger cohorts with higher statistical power to identify rare variant associations.

Kraepelin revisited: schizophrenia from degeneration to failed regeneration

One hundred years after its conceptual definition as 'Dementia Praecox' by Emil Kraepelin, schizophrenia is still a serious psychiatric illness that affects young adults and leads to disability in at least half of patients. The key treatment issue is partial or non-response, especially of negative symptoms. The illness is also associated with different degrees of cognitive dysfunction, particularly in verbal and working memory; the resulting functional impairment may lead to unemployment and an inability to maintain stable relationships. Patients' cognitive dysfunction led Kraepelin to the assumption that schizophrenia is a form of juvenile dementia caused by a degenerative process of the human brain. Postmortem studies and a plethora of imaging studies do not support the notion of a degenerative process, but such a process is supported by the recently published, largest genome-wide association study on schizophrenia. More than a 100 hits were described, converging on pathways that have a significant role in dopamine metabolism in immune modulation, calcium signalling and synaptic plasticity. This review suggests that research should focus on animal models based on risk genes like transcription factor 4 and study the effects of exposure to environmental stressors relevant for schizophrenia. The use of relevant end points like pre-pulse inhibition or cognitive dysfunction will allow us to gain an understanding of the molecular pathways in schizophrenia and consequently result in improved treatment options, especially for the disabling aspects of this illness.

What is the impact of genome-wide supported risk variants for schizophrenia and bipolar disorder on brain structure and function? A systematic review

The powerful genome-wide association studies (GWAS) revealed common mutations that increase susceptibility for schizophrenia (SZ) and bipolar disorder (BD), but the vast majority were not known to be functional or associated with these illnesses. To help fill this gap, their impact on human brain structure and function has been examined. We systematically discuss this output to facilitate its timely integration in the psychosis research field; and encourage reflection for future research. Irrespective of imaging modality, studies addressing the effect of SZ/BD GWAS risk genes (ANK3, CACNA1C, MHC, TCF4, NRGN, DGKH, PBRM1, NCAN and ZNF804A) were included. Most GWAS risk variations were reported to affect neuroimaging phenotypes implicated in SZ/BD: white-matter integrity (ANK3 and ZNF804A), volume (CACNA1C and ZNF804A) and density (ZNF804A); grey-matter (CACNA1C, NRGN, TCF4 and ZNF804A) and ventricular (TCF4) volume; cortical folding (NCAN) and thickness (ZNF804A); regional activation during executive tasks (ANK3, CACNA1C, DGKH, NRGN and ZNF804A) and functional connectivity during executive tasks (CACNA1C and ZNF804A), facial affect recognition (CACNA1C and ZNF804A) and theory-of-mind (ZNF804A); but inconsistencies and non-replications also exist. Further efforts such as standardizing reporting and exploring complementary designs, are warranted to test the reproducibility of these early findings.

Altered gene expression in schizophrenia: findings from transcriptional signatures in fibroblasts and blood

BACKGROUND

Whole-genome expression studies in the peripheral tissues of patients affected by schizophrenia (SCZ) can provide new insight into the molecular basis of the disorder and innovative biomarkers that may be of great utility in clinical practice. Recent evidence suggests that skin fibroblasts could represent a non-neural peripheral model useful for investigating molecular alterations in psychiatric disorders.

METHODS

A microarray expression study was conducted comparing skin fibroblast transcriptomic profiles from 20 SCZ patients and 20 controls. All genes strongly differentially expressed were validated by real-time quantitative PCR (RT-qPCR) in fibroblasts and analyzed in a sample of peripheral blood cell (PBC) RNA from patients (n = 25) and controls (n = 22). To evaluate the specificity for SCZ, alterations in gene expression were tested in additional samples of fibroblasts and PBCs RNA from Major Depressive Disorder (MDD) (n = 16; n = 21, respectively) and Bipolar Disorder (BD) patients (n = 15; n = 20, respectively).

RESULTS

Six genes (JUN, HIST2H2BE, FOSB, FOS, EGR1, TCF4) were significantly upregulated in SCZ compared to control fibroblasts. In blood, an increase in expression levels was confirmed only for EGR1, whereas JUN was downregulated; no significant differences were observed for the other genes. EGR1 upregulation was specific for SCZ compared to MDD and BD.

CONCLUSIONS

Our study reports the upregulation of JUN, HIST2H2BE, FOSB, FOS, EGR1 and TCF4 in the fibroblasts of SCZ patients. A significant alteration in EGR1 expression is also present in SCZ PBCs compared to controls and to MDD and BD patients, suggesting that this gene could be a specific biomarker helpful in the differential diagnosis of major psychoses.

Genetic underpinnings of white matter 'connectivity': heritability, risk, and heterogeneity in schizophrenia

Schizophrenia is a highly heritable disorder. Thus, the combination of genetics and brain imaging may be a useful strategy to investigate the effects of risk genes on anatomical connectivity, and for gene discovery, i.e. discovering the genetic correlates of white matter phenotypes. Following a database search, I review evidence for heritability of white matter phenotypes. I also review candidate gene investigations, examining association of putative risk variants with white matter phenotypes, as well as the recent flurry of research exploring relationships of genome-wide significant risk loci with white matter phenotypes. Finally, I review multivariate and polygene approaches, which constitute a new wave of imaging-genetics research, including large collaborative initiatives aiming to discover new genes that may predict aspects of white matter microstructure. The literature supports the heritability of white matter phenotypes. Loci in genes intimately implicated in oligodendrocyte and myelin development, growth and maintenance, and neurotrophic systems are associated with white matter microstructure. GWAS variants have not yet sufficiently been explored using DTI-based evaluation of white matter to draw conclusions, although micro-RNA 137 is promising due to its potential regulation of other GWAS schizophrenia genes. Many imaging-genetic studies only include healthy participants, which, while helping control for certain confounds, cannot address questions related to disease heterogeneity or symptom expression, and thus more studies should include participants with schizophrenia. With sufficiently large sample sizes, the future of this field lies in polygene strategies aimed at risk prediction and heterogeneity dissection of schizophrenia that can translate to personalized interventions.

Association study identifying a new susceptibility gene (AUTS2) for schizophrenia

Schizophrenia (SCZ) is a severe and debilitating mental disorder, and the specific genetic factors that underlie the risk for SCZ remain elusive. The autism susceptibility candidate 2 (AUTS2) gene has been reported to be associated with autism, suicide, alcohol consumption, and heroin dependence. We hypothesized that AUTS2 might be associated with SCZ. In the present study, three polymorphisms (rs6943555, rs7459368, and rs9886351) in the AUTS2 gene were genotyped in 410 patients with SCZ and 435 controls using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and forced PCR-RFLP methods. We detected an association between SCZ and the rs6943555 genotype distribution (odds ratio (OR)=1.363, 95% confidence interval (CI): 0.848-2.191, p=0.001). The association remained significant after adjusting for gender, and a significant effect (p=0.001) was observed among the females. In the present study, rs6943555 was determined to be associated with female SCZ. Our results confirm previous reports which have suggested that rs6943555 might elucidate the pathogenesis of schizophrenia and play an important role in its etiology.

Transcription factor 4 (TCF4) and schizophrenia: integrating the animal and the human perspective

Schizophrenia is a genetically complex disease considered to have a neurodevelopmental pathogenesis and defined by a broad spectrum of positive and negative symptoms as well as cognitive deficits. Recently, large genome-wide association studies have identified common alleles slightly increasing the risk for schizophrenia. Among the few schizophrenia-risk genes that have been consistently replicated is the basic Helix-Loop-Helix (bHLH) transcription factor 4 (TCF4). Haploinsufficiency of the TCF4 (formatting follows IUPAC nomenclature: TCF4 protein/protein function, Tcf4 rodent gene cDNA mRNA, TCF4 human gene cDNA mRNA) gene causes the Pitt-Hopkins syndrome-a neurodevelopmental disease characterized by severe mental retardation. Accordingly, Tcf4 null-mutant mice display developmental brain defects. TCF4-associated risk alleles are located in putative coding and non-coding regions of the gene. Hence, subtle changes at the level of gene expression might be relevant for the etiopathology of schizophrenia. Behavioural phenotypes obtained with a mouse model of slightly increased gene dosage and electrophysiological investigations with human risk-allele carriers revealed an overlapping spectrum of schizophrenia-relevant endophenotypes. Most prominently, early information processing and higher cognitive functions appear to be associated with TCF4 risk genotypes. Moreover, a recent human study unravelled gene × environment interactions between TCF4 risk alleles and smoking behaviour that were specifically associated with disrupted early information processing. Taken together, TCF4 is considered as an integrator ('hub') of several bHLH networks controlling critical steps of various developmental, and, possibly, plasticity-related transcriptional programs in the CNS and changes of TCF4 expression also appear to affect brain networks important for information processing. Consequently, these findings support the neurodevelopmental hypothesis of schizophrenia and provide a basis for identifying the underlying molecular mechanisms.