Replication of linkage on chromosome 7q22 and association of the regional Reelin gene with working memory in schizophrenia families

Role of Semaphorin 3A in common psychiatric illnesses such as schizophrenia, depression, and anxiety

With societal development and an ageing population, psychiatric disorders have become a common cause of severe and long-term disability and socioeconomic burdens worldwide. Semaphorin 3A (Sema-3A) is a secreted glycoprotein belonging to the semaphorin family. Sema-3A is well known as an axon guidance factor in the neuronal system and a potent immunoregulator at all stages of the immune response. It is reported to have various biological functions and is involved in many human diseases, including autoimmune diseases, angiocardiopathy, osteoporosis, and tumorigenesis. The signals of sema-3A involved in the pathogenesis of these conditions, are transduced through its cognate receptors and diverse downstream signalling pathways. An increasing number of studies show that sema-3A plays important roles in synaptic and dendritic development, which are closely associated with the pathophysiological mechanisms of psychiatric disorders, including schizophrenia, depression, and autism, suggesting the involvement of sema-3A in the pathogenesis of mental diseases. This indicates that mutations in sema-3A and alterations in its receptors and signalling may compromise neurodevelopment and predispose patients to these disorders. However, the role of sema-3A in psychiatric disorders, particularly in regulating neurodevelopment, remains elusive. In this review, we summarise the recent progress in understanding sema-3A in the pathogenesis of mental diseases and highlight sema-3A as a potential target for the prevention and treatment of these diseases.

Neurocognitive, Clinical and Reelin Activity in Rehabilitation Using Neurofeedback Therapy in Patients with Schizophrenia

Introduction: Reelin is a neuropeptide responsible for the migration and positioning of pyramidal neurons, interneurons, and Purkinje cells. In adulthood, it still supports neuroplasticity, especially dendritic spines formation and glutamatergic neurotransmission. Genetic studies have confirmed the involvement of reelin system failure in the etiopathogenesis of mental diseases, including schizophrenia. Given the role of reelin in brain cytoarchitectonics and the regularly observed reduction in its activity in prefrontal areas in cases of schizophrenia, dysfunction of the reelin pathway fits the neurodevelopmental hypothesis of schizophrenia, both as a biochemical predisposition and/or the ultimate trigger of psychosis and as a biosocial factor determining the clinical course, and finally, as a potential target for disease monitoring and treatment. Aim: The purpose of this study was to examine associations of the reelin blood level with clinical and neurocognitive parameters during an intensive, structured neurofeedback therapy of patients with schizophrenia. Methods: Thirty-seven male patients with paranoid schizophrenia were randomly divided into two groups: a group with 3-month neurofeedback as an add-on to ongoing antipsychotic treatment (NF, N18), and a control group with standard social support and antipsychotic treatment (CON, N19). The reelin serum concentration, clinical and neurocognitive tests were compared between the groups. Results: After 3-month trial (T2), the reelin serum level increased in the NF group vs. the CON group. The negative and general symptoms of PANSS (Positive and Negative Syndrome Scale) were reduced significantly more in the NF group at T2, and the d2 (d2 Sustained Attention Test) and BCIS (Beck Cognitive Insight Scale) scores improved only in the NF group. The AIS scores improved more dynamically in the NF group, but not enough to differentiate them from the CON group at T2. Conclusions: The clinical and neurocognitive improvement within the 3-month NF add-on therapy trial was associated with a significant increase of reelin serum level in schizophrenia patients.

Reelin Signaling and Synaptic Plasticity in Schizophrenia

Recent research emphasizes the significance of studying the quality of life of schizophrenia patients, considering the complex nature of the illness. Identifying neuronal markers for early diagnosis and treatment is crucial. Reelin (RELN) stands out among these markers, with genetic studies highlighting its role in mental health. Suppression of RELN expression may contribute to cognitive deficits by limiting dendritic proliferation, affecting neurogenesis, and leading to improper neuronal circuits. Although the physiological function of reelin is not fully understood, it plays a vital role in hippocampal cell stratification and neuroglia formation. This analysis explores reelin's importance in the nervous system, shedding light on its impact on mental disorders such as schizophrenia, paving the way for innovative therapeutic approaches, and at the same time, raises the following conclusions: increased methylation levels of the RELN gene in patients with a diagnosis of schizophrenia results in a multiple decrease in the expression of reelin, and monitoring of this indicator, i.e., methylation levels, can be used to monitor the severity of symptoms in the course of schizophrenia.

Glutamatergic dysfunction is associated with phenotypes of VGF-overexpressing mice

VGF nerve growth factor inducible (VGF) is a neuropeptide precursor, which is induced by several neurotrophic factors, including nerve growth factor and brain-derived neurotrophic factor. Clinically, an upregulation of VGF levels has been reported in the cerebrospinal fluid and prefrontal cortex of patients with schizophrenia. In our previous study, mice overexpressing VGF exhibited schizophrenia-related behaviors. In the current study, we characterized the biochemical changes in the brains of VGF-overexpressing mice. Metabolomics analysis of neurotransmitters revealed that glutamic acid and N-acetyl-L-aspartic acid were increased in the striatum of VGF-overexpressing mice. Additionally, the present study revealed that MK-801, which causes the disturbance in glutamic acid metabolism, increased the expression level of VGF-derived peptide (NAPP129, named VGF20), and VGF-overexpressing mice had higher sensitivity to MK-801. These results suggest that VGF may modulate the regulation of glutamic acid levels and the degree of glutamic acid signaling.

Working memory deficits in children with schizophrenia and its mechanism, susceptibility genes, and improvement: A literature review

The negative influence on the cognitive ability of schizophrenia is one of the issues widely discussed in recent years. Working memory deficits are thought to be a core cognitive symptom of schizophrenia and lead to poorer social functions and worse academic performance. Previous studies have confirmed that working memory deficits tend to appear in the prodromal phase of schizophrenia. Therefore, considering that children with schizophrenia have better brain plasticity, it is critical to explore the development of their working memory. Although the research in this field developed gradually in recent years, few researchers have summarized these findings. The current study aims to review the recent studies from both behavior and neuroimaging aspects to summarize the working memory deficits of children with schizophrenia and to discuss the pathogenic factors such as genetic susceptibility. In addition, this study put forward some practicable interventions to improve cognitive symptoms of schizophrenia from psychological and neural perspectives.

Revisiting tandem repeats in psychiatric disorders from perspectives of genetics, physiology, and brain evolution

Genome-wide association studies (GWASs) have revealed substantial genetic components comprised of single nucleotide polymorphisms (SNPs) in the heritable risk of psychiatric disorders. However, genetic risk factors not covered by GWAS also play pivotal roles in these illnesses. Tandem repeats, which are likely functional but frequently overlooked by GWAS, may account for an important proportion in the "missing heritability" of psychiatric disorders. Despite difficulties in characterizing and quantifying tandem repeats in the genome, studies have been carried out in an attempt to describe impact of tandem repeats on gene regulation and human phenotypes. In this review, we have introduced recent research progress regarding the genomic distribution and regulatory mechanisms of tandem repeats. We have also summarized the current knowledge of the genetic architecture and biological underpinnings of psychiatric disorders brought by studies of tandem repeats. These findings suggest that tandem repeats, in candidate psychiatric risk genes or in different levels of linkage disequilibrium (LD) with psychiatric GWAS SNPs and haplotypes, may modulate biological phenotypes related to psychiatric disorders (e.g., cognitive function and brain physiology) through regulating alternative splicing, promoter activity, enhancer activity and so on. In addition, many tandem repeats undergo tight natural selection in the human lineage, and likely exert crucial roles in human brain evolution. Taken together, the putative roles of tandem repeats in the pathogenesis of psychiatric disorders is strongly implicated, and using examples from previous literatures, we wish to call for further attention to tandem repeats in the post-GWAS era of psychiatric disorders.

Variants in regulatory elements of PDE4D associate with major mental illness in the Finnish population

We have previously reported a replicable association between variants at the PDE4D gene and familial schizophrenia in a Finnish cohort. In order to identify the potential functional mutations underlying these previous findings, we sequenced 1.5 Mb of the PDE4D genomic locus in 20 families (consisting of 96 individuals and 79 independent chromosomes), followed by two stages of genotyping across 6668 individuals from multiple Finnish cohorts for major mental illnesses. We identified 4570 SNPs across the PDE4D gene, with 380 associated to schizophrenia (p ≤ 0.05). Importantly, two of these variants, rs35278 and rs165940, are located at transcription factor-binding sites, and displayed replicable association in the two-stage enlargement of the familial schizophrenia cohort (combined statistics for rs35278 p = 0.0012; OR = 1.18, 95% CI: 1.06-1.32; and rs165940 p = 0.0016; OR = 1.27, 95% CI: 1.13-1.41). Further analysis using additional cohorts and endophenotypes revealed that rs165940 principally associates within the psychosis (p = 0.025, OR = 1.18, 95% CI: 1.07-1.30) and cognitive domains of major mental illnesses (g-score p = 0.044, β = -0.033). Specifically, the cognitive domains represented verbal learning and memory (p = 0.0091, β = -0.044) and verbal working memory (p = 0.0062, β = -0.036). Moreover, expression data from the GTEx database demonstrated that rs165940 significantly correlates with the mRNA expression levels of PDE4D in the cerebellum (p-value = 0.04; m-value = 0.9), demonstrating a potential functional consequence for this variant. Thus, rs165940 represents the most likely functional variant for major mental illness at the PDE4D locus in the Finnish population, increasing risk broadly to psychotic disorders.

Exploring the mRNA expression level of RELN in peripheral blood of schizophrenia patients before and after antipsychotic treatment

Background

The Reelin (RELN) gene encodes the protein reelin, which is a large extracellular matrix glycoprotein that plays a key role in brain development. Additionally, this protein may be involved in memory formation, neurotransmission, and synaptic plasticity, which have been shown to be disrupted in schizophrenia (SCZ). A decreasing trend in the expression of RELN mRNA in the brain and peripheral blood of SCZ patients has been observed. There is a need to determine whether changes in RELN mRNA expression in SCZ patients are the result of long-term antipsychotic treatment rather than the etiological characteristics of schizophrenia. The expression levels of RELN mRNA in the peripheral blood of 48 healthy controls and 30 SCZ patients before and after 12-weeks of treatment were measured using quantitative real-time PCR.

Results

The expression levels of RELN mRNA in the SCZ group were significantly lower than that of healthy controls; however, after 12-weeks of antipsychotic treatment, RELN mRNA levels were significantly increased in the SCZ group.

Conclusion

The up-regulation of RELN mRNA expression was current in SCZ patients after antipsychotic treatment, suggesting that the changes in RELN mRNA expression were related to the effect of the antipsychotic treatment.

Further evidence for the association between LRP8 and schizophrenia

Previous studies (including genome-wide association study (GWAS) and candidate gene studies) have revealed the important roles of genetic risk factors in schizophrenia, and RELN has been identified as a risk gene for this illness. We recently found that the low-density lipoprotein receptor-related protein 8 (LRP8), a receptor of Reelin (the protein encoded by RELN), was significantly associated with schizophrenia and bipolar disorder in European populations. To further enhance our understanding of its role in the risk of psychiatric illnesses, we conducted meta-analyses of a higher density of single nucleotide polymorphisms (SNPs, N=173) in LRP8 to understand their associations with schizophrenia in much larger samples (39,400 cases and 50,357 controls) from populations of European, Chinese and African American ancestries. The significant risk SNPs then underwent further analyses to understand their correlations with bipolar disorder and anxiety disorders, as well as LRP8 expression. We observed that rs5177 in the 3' untranslated region (3'UTR) of LRP8 was associated with schizophrenia and other psychiatric disorders, and rs5177 was also associated with LRP8 mRNA expression. These data further support LRP8 as a schizophrenia susceptibility gene, and suggest that this variant is likely a risk locus in general populations.

Disruptive mutations in TANC2 define a neurodevelopmental syndrome associated with psychiatric disorders

Postsynaptic density (PSD) proteins have been implicated in the pathophysiology of neurodevelopmental and psychiatric disorders. Here, we present detailed clinical and genetic data for 20 patients with likely gene-disrupting mutations in TANC2-whose protein product interacts with multiple PSD proteins. Pediatric patients with disruptive mutations present with autism, intellectual disability, and delayed language and motor development. In addition to a variable degree of epilepsy and facial dysmorphism, we observe a pattern of more complex psychiatric dysfunction or behavioral problems in adult probands or carrier parents. Although this observation requires replication to establish statistical significance, it also suggests that mutations in this gene are associated with a variety of neuropsychiatric disorders consistent with its postsynaptic function. We find that TANC2 is expressed broadly in the human developing brain, especially in excitatory neurons and glial cells, but shows a more restricted pattern in Drosophila glial cells where its disruption affects behavioral outcomes.

VGF has Roles in the Pathogenesis of Major Depressive Disorder and Schizophrenia: Evidence from Transgenic Mouse Models

Mental disorders, such as major depressive disorder and schizophrenia, are complex multigenetic conditions, but focused studies of single genes might reveal genes involved in the pathogenesis of mental disorders, including major depressive disorder and schizophrenia. Several candidate genes have been identified using transgenic mice. VGF nerve growth factor inducible (VGF) is a neuropeptide expression of which is induced by nerve growth factor (NGF). VGF is robustly and exclusively synthesized in neuronal and neuroendocrine cells. In central nervous system (CNS), VGF is extensively expressed especially in the cerebral cortex, hippocampus, and hypothalamus. VGF has many roles in the CNS, such as promotion of synaptic plasticity, neurogenesis, and neurite outgrowth. In clinical studies, altered expression and genetic mutations of VGF have been reported in patients with major depressive disorder and schizophrenia. On this basis, studies using transgenic mice to overexpress or knockout VGF have been performed to investigate the roles of upregulation or downregulation of VGF. In this review, we will discuss studies of the roles of VGF using transgenic mice and its relevance to pathologies in major depressive disorder and schizophrenia.

The genomics of schizophrenia: Shortcomings and solutions

Due to recent advances in human genomic technologies, there have been explosive interests and extensive research on the genomics of schizophrenia, a severe psychiatric disorder characterized by social cognitive deficits, hallucinations, and delusions. These new technologies, including next-generation sequencing (NGS), genome-wide association studies (GWAS), and the Clustered Regularly Interspaced Short Palindromic Repeats-associated nuclease 9 (CRISPR/Cas9) genome editing platform are capable of interrogating and editing the genome directly. In the past few years, these efforts have led to the identification of important loci and genes susceptible to schizophrenia. The findings have increased our understanding of the underlying genetic causes of schizophrenia and aided in the development of new approaches for more effectively diagnosing and treating schizophrenia. Despite the substantial progress, there are several unanswered questions about the genomics of schizophrenia, and there are a number of potential shortcomings in the current literature considering the complexity of the disease and limits of the current technologies. In the present review, we assessed the existing literature on the genomics of schizophrenia, identifying the strengths and study design shortcomings from the following aspects: elucidation of the pathogenesis, early risk prediction and diagnosis, and the treatment of schizophrenia. Moreover, we have proposed solutions to overcome the shortcomings of past studies. Lastly, we have discussed the importance of developing multidisciplinary teams and global research groups in order to improve the lives of schizophrenic patients globally.

Female gender specific association of the Reelin (RELN) gene rs7341475 variant with schizophrenia

RELN gene encodes a large extracellular matrix protein which is critical for neuronal migration, cell positioning and cell-cell interactions. It also controls the synaptic plasticity of neurons for initiation and maintenance of long term potentiation. The aim of this study is to investigate the association of RELN rs7341475 variant with schizophrenia. Genomic DNA isolation was performed from 105 schizophrenic patients and 137 healthy controls to determine RELN rs7341475 genotypes. Genotype and allele frequencies were determined by a polymerase chain reaction-restriction fragment length polymorphism method developed in our laboratory. Statistical analysis was performed using χ² test. The frequencies for G allele were 79.5% in cases and 81.0% in controls, for A allele 20.5% in cases and 19.0% in controls in the overall population. The genotype frequencies of the RELN gene rs7341475 variant were GG; 63.8%, GA; 31.4% and AA; 4.8% in cases, GG; 63.5%, GA; 35.0% and AA; 1.5% in controls in the overall population. There was no statistically significant association between the rs7341475 variant of RELN gene and schizophrenia in the overall population (χ² = 2.473, p = 0.290). In the gender specific analysis, female gender specific association was only found. The RELN rs7341475 variant GG genotype was significantly associated with schizophrenia (p = 0.034, OR 2.760, 95% CI 1.058-7.197) and A allele was protective against schizophrenia (p = 0.034, OR 0.362, 95% CI 0.139-0.945). All cases and controls were in Hardy-Weinberg equilibrium (p > 0.05). Population size can be increased to improve the statistical power. Moreover, other RELN gene variants which are especially involved in neuronal migration and epigenetic regulation may be analyzed for revealing the complex genetic architecture of schizophrenia. In conclusion, there was only association between the RELN rs7341475 variant and schizophrenia in the female gender in a Turkish population.

Gene expression changes related to immune processes associate with cognitive endophenotypes of schizophrenia

Schizophrenia is a heterogeneous disorder characterized by a spectrum of symptoms and many different underlying causes. Thus, instead of using the broad diagnosis, intermediate phenotypes can be used to possibly decrease the underlying complexity of the disorder. Alongside the classical symptoms of delusions and hallucinations, cognitive deficits are a core feature of schizophrenia. To increase our understanding of the biological processes related to these cognitive deficits, we performed a genome-wide gene expression analysis. A battery of 14 neuropsychological tests was administered to 844 individuals from a Finnish familial schizophrenia cohort. We grouped the applied neuropsychological tests into five factors for further analysis. Cognitive endophenotypes, whole blood mRNA, genotype, and medication use data were studied from 47 individuals. Expression level of several RNA probes were significantly associated with cognitive performance. The factor representing Verbal Working Memory was associated with altered expression levels of 11 probes, of which one probe was also associated with a specific sub-measure of this factor (WMS-R Digit span backward). While, the factor Processing speed was related to one probe, which additionally associated among 55 probes with a specific sub-measure of this factor (WAIS-R Digit symbol). Two probes were associated with the measure recognition memory performance. Enrichment analysis of these differentially expressed probes highlighted immunological processes. Our findings are in line with genome-wide genetic discoveries made in schizophrenia, suggesting that immunological processes may be of biological interest for future drug design towards schizophrenia and the cognitive dysfunctions that underlie it.

SNP Variation of RELN Gene and Schizophrenia in a Chinese Population: A Hospital-Based Case-Control Study

Aims: We aimed to explore whether RELN contributes to the vulnerability and severity of clinical symptoms of schizophrenia (SZ) in a Chinese population. Methods: The following were conducted in an adult Han Chinese population from southern China: case-control association analyses of 30 representative single nucleotide polymorphisms (SNPs) that were screened according to specific programs based on bioinformatics tools and former research and quantitative trait locus analyses with SNPs and psychiatric symptoms evaluated with the positive and negative symptoms scale. Results: A 4-SNP haplotype consisting of rs362814, rs39339, rs540058, and rs661575 was found to be significantly associated with SZ even after Bonferroni correction (χ² = 29.024, p = 6.42E-04, p _Bonf = 0.017), and the T-C-T-C haplotype was a protective factor for SZ (OR = 0.050, 95% CI = 0.004-0.705). Moreover, the 4-SNP haplotype showed a significant association with G16 (active social avoidance) after false discovery rate correction (χ² = 28.620, p = 1.697E-04, p _FDR = 0.025). In addition, P7 (hostility) was related to the haplotype comprising rs2229864, rs2535764, and rs262355 (χ² = 31.424, p = 2.103E-05, p _adjustment = 0.019) in quantitative trait loci analyses. Conclusion: Overall, this study showed several positive associations between RELN and SZ, as well as psychiatric symptoms, which not only supports the proposition that RELN is a susceptibility gene for SZ but also provides information on a genotype-phenotype correlation for SZ in a Chinese population.

VRK2, a Candidate Gene for Psychiatric and Neurological Disorders

Recent large-scale genetic approaches, such as genome-wide association studies, have identified multiple genetic variations that contribute to the risk of mental illnesses, among which single nucleotide polymorphisms (SNPs) within or near the vaccinia related kinase 2 (VRK2) gene have gained consistent support for their correlations with multiple psychiatric and neurological disorders including schizophrenia (SCZ), major depressive disorder (MDD), and genetic generalized epilepsy. For instance, the genetic variant rs1518395 in VRK2 showed genome-wide significant associations with SCZ (35,476 cases and 46,839 controls, p = 3.43 × 10-8) and MDD (130,620 cases and 347,620 controls, p = 4.32 × 10-12) in European populations. This SNP was also genome-wide significantly associated with SCZ in Han Chinese population (12,083 cases and 24,097 controls, p = 3.78 × 10-13), and all associations were in the same direction of allelic effects. These studies highlight the potential roles of VRK2 in the central nervous system, and this gene therefore might be a good candidate to investigate the shared genetic and molecular basis between SCZ and MDD, as it is one of the few genes known to show genome-wide significant associations with both illnesses. Furthermore, the VRK2 gene was found to be involved in multiple other congenital deficits related to the malfunction of neurodevelopment, adding further support for the involvement of this gene in the pathogenesis of these neurological and psychiatric illnesses. While the precise function of VRK2 in these conditions remains unclear, preliminary evidence suggests that it may affect neuronal proliferation and migration via interacting with multiple essential signaling pathways involving other susceptibility genes/proteins for psychiatric disorders. Here, we have reviewed the recent progress of genetic and molecular studies of VRK2, with an emphasis on its role in psychiatric illnesses and neurological functions. We believe that attention to this important gene is necessary, and further investigations of VRK2 may provide hints into the underlying mechanisms of SCZ and MDD.

[Relationships of rs7341475 polymorphism and DNA methylation in the reelin gene with schizophrenia symptoms]

AIM

To study the role of polymorphism rs7341475 and methylation of the reelin gene in symptoms of schizophrenia and semantic verbal fluency.

MATERIAL AND METHODS

Genotypes at the locus rs7341475 were identified in 556 patients with schizophrenic disorders. PANSS scores were obtained for 549 patients and 221 patients performed a test for semantic verbal fluency. The association of the reelin promoter methylation with the PANSS and verbal fluency measures was evaluated in 35 patients. A five-factor model of the PANSS was used.

RESULTS

The interaction effect of sex with genotype on the PANSS scores was found (F=2.70, p=0.020). Schizophrenic men homozygous for a common allele G had the lowest scores of the positive syndrome. Verbal fluency was related to the reelin promoter methylation.

CONCLUSION

The results suggest that polymorphism rs7341475 may be associated with the variability of positive symptomatology in schizophrenic men. At the same time, the reelin gene methylation pattern, which consists of a higher methylation level in the region of the transcription start site and a lower one in the distal region of the promoter, may be beneficial for verbal fluency.

Reelin Haploinsufficiency and Late-Adolescent Corticosterone Treatment Induce Long-Lasting and Female-Specific Molecular Changes in the Dorsal Hippocampus

Reelin depletion and stress seem to affect similar pathways including GABAergic and glutamatergic signaling and both are implicated in psychiatric disorders in late adolescence/early adulthood. The interaction between reelin depletion and stress, however, remains unclear. To investigate this, male and female heterozygous reelin mice (HRM) and wildtype (WT) controls were treated with the stress hormone, corticosterone (CORT), during late adolescence to simulate chronic stress. Glucocorticoid receptors (GR), N-methyl-d-aspartate receptor (NMDAr) subunits, glutamic acid decarboxylase (GAD₆₇) and parvalbumin (PV) were measured in the hippocampus and the prefrontal cortex (PFC) in adulthood. While no changes were seen in male mice, female HRM showed a significant reduction in GR expression in the dorsal hippocampus. In addition, CORT reduced GR levels as well as GluN2B and GluN2C subunits of NMDAr in the dorsal hippocampus in female mice only. CORT furthermore reduced GluN1 levels in the PFC of female mice. The combined effect of HRM and CORT treatment appeared to be additive in terms of GR expression in the dorsal hippocampus. Female-specific CORT-induced changes were associated with overall higher circulating CORT levels in female compared to male mice. This study shows differential effects of reelin depletion and CORT treatment on GR and NMDAr protein expression in male and female mice, suggesting that females are more susceptible to reelin haploinsufficiency as well as late-adolescent stress. These findings shed more light on female-specific vulnerability to stress and have implications for stress-associated mental illnesses with a female bias including anxiety and major depression.

The NDE1 genomic locus can affect treatment of psychiatric illness through gene expression changes related to microRNA-484

Genetic studies of familial schizophrenia in Finland have observed significant associations with a group of biologically related genes, DISC1, NDE1, NDEL1, PDE4B and PDE4D, the ‘DISC1 network’. Here, we use gene expression and psychoactive medication use data to study their biological consequences and potential treatment implications. Gene expression levels were determined in 64 individuals from 18 families, while prescription medication information has been collected over a 10-year period for 931 affected individuals. We demonstrate that the NDE1 SNP rs2242549 associates with significant changes in gene expression for 2908 probes (2542 genes), of which 794 probes (719 genes) were replicable. A significant number of the genes altered were predicted targets of microRNA-484 (p = 3.0 × 10⁻⁸), located on a non-coding exon of NDE1. Variants within the NDE1 locus also displayed significant genotype by gender interaction to early cessation of psychoactive medications metabolized by CYP2C19. Furthermore, we demonstrate that miR-484 can affect the expression of CYP2C19 in a cell culture system. Thus, variation at the NDE1 locus may alter risk of mental illness, in part through modification of miR-484, and such modification alters treatment response to specific psychoactive medications, leading to the potential for use of this locus in targeting treatment.

Dorsal Forebrain-Specific Deficiency of Reelin-Dab1 Signal Causes Behavioral Abnormalities Related to Psychiatric Disorders

Reelin-Dab1 signaling is involved in brain development and neuronal functions. The abnormalities in the signaling through either reduction of Reelin and Dab1 gene expressions or the genomic mutations in the brain have been reported to be associated with psychiatric disorders. However, it has not been clear if the deficiency in Reelin-Dab1 signaling is responsible for symptoms of the disorders. Here, to examine the function of Reelin-Dab1 signaling in the forebrain, we generated dorsal forebrain-specific Dab1 conditional knockout mouse (Dab1 cKO) and performed a behavioral test battery on the Dab1 cKO mice. Although conventional Dab1 null mutant mice exhibit cerebellar atrophy and cerebellar ataxia, the Dab1 cKO mice had normal cerebellum and showed no motor dysfunction. Dab1 cKO mice exhibited behavioral abnormalities, including hyperactivity, decreased anxiety-like behavior, and impairment of working memory, which are reminiscent of symptoms observed in patients with psychiatric disorders such as schizophrenia and bipolar disorder. These results suggest that deficiency of Reelin-Dab1 signal in the dorsal forebrain is involved in the pathogenesis of some symptoms of human psychiatric disorders.

The Candidate Schizophrenia Risk Gene DGCR2 Regulates Early Steps of Corticogenesis

BACKGROUND

Alterations in early steps of cortical circuit assembly are thought to play a critical role in vulnerability to schizophrenia (SZ), but the pathogenic impact of SZ-risk mutations on corticogenesis remains to be determined. DiGeorge syndrome critical region 2 (DGCR2) is located in the 22q11.2 locus, whose deletion is a major risk factor for SZ. Moreover, exome sequencing of individuals with idiopathic SZ identified a rare missense mutation in DGCR2, further suggesting that DGCR2 is involved in SZ.

METHODS

Here we investigated the function of Dgcr2 and the pathogenic impact of the SZ-risk DGCR2 mutation in mouse corticogenesis using in utero electroporation targeted to projection neurons.

RESULTS

Dgcr2 knockdown impaired radial locomotion and final translocation of projection neurons, leading to persistent laminar positioning alterations. The DGCR2 missense SZ-risk mutation had a pathogenic impact on projection neuron laminar allocation by reducing protein expression. Mechanistically, we identified Dgcr2 as a novel member of the Reelin complex, regulating the phosphorylation of Reelin-dependent substrates and the expression of Reelin-dependent transcriptional targets.

CONCLUSIONS

Overall, this study provides biological evidence that the SZ-risk gene DGCR2 regulates critical steps of early corticogenesis possibly through a Reelin-dependent mechanism. Additionally, we found that the SZ-risk mutation in DGCR2 has a pathogenic impact on cortical formation by reducing protein expression level, suggesting a functional role for DGCR2 haploinsufficiency in the 22q11.2 deletion syndrome.

Sensorimotor gating deficits and effects of antipsychotics on the hyperactivity in VGF-overexpressing mice

BACKGROUND

VGF nerve growth factor inducible (VGF) is a neuropeptide which is expressed in neuronal cells and endocrine cells. VGF is induced by several neurotrophic factors. The expression level of VGF in patients with schizophrenia is increased in cerebrospinal fluid (CSF) and prefrontal cortex. In our previous study, we generated mice in which the expression level of VGF in the brain was increased. VGF-overexpressing mice exhibited abnormal behaviors including hyperactivity. However, it remains unknown whether VGF-overexpressing mice exhibit the endophenotype of schizophrenia and whether abnormal behaviors in these mice can be improved by antipsychotics.

METHODS

In the present study, we investigated schizophrenia-like behaviors and the responsiveness to antipsychotics in transgenic mice.

RESULTS

VGF-overexpressing mice (1) exhibited prepulse inhibition (PPI) impairment, (2) showed normalized hyperactivity following antipsychotic drug treatment, and (3) showed abnormal responsiveness to haloperidol.

CONCLUSION

Upregulation of VGF may be implicated in the pathophysiology of schizophrenia and abnormalities of dopaminergic signaling.

A genome-wide screen for acrophobia susceptibility loci in a Finnish isolate

Acrophobia, an abnormal fear of heights, is a specific phobia characterized as apprehension cued by the occurrence or anticipation of elevated spaces. It is considered a complex trait with onset influenced by both genetic and environmental factors. Identification of genetic risk variants would provide novel insight into the genetic basis of the fear of heights phenotype and contribute to the molecular-level understanding of its aetiology. Genetic isolates may facilitate identification of susceptibility alleles due to reduced genetic heterogeneity. We took advantage of an internal genetic isolate in Finland in which a distinct acrophobia phenotype appears to be segregating in pedigrees originally ascertained for schizophrenia. We conducted parametric, nonparametric, joint linkage and linkage disequilibrium analyses using a microsatellite marker panel, genotyped in families to search for chromosomal regions correlated with acrophobia. Our results implicated a few regions with suggestive evidence for linkage on chromosomes 4q28 (LOD = 2.17), 8q24 (LOD = 2.09) and 13q21-q22 (LOD = 2.22). We observed no risk haplotypes shared between different families. These results suggest that genetic predisposition to acrophobia in this genetic isolate is unlikely to be mediated by a small number of shared high-risk alleles, but rather has a complex genetic architecture.

Reelin and Neuropsychiatric Disorders

Proper neuronal migration and laminar formation during corticogenesis is essential for normal brain function. Disruption of these developmental processes is thought to be involved in the pathogenesis of some neuropsychiatric conditions. Especially, Reelin, a glycoprotein mainly secreted by the Cajal-Retzius cells and a subpopulation of GABAergic interneurons, has been shown to play a critical role, both during embryonic and postnatal periods. Indeed, animal studies have clearly revealed that Reelin is an essential molecule for proper migration of cortical neurons and finally regulates the cell positioning in the cortex during embryonic and early postnatal stages; by contrast, Reelin signaling is closely involved in synaptic function in adulthood. In humans, genetic studies have shown that the reelin gene (RELN) is associated with a number of psychiatric diseases, including Schizophrenia (SZ), bipolar disorder (BP) and autistic spectrum disorder. Indeed, Reln haploinsufficiency has been shown to cause cognitive impairment in rodents, suggesting the expression level of the Reelin protein is closely related to the higher brain functions. However, the molecular abnormalities in the Reelin pathway involved in the pathogenesis of psychiatric disorders are not yet fully understood. In this article, we review the current progress in the understanding of the Reelin functions that could be related to the pathogenesis of psychiatric disorders. Furthermore, we discuss the basis for selecting Reelin and molecules in its downstream signaling pathway as potential therapeutic targets for psychiatric illnesses.

Mice that lack the C-terminal region of Reelin exhibit behavioral abnormalities related to neuropsychiatric disorders

The secreted glycoprotein Reelin is believed to play critical roles in the pathogenesis of several neuropsychiatric disorders. The highly basic C-terminal region (CTR) of Reelin is necessary for efficient activation of its downstream signaling, and the brain structure of knock-in mice that lack the CTR (ΔC-KI mice) is impaired. Here, we performed a comprehensive behavioral test battery on ΔC-KI mice, in order to evaluate the effects of partial loss-of-function of Reelin on brain functions. The ΔC-KI mice were hyperactive and exhibited reduced anxiety-like and social behaviors. The working memory in ΔC-KI mice was impaired in a T-maze test. There was little difference in spatial reference memory, depression-like behavior, prepulse inhibition, or fear memory between ΔC-KI and wild-type mice. These results suggest that CTR-dependent Reelin functions are required for some specific normal brain functions and that ΔC-KI mice recapitulate some aspects of neuropsychiatric disorders, such as schizophrenia, bipolar disorder, and autism spectrum disorder.

Structural Insights into Reelin Function: Present and Future

Reelin is a neuronal glycoprotein secreted by the Cajal-Retzius cells in marginal regions of the cerebral cortex and the hippocampus where it plays important roles in the control of neuronal migration and the formation of cellular layers during brain development. This 3461 residue-long protein is composed of a signal peptide, an F-spondin-like domain, eight Reelin repeats (RR1-8), and a positively charged sequence at the C-terminus. Biochemical data indicate that the central region of Reelin binds to the low-density lipoprotein receptors apolipoprotein E receptor 2 (ApoER2) and the very-low-density lipoprotein receptor (VLDLR), leading to the phosphorylation of the intracellular adaptor protein Dab1. After secretion, Reelin is rapidly degraded in three major fragments, but the functional significance of this degradation is poorly understood. Probably due to its large mass and the complexity of its architecture, the high-resolution, three-dimensional structure of Reelin has never been determined. However, the crystal structures of some of the RRs have been solved, providing important insights into their fold and the interaction with the ApoER2 receptor. This review discusses the current findings on the structure of Reelin and its binding to the ApoER2 and VLDLR receptors, and we discuss some areas where proteomics and structural biology can help understanding Reelin function in brain development and human health.

Comprehensive behavioral phenotyping of a new Semaphorin 3 F mutant mouse

BACKGROUND

Semaphorin 3 F (Sema3F) is a secreted type of the Semaphorin family of axon guidance molecules. Sema3F and its receptor neuropilin-2 (Npn-2) are expressed in a mutually exclusive manner in the embryonic mouse brain regions including olfactory bulb, hippocampus, and cerebral cortex. Sema3F is thought to have physiological functions in the formation of neuronal circuitry and its refinement. However, functional roles of Sema3F in the brain remain to be clarified. Here, we examined behavioral effects of Sema3F deficiency through a comprehensive behavioral test battery in Sema3F knockout (KO) male mice to understand the possible functions of Sema3F in the brain.

RESULTS

Male Sema3F KO and wild-type (WT) control mice were subjected to a battery of behavioral tests, including neurological screen, rotarod, hot plate, prepulse inhibition, light/dark transition, open field, elevated plus maze, social interaction, Porsolt forced swim, tail suspension, Barnes maze, and fear conditioning tests. In the open field test, Sema3F KO mice traveled shorter distance and spent less time in the center of the field than WT controls during the early testing period. In the light/dark transition test, Sema3F KO mice also exhibited decreased distance traveled, fewer number of transitions, and longer latency to enter the light chamber compared with WT mice. In addition, Sema3F KO mice traveled shorter distance than WT mice in the elevated plus maze test, although there were no differences between genotypes in open arm entries and time spent in open arms. Similarly, Sema3F KO mice showed decreased distance traveled in the social interaction test. Sema3F KO mice displayed reduced immobility in the Porsolt forced swim test whereas there was no difference in immobility between genotypes in the tail suspension test. In the fear conditioning test, Sema3F KO mice exhibited increased freezing behavior when exposed to a conditioning context and an altered context in absence of a conditioned stimulus. In the tests for assessing motor function, pain sensitivity, startle response to an acoustic stimulus, sensorimotor gating, or spatial reference memory, there were no significant behavioral differences between Sema3F KO and WT mice.

CONCLUSIONS

These results suggest that Sema3F deficiency induces decreased locomotor activity and possibly abnormal anxiety-related behaviors and also enhances contextual memory and generalized fear in mice. Thus, our findings suggest that Sema3F plays important roles in the development of neuronal circuitry underlying the regulation of some aspects of anxiety and fear responses.

Working memory genetics in schizophrenia and related disorders: An RDoC perspective

Improved classification of mental disorders through neurobiological measures will require a set of traits that map to transdiagnostic subgroups of patients and align with heritable, core psychopathological processes at the center of the disorders of interest. A promising candidate is working memory (WM) function, for which deficits have been reported across multiple diagnostic entities including schizophrenia, bipolar disorder, ADHD, autism, and major depressive disorder. Here we review genetic working memory associations and their brain functional correlates from the perspective of identifying patient subgroups across conventional diagnostic boundaries, explore the utility of multimodal investigations integrating functional information at the neural systems level and explore potential limitations as well as future directions for research.

Convergent Lines of Evidence Support LRP8 as a Susceptibility Gene for Psychosis

Reelin (RELN) is identified as a risk gene for major psychiatric disorders such as schizophrenia (SCZ) and bipolar disorder (BPD). However, the role of its downstream signaling molecule, the low-density lipoprotein receptor-related protein 8 (LRP8) in these illnesses is still unclear. To detect whether LRP8 is a susceptibility gene for SCZ and BPD, we analyzed the associations of single nucleotide polymorphisms (SNPs) in LRP8 in a total of 47,187 subjects (including 9379 SCZ patients; 6990 BPD patients; and 12,556 controls in a screening sample, and 1397 SCZ families, 3947 BPD patients, and 8387 controls in independent replications), and identified a non-synonymous SNP rs5174 in LRP8 significantly associated with SCZ and BPD as well as the combined psychosis phenotype (P _meta = 1.99 × 10^-5, odds ratio (OR) = 1.066, 95 % confidence interval (CI) = 1.035-1.098). The risk SNP rs5174 was also associated with LRP8 messenger RNA (mRNA) expression in multiple brain tissues across independent samples (lowest P = 0.00005). Further exploratory analysis revealed that LRP8 was preferentially expressed in fetal brain tissues. Protein-protein interaction (PPI) analysis demonstrated that LRP8 significantly participated in a highly interconnected PPI network build by top risk genes for SCZ and BPD (P = 7.0 × 10^-4). Collectively, we confirmed that LRP8 is a risk gene for psychosis, and our results provide useful information toward a better understanding of genetic mechanism involving LRP8 underlying risk of complex psychiatric disorders.

Reelin influences the expression and function of dopamine D2 and serotonin 5-HT2A receptors: a comparative study

Reelin is an extracellular matrix protein that plays a critical role in neuronal guidance during brain neurodevelopment and in synaptic plasticity in adults and has been associated with schizophrenia. Reelin mRNA and protein levels are reduced in various structures of post-mortem schizophrenic brains, in a similar way to those found in heterozygous reeler mice (HRM). Reelin is involved in protein expression in dendritic spines that are the major location where synaptic connections are established. Thus, we hypothesized that a genetic deficit in reelin would affect the expression and function of dopamine D2 and serotonin 5-HT2A receptors that are associated with the action of current antipsychotic drugs. In this study, D2 and 5-HT2A receptor expression and function were quantitated by using radioligand binding studies in the frontal cortex and striatum of HRM and wild-type mice (WTM). We observed increased expression (p<0.05) in striatum membranes and decreased expression (p<0.05) in frontal cortex membranes for both dopamine D2 and serotonin 5-HT2A receptors from HRM compared to WTM. Our results show parallel alterations of D2 and 5-HT2A receptors that are compatible with a possible hetero-oligomeric nature of these receptors. These changes are similar to changes described in schizophrenic patients and provide further support for the suitability of using HRM as a model for studying this disease and the effects of antipsychotic drugs.

Guided exploration of genomic risk for gray matter abnormalities in schizophrenia using parallel independent component analysis with reference

One application of imaging genomics is to explore genetic variants associated with brain structure and function, presenting a new means of mapping genetic influences on mental disorders. While there is growing interest in performing genome-wide searches for determinants, it remains challenging to identify genetic factors of small effect size, especially in limited sample sizes. In an attempt to address this issue, we propose to take advantage of a priori knowledge, specifically to extend parallel independent component analysis (pICA) to incorporate a reference (pICA-R), aiming to better reveal relationships between hidden factors of a particular attribute. The new approach was first evaluated on simulated data for its performance under different configurations of effect size and dimensionality. Then pICA-R was applied to a 300-participant (140 schizophrenia (SZ) patients versus 160 healthy controls) dataset consisting of structural magnetic resonance imaging (sMRI) and single nucleotide polymorphism (SNP) data. Guided by a reference SNP set derived from ANK3, a gene implicated by the Psychiatric Genomic Consortium SZ study, pICA-R identified one pair of SNP and sMRI components with a significant loading correlation of 0.27 (p=1.64×10(-6)). The sMRI component showed a significant group difference in loading parameters between patients and controls (p=1.33×10(-15)), indicating SZ-related reduction in gray matter concentration in prefrontal and temporal regions. The linked SNP component also showed a group difference (p=0.04) and was predominantly contributed to by 1030 SNPs. The effect of these top contributing SNPs was verified using association test results of the Psychiatric Genomic Consortium SZ study, where the 1030 SNPs exhibited significant SZ enrichment compared to the whole genome. In addition, pathway analyses indicated the genetic component majorly relating to neurotransmitter and nervous system signaling pathways. Given the simulation and experiment results, pICA-R may prove a promising multivariate approach for use in imaging genomics to discover reliable genetic risk factors under a scenario of relatively high dimensionality and small effect size.

Impaired impulse control is associated with a 5-HT2A receptor polymorphism in schizophrenia

The impact of the serotonin2a (5-HT2A) receptor gene on the pathophysiology of schizophrenia is inconclusive despite accumulating evidence implicating the 5-HT2A receptor. To simplify the complexity of genetic analysis, we used an endophenotype approach. The relationship between Continuous Performance Test (CPT) performance and 5-HT2A receptor gene variance was examined. Both patients with schizophrenia (n=255) and healthy volunteers (n=380) were recruited. All were genotyped for the -1438A/G polymorphism and assessed with the CPT. The Positive and Negative Syndrome Scale and the Scale for the Assessment of Negative Symptoms were used to evaluate patients' clinical symptoms. The distribution of the 5-HT2A genotypes between patients and healthy controls was similar. Impulse control in schizophrenic patients, assessed with the false-alarm rate of the CPT, differed significantly between those with different 5-HT2A genotypes. We hypothesize that the 5-HT2A receptor gene is a modifier gene of schizophrenia and suggest that additional studies are warranted.

Does originating from a genetic isolate affect the level of cognitive impairments in schizophrenia families?

Earlier studies have detected differences in the prevalence, symptomatology and genetic risk variants of schizophrenia between a north-eastern Finnish genetic isolate and the rest of Finland. This study compared a population-based isolate sample (145 persons with schizophrenia, 304 first-degree relatives and 32 controls) with a rest of Finland sample (73 persons with schizophrenia, 100 first-degree relatives and 80 controls) in cognitive functioning. Persons from the isolate outperformed persons in the rest of Finland sample in verbal learning, verbal ability and cognitive flexibility in the schizophrenia groups and in verbal learning, speeded processing and attentional control in the relatives groups. The differences between the subsamples remained significant after taking into account an intragenic Reelin STR allele, previously associated with cognitive impairments and almost absent from the isolate, in addition to disorder characteristics and familial loading. In control groups, we observed no differences between the isolate and the rest of Finland. In conclusion, cognitive impairments were milder in schizophrenia patients and their first-degree relatives within than outside the isolate. An absence of differences between the control samples suggests that the differences in schizophrenia families may relate to genetic background, possibly to partly distinct variants affecting the liability inside and outside the isolate.

The involvement of Reelin in neurodevelopmental disorders

Reelin is a glycoprotein that serves important roles both during development (regulation of neuronal migration and brain lamination) and in adulthood (maintenance of synaptic function). A number of neuropsychiatric disorders including autism, schizophrenia, bipolar disorder, major depression, Alzheimer's disease and lissencephaly share a common feature of abnormal Reelin expression in the brain. Altered Reelin expression has been hypothesized to impair neuronal connectivity and synaptic plasticity, leading ultimately to the cognitive deficits present in these disorders. The mechanisms for abnormal Reelin expression in some of these disorders are currently unknown although possible explanations include early developmental insults, mutations, hypermethylation of the promoter for the Reelin gene (RELN), miRNA silencing of Reelin mRNA, FMRP underexpression and Reelin processing abnormalities. Increasing Reelin expression through pharmacological therapies may help ameliorate symptoms resulting from Reelin deficits. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.

Analysis of common genetic variants identifies RELN as a risk gene for schizophrenia in Chinese population

Abstract Objectives. Several lines of evidence have shown that both RELN mRNA and protein are possibly down-regulated in the brain of schizophrenia patients. Recent association studies in European populations suggested RELN as a risk gene for schizophrenia. In this study, we test if RELN contributes to the risk of schizophrenia in Chinese population. Methods. We conducted case-control association analysis of 19 representative single nucleotide polymorphisms (SNPs) spanning the entire region of RELN in two independent Han Chinese samples from southwestern China (the Kunming sample and the Yuxi sample). Results. We identified six SNPs significantly associated with schizophrenia in the Kunming sample and four of them remained significant in the combined samples (the P values range from 0.006 to 4.0 × 10(-5)). Haplotype analysis also suggested significant associations for the haplotypes incorporating the six significant SNPs (global P < 1.0 × 10(-5)). Additionally, we also observed several other haplotypes (defined by a different set of SNPs) significantly associated with schizophrenia in the Kunming sample. However, the reported association of rs7341475 in Ashkenazi Jews was not significant in Han Chinese.

CONCLUSIONS

Our findings demonstrate that RELN is a susceptibility gene for schizophrenia in Chinese population, and it is likely a common risk gene for schizophrenia in major populations worldwide.

Decreased reelin expression in the left prefrontal cortex (BA9) in chronic schizophrenia patients

BACKGROUND

Reelin is under epigenetic control and has been reported to be decreased in cortical regions in schizophrenia.

METHODS

To establish if expression of reelin is altered in specific cortical, hippocampal or thalamic regions of schizophrenia patients, we measured gene expression of reelin in a postmortem study of elderly patients with schizophrenia and non-affected controls in both hemispheres differentiating between gray and white matter. We compared cerebral postmortem samples (dorsolateral prefrontal cortex BA9 and BA46, superior temporal cortex BA22, entorhinal cortex BA28, sensoric cortex BA1-3, hippocampus, CA4, mediodorsal nucleus of the thalamus) from 12 schizophrenia patients with 13 normal subjects investigating gene expression of reelin in the gray and white matter of both hemispheres by in situ-hybridization.

RESULTS

The left prefrontal area (BA9) of schizophrenia patients revealed a decreased expression of reelin-mRNA of 29.1% in the white (p = 0.022) and 13.6% in the gray matter (p = 0.007) compared to the control group. None of the other regions examined showed any statistically significant differences.

CONCLUSION

Since reelin is responsible for migration and synapse formation, the decreased gene expression of reelin in the left prefrontal area of schizophrenia patients points to neurodevelopmental deficits in neuronal migration and synaptic plasticity. However, our study group was small, and results should be verified using larger samples.

Impact of the Reelin signaling cascade (ligands-receptors-adaptor complex) on cognition in schizophrenia

Our previous neurocognitive studies of schizophrenia outlined two clusters of affected subjects--cognitively spared (CS) and cognitive deficit (CD), the latter's characteristics pointing to developmental origins and impaired synaptic plasticity. Here we investigate the contribution of polymorphisms in major regulators of these processes to susceptibility to schizophrenia and to CD in patients. We examine variation in genes encoding proteins at the gateway of Reelin signaling: ligands RELN and APOE, their common receptors APOER2 and VLDLR, and adaptor DAB1. Association analysis with disease outcome and cognitive performance in the Western Australian Family Study of Schizophrenia (WAFSS) was followed by replication analysis in the Australian Schizophrenia Research Bank (ASRB) and in the Health in Men Study (HIMS) of normal aging males. In the WAFSS sample, we observed significant association of APOE, APOER2, VLDLR, and DAB1 SNPs with disease outcome in the case-control and CD-control datasets, and with pre-morbid intelligence and verbal memory in cases. HIMS replication analysis supported rs439401 (APOE regulatory region), and rs2297660 and rs3737983 (APOER2), with an effect on memory performance in normal aging subjects consistent with the findings in schizophrenia cases. APOER2 gene expression analysis revealed lower transcript levels in lymphoblastoid cells from cognitively impaired schizophrenia patients of the alternatively spliced exon 19, mediating Reelin signaling and synaptic plasticity in the adult brain. ASRB replication analysis produced marginally significant results, possibly reflecting a recruitment strategy biased toward CS patients. The data suggest a contribution of neurodevelopmental/synaptic plasticity genes to cognitive impairment in schizophrenia.

An association between high birth weight and schizophrenia in a Finnish schizophrenia family study sample

Longitudinal cohort studies have implicated an association between both low and high birth weight and schizophrenia. It has been suggested that schizophrenia associated genes could augment an individual's susceptibility to adverse prenatal and perinatal environmental events. We investigated the association between birth weight and schizophrenia in a large Finnish schizophrenia family study sample. We utilized the birth weight data of 1051 offspring from 315 Finnish families with at least one offspring with a diagnosis of schizophrenia. We used a multivariate COX frailty model to analyze the effect of birth weight on the risk of developing schizophrenia within the families. Using information from the Medication Reimbursement Register and patient interviews, we further investigated the association of maternal type 2 diabetes and schizophrenia risk among offspring. High birth weight (>4000g) was associated with a 1.68-fold increase in schizophrenia susceptibility. Maternal diabetes at the time of data collection, a proxy for gestational diabetes, was associated with a 1.66-fold increase in the risk of developing schizophrenia among offspring. Our results corroborate recent findings showing an association between high birth weight and schizophrenia. Our results also point to a potential birth-weight independent association between maternal type 2 diabetes and schizophrenia among offspring.

Genome-wide association analysis of age at onset in schizophrenia in a European-American sample

We performed a genome-wide association analysis to identify genetic variants influencing age at onset (AAO) and examine gene × gender interactions for AAO in schizophrenia (SCZ) using a European-American sample (1,162 cases). Linear regression model in PLINK was used to test for associations with AAO while the GxE option was chosen to test for the influence of gene × gender interactions. The most significant association with AAO was observed with SNP rs7819815 (P = 3.10×10(-7)) at 8q24.22. The next best signal was at 4q25 in COL25A1 gene (rs17039583, P = 4.30×10(-6)) and the third region was at 4p16.1 (rs17407555, P = 4.56×10(-6) , near RAF1P1, and rs4697924, P = 1.23×10(-5) within WDR1 gene). Conditional analysis on chromosome 4 indicated that 4p16.1 and 4q25 loci were independent. Furthermore, 2 SNPs (rs16834822 and rs16834824) at 1q43 in RYR2 showed strong associations in the female sample (P = 2.10×10(-6) and 2.33×10(-6) , respectively) and strong gene × gender interactions in influencing AAO (P = 9.23×10(-7) and 1.15×10(-6) , respectively) while the second best region showing gene × gender interaction was at 7q22.3 (rs179863, P = 2.33×10(-6) ). Using an independent sample of 1,068 cases, we could not replicate the associations for above top SNPs; however, we found nominal significance associations for their flanking SNPs (P < 0.05). These findings provide evidence of several genetic variants influencing AAO of SCZ.

Extracellular matrix abnormalities in schizophrenia

Emerging evidence points to the involvement of the brain extracellular matrix (ECM) in the pathophysiology of schizophrenia (SZ). Abnormalities affecting several ECM components, including Reelin and chondroitin sulfate proteoglycans (CSPGs), have been described in subjects with this disease. Solid evidence supports the involvement of Reelin, an ECM glycoprotein involved in corticogenesis, synaptic functions and glutamate NMDA receptor regulation, expressed prevalently in distinct populations of GABAergic neurons, which secrete it into the ECM. Marked changes of Reelin expression in SZ have typically been reported in association with GABA-related abnormalities in subjects with SZ and bipolar disorder. Recent findings from our group point to substantial abnormalities affecting CSPGs, a main ECM component, in the amygdala and entorhinal cortex of subjects with schizophrenia, but not bipolar disorder. Striking increases of glial cells expressing CSPGs were accompanied by reductions of perineuronal nets, CSPG- and Reelin-enriched ECM aggregates enveloping distinct neuronal populations. CSPGs developmental and adult functions, including neuronal migration, axon guidance, synaptic and neurotransmission regulation are highly relevant to the pathophysiology of SZ. Together with reports of anomalies affecting several other ECM components, these findings point to the ECM as a key component of the pathology of SZ. We propose that ECM abnormalities may contribute to several aspects of the pathophysiology of this disease, including disrupted connectivity and neuronal migration, synaptic anomalies and altered GABAergic, glutamatergic and dopaminergic neurotransmission.

GWAS findings for human iris patterns: associations with variants in genes that influence normal neuronal pattern development

Human iris patterns are highly variable. The origins of this variation are of interest in the study of iris-related eye diseases and forensics, as well as from an embryological developmental perspective, with regard to their possible relationship to fundamental processes of neurodevelopment. We have performed genome-wide association scans on four iris characteristics (crypt frequency, furrow contractions, presence of peripupillary pigmented ring, and number of nevi) in three Australian samples of European descent. Both the discovery (n = 2121) and replication (n = 499 and 73) samples showed evidence for association between (1) crypt frequency and variants in the axonal guidance gene SEMA3A (p = 6.6 × 10(-11)), (2) furrow contractions and variants within the cytoskeleton gene TRAF3IP1 (p = 2.3 × 10(-12)), and (3) the pigmented ring and variants in the well-known pigmentation gene SLC24A4 (p = 7.6 × 10(-21)). These replicated findings individually accounted for around 1.5%-3% of the variance for these iris characteristics. Because both SEMA3A and TRAFIP1 are implicated in pathways that control neurogenesis, neural migration, and synaptogenesis, we also examined the evidence of enhancement among such genes, finding enrichment for crypts and furrows. These findings suggest that genes involved in normal neuronal pattern development may also influence tissue structures in the human iris.

Association study of RELN polymorphisms with schizophrenia in Han Chinese population

Schizophrenia (SZ) is a common and complex psychiatric disorder with a strong genetic component. Previous research suggests that mutations altering genes in neurodevelopmental pathways contribute to SZ. Reelin gene (RELN) maps to chromosome 7q22.1, the encoded protein plays a pivotal role in guiding neuronal migration, lamination and connection during embryonic brain development. Several reports had indicated that reduced RELN expression is associated with human mental illnesses such as SZ, mood disorders and autism. In this study, case-control association analyses were performed in the Han Chinese population to determine if the RELN gene is a susceptibility gene for SZ. Thirty-seven single nucleotide polymorphisms (SNPs) were genotyped in 528 paranoid SZ patients and 528 control subjects. A significant association was found between rs12705169 and SZ (p=0.001). Moreover, the haplotypes constructed from five SNPs showed significant differences between cases and controls (p=0.041). When subjects were divided by gender, rs12705169 remained significant difference only in females (OR=0.24, 95%CI=0.14-0.40 for CC and OR=0.40, 95%CI=0.27-0.58 for AC), both in the allele and genotype (p=0.0001 for both). This study describes a positive association between RELN and SZ in the Han Chinese population, and provides genetic evidence to support the gender difference of SZ.

Possible association of the semaphorin 3D gene (SEMA3D) with schizophrenia

Semaphorins are ligands of plexins, and the plexin-semaphorin signaling system is widely involved in many neuronal events including axon guidance, cell migration, axon pruning, and synaptic plasticity. The plexin A2 gene (PLXNA2) has been reported to be associated with schizophrenia. This finding prompted us to examine the possible association between the semaphorin 3D gene (SEMA3D) and schizophrenia in a Japanese population. We genotyped 9 tagging single nucleotide polymorphisms (SNPs) of SEMA3D including a non-synonymous variation, Lys701Gln (rs7800072), in a sample of 506 patients with schizophrenia and 941 healthy control subjects. The Gln701 allele showed a significant protective effect against the development of schizophrenia (p = 0.0069, odds ratio = 0.76, 95% confidence interval 0.63 to 0.93). Furthermore, the haplotype-based analyses revealed a significant association. The four-marker analysis (rs2190208-rs1029564-rs17159614-rs12176601), in particular, not including the Lys701Gln, revealed a highly significant association (p = 0.00001, global permutation), suggesting that there may be other functional polymorphisms within SEMA3D. Our findings provide strong evidence that SEMA3D confers susceptibility to schizophrenia, which could contribute to the neurodevelopmental impairments in the disorder.