Association study of the G-protein signaling 4 (RGS4) and proline dehydrogenase (PRODH) genes with schizophrenia: a meta-analysis

Association between RGS4 gene polymorphisms and schizophrenia: A protocol for systematic review and meta-analysis

BACKGROUND

Schizophrenia is a complex brain disorder, the pathogenesis of which remains unclear. Regulator of G-protein signaling 4 is regarded as a candidate gene for schizophrenia risk. The association between the regulator of G-protein signaling 4 gene and the risk of schizophrenia is complicated and controversial, thus, an updated meta-analysis is needed.

METHODS

A search strategy using Medical Subject Headings was developed in English (PubMed, SZGene) and Chinese (CNKI, Wanfang, and Weipu) databases. Inclusion and exclusion criteria were used to screen for eligible studies. Parameters, such as P value of Hardy-Weinberg equilibrium, odds ratios, 95% confidence intervals, P values of association, heterogeneity (Ph), and publication bias, were analyzed by the Stata software using a random effects model. Subgroup analyses were performed to detect heterogeneity.

RESULTS

There were 15 articles regarding rs10917670 (8046 cases and 8837 controls), 16 regarding rs951436 (8990 cases and 10,568 controls), 15 regarding rs951439 (7995 cases and 8646 controls), 15 regarding rs2661319 (8320 cases and 9440 controls), and 4 regarding rs10759 (2752 cases and 2866 controls). The frequencies of rs10917670 and rs951439 were not significantly different between the case and control groups (P > .05). As shown by the East Asian and hospital-based subgroup analyses, the genotype TT of rs951436 might be related to the risk of schizophrenia. The genotypes CC + CT of rs2661319 and CC + CA of rs10759 were statistically different between the 2 groups, and the East Asian population contributed to these differences.

CONCLUSION

The genotypes CC + CT of rs2661319 and CC + CA of rs10759 might be associated with the risk of schizophrenia.

Association Analysis Between SNPs in the Promoter Region of RGS4 and Schizophrenia in the Northern Chinese Han Population

BACKGROUND

Abnormal RGS4 gene expression may cause neurotransmitter disorders, resulting in schizophrenia. The association between RGS4 and the risk of schizophrenia is controversial, and there has been little research on the SNPs in the promoter region of RGS4.

PURPOSE

The present study was performed to detect the association between SNPs in the promoter region of the RGS4 gene and the risk of schizophrenia.

MATERIALS AND METHODS

In this study, the 1757-bp fragment (-1119-+600, TSS+1) of RGS4 was amplified and sequenced in 198 schizophrenia patients and 264 healthy controls of the northern Chinese Han population. Allele, genotype and haplotype frequencies were analyzed by chi-square test.

RESULTS

Four SNPs were detected in the region. LD analysis determined that rs7515900 was linked to rs10917671 (D' = 1, r² = 1). Therefore, the data for rs10917671 were eliminated from further analysis. Genotype TT of rs12041948 (P = 0.009, OR = 1.829, and 95% CI = 0.038-0.766) was significantly different between the two groups in the northern Chinese Han population. In males, genotype GG of rs6678136 (P = 0.009, OR = 2.292, and 95% CI = 1.256-4.18) and CC of rs7515900 (P = 0.003, OR = 2.523, and 95% CI = 1.332-4.778) were significantly different.

CONCLUSION

The results of this study suggested that genotype TT of rs12041948 in the pooled male and female samples and GG of rs6678136 and CC of rs7515900 in the male samples could be risk factors for schizophrenia. The present study is the first to detect an association between SNPs in the promoter region of the RGS4 gene and the risk of schizophrenia in the northern Chinese Han population. Functional studies are required to confirm these findings.

A gene-based review of RGS4 as a putative risk gene for psychiatric illness

Considerable efforts have been made to characterize RGS4 as a potential candidate gene for schizophrenia. Investigations span across numerous modalities and include explorations of genetic risk associations, mRNA and protein levels in the brain, and functionally relevant interactions with other candidate genes as well as links to schizophrenia relevant neural phenotypes. While these lines of investigations have yielded partially inconsistent findings, they provide a perspective on RGS4 as an important part of a larger biological system contributing to schizophrenia risk. This gene-based review aims to provide a comprehensive overview of published data from different experimental modalities and discusses the current knowledge of RGS4's systems-biological impact on the schizophrenia pathology.

Proline dehydrogenase gene (PRODH) polymorphisms and schizophrenia susceptibility: a meta-analysis

Previous studies have been conducted to explore the association between proline dehydrogenase gene (PRODH) polymorphisms and schizophrenia (SZ) susceptibility, but providing the controversial results. Here we performed this meta-analysis to determine whether PRODH variants were associated with SZ risk. Relevant studies were screened by retrieving online database PubMed, Web of Science, Embase, China National Knowledge Infrastructure (CNKI) and SZGene from inception to December 2016. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated based on genotype data or allele frequency to evaluate the strength of this association. For rs372055, eleven studies with 3398 SZ patients and 3171 controls were included and the results indicated that people carrying the T allele was not associated with SZ risk in allele frequency model (C vs T, OR = 1.12, 95%CI = 0.96-1.32). However, results from subgroup analysis showed a significant relationship between rs372055 and SZ risk in dominant genetic model (CC + CT vs TT, OR = 1.26, 95% CI = 1.05-1.50) and heterogeneous model (CT vs TT, OR = 1.26, 95% CI = 1.05-1.52) in Asian, but not in Caucasian. For polymorphisms rs383964, rs450046, rs385440 and rs2870983, no associations were found between these polymorphisms and SZ susceptibility in allele frequency. This meta-analysis suggests that rs372055 (C/T) polymorphism in PRODH gene is associated with increased SZ risk only in Asian.

Association between RGS4 variants and psychotic-like experiences in nonclinical individuals

The psychosis phenotype is expressed across a continuum known as schizotypy, which ranges from personality variation through subclinical symptoms to severe psychopathology. The study of subclinical manifestations in non-affected individuals minimizes confounding factors associated with the clinical phenotype and facilitates the differentiation of dimension-specific etiological mechanisms. The aim of the present study was to investigate the association between the variation in the regulator of G-protein signaling 4 (RGS4) gene, a putative candidate gene for psychosis previously associated with schizophrenia endophenotypes, and psychotic-like experiences (PLEs). In total, 808 healthy individuals completed the community assessment of psychic experiences (CAPE) to measure positive and negative PLEs and provided a DNA sample. Two RGS4 single-nucleotide polymorphisms (SNPs) (rs951436 [SNP4] and rs2661319 [SNP18]) were genotyped. Analyses of covariance (ANCOVA) were used to explore the association of positive and negative PLEs with RGS4 variation. Our results showed associations of positive and negative PLEs with the two polymorphisms studied: subjects with the T allele (SNP4) and the A allele (SNP18) had higher scores on both the positive and the negative dimensions. Haplotypic analyses supported these results, showing the highest scores in those with the TA haplotype (SNP4-SNP18). The RGS4 variants might exert gene-specific modulating effects on psychosis proneness.

Molecular genetic models related to schizophrenia and psychotic illness: heuristics and challenges

Schizophrenia is a heritable disorder that may involve several common genes of small effect and/or rare copy number variation, with phenotypic heterogeneity across patients. Furthermore, any boundaries vis-à-vis other psychotic disorders are far from clear. Consequently, identification of informative animal models for this disorder, which typically relate to pharmacological and putative pathophysiological processes of uncertain validity, faces considerable challenges. In juxtaposition, the majority of mutant models for schizophrenia relate to the functional roles of a diverse set of genes associated with risk for the disorder or with such putative pathophysiological processes. This chapter seeks to outline the evidence from phenotypic studies in mutant models related to schizophrenia. These have commonly assessed the degree to which mutation of a schizophrenia-related gene is associated with the expression of several aspects of the schizophrenia phenotype or more circumscribed, schizophrenia-related endophenotypes; typically, they place specific emphasis on positive and negative symptoms and cognitive deficits, and extend to structural and other pathological features. We first consider the primary technological approaches to the generation of such mutants, to include their relative merits and demerits, and then highlight the diverse phenotypic approaches that have been developed for their assessment. The chapter then considers the application of mutant phenotypes to study pathobiological and pharmacological mechanisms thought to be relevant for schizophrenia, particularly in terms of dopaminergic and glutamatergic dysfunction, and to an increasing range of candidate susceptibility genes and copy number variants. Finally, we discuss several pertinent issues and challenges within the field which relate to both phenotypic evaluation and a growing appreciation of the functional genomics of schizophrenia and the involvement of gene × environment interactions.

Copy number variation at 22q11.2: from rare variants to common mechanisms of developmental neuropsychiatric disorders

Recently discovered genome-wide rare copy number variants (CNVs) have unprecedented levels of statistical association with many developmental neuropsychiatric disorders, including schizophrenia, autism spectrum disorders, intellectual disability and attention deficit hyperactivity disorder. However, as CNVs often include multiple genes, causal genes responsible for CNV-associated diagnoses and traits are still poorly understood. Mouse models of CNVs are in use to delve into the precise mechanisms through which CNVs contribute to disorders and associated traits. Based on human and mouse model studies on rare CNVs within human chromosome 22q11.2, we propose that alterations of a distinct set of multiple, noncontiguous genes encoded in this chromosomal region, in concert with modulatory impacts of genetic background and environmental factors, variably shift the probabilities of phenotypes along a predetermined developmental trajectory. This model can be further extended to the study of other CNVs and may serve as a guide to help characterize the impact of genes in developmental neuropsychiatric disorders.

Brain RGS4 and RGS10 protein expression in schizophrenia and depression. Effect of drug treatment

RATIONALE

Regulator of G-protein signaling (RGS) proteins, RGS4 and RGS10, may be involved in the pathophysiology of schizophrenia. RGS4 has attracted special interest since the reports of genetic association between SNPs in RGS4 and schizophrenia. However, there is no information about the subcellular distribution of RGS4 and RGS10 proteins in psychiatric disorders.

OBJECTIVES

Plasma membrane RGS4 and cytosolic RGS10 protein immunoreactivity in prefrontal cortex from schizophrenic subjects (n = 25), non-diagnosed suicides (n = 13), and control subjects (n = 35), matched by age, gender, and postmortem delay, was analyzed by western blot. A second group of depressed subjects (n = 25) and control subjects (n = 25) was evaluated. The effect of the antipsychotic or antidepressant treatments was also assessed.

RESULTS

No significant differences in plasma membrane RGS4 and cytosolic RGS10 protein expression were observed between schizophrenic subjects, non-diagnosed suicides, and control subjects. However, RGS4 immunoreactivity was significantly higher (Δ = 33 ± 10 %, p < 0.05) in the antipsychotic-treated subgroup (n = 12) than in the antipsychotic-free subgroup (n = 13). Immunodensities of plasma membrane RGS4 and cytosolic RGS10 proteins did not differ between depressed and matched control subjects.

CONCLUSIONS

Expression of RGS4 and RGS10 proteins at their predominant subcellular location was studied in the postmortem brain of subjects with psychiatric disorders. The results suggest unaltered membrane RGS4 and cytosolic RGS10 proteins levels in schizophrenia and major depression. Antipsychotic treatment seems to increase membrane RGS4 immunoreactivity. Further studies are needed to elucidate RGS4 and RGS10 functional status.

Variation in regulator of G-protein signaling 17 gene (RGS17) is associated with multiple substance dependence diagnoses

Background

RGS17 and RGS20 encode two members of the regulator of G-protein signaling RGS-Rz subfamily. Variation in these genes may alter their transcription and thereby influence the function of G protein-coupled receptors, including opioid receptors, and modify risk for substance dependence.

Methods

The association of 13 RGS17 and eight RGS20 tag single nucleotide polymorphisms (SNPs) was examined with four substance dependence diagnoses (alcohol (AD), cocaine (CD), opioid (OD) or marijuana (MjD)] in 1,905 African Americans (AAs: 1,562 cases and 343 controls) and 1,332 European Americans (EAs: 981 cases and 351 controls). Analyses were performed using both χ² tests and logistic regression analyses that covaried sex, age, and ancestry proportion. Correlation of genotypes and mRNA expression levels was assessed by linear regression analyses.

Results

Seven RGS17 SNPs showed a significant association with at least one of the four dependence traits after a permutation-based correction for multiple testing (0.003≤P_empirical≤0.037). The G allele of SNP rs596359, in the RGS17 promoter region, was associated with AD, CD, OD, or MjD in both populations (0.005≤P_empirical≤0.019). This allele was also associated with significantly lower mRNA expression levels of RGS17 in YRI subjects (P = 0.002) and non-significantly lower mRNA expression levels of RGS17 in CEU subjects (P = 0.185). No RGS20 SNPs were associated with any of the four dependence traits in either population.

Conclusions

This study demonstrated that variation in RGS17 was associated with risk for substance dependence diagnoses in both AA and EA populations.

Contribution of nonprimate animal models in understanding the etiology of schizophrenia

Schizophrenia is a severe psychiatric disorder that is characterized by positive and negative symptoms and cognitive impairments. The etiology of the disorder is complex, and it is thought to follow a multifactorial threshold model of inheritance with genetic and neurodevelop mental contributions to risk. Human studies are particularly useful in capturing the richness of the phenotype, but they are often limited to the use of correlational approaches. By assessing behavioural abnormalities in both humans and rodents, nonprimate animal models of schizophrenia provide unique insight into the etiology and mechanisms of the disorder. This review discusses the phenomenology and etiology of schizophrenia and the contribution of current nonprimate animal models with an emphasis on how research with models of neuro transmitter dysregulation, environmental risk factors, neurodevelopmental disruption and genetic risk factors can complement the literature on schizophrenia in humans.

Testing for genetic association between the ZDHHC8 gene locus and susceptibility to schizophrenia: An integrated analysis of multiple datasets

A number of studies have reported an association between the ZDHHC8 gene locus and schizophrenia but have produced some divergent findings and their interpretation is not straightforward. We investigated the association of the ZDHHC8 gene locus with schizophrenia using meta-analytic techniques, combining all published data up to May 2009 and focusing on 10 independent studies from six published references covering 2,894 cases, 2,932 controls and 1,225 parent-offspring trios. We restricted the analysis to studies investigating rs175174, the most frequently studied single nucleotide polymorphism (SNP). Stratified meta-analysis was conducted to investigate whether ancestry, study design, or gender moderated any association. Analyses of linkage disequilibrium (LD) and haplotype structure of this gene locus were also performed based on the hapmap project genotype data to determine whether there were other independent polymorphic markers which might contribute to susceptibility to schizophrenia in particular ethnic populations. We found no allelic- or genotype-wise evidence for an association of the rs175174 SNP with schizophrenia in our overall analysis. After applying stratified analyses, there was only a weak nominal genotype-wise association of this SNP with schizophrenia in the dominant genetic model in East Asian populations (P = 0.049), which might be caused by significant between-study heterogeneity (P = 0.042). No significant publication bias was detected. Other polymorphic markers within this gene genotyped in the hapmap project across different ethnic populations were in strong LD with rs175174. Consistently negative associations were found in the rs175174 polymorphism. LD structure further suggested that the ZDHHC8 locus might not play an important role in the etiology of schizophrenia.

RGS4 polymorphisms associated with variability of cognitive performance in a family-based schizophrenia sample

Polymorphisms of the gene encoding the regulator of G protein signaling, subtype 4 (RGS4), may be associated with schizophrenia. Among first-episode schizophrenia patients, they are also associated with dorsolateral prefrontal cortex (DLPFC) volume. The DLPFC is a key region that regulates heritable cognitive functions implicated in schizophrenia pathogenesis. To further understand the relationship of RGS4 variants to schizophrenia, we examined their associations with cognitive functions among schizophrenia patients and their relatives. We analyzed 31 multiplex, multigenerational Caucasian families with schizophrenia recruited on the basis of 2 affected first-degree relatives. All participants underwent a computerized neurocognitive battery that evaluates accuracy and speed (response time) of performance on abstraction/mental flexibility; attention; verbal, spatial, and face memory; and spatial ability. "Tag" single-nucleotide polymorphisms (SNPs) representing common polymorphisms were genotyped. Measured genotype analyses accounting for family relationships were performed using Sequential Oligogenic Linkage Analysis Routines. SNPs rs10917670 ("SNP1") and rs951439 ("SNP7") were associated with face memory speed (P = .0003) at a significance level that survived Bonferroni correction (P = .039). The same SNPs have earlier been reported to be associated with schizophrenia. There also were uncorrected associations with rs10917670 ("SNP1") and rs951439 ("SNP7") on face memory efficiency (P = .03) and verbal memory efficiency (P = 0.02), rs28757217 on abstraction/mental flexibility speed (P = .02) and verbal memory efficiency (P = .03), SNP18 (rs2661319) on spatial memory accuracy (P = 0.02) and face memory speed (P = .03). RGS4 polymorphisms are associated with variations in cognitive functions and contribute a small but statistically significant proportion of variance in a family-based sample.

Anxiety and depression in children and adults: influence of serotonergic and neurotrophic genes?

There are two major hypotheses regarding the etiology of anxiety and depression: the mono-amine hypothesis and the hypothesis of an abnormal stress response acting partly via reduced neurogenesis. Association studies have focused on genes involved in these processes, but with inconclusive results. This study investigated the effect of 45 single nucleotide polymorphisms (SNPs) in genes encoding for serotonin receptors 1A, 1D, 2A, catechol-O-methyltransferase (COMT), tryptophane hydroxylase type 2 (TPH2), brain derived neurotrophic factor (BDNF), PlexinA2 and regulators of G-protein-coupled signaling (RGS) 2, 4, 16. Anxious depression (A/D) symptoms were assessed five times in 11 years in over 11 000 adults with 1504 subjects genotyped and at age 7, 10, 12 and during adolescence in over 20 000 twins with 1078 subjects genotyped. In both cohorts, a longitudinal model with one latent factor loading on all A/D measures over time was analysed. The genetic association effect modeled at the level of this latent factor was 60% and 70% heritable in the children and adults, respectively, and explained around 50% of the total phenotypic variance. Power analyses showed that the samples contained 80% power to detect an effect explaining between 1.4% and 3.6% of the variance. However, no SNP showed a consistent effect on A/D. To conclude, this longitudinal study in children and adults found no association of SNPs in the serotonergic system or core regulators of neurogenesis with A/D. Overall, there has been no convincing evidence, so far, for a role of genetic variation in these pathways in the development of anxiety and depression.

Supportive evidence for reduced expression of GNB1L in schizophrenia

BACKGROUND

Chromosome 22q11 deletion syndrome (22q11DS) increases the risk of development of schizophrenia more than 10 times compared with that of the general population, indicating that haploinsufficiency of a subset of the more than 20 genes contained in the 22q11DS region could increase the risk of schizophrenia. In the present study, we screened for genes located in the 22q11DS region that are expressed at lower levels in postmortem prefrontal cortex of patients with schizophrenia than in those of controls.

METHODS

Gene expression was screened by Illumina Human-6 Expression BeadChip arrays and confirmed by real-time reverse transcription-polymerase chain reaction assays and Western blot analysis.

RESULTS

Expression of GNB1L was lower in patients with schizophrenia than in control subjects in both Australian (10 schizophrenia cases and 10 controls) and Japanese (43 schizophrenia cases and 11 controls) brain samples. TBX1 could not be evaluated due to its low expression levels. Expression levels of the other genes were not significantly lower in patients with schizophrenia than in control subjects. Association analysis of tag single-nucleotide polymorphisms in the GNB1L gene region did not confirm excess homozygosity in 1918 Japanese schizophrenia cases and 1909 Japanese controls. Haloperidol treatment for 50 weeks increased Gnb1l gene expression in prefrontal cortex of mice.

CONCLUSIONS

Taken together with the impaired prepulse inhibition observed in heterozygous Gnb1l knockout mice reported by the previous study, the present findings support assertions that GNB1L is one of the genes in the 22q11DS region responsible for increasing the risk of schizophrenia.

The quality of meta-analyses of genetic association studies: a review with recommendations

Although there has been a rapid rise in the publication of meta-analyses of genetic association studies, little is known about their methodological quality. The authors reviewed the quality of 120 randomly selected genetic meta-analyses published between 2005 and 2007. Data extracted included issues of general relevance and other issues specific to genetic epidemiology. Quality was markedly poorer in the 26% of the meta-analyses that accompanied a report on a primary study. Such meta-analyses were predominantly published in specialist journals, and their quality was positively associated with the impact factor of the journal. Among the meta-analyses that did not accompany a primary study, Human Genome Epidemiology reviews tended to score better than the others, although the comparison was limited by relatively small numbers. Comparison of the overall quality with that of genetic meta-analyses published before 2000 showed improvement in both conduct and reporting. However, the quality of the handling of specific genetic issues remains disappointingly low. For a few key general quality issues, the authors compared their findings with findings in other fields of medicine and found that general quality was similar. On the basis of this review, the authors provide practical recommendations for the conduct and reporting of genetic meta-analyses.

Cloning and characterization of rabbit Rgs4 promoter in gut smooth muscle

Regulator of G-protein signaling 4 (Rgs4) regulates the strength and duration of G-protein signaling, and plays an important role in cardiac development, smooth muscle contraction and psychiatric disorders. Rgs4 expression is regulated at both mRNA and protein levels. In order to examine the transcriptional mechanism of Rgs4 expression, we have cloned and characterized rabbit Rgs4 promoter. The coding sequence of rabbit Rgs4 was obtained by degenerative RT-PCR and used for Northern blot and 5'-RACE analysis. A single transcript was identified in rabbit colonic smooth muscle cells. The 5'-untranslated region (UTR) extended 120 bp nucleotides upstream of the Rgs4 start codon. A putative promoter sequence (1389 bp) showed a consensus TATA box and cis-acting binding sites for several potential transcriptional factors. Reporter gene assay identified strong promoter activity in various cell types. Further analysis by deletion mutagenesis suggested that the proximal region had a highest core promoter activity while the distal region is suppressive. IL-1beta significantly increased the promoter activity. The in vitro and in vivo binding activities for NF-kappaB transcription factor were validated by electrophoretic mobility shift assay and chromatin immunoprecipitation assay respectively. Mutation of NF-kappaB site reduced the promoter activity. These data suggest that the cloned rabbit Rgs4 promoter is functionally active and NF-kappaB binding site possesses enhancer activity in regulating Rgs4 transcription. Our studies provide an important basis for further understanding of Rgs4 regulation and function in different diseases.

Small molecule protein-protein interaction inhibitors as CNS therapeutic agents: current progress and future hurdles

Protein-protein interactions are a crucial element in cellular function. The wealth of information currently available on intracellular-signaling pathways has led many to appreciate the untapped pool of potential drug targets that reside downstream of the commonly targeted receptors. Over the last two decades, there has been significant interest in developing therapeutics and chemical probes that inhibit specific protein-protein interactions. Although it has been a challenge to develop small molecules that are capable of occluding the large, often relatively featureless protein-protein interaction interface, there are increasing numbers of examples of small molecules that function in this manner with reasonable potency. This article will highlight the current progress in the development of small molecule protein-protein interaction inhibitors that have applications in the treatment or study of central nervous system function and disease. In particular, we will focus upon recent work towards developing small molecule inhibitors of amyloid-beta and alpha-synuclein aggregation, inhibitors of critical components of G-protein-signaling pathways, and PDZ domain inhibitors.

Functional polymorphisms in PRODH are associated with risk and protection for schizophrenia and fronto-striatal structure and function

PRODH, encoding proline oxidase (POX), has been associated with schizophrenia through linkage, association, and the 22q11 deletion syndrome (Velo-Cardio-Facial syndrome). Here, we show in a family-based sample that functional polymorphisms in PRODH are associated with schizophrenia, with protective and risk alleles having opposite effects on POX activity. Using a multimodal imaging genetics approach, we demonstrate that haplotypes constructed from these risk and protective functional polymorphisms have dissociable correlations with structure, function, and connectivity of striatum and prefrontal cortex, impacting critical circuitry implicated in the pathophysiology of schizophrenia. Specifically, the schizophrenia risk haplotype was associated with decreased striatal volume and increased striatal-frontal functional connectivity, while the protective haplotype was associated with decreased striatal-frontal functional connectivity. Our findings suggest a role for functional genetic variation in POX on neostriatal-frontal circuits mediating risk and protection for schizophrenia.

Schizophrenia is a major mental illness affecting 1% of the population. It is known that genetics plays a role in the disease susceptibility, and it is thought that the illness is a complex disorder involving multiple genes. We show that the schizophrenia susceptibility gene, PRODH, conveys its risk through a variation that increases its enzyme activity. We further show that protection is associated with variations that decrease enzyme activity and these protective variations are enriched in their unaffected siblings. We then used brain imaging of structure and memory function to dissect the risk and protective haplotypes differential effects, and found that the schizophrenia risk haplotype was associated with decreased striatal gray matter volume and increased subcortical to frontal lobe functional connectivity, while the schizophrenia protective haplotype was associated with trend-level increase of frontal lobe volume and decreased subcortical to frontal lobe connectivity. These findings indicate a new target for treating schizophrenia and characterize associated structural and functional deficits.

Adjuvant chemotherapy in oesophageal cancer: a meta-analysis and experience from the Shanghai Cancer Hospital

Whether adjuvant chemotherapy increases survival of oesophageal cancer patients has been widely debated. The present study used meta-analysis software to combine data from six studies up to July 2007 that were found and selected as suitable, comprising a total of 1001 oesophageal cancer patients. The results indicated that adjuvant chemotherapy did not significantly improve outcome in oesophageal cancer patients. A trend towards improved outcome from adjuvant chemotherapy was found in lymph node-positive patients, but did not reach significance. In our own study including 270 oesophageal cancer patients, adjuvant chemotherapy did not improve overall patient survival, but did improve survival for patients with metastases in cervical and/or celiac lymph nodes (stage IVa). Although our study had the largest patient sample, more prospective clinical trials with large numbers of patients are necessary to confirm the value of adjuvant chemotherapy in stage IVa patients.

Association of RGS4 variants with schizotypy and cognitive endophenotypes at the population level

Background

While association studies on schizophrenia show conflicting results regarding the importance of the regulator of the G-protein signaling 4 (RGS4) gene, recent work suggests that RGS4 may impact on the structural and functional integrity of the prefrontal cortex. We aimed to study associations of common RGS4 variants with prefrontal dependent cognitive performance and schizotypy endophenotypes at the population level.

Methods

Four RGS4 single nucleotide polymorphisms (SNP1 [rs10917670], SNP4 [rs951436], SNP7 [rs951439], and SNP18 [rs2661319]) and their haplotypes were selected. Their associations with self-rated schizotypy (SPQ), vigilance, verbal, spatial working memory and antisaccade eye performance were tested with regressions in a representative population of 2,243 young male military conscripts.

Results

SNP4 was associated with negative schizotypy (higher SPQ negative factor for common T allele, p = 0.009; p = 0.031 for differences across genotypes) and a similar trend was seen also for common A allele of SNP18 (p = 0.039 for allele-load model; but p = 0.12 for genotype differences). Haplotype analyses showed a similar pattern with a dose-response for the most common haplotype (GGGG) on the negative schizotypy score with or without adjustment for age, IQ and their interaction (p = 0.011 and p = 0.024, respectively). There was no clear evidence for any association of the RGS4 variants with cognitive endophenotypes, except for an isolated effect of SNP18 on antisaccade error rate (p = 0.028 for allele-load model).

Conclusion

Common RGS4 variants were associated with negative schizotypal personality traits amongst a large cohort of young healthy individuals. In accordance with recent findings, this may suggest that RGS4 variants impact on the functional integrity of the prefrontal cortex, thus increasing susceptibility for psychotic spectrum disorders.

Regulator of G-protein signalling 4 expression is not altered in the prefrontal cortex in schizophrenia

OBJECTIVES

Regulator of G-protein signalling 4 (RGS4) modulates signal transduction through several neurotransmitter receptor systems associated with the pathology of schizophrenia. A reported decrease in RGS4 expression in the prefrontal cortex of schizophrenia patients followed by supporting evidence from association studies implicated RGS4 as a susceptibility gene for schizophrenia. Subsequent efforts to extend these findings in post-mortem brain tissue have produced conflicting results. The aim of the present study was to reconcile these discrepancies by examining RGS4 expression in the dorsolateral prefrontal and parietal cortices from subjects with schizophrenia.

METHODS

RGS4 mRNA and protein levels were measured in post-mortem Brodmann area (BA)9 and BA40 tissue from 19 schizophrenia patients subjects and 19 pair-matched controls using in situ hybridization and western blotting.

RESULTS

Levels of RGS4 mRNA (F(1,73)=1.845; p >0.05) or protein (F(1,72)=3.336 x 10(-4), p >0.05) did not vary significantly with diagnosis in BA9 or BA40 from subjects with schizophrenia.

CONCLUSIONS

Altered RGS4 expression is not universally present throughout the cortex of people with schizophrenia.

Renner T. Genetische Befunde zu Schizophrenie

Zusammenfassung: Schizophrene Erkrankungen zeichnen sich durch eine sehr heterogene Symptomatik mit übergreifenden Funktionsstörungen verschiedenster kognitiver Bereiche aus. Die vielfältigen Phänotypen werden durch das Zusammenwirken von genetischer Prädisposition und Umwelteinflüssen erklärt. Pathophysiologische Modelle beinhalten die Dopamin-Überschuss- sowie Glutamat-Mangel-Hypothese, die Radikal-Hypothese und die Hypothese entwicklungsbedingter versus degenerativer Genese. Neben den neurobiologischen Erklärungsansätzen geben Kopplungsstudien mit nachfolgenden Feinkartierungen Hinweise auf potentiell an der Pathophysiologie beteiligte Gene. Den wichtigsten Kandidatengenen, wie Dysbindin (DTNBP1), Neuregulin1 (NRG1) oder DISC-1 (disrupted-in schizophrenia-1), werden Einfluss auf die Signalübertragung sowie der Ausbildung und dem Erhalt der Struktur von neuronalen Netzwerken zugeschrieben. Zu ihnen werden zahlreiche weitere Gene gezählt. Insgesamt ist bei der Pathogenese der Schizophrenie von einer multifaktoriellen Entstehung mit der Interaktion von verschiedenen genetischen und neurobiologischen sowie exogenen Komponenten auszugehen.

Linkage disequilibrium patterns and functional analysis of RGS4 polymorphisms in relation to schizophrenia

The regulator of G-protein signaling 4 (RGS4, chromosome 1q23.3) plays a critical role in G-protein function. Four common single-nucleotide polymorphisms (SNPs) localized between the 5' upstream sequence and the first intron, as well as 2 haplotypes derived from these SNPs may confer liability to schizophrenia (SZ). However, the pattern of associations varies among samples. To help clarify the putative associations, we report the following analyses: (1) a comprehensive catalog of common polymorphisms, (2) linkage disequilibrium (LD) and association analyses using these SNPs, and (3) functional analysis based on dual-luciferase promoter assays. We identified 62 SNPs from a 20-kb genomic region spanning RGS4, of which 26 are common polymorphisms with a minor allele frequency (MAF) of >5%. LD analysis suggested 5 clusters of SNPs (r(2) > .8). Association analyses using the novel SNPs were consistent with the prior reports, but further localization was constrained by significant LD across the region. The 2 haplotypes reported to confer liability to SZ had significant promoter activity compared with promoterless constructs, suggesting a functional role for both haplotypes. Further analyses of promoter sequences are warranted to understand transcriptional regulation at RGS4. This information will be useful for further analysis of samples in which genetic association of RGS4 polymorphisms with SZ has been reported.

Association study between the dystrobrevin binding protein 1 gene (DTNBP1) and schizophrenia: a meta-analysis

Positional, functional and association studies have strongly implicated the dystrobrevin binding protein 1 gene (DTNBP1) as a promising novel candidate gene for schizophrenia. Since the first association study was reported, there have been many attempts to replicate it. However the results have been mixed and these subsequent studies have produced negative as well as positive results. To reconcile these conflicting findings and to give a comprehensive picture of the relationship of DTNBP1 and schizophrenia, the current meta-analysis combined all published association studies involving nine polymorphisms up to May 2006. The results (12 studies including 3429 cases, 3376 controls and 721 trios) showed that there were five single nucleotide polymorphisms (SNPs) with p values < 0.05, however, sensitivity analyses showed that only one SNP was consistent across all nine studies (four of the five SNPs became non-significant after removal of one study), indicating that one study may cause the association findings for each of these four SNPs. In conclusion, there is only a weak association of one SNP in DTNBP1 with schizophrenia, which is not significant after multiple testing.