The genetic contribution of the NO system at the glutamatergic post-synapse to schizophrenia : further evidence and meta-analysis

NO is a pleiotropic signaling molecule and has an important role in cognition and emotion. In the brain, NO is produced by neuronal nitric oxide synthase (NOS-I, encoded by NOS1) coupled to the NMDA receptor via PDZ. interactions; this protein-protein interaction is disrupted upon binding of NOS1 adapter protein (encoded by NOS1AP) to NOS-I. As both NOS1 and NOS1AP were associated with schizophrenia, we here investigated these genes in greater detail by genotyping new samples and conducting a meta-analysis of our own and published data. In doing so, we confirmed association of both genes with schizophrenia and found evidence for their interaction in increasing risk towards disease. Our strongest finding was the NOS1 promoter SNP rs41279104, yielding an odds ratio of 1.29 in the meta-analysis. As findings from heterologous cell systems have suggested that the risk allele decreases gene expression, we studied the effect of the variant on NOS1 expression in human post-mortem brain samples and found that the risk allele significantly decreases expression of NOS1 in the prefrontal cortex. Bioinformatic analyses suggest that this might be due the replacement of six transcription factor binding sites by two new binding sites as a consequence of proxy SNPs. Taken together, our data argue that genetic variance in NOS1 resulting in lower prefrontal brain expression of this gene contributes to schizophrenia liability, and that NOS1 interacts with NOS1AP in doing so. The NOS1-NOS1AP PDZ interface may thus well constitute a novel target for small molecules in at least some forms of schizophrenia. PostprintPeer reviewe

Genome-wide significant linkage of schizophrenia-related neuroanatomical trait to 12q24

The insula and medial prefrontal cortex (mPFC) share functional, histological, transcriptional and developmental characteristics and they serve higher cognitive functions of theoretical relevance to schizophrenia and related disorders. Meta-analyses and multivariate analysis of structural magnetic resonance imaging (MRI) scans indicate that gray matter density and volume reductions in schizophrenia are the most consistent and pronounced in a network primarily composed of the insula and mPFC. We used source-based morphometry, a multivariate technique optimized for structural MRI, in a large sample of randomly ascertained pedigrees (N = 887) to derive an insula-mPFC component and to investigate its genetic determinants. Firstly, we replicated the insula-mPFC gray matter component as an independent source of gray matter variation in the general population, and verified its relevance to schizophrenia in an independent case-control sample. Secondly, we showed that the neuroanatomical variation defined by this component is largely determined by additive genetic variation (h2 = 0.59), and genome-wide linkage analysis resulted in a significant linkage peak at 12q24 (LOD = 3.76). This region has been of significant interest to psychiatric genetics as it contains the Darier’s disease locus and other proposed susceptibility genes (e.g. DAO, NOS1), and it has been linked to affective disorders and schizophrenia in multiple populations. Thus, in conjunction with previous clinical studies, our data imply that one or more psychiatric risk variants at 12q24 are co-inherited with reductions in mPFC and insula gray matter concentration

MK-801-induced impairments on the Trial-Unique, Delayed Nonmatching-to-Location task in rats: effects of acute sodium nitroprusside

The cognitive symptoms observed in schizophrenia are highly prevalent and predictive of patient functional outcome but are not usually alleviated by conventional antipsychotics. In a recent pilot study, sodium nitroprusside (SNP), a nitric oxide donor, was identified as a promising adjunct treatment to reduce the working memory impairments experienced by schizophrenia patients. Adjunctive SNP has also been reported to decrease the positive and negative symptoms experienced by patients for weeks following a single administration. The mechanisms underlying these changes and the areas of cognition affected remain largely unknown. Therefore, it is of interest to examine the effects of SNP using a rodent model of schizophrenia that has demonstrated predictive validity. The aim of the present experiment was to explore the effects of SNP on the acute MK-801 rodent model of schizophrenia using a highly translatable task in order to establish its validity. Working memory and pattern separation were measured using the trial-unique, delayed nonmatching-to-location (TUNL) task in touchscreen-equipped operant conditioning chambers. Acute MK-801 administration 25 minutes prior to task initiation impaired both areas of cognition. When SNP and MK-801 were administered within 5 minutes of each other, no interaction was observed. Interestingly, SNP improved performance on trials with difficult to discriminate patterns (p=0.058). Previous rodent studies using the ketamine model of schizophrenia and the novel object preference task observed a preventative effect of SNP administration. When we administered SNP nearly 4 hours prior to MK-801, no cognitive improvements were observed. Our results suggest that SNP may have intrinsic cognitive enhancing properties but is not capable of reducing MK-801-induced working memory and pattern separation impairments in the TUNL task. This study failed to mirror the results of the human pilot study that observed improved working memory following SNP administration. Further, it did not replicate previous animal studies using ketamine. Ultimately, the findings suggest that the effects of MK-801 in the TUNL task may not hold the predictive validity needed for its use in the study of SNP. In order to advance the understanding of SNP, future studies should investigate other translatable paradigms to establish validity

MiR-137-derived polygenic risk: effects on cognitive performance in patients with schizophrenia and controls

Variants at microRNA-137 (MIR137), one of the most strongly associated schizophrenia risk loci identified to date, have been associated with poorer cognitive performance. As microRNA-137 is known to regulate the expression of ~1900 other genes, including several that are independently associated with schizophrenia, we tested whether this gene set was also associated with variation in cognitive performance. Our analysis was based on an empirically derived list of genes whose expression was altered by manipulation of MIR137 expression. This list was cross-referenced with genome-wide schizophrenia association data to construct individual polygenic scores. We then tested, in a sample of 808 patients and 192 controls, whether these risk scores were associated with altered performance on cognitive functions known to be affected in schizophrenia. A subgroup of healthy participants also underwent functional imaging during memory (n=108) and face processing tasks (n=83). Increased polygenic risk within the empirically derived miR-137 regulated gene score was associated with significantly lower performance on intelligence quotient, working memory and episodic memory. These effects were observed most clearly at a polygenic threshold of P=0.05, although significant results were observed at all three thresholds analyzed. This association was found independently for the gene set as a whole, excluding the schizophrenia-associated MIR137 SNP itself. Analysis of the spatial working memory fMRI task further suggested that increased risk score (thresholded at P=10−5) was significantly associated with increased activation of the right inferior occipital gyrus. In conclusion, these data are consistent with emerging evidence that MIR137 associated risk for schizophrenia may relate to its broader downstream genetic effects

Searching for susceptibility genes for psychosis in late-onset Alzheimer's disease

A number of behavioural symptoms are commonly displayed by Alzheimer's disease (AD) sufferers. Behavioural disturbances in AD can include affective symptoms, agitation, aggression and psychosis (Burns et al. 1990a Burns et al. 1990b Burns et al. 1990c). Alois Alzheimer was the first to document psychosis in the disease bearing his name, during his description of the clinical presentation of a patient upon admission to the Frankfurt asylum in 1906 (Alzheimer 1995 Schneider and Dagerman 2004).EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Searching for susceptibility genes for psychosis in late-onset Alzheimer's disease

A number of behavioural symptoms are commonly displayed by Alzheimer's disease (AD) sufferers. Behavioural disturbances in AD can include affective symptoms, agitation, aggression and psychosis (Burns et al. 1990a Burns et al. 1990b Burns et al. 1990c). Alois Alzheimer was the first to document psychosis in the disease bearing his name, during his description of the clinical presentation of a patient upon admission to the Frankfurt asylum in 1906 (Alzheimer 1995 Schneider and Dagerman 2004).EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Searching for susceptibility genes for psychosis in late-onset Alzheimer's disease

A number of behavioural symptoms are commonly displayed by Alzheimer's disease (AD) sufferers. Behavioural disturbances in AD can include affective symptoms, agitation, aggression and psychosis (Burns et al. 1990a Burns et al. 1990b Burns et al. 1990c). Alois Alzheimer was the first to document psychosis in the disease bearing his name, during his description of the clinical presentation of a patient upon admission to the Frankfurt asylum in 1906 (Alzheimer 1995 Schneider and Dagerman 2004)