Peripheral blood gene expression profiles linked to monoamine metabolite levels in cerebrospinal fluid.

The blood-brain barrier separates circulating blood from the central nervous system (CNS). The scope of this barrier is not fully understood which limits our ability to relate biological measurements from peripheral to central phenotypes. For example, it is unknown to what extent gene expression levels in peripheral blood are reflective of CNS metabolism. In this study, we examine links between central monoamine metabolite levels and whole-blood gene expression to better understand the connection between peripheral systems and the CNS. To that end, we correlated the prime monoamine metabolites in cerebrospinal fluid (CSF) with whole-genome gene expression microarray data from blood (N=240 human subjects). We additionally applied gene-enrichment analysis and weighted gene co-expression network analyses (WGCNA) to identify modules of co-expressed genes in blood that may be involved with monoamine metabolite levels in CSF. Transcript levels of two genes were significantly associated with CSF serotonin metabolite levels after Bonferroni correction for multiple testing: THAP7 (P=2.8 × 10-8, ß=0.08) and DDX6 (P=2.9 × 10-7, ß=0.07). Differentially expressed genes were significantly enriched for genes expressed in the brain tissue (P=6.0 × 10-52). WGCNA revealed significant correlations between serotonin metabolism and hub genes with known functions in serotonin metabolism, for example, HTR2A and COMT. We conclude that gene expression levels in whole blood are associated with monoamine metabolite levels in the human CSF. Our results, including the strong enrichment of brain-expressed genes, illustrate that gene expression profiles in peripheral blood can be relevant for quantitative metabolic phenotypes in the CNS.

Genome-wide association study of NMDA receptor coagonists in human cerebrospinal fluid and plasma.

The N-methyl-D-aspartate receptor (NMDAR) coagonists glycine, D-serine and L-proline play crucial roles in NMDAR-dependent neurotransmission and are associated with a range of neuropsychiatric disorders. We conducted the first genome-wide association study of concentrations of these coagonists and their enantiomers in plasma and cerebrospinal fluid (CSF) of human subjects from the general population (N=414). Genetic variants at chromosome 22q11.2, located in and near PRODH (proline dehydrogenase), were associated with L-proline in plasma (ß=0.29; P=6.38 × 10(-10)). The missense variant rs17279437 in the proline transporter SLC6A20 was associated with L-proline in CSF (ß=0.28; P=9.68 × 10(-9)). Suggestive evidence of association was found for the D-serine plasma-CSF ratio at the D-amino-acid oxidase (DAO) gene (ß=-0.28; P=9.08 × 10(-8)), whereas a variant in SRR (that encodes serine racemase and is associated with schizophrenia) constituted the most strongly associated locus for the L-serine to D-serine ratio in CSF. All these genes are highly expressed in rodent meninges and choroid plexus, anatomical regions relevant to CSF physiology. The enzymes and transporters they encode may be targeted to further construe the nature of NMDAR coagonist involvement in NMDAR gating. Furthermore, the highlighted genetic variants may be followed up in clinical populations, for example, schizophrenia and 22q11 deletion syndrome. Overall, this targeted metabolomics approach furthers the understanding of NMDAR coagonist concentration variability and sets the stage for non-targeted CSF metabolomics projects.

Genome-wide association study of monoamine metabolite levels in human cerebrospinal fluid.

Studying genetic determinants of intermediate phenotypes is a powerful tool to increase our understanding of genotype-phenotype correlations. Metabolic traits pertinent to the central nervous system (CNS) constitute a potentially informative target for genetic studies of intermediate phenotypes as their genetic underpinnings may elucidate etiological mechanisms. We therefore conducted a genome-wide association study (GWAS) of monoamine metabolite (MM) levels in cerebrospinal fluid (CSF) of 414 human subjects from the general population. In a linear model correcting for covariates, we identified one locus associated with MMs at a genome-wide significant level (standardized ß=0.32, P=4.92 × 10(-8)), located 20 kb from SSTR1, a gene involved with brain signal transduction and glutamate receptor signaling. By subsequent whole-genome expression quantitative trait locus (eQTL) analysis, we provide evidence that this variant controls expression of PDE9A (ß=0.21; P unadjusted=5.6 × 10(-7); P corrected=0.014), a gene previously implicated in monoaminergic transmission, major depressive disorder and antidepressant response. A post hoc analysis of loci significantly associated with psychiatric disorders suggested that genetic variation at CSMD1, a schizophrenia susceptibility locus, plays a role in the ratio between dopamine and serotonin metabolites in CSF. The presented DNA and mRNA analyses yielded genome-wide and suggestive associations in biologically plausible genes, two of which encode proteins involved with glutamate receptor functionality. These findings will hopefully contribute to an exploration of the functional impact of the highlighted genes on monoaminergic transmission and neuropsychiatric phenotypes.

Seasonal variation of serotonin turnover in human cerebrospinal fluid, depressive symptoms and the role of the 5-HTTLPR.

Studying monoaminergic seasonality is likely to improve our understanding of neurobiological mechanisms underlying season-associated physiological and pathophysiological behavior. Studies of monoaminergic seasonality and the influence of the serotonin-transporter-linked polymorphic region (5-HTTLPR) on serotonin seasonality have yielded conflicting results, possibly due to lack of power and absence of multi-year analyses. We aimed to assess the extent of seasonal monoamine turnover and examined the possible involvement of the 5-HTTLPR. To determine the influence of seasonality on monoamine turnover, 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) were measured in the cerebrospinal fluid of 479 human subjects collected during a 3-year period. Cosine and non-parametric seasonal modeling were applied to both metabolites. We computed serotonin (5-HT) seasonality values and performed an association analysis with the s/l alleles of the 5-HTTLPR. Depressive symptomatology was assessed using the Beck Depression Inventory-II. Circannual variation in 5-HIAA fitted a spring-peak cosine model that was significantly associated with sampling month (P=0.0074). Season of sampling explained 5.4% (P=1.57 × 10(-7)) of the variance in 5-HIAA concentrations. The 5-HTTLPR s-allele was associated with increased 5-HIAA seasonality (standardized regression coefficient=0.12, P=0.020, N=393). 5-HIAA seasonality correlated with depressive symptoms (Spearman's rho=0.13, P=0.018, N=345). In conclusion, we highlight a dose-dependent association of the 5-HTTLPR with 5-HIAA seasonality and a positive correlation between 5-HIAA seasonality and depressive symptomatology. The presented data set the stage for follow-up in clinical populations with a role for seasonality, such as affective disorders.

Schizophrenia genetic variants are not associated with intelligence.

BACKGROUND: Schizophrenia is associated with lower pre-morbid intelligence (IQ) in addition to (pre-morbid) cognitive decline. Both schizophrenia and IQ are highly heritable traits. Therefore, we hypothesized that genetic variants associated with schizophrenia, including copy number variants (CNVs) and a polygenic schizophrenia (risk) score (PSS), may influence intelligence. METHOD: IQ was estimated with the Wechsler Adult Intelligence Scale (WAIS). CNVs were determined from single nucleotide polymorphism (SNP) data using the QuantiSNP and PennCNV algorithms. For the PSS, odds ratios for genome-wide SNP data were calculated in a sample collected by the Psychiatric Genome-Wide Association Study (GWAS) Consortium (8690 schizophrenia patients and 11 831 controls). These were used to calculate individual PSSs in our independent sample of 350 schizophrenia patients and 322 healthy controls. RESULTS: Although significantly more genes were disrupted by deletions in schizophrenia patients compared to controls (p = 0.009), there was no effect of CNV measures on IQ. The PSS was associated with disease status (R 2 = 0.055, p = 2.1 × 10-7) and with IQ in the entire sample (R 2 = 0.018, p = 0.0008) but the effect on IQ disappeared after correction for disease status. CONCLUSIONS: Our data suggest that rare and common schizophrenia-associated variants do not explain the variation in IQ in healthy subjects or in schizophrenia patients. Thus, reductions in IQ in schizophrenia patients may be secondary to other processes related to schizophrenia risk.

Region and state specific glutamate downregulation in major depressive disorder: a meta-analysis of (1)H-MRS findings.

For major depressive disorder (MDD), magnetic resonance spectroscopy ((1)H-MRS) studies of glutamate, glutamine and Glx (the composite measure of mainly glutamate and glutamine) have yielded inconclusive or seemingly inconsistent results. We therefore systematically reviewed whether in vivo concentrations of glutamate, glutamine and Glx measured with (1)H-MRS differ between MDD patients and controls. Meta-analysis including meta-regression, sensitivity, statistical heterogeneity, and publication bias analyses were conducted. Glutamate and Glx concentrations were found to be lower in the anterior cingulate cortex (ACC) in patients compared to controls (standardized mean difference (SMD) for glutamate with 95% CIs: -0.86, -1.55 to -0.17; and for Glx: -1.15, -1.86 to -0.44). In addition, Glx was decreased in all brain regions together in current episode patients (SMD: -0.62, -1.17 to -0.07). We conclude that in MDD, glutamate and possibly glutamine are downregulated primarily in the ACC and during depressive states. These results fit the central role of the ACC in depressive symptomatology and suggest that in MDD changes in glutamatergic neurotransmission are state-dependent.

An association screen of myelin-related genes implicates the chromosome 22q11 PIK4CA gene in schizophrenia.

Several lines of evidence, including expression analyses, brain imaging and genetic studies suggest that the integrity of myelin is disturbed in schizophrenia patients. In this study, we first reconstructed a pathway of 138 myelin-related genes, all involved in myelin structure, composition, development or maintenance. Then we performed a two-stage association analysis on these 138 genes using 771 single nucleotide polymorphisms (SNPs). Analysis of our data from 310 cases vs 880 controls demonstrated association of 10 SNPs from six genes. Specifically, we observed highly significant P-values for association in PIK4CA (observed P=6.1 x 10(-6)). These findings remained significant after Bonferroni correction for 771 tests. The PIK4CA gene is located in the chromosome 22q11 deletion syndrome region, which is of particular interest because it has been implicated in schizophrenia. We also report weak association of SNPs in PIK3C2G, FGF1, FGFR1, ARHGEF10 and PSAP (observed P

The PIP5K2A and RGS4 genes are differentially associated with deficit and non-deficit schizophrenia.

Several putative schizophrenia susceptibility genes have recently been reported, but it is not clear whether these genes are associated with schizophrenia in general or with specific disease subtypes. In a previous study, we found an association of the neuregulin 1 (NRG1) gene with non-deficit schizophrenia only. We now report an association study of four schizophrenia candidate genes in patients with and without deficit schizophrenia, which is characterized by severe and enduring negative symptoms. Single-nucleotide polymorphisms (SNPs) were genotyped in the DTNBP1 (dysbindin), G72/G30 and RGS4 genes, and the relatively unknown PIP5K2A gene, which is located in a region of linkage with both schizophrenia and bipolar disorder. The sample consisted of 273 Dutch schizophrenia patients, 146 of whom were diagnosed with deficit schizophrenia and 580 controls. The strongest evidence for association was found for the A-allele of SNP rs10828317 in the PIP5K2A gene, which was associated with both clinical subtypes (P = 0.0004 in the entire group; non-deficit P = 0.016, deficit P = 0.002). Interestingly, this SNP leads to a change in protein composition. In RGS4, the G-allele of the previously reported SNP RGS4-1 (single and as part of haplotypes with SNP RGS4-18) was associated with non-deficit schizophrenia (P = 0.03) but not with deficit schizophrenia (P = 0.79). SNPs in the DTNBP1 and G72/G30 genes were not significantly associated in any group. In conclusion, our data provide further evidence that specific genes may be involved in different schizophrenia subtypes and suggest that the PIP5K2A gene deserves further study as a general susceptibility gene for schizophrenia.

A whole-genome scan in 164 Dutch sib pairs with attention-deficit/hyperactivity disorder: suggestive evidence for linkage on chromosomes 7p and 15q.

A genome scan was performed on 164 Dutch affected sib pairs (ASPs) with attention-deficit/hyperactivity disorder (ADHD). All subjects were white and of Dutch descent and were phenotyped according to criteria set out in the Diagnostic and Statistical Manual Of Mental Disorders, 4th edition. Initially, a narrow phenotype was defined, in which all the sib pairs met the full ADHD criteria (117 ASPs). In a broad phenotype, additional sib pairs were included, in which one child had an autistic-spectrum disorder but also met the full ADHD criteria (164 ASPs). A set of 402 polymorphic microsatellite markers with an average intermarker distance of 10 cM was genotyped and analyzed using the Mapmaker/sibs program. Regions with multipoint maximum likelihood scores (MLSs) >1.5 in both phenotypes were fine mapped with additional markers. This genome scan indicated several regions of interest, two of which showed suggestive evidence for linkage. The most promising chromosome region was located at 15q, with an MLS of 3.54 under the broad phenotype definition. This region was previously implicated in reading disability and autism. In addition, MLSs of 3.04 and 2.05 were found for chromosome regions 7p and 9q in the narrow phenotype. Except for a region on chromosome 5, no overlap was found with regions mentioned in the only other independent genome scan in ADHD reported to date.

[Treatment of hyperthyroidism caused by Graves' disease or toxic multinodular goitre by radioiodine: over 80% cure retrospectively after one calculated dose]. / Behandeling van hyperthyreoïdie door de ziekte van Graves of toxisch multinodulair struma met jodium-131: retrospectief ruim 80% genezing na één berekende dosis.

OBJECTIVE: Assessment of the results of radioiodine therapy for hyperthyroidism one year after treatment. DESIGN: Retrospective study of patient reports and a literature search. METHOD: Data were collected from 159 patients with Graves' disease or toxic multinodular goitre who had been treated with a calculated dose of radioiodine (131I) during a four-year period (1994-1998) at the Bronovo Hospital, The Hague, the Netherlands. Percentages of hypothyroidism, euthyroidism and hyperthyroidism one year after the treatment were compared with results from the literature. RESULTS: Of the patients treated for Graves' disease 42% were hypothyroid, 38% were euthyroid and 20% were hyperthyroid one year after radioiodine therapy. For patients with toxic multinodular goitre the figures were 10%, 78% and 12% respectively. These results were comparable with those found in the literature. Two factors influenced the outcome of therapy in patients with Graves' disease: patients with persistent hyperthyroidism were on average younger and low thyroid weight increased the chance of hypothyroidism. Whether the hyperthyroidism was permanent or transient could only be established in less than half of all patients with hormone substitution after treatment, as the substitution had already been started in the first six months. CONCLUSION: One calculated dose of radioiodine can effectively cure hyperthyroidism in over 80% of the patients. It is recommended that an effort is made to discontinue radioiodine treatment after one year so as to exclude transient hypothyroidism and unjustified hormone substitution.

Efficient tumor eradication by adoptively transferred cytotoxic T-cell clones in allogeneic hosts.

Tumor-specific cytotoxic T cells (CTLs) can play an important role against cancer as illustrated by the observation that adoptive transfer of tumor-specific CTLs can mediate potent anti-tumor effects. Although such CTLs can be detected at the tumor site, relatively little is known about the mechanisms by which they enter the tumor. In this study, the role of major histocompatibility complex (MHC) class 1 molecules on vascular endothelium in the tumor in entry of, and tumor eradication by, tumor-specific CTL was investigated. Two H-2Db-restricted CTL clones recognizing peptide VNIRNCCYI on human adenovirus type 5 early region 1-(Ad5E1)-induced tumors were used to test whether CTLs were able to cross the vascular endothelium lacking the restricting MHC molecule. One CTL clone recognizes peptide VNIRNCCYI in the context of both H-2Db and H-2Dbm14 molecules. The other CTL clone recognizes this peptide only in the context of H-2Db. Adoptive transfer of these CTLs leads to eradication of Ad5E 1-induced, H-2Db-expressing tumors in B6(H-2Db+) and Bm14(H-2Db-) nude mice. Our data show that presentation of tumor-derived peptides by MHC molecules on endothelial cells of blood vessels in a tumor do not play a major role in eradication of tumors by adoptively transferred CTL in combination with interleukin-2. Moreover, our data show that successful adoptive CTL immunotherapy is possible across allogeneic barriers, without inducing severe side effects, provided the tumor expresses the MHC class 1-peptide complex recognized by the CTLs.