The single-cell eQTLGen consortium.

In recent years, functional genomics approaches combining genetic information with bulk RNA-sequencing data have identified the downstream expression effects of disease-associated genetic risk factors through so-called expression quantitative trait locus (eQTL) analysis. Single-cell RNA-sequencing creates enormous opportunities for mapping eQTLs across different cell types and in dynamic processes, many of which are obscured when using bulk methods. Rapid increase in throughput and reduction in cost per cell now allow this technology to be applied to large-scale population genetics studies. To fully leverage these emerging data resources, we have founded the single-cell eQTLGen consortium (sc-eQTLGen), aimed at pinpointing the cellular contexts in which disease-causing genetic variants affect gene expression. Here, we outline the goals, approach and potential utility of the sc-eQTLGen consortium. We also provide a set of study design considerations for future single-cell eQTL studies.

An epigenome-wide association study meta-analysis of educational attainment.

The epigenome is associated with biological factors, such as disease status, and environmental factors, such as smoking, alcohol consumption and body mass index. Although there is a widespread perception that environmental influences on the epigenome are pervasive and profound, there has been little evidence to date in humans with respect to environmental factors that are biologically distal. Here we provide evidence on the associations between epigenetic modifications-in our case, CpG methylation-and educational attainment (EA), a biologically distal environmental factor that is arguably among the most important life-shaping experiences for individuals. Specifically, we report the results of an epigenome-wide association study meta-analysis of EA based on data from 27 cohort studies with a total of 10 767 individuals. We find nine CpG probes significantly associated with EA. However, robustness analyses show that all nine probes have previously been found to be associated with smoking. Only two associations remain when we perform a sensitivity analysis in the subset of never-smokers, and these two probes are known to be strongly associated with maternal smoking during pregnancy, and thus their association with EA could be due to correlation between EA and maternal smoking. Moreover, the effect sizes of the associations with EA are far smaller than the known associations with the biologically proximal environmental factors alcohol consumption, body mass index, smoking and maternal smoking during pregnancy. Follow-up analyses that combine the effects of many probes also point to small methylation associations with EA that are highly correlated with the combined effects of smoking. If our findings regarding EA can be generalized to other biologically distal environmental factors, then they cast doubt on the hypothesis that such factors have large effects on the epigenome.

The Chronic Effects of Neurotrauma Consortium (CENC) multi-centre observational study: Description of study and characteristics of early participants.

PRIMARY OBJECTIVES: To establish and comprehensively evaluate a large cohort of US veterans who served in recent military conflicts in order to better understand possible chronic and late-life effects of mild traumatic brain injury (mTBI), including those that may stem from neurodegeneration. RESEARCH DESIGN: Cross-sectional and prospective longitudinal. METHODS AND PROCEDURES: Inclusion criteria are prior combat exposure and deployment(s) in Operation Enduring Freedom, Operation Iraqi Freedom or one of their follow-on conflicts (collectively OEF/OIF). Effects of mTBI will be assessed by enrolling participants across the entire spectrum of mTBI, from entirely negative to many mTBIs. Longitudinal assessments consist of in-person comprehensive testing at least every 5 years, with interval annual telephonic testing. The primary outcome is the composite score on the NIH Toolbox neuropsychological test battery. Assessments also include structured interviews, questionnaires, traditional neuropsychological testing, motor, sensory and vestibular functions, neuroimaging, electrophysiology, genotypes and biomarkers. MAIN OUTCOMES AND RESULTS: The authors fully describe the study methods and measures and report demographic and exposure characteristics from the early portion of the cohort of OEF/OIF veterans. CONCLUSIONS: This centrepiece observational study of the Chronic Effects of Neurotrauma Consortium (CENC) is successfully launched and, within several years, should provide fertile data to begin investigating its aims.

Prevalence of mental health conditions after military blast exposure, their co-occurrence, and their relation to mild traumatic brain injury.

PRIMARY OBJECTIVES: To measure common psychiatric conditions after military deployment with blast exposure and test relationships to post-concussion syndrome (PCS) symptoms and mild traumatic brain injury (mTBI) history. RESEARCH DESIGN: Cross-sectional. METHODS AND PROCEDURES: Service members or Veterans (n = 107) within 2 years of blast exposure underwent structured interviews for mTBI, post-traumatic stress disorder (PTSD) and multiple mood and anxiety diagnoses. MAIN OUTCOMES AND RESULTS: MTBI history and active PTSD were both common, additionally 61% had at least one post-deployment mood or anxiety disorder episode. Psychiatric diagnoses had a high degree of comorbidity. Most dramatically, depression was 43-times (95% CI = 11-165) more likely if an individual had PTSD. PCS symptoms were greater in those with post-deployment PTSD or mood diagnosis. However, neither mTBI nor blast exposure history had an effect on the odds of having PTSD, mood or anxiety condition. CONCLUSIONS: These findings support that psychiatric conditions beyond PTSD are common after military combat deployment with blast exposure. They also highlight the non-specificity of post-concussion type symptoms. While some researchers have implicated mTBI history as a contributor to post-deployment mental health conditions, no clear association was found. This may partly be due to the more rigorous method of retrospective mTBI diagnosis determination.

Cancer spectrum and frequency among children with Noonan, Costello, and cardio-facio-cutaneous syndromes.

BACKGROUND: Somatic mutations affecting components of the Ras-MAPK pathway are a common feature of cancer, whereas germline Ras pathway mutations cause developmental disorders including Noonan, Costello, and cardio-facio-cutaneous syndromes. These 'RASopathies' also represent cancer-prone syndromes, but the quantitative cancer risks remain unknown. METHODS: We investigated the occurrence of childhood cancer including benign and malignant tumours of the central nervous system in a group of 735 individuals with germline mutations in Ras signalling pathway genes by matching their information with the German Childhood Cancer Registry. RESULTS: We observed 12 cases of cancer in the entire RASopathy cohort vs 1.12 expected (based on German population-based incidence rates). This corresponds to a 10.5-fold increased risk of all childhood cancers combined (standardised incidence ratio (SIR)=10.5, 95% confidence interval=5.4-18.3). The specific cancers included juvenile myelomonocytic leukaemia=4; brain tumour=3; acute lymphoblastic leukaemia=2; rhabdomyosarcoma=2; and neuroblastoma=1. The childhood cancer SIR in Noonan syndrome patients was 8.1, whereas that for Costello syndrome patients was 42.4. CONCLUSIONS: These data comprise the first quantitative evidence documenting that the germline mutations in Ras signalling pathway genes are associated with increased risks of both childhood leukaemia and solid tumours.

Determining the association between adipokine expression in multiple tissues and phenotypic features of non-alcoholic fatty liver disease in obesity.

OBJECTIVES: Non-alcoholic fatty liver disease (NAFLD) is an obesity-associated disease, and in obesity adipokines are believed to be involved in the development of NAFLD. However, it is still not clear whether adipokines in the liver and/or adipose tissues can be related to the development of specific characteristics of NAFLD, such as steatosis and inflammation. We aimed to address this question by simultaneously examining the adipokine expression in three tissue types in obese individuals. METHODS: We enrolled 93 severely obese individuals with NAFLD, varying from simple steatosis to severe non-alcoholic steatohepatitis. Their expression of 48 adipokines in the liver, visceral and subcutaneous adipose tissue (SAT) was correlated to their phenotypic features of NAFLD. We further determined whether the correlations were tissue specific and/or independent of covariates, including age, sex, obesity, insulin resistance and type 2 diabetes (T2D). RESULTS: The expression of adipokines showed a liver- and adipose tissue-specific pattern. We identified that the expression of leptin, angiopoietin 2 (ANGPT2) and chemerin in visceral adipose tissue (VAT) was associated with different NAFLD features, including steatosis, ballooning, portal and lobular inflammation. In addition, the expression of tumor necrosis factor (TNF), plasminogen activator inhibitor type 1 (PAI-1), insulin-like growth factor 1 (somatomedin C) (IGF1) and chemokine (C-X-C motif) ligand 10 (CXCL10) in the liver tissue and the expression of interleukin 1 receptor antagonist (IL1RN) in both the liver and SAT were associated with NAFLD features. The correlations between ANGPT2 and CXCL10, and NAFLD features were dependent on insulin resistance and T2D, but for the other genes the correlation with at least one NAFLD feature remained significant after correcting for the covariates. CONCLUSIONS: Our results suggest that in obese individuals, VAT-derived leptin and chemerin, and hepatic expression of TNF, IGF1, IL1RN and PAI-1 are involved in the development of NAFLD features. Further, functional studies are warranted to establish a causal relationship.

HLA-DRB1*03:01 and HLA-DRB1*04:01 modify the presentation and outcome in autoimmune hepatitis type-1.

The classical human leukocyte antigen (HLA)-DRB1*03:01 and HLA-DRB1*04:01 alleles are established autoimmune hepatitis (AIH) risk alleles. To study the immune-modifying effect of these alleles, we imputed the genotypes from genome-wide association data in 649 Dutch AIH type-1 patients. We therefore compared the international AIH group (IAIHG) diagnostic scores as well as the underlying clinical characteristics between patients positive and negative for these HLA alleles. Seventy-five percent of the AIH patients were HLA-DRB1*03:01/HLA-DRB1*04:01 positive. HLA-DRB1*03:01/HLA-DRB1*04:01-positive patients had a higher median IAIHG score than HLA-DRB1*03:01/HLA-DRB1*04:01-negative patients (P<0.001). We did not observe associations between HLA alleles and alanine transaminase levels (HLA-DRB1*03:01: P=0.2; HLA-DRB1*04:01; P=0.5); however, HLA-DRB1*03:01 was independently associated with higher immunoglobulin G levels (P=0.04). The HLA-DRB1*04:01 allele was independently associated with presentation at older age (P=0.03) and a female predominance (P=0.04). HLA-DRB1*03:01-positive patients received immunosuppressive medication and liver transplantation. In conclusion, the HLA-DRB1*03:01 and HLA-DRB1*04:01 alleles are both independently associated with the aggregate diagnostic IAIHG score in type-1 AIH patients, but are not essential for AIH development. HLA-DRB1*03:01 is the strongest genetic modifier of disease severity in AIH.

ATR inhibition preferentially targets homologous recombination-deficient tumor cells.

Homologous recombination (HR) is required for faithful repair of double-strand DNA breaks. Defects in HR repair cause severe genomic instability and challenge cellular viability. Paradoxically, various cancers are HR defective and have apparently acquired characteristics to survive genomic instability. We aimed to identify these characteristics to uncover therapeutic targets for HR-deficient cancers. Cytogenetic analysis of 1143 ovarian cancers showed that the degree of genomic instability was correlated to amplification of replication checkpoint genes ataxia telangiectasia and Rad3-related kinase (ATR) and CHEK1. To test whether genomic instability leads to increased reliance on replication checkpoint signaling, we inactivated Rad51 to model HR-related genomic instability. Rad51 inactivation caused defective HR repair and induced aberrant replication dynamics. Notably, inhibition of Rad51 led to increased ATR/checkpoint kinase-1 (Chk1)-mediated replication stress signaling. Importantly, inhibition of ATR or Chk1 preferentially killed HR-deficient cancer cells. Combined, our data show that defective HR caused by Rad51 inhibition results in differential sensitivity for ATR and Chk1 inhibitors, implicating replication checkpoint kinases as potential drug targets for HR-defective cancers.

A meta-analysis of Hodgkin lymphoma reveals 19p13.3 TCF3 as a novel susceptibility locus.

Recent genome-wide association studies (GWAS) of Hodgkin lymphoma (HL) have identified associations with genetic variation at both HLA and non-HLA loci; however, much of heritable HL susceptibility remains unexplained. Here we perform a meta-analysis of three HL GWAS totaling 1,816 cases and 7,877 controls followed by replication in an independent set of 1,281 cases and 3,218 controls to find novel risk loci. We identify a novel variant at 19p13.3 associated with HL (rs1860661; odds ratio (OR)=0.81, 95% confidence interval (95% CI) = 0.76-0.86, P(combined) = 3.5 × 10(-10)), located in intron 2 of TCF3 (also known as E2A), a regulator of B- and T-cell lineage commitment known to be involved in HL pathogenesis. This meta-analysis also notes associations between previously published loci at 2p16, 5q31, 6p31, 8q24 and 10p14 and HL subtypes. We conclude that our data suggest a link between the 19p13.3 locus, including TCF3, and HL risk.

Genetic variants in the region of the C1q genes are associated with rheumatoid arthritis.

Rodent models for arthritis implicate a role for complement in disease development and progression. In humans, complement deposition has been observed in inflamed synovia of rheumatoid arthritis (RA) patients. In this study we analysed whether genetic variants of complement component C1q predispose to RA. We genotyped single nucleotide polymorphisms (SNPs) in and around the C1q genes, C1qA, C1qB and C1qC, in a Dutch set of 845 RA cases and 1046 controls. Replication was sought in a sample set from North America (868 cases/1193 controls), and a meta-analysis was performed in a combined samples set of 8000 cases and 23 262 controls of European descent. We determined C1q serum levels in relation to C1q genotypes. In the discovery phase, five of the 13 SNPs tested in the C1q genes showed a significant association with RA. Additional analysis of the genomic area around the C1q genes revealed that the strongest associating SNPs were confined to the C1q locus. Within the C1q locus we observed no additional signal independent of the strongest associating SNP, rs292001 [odds ratio (OR) = 0·72 (0·58-0·88), P = 0·0006]. The variants of this SNP were associated with different C1q serum levels in healthy controls (P = 0·006). Interestingly, this SNP was also associated significantly in genome-wide association studies (GWAS) from the North American Rheumatoid Arthritis Consortium study, confirming the association with RA [OR = 0·83 (0·69-1·00), P = 0·043]. Combined analysis, including integrated data from six GWAS studies, provides support for the genetic association. Genetic variants in C1q are correlated with C1q levels and may be a risk for the development of RA.

A genetic variant in granzyme B is associated with progression of joint destruction in rheumatoid arthritis.

OBJECTIVE: Genetic factors account for an estimated 45-58% of the variance in joint destruction in rheumatoid arthritis (RA). The serine proteinase granzyme B induces target cell apoptosis, and several in vitro studies suggest that granzyme B is involved in apoptosis of chondrocytes. Serum levels of granzyme B are increased in RA and are also associated with radiographic erosions. The aim of this study was to investigate GZMB as a candidate gene accounting for the severity of joint destruction in RA. METHODS: A total of 1,418 patients with 4,885 radiograph sets of the hands and feet from 4 independent cohorts were studied. First, explorative analyses were performed in 600 RA patients in the Leiden Early Arthritis Clinic cohort. Fifteen single-nucleotide polymorphisms (SNPs) tagging GZMB were tested. Significantly associated SNPs were genotyped in data sets representing patients from the Groningen, Sheffield, and Lund cohorts. In each data set, the relative increase in the annual rate of progression in the presence of a genotype was assessed. Data were summarized in a meta-analysis. The association of GZMB with the RNA expression level of the GZMB genomic region was tested by mapping expression quantitative trait loci (QTLs) on 1,469 whole blood samples. RESULTS: SNP rs8192916 was significantly associated with the rate of joint destruction in the first cohort and in the meta-analysis of all data sets. Patients homozygous for the minor allele of rs8192916 had a higher rate of joint destruction per year compared with other patients (P = 7.8 × 10(-4)). Expression QTL of GZMB identified higher expression in the presence of the minor allele of rs8192916 (P = 2.27 × 10(-5)). CONCLUSION: SNP rs8192916 located in GZMB is associated with the progression of joint destruction in RA as well as with RNA expression in whole blood.

Relationships between platelet MAO-B activity and personality styles in acute and weight-recovered young patients with anorexia nervosa.

OBJECTIVE: Previous studies have shown relationships between personality styles and markers of serotonergic functioning, but data on patients with anorexia nervosa (AN) are scarce. METHODS: The personality styles and disorder inventory was administered to 47 acute patients with anorexia nervosa (acAN), 27 weight-recovered patients (recAN) and 72 healthy controls (HC) aged between 14 and 21 years. Platelet monoamine oxidase (MAO-B) activity was assayed with [14C]-ß-phenylethylamine as substrate. RESULTS: AcAN had significant elevated scores on 9 of the 14 personality style subscales when compared to HC, whereas recAN were largely normal. Platelet MAO-B activity and "ambitious/narcissistic" scores correlated negatively in acAN. In recAN we found positive correlations between MAO-B and personality subscores. CONCLUSIONS: The inverse relationship between a cluster B personality style and MAO-B activity in acAN is in accordance with studies in other patient populations. In contrast, positive associations between problematic personality styles and MAO-B activity in recAN combined with the overall decreased MAO-B activity in this group adds to the existing evidence suggesting a general dysfunction of the serotonergic system as a trait marker for AN.

Celiac disease: moving from genetic associations to causal variants.

Genome-wide association studies are providing insight into the genetic basis of common complex diseases: more than 1150 genetic loci [2165 unique single nucleotide polymorphisms (SNPs)] have recently been associated to 159 complex diseases. The hunt for genes contributing to immune-related diseases has been particularly successful in celiac disease, for example, with 27 genome-wide significantly associated loci identified so far. One of the current challenges is how to move from a genetic association with a disease to finding disease-associated genes and causal variants, as a step towards understanding the underlying disease process. About 50% of disease-associated SNPs affect the expression of nearby genes (so-called expression quantitative traits loci or eQTLs) and these can provide clues for finding causal variants. Although eQTLs can be useful, fine mapping and sequencing are required to refine the association signal. Ultimately, sophisticated study designs will be needed to find the causal variants involved in complex diseases. In this review, we use celiac disease as an example to describe the different aspects that need to be considered on the path from genetic association to disease-causing variants.

Cost-of-illness of rheumatoid arthritis and ankylosing spondylitis.

OBJECTIVE: To assess, quantify and summarise the cost of illness of rheumatoid arthritis (RA) and ankylosing spondylitis (AS) from the societal perspective. METHODS: Original studies reporting costs of RA or AS were searched systematically. Both cost-of-illness studies and economic evaluations of therapies were included. Studies were appraised for patient and study characteristics, type of costs and actual costs. Reported costs were aggregated by cost categories and overall mean costs were summarised by cost domain (healthcare, patient and family, and productivity costs). RESULTS: Overall mean costs of RA (euro14,906 per year) were above that of AS (euro9,374 per year), while the relative distribution of costs over cost domains was approximately similar. For both diseases, productivity costs based on the human cost approach were 3 to 10 times higher than the friction costs and accounted for more than half the total costs of both diseases. CONCLUSION: Productivity costs constitute the largest part of the total cost-off-illness of RA and AS reflecting the high burden of the disease on work participation. Although total and direct costs of illness in RA were higher than in AS, the average age of AS patients was 10 years lower and therefore, lifetime costs associated with AS may actually be equal or higher.

Coeliac disease-associated risk variants in TNFAIP3 and REL implicate altered NF-kappaB signalling.

OBJECTIVE: Our previous coeliac disease genome-wide association study (GWAS) implicated risk variants in the human leucocyte antigen (HLA) region and eight novel risk regions. To identify more coeliac disease loci, we selected 458 single nucleotide polymorphisms (SNPs) that showed more modest association in the GWAS for genotyping and analysis in four independent cohorts. DESIGN: 458 SNPs were assayed in 1682 cases and 3258 controls from three populations (UK, Irish and Dutch). We combined the results with the original GWAS cohort (767 UK cases and 1422 controls); six SNPs showed association with p<1 x 10(-04) and were then genotyped in an independent Italian coeliac cohort (538 cases and 593 controls). RESULTS: We identified two novel coeliac disease risk regions: 6q23.3 (OLIG3-TNFAIP3) and 2p16.1 (REL), both of which reached genome-wide significance in the combined analysis of all 2987 cases and 5273 controls (rs2327832 p = 1.3 x 10(-08), and rs842647 p = 5.2 x 10(-07)). We investigated the expression of these genes in the RNA isolated from biopsies and from whole blood RNA. We did not observe any changes in gene expression, nor in the correlation of genotype with gene expression. CONCLUSIONS: Both TNFAIP3 (A20, at the protein level) and REL are key mediators in the nuclear factor kappa B (NF-kappaB) inflammatory signalling pathway. For the first time, a role for primary heritable variation in this important biological pathway predisposing to coeliac disease has been identified. Currently, the HLA risk factors and the 10 established non-HLA risk factors explain approximately 40% of the heritability of coeliac disease.

Platelet monoamine oxidase activity in underweight and weight-recovered females with anorexia nervosa.

INTRODUCTION: Central serotonergic pathways may play an important role in the etiology of anorexia nervosa (AN). Although platelet monoamine oxidase activity (MAO-B) has been proposed as an index of cerebral serotonin activity, studies in patients with AN are scarce. METHODS: Platelet MAO-B activity was determined in 59 acutely underweight AN patients (acAN, aged 14-29 years, BMI=15.2+/-1.4), 35 weight-recovered AN patients (recAN, aged 15-29, BMI=20.8+/-2.2) and 59 healthy control women (HCW, aged 14-26, BMI=21.6+/-2.1). Plasma leptin served as an indicator of malnutrition. Results were compared by ANCOVA controlling for confounding variables. RESULTS: Platelet MAO-B activity in acAN patients (5.2+/-1.4 nmol/10 (9)pltx15 min) was similar to HCW (5.5+/-1.9) but significantly lower in recAN patients (4.4+/-1.5). BMI and leptin showed a significant negative correlation with MAO-B activity in AN patients, but not in HCW. DISCUSSION: Our results highlight the importance of malnutrition for the interpretation of abnormalities in neurotransmitter systems in AN. Whether low MAO-B activity in weight-recovered AN patients indicates a premorbid trait or a secondary change due to recovery remains to be elucidated.

The molecular mechanism of the inhibition by licofelone of the biosynthesis of 5-lipoxygenase products.

BACKGROUND AND PURPOSE: Licofelone is a dual inhibitor of the cyclooxygenase and 5-lipoxygenase (5-LO) pathway, and has been developed for the treatment of inflammatory diseases. Here, we investigated the molecular mechanisms underlying the inhibition by licofelone of the formation of 5-LO products. EXPERIMENTAL APPROACH: The efficacy of licofelone to inhibit the formation of 5-LO products was analysed in human isolated polymorphonuclear leukocytes (PMNL) or transfected HeLa cells, as well as in cell-free assays using respective cell homogenates or purified recombinant 5-LO. Moreover, the effects of licofelone on the subcellular redistribution of 5-LO were studied. KEY RESULTS: Licofelone potently blocked synthesis of 5-LO products in Ca(2+)-ionophore-activated PMNL (IC(50)=1.7 microM) but was a weak inhibitor of 5-LO activity in cell-free assays (IC(50)>>10 microM). The structures of licofelone and MK-886, an inhibitor of the 5-LO-activating protein (FLAP), were superimposable. The potencies of both licofelone and MK-886 in ionophore-activated PMNL were impaired upon increasing the concentration of arachidonic acid, or under conditions where 5-LO product formation was evoked by genotoxic, oxidative or hyperosmotic stress. Furthermore, licofelone prevented nuclear redistribution of 5-LO in ionophore-activated PMNL, as had been observed for FLAP inhibitors. Finally, licofelone as well as MK-886 caused only moderate inhibition of the synthesis of 5-LO products in HeLa cells, unless FLAP was co-transfected. CONCLUSIONS AND IMPLICATIONS: Our data suggest that the potent inhibition of the biosynthesis of 5-LO products by licofelone requires an intact cellular environment and appears to be due to interference with FLAP.

[High time for a total ban on smoking in the hotel, restaurant and catering industry: the arguments are mounting]. / Hoogste tijd voor een rookvrije horeca: de argumenten stapelen zich op.

Active and passive smoking are well-known causes of disease, including respiratory and cardiovascular disease and cancer. In 2004 the Dutch government introduced new legislation to regulate smoking in the workplace. However, smoking is still allowed in hotels, bars and restaurants, despite the fact that two-thirds of the Dutch population support a total ban on smoking in public places. Several other European countries and American states have banned smoking in public places. Studies performed in these regions show that the new smoking regulations have had no negative economic effects. Moreover, various studies have shown that smoking bans have a positive impact on public health, even in the short-term, including a significant decrease in respiratory and cardiovascular disease. There is therefore no reason to continue to exclude hotels, bars and restaurants from the smoking ban in all public places in The Netherlands.

Peripheral serotonergic markers in acutely suicidal patients. 1. Comparison of serotonergic platelet measures between suicidal individuals, nonsuicidal patients with major depression and healthy subjects.

BACKGROUND: A robust association between "suicidality" and deficits of the serotoninergic neurotransmission has been claimed in the past. However, many studies having investigated the relationship between suicidality and peripheral indicators of serotoninergic neurotransmission suffer from considering only one or a very small number of potentially useful serotoninergic parameters, whereas a synoptic multidimensional approach appears to be more appropriate. Furthermore, the psychiatric context within which suicidal behaviour occurs should be considered when interpreting biochemical findings of patients with suicidal ideation and suicide attempts. METHODS: In the present study 5 peripheral serotonergic markers, (platelet 5HT concentration, 5HT uptake activity, 5HT(2A) receptor binding characteristics, MAO-B activity and tryptophan concentration in plasma) were assessed simultaneously. Of the 60 acutely suicidal inpatients (ICD-10: F43.xx, n = 52; F31/32/33, n = 8), 45 were suicide attempters. Data of 28 nonsuicidal patients with major depression (F31, n = 4; F32, n = 14; F33, n = 10) and 123 healthy volunteers represented the control groups. RESULTS: Mean platelet 5HT concentration was significantly lower in suicidal inpatients when compared to nonsuicidal depressed patients, but did not differ from the figure in healthy subjects. Nonsuicidal depressed patients showed significantly higher mean platelet-5HT concentration than healthy controls. Mean V(max) of 5HT uptake in washed platelets, but not in platelet-rich plasma, was significantly higher in suicidal patients than in healthy controls, not, however, when compared to nonsuicidal depressed patients. Mean K(D) for the platelet 5HT(2A) receptor and MAO-B activity were significantly lower in suicidal patients as compared to nonsuicidal depressed patients and healthy controls. The observed differences in peripheral serotonergic markers between groups are partially due to a significant gender effect. A lower MAO-B activity was observed only in suicidal females, while the higher V(max) of 5HT uptake in washed platelets of suicidal patients was due to suicidal males. CONCLUSIONS: In view of conflicting observations made by other authors and the present findings on suicidal patients with adjustment disorder it remains doubtful whether and if so to which extent platelet studies can provide valid information on serotonergic mechanisms related to suicidal behaviour.