Deficiency of FANCD2-associated nuclease KIAA1018/FAN1 sensitizes cells to interstrand crosslinking agents.

Cytotoxicity of cisplatin and mitomycin C (MMC) is ascribed largely to their ability to generate interstrand crosslinks (ICLs) in DNA, which block the progression of replication forks. The processing of ICLs requires the Fanconi anemia (FA) pathway, excision repair, and translesion DNA synthesis (TLS). It also requires homologous recombination (HR), which repairs double-strand breaks (DSBs) generated by cleavage of the blocked replication forks. Here we describe KIAA1018, an evolutionarily conserved protein that has an N-terminal ubiquitin-binding zinc finger (UBZ) and a C-terminal nuclease domain. KIAA1018 is a 5'-->3' exonuclease and a structure-specific endonuclease that preferentially incises 5' flaps. Like cells from FA patients, human cells depleted of KIAA1018 are sensitized to ICL-inducing agents and display chromosomal instability. The link of KIAA1018 to the FA pathway is further strengthened by its recruitment to DNA damage through interaction of its UBZ domain with monoubiquitylated FANCD2. We therefore propose to name KIAA1018 FANCD2-associated nuclease, FAN1.

Increased suicide risk among younger women in winter during full moon in northern Europe. An artifact or a novel finding?

Available evidence suggests that there is no effect of moon phases on suicidal behavior. However, a Finnish study recently reported elevated suicide rates during full-moon, but only among premenopausal women and only in winter. This could not be replicated in an Austrian study and stirred a discussion about whether the Finnish finding was false-positive or if there are unaccounted moderator variables differing between Finland and Austria. The goal of the present study was to provide another replication with data from Sweden, which is geographically more comparable to Finland than Austria. We also investigated the discussed moderator variables latitude and nightly artificial brightness. There were 48,537 suicides available for analysis. The fraction of suicides during the full-moon quarter in winter did not differ significantly from the expected 25% among premenopausal women (23.3%) and in the full sample (24.7%). The incidence risk ratios for full moon quarter in Poisson regression models were 0.96 (95% CI: 0.90-1.02) for premenopausal women and 1.01 (95% CI: 0.99-1.04) for the full sample. According to Bayes-factor analysis, the evidence supports the null-hypothesis (no association) over the alternative hypothesis (some association). We found similar results when we split the data by latitude and artificial nightly brightness, respectively. In line with the Austrian study, there was no increase of suicides in Sweden among premenopausal women in winter during full-moon. The results from the Finnish study are likely false positive, perhaps resulting from problematic but common research and publication practices, which we discuss.

The serotonin theory of depression: a systematic umbrella review of the evidence.

The serotonin hypothesis of depression is still influential. We aimed to synthesise and evaluate evidence on whether depression is associated with lowered serotonin concentration or activity in a systematic umbrella review of the principal relevant areas of research. PubMed, EMBASE and PsycINFO were searched using terms appropriate to each area of research, from their inception until December 2020. Systematic reviews, meta-analyses and large data-set analyses in the following areas were identified: serotonin and serotonin metabolite, 5-HIAA, concentrations in body fluids; serotonin 5-HT1A receptor binding; serotonin transporter (SERT) levels measured by imaging or at post-mortem; tryptophan depletion studies; SERT gene associations and SERT gene-environment interactions. Studies of depression associated with physical conditions and specific subtypes of depression (e.g. bipolar depression) were excluded. Two independent reviewers extracted the data and assessed the quality of included studies using the AMSTAR-2, an adapted AMSTAR-2, or the STREGA for a large genetic study. The certainty of study results was assessed using a modified version of the GRADE. We did not synthesise results of individual meta-analyses because they included overlapping studies. The review was registered with PROSPERO (CRD42020207203). 17 studies were included: 12 systematic reviews and meta-analyses, 1 collaborative meta-analysis, 1 meta-analysis of large cohort studies, 1 systematic review and narrative synthesis, 1 genetic association study and 1 umbrella review. Quality of reviews was variable with some genetic studies of high quality. Two meta-analyses of overlapping studies examining the serotonin metabolite, 5-HIAA, showed no association with depression (largest n = 1002). One meta-analysis of cohort studies of plasma serotonin showed no relationship with depression, and evidence that lowered serotonin concentration was associated with antidepressant use (n = 1869). Two meta-analyses of overlapping studies examining the 5-HT1A receptor (largest n = 561), and three meta-analyses of overlapping studies examining SERT binding (largest n = 1845) showed weak and inconsistent evidence of reduced binding in some areas, which would be consistent with increased synaptic availability of serotonin in people with depression, if this was the original, causal abnormaly. However, effects of prior antidepressant use were not reliably excluded. One meta-analysis of tryptophan depletion studies found no effect in most healthy volunteers (n = 566), but weak evidence of an effect in those with a family history of depression (n = 75). Another systematic review (n = 342) and a sample of ten subsequent studies (n = 407) found no effect in volunteers. No systematic review of tryptophan depletion studies has been performed since 2007. The two largest and highest quality studies of the SERT gene, one genetic association study (n = 115,257) and one collaborative meta-analysis (n = 43,165), revealed no evidence of an association with depression, or of an interaction between genotype, stress and depression. The main areas of serotonin research provide no consistent evidence of there being an association between serotonin and depression, and no support for the hypothesis that depression is caused by lowered serotonin activity or concentrations. Some evidence was consistent with the possibility that long-term antidepressant use reduces serotonin concentration.

Post-transcriptional control of executioner caspases by RNA-binding proteins.

Caspases are key components of apoptotic pathways. Regulation of caspases occurs at several levels, including transcription, proteolytic processing, inhibition of enzymatic function, and protein degradation. In contrast, little is known about the extent of post-transcriptional control of caspases. Here, we describe four conserved RNA-binding proteins (RBPs)-PUF-8, MEX-3, GLD-1, and CGH-1-that sequentially repress the CED-3 caspase in distinct regions of the Caenorhabditis elegans germline. We demonstrate that GLD-1 represses ced-3 mRNA translation via two binding sites in its 3' untranslated region (UTR), thereby ensuring a dual control of unwanted cell death: at the level of p53/CEP-1 and at the executioner caspase level. Moreover, we identified seven RBPs that regulate human caspase-3 expression and/or activation, including human PUF-8, GLD-1, and CGH-1 homologs PUM1, QKI, and DDX6. Given the presence of unusually long executioner caspase 3' UTRs in many metazoans, translational control of executioner caspases by RBPs might be a strategy used widely across the animal kingdom to control apoptosis.

Prevalence, trends, and individual patterns of long-term antidepressant medication use in the adult Swiss general population.

PURPOSE: Antidepressant use has increased in many European countries, mostly driven by longer treatment duration. The aim of this study was to provide prevalence rates of long-term users of antidepressants for the Swiss population over the last decade and to investigate associated factors for longer use. METHODS: We examined the prevalence rates of individuals with at least one prescription for antidepressants using longitudinal health claims data for 2013 to 2021. We defined short- (< one year), medium- (one-two years), and long-term users (> two years) for 2015 to 2019. We applied a binary logistic regression model to investigate the effects of population (gender, age, area of living, language, health insurance plan, and nursing home) and treatment characteristics (psychiatric or psychotherapeutic care) on long-term compared to short- and medium-term users in 2019. RESULTS: In 2021, 9% of the Swiss population (n = 770,698) received at least one antidepressant prescription, which remained stable since 2013. In 2019, the proportion of long-term users was 57.4%, with steady increase since 2015. The proportion of medium- and short-term users has decreased. Older age, being a woman, living in an urban area, living in a nursing home, being enrolled in a standard care plan, and receiving psychiatric or psychotherapeutic care were factors positively associated with being a long-term user. CONCLUSION: The proportion of long-term users in Switzerland is high and steadily increasing. Given the ongoing debate about the confounding effects of relapse and withdrawal, more research is needed to investigate longer use of antidepressants that could indicate overprescribing.

Patterns of internalizing symptoms and disability functioning in children and adolescents.

Despite findings from previous studies, there is still little consistent knowledge regarding the co-occurrence patterns of somatic, depressive and anxiety symptoms in childhood and adolescence. Moreover, functional disability due to somatic symptoms at different concomitant levels of depression and anxiety is understudied. The present study examined the co-occurrence patterns of somatic symptoms and symptoms of depression and anxiety, in children and adolescents using two-step cluster analysis. Differences in functional disability due to somatic symptoms were tested with ANCOVA controlling for gender and age. The sample comprised 1127 Italian children and adolescents (48.7% males, n = 549) aged 8-16 years (Mage = 11.7, SD = 2.37). Data were collected using the Children Somatization Inventory-24, the Children Depression Inventory, the Screen for Child Anxiety Related Emotional Disorders, and the Functional Disability Inventory. A four-cluster solution based on the co-occurrence of internalizing symptoms best fit the data. The four clusters were labelled as follows: cluster 1: "High somatic symptoms and average depression/anxiety"; cluster 2: "High somatic symptoms and high depression/anxiety"; cluster 3: "Average somatic symptoms and above average depression/anxiety"; and cluster 4: "Low somatic symptoms and low depression/anxiety". Significant differences between the four groups according to gender and age were shown. Participants with high levels of somatic, depressive, and anxiety symptoms reported greater functional disability due to somatic symptoms than the other three groups. Our findings indicate that children and adolescents who demonstrate high symptoms of depression and anxiety also reported higher levels of disability in daily life due to somatic symptoms.

Cognitive function in association with high estradiol levels resulting from fertility treatment.

The putative association between hormones and cognitive performance is controversial. While there is evidence that estradiol plays a neuroprotective role, hormone treatment has not been shown to improve cognitive performance. Current research is flawed by the evaluation of combined hormonal effects throughout the menstrual cycle or in the menopausal transition. The stimulation phase of a fertility treatment offers a unique model to study the effect of estradiol on cognitive function. This quasi-experimental observational study is based on data from 44 women receiving IVF in Zurich, Switzerland. We assessed visuospatial working memory, attention, cognitive bias, and hormone levels at the beginning and at the end of the stimulation phase of ovarian superstimulation as part of a fertility treatment. In addition to inter-individual differences, we examined intra-individual change over time (within-subject effects). The substantial increases in estradiol levels resulting from fertility treatment did not relate to any considerable change in cognitive functioning. As the tests applied represent a broad variety of cognitive functions on different levels of complexity and with various brain regions involved, we can conclude that estradiol does not show a significant short-term effect on cognitive function.

Did the introduction and increased prescribing of antidepressants lead to changes in long-term trends of suicide rates?

BACKGROUND: Ecological studies have explored associations between suicide rates and antidepressant prescriptions in the population, but most of them are limited as they analyzed short-term correlations that may be spurious. The aim of this long-term study was to examine whether trends in suicide rates changed in three European countries when the first antidepressants were introduced in 1960 and when prescription rates increased steeply after 1990 with the introduction of the serotonin reuptake inhibitors (SSRIs). METHODS: Data were extracted from the WHO Mortality Database. Suicide rates were calculated for people aged 10-89 years from 1951-2015 for Italy, 1955-2016 for Austria and 1951-2013 for Switzerland. Trends in suicide rates stratified by gender were analyzed using joinpoint regression models. RESULTS: There was a general pattern of long-term trends that was broadly consistent across all three countries. Suicide rates were stable or decreasing during the 1950s and 1960s, they rose during the 1970s, peaked in the early 1980s and thereafter they declined. There were a few notable exceptions to these general trends. In Italian men, suicide rates increased until 1997, then fell sharply until 2006 and increased again from 2006 to 2015. In women from all three countries, there was an extended period during the 2000s when suicide rates were stable. No trend changes occurred around 1960 or 1990. CONCLUSIONS: The introduction of antidepressants around 1960 and the sharp increase in prescriptions after 1990 with the introduction of the SSRIs did not coincide with trend changes in suicide rates in Italy, Austria or Switzerland.

Swiss GPs' preferences for antidepressant treatment in mild depression: vignette-based quantitative analysis.

BACKGROUND: GPs frequently prescribe antidepressants in mild depression. The aim of this study was to examine, how often Swiss GPs recommend antidepressants in various clinical presentations of mild depression and which factors contribute to antidepressant treatment recommendations. METHODS: We conducted an online survey among Swiss GPs with within-subject effect analysis. Alternating case vignettes described a typical female case of mild depression according to International Classification of Diseases, 10th edition criteria, with and without anxiety symptoms and sleep problems. GPs indicated for each vignette their preferred treatments (several recommendations were possible). Additionally, we assessed GP characteristics, attitudes towards depression treatments, and elements of clinical decision-making. RESULTS: Altogether 178 GPs completed the survey. In the initial description of a case with mild depression, 11% (95%-CI: 7%-17%) of GPs recommended antidepressants. If anxiety symptoms were added to the same case, 29% (23%-36%) recommended antidepressants. If sleep problems were mentioned, 47% (40%-55%) recommended antidepressants, and if both sleep problems and anxiety symptoms were mentioned, 63% (56%-70%) recommended antidepressants. Several factors were independently associated with increased odds of recommending antidepressants, specifically more years of practical experience, an advanced training in psychosomatic and psychosocial medicine, self-dispensation, and a higher perceived effectiveness of antidepressants. By contrast, a higher perceived influence of patient characteristics and the use of clinical practice guidelines were associated with reduced odds of recommending antidepressants. CONCLUSIONS: Consistent with depression practice guidelines, Swiss GPs rarely recommended antidepressants in mild depression if no co-indications (i.e., sleep problems and anxiety symptoms) were depicted. However, presence of sleep problems and anxiety symptoms, many years of practical experience, overestimation of antidepressants' effectiveness, self-dispensation, an advanced training in psychosomatic and psychosocial medicine, and non-use of clinical practice guidelines may independently lead to antidepressant over-prescribing.

'Placement budgets' for supported employment: impact on employment rates in a multicentre randomised controlled trial.

BACKGROUND: The most effective rehabilitation model for job (re-)entry of people with mental illness is supported employment. A barrier to introducing supported employment into standard care is its temporally unlimited provision, which conflicts with health and social legislation in many European countries. AIMS: To test the impact of different 'placement budgets', i.e. a predefined maximum time budget for job seeking until take-up of competitive employment. METHOD: Participants (116) were randomly assigned to 25 h, 40 h or 55 h placement budgets in an intent-to-treat analysis. We applied the individual placement and support model over 24 months, following participants for 36 months. Primary outcome was employment in the labour market for at least 3 months. RESULTS: The proportion of participants obtaining competitive employment was 55.1% in the 25 h group, 37.8% in the 40 h group and 35.8% in the 55 h group. In a Cox regression analysis, time to employment was slightly lower in the 25 h group relative to the 40 h (hazard ratio 1.78, 95% CI 0.88-3.57, P = 0.107) and 55 h groups (hazard ratio 1.74, 95% CI 0.86-3.49, P = 0.122), but this was not statistically significant. The vast majority of all participants who found a job did so within the first 12 months (80.4%). CONCLUSION: A restricted time budget for job finding and placement does not affect the rate of successful employment. In accordance with legislation, a restriction of care provision seems justified and enhances the chances of supported employment being introduced in statutory services.

Comparative efficacy of placebos in short-term antidepressant trials for major depression: a secondary meta-analysis of placebo-controlled trials.

BACKGROUND: The issue of unblinded outcome-assessors and patients has repeatedly been stressed as a flaw in allegedly double-blind antidepressant trials. Unblinding bias can for example result from a drug's marked side effects. If such unblinding bias is present for a given drug, then it might be expected that the placebos of that drug are rated significantly less effective than that of other antidepressants. METHODS: To test this hypothesis, the present exploratory analysis conducted a Bayesian network meta-analysis (NMA) comparing the efficacy of 19 different placebos in placebo-controlled trials provided in the dataset by Cipriani et al. (Lancet 2018; 391: 1357-66). Primary outcome was efficacy (continuous) estimated on the standardized mean difference (SMD) scale and defined as the pre-post change on the Hamilton Depression scale (HAMD-17), on which information was available in N = 258 trials. RESULTS: Comparative placebo ranking suggested mirtazapine-placebo (SMD -2.0 [- 5.0-1.0 95% CrI]) to be the most, and amitriptyline- (SMD 1.2 [- 1.6-3.9 95% CrI]) and trazodone- (SMD 2.1 [- 0.9-5.2 95% CrI]) placebos to be the least effective placebos. Other placebos suggested to be more effective than amitriptyline- and trazodone-placebos (based on 95% CrIs excluding zero) were citalopram, desvenlafaxine, duloxetine, escitalopram, fluoxetine, sertraline, and venlafaxine placebos. These NMA results were corroborated by the observation that the relative efficacy between drug and placebo was considerably larger for amitriptyline and trazodone than for instance mirtazapine, duloxetine, and venlafaxine, supported by a small and insignificant correlation between drug-efficacy and placebo-efficacy (r = - 0.202, p = 0.408). DISCUSSION: The present exploratory NMA indicates that distinguishable side effects of older drugs may unblind outcome-assessors thus resulting in overestimation of the average drug-placebo difference and underrating bias in placebo-arms, particularly for the older antidepressant drugs amitriptyline and trazodone. If confirmed in prospective studies, these findings suggest that efficacy rankings for antidepressants are susceptible to bias and should be considered unreliable or misleading. The analysis is limited by the focus on the single-comparison placebos (76%, i.e., placebos assessed in two-arm trials), since double-comparison placebos (25%, i.e., placebos assessed in three-arm trials) are hard to interpret and therefore not included in the present interpretation. Another limitation is the problem of multiplicity, which was only approximately accounted for in the Bayesian NMA by modelling treatment effects as exchangeable.

Guidelines for the pharmacological acute treatment of major depression: conflicts with current evidence as demonstrated with the German S3-guidelines.

Several international guidelines for the acute treatment of moderate to severe unipolar depression recommend a first-line treatment with antidepressants (AD). This is based on the assumption that AD obviously outperform placebo, at least in the case of severe depression. The efficacy of AD for severe depression can only be definitely clarified with individual patient data, but corresponding studies have only been available recently. In this paper, we point out discrepancies between the content of guidelines and the scientific evidence by taking a closer look at the German S3-guidelines for the treatment of depression. Based on recent studies and a systematic review of studies using individual patient data, it turns out that AD are marginally superior to placebo in both moderate and severe depression. The clinical significance of this small drug-placebo-difference is questionable, even in the most severe forms of depression. In addition, the modest efficacy is likely an overestimation of the true efficacy due to systematic method biases. There is no related discussion in the S3-guidelines, despite substantial empirical evidence confirming these biases. In light of recent data and with their underlying biases, the recommendations in the S3-guidelines are in contradiction with the current evidence. The risk-benefit ratio of AD for severe depression may be similar to the one estimated for mild depression and thus could be unfavorable. Downgrading of the related grade of recommendation would be a logical consequence.

Functional identification of optimized RNAi triggers using a massively parallel sensor assay.

Short hairpin RNAs (shRNAs) provide powerful experimental tools by enabling stable and regulated gene silencing through programming of endogenous microRNA pathways. Since requirements for efficient shRNA biogenesis and target suppression are largely unknown, many predicted shRNAs fail to efficiently suppress their target. To overcome this barrier, we developed a "Sensor assay" that enables the biological identification of effective shRNAs at large scale. By constructing and evaluating 20,000 RNAi reporters covering every possible target site in nine mammalian transcripts, we show that our assay reliably identifies potent shRNAs that are surprisingly rare and predominantly missed by existing algorithms. Our unbiased analyses reveal that potent shRNAs share various predicted and previously unknown features associated with specific microRNA processing steps, and suggest a model for competitive strand selection. Together, our study establishes a powerful tool for large-scale identification of highly potent shRNAs and provides insights into sequence requirements of effective RNAi.

Scientific debate instead of beef; challenging misleading arguments about the efficacy of antidepressants.

In a recent commentary with the polemic title 'Antidepressants; what's the beef?', Goodwin and Nutt argued that the benefit-risk ratio of antidepressants had been questioned inappropriately (Goodwin & Nutt, 2019). Personally I think it is a great achievement that our medical system can offer pharmacological treatments to people who suffer from serious clinical depression, and like Goodwin and Nutt I accept that antidepressants may be useful in some patients (Hengartner & Plöderl, 2018). Nevertheless, and this is where my position deviates from Goodwin and Nutt, I am also concerned about the overestimation of efficacy and the minimisation of harm (Hengartner, 2017). There are many misrepresentations in the commentary by Goodwin and Nutt, all of which systematically inflate the apparent benefits of antidepressants, and in this letter, I will discuss five of them.

Cooperative target mRNA destabilization and translation inhibition by miR-58 microRNA family in C. elegans.

In animals, microRNAs frequently form families with related sequences. The functional relevance of miRNA families and the relative contribution of family members to target repression have remained, however, largely unexplored. Here, we used the Caenorhabditis elegans miR-58 miRNA family, composed primarily of the four highly abundant members miR-58.1, miR-80, miR-81, and miR-82, as a model to investigate the redundancy of miRNA family members and their impact on target expression in an in vivo setting. We found that miR-58 family members repress largely overlapping sets of targets in a predominantly additive fashion. Progressive deletions of miR-58 family members lead to cumulative up-regulation of target protein and RNA levels. Phenotypic defects could only be observed in the family quadruple mutant, which also showed the strongest change in target protein levels. Interestingly, although the seed sequences of miR-80 and miR-58.1 differ in a single nucleotide, predicted canonical miR-80 targets were efficiently up-regulated in the mir-58.1 single mutant, indicating functional redundancy of distinct members of this miRNA family. At the aggregate level, target binding leads mainly to mRNA degradation, although we also observed some degree of translational inhibition, particularly in the single miR-58 family mutants. These results provide a framework for understanding how miRNA family members interact to regulate target mRNAs.

Articulation and testing of a personality-centred model of psychopathology: evidence from a longitudinal community study over 30 years.

Advances in psychopathological research advocate a personality-centred model of common mental disorders (CMD). We tested four hypotheses to test such a model. First, personality relates to critical life events; second, both personality and critical life events relate to CMD; third, interaction effects between personality and critical life events relate to CMD; fourth, neuroticism explains the majority of variance in psychopathology. We analysed data (n = 453) based on seven semi-structured interviews from a longitudinal epidemiologic cohort study over 30 years spanning years 1979 (age 20) to 2008 (age 50). CMD and critical life events were assessed seven times between 1979 and 2008 and personality domains of neuroticism, extraversion and aggressiveness in 1988 and 1993. Aggressiveness and neuroticism related to partnership rupture and job loss. Neuroticism related significantly to major depression, anxiety disorders, substance-use disorders (SUD) and severity of psychopathology. Both partnership rupture and job loss related to major depression and severity of psychopathology, but not to anxiety disorder or SUD. An interaction effect between neuroticism and partnership rupture pointed towards significantly increased SUD prevalence. All associations held when additionally adjusted for childhood adversity and familial socio-economic status. According to a pseudo-R 2, neuroticism explained 51% of total variance in severity of psychopathology over time, while all three personality domains along with both partnership rupture and job loss explained 59% of total variance. In conclusion, personality, especially neuroticism, relates consistently to repeated measures of psychopathology. These associations are independent of and more pervasive than the effects of partnership rupture and job loss. Partnership rupture in interaction with neuroticism may further increase the risk for SUD. We conclude that neuroticism is a fundamental aetiological factor for severe psychopathology, but further testing of this model in other longitudinal studies is required.

Natural Genetic Variation Differentially Affects the Proteome and Transcriptome in Caenorhabditis elegans.

Natural genetic variation is the raw material of evolution and influences disease development and progression. An important question is how this genetic variation translates into variation in protein abundance. To analyze the effects of the genetic background on gene and protein expression in the nematode Caenorhabditis elegans, we quantitatively compared the two genetically highly divergent wild-type strains N2 and CB4856. Gene expression was analyzed by microarray assays, and proteins were quantified using stable isotope labeling by amino acids in cell culture. Among all transcribed genes, we found 1,532 genes to be differentially transcribed between the two wild types. Of the total 3,238 quantified proteins, 129 proteins were significantly differentially expressed between N2 and CB4856. The differentially expressed proteins were enriched for genes that function in insulin-signaling and stress-response pathways, underlining strong divergence of these pathways in nematodes. The protein abundance of the two wild-type strains correlates more strongly than protein abundance versus transcript abundance within each wild type. Our findings indicate that in C. elegans only a fraction of the changes in protein abundance can be explained by the changes in mRNA abundance. These findings corroborate with the observations made across species.

Dimerization of the fungal defense lectin CCL2 is essential for its toxicity against nematodes.

Lectins are used as defense effector proteins against predators, parasites and pathogens by animal, plant and fungal innate defense systems. These proteins bind to specific glycoepitopes on the cell surfaces and thereby interfere with the proper cellular functions of the various antagonists. The exact cellular toxicity mechanism is in many cases unclear. Lectin CCL2 of the mushroom Coprinopsis cinerea was previously shown to be toxic for Caenorhabditis elegans and Drosophila melanogaster. This toxicity is dependent on a single, high-affinity binding site for the trisaccharide GlcNAc(Fucα1,3)ß1,4GlcNAc, which is a hallmark of nematode and insect N-glycan cores. The carbohydrate-binding site is located at an unusual position on the protein surface when compared to other ß-trefoil lectins. Here, we show that CCL2 forms a compact dimer in solution and in crystals. Substitution of two amino acid residues at the dimer interface, R18A and F133A, interfered with dimerization of CCL2 and reduced toxicity but left carbohydrate-binding unaffected. These results, together with the positioning of the two carbohydrate-binding sites on the surface of the protein dimer, suggest that crosslinking of N-glycoproteins on the surface of intestinal cells of invertebrates is a crucial step in the mechanism of CCL2-mediated toxicity. Comparisons of the number and positioning of carbohydrate-binding sites among different dimerizing fungal ß-trefoil lectins revealed a considerable variability in the carbohydrate-binding patterns of these proteins, which are likely to correlate with their respective functions.