Association of the neurotrophic tyrosine kinase receptor 3 (NTRK3) gene and childhood-onset mood disorders

Genome-wide association study in a rat model of temperament identifies multiple loci for exploratory locomotion and anxiety-like traits

Common genetic factors likely contribute to multiple psychiatric diseases including mood and substance use disorders. Certain stable, heritable traits reflecting temperament, termed externalizing or internalizing, play a large role in modulating vulnerability to these disorders. To model these heritable tendencies, we selectively bred rats for high and low exploration in a novel environment [bred High Responders (bHR) vs. Low Responders (bLR)]. To identify genes underlying the response to selection, we phenotyped and genotyped 538 rats from an F₂ cross between bHR and bLR. Several behavioral traits show high heritability, including the selection trait: exploratory locomotion (EL) in a novel environment. There were significant phenotypic and genetic correlations between tests that capture facets of EL and anxiety. There were also correlations with Pavlovian conditioned approach (PavCA) behavior despite the lower heritability of that trait. Ten significant and conditionally independent loci for six behavioral traits were identified. Five of the six traits reflect different facets of EL that were captured by three behavioral tests. Distance traveled measures from the open field and the elevated plus maze map onto different loci, thus may represent different aspects of novelty-induced locomotor activity. The sixth behavioral trait, number of fecal boli, is the only anxiety-related trait mapping to a significant locus on chromosome 18 within which the Pik3c3 gene is located. There were no significant loci for PavCA. We identified a missense variant in the Plekhf1 gene on the chromosome 1:95 Mb QTL and Fancf and Gas2 as potential candidate genes that may drive the chromosome 1:107 Mb QTL for EL traits. The identification of a locomotor activity-related QTL on chromosome 7 encompassing the Pkhd1l1 and Trhr genes is consistent with our previous finding of these genes being differentially expressed in the hippocampus of bHR vs. bLR rats. The strong heritability coupled with identification of several loci associated with exploratory locomotion and emotionality provide compelling support for this selectively bred rat model in discovering relatively large effect causal variants tied to elements of internalizing and externalizing behaviors inherent to psychiatric and substance use disorders.

Immunoglobulin-Like Receptors and Their Impact on Wiring of Brain Synapses

Synapse formation is mediated by a surprisingly large number and wide variety of genes encoding many different protein classes. One of the families increasingly implicated in synapse wiring is the immunoglobulin superfamily (IgSF). IgSF molecules are by definition any protein containing at least one Ig-like domain, making this family one of the most common protein classes encoded by the genome. Here, we review the emerging roles for IgSF molecules in synapse formation specifically in the vertebrate brain, focusing on examples from three classes of IgSF members: ( a) cell adhesion molecules, ( b) signaling molecules, and ( c) immune molecules expressed in the brain. The critical roles for IgSF members in regulating synapse formation may explain their extensive involvement in neuropsychiatric and neurodevelopmental disorders. Solving the IgSF code for synapse formation may reveal multiple new targets for rescuing IgSF-mediated deficits in synapse formation and, eventually, new treatments for psychiatric disorders caused by altered IgSF-induced synapse wiring.

Targeted exome sequencing for the identification of a protective variant against Internet gaming disorder at rs2229910 of neurotrophic tyrosine kinase receptor, type 3 (NTRK3): A pilot study

Background and aims Internet gaming disorder (IGD) has gained recognition as a potential new diagnosis in the fifth revision of the Diagnostic and Statistical Manual of Mental Disorders, but genetic evidence supporting this disorder remains scarce. Methods In this study, targeted exome sequencing was conducted in 30 IGD patients and 30 control subjects with a focus on genes linked to various neurotransmitters associated with substance and non-substance addictions, depression, and attention deficit hyperactivity disorder. Results rs2229910 of neurotrophic tyrosine kinase receptor, type 3 (NTRK3) was the only single nucleotide polymorphism (SNP) that exhibited a significantly different minor allele frequency in IGD subjects compared to controls (p = .01932), suggesting that this SNP has a protective effect against IGD (odds ratio = 0.1541). The presence of this potentially protective allele was also associated with less time spent on Internet gaming and lower scores on the Young's Internet Addiction Test and Korean Internet Addiction Proneness Scale for Adults. Conclusions The results of this first targeted exome sequencing study of IGD subjects indicate that rs2229910 of NTRK3 is a genetic variant that is significantly related to IGD. These findings may have significant implications for future research investigating the genetics of IGD and other behavioral addictions.

Neurotrophin Signaling and Stem Cells-Implications for Neurodegenerative Diseases and Stem Cell Therapy

Neurotrophins (NTs) are members of a neuronal growth factor protein family whose action is mediated by the tropomyosin receptor kinase (TRK) receptor family receptors and the p75 NT receptor (p75NTR), a member of the tumor necrosis factor (TNF) receptor family. Although NTs were first discovered in neurons, recent studies have suggested that NTs and their receptors are expressed in various types of stem cells mediating pivotal signaling events in stem cell biology. The concept of stem cell therapy has already attracted much attention as a potential strategy for the treatment of neurodegenerative diseases (NDs). Strikingly, NTs, proNTs, and their receptors are gaining interest as key regulators of stem cells differentiation, survival, self-renewal, plasticity, and migration. In this review, we elaborate the recent progress in understanding of NTs and their action on various stem cells. First, we provide current knowledge of NTs, proNTs, and their receptor isoforms and signaling pathways. Subsequently, we describe recent advances in the understanding of NT activities in various stem cells and their role in NDs, particularly Alzheimer's disease (AD) and Parkinson's disease (PD). Finally, we compile the implications of NTs and stem cells from a clinical perspective and discuss the challenges with regard to transplantation therapy for treatment of AD and PD.

The Interplay of Genetics, Behavior, and Pain with Depressive Symptoms in the Elderly

PURPOSE OF STUDY

About 25% of older adults suffer from depressive symptoms. Commonly studied candidate genes associated with depression include those that influence serotonin (SLC6A4), dopamine (COMT), or neuroplasticity (BDNF, NTRK3). However, the majority of candidate gene studies do not consider the interplay of genetics, demographic, clinical, and behavioral factors and how they jointly contribute to depressive symptoms among older adults. The purpose of this study was to gain a more comprehensive understanding of depressive symptoms among older adults.

DESIGN AND METHODS

In this descriptive study, demographic, behavioral, and clinical characteristics (age, gender, comorbidities, volunteering, physical activity, pain, and fear of falling) were obtained via interview of 114 residents in a continuing care retirement community. Peripheral whole blood was collected for DNA extraction. We examined common single nucleotide polymorphisms (SNPs) in the aforementioned genes using path analyses.

RESULTS

SNPs in the NTRK3 gene, pain, physical activity, and fear of falling were directly associated with depressive symptoms in older adults. Those who had polymorphisms in the NTRK3 gene, pain, fear of falling, and were less physically active were more likely to exhibit depressive symptoms. None of the SNPs in SLC6A4, COMT, or BDNF genes were significantly associated with depressive symptoms.

IMPLICATIONS

Our use of a path analysis to examine a biopsychosocial model of depressive symptoms provided the opportunity to describe a comprehensive clinical picture of older adults at risk for depressive symptoms. Thus, interventions could be implemented to identify older adults at risk for depressive symptoms.

The Involvement of Genes in Adolescent Depression: A Systematic Review

Numerous studies have reported on the roles of genetic factors in the development of depression in adolescents and young adults. However, there are few systematic reviews that update our understanding of adolescent depression with the biological findings identifying the roles of gene expression and/or polymorphism(s). This review systematically summarized the findings that clearly identified the contribution of a gene to the risk of depression in adolescents between the ages of 10 and 19 years old and young adults between the ages of 20 and 25 years old. Data were obtained through searching PubMed, Embase, and Web of Science. A total of 47 studies on early adolescence and three studies on young adults were included in the current review. Most articles studied genes in the serotonergic system (n = 26), dopaminergic system (n = 3), and the Brain-derived neurotropic factor (BDNF) gene (n = 12). 92.3% of studies (24/26) identified positive associations of 5-HTTLPR polymorphism with depressive illness or depressive symptoms. 83.3% of studies (10/12) found positive association between BDNF Val66Met genotype and adolescent depressive symptoms. More studies should be conducted on the 18 genes reported in a few studies to clarify their roles in the risk for adolescent depression.

Multivariate genetic determinants of EEG oscillations in schizophrenia and psychotic bipolar disorder from the BSNIP study

Schizophrenia (SZ) and psychotic bipolar disorder (PBP) are disabling psychiatric illnesses with complex and unclear etiologies. Electroencephalogram (EEG) oscillatory abnormalities in SZ and PBP probands are heritable and expressed in their relatives, but the neurobiology and genetic factors mediating these abnormalities in the psychosis dimension of either disorder are less explored. We examined the polygenic architecture of eyes-open resting state EEG frequency activity (intrinsic frequency) from 64 channels in 105 SZ, 145 PBP probands and 56 healthy controls (HCs) from the multisite BSNIP (Bipolar-Schizophrenia Network on Intermediate Phenotypes) study. One million single-nucleotide polymorphisms (SNPs) were derived from DNA. We assessed eight data-driven EEG frequency activity derived from group-independent component analysis (ICA) in conjunction with a reduced subset of 10,422 SNPs through novel multivariate association using parallel ICA (para-ICA). Genes contributing to the association were examined collectively using pathway analysis tools. Para-ICA extracted five frequency and nine SNP components, of which theta and delta activities were significantly correlated with two different gene components, comprising genes participating extensively in brain development, neurogenesis and synaptogenesis. Delta and theta abnormality was present in both SZ and PBP, while theta differed between the two disorders. Theta abnormalities were also mediated by gene clusters involved in glutamic acid pathways, cadherin and synaptic contact-based cell adhesion processes. Our data suggest plausible multifactorial genetic networks, including novel and several previously identified (DISC1) candidate risk genes, mediating low frequency delta and theta abnormalities in psychoses. The gene clusters were enriched for biological properties affecting neural circuitry and involved in brain function and/or development.

Transcriptional evidence for the role of chronic venlafaxine treatment in neurotrophic signaling and neuroplasticity including also Glutamatergic [corrected] - and insulin-mediated neuronal processes

OBJECTIVES

Venlafaxine (VLX), a serotonine-noradrenaline reuptake inhibitor, is one of the most commonly used antidepressant drugs in clinical practice for the treatment of major depressive disorder (MDD). Despite being more potent than its predecessors, similarly to them, the therapeutical effect of VLX is visible only 3-4 weeks after the beginning of treatment. Furthermore, recent papers show that antidepressants, including also VLX, enhance the motor recovery after stroke even in non depressed persons. In the present, transcriptomic-based study we looked for changes in gene expressions after a long-term VLX administration.

METHODS

Osmotic minipumps were implanted subcutaneously into Dark Agouti rats providing a continuous (40 mg/kg/day) VLX delivery for three weeks. Frontal regions of the cerebral cortex were isolated and analyzed using Illumina bead arrays to detect genes showing significant chances in expression. Gene set enrichment analysis was performed to identify specific regulatory networks significantly affected by long term VLX treatment.

RESULTS

Chronic VLX administration may have an effect on neurotransmitter release via the regulation of genes involved in vesicular exocytosis and receptor endocytosis (such as Kif proteins, Myo5a, Sv2b, Syn2 or Synj2). Simultaneously, VLX activated the expression of genes involved in neurotrophic signaling (Ntrk2, Ntrk3), glutamatergic transmission (Gria3, Grin2b and Grin2a), neuroplasticity (Camk2g/b, Cd47), synaptogenesis (Epha5a, Gad2) and cognitive processes (Clstn2). Interestingly, VLX increased the expression of genes involved in mitochondrial antioxidant activity (Bcl2 and Prdx1). Additionally, VLX administration also modulated genes related to insulin signaling pathway (Negr1, Ppp3r1, Slc2a4 and Enpp1), a mechanism that has recently been linked to neuroprotection, learning and memory.

CONCLUSIONS

Our results strongly suggest that chronic VLX treatment improves functional reorganization and brain plasticity by influencing gene expression in regulatory networks of motor cortical areas. These results are consonant with the synaptic (network) hypothesis of depression and antidepressant-induced motor recovery after stroke.

Genetics of serum BDNF: meta-analysis of the Val66Met and genome-wide association study

OBJECTIVES

Lower levels of serum brain derived neurotrophic factor (BDNF) is one of the best known biomarkers of depression. To identify genetic variants associated with serum BDNF, we tested the Val66Met (rs6265) functional variant and conducted a genome-wide association scan (GWAS).

METHODS

In a community-based sample (N = 2054; aged 19-101, M = 51, SD = 15) from Sardinia, Italy, we measured serum BDNF concentration and conducted a GWAS.

RESULTS

We estimated the heritability of serum BDNF to be 0.48 from sib-pairs. There was no association between serum BDNF and Val66Met in the SardiNIA sample and in a meta-analysis of published studies (k = 13 studies, total n = 4727, P = 0.92). Although no genome-wide significant associations were identified, some evidence of association was found in the BDNF gene (rs11030102, P = 0.001) and at two loci (rs7170215, P = 4.8 × 10⁻⁵ and rs11073742 P = 1.2 × 10⁻⁵) near and within NTRK3 gene, a neurotrophic tyrosine kinase receptor.

CONCLUSIONS

Our study and meta-analysis of the literature indicate that the BDNF Val66Met variant is not associated with serum BDNF, but other variants in the BDNF and NTRK3 genes might regulate the level of serum BDNF.

Central amygdala nucleus (Ce) gene expression linked to increased trait-like Ce metabolism and anxious temperament in young primates

Children with anxious temperament (AT) are particularly sensitive to new social experiences and have increased risk for developing anxiety and depression. The young rhesus monkey is optimal for studying the origin of human AT because it shares with humans the genetic, neural, and phenotypic underpinnings of complex social and emotional functioning. In vivo imaging in young monkeys demonstrated that central nucleus of the amygdala (Ce) metabolism is relatively stable across development and predicts AT. Transcriptome-wide gene expression, which reflects combined genetic and environmental influences, was assessed within the Ce. Results support a maladaptive neurodevelopmental hypothesis linking decreased amygdala neuroplasticity to early-life dispositional anxiety. For example, high AT individuals had decreased mRNA expression of neurotrophic tyrosine kinase, receptor, type 3 (NTRK3). Moreover, variation in Ce NTRK3 expression was inversely correlated with Ce metabolism and other AT-substrates. These data suggest that altered amygdala neuroplasticity may play a role the early dispositional risk to develop anxiety and depression.

Association study of early-immediate genes in childhood-onset mood disorders and suicide attempt

Childhood-onset mood disorders (COMD) are serious affective disorders with deleterious developmental sequelae including interpersonal dysfunction, psychotic symptoms and suicidal behavior. The current study examines 10 markers from two early-immediate genes for association with COMD and suicide attempt (SA) - HOMER1 and human neuronal pentraxin II (NPTX2). We examined individuals diagnosed with COMD versus matched controls, as well as individuals with COMD and a history of at least one lifetime SA versus COMD participants with no history of SA. No significant genotypic association was noted between any of the single nucleotide polymorphisms (SNPs) and COMD. Our sample yielded a nominally significant allelic association between the HOMER1 rs7713917 SNP and COMD. We report significant genotype associations between HOMER1 rs2290639 and SA , and between NPTX2 markers rs705315 and rs1681248 and SA, findings that remained statistically significant after multiple test correction. A three-way interaction was observed among HOMER1 rs4704560, rs2290639 and NPTX2 rs705318. The associations we describe for HOMER1 and NPTX2 with SA should be considered preliminary until replicated.

Intron 12 in NTRK3 is associated with bipolar disorder

Based on the important role of neurotrophic factors in brain development and plasticity and reports of association between schizophrenia and the gene neurotrophic tyrosine kinase receptor 3 (NTRK3), we investigated associations of bipolar disorder with polymorphisms in NTRK3. Recently, our group reported evidence for a possible association of NTRK3 polymorphisms with hippocampal function and schizophrenia. In the present study, we used a homogenous Norwegian case-control sample (the TOP study) consisting of 194 patients diagnosed with bipolar disorder and 336 healthy controls genotyped on the Affymetrix Genome-wide Human SNP Array 6.0. In total 149 markers were investigated for SNP-disease association. Polymorphisms in over 20 markers were nominally associated with bipolar disorder, covering intron 5 to intron 12. Interestingly, our markers appeared to be located close or within the linkage regions reported in schizophrenia, early-onset major depressive disorder and eating disorder, supporting the hypothesis that some genes influence risk beyond traditional diagnostic boundaries.

Prevalence and correlates of eating disorders in 875 patients with bipolar disorder

OBJECTIVE

Relatively little is known about the co-occurrence of bipolar and eating disorders. We therefore assessed the prevalence and clinical correlates of eating disorders in 875 patients with bipolar disorder.

METHOD

875 outpatients with DSM-IV bipolar I or II disorder were evaluated with structured diagnostic interviews and clinician- and self-administered questionnaires to determine bipolar and eating disorder diagnoses, other comorbid Axis I disorder diagnoses, and demographic and historical illness characteristics.

RESULTS

125 (14.3%) patients met DSM-IV criteria for at least one comorbid lifetime Axis I eating disorder, with binge eating disorder (N=77) being more common than bulimia nervosa (n=42) and anorexia nervosa (N=27). There were no significant eating disorder comorbidity differences between bipolar I and bipolar II patients. Presence of a lifetime comorbid eating disorder was associated with female gender, younger age, earlier age of onset of mood symptoms and of bipolar disorder, presentation in a mixed episode, greater number of prior mood episodes, history of rapid cycling and suicide attempts, greater mean BMI, obesity and severe obesity, and family history of depression, bipolar disorder, alcoholism, and drug abuse. When the three eating disorder groups were compared, lifetime anorexia nervosa was associated with normal weight and a lifetime anxiety disorder, lifetime bulimia nervosa was associated with overweight, and lifetime binge eating disorder was associated with obesity and severe obesity.

CONCLUSIONS

Patients with bipolar disorder, especially women, not infrequently have comorbid eating disorders, and this comorbidity is associated with an earlier age of onset and more severe course of bipolar illness.

Postsynaptic TrkC and presynaptic PTPσ function as a bidirectional excitatory synaptic organizing complex

Neurotrophin receptor tyrosine kinases (Trks) have well-defined trophic roles in nervous system development through kinase activation by neurotrophins. Yet Trks have typical cell-adhesion domains and express noncatalytic isoforms, suggesting additional functions. Here we discovered noncatalytic TrkC in an unbiased hippocampal neuron-fibroblast coculture screen for proteins that trigger differentiation of neurotransmitter release sites in axons. All TrkC isoforms, but not TrkA or TrkB, function directly in excitatory glutamatergic synaptic adhesion by neurotrophin-independent high-affinity trans binding to axonal protein tyrosine phosphatase receptor PTPσ. PTPσ triggers and TrkC mediates clustering of postsynaptic molecules in dendrites, indicating bidirectional synaptic organizing functions. Effects of a TrkC-neutralizing antibody that blocks TrkC-PTPσ interaction and TrkC knockdown in culture and in vivo reveal essential roles of TrkC-PTPσ in glutamatergic synapse formation. Thus, postsynaptic TrkC trans interaction with presynaptic PTPσ generates bidirectional adhesion and recruitment essential for excitatory synapse development and positions these signaling molecules at the center of synaptic pathways.

Lack of association between MAGEL2 and schizophrenia and mood disorders in the Japanese population

Several investigations have reported that abnormalities in circadian rhythms might be related with the pathophysiology of psychiatric disorders, since many psychiatric patients have insomnia and sleep-awake disturbance. A recent animal study reported that Magel2, which encodes a member of the MAGE/necdin family of proteins, might be associated in the pathophysiology of psychiatric disorders. Magel2 gene knockout mice showed altered concentrations of both dopamine and serotonin in several parts of the brain compared with controls. In addition, the authors of that study detected a bilateral reduction in cortical volume in distinct regions of the Magel2 gene knockout mice brain, including focused regions in the parieto-temporal lobe of the cerebral cortex, the amygdala, the hippocampus, and the nucleus accumbens. These mice were also found to have hypoactivity and abnormalities in circadian rhythms. From this evidence, we considered Magel2 gene (MAGEL2) to be a good candidate gene for the pathophysiology of schizophrenia and mood disorder, and we conducted a case-control study among Japanese (731 schizophrenia patients, 465 MDD patients, 156 BP patients and 758 controls) using three tagging SNPs in MAGEL2 (rs850815, rs8920 and rs4480754), selected using the HapMap database. We did not find any association between MAGEL2 and schizophrenia, BP or MDD in allele/genotype-wise analysis or haplotype-wise analysis. Our results suggest that MAGEL2 may not play a role in the pathophysiology of schizophrenia and mood disorders in the Japanese population. A replication study using larger samples may be required for conclusive results, since our sample size was small and our study analyzed only three SNPs in MAGEL2.

Differential gene expression in a rat model of depression based on persistent differences in exploratory activity

Affective disorders are often accompanied by changes in motivation and anxiety. We investigated the genome-wide gene expression patterns in an animal model of depression that separates Wistar rats belonging into clusters of persistently high anxiety/low motivation to explore and low anxiety/high motivation to explore (low explorers and high explorers, LE and HE, respectively), in three brain regions previously implicated in mood disorders (raphe, hippocampus and the frontal cortex). Several serotonin-, GABA-, and glutamatergic genes were differentially expressed in LE- and HE-rats. The analysis of Gene Ontology biological process terms associated with the differentially regulated genes identified a significant overrepresentation of genes involved in the neuron development, morphogenesis, and differentiation; the most enriched pathways from the Kyoto Encyclopedia of Genes and Genomes were the Wnt signalling, MAPK signalling, long-term potentiation, and long-term depression pathways. These findings corroborate some expression data from other models of depression, and suggest additional targets.

Susceptibility to stress in transgenic mice overexpressing TrkC, a model of panic disorder

Stressful life events increase the susceptibility for subsequent onset of psychiatric disorders in humans. Previous research has implicated neurotrophins in the onset of some stress-related diseases, such as major depression disorder, post-traumatic stress disorder or panic disorder. We have tested the hypothesis that the neurotrophin-3 (NT-3)/TrkC system is a genetic interface mediating the deleterious effects of stress on the initiation of panic disorder and other pathologies. To this aim, we have analyzed the functionality of HPA axis and the behavioral consequences of different types of stressful conditions in a mouse model of panic disorder, which overexpresses TrkC, the high affinity-receptor for NT-3 (TgNTRK3). Our results reveal that TgNTRK3 mice exhibit an altered circadian corticosterone rhythm that is reversed by clonidine treatment, but normal expression of genes involved in the control of the hypothalamus-pituitary-adrenal (HPA) axis (CRH, GR) and normal corticosterone response to acute and chronic stressors. In contrast, they exhibit an altered pattern of activation of stress-related brain areas and showed enhanced anxiety-related behavior and more passive strategies than wild types under some chronic stress conditions. We conclude that TgNTRK3 mice present differences in their response to stress characterized by subtle changes in the HPA axis, marked changes in acute stress-induced brain activation and altered coping strategies, suggesting a key role of TrkC receptor in the stress neural circuitry and in the behavioral consequences of chronic stress.

Genome scan in sibling pairs with juvenile-onset mood disorders: Evidence for linkage to 13q and Xq

Mood disorders (bipolar and depressive disorders) in children and adolescents are associated with significant morbidity and mortality. Twin and family studies, for the most part, indicate higher familiality and heritability for mood disorders that onset in childhood/adolescence than those that onset in adulthood. To identify the genetic contribution to mood disorders that onset in childhood/adolescence, we performed a genome scan on 146 nuclear families from Hungary containing an affected proband and affected siblings. In total, the pedigrees contained 303 affected children: 146 probands, 137 siblings with a first episode of mood disorder before 14.9 years of age, and 20 siblings with onset of their first episode after 14.9 years of age but before the age of 18. The results of the genome scan using 405 microsatellite markers did not provide evidence for linkage at the recommended genome wide significance level for any novel loci. However, markers on two chromosomes, 13q and Xq, provided evidence for linkage in regions previously identified as linked to bipolar disorder in multiple studies. For the marker on chromosome 13q the peak non-parametric multipoint LOD score was at the marker D13S779 (LOD = 1.5, P = 0.004). On chromosome Xq, evidence for linkage was observed across a large region spanning two regions previously linked to bipolar disorder; Xq24 to Xq28, with a peak at marker TTTA062 (LOD 2.10, P = 0.0009) in Xq28. Results for these regions exceed the recommended P-value for a replication study of P < 0.01 and thus provide evidence for these two loci as contributing to mood disorders with juvenile onset.

Tagging SNP association study of the IL-1beta gene (IL1B) and childhood-onset mood disorders

Given substantial evidence for IL-1beta involvement in the etiology of depression, the IL1B gene is a strong candidate for involvement in susceptibility to depressive disorders. However, association studies investigating this, to date, have been limited to just two polymorphisms (rs1143627[-31T/C] and rs16944[-511C/T]) that constitute only a fraction of the genetic variation that is actually present across this gene in the population. Here, in a family-based association study of childhood-onset mood disorders (COMD), characterized by onset of depression before the age of 15, we have used a gene-wide approach, employing a panel of five tagging SNPs spanning the entire gene. Based on TDT analyses of both individual alleles and haplotypes, in a study sample of 646 families (with 782 affected children), none of the SNPs, including those implicated in transcriptional regulation of the gene, showed evidence for association with COMD. This is the largest and most comprehensive study of IL1B in relation to mood disorders that has been carried out, to date. The results do not support the involvement of IL1B as a major factor in genetic risk for early-onset mood disorders.