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Brain-derived neurotrophic factor variants are associated with childhood-onset mood disorder: confirmation in a Hungarian sample

Brain-derived neurotrophic factor (BDNF) is a nerve growth factor that has been implicated in the neurobiology of depression. Our group has previously reported an association between a BDNF variant and childhood-onset mood disorder (COMD) in an adult sample from Pittsburgh. We hypothesize that variants at the BDNF locus are associated with COMD. Six BDNF polymorphisms were genotyped in 258 trios having juvenile probands with childhood-onset DSM-IV major depressive or dysthymic disorder. BDNF markers included the (GT)n microsatellite, Val66Met and four other single-nucleotide polymorphisms (SNPs) distributed across the BDNF gene. Family-based association and evolutionary haplotype analysis methods were used. Analysis of linkage disequilibrium (LD) revealed substantial LD among all six polymorphisms. Analyses of the Val66Met polymorphism demonstrated significant overtransmission of the val allele (χ2=7.12, d.f.=1, P=0.0076). Consistent with the pattern of LD, all other SNPs showed significant biased transmission. The (GT)n microsatellite alleles also indicated a trend towards biased transmission (170 bp: Z=2.095, P=0.036). Significant haplotypes involved Val66Met and BDNF2 (P=0.0029). In this Hungarian sample, we found all five BDNF SNPs tested and a haplotype containing the BDNF Val66Met Val allele to be associated with COMD. These results provide evidence that BDNF variants affect liability to juvenile-onset mood disorders, supported by data from two independent samples.

Cytokine Genes TNF, IL1A, IL1B, IL6, IL1RN and IL10, and Childhood-Onset Mood Disorders

Background/Aims: Inflammatory cytokines induce a behavioral syndrome, known as sickness behavior, that strongly resembles symptoms typically seen in depression. This resemblance has led to the theory that an imbalance of inflammatory cytokine activity may be a contributing factor in depressive disorders. Support for this is found in multiple lines of evidence, such as the effects of cytokines on the activities of the hypothalamic-pituitary-adrenal axis, serotonin and brain-derived neurotrophic factor, and hippocampal function, all of which are implicated in the etiology of depression. In addition, associations between inflammatory activity and depressive symptomology have been documented in a number of studies, and the depressogenic effects of cytokine therapy are well known. Accordingly, given that depression has a substantial genetic basis, genes involved in the regulation of inflammatory cytokine activity are strong candidates for involvement in genetic susceptibility to depressive disorders. Here, we have tested 6 key genes of this type, TNF, IL1A, IL1B, IL6, IL1RN and IL10, as candidates for involvement in childhood-onset mood disorders. Methods: In this study of 384 families, each ascertained through a child with depression diagnosed before the age of 15 years, 11 polymorphisms of known or likely functional significance (coding and regulatory variants) were analyzed. Results: Testing for biased transmission of alleles from parents to their affected offspring, we found no evidence for an association between childhood-onset mood disorders and any of the polymorphisms, either individually or as haplotypes. Conclusion: The present study does not support the involvement of the TNF, IL1A, IL1B, IL6, IL1RN and IL10 variants as major genetic risk factors contributing to early-onset mood disorders.

Association of the GABRD gene and childhood-onset mood disorders

The chromosome 1p36 region was previously indicated as a locus for susceptibility to recurrent major depressive disorder based on a linkage study in a sample of 497 sib pairs. We investigated the gamma‐aminobutyric acid A (GABAA) δ receptor subunit gene, GABRD, as a susceptibility gene to childhood‐onset mood disorders (COMD) because of substantial evidence implicating GABAergic dysfunction in mood disorders and the position of this gene near the 1p36 linkage region. Using a sample consisting of 645 Hungarian families with a child/adolescent proband diagnosed with a mood disorder with the onset of the first episode before age 15, we found some evidence for the association of two polymorphisms located within the gene, rs2376805 and rs2376803, as well as significant evidence for biased transmission of the haplotypes of these two markers (global χ2 test for haplotypes = 12.746, 3 df, P = 0.0052). Furthermore, significant evidence of association was only observed in male subjects (n = 438) when the results were analyzed by sex (χ2 = 9.000 1 df, P = 0.003 for rs2376805). This was in contrast with the previous linkage findings, as LOD scores exceeding 3 were only in female–female pairs in that study. These findings point to the GABRD gene as a susceptibility gene for COMD; however, this gene may not explain the previous linkage finding.

Association study of CREB1 and childhood-onset mood disorders

Several lines of evidence suggest that the cellular pathways involved in synaptic plasticity contribute to the risk of depression. These findings include the evidence that chronic antidepressant treatment upregulates the cAMP signal transduction cascade resulting in increased expression and function of the cAMP responsive element binding protein (CREB), a transcription factor that increases the expression of key growth factors involved in synaptogenesis and neurogenesis. Recently, linkage to CREB1 was reported for early‐onset depression in families recruited from the Pittsburgh area. This finding was significant only in female sibling pairs from those families. Two specific DNA variants, −656G/A and a C insertion/deletion in intron 8, were identified in CREB1 that co‐segregated with depression in two of the families. We sought to investigate the relationship of CREB1 to childhood‐onset mood disorders (COMD) using a sample of 195 nuclear families (225 affected children) collected in Hungary. We genotyped the two CREB1 DNA variants previously identified as linked to depression as well as three additional polymorphisms spanning the gene. In addition, we genotyped the −656G/A DNA change and the intron 8 polymorphism in a sample of 112 probands with mood disorders collected in the Pittsburgh area and matched controls, and examined the distribution of alleles. The −656A allele was not observed in our samples and there was no evidence for association of the intron 8 polymorphism in either the sample from Pittsburgh (χ2 = 0.061, 1 d.f., P = 0.803) or Hungary (χ2 = 0.040, 1 d.f., P = 0.842). We found no evidence for an association with the other three polymorphisms or with the haplotypes of these markers. Further, we found no sex‐specific relationship. Our results, therefore, do not support the previous evidence for this gene as a major factor contributing to depression.

The Association between Major Depressive Disorder in Childhood and Risk Factors for Cardiovascular Disease in Adolescence

Objective Depression in adults is associated with risk factors for cardiovascular disease (CVD). It is unclear, however, when the association between clinical depression and cardiac risk factors develops or how early in life this association can be detected. Methods In an ongoing study of pediatric depression, we compared CVD risk factors including smoking, obesity, physical activity level, sedentary behavior, and parental history of CVD across three samples of adolescents: probands with established histories of childhood-onset major depressive disorder (n = 210), never-depressed siblings of probands (n = 195), and controls with no history of any major psychiatric disorder (n = 161). Results When assessed during adolescence, 85% of the probands were not in a major depressive episode. Nevertheless, at that assessment, probands had a higher prevalence of regular smoking (odds ratio [OR] = 12.54, 95% confidence interval [CI] = 4.36–36.12) and were less physically active than controls (OR = 0.59, CI = 0.43–0.81) and siblings (OR = 0.70, CI = 0.52–0.94) and had a higher rate of obesity than did controls (OR = 3.67, CI = 1.42–9.52). Parents of probands reported high rates of CVD (significantly higher than did parents of controls), including myocardial infarction and CVD-related hospitalization (ORs = 1.62–4.36, CIs = 1.03–15.40). Differences in CVD risk factors between probands and controls were independent of parental CVD. Conclusions Major depression in childhood is associated with an unfavorable CVD risk profile in adolescence, and risks for pediatric depression and CVD may coincide in families. Effective prevention and treatment of childhood depression may be a means to reduce the incidence of adult CVD.

Stressful life events in a clinical sample of depressed children in Hungary

BACKGROUND There is limited information on the characteristics of stressful life events in depressed pediatric clinical populations and the extent to which sex, age, and their interactions may influence the relations of life events and depression. Using a very large clinical sample of children and adolescents with major depressive disorder (MDD), we therefore examined life events in various ways, as well as their relations to age and sex. METHODS The study included a clinic-based sample of 434 children (ages 7-14) with a DSM-IV diagnosis of MDD and their mothers, and a school-based comparison sample of 724 children and their mothers. Life event information was obtained from the mothers. RESULTS Children with MDD had twice the number of lifetime stressful events than did the comparison group, with very high levels of stressors by the age of 7-9 that stabilized across adolescence. In contrast, the comparison sample experienced a gradual increase in stressful life events as a function of age up to mid-adolescence. Parental health events, death of close relatives, and intrafamilial events were significantly associated with MDD diagnosis. There were significantly stronger associations between parental health- as well as death-event clusters and MDD diagnosis among younger children than adolescents. LIMITATIONS Geographical differences between the clinical and comparison samples, as well as possible parental reporting biases may affect the generalizability of these findings. CONCLUSION The association between some stressful life events and MDD seems to be moderated by age, underscoring the need to examine specific events, as well as clusters of events. Better understanding of such interactions may facilitate early identification of possible risk factors for pediatric MDD.

Association study of the adrenergic receptors and childhood-onset mood disorders in Hungarian families

The adrenergic system has been implicated in the etiology of depression based on a number of lines of evidence, particularly, the mechanism of some classes of antidepressants which increase the synaptic levels of norepinephrine. Further, several genome scans for mood disorders, both unipolar and bipolar, have indicated linkage to the chromosomal regions of 5q23–q33.3, 8p12–p11.2, 4p16, and 10q24–q26, the location of the adrenergic receptors α1B (ADRA1B), β3 (ADRB3), α2C (ADRA2C), α2A (ADRA2A), and β1 (ADRB1). In this manuscript, we report on the relationship of the adrenergic receptors and depression using a family based association approach and 189 families (223 affected children) with childhood‐onset mood disorder (COMD) collected in Hungary. We found no significant evidence for an association with any of the 24 markers, in total, tested across these genes using single marker analysis or haplotypes of markers across these genes. The results in the present sample indicate that these nine genes are unlikely to be major susceptibility genes contributing to COMD.

Mood repair via attention refocusing or recall of positive autobiographical memories by adolescents with pediatric-onset major depression

BACKGROUND Impaired emotion regulation is increasingly recognized as a core feature of depressive disorders. Indeed, currently and previously depressed adults both report greater problems in attenuating sadness (mood repair) in daily life than healthy controls. In contrast, studies of various strategies to attenuate sad affect have mostly found that currently or previously depressed adults and controls were similarly successful at mood repair in the laboratory. But few studies have examined mood repair among depression-prone youths or the effects of trait characteristics on mood repair outcomes in the laboratory. METHODS Adolescents, whose first episode of major depressive disorder (MDD) had onset at age 9, on average (probands), and were either in remission or depressed, and control peers, watched a sad film clip. Then, they were instructed to engage in refocusing attention (distraction) or recalling happy memories. Using affect ratings provided by the youths, we tested two developmentally informed hypotheses about whether the subject groups would be similarly able to attenuate sadness via the two mood repair strategies. We also explored if self-reported habitual (trait) mood repair influenced laboratory performance. RESULTS Contrary to expectations, attention refocusing and recall of happy memories led to comparable mood benefits across subjects. Control adolescents reported significantly greater reductions in sadness than did depressed (Cohens d = .48) or remitted (Cohens d = .32) probands, regardless of mood repair strategy, while currently depressed probands remained the saddest after mood repair. Habitual mood repair styles moderated the effects of instructed (state) mood repair in the laboratory. CONCLUSIONS Whether depressed or in remission, adolescents with MDD histories are not as efficient at mood repair in the laboratory as controls. But proband-control group differences in mood repair outcomes were modest in scope, suggesting that the abilities that subserve affect regulation have been preserved in probands to some degree. Further information about the nature of mood repair problems among youths with depression histories would help to better understand the clinical course of MDD and to design personalized interventions for depression.

Tagging SNP Association Study of the IL-1β Gene (IL1B) and Childhood-Onset Mood Disorders

Given substantial evidence for IL‐1β 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.

Mutation screen and association analysis of the glucocorticoid receptor gene (NR3C1) in childhood‐onset mood disorders (COMD)

Depressive disorders are highly heterogeneous psychiatric disorders involving deficits to cognitive, psychomotor, and emotional processing. Considerable evidence links disruption to the hypothalamic–pituitary–adrenal (HPA) axis to the etiology of depression, with specific deficits reported in glucocorticoid receptor (GR)‐mediated negative feedback. Given the role of GR‐mediated negative feedback in mediating response to stress, and the clear link between stress and depression, it is plausible that polymorphisms in the GR gene (NR3C1) act to increase susceptibility. Maternal behavior in rats epigenetically alters a NGF1‐A transcription factor binding‐site in the promoter region of the GR gene, providing a mechanism by which environmental cues can regulate GR expression and thus response to stress. The analogous region of the human GR gene (NR3C1) has not been studied, but it is possible that polymorphisms in this region may alter the binding of transcription factors known to regulate GR expression. In this study, we have performed bioinformatic analyses on the promoter region of NR3C1 to identify conserved promoter sequences and predicted transcription factor binding sites. These regions were screened with denaturing high‐performance liquid chromatography (DHPLC) and direct re‐sequencing, and several novel polymorphic variants were identified. We genotyped nine polymorphisms across NR3C1 in a large sample of Hungarian nuclear families ascertained through affected probands with a diagnosis of childhood‐onset mood disorders (COMD). Single‐marker analysis provided little evidence for an association of this gene with COMD, but multi‐marker analysis across a region of high linkage disequilibrium revealed modest evidence for the biased transmission of several haplotypes.