Growing old but not growing apart: twin similarity in the latter half of the lifespan

While a substantial amount of behavioral genetic research has helped to characterize developmental trends in twin similarity in early life, relatively little is known about changes in twin similarity with age in adulthood. We investigated age moderation of twin similarity for a composite measure of cognitive ability, depression symptomatology and hand grip strength in a cross-sectional sample of 2,332 like-sex pairs of Danish twins age 46-96 years. All three outcomes were strongly correlated with age, indicating that the three phenotypes analyzed are not developmentally static. Nonetheless, in moderated regression analysis we found no evidence of declining twin similarity for any of the three outcomes in either zygosity group. Moreover, biometric analysis of the twin data revealed minimal differences in heritability estimates across the age range sampled. While small sample size limits our ability to draw firm conclusions at very advanced ages, these findings call into question the hypothesis that the cumulative impact of life experiences diminishes twin similarity at least through age 80. We hypothesize that twins are able to maintain similarity over extended periods of time because in part they are able to construct similar environments that reinforce that similarity.

Genetic risk factors for depression in Alzheimer`s disease patients

OBJECTIVE

Alzheimer's Disease (AD) is often associated with depressive symptoms developing at any time before and after AD onset. The aetiology of depression in AD has not sufficiently been characterized, but biological aspects due to neurodegeneration and/ or genetic risk factors may play a plausible role and may distinguish it from common depressive disorders.

METHOD

To investigate the possible relationship between genetic risk factors and depression in AD, we assessed genetic polymorphisms reported to be associated with depression (MAOA VNTR, ACE 288bp Insertion/ Deletion, 5HTTLPR, COMT Val158Met, BDNF Val66Met, TPH1 A218C, HTR2A T102C, P2RX7 Q460R, FKBP5 rs1360780 and CRHR1 rs242941) in a cross-sectional study on 246 AD patients with or without clinically significant major depressive disorder (MDD) according to DSM-IV.

RESULTS

Significant associations between AD and MDD have been found for three polymorphisms mainly in females (TPH1 A218C, MAOA VNTR and BDNF Val66Met) and one polymorphism in the total population only (FKBP5 rs1360780). There was an increased risk of having MDD in homozygous female carriers of the TPH1 A-allele (odds ratio: 4.35) and homozygous carriers of the MAOA VNTR low activity allele 3R (odds ratio: 3.37).

CONCLUSION

We detected allelic or genotypic associations of MAOA, TPH1, FKBP5 and BDNF in clinically significant MDD in AD. Odds-ratios were generally higher in female AD-patients, which might be due to the composition of the study population. Further studies on the neurotransmitter systems affected by the genetic polymorphisms found to be associated with MDD in AD may help to elucidate the underlying pathomechanisms of MDD.

Behavioral abnormalities observed in Zfhx2-deficient mice

Zfhx2 (also known as zfh-5) encodes a transcription factor containing three homeobox domains and 18 Zn-finger motifs. We have reported that Zfhx2 mRNA is expressed mainly in differentiating neurons in the mouse brain and its expression level is negatively regulated by the antisense transcripts of Zfhx2. Although the expression profile of Zfhx2 suggests that ZFHX2 might have a role in a particular step of neuronal differentiation, the specific function of the gene has not been determined. We generated a Zfhx2-deficient mouse line and performed a comprehensive battery of behavioral tests to elucidate the function of ZFHX2. Homozygous Zfhx2-deficient mice showed several behavioral abnormalities, namely, hyperactivity, enhanced depression-like behaviors, and an aberrantly altered anxiety-like phenotype. These behavioral phenotypes suggest that ZFHX2 might play roles in controlling emotional aspects through the function of monoaminergic neurons where ZFHX2 is expressed. Moreover, considering their phenotypes, the Zfhx2-deficient mice may provide a novel model of human psychiatric disorders.

Individual differences in amygdala-medial prefrontal anatomy link negative affect, impaired social functioning, and polygenic depression risk

Individual differences in affective and social processes may arise from variability in amygdala-medial prefrontal (mPFC) circuitry and related genetic heterogeneity. To explore this possibility in humans, we examined the structural correlates of trait negative affect in a sample of 1050 healthy young adults with no history of psychiatric illness. Analyses revealed that heightened negative affect was associated with increased amygdala volume and reduced thickness in a left mPFC region encompassing the subgenual and rostral anterior cingulate cortex. The most extreme individuals displayed an inverse correlation between amygdala volume and mPFC thickness, suggesting that imbalance between these structures is linked to negative affect in the general population. Subgroups of participants were further evaluated on social (n = 206) and emotional (n = 533) functions. Individuals with decreased mPFC thickness exhibited the poorest social cognition and were least able to correctly identify facial emotion. Given prior links between disrupted amygdala-mPFC circuitry and the presence of major depressive disorder (MDD), we explored whether the individual differences in anatomy observed here in healthy young adults were associated with polygenic risk for MDD (n = 438) using risk scores derived from a large genome-wide association analysis (n = 18,759). Analyses revealed associations between increasing polygenic burden for MDD and reduced cortical thickness in the left mPFC. These collective findings suggest that, within the healthy population, there is significant variability in amygdala-mPFC circuitry that is associated with poor functioning across affective and social domains. Individual differences in this circuitry may arise, in part, from common genetic variability that contributes to risk for MDD.

Beyond structural equation modeling: model properties and effect size from a Bayesian viewpoint. An example of complex phenotype-genotype associations in depression

Despite the rapid evolution of measurement technologies in biomedicine and genetics, most of the recent studies aiming to explore the genetic background of multifactorial diseases were only moderately successful. One of the causes of this phenomenon is that the bottleneck of genetic research is no longer the measurement process related to various laboratory technologies, but rather the analysis and interpretation of results. The commonly applied univariate methods are inadequate for exploring complex dependency patterns of multifactorial diseases which includes nearly all common diseases, such as depression, hypertension, and asthma. A comprehensive investigation requires multivariate modeling methods that enable the analysis of interactions between factors, and allow a more detailed interpretation of studies measuring complex phenotype descriptors. In this paper we discuss various aspects of multivariate modeling through a case study analyzing the effect of the single nucleotide polymorphism rs6295 in the HTR1A gene on depression and impulsivity. We overview basic concepts related to multivariate modeling and compare the properties of two investigated modeling techniques: Structural Equation Modeling and Bayesian network based learning algorithms. The resulting models demonstrate the advantages of the Bayesian approach in terms of model properties and effect size as it allows coherent handling of the weakly significant effect of rs6295. Results also confirm the mediating role of impulsivity between the SNP rs6295 of HTR1A and depression.

Association between the COMT gene and rumination in a Hungarian sample

INTRODUCTION

Rumination is a multidimensional trait which is a proven risk factor in the vulnerability to depression. The aim to identify the main risk genes for depression in addition to the gene-environment interactions pointed to the importance of intermediate phenotypes, like rumination, to improve our understanding of the biological mechanisms of depression. Catechol-O-Methyltransferase (COMT) gene is extensively investigated in depression with contradictory results but its association with rumination, as an intermediate phenotype in depression, has not been investigated yet.

METHODS

In our study, four tagging SNPs in the COMT gene (rs933271, rs740603, rs4680, rs4646316) were genotyped in a nonclinical Hungarian sample (n=939). We investigated the association between the COMT gene and rumination scores measured by the Ruminative Response Scale using haplotype trend regression.

RESULTS

We found a significant association between COMT haplotypes and rumination scores (p=0.013) but no significant association was apparent between the functional Val158Met polymorphism (rs4680) and rumination in any genetic model.

DISCUSSION

Variations in the COMT gene exert complex effects on susceptibility to depression involving intermediate phenotypes, such as rumination and also impulsivity, as we previously demonstrated. Both rumination and impulsivity represent maladaptive cognitive styles that can lead to depressive state by influencing the response to negative life events and life stressors. In conclusion, our findings provide evidence that in addition to other genes, COMT also has a significant role in the development of depression, and demonstrate that analysing the complex phenotype associations of genes by haplotype tagging is a powerful method.

[Expression of miR-16 in the hippocampus of depressed adult rats induced by maternal deprivation]

OBJECTIVE

To detect the expression of miR-16 in the hippocampus of a rat depression model induced by maternal deprivation, and to explore whether miR-16 is involved in the pathological process of maternal deprivation-induced depression.

METHODS

Newborn SD rats were randomly divided into a maternal deprivation group (n=17) and a control group (n=17). Rats in the maternal deprivation group experienced maternal deprivation for 6 h per day from 1st to 14th postnatal day, while rats in the control group rats received no treatment. When the rats were 13 weeks old, depression-like behaviors were assessed by forced swimming test and sucrose consumption test, and the expression of hippocampal miR-16 in rats was detected by real-time RT-PCR.

RESULTS

Maternal-deprived rats exhibited significantly longer passive floating time and lower sucrose preference rate than rats in the control group (P<0.05). Maternal-deprivation rats expressed higher level of miR-16 in the hippocampus than rats in the control group, and the expression level of miR-16 was significantly associated with the passive floating time (r=0.65, P<0.05) and the sucrose preference rate (r=-0.59, P<0.05).

CONCLUSION

Maternal deprivation can induce depressive behaviors in rats and increase the expression of miR-16 in the hippocampus in rats. MiR-16 may be involved in the pathological mechanism of the maternal deprivation-induced depression.

Modeling the direction of causation between cross-sectional measures of disrupted sleep, anxiety and depression in a sample of male and female Australian twins

The direction of causation between measures of disrupted sleep, anxiety and depression is not well understood. Under certain conditions, cross-sectional analysis based on genetically informative data can provide important information about the direction of causation between variables. Two community-based samples of 7235 Australian twins aged 18-87 years were mailed an extensive questionnaire that covered a wide range of personality and behavioral measures. Included were self-report measures of disrupted sleep, as well as symptoms of anxiety and depression. Among all females, modeling the direction of causation did not support the hypothesis of sleep having a direct causal impact on risk of anxiety or depression. Among older females, we found evidence that both anxiety and depression interact reciprocally with disrupted sleep, whereas among younger women both anxiety and depression appear to have a causal impact on sleep. Results for males were equivocal. The nosological implications of our findings are discussed.

A new clinical evidence-based gene-environment interaction model of depression

In our current understanding of mood disorders, the role of genes is diverse including the mediation of the effects of provoking and protective factors. Different or partially overlapping gene sets play a major role in the development of personality traits including also affective temperaments, in the mediation of the effects of environmental factors, and in the interaction of these elements in the development of depression. Certain genes are associated with personality traits and temperaments including e.g., neuroticism, impulsivity, openness, rumination and extroversion. Environmental factors consist of external (early and provoking life events, seasonal changes, social support etc.) and internal factors (hormones, biological rhythm generators, comorbid disorders etc). Some of these environmental factors, such as early life events and some prenatal events directly influence the development of personality traits and temperaments. In the NEWMOOD cohort polymorphisms of the genes of the serotonin transporter, 5-HT1A, 5-HT1B and 5-HT2A and endocannabinoid CB1 receptors, tryptophan hydroxylase, CREB1, BDNF and GIRK provide evidence for the involvement of these genes in the development of depression. Based on their role in this process they could be assigned to different gene sets. The role of certain genes, such as promoter polymorphisms of the serotonin transporter (5-HTTLPR) and CB1 receptor has been shown in more than one of the above factors. Furthermore, gene-gene interactions of these promoters associated with anxiety suggest the application of these polymorphisms in personalized medicine. In this review we introduce a new model including environmental factors, genes, trait and temperament markers based on human genetic studies.

Interaction of sex steroid hormones and brain-derived neurotrophic factor-tyrosine kinase B signalling: relevance to schizophrenia and depression

Sex steroid hormones and neurotrophic factors are involved in pruning and shaping the developing brain and have been implicated in the pathogenesis of neurodevelopmental disorders. Sex steroid hormones are also involved in the regulation of brain-derived neurotrophic factor expression. A review of the literature is provided on the relationship between brain-derived neurotrophic factor and sex steroid hormones, as well as the mechanisms behind this interaction, in the context of how this relationship may be involved in the development of neurodevelopmental psychiatric illnesses, such as schizophrenia and depression.

5-HTTLPR and early childhood adversities moderate cognitive and emotional processing in adolescence

BACKGROUND

Polymorphisms in the promoter region of the serotonin transporter gene (5-HTTLPR) and exposure to early childhood adversities (CA) are independently associated with individual differences in cognitive and emotional processing. Whether these two factors interact to influence cognitive and emotional processing is not known.

METHODOLOGY AND PRINCIPAL FINDINGS

We used a sample of 238 adolescents from a community study characterised by the presence of the short allele of 5-HTTLPR (LL, LS, SS) and the presence or absence of exposure to CA before 6 years of age. We measured cognitive and emotional processing using a set of neuropsychological tasks selected predominantly from the CANTAB® battery. We found that adolescents homozygous for the short allele (SS) of 5-HTTLPR and exposed to CA were worse at classifying negative and neutral stimuli and made more errors in response to ambiguous negative feedback. In addition, cognitive and emotional processing deficits were associated with diagnoses of anxiety and/or depressions.

CONCLUSION AND SIGNIFICANCE

Cognitive and emotional processing deficits may act as a transdiagnostic intermediate marker for anxiety and depressive disorders in genetically susceptible individuals exposed to CA.

Aberrant apolipoprotein E expression and cognitive dysfunction in patients with poststroke depression

BACKGROUND

Apolipoprotein E (ApoE) is associated with some diseases with cognitive function defect.

AIMS

The purpose of this study was to examine the influence of ApoE on poststroke depression (PSD) risk and to define objective markers for diagnosis.

METHODS

The cognitive function, serum ApoE, and peripheral mononuclear blood cell ApoE mRNA expression of patients with PSD were compared to age-matched control patients with stroke and healthy volunteers. Sixty-seven patients with stroke were selected according to the cerebral infarction diagnosis standard of the Fourth National Cerebrovascular Disease Conference and divided into a PSD group (28 patients, 43-76 years old) or a control stroke group (39 patients, 43-78 years old) using the Hamilton Rating Scale for Depression, and compared to 40 healthy volunteers (42-78 years old). Cognitive function was evaluated by analysis of event-related potentials (ERPs), while expression of ApoE mRNA was determined by quantitative reverse transcription-polymerase chain reaction and serum ApoE by ELISA.

RESULTS

The latencies of ERP components N2 and P3 were prolonged, and the P3 amplitude was lower in the PSD group compared to the control stroke group and healthy controls (p<0.01). There were no significant group differences in N1 and P2 latencies (all p>0.05). The latency of N2 was positively correlated to the P3 latency in the PSD group (p<0.05). No associations were detected between P3 amplitude, expression of ApoE mRNA, and serum ApoE in the PSD group (all p>0.05). The ERP results indicated that patients with PSD were significantly slower at identifying a target stimulus, suggesting deficits in perception and/or cognitive processing. Peripheral expression of ApoE mRNA was lower in the PSD group than the control stroke group (p<0.701) while serum ApoE was higher than in the control stroke group (p<0.05), possibly reflecting a feedback reduction in expression.

CONCLUSION

We suggest that aberrant serum ApoE together with abnormalities in some ERP components may be useful markers for assessment of PSD risk and clinical diagnosis.

Up-regulation of leucocytes genes implicated in telomere dysfunction and cellular senescence correlates with depression and anxiety severity scores

Background

Major depressive disorder (MDD) is frequently associated with chronic medical illness responsible of increased disability and mortality. Inflammation and oxidative stress are considered to be the major mediators of the allostatic load, and has been shown to correlate with telomere erosion in the leucocytes of MDD patients, leading to the model of accelerated aging. However, the significance of telomere length as an exclusive biomarker of aging has been questioned on both methodological and biological grounds. Furthermore, telomeres significantly shorten only in patients with long lasting MDD. Sensitive and dynamic functional biomarkers of aging would be clinically useful to evaluate the somatic impact of MDD.

Methodology

To address this issue we have measured in the blood leucocytes of MDD patients (N = 17) and controls (N = 16) the expression of two genes identified as robust biomarkers of human aging and telomere dysfunction: p16^INK4a and STMN1. We have also quantified the transcripts of genes involved in the repair of oxidative DNA damage at telomeres (OGG1), telomere regulation and elongation (TERT), and in the response to biopsychological stress (FOS and DUSP1).

Results

The OGG1, p16^INK4a, and STMN1 gene were significantly up-regulated (25 to 100%) in the leucocytes of MDD patients. Expression of p16^INK4a and STMN1 was directly correlated with anxiety scores in the depression group, and that of p16^INK4a, STMN and TERT with the depression and anxiety scores in the combined sample (MDD plus controls). Furthermore, we identified a unique correlative pattern of gene expression in the leucocytes of MDD subjects.

Conclusions

Expression of p16^INK4 and STMN1 is a promising biomarker for future epidemiological assessment of the somatic impact of depressive and anxious symptoms, at both clinical and subclinical level in both depressive patients and general population.

[Epigenetics of early interactions, depression and schizophrenia]

Epigenetics is the study of the variations of genetic expression that occur not because of differences in DNA structure, but because of chromatin alternations that modulate DNA transcription. The mechanisms of epigenetics are thus the link between genome and phenotype. This article will explore the best known epigenetic mechanisms, namely DNA methylation and histone modifications and how they may lead to the emergence of depression and schizophrenia. The practical interest of this research is an understanding of the role of early interactions in the development of mental illness. Hopefully this understanding will lead to therapeutic pathways aimed at neutralizing these unfavourable epigenetic influences, with the ultimate goal of prevention of mental illness.

Chronic fluoxetine treatment affects gene expression of catecholamine enzymes in the heart of depression model rats

Depression is associated with increased risk of coronary heart diseases. Selective serotonin reuptake inhibitors (SSRIs) have been proved to be very effective in normalizing symptoms of depression, but the data on possible influence of these drugs on cardiovascular function is controversial. Applying Taqman RT-PCR assay, the effect of chronic treatment with a SSRI antidepressant fluoxetine has been investigated on gene expression of catecholamine biosynthetic enzymes in all four heart chambers of rats with signs of depression. Depression was induced by exposing the animals to chronic unpredictable mild stress (CUMS). Tyrosine-hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) mRNA levels were decreased both in right and left atria, while phenylethanolamine N-methyltransferase (PNMT) mRNAs were increased in left atria and both ventricles of depression model rats. Fluoxetine elevated gene expression of TH and DBH in atria, but did not influence this process in the ventricles. Also, this antidepressant did not express a significant effect on the level of PNMT mRNA both in atria and ventricles. These results indicate that fluoxetine acted stimulating noradrenaline synthesis in the heart, which could lead to increased risk of heart disease.

Growth in externalizing and internalizing problems in childhood: a prospective study of psychopathology across three generations

Three generations of participants were assessed over approximately 27 years, and intergenerational prediction models of growth in the third generation's (G3) externalizing and internalizing problems across ages 3-9 years were examined. The sample included 103 fathers and mothers (G2), at least 1 parent (G1) for all of the G2 fathers (99 mothers, 72 fathers), and 185 G3 offspring (83 boys, 102 girls) of G2, with prospective data available on the G2 fathers beginning at age 9 years. Behavior of the G2 mother, along with father contact and mother age at birth were included in the models. Intergenerational associations in psychopathology were modest, and much of the transmission occurred via contextual risk within the family of procreation.

The role of limbic system irritability in linking history of childhood maltreatment and psychiatric outcomes in low-income, high-risk women: moderation by FK506 binding protein 5 haplotype

Childhood maltreatment is associated with lasting changes in neuroendocrine regulation, alterations in brain structure and function, and symptoms of "limbic irritability." Limbic irritability symptoms include somatic, sensory, and behavioral phenomena and may stem from increased excitatory neurotransmission following maltreatment. We tested the hypotheses that child maltreatment is indirectly associated with depressive and dissociative symptomatology via indicators of limbic irritability and that variation within the FK506 binding protein 5 gene (FKBP5), a gene involved in glucorticoid receptor functioning, moderates these effects. The sample consisted of high-risk, low-income women (N = 236) living in an inner-city environment. Child maltreatment, limbic irritability, and symptoms of depression and dissociation were measured cross-sectionally using self-report assessments. Haplotype analyses were conducted across four FKBP5 single nucleotide polymorphisms: rs3800373, rs9296158, rs1360870, and rs9470080. Path analysis using bootstrapping procedures was performed to test hypotheses regarding indirect and conditional indirect effects. We found significant indirect effects of maltreatment on depression (β = 0.088, p < .01) and dissociation (β = 0.105, p < .01) via limbic irritability. In addition, variation within FKBP5 moderated these significant indirect effects. For individuals with one to two copies of the CATT haplotype, the indirect effects of maltreatment on depression (β = 0.137, p < .01) and dissociation (β = 0.132, p < .01) via limbic irritability were significant, whereas the indirect paths were not significant for individuals with no copies of this haplotype (depression: β = 0.037, p > .05; dissociation: β = 0.002, p > .05). These results add to the growing evidence that child maltreatment may lead to symptoms of internalizing psychopathology through its impact on the limbic system. In addition, this study revealed a potential role of FKBP5 gene variants in contributing to risk for limbic system dysfunction.

Serotonin transporter gene as a predictor of stress generation in depression

Research suggests that a polymorphism in the promoter region of the serotonin transporter promoter (5-HTTLPR) interacts with stressful life events to predict depressive onset, with short (s) allele presence associated with greater susceptibility to stressors. However, this research has not considered that depressed individuals often actively generate stressful contexts. Furthermore, little is known about the genetic basis of stress generation. The current study explored the role of 5-HTTLPR genotype in stress generation in a longitudinal sample of 381 adolescents, oversampled for maternal depression, assessed at ages 15 and 20. Genotype did not correlate directly with number or ratings of stressful life events. However, 5-HTTLPR genotype interacted with depression at age 15 to predict dependent stressful events at age 20. Specifically, participants with one or more s alleles showed a stronger association between age 15 depression and age 20 dependent and interpersonal events than long allele homozygotes. Results imply that the 5-HTTLPR genotype predicts reciprocal associations between stress and depression, indicating a more complex relationship between stress, depression, and their genetic underpinnings than previously suggested.

Selection of suitable housekeeping genes for real-time quantitative PCR in CD4(+) lymphocytes from asthmatics with or without depression

OBJECTIVE

No optimal housekeeping genes (HKGs) have been identified for CD4(+) T cells from non-depressive asthmatic and depressive asthmatic adults for normalizing quantitative real-time PCR (qPCR) assays. The aim of present study was to select appropriate HKGs for gene expression analysis in purified CD4(+) T cells from these asthmatics.

METHODS

Three groups of subjects (Non-depressive asthmatic, NDA, n = 10, Depressive asthmatic, DA, n = 11, and Healthy control, HC, n = 10 respectively) were studied. qPCR for 9 potential HKGs, namely RNA, 28S ribosomal 1 (RN28S1), ribosomal protein, large, P0 (RPLP0), actin, beta (ACTB), cyclophilin A (PPIA), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphoglycerate kinase 1 (PGK1), beta-2-microglobulin (B2M), glucuronidase, beta (GUSB) and ribosomal protein L13a (RPL13A), was performed. Then the data were analyzed with three different applications namely BestKeeper, geNorm, and NormFinder.

RESULTS

The analysis of gene expression data identified B2M and RPLP0 as the most stable reference genes and showed that the level of PPIA was significantly different among subjects of three groups when the two best HKGs identified were applied. Post-hoc analysis by Student-Newman-Keuls correction shows that depressive asthmatics and non-depressive asthmatics exhibited lower expression level of PPIA than healthy controls (p<0.05).

CONCLUSIONS

B2M and RPLP0 were identified as the most optimal HKGs in gene expression studies involving human blood CD4(+) T cells derived from normal, depressive asthmatics and non-depressive asthmatics. The suitability of using the PPIA gene as the HKG for such studies was questioned due to its low expression in asthmatics.

Molecular pathway reconstruction and analysis of disturbed gene expression in depressed individuals who died by suicide

Molecular mechanisms behind the etiology and pathophysiology of major depressive disorder and suicide remain largely unknown. Recent molecular studies of expression of serotonin, GABA and CRH receptors in various brain regions have demonstrated that molecular factors may contribute to the development of depressive disorder and suicide behaviour. Here, we used microarray analysis to examine the expression of genes in brain tissue (frontopolar cortex) of individuals who had been diagnosed with major depressive disorder and died by suicide, and those who had died suddenly without a history of depression. We analyzed the list of differentially expressed genes using pathway analysis, which is an assumption-free approach to analyze microarray data. Our analysis revealed that the differentially expressed genes formed functional networks that were implicated in cell to cell signaling related to synapse maturation, neuronal growth and neuronal complexity. We further validated these data by randomly choosing (100 times) similarly sized gene lists and subjecting these lists to the same analyses. Random gene lists did not provide highly connected gene networks like those generated by the differentially expressed list derived from our samples. We also found through correlational analysis that the gene expression of control participants was more highly coordinated than in the MDD/suicide group. These data suggest that among depressed individuals who died by suicide, wide ranging perturbations of gene expression exist that are critical for normal synaptic connectively, morphology and cell to cell communication.

Abnormal hippocampal BDNF and miR-16 expression is associated with depression-like behaviors induced by stress during early life

Some environmental stressors lead to the onset of depression via inhibiting hippocampal BDNF expression, but other environmental stressors-induced depression exhibits no change in BDNF expression. The underlying mechanisms behind the divergence remain unknown. In this study, depression-like behaviors were induced in rats by maternal deprivation (MD) and chronic unpredictable stress (CUPS). Depression-like behaviors were tested by open field test, forced swimming test, and sucrose consumption test. BDNF and miR-16 expressions in the hippocampus were examined by real-time PCR. MD and CUPS rats crawled less distance, exhibited decreased vertical activity, and produced more fecal pellets than control rats in the open field test. However, MD rats crawled less distance and produced significantly less fecal pellets than CUPS rats. In the forced swimming and sucrose consumption tests, CUPS and MD rats exhibited longer floating time and consumed less sucrose than control rats, but MD rats exhibited shorter floating time and consumed less sucrose than CUPS rats. MD but not CUPS rats showed lower BDNF mRNA and higher miR-16 expression than control rats. In MD rats, BDNF mRNA expression negatively correlated with the expression of miR-16. BDNF expression positively correlated with the total distance rats crawled and vertical activity in the open field test while miR-16 expression negatively correlated the two behaviors. BDNF positively correlated with sucrose preference rate while miR-16 negatively correlated with sucrose preference rate of the sucrose consumption test. Our study suggests that MD and CUPS induced different depression-like behaviors in rats. Depression induced by MD but not CUPS was significantly associated with upregulation of miR-16 and possibly subsequent downregulation of BDNF in hippocampus.

Disentangling the causal inter-relationship between negative life events and depressive symptoms in women: a longitudinal twin study

BACKGROUND

Negative life events are strongly associated with the development of depression. However, the etiologic relationship between life events and depression is complex. Evidence suggests that life events can cause depression, and depression increases the risk for life events. Additionally, third factors influencing both phenotypes may be involved. In this work we sought to disentangle these relationships using a genetically informative longitudinal design.

METHOD

Adult female twins (n=536, including 281 twin pairs) were followed up for measurements of negative life event exposure and depressive symptoms. Four follow-ups were completed, each approximately 3 months apart. Model fitting was carried out using the Mx program.

RESULTS

The best-fitting model included causal paths from life events to depressive symptoms for genetic and shared environmental risk factors, whereas paths from depressive symptoms to life events were apparent for shared environmental factors. Shared latent influence on both phenotypes was found for individual-specific effects.

CONCLUSIONS

Life events and depressive symptoms have complex inter-relationships that differ across sources of variance. The results of the model, if replicated, indicate that reducing life event exposure would reduce depressive symptoms and that lowering depressive symptoms would decrease the occurrence of negative life events.

Differential sensitivity to life stress in FMR1 premutation carrier mothers of children with fragile X syndrome

OBJECTIVE

The premutation of the FMR1 gene (defined as between 55 and 200 CGG repeats) is estimated to affect 1 in 149 females and 1 in 643 males, and some people who carry the FMR1 premutation display signs of impairment.

METHOD

This study focuses on 82 premutation carrier mothers (M age = 51.4 years; SD = 7.7) of adolescent and adult children with fragile X syndrome (FXS). A Gene × Environment interaction approach examined the ways in which the experience of negative life events interacts with genetic vulnerability to predict depressive symptoms, anxiety, and daily cortisol levels.

RESULTS

The associations of life events with all 3 dependent measures were associated with CGG repeat length but in a curvilinear manner. Mothers with midsize CGG repeats who experienced above-average numbers of negative life events in the previous year had more depressive symptoms and anxiety and had a blunted cortisol awakening response, as compared with those with higher or lower repeat lengths. However, mothers with midsize CGG repeats who experienced below-average numbers of negative life events in the previous year had the lowest levels of depressive symptoms and anxiety, and they exhibited the typical cortisol response to awakening, meeting the criteria for differential susceptibility.

CONCLUSIONS

This research extends our understanding of the phenotypic effects of the expansion of the FMR1 gene, and it adds to the growing literature on the curvilinear relationship between CGG repeat length and mental and physical health.

Genome-wide association uncovers shared genetic effects among personality traits and mood states

Measures of personality and psychological distress are correlated and exhibit genetic covariance. We conducted univariate genome-wide SNP (~2.5 million) and gene-based association analyses of these traits and examined the overlap in results across traits, including a prediction analysis of mood states using genetic polygenic scores for personality. Measures of neuroticism, extraversion, and symptoms of anxiety, depression, and general psychological distress were collected in eight European cohorts (n ranged 546-1,338; maximum total n = 6,268) whose mean age ranged from 55 to 79 years. Meta-analysis of the cohort results was performed, with follow-up associations of the top SNPs and genes investigated in independent cohorts (n = 527-6,032). Suggestive association (P = 8 × 10(-8)) of rs1079196 in the FHIT gene was observed with symptoms of anxiety. Other notable associations (P < 6.09 × 10(-6)) included SNPs in five genes for neuroticism (LCE3C, POLR3A, LMAN1L, ULK3, SCAMP2), KIAA0802 for extraversion, and NOS1 for general psychological distress. An association between symptoms of depression and rs7582472 (near to MGAT5 and NCKAP5) was replicated in two independent samples, but other replication findings were less consistent. Gene-based tests identified a significant locus on chromosome 15 (spanning five genes) associated with neuroticism which replicated (P < 0.05) in an independent cohort. Support for common genetic effects among personality and mood (particularly neuroticism and depressive symptoms) was found in terms of SNP association overlap and polygenic score prediction. The variance explained by individual SNPs was very small (up to 1%) confirming that there are no moderate/large effects of common SNPs on personality and related traits.