Dirk Moser

Interaction of Serotonin Transporter Gene-Linked Polymorphic Region and Stressful Life Events Predicts Cortisol Stress Response

There has been significant controversy whether stressful life events (SLEs) experienced over the lifespan may elevate the risk of depression in individuals who are homozygous for the short (S) allele of the repeat length polymorphism (5-HTTLPR) in the regulatory region of the serotonin transporter gene (SLC6A4), compared with individuals homozygous for the long (L) allele. On the basis of the hypothesis that age may be a critical variable, by which such a gene-by-environment interaction may be present in younger adults, but not in older adults and in children, aim of this study was to investigate the role of 5-HTTLPR and SLEs on the endocrine stress response in multiple age cohorts. A total of 115 children (8–12 years), 106 younger adults (18–31 years), and 99 older adults (54–68 years) were subjected to the Trier Social Stress Test (TSST) and structured interviews on SLEs. The TSST induced significant endocrine stress responses in all groups. There was a main effect of genotype in younger and older adults with individuals homozygous for the more active L allele showing a significantly larger cortisol response to the TSST than individuals carrying at least one of the low-expressing S alleles. As predicted, there was a significant interaction of 5-HTTLPR genotype and SLEs, but this interaction was only significant in younger adults and only when the measured SLEs had occurred during the first 5 years of life, suggesting that both age and the specific type of SLE has a role in whether a significant gene–environment interaction is observed.

Characterization of a glucocorticoid receptor gene (GR, NR3C1) promoter polymorphism reveals functionality and extends a haplotype with putative clinical relevance

Hyperactivity of the hypothalamus–pituitary–adrenal (HPA) axis has been associated with the etiology of major depression. One of the factors underlying altered glucocorticoid signaling might be variability of the glucocorticoid receptor gene (GR, NR3C1). GR polymorphisms have been associated with variability in glucocorticoid sensitivity and endocrine responses to psychosocial stress. Furthermore, a common GR SNP (rs10482605), located in the promoter region, has been associated with major depression. We performed functional characterization of this SNP in vitro using a reporter gene assay under different stimulation conditions. Furthermore, we genotyped 219 subjects previously genotyped for four common GR SNPs to further characterize GR haplotype structure. The minor C allele of the rs10482605 SNP showed reduced transcriptional activity under unstimulated conditions and under different stimulation conditions in two brain derived cell lines. Linkage analyses revealed that the rs10482605 SNP is in high linkage disequilibrium with a A/G SNP in exon 9beta (rs6198), associated with relative glucocorticoid resistance and increased GRbeta mRNA stability. We provide evidence that two functional GR SNPs in linkage disequilibrium are responsible for both regulation of GR expression and mRNA stability. This newly characterized haplotype could increase the risk for the development of stress related disorders, including major depression.

The glucocorticoid receptor gene exon 1-F promoter is not methylated at the NGFI-A binding site in human hippocampus

Recent research has demonstrated that early life experience, such as variation in maternal care, can have a profound impact on the physiological and endocrine stress response of Rattus norvegicus. Low maternal care resulted in increased methylation of the nerve growth factor-inducible protein A (NGFI-A, EGR1) binding site located in the hippocampal glucocorticoid receptor gene (Nr3c1) exon 17 promoter, leading to decreased Nr3c1 expression, which results in a reduced efficiency of glucocorticoid-mediated negative feedback on hypothalamus–pituitary–adrenal axis activity. The human glucocorticoid receptor gene (NR3C1) has a highly similar 5′ structure compared to the rat, and the human alternative exon 1-F is the orthologue to the rat exon 17. Based upon the evidence from rats, and the high sequence identity of the regulatory sequences, we examined the methylation pattern of the corresponding NGFI-A binding site in the human glucocorticoid receptor exon 1-F specific promoter in post mortem hippocampal tissue. In contrast to the findings in rats, neither of the two CpG motifs within the NGFI-A binding site was methylated in the 32 subjects investigated. These observations might reflect different promoter methylation patterns in humans and rats.

Serotonin transporter gene variation and stressful life events impact processing of fear and anxiety

Genetic variation of the serotonin transporter (5-HTT) has been associated with fear- and anxiety-related behaviours. The amygdala is considered crucial in emotional modulation and stronger amygdala reactivity in response to fearful stimuli has been found in carriers of the short (S) allele of the 5-HTT gene in imaging studies. Additionally, reactivity of amygdala-innervated effectory systems is also of particular interest. We recently reported the impact of a functional polymorphism in the transcriptional control region of the serotonin transporter gene (5-HTTLPR) on the acoustic startle reflex. Here, we attempted to replicate and extend these findings. Startle magnitudes to intense noise bursts as measured with the eyeblink response were recorded in 106 healthy volunteers during baseline without additional stimulation and while they viewed pictures of three valence conditions: unpleasant, pleasant and neutral. Subjects were genotyped for the tri-allelic functional polymorphism 5-HTTLPR. In replication of our previous findings we found that carriers of the low-expressing S or LG alleles exhibited stronger overall startle responses across conditions than LA/LA homozygotes, while there were no differences in emotional startle modulation between the two genetic groups. In addition, we found that the recent experience of stressful life events resulted in overall higher startle responses and less startle habituation across blocks. The results replicate and emphasize the role of 5-HTTLPR and stress on the overall startle response as a possible genetically driven endophenotype for anxiety-related behaviour.

Interaction Effect of D4 Dopamine Receptor Gene and Serotonin Transporter Promoter Polymorphism on the Cortisol Stress Response

Genetic variation of the serotonin transporter (SCL6A4, 5-HTT) has been associated with fear- and anxiety-related behaviors, while a polymorphism in exon III of the D4 dopamine receptor gene (DRD4) has been linked to novelty seeking. The dopaminergic and the serotonergic neurotransmitter system have been found to modulate the amygdala-connected circuitries that are crucial in emotional modulation and response to fearful stimuli. Additionally, reactivity of amygdala-innervated effector systems is also essential for our understanding of anxiety-related behaviors. Here, we used the stress-induced activation of the hypothalamic-pituitary-adrenal axis to investigate the impact of 5-HTTLPR and DRD4 on the cortisol stress response in 84 healthy adults. Saliva cortisol was measured during and after the Trier Social Stress Test. We found a significant main effect of DRD4: Carriers of the 7R allele exhibited lower cortisol responses. Additionally, a DRD4 by 5-HTTLPR interaction emerged: 5-HTTLPR LA/LA homozygotes showed a lower cortisol response than did S or LG allele carriers but only if they possessed at least one copy of the DRD4 7R allele. The results point to independent and joint effects of these polymorphisms on stress responsivity.

Functional Analysis of a Potassium-Chloride Co-Transporter 3 ( SLC12A6 ) Promoter Polymorphism Leading to an Additional DNA Methylation Site

The human potassium-chloride co-transporter 3 (KCC3, SLC12A6) is involved in cell proliferation and in electro-neutral movement of ions across the cell membrane. The gene (SLC12A6) is located on chromosome 15q14, a region that has previously shown linkage with bipolar disorder, schizophrenia, rolandic epilepsy, idiopathic generalized epilepsy, autism and attention deficit/hyperactivity disorder. Furthermore, recessively inherited mutations of SLC12A6 cause Andermann syndrome, characterized by agenesis of the corpus callosum, which is associated with peripheral neuropathy and psychoses. Recently, we have demonstrated the association of two G/A promoter polymorphisms of SLC12A6 with bipolar disorder in a case–control study, and familial segregation of the rare variants as well as a trend toward association with schizophrenia. To investigate functional consequences of these polymorphisms, lymphocyte DNA was extracted, bisulfite modified, and subsequently sequenced. To investigate SLC12A6 promoter activity, various promoter constructs were generated and analyzed by luciferase reporter gene assays. We provide evidence that the G- allele showed a significant reduction of reporter gene expression. In human lymphocytes, the allele harboring the rare upstream G nucleotide was found to be methylated at the adjacent C position, possibly accountable for tissue-specific reduction in gene expression in vivo. Here we demonstrate functionality of an SNP associated with psychiatric disease and our results may represent a functional link between genetic variation and an epigenetic modification.

Attention-deficit/hyperactivity disorder phenotype is influenced by a functional catechol-O-methyltransferase variant

The catechol-O-methyltransferase gene (COMT) plays a crucial role in the metabolism of catecholamines in the frontal cortex. A single nucleotide polymorphism (Val158Met SNP, rs4680) leads to either methionine (Met) or valine (Val) at codon 158, resulting in a three- to fourfold reduction in COMT activity. The aim of the present study was to assess the COMT Val158Met SNP as a risk factor for attention-deficit/hyperactivity disorder (ADHD), ADHD symptom severity and co-morbid conduct disorder (CD) in 166 children with ADHD. The main finding of the present study is that the Met allele of the COMT Val158Met SNP was associated with ADHD and increased ADHD symptom severity. No association with co-morbid CD was observed. In addition, ADHD symptom severity and early adverse familial environment were positive predictors of lifetime CD. These findings support previous results implicating COMT in ADHD symptom severity and early adverse familial environment as risk factors for co-morbid CD, emphasizing the need for early intervention to prevent aggressive and maladaptive behavior progressing into CD, reducing the overall severity of the disease burden in children with ADHD.

Epigenetic regulation of lateralized fetal spinal gene expression underlies hemispheric asymmetries

Lateralization is a fundamental principle of nervous system organization but its molecular determinants are mostly unknown. In humans, asymmetric gene expression in the fetal cortex has been suggested as the molecular basis of handedness. However, human fetuses already show considerable asymmetries in arm movements before the motor cortex is functionally linked to the spinal cord, making it more likely that spinal gene expression asymmetries form the molecular basis of handedness. We analyzed genome-wide mRNA expression and DNA methylation in cervical and anterior thoracal spinal cord segments of five human fetuses and show development-dependent gene expression asymmetries. These gene expression asymmetries were epigenetically regulated by miRNA expression asymmetries in the TGF-β signaling pathway and lateralized methylation of CpG islands. Our findings suggest that molecular mechanisms for epigenetic regulation within the spinal cord constitute the starting point for handedness, implying a fundamental shift in our understanding of the ontogenesis of hemispheric asymmetries in humans. DOI: http://dx.doi.org/10.7554/eLife.22784.001

Altered stress-induced regulation of genes in monocytes in adults with a history of childhood adversity

Exposure to serious or traumatic events early in life can lead to persistent alterations in physiological stress response systems, including enhanced cross talk between the neuroendocrine and immune system. These programming effects may be mechanistically involved in mediating the effects of adverse childhood experience on disease risk in adulthood. We investigated hormonal and genome-wide mRNA expression responses in monocytes to acute stress exposure, in a sample of healthy adults (n=30) with a history of early childhood adversity, and a control group (n=30) without trauma experience. The early adversity group showed altered hypothalamus-pituitary-adrenal axis responses to stress, evidenced by lower ACTH and cortisol responses. Analyses of gene expression patterns showed that stress-responsive transcripts were enriched for genes involved in cytokine activity, cytokine–cytokine receptor interaction, chemokine activity, and G-protein coupled receptor binding. Differences between groups in stress-induced regulation of gene transcription were observed for genes involved in steroid binding, hormone activity, and G-protein coupled receptor binding. Transcription factor binding motif analysis showed an increased activity of pro-inflammatory upstream signaling in the early adversity group. We also identified transcripts that were differentially correlated with stress-induced cortisol increases between the groups, enriched for genes involved in cytokine–cytokine receptor interaction and glutamate receptor signaling. We suggest that childhood adversity leads to persistent alterations in transcriptional control of stress-responsive pathways, which—when chronically or repeatedly activated—might predispose individuals to stress-related psychopathology.

Haploinsufficiency of the SERPINA6 gene is associated with severe muscle fatigue: A de novo mutation in corticosteroid-binding globulin deficiency

Summary.Corticosteroid-binding globulin (SERPINA6) deficiency is an extremely rare hereditary disorder characterized by reduced corticosteroid-binding capacity with normal or low plasma corticosteroid-binding globulin concentration, and normal or low basal cortisol levels associated with hypo-/hypertension and muscle fatigue. Here, we present a patient with severe muscle fatigue, normal blood pressure, and abnormal high saliva cortisol levels following a standardized stress test. This patient was found heterozygous for a de novo 367 asparagine-encoding variant of the corticosteroid-binding globulin gene, previously described as “transcortin Lyon”. Both parents were homozygous for the (“wildtype”) 367 aspartate-encoding allele. To the best of our knowledge, this case represents the first de novo mutation reported for corticosteroid-binding globulin deficiency, implicating a pathogenic role of variants of SERPINA6 in some cases of muscle fatigue.