Catharina Lavebratt

Epigenetic aberrations in leukocytes of patients with schizophrenia: association of global DNA methylation with antipsychotic drug treatment and disease onset

Even though schizophrenia has a strong hereditary component, departures from simple genetic transmission are prominent. DNA methylation has emerged as an epigenetic explanatory candidate of schizophrenias nonmendelian characteristics. To investigate this assumption, we examined genome‐wide (global) and gene‐specific DNA methylation levels, which are associated with genomic stability and gene expression activity, respectively. Analyses were conducted using DNA from leukocytes of patients with schizophrenia and controls. Global methylation results revealed a highly significant hypomethylation in patients with schizophrenia (P<2.0×10‐6) and linear regression among patients generated a model in which antipsychotic treatment and disease onset explained 11% of the global methylation variance (adjusted R2=0.11, ANOVA P>0.001). Specifically, haloperidol was associated with higher (“control‐like”) methylation (P=0.001), and early onset (a putative marker of schizophrenia severity) was associated with lower methylation (P=0.002). With regard to the gene‐specific methylation analyses, and in accordance with the dopamine hypothesis of psychosis, we found that the analyzed region of S‐COMT was hypermethylated in patients with schizophrenia (P=0.004). In summary, these data support the notion of a dysregulated epigenome in schizophrenia, which, at least globally, is more pronounced in early‐onset patients and can be partly rescued by antipsychotic medication. In addition, blood DNA‐methylation signatures show promise of serving as a schizophrenia biomarker in the future.—Melas, P. A., Rogdaki, M., Ösby, U., Schalling, M., Lavebratt, C., Ekström, T. J. Epigenetic aberrations in leukocytes of patients with schizophrenia: association of global DNA methylation with antipsychotic drug treatment and disease onset. FASEB J. 26, 2712‐2718 (2012). www.fasebj.org

Genetic and epigenetic associations of MAOA and NR3C1 with depression and childhood adversities

Monoamine oxidase A (MAOA) harbours a polymorphic upstream variable-number tandem repeat (u-VNTR). The MAOA-L allele of the u-VNTR leads to decreased gene expression levels in vitro and has been found to increase the risk of conduct disorder in males with childhood adversities. Early-life adversities have been associated with hypermethylation of the glucocorticoid receptor (NR3C1). In this study, we first performed a genetic association analysis of the MAOA u-VNTR using individuals with depression (n = 392) and controls (n = 1276). Next, DNA methylation analyses of MAOA and NR3C1 were performed using saliva samples of depressed and control subgroups. Adult MAOA-L females with childhood adversities were found to have a higher risk of developing depression (p = 0.006) and overall MAOA methylation levels were decreased in depressed females compared to controls (mean depressed, 42% vs. mean controls, 44%; p = 0.04). One specific childhood adversity [early parental death (EPD)] was associated with hypermethylation of NR3C1 close to an NGFI-A binding site (mean EPD, 19% vs. mean non-EPD, 14%; p = 0.005). Regression analysis indicated that this association may be mediated by the MAOA-L allele (adjusted R² = 0.24, ANOVA: F = 23.48, p < 0.001). Conclusively: (1) depression in females may result from a gene × childhood-adversity interaction and/or a dysregulated epigenetic programming of MAOA; (2) childhood-adversity subtypes may differentially impact DNA methylation at NR3C1; (3) baseline MAOA-genotypic variations may affect the extent of NR3C1 methylation.

Variations in FKBP5 and BDNF genes are suggestively associated with depression in a Swedish population-based cohort.

BACKGROUND Genetic variations in FKBP5, BDNF, P2RX7 and CACNA1 are current candidates for involvement in depression. METHODS The single nucleotide polymorphisms FKBP5:rs1360780, BDNF:rs6265 (Val66Met), P2RX7:2230912 (Gln460Arg) and CACNA1C:rs1006737 were genotyped in DNA from 457 depression cases (major depression, dysthymia, and mixed anxiety depression) and 2286 healthy controls with no symptom of psychopathology. Cases and controls were derived from a large well-characterized longitudinal population-based sample of adult Swedes with data on life situation and life history. Association to depression was analyzed with and without consideration to problems during childhood and negative life events last year. RESULTS FKBP5:rs1360780 allele T and genotype TT were overrepresented in depression for men. Childhood problems and negative life events (two or more) conferred a risk for depression (OR=2.8, 95% CI: 2.2-3.5 and OR=2.9, 95% CI: 2.4-3.7, respectively). The BDNF:rs6265 Met-allele was overrepresented in depression for women with problems during their childhood. No indication for association to depression was found for P2RX7:2230912 and CACNA1C:rs1006737 without or with consideration of childhood problems or negative life events. LIMITATIONS The sample size did not allow exclusion of true association to depression at low odds ratios. There was possibly some recall bias of childhood problems. CONCLUSIONS These data support previous reports on FKBP5:rs1360780 and show a gender difference. Likewise, they support previous reports on BDNF:rs6265 and show involvement of environmental stress. P2RX7:2230912 and CACNA1C:rs1006737 did not have a large or moderate-size effect on depression risk. Further studies are required to estimate the significance of these findings.

Antidepressant treatment is associated with epigenetic alterations in the promoter of P11 in a genetic model of depression

P11 (S100A10) has been associated with the pathophysiology of depression both in human and rodent models. Different types of antidepressants have been shown to increase P11 levels in distinct brain regions and P11 gene therapy was recently proven effective in reversing depressive-like behaviours in mice. However, the molecular mechanisms that govern P11 gene expression in response to antidepressants still remain elusive. In this study we report decreased levels of P11, associated with higher DNA methylation in the promoter region, in the prefrontal cortex of the Flinders Sensitive Line (FSL) genetic rodent model of depression. This hypermethylated pattern was reversed to normal, as indicated by the control line, after chronic administration of escitalopram (a selective serotonin reuptake inhibitor; SSRI). The escitalopram-induced hypomethylation was associated with both an increase in P11 gene expression and a reduction in mRNA levels of two DNA methyltransferases that have been shown to maintain DNA methylation in adult forebrain neurons (Dnmt1 and Dnmt3a). In conclusion, our data further support a role for P11 in depression-like states and suggest that this gene is controlled by epigenetic mechanisms that can be affected by antidepressant treatment.

CRY2 is associated with depression

Background Abnormalities in the circadian clockwork often characterize patients with major depressive and bipolar disorders. Circadian clock genes are targets of interest in these patients. CRY2 is a circadian gene that participates in regulation of the evening oscillator. This is of interest in mood disorders where a lack of switch from evening to morning oscillators has been postulated. Principal Findings We observed a marked diurnal variation in human CRY2 mRNA levels from peripheral blood mononuclear cells and a significant up-regulation (P = 0.020) following one-night total sleep deprivation, a known antidepressant. In depressed bipolar patients, levels of CRY2 mRNA were decreased (P = 0.029) and a complete lack of increase was observed following sleep deprivation. To investigate a possible genetic contribution, we undertook SNP genotyping of the CRY2 gene in two independent population-based samples from Sweden (118 cases and 1011 controls) and Finland (86 cases and 1096 controls). The CRY2 gene was significantly associated with winter depression in both samples (haplotype analysis in Swedish and Finnish samples: OR = 1.8, P = 0.0059 and OR = 1.8, P = 0.00044, respectively). Conclusions We propose that a CRY2 locus is associated with vulnerability for depression, and that mechanisms of action involve dysregulation of CRY2 expression.

Multigenic Control of Disease Severity after Virulent Mycobacterium tuberculosis Infection in Mice

ABSTRACT Following challenge with virulent Mycobacterium tuberculosis, mice of the I/St inbred strain exhibit shorter survival time, more rapid body weight loss, higher mycobacterial loads in organs, and more severe lung histopathology than mice of the A/Sn strain. We previously performed a genome-wide scan for quantitative trait loci (QTLs) that control the severity of M. tuberculosis-triggered disease in [(A/Sn × I/St) F1 × I/St] backcross-1 (BC1) mice and described several QTLs that are significantly or suggestively linked to body weight loss. In the present study we expanded our analysis by including the survival time phenotype and by genotyping 406 (A/Sn × I/St) F2 mice for the previously identified chromosomal regions of interest. The previously identified 12-cM-wide QTL on distal mouse chromosome 3 was designated tbs1 (tuberculosis severity 1); the location of the QTL on proximal chromosome 9 was narrowed to a 9-cM interval, and this QTL was designated tbs2. Allelic variants of the tbs2 locus appeared to be involved in control of both body weight loss and survival time. Also, the data strongly suggested that a QTL located in the vicinity of the H-2 complex on chromosome 17 is involved in control of tuberculosis in mice of both genders, whereas the tbs1 locus seemed to have an effect on postinfection body weight loss in female mice. Interestingly, these loci appeared to interact with each other, which suggests that there might be a basic genetic network for the control of intracellular parasites. Overall, linkage data reported here for F2 mice are in agreement with, and add to, our previous findings concerning the control of M. tuberculosis-triggered disease in the BC1 segregation.

PER2 variantion is associated with depression vulnerability

The circadian clock is driven by transcription–translation feedback loops and regulates rhythms that approximate the 24‐hr day–night cycle or light–dark transitions. Disruptions of the circadian rhythms are common in depressed patients, expressed for example as sleep disturbances. Genetic variations in core circadian genes may in part explain these abnormalities. To investigate whether genetic variation in core circadian genes associates with vulnerability to depression, we genotyped 18 genes in a Swedish population based sample. Genetic variations indicative of association with depression, or with winter depression in our previous study, were tested for association to depression in a second Swedish depression‐control sample set. PER2 genetic variation was associated with depression vulnerability, and this genetic risk did not seem to require exposure to potential sleep disturbance factors such as negative life event or financial strain that are known to increase the risk for depression. Polymorphisms in the circadian genes NPAS2, ARNTL, and RORA were also suggested to contribute to depression vulnerability. The findings we report for PER2, ARNTL, and RORA are supported by at least two of the three sample sets. In conclusion, genetic variation in PER2 is associated with depression vulnerability a Swedish population‐based sample. More studies are needed to determine if this is the case also for NPAS2, ARNTL, and RORA.

Severity of tuberculosis in mice is linked to distal chromosome 3 and proximal chromosome 9

Genetic factors play a role in host response to infection with Mycobacterium tuberculosis, the number one infectious killer worldwide. Mice of the inbred strains I/St and A/Sn show significant differences in disease severity after intravenous injection of a lethal dose of the virulent human isolate M. tuberculosis H37Rv. Following challenge with H37Rv, only I/St mice have rapid body weight loss and short survival times. A genome wide analysis for linkage with body weight after M. tuberculosis H37Rv infection was done in (A/SnxI/St)F1xI/St mice. Among females, quantitative trait loci (QTLs) on chromosomes 9 and 3 were significantly linked to postinfection body weight (logarithm of the odds ratio [LOD] scores of 6.68 and 3.92, respectively). Suggestive linkages were found for QTLs on chromosomes 8 and 17 (LOD scores of 3.01 and 2.95, respectively). For males, QTLs on chromosomes 5 and 10 showed suggestive linkages (LOD scores of 3.03 and 2.31, respectively). These linkages can be used to identify candidate regions for tuberculosis susceptibility loci in the human genome.

Long-term lithium treatment in bipolar disorder is associated with longer leukocyte telomeres

Telomere shortening is a hallmark of aging and has been associated with oxidative stress, inflammation and chronic somatic, as well as psychiatric disorders, including schizophrenia and depression. Additionally, antidepressants have been found to protect against telomere shortening. However, pharmacological telomere studies are lacking in bipolar disorder (BD). Therefore, the objective of this study was to explore telomere length (TL) in patients with BD in the context of lithium treatment. We determined TL by quantitative real-time PCR using peripheral blood leukocytes. Participants were outpatients diagnosed with BD type 1 or 2 (n=256) and healthy controls (n=139). Retrospective case–control and case–case study designs were applied. Lithium response (LiR) was scored using the Alda-Scale. Lithium-treated BD patients overall, as well as those on lithium monotherapy, had 35% longer telomeres compared with controls (P<0.0005, partial η2=0.13). TL correlated positively with lithium treatment duration of >30 months (P=0.031, R2=0.13) and was negatively associated with increasing number of depressive episodes (P<0.007). BD patients responding well to lithium treatment had longer telomeres than those not responding well. This is the first study to report a positive effect of long-term lithium treatment on TL. Importantly, longer TL was also associated with a better LiR in BD patients. These data suggest that lithium exerts a protective effect against telomere shortening especially when therapeutically efficacious. We hypothesize that induction of telomerase activity may be involved in LiR in BD.

Assessment of Response to Lithium Maintenance Treatment in Bipolar Disorder: A Consortium on Lithium Genetics (ConLiGen) Report

Objective The assessment of response to lithium maintenance treatment in bipolar disorder (BD) is complicated by variable length of treatment, unpredictable clinical course, and often inconsistent compliance. Prospective and retrospective methods of assessment of lithium response have been proposed in the literature. In this study we report the key phenotypic measures of the “Retrospective Criteria of Long-Term Treatment Response in Research Subjects with Bipolar Disorder” scale currently used in the Consortium on Lithium Genetics (ConLiGen) study. Materials and Methods Twenty-nine ConLiGen sites took part in a two-stage case-vignette rating procedure to examine inter-rater agreement [Kappa (κ)] and reliability [intra-class correlation coefficient (ICC)] of lithium response. Annotated first-round vignettes and rating guidelines were circulated to expert research clinicians for training purposes between the two stages. Further, we analyzed the distributional properties of the treatment response scores available for 1,308 patients using mixture modeling. Results Substantial and moderate agreement was shown across sites in the first and second sets of vignettes (κ = 0.66 and κ = 0.54, respectively), without significant improvement from training. However, definition of response using the A score as a quantitative trait and selecting cases with B criteria of 4 or less showed an improvement between the two stages (ICC1 = 0.71 and ICC2 = 0.75, respectively). Mixture modeling of score distribution indicated three subpopulations (full responders, partial responders, non responders). Conclusions We identified two definitions of lithium response, one dichotomous and the other continuous, with moderate to substantial inter-rater agreement and reliability. Accurate phenotypic measurement of lithium response is crucial for the ongoing ConLiGen pharmacogenomic study.