Louise K. Sjöholm

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.

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.

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.

Ovarian Cancer Risk Factors by Histologic Subtype: An Analysis From the Ovarian Cancer Cohort Consortium

PURPOSE An understanding of the etiologic heterogeneity of ovarian cancer is important for improving prevention, early detection, and therapeutic approaches. We evaluated 14 hormonal, reproductive, and lifestyle factors by histologic subtype in the Ovarian Cancer Cohort Consortium (OC3). PATIENTS AND METHODS Among 1.3 million women from 21 studies, 5,584 invasive epithelial ovarian cancers were identified (3,378 serous, 606 endometrioid, 331 mucinous, 269 clear cell, 1,000 other). By using competing-risks Cox proportional hazards regression stratified by study and birth year and adjusted for age, parity, and oral contraceptive use, we assessed associations for all invasive cancers by histology. Heterogeneity was evaluated by likelihood ratio test. RESULTS Most risk factors exhibited significant heterogeneity by histology. Higher parity was most strongly associated with endometrioid (relative risk [RR] per birth, 0.78; 95% CI, 0.74 to 0.83) and clear cell (RR, 0.68; 95% CI, 0.61 to 0.76) carcinomas (P value for heterogeneity [P-het] < .001). Similarly, age at menopause, endometriosis, and tubal ligation were only associated with endometrioid and clear cell tumors (P-het ≤ .01). Family history of breast cancer (P-het = .008) had modest heterogeneity. Smoking was associated with an increased risk of mucinous (RR per 20 pack-years, 1.26; 95% CI, 1.08 to 1.46) but a decreased risk of clear cell (RR, 0.72; 95% CI, 0.55 to 0.94) tumors (P-het = .004). Unsupervised clustering by risk factors separated endometrioid, clear cell, and low-grade serous carcinomas from high-grade serous and mucinous carcinomas. CONCLUSION The heterogeneous associations of risk factors with ovarian cancer subtypes emphasize the importance of conducting etiologic studies by ovarian cancer subtypes. Most established risk factors were more strongly associated with nonserous carcinomas, which demonstrate challenges for risk prediction of serous cancers, the most fatal subtype.

CLOCK is suggested to associate with comorbid alcohol use and depressive disorders

Background Depression and alcohol abuse or dependence (AUD) co-occur in the general population more frequently than expected by chance. Alcohol use influences the circadian rhythms generated by the central pacemaker in the suprachiasmatic nucleus, and circadian rhythm alterations in turn are common in depressive disorders as well as among persons addicted to alcohol. Methods 32 SNPs in 19 circadian clockwork related genes were analyzed using DNA from 76 individuals with comorbid depression and AUD, 446 individuals with AUD and 517 healthy controls with no psychiatric diagnosis. The individuals participated in a nationwide health examination study, representative of the general population aged 30 and over in Finland. Results The CLOCK haplotype TTGC formed by SNPs rs3805151, rs2412648, rs11240 and rs2412646, was associated with increased risk for comorbidity (OR = 1.65, 95% CI = 1.14-2.28, P = 0.0077). The SNPs of importance for this suggestive association were rs2412646 and rs11240 indicating location of the functional variation in the block downstream rs2412648. There was no indication for association between CLOCK and AUD. Conclusion Our findings suggest an association between the CLOCK gene and the comorbid condition of alcohol use and depressive disorders. Together with previous reports it indicates that the CLOCK variations we found here may be a vulnerability factor to depression given the exposure to alcohol in individuals having AUD.

CRY2 is associated with rapid cycling in bipolar disorder patients.

Background Bipolar disorder patients often display abnormalities in circadian rhythm, and they are sensitive to irregular diurnal rhythms. CRY2 participates in the core clock that generates circadian rhythms. CRY2 mRNA expression in blood mononuclear cells was recently shown to display a marked diurnal variation and to respond to total sleep deprivation in healthy human volunteers. It was also shown that bipolar patients in a depressive state had lower CRY2 mRNA levels, nonresponsive to total sleep deprivation, compared to healthy controls, and that CRY2 gene variation was associated with winter depression in both Swedish and Finnish cohorts. Principal Findings Four CRY2 SNPs spanning from intron 2 to downstream 3′UTR were analyzed for association to bipolar disorder type 1 (n = 497), bipolar disorder type 2 (n = 60) and bipolar disorder with the feature rapid cycling (n = 155) versus blood donors (n = 1044) in Sweden. Also, the rapid cycling cases were compared with bipolar disorder cases without rapid cycling (n = 422). The haplotype GGAC was underrepresented among rapid cycling cases versus controls and versus bipolar disorder cases without rapid cycling (OR = 0.7, P = 0.006−0.02), whereas overrepresentation among rapid cycling cases was seen for AAAC (OR = 1.3−1.4, P = 0.03−0.04) and AGGA (OR = 1.5, P = 0.05). The risk and protective CRY2 haplotypes and their effect sizes were similar to those recently suggested to be associated with winter depression in Swedes. Conclusions We propose that the circadian gene CRY2 is associated with rapid cycling in bipolar disorder. This is the first time a clock gene is implicated in rapid cycling, and one of few findings showing a molecular discrimination between rapid cycling and other forms of bipolar disorder.

A Role for VAV1 in Experimental Autoimmune Encephalomyelitis and Multiple Sclerosis

VAV1 plays a role in regulating proinflammatory cytokines, which underlie the susceptibility for developing experimental autoimmune encephalomyelitis and multiple sclerosis. Rat Genetics Moving Up Multiple sclerosis (MS) is a common autoimmune disease with a complex etiology that attacks the brain and spinal cord and emerges as a result from both genetic and environmental factors. At present, there is no predictive biomarker for MS and no cure for adults who present with the disease, and only a few genes have been unambiguously linked to its development. The hunt has been to address these challenges, but also to uncover new targets that are associated with a high susceptibility for MS to augment disease-modifying treatments that are in clinical use. Using experimental autoimmune encephalomyelitis, an animal model of MS, Jagodic et al. have focused on a region of the rat genome on chromosome 9 that encodes the gene Vav1. Although this gene was initially identified as an oncogene, it later was found to be an important signal transducer with a pivotal role in immune cells, the very first hint being its specific activation after T cell receptor stimulation. The authors show that a specific mutation identified in rat Vav1 altered Vav1 protein abundances, immune cell activation, and neuroinflammation induction. Taking this observation a step further, among 12,735 individuals of European descent, Jagodic et al. reveal an association between a set of common variants within the first intron of VAV1 and susceptibility for MS. Like what they observed in the rat, common VAV1 variants altered VAV1 expression and immune activation in the peripheral blood and in the cerebrospinal fluid cells of MS patients. This study displays the power of using rat genetics to encourage the discovery of human genetic targets in common diseases such as MS. Multiple sclerosis, the most common cause of progressive neurological disability in young adults, is a chronic inflammatory disease. There is solid evidence for a genetic influence in multiple sclerosis, and deciphering the causative genes could reveal key pathways influencing the disease. A genome region on rat chromosome 9 regulates experimental autoimmune encephalomyelitis, a model for multiple sclerosis. Using interval-specific congenic rat lines and association of single-nucleotide polymorphisms with inflammatory phenotypes, we localized the gene of influence to Vav1, which codes for a signal-transducing protein in leukocytes. Analysis of seven human cohorts (12,735 individuals) demonstrated an association of rs2546133-rs2617822 haplotypes in the first VAV1 intron with multiple sclerosis (CA: odds ratio, 1.18; CG: odds ratio, 0.86; TG: odds ratio, 0.90). The risk CA haplotype also predisposed for higher VAV1 messenger RNA expression. VAV1 expression was increased in individuals with multiple sclerosis and correlated with tumor necrosis factor and interferon-γ expression in peripheral blood and cerebrospinal fluid cells. We conclude that VAV1 plays a central role in controlling central nervous system immune-mediated disease and proinflammatory cytokine production critical for disease pathogenesis.

Increased DNA methylation levels of the insulin-like growth factor binding protein 1 gene are associated with type 2 diabetes in Swedish men

BackgroundProspective studies have shown that low levels of circulating insulin-like growth factor binding protein-1 (IGFBP-1) are associated with the risk of type 2 diabetes. In the present study, we investigated DNA methylation in the IGFBP1 gene to evaluate its changes in relation to serum IGFBP-1 levels in type 2 diabetes.ResultsA total of 406 Swedish men, including age-matched normal glucose tolerance subjects and type 2 diabetes patients either newly diagnosed or undergoing treatment, were selected from the Stockholm Diabetes Prevention Program. IGFBP1 methylation levels in genomic DNA extracted from peripheral blood were analysed by bisulfite pyrosequencing. Serum IGFBP-1 levels were measured by radio-immunoassay. We found that IGFBP1 DNA methylation levels were higher in both newly diagnosed and treated type 2 diabetes patients with a mean diabetes duration of 3 years compared with subjects with normal glucose tolerance (19.8% and 20.2% vs. 16.9%, P < 0.001 for both). Serum levels of IGFBP-1 in newly diagnosed and in treated type 2 diabetes patients were lower compared with healthy individuals (18 μg/l both vs. 24 μg/l, P = 0.011, P < 0.001). IGFBP1 methylation levels but not serum IGFBP-1 levels in type 2 diabetes patients were independent of body mass index. Newly diagnosed patients with a family history of diabetes (FHD) had higher IGFBP1 methylation levels than those without FHD (20.3% vs. 18.6%, P = 0.017).ConclusionsThis study provides the first evidence that changes in DNA methylation of the IGFBP1 gene are associated with type 2 diabetes in Swedish men and suggests that increased IGFBP1 DNA methylation and decreased IGFBP-1 serum levels are features of type 2 diabetes with a short duration.

PreproNPY Pro7 protects against depression despite exposure to environmental risk factors

BACKGROUND There is extensive evidence, from both clinical cases and rodent models, for reduced levels of the widely expressed neuropeptide Y (NPY) in anxiety and depressive disorders. The rare allele of the Leu7Pro polymorphism in the signal peptide of preproNPY has been associated with higher processing into mature NPY, and higher NPY levels in plasma and cerebrospinal fluid. The Pro7 allele was proposed to protect against depression in a small Swedish clinical sample (Heilig M., Zachrisson O., Thorsell A., Ehnvall A., Mottagui-Tabar S., Sjögren M., Asberg M., Ekman R., Wahlestedt C., Agren H., 2004. Decreased cerebrospinal fluid neuropeptide Y (NPY) in patients with treatment refractory unipolar major depression: preliminary evidence for association with preproNPY gene polymorphism. J. Psychiatr. Res. 38, 113-121). METHOD Leu7Pro was analyzed in a large well-characterized longitudinal population-based sample of adult Swedes with data on life situation and life history, including 461 with depression diagnosis, 157 with anxiety diagnosis and 1514 healthy individuals with no symptom of psychopathology. RESULTS Pro7 was rarer in depression cases than in healthy individuals (OR=2.7; P=0.0004). The protective effect of Pro7 was similar despite exposure to known environmental vulnerability factors. Pro7 appeared with similar effect size in those with an anxiety diagnosis, but this was not statistically significant (OR=2.3; P=0.06). LIMITATION The size of the anxiety sample and possibly some recall bias of childhood conditions. CONCLUSION Pro7 allele of preproNPY protected against depression among Swedes. Pro7 is not common, but was found to exert its protective effect also in an environment-induced vulnerable state. This supports a protective effect of NPY in line with previous reports suggesting anxiolytic-like and antidepressant-like effects of NPY.