A genome-wide association study of anorexia nervosa

Anorexia nervosa (AN) is a complex and heritable eating disorder characterized by dangerously low body weight. Neither candidate gene studies nor an initial genome-wide association study (GWAS) have yielded significant and replicated results. We performed a GWAS in 2907 cases with AN from 14 countries (15 sites) and 14 860 ancestrally matched controls as part of the Genetic Consortium for AN (GCAN) and the Wellcome Trust Case Control Consortium 3 (WTCCC3). Individual association analyses were conducted in each stratum and meta-analyzed across all 15 discovery data sets. Seventy-six (72 independent) single nucleotide polymorphisms were taken forward for in silico (two data sets) or de novo (13 data sets) replication genotyping in 2677 independent AN cases and 8629 European ancestry controls along with 458 AN cases and 421 controls from Japan. The final global meta-analysis across discovery and replication data sets comprised 5551 AN cases and 21 080 controls. AN subtype analyses (1606 AN restricting; 1445 AN binge-purge) were performed. No findings reached genome-wide significance. Two intronic variants were suggestively associated: rs9839776 (P=3.01 × 10(-7)) in SOX2OT and rs17030795 (P=5.84 × 10(-6)) in PPP3CA. Two additional signals were specific to Europeans: rs1523921 (P=5.76 × 10(-)(6)) between CUL3 and FAM124B and rs1886797 (P=8.05 × 10(-)(6)) near SPATA13. Comparing discovery with replication results, 76% of the effects were in the same direction, an observation highly unlikely to be due to chance (P=4 × 10(-6)), strongly suggesting that true findings exist but our sample, the largest yet reported, was underpowered for their detection. The accrual of large genotyped AN case-control samples should be an immediate priority for the field.

Depressive disorder moderates the effect of the FTO gene on body mass index

There is evidence that obesity-related disorders are increased among people with depression. Variation in the FTO (fat mass and obesity associated) gene has been shown to contribute to common forms of human obesity. This study aimed to investigate the genetic influence of polymorphisms in FTO in relation to body mass index (BMI) in two independent samples of major depressive disorder (MDD) cases and controls. We analysed 88 polymorphisms in the FTO gene in a clinically ascertained sample of 2442 MDD cases and 809 controls (Radiant Study). In all, 8 of the top 10 single-nucleotide polymorphisms (SNPs) showing the strongest associations with BMI were followed-up in a population-based cohort (PsyCoLaus Study) consisting of 1292 depression cases and 1690 controls. Linear regression analyses of the FTO variants and BMI yielded 10 SNPs significantly associated with increased BMI in the depressive group but not the control group in the Radiant sample. The same pattern was found in the PsyCoLaus sample. We found a significant interaction between genotype and affected status in relation to BMI for seven SNPs in Radiant (P<0.0057), with PsyCoLaus giving supportive evidence for five SNPs (P-values between 0.03 and 0.06), which increased in significance when the data were combined in a meta-analysis. This is the first study investigating FTO and BMI within the context of MDD, and the results indicate that having a history of depression moderates the effect of FTO on BMI. This finding suggests that FTO is involved in the mechanism underlying the association between mood disorders and obesity.

The impact of COMT gene polymorphisms on suicidality in treatment resistant major depressive disorder--a European multicenter study

Many association studies have reported associations between the catechol-O-methyltransferase (COMT) gene and psychiatric disorders including major depression (MDD). The COMT gene has further been associated with suicidal behaviour, as well as with treatment response, although with conflicting results. In the present study, we further elucidate the impact of COMT in treatment response in MDD patients with suicide risk and/or a personal history of suicide attempts. Two hundred fifty MDD patients were collected in the context of a European multicentre resistant depression study and treated with antidepressants at adequate doses for at least 4 weeks. Suicidality was assessed using Mini International Neuropsychiatric Interview (MINI) and the Hamilton Rating Scale for Depression (HAM-D). Treatment response was defined as HAM-D ≤ 17 and remission as HAM-D ≤ 7 after 4 weeks of treatment with antidepressants at adequate dose. Genotyping was performed for seven SNPs (rs4680, rs2075507, rs737865, rs6269, rs4633, rs4818 and rs165599) within the COMT gene. With regard to suicide risk and personal history of suicide attempts, neither single marker nor haplotypic association was found with any SNP after multiple testing correction. In non-responders, we found significant single marker and haplotypic association with suicide risk, but not in responders. The same holds true for both remitters and non-remitters, and when testing for association with a personal history of suicide attempts and treatment response phenotypes. In conclusion, we found significant association of COMT SNPs with suicide risk in MDD patients not responding to antidepressant treatment. Larger well-defined cohorts will be required to dissect this further.

A follow-up case-control association study of tractable (druggable) genes in recurrent major depression

The High-Throughput Disease-specific target Identification Program (HiTDIP) aimed to study case-control association samples for 18 common diseases. Here we present the results of a follow-up case-control association study of HiTDIP in major depressive disorder (MDD). The HiTDIP in MDD was conducted in a sample of 974 cases of recurrent MDD of white German origin collected at the Max-Planck Institute (MP-GSK) and 968 ethnically matched controls screened for lifetime absence of depression. Six genes were identified as of interest for a follow-up, based on the strength of the association and based on the interest as potential candidate target for developing new treatment for depression: Solute Carrier Family 4 Member 10 (SLC4A10), Dipeptidyl Peptidase IV (DPP4), Dopamine Receptor D3 (DRD3), Zinc Finger Protein 80 (ZNF80), Nitric Oxide Synthase 2A (NOS2A) and Peroxisome Proliferator-Activated Receptor-Gamma, Coactivator 1, Alpha (PPARGC1A). Within the current study, we attempted to follow-up these findings in a sample from the UK, the Depression Case Control (DeCC) sample consisting of 1,196 cases and 842 screened controls, phenotyped using exactly the same methods as the MP-GSK sample. Performing Cochran-Mantel-Haenzel statistics to test for genotypic and/or allelic differences between the DeCC and MP-GSK samples, we found no significant differences, thus being able to combine the two samples for association testing. In the combined sample of 2,170 MDD cases and 1,810 controls, there were positive findings in the Nitric Oxide Synthase 2A (NOS2A) gene both using single SNP analysis and haplotype analysis.

FC04-06 - Candidate gene association study of suicidality in treatment resistant MDD

Suicidal behaviour runs in families and the existence of genetic vulnerability to suicidality is well-established. Mental disorders, especially depression, are present in more of 90% of suicides. The incidence of treatment emergent suicidal ideation in major depression (MDD) varies from 4% to 20%, depending on the definition of suicidal ideation and sample characteristics.

In the present study, we further elucidated the impact of depression candidate genes in treatment emergent suicidal ideation in MDD. One hundred-seventy MDD patients were collected in the context of a resistant depression study and treated with antidepressants at adequate doses for at least 4 weeks. MDD subjects were genotyped for SNPs within the COMT gene, BDNF, DTNBP1, 5HT1A, 5HT2A, GNB3, GRIK4, PTGS1, PTGS2, CREB, and cytochrome P450 CYP1A2, CYP2C9, CYP2C19 and CYP2D6 gene. Response, remission and treatment resistance, as well as suicidality information derived from Mini International Neuropsychiatric Interview (MINI) and Hamilton Rating Scale for Depression (HAM-D) were recorded.

A quantitative and measure of suicidal behaviour was defined using the Hamilton rating scale (score 0 to 4) and the MINI-item (yes/no) on suicidality in a large cohort of depression cases. In addition, we tested for association with ‘serious suicidal attempts’ corresponding to a HAMD score of 4 (discrete trait analyses). Results of this candidate gene approach in treatment emergent suicidal ideation in MDD will be presented and discussed.

P01-246-3Q29 case-control association study of co-morbid migraine in bipolar affective disorder

According to Oedegaard et al. (2010) the co-morbidity of migraine and bipolar disorder (BPD) is well documented in numerous epidemiological and clinical studies, and there are clear pathophysiological similarities. Interestingly, in a genome-wide scan, Lea et al. (2005) identified a susceptibility locus for a severe heritable form of common migraine on chromosome 3q29. With respect to BPD, a susceptibility region on chromosome 3q29 was identified in a genome-wide linkage scan (Bailer et al. 2002) and follow-up linkage analysis (Schosser et al. 2004). These findings were also supported by further fine-mapping of this region (Schosser et al. 2007). Since 3q29 is among the chromosomal regions implicated in migraine and bipolar linkage studies, the aim of the current study is to test for 3q29 association of migraine in sample of patients with BPD. The sample consists of 463 patients with a diagnosis of BPD (34.63% men, 65.37% women; mean age ± SD: 48.01 ± 11.26), as defined by the Diagnostic and Statistical Manual 4th edition operational criteria (DSM-IV) and the International Classification of Diseases 10th edition operational criteria (ICD-10), derived from the Bipolar Affective Disorder Case Control Study (BACCS). A total of 51 SNPs in the region of the 3q29 were genotyped using Sequenom MassARRAY® iPLEX Gold and tested for association with migraine. The results of this association study investigating the 3q29 region in a sample of patients with BPD will be presented.

COMT in major depression - UK candidate gene association study

Catechol-O-methyltransferase (COMT) has a central role in brain dopamine, noradrenalin and adrenalin signaling, and has been suggested to be involved in the pathogenesis and pharmacological treatment of affective disorders. The functional single nucleotide polymorphism (SNP) in exon 4 (Val158Met, rs4680) influences the COMT enzyme activity. The Val158Met polymorphism is a commonly studied variant in psychiatric genetics, and initial studies in schizophrenia and bipolar disorder presented evidence for association with the Met allele. In unipolar depression, while some of the investigations point at an association between the Met/Met genotype and others have found a link between the Val/Val genotype and depression, most of the studies cannot detect any difference in Val158Met allele frequency between depressed individuals and controls.

In the present study, we further elucidated the impact of COMT polymorphisms including the Val158Met in MDD. We investigated 1,250 subjects with DSM-IV and/or ICD-10 diagnosis of major depression (MDD), and 1,589 control subjects from UK. A total of 24 SNPs spanning the COMT gene were successfully genotyped using the Illumina HumaHap610-Quad Beadchip (22 SNPs), SNPlex™ genotyping system (1 SNP), and Sequenom MassARRAY® iPLEX Gold (1 SNP). Statistical analyses were implemented using PASW Statistics18, FINETTI (http://ihg.gsf.de/cgi-bin/hw/hwa1.pl), UNPHASED version 3.0.10 program and Haploview 4.0 program.

Neither single-marker nor haplotypic association was found with the functional Val158Met polymorphism or with any of the other SNPs genotyped. Our findings do not provide evidence that COMT plays a role in MDD or that this gene explains part of the genetic overlap with bipolar disorder.

NRG1 gene in recurrent major depression: no association in a large-scale case-control association study

The Neuregulin 1 (NRG1) gene was initially implicated in schizophrenia (SZ) and has recently been associated with bipolar disorder (BPD) in two studies. An association with major depressive disorder (MDD) has not yet been investigated but is warranted in view of the genetic overlap between MDD and BPD. We have performed a large-scale case-control study investigating the association between NRG1 polymorphisms and MDD, genotyping a selection of 14 single nucleotide polymorphisms (SNPs) spanning the NRG1 gene in a sample of 1,398 patients of White European ancestry with a diagnosis of MDD and 1,304 ethnically matched controls from three clinical sites in the UK. We found no single marker or haplotype associations that withstood correction for multiple testing. Our findings do not provide evidence that NRG1 plays a role in MDD or that this gene explains part of the genetic overlap with BPD.

From age correction to genome-wide association

OBJECTIVE

Eric Strömgren was one of the pioneers of psychiatric genetics and family studies. There has now been an explosion of interest in this field and research progress, including linkage and association studies, whole genome genotyping, copy number variants and epigenetics is reviewed here.

METHOD

An overview of this area of psychiatric research is presented and discussed based on the relevant literature aiming at giving a recent status of the progress.

RESULTS

Broadly speaking linkage and association are complementary approaches used to locate genes contributing to the genetic aetiology of psychopathology. Linkage can be detected over comparatively large distances, however power is problematic when searching for quantitative trait loci with small effect sizes. In contrast, association studies can detect small effects but only over very small distances. Therefore, while several genome-wide linkage studies in psychiatric disorders have been performed, the majority of association studies have investigated specific functional candidate genes.

CONCLUSION

Due to very recent technological advancements, genome-wide association studies have now become possible and have identified some completely novel susceptibility loci. Other recent advances include the discovery of epigenetic phenomena and copy number variants.