Recurrent Early-onset Major Depressive Disorder Research Articles

Differential hippocampal gene expression and pathway analysis in an etiology-based mouse model of major depressive disorder.

We have recently reported the creation and initial characterization of an etiology-based recombinant mouse model of a severe and inherited form of Major Depressive Disorder (MDD). This was achieved by replacing the corresponding mouse DNA sequence with a 6-base DNA sequence from the human CREB1 promoter that is associated with MDD in individuals from families with recurrent, early-onset MDD (RE-MDD). In the current study, we explored the effect of the pathogenic Creb1 allele on gene expression in the mouse hippocampus, a brain region that is altered in structure and function in MDD. Mouse whole-genome profiling was performed using the Illumina MouseWG-6 v2.0 Expression BeadChip microarray. Univariate analysis identified 269 differentially-expressed genes in the hippocampus of the mutant mouse. Pathway analyses highlighted 11 KEGG pathways: the phosphatidylinositol signaling system, which has been widely implicated in MDD, Bipolar Disorder, and the action of mood stabilizers; gap junction and long-term potentiation, which mediate cognition and memory functions often impaired in MDD; cardiac muscle contraction, insulin signaling pathway, and three neurodegenerative brain disorders (Alzheimer's, Parkinson's, and Huntington's Diseases) that are associated with MDD; ribosome and proteasome pathways affecting protein synthesis/degradation; and the oxidative phosphorylation pathway that is key to energy production. These findings illustrate the merit of this congenic C57BL/6 recombinant mouse as a model of RE-MDD, and demonstrate its potential for highlighting molecular and cellular pathways that contribute to the biology of MDD. The results also inform our understanding of the mechanisms that underlie the comorbidity of MDD with other disorders.

Alterations of brain anatomy in mouse model of MDD created by replacement of homologous mouse DNA sequence with an illness‐associated 6‐base humanCREB1promoter sequence

We have recently reported the creation and initial characterization of an etiology-based recombinant mouse model of a severe and inherited form of Major Depressive Disorder (MDD). This was achieved by replacing the corresponding mouse DNA sequence with a 6-base DNA sequence from the human CREB1 promoter that is associated with the development of MDD in men and women from families identified by probands with recurrent, early-onset MDD (RE-MDD). Individuals in these families are also at increased risk for childhood developmental disorders and late life neurodegenerative disorders. The current study used three-dimensional magnetic resonance microscopy (3D-MRM) to determine the effect of the resulting humanized mutation of the mouse Creb1 gene on the anatomy of the mouse brain. Homozygous mutant mice manifested prominent increases in the volume and surface area of the lateral ventricles, as well as reduced volume of the anterior corpus callosum, compared to age/sex-matched wild-type mice. No significant genotype effects were observed on the volume or surface area of total brain, or several brain regions sometimes observed to be abnormal in human depression, including hippocampus, amygdala, or striatum. These findings suggest that at least some forms of MDD result from abnormal brain development produced by inherited genetic variants.

POSTTRAUMATIC STRESS DISORDER INCREASES RISK FOR SUICIDE ATTEMPT IN ADULTS WITH RECURRENT MAJOR DEPRESSION

Genetics of Recurrent Early-Onset Depression study (GenRED II) data were used to examine the relationship between posttraumatic stress disorder (PTSD) and attempted suicide in a population of 1,433 individuals with recurrent early-onset major depressive disorder (MDD). We tested the hypothesis that PTSD resulting from assaultive trauma increases risk for attempted suicide among individuals with recurrent MDD. Data on lifetime trauma exposures and clinical symptoms were collected using the Diagnostic Interview for Genetic Studies version 3.0 and best estimate diagnoses of MDD, PTSD, and other DSM-IV Axis I disorders were reported with best estimated age of onset. The lifetime prevalence of suicide attempt in this sample was 28%. Lifetime PTSD was diagnosed in 205 (14.3%) participants. We used discrete time-survival analyses to take into account timing in the PTSD-suicide attempt relationship while adjusting for demographic variables (gender, race, age, and education level) and comorbid diagnoses prior to trauma exposure. PTSD was an independent predictor of subsequent suicide attempt (HR = 2.5, 95% CI: 1.6, 3.8; P < .0001). Neither assaultive nor nonassaultive trauma without PTSD significantly predicted subsequent suicide attempt after Bonferroni correction. The association between PTSD and subsequent suicide attempt was driven by traumatic events involving assaultive violence (HR = 1.7, 95% CI: 1.3, 2.2; P< .0001). Among those with recurrent MDD, PTSD appears to be a vulnerability marker of maladaptive responses to traumatic events and an independent risk factor for attempted suicide. Additional studies examining differences between those with and without PTSD on biological measures might shed light on this potential vulnerability.

A mega-analysis of genome-wide association studies for major depressive disorder

Prior genome-wide association studies (GWAS) of major depressive disorder (MDD) have met with limited success. We sought to increase statistical power to detect disease loci by conducting a GWAS mega-analysis for MDD. In the MDD discovery phase, we analyzed more than 1.2 million autosomal and X chromosome single-nucleotide polymorphisms (SNPs) in 18 759 independent and unrelated subjects of recent European ancestry (9240 MDD cases and 9519 controls). In the MDD replication phase, we evaluated 554 SNPs in independent samples (6783 MDD cases and 50 695 controls). We also conducted a cross-disorder meta-analysis using 819 autosomal SNPs with P<0.0001 for either MDD or the Psychiatric GWAS Consortium bipolar disorder (BIP) mega-analysis (9238 MDD cases/8039 controls and 6998 BIP cases/7775 controls). No SNPs achieved genome-wide significance in the MDD discovery phase, the MDD replication phase or in pre-planned secondary analyses (by sex, recurrent MDD, recurrent early-onset MDD, age of onset, pre-pubertal onset MDD or typical-like MDD from a latent class analyses of the MDD criteria). In the MDD-bipolar cross-disorder analysis, 15 SNPs exceeded genome-wide significance (P<5 × 10(-8)), and all were in a 248 kb interval of high LD on 3p21.1 (chr3:52 425 083-53 822 102, minimum P=5.9 × 10(-9) at rs2535629). Although this is the largest genome-wide analysis of MDD yet conducted, its high prevalence means that the sample is still underpowered to detect genetic effects typical for complex traits. Therefore, we were unable to identify robust and replicable findings. We discuss what this means for genetic research for MDD. The 3p21.1 MDD-BIP finding should be interpreted with caution as the most significant SNP did not replicate in MDD samples, and genotyping in independent samples will be needed to resolve its status.

Replacement of homologous mouse DNA sequence with pathogenic 6-base human CREB1 promoter sequence creates murine model of major depressive disorder.

Major depressive disorder (MDD) is a leading cause of disability worldwide. Families with recurrent, early-onset MDD (RE-MDD), a severe, familial form of MDD, have provided an important resource for identifying and characterizing genetic variants that confer susceptibility to MDD and related disorders. Previous studies identified a rare, highly penetrant A(-115)G transition within the human CREB1 promoter that reduced promoter activity in vitro and was associated with depressive disorders in RE-MDD families. The development of an etiology-based recombinant animal model for MDD would facilitate the advancement of our limited understanding of the pathophysiology of MDD, as well as the development of improved treatments. Here we report the construction and initial characterization of a congenic mutant C57BL/6NTac mouse model that carries the human pathogenic sequence at the homologous position of the mouse Creb1 promoter. The recombinant strain exhibited decreases in reproductive capacity and pup survival that may be related to increased infant mortality observed in RE-MDD families; enlargement of the cerebral ventricles; reduced levels of CREB protein in the mouse cerebral cortex, as predicted from transfection experiments employing the pathogenic human CREB1 promoter; and alterations in two standardized behavioral tests, the forced swim and marble burying tests. These initial findings support the pathogenicity of the human A(-115)G promoter variant, and invite further characterization of this etiology-based recombinant animal model for MDD. Human promoter variants that have highly penetrant effects on disease expression provide an attractive opportunity for creating etiology-based mouse models of human diseases, with minimal disruption of the mouse genome.

Effects of the A(−115)G variant on CREB1 promoter activity in two brain cell lines: Interactions with gonadal steroids

Major depressive disorder (MDD) is a leading contributor to disease burden worldwide. Previous genetic studies have revealed significant evidence of linkage of the CREB1 region to mood disorders among women from families with recurrent, early-onset MDD (RE-MDD), a severe and familial subtype of MDD. Systematic resequencing of the CREB1 gene in affected members of these families has identified rare sequence variants at positions -656 and -115 that appear to cosegregate with unipolar mood disorders in two large multigenerational families and three small nuclear families, respectively. Results from previous transfection experiments that employed constructs containing the wild-type or variant CREB1 promoters coupled to a reporter gene support the hypothesis that the A(-656) allele contributes to the development of MDD in women by selectively increasing the activity of the CREB1 promoter in brain cell lines exposed to 17 β-estradiol. Analogous transfection experiments described in the current study revealed that the G(-115) promoter variant reduced promoter activity in CATH.a neuronal cells regardless of the hormonal environment, consistent with the observation that increased risk for unipolar mood disorders conferred by this allele was not limited by sex. The effects of CREB1 promoter variants on promoter activity, their influence on the development of mood disorders and related clinical features, and the interaction of their phenotypic expression with sex seem likely to be complex and allele-specific rather than a general property of the CREB1 locus. © 2010 Wiley-Liss, Inc.

Genome-wide association study of recurrent early-onset major depressive disorder

A genome-wide association study was carried out in 1,020 case subjects with recurrent early-onset major depressive disorder (MDD) (onset before age 31) and 1,636 control subjects screened to exclude lifetime MDD. Subjects were genotyped with the Affymetrix 6.0 platform. After extensive quality control procedures, 671,424 autosomal SNPs and 25,068 X chromosome SNPs with minor allele frequency greater than 1% were available for analysis. An additional 1,892,186 HapMap II SNPs were analyzed based on imputed genotypic data. Single-SNP logistic regression trend tests were computed, with correction for ancestry-informative principal component scores. No genome-wide significant evidence for association was observed, assuming that nominal P < 5 × 10−8 approximates a 5% genome-wide significance threshold. The strongest evidence for association was observed on chromosome 18q22.1 (rs17077540, P = 1.83 × 10−7) in a region that has produced some evidence for linkage to bipolar I or II disorder in several studies, within an mRNA detected in human brain tissue (BC053410)and approximately 75 kb upstream of DSEL. Comparing these results with those of a meta-analysis of three MDD GWAS datasets reported in a companion article, we note that among the strongest signals observed in the GenRED sample, the meta-analysis provided the greatest support (although not at a genome-wide significant level) for association of MDD to SNPs within SP4, a brain-specific transcription factor. Larger samples will be required to confirm the hypothesis of association between MDD (and particularly the recurrent early-onset subtype) and common SNPs.

Genetic linkage of region containing the CREB1 gene to depressive disorders in families with recurrent, early‐onset, major depression: A re‐analysis and confirmation of sex‐specific effect

A previously published model-free linkage analysis of chromosome 2q33-35, highlighted by previous case-control studies and supported by within-family analyses employing the transmission disequilibrium test, revealed evidence of sex-specific linkage of the CREB1-containing region of 2q to unipolar mood disorders among women in 81 recurrent, early-onset, major depressive disorder (RE-MDD) families. Since it has been reported that the LODPAL program from S.A.G.E. v.4.0 used to conduct this previous linkage analysis suffers from an increased type I error rate that is exacerbated by covariates such as sex, we re-analyzed the evidence for this sex-specific linkage result using a simulation approach to estimate the empirical significance of our previous results. The results continue to support sex-specific linkage of the CREB1 region to mood disorders among women from families with RE-MDD. Moreover, these results have been supported by a host of additional published findings that implicate sequence variations in CREB1 in the sex-dependent development of syndromic mood disorders, as well as related clinical features and disorders.

Linkage Disequilibrium Mapping of a Chromosome 15q25-26 Major Depression Linkage Region and Sequencing of NTRK3

We reported genome-wide significant linkage on chromosome 15q25.3-26.2 to recurrent early-onset major depressive disorder (MDD-RE). Here we present initial linkage-disequilibrium (LD) fine mapping of this signal and sequence analysis of NTRK3 (neurotrophic receptor kinase-3), a biologically plausible candidate gene. In 300 pedigrees informative for family-based association, 1195 individuals were genotyped for 795 single nucleotide polymorphism (SNPs). We resequenced 21 exons and 7 highly conserved NTRK3 regions in 176 MDD-RE cases to test for an excess of rare functional variants and, 176 controls for case-control analysis of common variants. LD mapping showed nominally significant association in NTRK3, FLJ12484, RHCG, DKFZp547K1113, VPS33B, SV2B, SLCO3A1, RGMA, and MCTP2 with MDD-RE. In NTRK3, five SNPs had nominally significant p values (.035-.001). Sequence analysis revealed 35 variants (24 novel, including 9 rare exonic); the number of rare variants did not exceed chance expectation. Case-control analysis of 13 common variants showed modest nominal association of MDD-RE with rs4887379, rs6496463, and rs3825882 (p = .008, .048, and .034), which were in partial LD with four of five associated SNPs from the family-based experiment. Common variants in NTRK3 or other genes identified might play a role in MDD-RE. However, much larger studies are required for full evaluation of this region.

Effects of the G(−656)A variant on CREB1 promoter activity in a neuronal cell line: Interactions with gonadal steroids and stress

Major depressive disorder (MDD) constitutes a major public health problem worldwide and affects women twice as frequently as men. Previous genetic studies have revealed significant evidence of linkage of the cAMP-responsive element-binding protein 1 (CREB1) gene region (2q33-35) to mood disorders among women from families with recurrent, early-onset MDD (RE-MDD), a severe and familial subtype of MDD. A rare G-to-A transition at position -656 in the CREB1 promoter co-segregates with mood disorders in women from these families, implicating CREB1 as a sex-related susceptibility gene for unipolar mood disorders. In the current study, the functional significance of the CREB1 promoter variant was determined using transfection experiments that employed plasmid constructs containing the wild-type or variant CREB1 promoters coupled to a reporter gene. The results support the hypothesis that the A(-656) allele contributes to the development of MDD in women through selective alteration of CREB1 promoter activity by female gonadal steroids in noradrenergic neuronal cells. Furthermore, exaggeration of these effects during a simulated stress condition may be relevant to reported gene-environment interactions that contribute to the emergence of MDD in clinical populations.

Effects of the G(‐656)A variant on CREB1 promoter activity in a glial cell line: Interactions with gonadal steroids and stress

Major depressive disorder (MDD) constitutes a major public health problem worldwide and affects women twice as frequently as men. Previous genetic studies have revealed significant evidence of linkage of the CREB1 region to mood disorders among women from families with recurrent, early-onset MDD (RE-MDD), a severe and familial subtype of MDD. A rare G to A transition at position -656 in the CREB1 promoter cosegregates with mood disorders in women from these families, implicating CREB1 as a sex-related susceptibility gene for unipolar mood disorders. In the current study, the functional significance of the CREB1 promoter variant was determined using transfection experiments that employed constructs containing the wild-type or variant CREB1 promoters coupled to a reporter gene. The results support the hypothesis that the A(-656) allele contributes to the development of MDD in women by selectively altering the activity of the CREB1 promoter in glial cells exposed to 17 beta-estradiol. Furthermore, the exaggeration of this effect during a simulated stress condition may be relevant to reported gene-environment interactions that contribute to the emergence of MDD in clinical populations. The results of in silico analysis revealed four putative binding sites for transcription factors that are affected by the G to A transition at position -656, of which CP2 best fit the experimental observations.

Genetics of Recurrent Early-Onset Major Depression (GenRED): Significant Linkage on Chromosome 15q25-q26 After Fine Mapping With Single Nucleotide Polymorphism Markers

The authors studied a dense map of single nucleotide polymorphism (SNP) DNA markers on chromosome 15q25-q26 to maximize the informativeness of genetic linkage analyses in a region where they previously reported suggestive evidence for linkage of recurrent early-onset major depressive disorder. In 631 European-ancestry families with multiple cases of recurrent early-onset major depressive disorder, 88 SNPs were genotyped, and multipoint allele-sharing linkage analyses were carried out. Marker-marker linkage disequilibrium was minimized, and a simulation study with founder haplotypes from these families suggested that linkage scores were not inflated by linkage disequilibrium. The dense SNP map increased the information content of the analysis from around 0.7 to over 0.9. The maximum evidence for linkage was the Z likelihood ratio score statistic of Kong and Cox (Z(LR))=4.69 at 109.8 cM. The exact p value was below the genomewide significance threshold. By contrast, in the genome scan with microsatellite markers at 9 cM spacing, the maximum Z(LR) for European-ancestry families was 3.43 (106.53 cM). It was estimated that the linked locus or loci in this region might account for a 20% or less populationwide increase in risk to siblings of cases. This region has produced modestly positive evidence for linkage to depression and related traits in other studies. These results suggest that DNA sequence variations in one or more genes in the 15q25-q26 region can increase susceptibility to major depression and that efforts are warranted to identify these genes.

Genetics of Recurrent Early-Onset Major Depression (GenRED): Final Genome Scan Report

Objective: The authors carried out a genomewide linkage scan to identify chromosomal regions likely to contain genes that contribute to susceptibility to recurrent early-onset major depressive disorder, the form of the disorder with the greatest reported risk to relatives of index cases. Method: Microsatellite DNA markers were studied in 656 families with two or more such cases (onset before age 31 in probands and age 41 in other relatives), including 1,494 informative “all possible” affected relative pairs (there were 894 independent affected sibling pairs). Analyses included a primary multipoint allele-sharing analysis (with ALLEGRO) and a secondary logistic regression analysis taking the sex of each relative pair into account (male-male, male-female, female-female). Results: Genomewide suggestive evidence for linkage was observed on chromosome 15q25-q26 (at 105.4 centimorgans [cM]). The authors previously reported genomewide significant linkage in this region in the first 297 families. In the secondary analysis, after empirical genomewide correction for multiple testing, suggestive linkage results were observed on chromosome 17p12 (28.0 cM, excess sharing in male-male and male-female pairs) and on chromosome 8p22-p21.3 (25.1 cM, excess sharing in male-male pairs). Conclusions: These regions of chromosomes 15q, 17p, and 8p might contain genes that contribute to susceptibility to major depression and related disorders. Evidence for linkage has been reported independently in the same regions of chromosome 15q for major depression and of chromosome 8p for related personality traits.

Genetics of Recurrent Early-Onset Major Depression (GenRED): Final Genome Scan Report

The authors carried out a genomewide linkage scan to identify chromosomal regions likely to contain genes that contribute to susceptibility to recurrent early-onset major depressive disorder, the form of the disorder with the greatest reported risk to relatives of index cases. Microsatellite DNA markers were studied in 656 families with two or more such cases (onset before age 31 in probands and age 41 in other relatives), including 1,494 informative "all possible" affected relative pairs (there were 894 independent affected sibling pairs). Analyses included a primary multipoint allele-sharing analysis (with ALLEGRO) and a secondary logistic regression analysis taking the sex of each relative pair into account (male-male, male-female, female-female). Genomewide suggestive evidence for linkage was observed on chromosome 15q25-q26 (at 105.4 centimorgans [cM]). The authors previously reported genomewide significant linkage in this region in the first 297 families. In the secondary analysis, after empirical genomewide correction for multiple testing, suggestive linkage results were observed on chromosome 17p12 (28.0 cM, excess sharing in male-male and male-female pairs) and on chromosome 8p22-p21.3 (25.1 cM, excess sharing in male-male pairs). These regions of chromosomes 15q, 17p, and 8p might contain genes that contribute to susceptibility to major depression and related disorders. Evidence for linkage has been reported independently in the same regions of chromosome 15q for major depression and of chromosome 8p for related personality traits.

Association of the human kainate receptor GluR7 gene (GRIK3) with recurrent major depressive disorder

The etiology of mood disorders remains elusive, despite our increasing understanding of the neurotransmitter systems and brain regions that are involved. We performed a large family-based association study to test if the human kainate receptor GluR7 gene (GRIK3) is associated with bipolar disorder (BP) or recurrent major depressive disorder (R-MDD). One hundred fifty-three multiplex BP families from the National Institute of Mental Health (NIMH) Genetics Initiative on Bipolar Disorder were analyzed with the transmission disequilibrium test (TDT). We detected a significant linkage disequilibrium (LD) indicated by preferential maternal transmission of the GluR7 S310 allele to R-MDD patients (P = 0.012), but not to bipolar I disorder (BPI) patients (P = 1.00). We performed a second independent study by applying the TDT in 81 parent-offspring triads from families that inherit recurrent early-onset major depressive disorder (RE-MDD). The results from this second study showed only a suggestive maternal association (P = 0.068). Our findings imply that the GluR7 gene is a susceptibility factor in R-MDD and that the glutamatergic receptor system plays a critical role in the disease etiology.

High harm avoidance and low self-directedness in euthymic young adults with recurrent, early-onset depression

Background The personality dimensions of harm avoidance (HA) and self-directedness (SD), as measured by the Temperament and Character Inventory (TCI), have been widely associated with depression and there is preliminary evidence that they may represent trait markers for depression. However, many studies in this area are limited by the use of heterogeneous samples of depressed patients and by the confounding effect of depressed mood during personality testing. The current study compares TCI personality dimension scores in a group of euthymic young adults with recurrent early-onset major depressive disorder (RE-MDD) to well-matched euthymic controls. Methods Fifty-two young adults with a past history of RE-MDD were recruited from consecutive referrals to a psychiatric clinic at a university health service. Eighty nine controls were also recruited. Euthymia was established in patients by a score of less than 9 on the Hamilton Rating Scale for Depression (HRSD) and in controls by a Becks Depression Inventory (BDI) score of less than 10. All participants completed the TCI-125. Results Patients and controls were well matched in terms of sociodemographic profile. Euthymic RE-MDD patients scored significantly higher than controls on the temperament dimension of harm avoidance (HA; mean score 14.5 versus 7.8, p < 0.0001) and significantly lower than controls on the character dimension of self-directedness (SD; mean score 14.1 versus 19.9, p < 0.0001). Covariance analysis suggested that both HA and SD contributed independently to the familial risk of depression. Limitations Subjects and controls all came from relatively affluent social backgrounds—these findings may not generalise to more socioeconomically diverse populations. The possibility of a ‘scarring effect’ of depressive episodes on self-reported personality dimension scores cannot be excluded. Conclusions High HA and low SD represent trait markers for liability to recurrent major depressive disorder in young adults. Further research is needed to replicate these findings and to assess the contribution that the experience of depressive episodes makes to self-reported personality dimension scores.

Genome-wide linkage survey for genetic loci that affect the risk of suicide attempts in families with recurrent, early-onset, major depression.

We previously described the results of a genome-wide linkage survey for genetic loci that influenced the development of unipolar mood disorders in 81 families identified by individuals with Recurrent, Early-Onset, Major Depressive Disorder (RE-MDD) [Zubenko et al. 2003b; Am J Med Genet (Neuropsychiatr Genet) 123B:1-18]. In the current study, we extended this linkage analysis by including the history of a suicide attempt as a covariate to identify chromosomal regions that harbor genes that influence the risk of this behavior in the context of mood disorders. This approach identified six linkage peaks with maximum multipoint DeltaLOD scores that reached genome-wide adjusted levels of significance (2p, 5q, 6q, 8p, 11q, and Xq). Four of these (2p, 6q, 8p, and Xq) exceeded the criterion for "highly-significant linkage" (genome-wide adjusted P < 0.001) recommended by Lander and Kruglyak [1995; Nat Genet 11:241-246]. The strongest evidence for linkage was observed in analyses employing affected relative pairs (ARPs) with the most severe and disabling Mood Disorders: Depression Spectrum Disorder and RE-MDD. The highest DeltaLOD score that emerged from this linkage analysis, 5.08, occurred for ARPs with Depression Spectrum Disorder at D8S1145 (37.0 cM, 18.2 Mbps, P < 0.0001) at cytogenetic location 8p22-p21. Significant linkage results on Xq arose from analyses of ARPs with RE-MDD at DXS1047 (143 cM, 127.8 Mbps, DeltaLOD = 3.87, P < 0.0001), a finding that may contribute to the higher rate of suicide attempts among women than men. These findings provide evidence for suicide risk loci that are independent of susceptibility loci for Mood Disorders, and suggest that the capacity for suicide risk loci to affect the development of suicidal behavior depends on the psychiatric disorder or subtype with which they interact.

Genome-wide linkage survey for genetic loci that influence the development of depressive disorders in families with recurrent, early-onset, major depression.

In this report, we describe the results of the first genome-wide linkage survey for genetic loci that influence the development of unipolar Mood Disorders in 81 families identified by individuals with Recurrent, Early-Onset, Major Depressive Disorder (RE-MDD). Model-free linkage analysis was performed using genotypes for 392 highly informative polymorphisms with an average spacing of 9 cM. The highest maximum LOD score observed, 8.19 (genome-wide adjusted P << 0.0001), occurred for Recurrent Major Depressive Disorder (R-MDD) at D2S2321 (205 cM), located 121 kb proximal to CREB1. Nineteen chromosomal regions contained linkage peaks that reached genome-wide statistical significance (genome-wide adjusted P < 0.05) and ten of these were "highly significant" (adjusted P < 0.001). Six of the 19 linkage peaks were revealed only when the analysis included covariates to control for the effects of sex and linkage to CREB1. Sex-specific susceptibility loci were common and preferentially affected the vulnerability of women to developing unipolar Mood Disorders. Five loci revealed evidence of interaction with the CREB1 locus in determining susceptibility (epistasis). A systematic candidate gene analysis is presented and potential overlaps of the linkage regions for unipolar Mood Disorders with those reported for other psychiatric disorders are discussed. The findings suggest that genes whose products participate in cellular signaling pathways that converge on CREB, as well as the target genes whose expression they regulate, may also harbor alleles that affect the development of Mood Disorders and related conditions.

Sequence variations in CREB1 cosegregate with depressive disorders in women.

Major depressive disorder (MDD) constitutes a major public health problem worldwide and affects women twice as frequently as men. Previous linkage studies have identified a 451 kb region of 2q33-35 that exhibited significant evidence of linkage to Mood Disorders among women (but not men) from families with recurrent, early-onset MDD (RE-MDD), a severe and strongly familial subtype of MDD. This 451 kb region includes CREB1, an attractive susceptibility gene for MDD and related disorders. Sequence variations in the CREB1 promoter and intron 8 have been detected that cosegregate with Mood Disorders, or their absence, in women from these families, identifying CREB1 as a sex-limited susceptibility gene for unipolar Mood Disorders. These findings implicate the cAMP signaling pathway in the pathophysiology of Mood Disorders and related conditions.

The association of the D2S2944 124 bp allele with recurrent early onset major depressive disorder in women.

Major depressive disorder (MDD) and substance use disorders (SUD) are complex behavioral disorders with 40-50% heritability. Recently, Zubenko and colleagues reported that the 124 bp allele of D2S2944, a tetranucleotide repeat marker on 2q35, is strongly associated with recurrent, early onset MDD (RE-MDD) and alcohol use disorders in women. To test this hypothesis, we examined the association of the 124 bp allele in a subset of 171 adoptees from the Iowa Adoption Studies, a population with high rates of MDD and SUD. We report that in our population, the 124 bp allele significantly associated with RE-MDD in women. There was slight evidence of an increased of SUD in women with the 124 bp allele with the rate of cannabis use disorders reaching statistical significance (P < 0.04) before correction for multiple comparisons. Given the history of prior studies implicating 2q35 as a locus encoding vulnerability to co-morbid alcoholism and depression, these findings strongly suggest that sequence variation conveying increased susceptibility to MDD and possibly SUD is in close proximity to D2S2944.