Wendy N. Zubenko

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.

Genomewide Significant Linkage to Recurrent, Early-Onset Major Depressive Disorder on Chromosome 15q

A genome scan was performed on the first phase sample of the Genetics of Recurrent Early-Onset Depression (GenRED) project. The sample consisted of 297 informative families containing 415 independent affected sibling pairs (ASPs), or, counting all possible pairs, 685 informative affected relative pairs (555 ASPs and 130 other pair types). Affected cases had recurrent major depressive disorder (MDD) with onset before age 31 years for probands or age 41 years for other affected relatives; the mean age at onset was 18.5 years, and the mean number of depressive episodes was 7.3. The Center for Inherited Disease Research genotyped 389 microsatellite markers (mean spacing of 9.3 cM). The primary linkage analysis considered allele sharing in all possible affected relative pairs with the use of the Z(lr) statistic computed by the ALLEGRO program. A secondary logistic regression analysis considered the effect of the sex of the pair as a covariate. Genomewide significant linkage was observed on chromosome 15q25.3-26.2 (Zlr=4.14, equivalent LOD = 3.73, empirical genomewide P=.023). The linkage was not sex specific. No other suggestive or significant results were observed in the primary analysis. The secondary analysis produced three regions of suggestive linkage, but these results should be interpreted cautiously because they depended primarily on the small subsample of 42 male-male pairs. Chromosome 15q25.3-26.2 deserves further study as a candidate region for susceptibility to MDD.

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.

Genetics of Recurrent Early-Onset Depression (GenRED): Design and preliminary clinical characteristics of a repository sample for genetic linkage studies

This is an initial report on a six‐site collaborative project, Genetics of Recurrent Early‐Onset Depression (GenRED). This is a study of a large sample of families with recurrent major depressive disorder (DSM‐IV) beginning by the age 30 in probands or 40 in relatives. Evidence suggests that early onset and recurrence of depressive episodes predict substantially increased risk of depression in first‐degree relatives compared with the general population, suggesting that susceptibility genes might be mapped with this phenotype. The projected sample of 800–1,000 affected sibling pairs (ASPs) and other relatives will be studied using genome scan methods. Biological materials and blinded clinical data will be made available through the NIMH cell repository program. The sample should have good‐to‐excellent power to detect a locus associated with a 24% or greater population‐wide increase in risk to siblings. We describe 838 affected individuals from the first 305 families containing 434 independent ASPs, or 613 ASPs counting all possible pairs. The mean age at the onset was 18.5 years, with a mean of 7.3 episodes and longest episode of 655 days. Almost all subjects had experienced at least 4 weeks of depression with five or more additional symptom criteria. Frequencies of symptoms and psychiatric and medical comorbid are provided. Substance use was more common in males, and panic disorder in females. Within pairs of affected siblings, correlations were significant for age at onset, substance abuse/dependence, panic disorder, obsessive‐compulsive disorder and nicotine initiation and persistence. We replicated previously reported associations among comorbid panic disorder and social phobia, chronicity of depression and suicidal behavior. This suggests comparability of our cases to those in earlier large family studies. This dataset should prove useful for genetic studies of a highly familial form of major depressive disorder.

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 ΔLOD 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 ΔLOD 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, ΔLOD = 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.

D2S2944 identifies a likely susceptibility locus for recurrent, early-onset, major depression in women

Recurrent, early-onset, major depressive disorder (RE-MDD) is a strongly familial condition whose malignant effects have a significant negative impact on the health and longevity of patients and their family members. Sixteen of the 19 candidate susceptibility loci identified by a recent genome survey revealed allelic associations with RE-MDD in men or women, but not in both sexes. The association of D2S2944 alleles and genotypes with RE-MDD and related disorders was evaluated using a case-control study design employing 100 adults with RE-MDD and 100 adult controls who had no personal or family history of mental disorders. The results of the case-control study were subsequently evaluated in a sample of 81 families ascertained through probands with RE-MDD using the transmission/disequilibrium test. The frequency of the D2S2944 124-bp allele among women with RE-MDD was approximately three times that for female controls (P = 0.0003). Women who carried the D2S2944 124-bp allele revealed a significantly elevated risk of developing RE-MDD, as indicated by an odds ratio of 4.5 compared to female controls (P<0.001). In contrast, men with RE-MDD did not have an increased frequency of this allele compared to male controls, and men who were carriers did not exhibit an increased risk of developing RE-MDD or related disorders. Our findings also suggest that the D2S2944 124-bp allele increases the risk of alcohol and other substance use disorders among women with RE-MDD. The transmission/disequilibrium test provided confirmatory evidence of these sex-specific findings within families. The results of this study confirm the existence of sex-specific susceptibility loci for RE-MDD, and suggest that there may be important differences in the molecular pathophysiology of RE-MDD in men and women. Alternatively, our findings may reflect the existence of sex-specific differences in the molecular mechanisms that determine resilience to endogenous or environmental depressogenic stimuli. The identification and characterization of the D2S2944 susceptibility locus for RE-MDD and related substance use disorders is likely to provide important new insights into the clinical biology, treatment, and prevention of these disorders.

Genetic segregation analysis of alcohol and other substance-use disorders in families with recurrent, early-onset major depression

Objective: The goal of this study was to conduct a complex segregation analysis of alcohol and other substance-use disorders in families identified by probands with recurrent, early-onset major depression (RE-MDD). Method: Eighty-one families were identified through probands over the age of 18, who met criteria for recurrent (≥2 episodes), early-onset (≤25 years), nonpsychotic, unipolar major depression (RE-MDD) and included 407 first-degree relatives and 835 extended relatives. Psychiatric diagnoses for probands and their family members who provided blood samples were formulated from structured personal interviews, structured family history assessments, and available medical records. The remaining family members who participated and those who were deceased were evaluated through the family history method augmented by available medical records. Best estimate diagnoses were made during a consensus conference according to established diagnostic criteria. Segregation analyses were performed using the REGD routine in S.A.G.E. release 4.0. Results: The best-fitting models for the transmission of “alcohol use disorders” or “alcohol/other substance use disorders” were sex-dependent Mendelian recessive models with significant residual spousal effects. Moreover, the parameter estimates for the models were very similar for these phenotypes. In contrast, the segregation analysis of “substance use disorder” supported a transmissible, but non-Mendelian, major effect. Conclusions: Our results suggest that a major locus contributes to the expression of alcohol use disorders or alcohol/other substance-use disorders within families identified by probands with RE-MDD. Due to the limitations of the segregation analysis model, our results cannot address whether the same major locus is segregating across families in our sample or whether multiple major loci are involved (genetic heterogeneity). Previous studies supported single gene transmission of recurrent major depression and major mood disorders in these families [Marazita et al. Am. J. Hum. Genet. 1997, 61, 1370–1378; Maher et al. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 2002, 114 (2), 214–221]. Mounting evidence suggests that at least some of this “comorbidity” may result from the effects of shared susceptibility genes or an overlap in the sets of genes that contribute to the vulnerability of developing these mental disorders [Zubenko, G.S. Mol. Psychiatry 2000, 5, 131–136].

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.

D10S1423 identifies a susceptibility locus for Alzheimer's disease (AD7) in a prospective, longitudinal, double‐blind study of asymptomatic individuals: Results at 14 years

Typical forms of Alzheimers disease (AD) appear to be influenced by multiple susceptibility loci. This report describes the prospective, longitudinal, double‐blind assessment of the age‐specific risk of AD encountered by 325 asymptomatic first‐degree relatives of AD probands who carried the D10S1423 (AD7) 234 bp allele, the APOE E4 allele, or both, after 14 years of systematic follow‐up. A total of 30 incident cases of AD were detected during the first 3752 subject‐years of surveillance. The effects of carrying either or both of the D10S1423 234 bp and APOE E4 alleles on the age‐specific risk of developing AD were determined using Kaplan–Meier survival analysis. The risk of developing AD was the greatest for individuals who carried both alleles (Mantel–Cox statistic = 16.46, df = 3, P = 0.0009; Breslow statistic = 13.38, df = 3, P = 0.004). Cox proportional hazards models were developed to estimate the risk ratios for each genotype, controlling for the potential effects of age at recruitment, sex, and years of education. Only individuals who carried both risk alleles exhibited a risk ratio that differed significantly from 1 (risk ratio = 7.5, P = 0.002, 95% CI = 2.1–27.0). Neither age at recruitment, sex, nor years of education made significant contributions to the model, although women tended to be at greater risk (P = 0.06). Recent evidence that D10S1423 resides within open reading frame C10orf112, whose predicted product resembles a low‐density lipoprotein receptor, suggests a molecular mechanism for this gene–gene interaction.