James L. Kennedy

Serotonin Transporter Promoter Gain-of-Function Genotypes Are Linked to Obsessive-Compulsive Disorder

A functional serotonin transporter promoter polymorphism, HTTLPR, alters the risk of disease as well as brain morphometry and function. Here, we show that HTTLPR is functionally triallelic. The L(G) allele, which is the L allele with a common G substitution, creates a functional AP2 transcription-factor binding site. Expression assays in 62 lymphoblastoid cell lines representing the six genotypes and in transfected raphe-derived cells showed codominant allele action and low, nearly equivalent expression for the S and L(G) alleles, accounting for more variation in HTT expression than previously recognized. The gain-of-function L(A)L(A) genotype was approximately twice as common in 169 whites with obsessive-compulsive disorder (OCD) than in 253 ethnically matched controls. We performed a replication study in 175 trios consisting of probands with OCD and their parents. The L(A) allele was twofold overtransmitted to the patients with OCD. The HTTLPR L(A)L(A) genotype exerts a moderate (1.8-fold) effect on risk of OCD, which crystallizes the evidence that the HTT gene has a role in OCD.

The brain-derived neurotrophic factor gene confers susceptibility to bipolar disorder: evidence from a family-based association study.

Bipolar disorder (BP) is a severe psychiatric disease, with a strong genetic component, that affects 1% of the population worldwide and is characterized by recurrent episodes of mania and depression. Brain-derived neurotrophic factor (BDNF) has been implicated in the pathogenesis of mood disorders, and the aim of the present study was to test for the presence of linkage disequilibrium between two polymorphisms in the BDNF gene and BP in 283 nuclear families. Family-based association test (FBAT) results for the dinucleotide repeat (GT)(N) polymorphism at position -1040 bp showed that allele A3 was preferentially transmitted to the affected individuals (Z=2.035 and P=.042). FBAT results for the val66met SNP showed a significant association for allele G (Z=3.415 and P=.00064). Transmission/disequilibrium test (TDT) haplotype analysis showed a significant result for the 3-G allele combination (P=.000394), suggesting that a DNA variant in the vicinity of the BDNF locus confers susceptibility to BP. Given that there is no direct evidence that either of the polymorphisms we examined alters function, it is unlikely that the actual risk-conferring allele is from these two sites. Rather, the causative site is likely nearby and in linkage disequilibrium with the 3-G haplotype that we have identified.

A human gene that shows identity with the gene encoding the angiotensin receptor is located on chromosome 11

We report the cloning of a gene, intronless in its coding region, which we have named APJ. This gene was cloned using the polymerase chain reaction (PCR), with a set of primers designed on the basis of the conservation that members of G protein-coupled receptors (GPCR) have in their transmembrane (TM) regions. The putative receptor protein, APJ, shares closest identity to the angiotensin receptor (AT1) ranging from 40 to 50% in the hydrophobic TM regions of these receptors. The transcripts for this gene were detected in many regions of the brain. PCR analysis of somatic cell lines found APJ-related sequences to be only present on chromosome 11, and high-resolution mapping by fluorescence in situ hybridization (FISH) sublocalized APJ on band q12.

Association of the dopamine receptor D4 (DRD4) gene with a refined phenotype of attention deficit hyperactivity disorder (ADHD): a family-based approach

Previously in this journal, we reported an association of the dopamine D4 receptor gene (DRD4) and attention deficit hyperactivity disorder (ADHD). In a population-association (case-control) study of 39 children with a refined phenotype of ADHD and 39 ethnically matched controls, we observed an increased percentage of the 7 repeat allele (29% vs 12%) and the 7+ genotype (49% vs 21%) in the ADHD group compared to the control group. In a replication and an extension of our initial study, we recruited another sample of ADHD subjects and found percentages of the 7 repeat allele (28%) and the 7+ genotype (48%) consistent with our previous findings. We used a family-based approach to evaluate a predicted association of DRD4 and ADHD based on a test of allele transmission focused on the 7 repeat allele. We identified 52 families based on the diagnosis of the refined phenotype of ADHD in the proband and the availability of DNA from both biological parents as well as the proband. Haplotype relative risk (HRR) analysis was performed to test our a priori hypothesis and produced significant results (chi-square = 4.65, P < 0.035). this provides additional evidence that the drd4 gene is associated with a refined phenotype of adhd.

Genome-wide association and meta-analysis of bipolar disorder in individuals of European ancestry

Bipolar disorder (BP) is a disabling and often life-threatening disorder that affects ≈1% of the population worldwide. To identify genetic variants that increase the risk of BP, we genotyped on the Illumina HumanHap550 Beadchip 2,076 bipolar cases and 1,676 controls of European ancestry from the National Institute of Mental Health Human Genetics Initiative Repository, and the Prechter Repository and samples collected in London, Toronto, and Dundee. We imputed SNP genotypes and tested for SNP-BP association in each sample and then performed meta-analysis across samples. The strongest association P value for this 2-study meta-analysis was 2.4 × 10−6. We next imputed SNP genotypes and tested for SNP-BP association based on the publicly available Affymetrix 500K genotype data from the Wellcome Trust Case Control Consortium for 1,868 BP cases and a reference set of 12,831 individuals. A 3-study meta-analysis of 3,683 nonoverlapping cases and 14,507 extended controls on >2.3 M genotyped and imputed SNPs resulted in 3 chromosomal regions with association P ≈ 10−7: 1p31.1 (no known genes), 3p21 (>25 known genes), and 5q15 (MCTP1). The most strongly associated nonsynonymous SNP rs1042779 (OR = 1.19, P = 1.8 × 10−7) is in the ITIH1 gene on chromosome 3, with other strongly associated nonsynonymous SNPs in GNL3, NEK4, and ITIH3. Thus, these chromosomal regions harbor genes implicated in cell cycle, neurogenesis, neuroplasticity, and neurosignaling. In addition, we replicated the reported ANK3 association results for SNP rs10994336 in the nonoverlapping GSK sample (OR = 1.37, P = 0.042). Although these results are promising, analysis of additional samples will be required to confirm that variant(s) in these regions influence BP risk.

Role of Translocator Protein Density, a Marker of Neuroinflammation, in the Brain During Major Depressive Episodes

IMPORTANCE The neuroinflammatory hypothesis of major depressive disorder is supported by several main findings. First, in humans and animals, activation of the immune system causes sickness behaviors that present during a major depressive episode (MDE), such as low mood, anhedonia, anorexia, and weight loss. Second, peripheral markers of inflammation are frequently reported in major depressive disorder. Third, neuroinflammatory illnesses are associated with high rates of MDEs. However, a fundamental limitation of the neuroinflammatory hypothesis is a paucity of evidence of brain inflammation during MDE. Translocator protein density measured by distribution volume (TSPO VT) is increased in activated microglia, an important aspect of neuroinflammation. OBJECTIVE To determine whether TSPO VT is elevated in the prefrontal cortex, anterior cingulate cortex (ACC), and insula in patients with MDE secondary to major depressive disorder. DESIGN, SETTING, AND PARTICIPANTS Case-control study in a tertiary care psychiatric hospital from May 1, 2010, through February 1, 2014. Twenty patients with MDE secondary to major depressive disorder and 20 healthy control participants underwent positron emission tomography with fluorine F 18-labeled N-(2-(2-fluoroethoxy)benzyl)-N-(4-phenoxypyridin-3-yl)acetamide ([18F]FEPPA). Patients with MDE were medication free for at least 6 weeks. All participants were otherwise healthy and nonsmokers. MAIN OUTCOMES AND MEASURES Values of TSPO VT in the prefrontal cortex, ACC, and insula. RESULTS In MDE, TSPO VT was significantly elevated in all brain regions examined (multivariate analysis of variance, F15,23 = 4.5 [P = .001]). The magnitude of TSPO VT elevation was 26% in the prefrontal cortex (mean [SD] TSPO VT, 12.5 [3.6] in patients with MDE and 10.0 [2.4] in controls), 32% in the ACC (mean [SD] TSPO VT, 12.3 [3.5] in patients with MDE and 9.3 [2.2] in controls), and 33% in the insula (mean [SD] TSPO VT, 12.9 [3.7] in patients with MDE and 9.7 [2.3] in controls). In MDE, greater TSPO VT in the ACC correlated with greater depression severity (r = 0.63 [P = .005]). CONCLUSIONS AND RELEVANCE This finding provides the most compelling evidence to date of brain inflammation, and more specifically microglial activation, in MDE. This finding is important for improving treatment because it implies that therapeutics that reduce microglial activation should be promising for MDE. The correlation between higher ACC TSPO VT and the severity of MDE is consistent with the concept that neuroinflammation in specific regions may contribute to sickness behaviors that overlap with the symptoms of MDE.

Pharmacogenetics of Tardive Dyskinesia: Combined Analysis of 780 Patients Supports Association with Dopamine D3 Receptor Gene Ser9Gly Polymorphism

Variability among individuals in their therapeutic response to psychotropic drugs and in susceptibility to adverse effects is considerable. Pharmacogenetics addresses the contribution of genetic factors to this variability. An important focus of interest in pharmacogenetics has been on candidate genes that play a role in susceptibility to the antipsychotic drug-induced adverse effect, tardive dyskinesia (TD). Four published studies have reported an association between a serine (ser) to glycine (gly) polymorphism in exon 1 of the dopamine D3 receptor gene (DRD3) and TD; three failed to replicate this finding and one found an insignificant trend. We examined the association in a pooled sample of 780 patients (317 with TD and 463 without TD) drawn from 6 research centers, who were divided into 8 groups based on their population origin. The analysis employed stepwise logistic regression so as to allow confounding effects of group, age, and gender to be taken into account. TD was significantly associated with DRD3 gly allele carrier status (x2=4.46, df 1, p = .04) and with DRD3 genotype (x2=6.62, df 2, p = .04) over and above the effect of group. Similar positive effects were observed when controlling for age and gender (x2=5.02, df 1, p = .02 for gly allele carrier status; x2 = 7.51, df 2, p = .002 for genotype). Examining abnormal involuntary movement scores as a continuous variable, we found that patients homozygous for the gly allele had significantly higher scores than ser-gly heterozygotes (p = .006) or ser-ser homozygotes (p < .0001). We also performed a meta-analysis that included, besides the groups in the combined analysis, three other published studies on DRD3 and TD. The Mantel-Haenszel pooled odds ratio for DRD3 gly allele carrier status increasing susceptibility to TD was 1.33 (95% CI 1.04–1.70, p = .02); the cumulative pooled estimate showed an odds ratio of 1.52 (95% CI 1.08–1.68, p < .0001). These findings support a small but significant contribution of the DRD3 ser9gly polymorphism to TD susceptibility that is demonstrable over and above population effects and the effect of age and gender on the phenotype.

Serotonin subtype 2 receptor genes and clinical response to clozapine in schizophrenia patients

Using a pharmacogenetic approach in 185 schizophrenics who have been prospectively assessed for clozapine response, we have examined the hypothesis that polymorphisms in the 5-HT2A (HTR2A), and 5-HT2C (HTR2C) genes are involved in its variable response. A -1438 A→G polymorphism in the putative promoter and a silent T→C 102 substitution in HTR2A were in almost complete linkage disequilibrium, and neither was associated with response (T→C 102 allele: χ2 = 0.02; 1 df, p = .90; genotype: χ2 = 0.02, 2 df, p = .99). A his452tyr HTR2A polymorphism was found to be associated with clozapine response (his452tyr allele: χ2 = 6.43, 1 df, p = .01 [p = .04, Bonferroni corrected]; genotype: χ2 = 6.54, 2 df, p = .04 [p = .16, Bonferroni corrected]). No HTR2A haplotype was associated with response. Interethnic differences were observed in the frequencies of the cys23ser HTR2C polymorphism. This polymorphism was not significantly associated with response in either of the ethnic groups (Caucasian and African American genotype: χ2 = 3.46, 2 df, p = .18; χ2 = .31, 2 df, p = .86, respectively). Although replication is required, the overall results suggest that the his452tyr HTR2A polymorphism may be involved in clozapine response.

Dopamine for "wanting" and opioids for "liking": a comparison of obese adults with and without binge eating.

Obesity research suffers from an overinclusion paradigm whereby all participants with a BMI beyond a certain cutoff value (e.g., 30) are typically combined in a single group and compared to those of normal weight. There has been little attempt to identify meaningful subgroups defined by their salient biobehavioral differences. In order to address this limitation, we examined genetic and psychological indicators of hedonic eating in obese adults with (n = 66) and without (n = 70) binge eating disorder (BED). Our analyses focused on dopamine (DA) and opioid genetic markers because of their conjoint association with the functioning of brain reward mechanisms. We targeted three functional polymorphisms related to the D2 receptor (DRD2) gene, as well as the functional A118G polymorphism of the mu‐opioid receptor (OPRM1) gene. We found that significantly more obese controls had the “loss‐of‐function” A1 allele of Taq1A compared to their BED counterparts, whereas the “gain‐of‐function” G allele of A118G occurred with greater frequency in the BED group. A significant gene–gene combination χ2 analysis also indicated that of those participants with the gain‐gain genotype (G+ and A1), 80% were in the BED group whereas only 35% with the loss‐loss genotype (G− and A1+) were in this group. Finally, BED subjects had significantly higher scores on a self‐report measure of hedonic eating. Our findings suggest that BED is a biologically based subtype of obesity and that the proneness to binge eating may be influenced by a hyper‐reactivity to the hedonic properties of food—a predisposition that is easily exploited in our current environment with its highly visible and easily accessible surfeit of sweet and fatty foods.

Early age at onset as a risk factor for poor outcome of bipolar disorder

The primary aim of our study was to investigate the effect of the age at onset (AAO) of Bipolar Disorder (BP) on the clinical course of the illness. We studied 320 subjects with a diagnosis of BP I or BP II who had been previously recruited for a genetic research protocol. All subjects gave their informed consent to participate in the study. Each subject was interviewed using the SCID I. The main clinical variables were compared between subjects with early (</=18 years) and later (>/=18 years) age at onset of BP (chi square tests and t-tests for independent samples). In addition, a logistic regression analysis was applied to the variables that were significantly related to earlier onset of BP in the exploratory analyses. We found a significantly earlier AAO in subjects with anxiety disorders (t=2.44, P=0.015) and rapid cycling course (t=3.16, P=0.002). When we compared a number of clinical characteristics between early and later onset of BP, subjects with early AAO had more frequent suicidal ideation/attempts (chi(2)=12.12, P=0.002), Axis I comorbidity (chi(2)=8.12, P=0.004), substance use disorders (chi(2)=5.45, P=0.019) and rapid cycling course (chi(2)=9.87, P=0.002). The Odds Ratios associated with these variables were: 1.407 (suicide ideation), 1.646 (Axis I comorbidity), 1.468 (substance abuse), and 2.082 (rapid cycling course). Overall, these results suggest a role of early AAO as a significant predictor of poor outcome in BP and, if replicated, they may have important clinical implications.