Genetic association study between antipsychotic-induced weight gain and the melanocortin-4 receptor gene

Antipsychotic-induced weight gain (AIWG) may result in the metabolic syndrome in schizophrenia (SCZ) patients. Downstream variants of the melanocortin-4 receptor (MC4R) gene have been associated with obesity in various populations. Thus, we examined single-nucleotide polymorphisms (SNPs) in the MC4R region for association with AIWG in SCZ patients. Four SNPs (rs2229616, rs17782313, rs11872992 and rs8087522) were genotyped in 224 patients who underwent treatment for SCZ and were evaluated for AIWG for up to 14 weeks. We compared weight change (%) across genotypic groups using analysis of covariance for three SNPs (r²≤0.8). European-ancestry patients who were rs8087522 A-allele carriers (AG+AA) on clozapine gained significantly more weight than non-carriers (P=0.027, n=69). These observations were marginal after correction for multiple testing. We performed in vitro electrophoretic mobility-shift assay that suggested that the presence of the A-allele may create a transcription factor-binding site. Further investigation is warranted for both these exploratory findings.

Replicated association of the NR4A3 gene with smoking behaviour in schizophrenia and in bipolar disorder

Schizophrenia and bipolar disorder are associated with dopamine neurotransmission and show high comorbidity with tobacco dependence. Recent evidence indicates that the family of the NR4A orphan nuclear receptors, which are expressed in dopamine neurons and in dopaminoceptive brain areas, may play a role in dopamine-mediated effects. We have, therefore, analysed the association of six single nucleotide polymorphisms (SNPs) within the three genes belonging to the NR4A orphan nuclear receptor family, NR4A1 (rs2603751, rs2701124), NR4A2 (rs12803, rs834835) and NR4A3 (rs1131339, rs1405209), with the degree of smoking in a sample of 204 unrelated schizophrenia patients, which included 126 smokers and 78 non-smokers. SNPs within the NR4A3 gene (rs1131339 and rs1405209) were significantly associated with heavy smoking in this cohort, using a stepwise analysis of the escalated number of cigarettes smoked per day (P = 0.008 and 0.006, respectively; satisfying the Nyholt significance threshold of 0.009, an adjustment for multiple testing). We then repeated the association analysis of the NR4A3 markers (rs1131339 and rs1405209) in a larger cohort of 319 patients with bipolar disorder, which included 167 smokers and 152 non-smokers. We have replicated the positive association with smoking of the NR4A3 SNP rs1131339 in this group (P = 0.04), providing an important confirmation of the involvement of the NR4A3 gene in nicotine addiction in patients with mental health disease, a population significantly at risk for nicotine addiction.

Opiates, overeating and obesity: a psychogenetic analysis

OBJECTIVE

This study provides an original perspective on the associations among endogenous opiates, overeating and obesity. The aim was to assess whether variability in the OPRM1 gene, as assessed by seven single-nucleotide polymorphisms, relates to individual differences in the preference for sweet and fatty foods. We also anticipated that these food preferences would be positively associated with binge eating, hedonic eating and emotionally driven eating-patterns of overeating that would, in turn, predict higher body mass index (BMI).

DESIGN

Analysis of variance procedures examined genotype differences in food preferences; bivariate correlation coefficients examined the relationships among food preferences and the overeating variables; and a regression analysis tested the combined influences of the overeating variables on BMI. DNA was extracted from whole blood for the genotyping, and measures of food preferences and eating behaviours were obtained from well-validated self-report questionnaires.

SUBJECTS

Participants were 300 healthy adult men and women recruited from the community.

RESULTS

All the predicted associations were supported by statistically significant results. In particular, the G/G genotype group of the functional A118G marker of the OPRM1 gene reported higher preferences for sweet and fatty foods compared with the other two groups. Food preferences were also related to all overeating measures, which in turn accounted for a substantial proportion of the variance in BMI.

CONCLUSIONS

Our findings suggest that some of the diversity in the preference for highly palatable foods can be explained by genotypic differences in the regulation of mu opioid receptors. The associations reported in this paper are important from a public-health perspective because of the abuse potential of sweet-fat foods and their strong relationship with obesity.

Association of the GABRD gene and childhood-onset mood disorders

The chromosome 1p36 region was previously indicated as a locus for susceptibility to recurrent major depressive disorder based on a linkage study in a sample of 497 sib pairs. We investigated the gamma-aminobutyric acid A (GABA(A)) delta receptor subunit gene, GABRD, as a susceptibility gene to childhood-onset mood disorders (COMD) because of substantial evidence implicating GABAergic dysfunction in mood disorders and the position of this gene near the 1p36 linkage region. Using a sample consisting of 645 Hungarian families with a child/adolescent proband diagnosed with a mood disorder with the onset of the first episode before age 15, we found some evidence for the association of two polymorphisms located within the gene, rs2376805 and rs2376803, as well as significant evidence for biased transmission of the haplotypes of these two markers (global chi(2) test for haplotypes = 12.746, 3 df, P = 0.0052). Furthermore, significant evidence of association was only observed in male subjects (n = 438) when the results were analyzed by sex (chi(2) = 9.000 1 df, P = 0.003 for rs2376805). This was in contrast with the previous linkage findings, as LOD scores exceeding 3 were only in female-female pairs in that study. These findings point to the GABRD gene as a susceptibility gene for COMD; however, this gene may not explain the previous linkage finding.

Association of HPA axis genes with suicidal behaviour in schizophrenia

Family, adoption and twin studies show that genetics influences suicidal behaviour, but do not indicate specific susceptibility variants. Stress response is thought to be mediated by the corticotrophin-releasing hormone (CRH), which is known to be a regulator of the hypothalamic-pituitary-adrenal pathway (HPA). Alterations in HPA system have been related to impulsivity, aggression and suicidal behaviour, common feature in schizophrenia. CRH is the hypothalamic factor that stimulates the pituitary gland. To search for markers conferring genetic susceptibility to suicide, we typed six HPA axis genes (CRH, CRHR1, CRHR2, CRHBP, MC2R, NC3R1) in a cohort of 231 subjects with schizophrenia in which 81 attempted suicide. The genotype analyses yielded significant association between CRH binding protein (CRHBP) and suicide attempt (P = 0.035). The genotype analysis for quantitative measures of suicidal behaviour showed no association. The interaction analysis showed a significant interaction between CRH receptor type 1 (CRHR1) and CRH binding protein (CRHBP) in influencing suicide attempt and the severity of suicidal behaviour. Current results show that genetic variation in HPA axis genes could be associated with suicidal behaviour in schizophrenia. This is to our knowledge the first study on suicidal behaviour investigating the interaction among the HPA axis genes.

Serotonin transporter polymorphisms (SLC6A4 insertion/deletion and rs25531) do not affect the availability of 5-HTT to [11C] DASB binding in the living human brain

Studies in vitro suggest that the expression of the serotonin transporter (5-HTT) is regulated by polymorphic variation in the promoter region of the 5-HTT gene (5-HTTLPR); however, results from human brain imaging studies examining the relation between 5-HTT genotype and 5-HTT radioligand binding in vivo have been inconsistent. This inconsistency could reflect small participant numbers or the use of sub-optimal radiotracer for measuring the 5-HTT. We used positron emission tomography in conjunction with the selective 5-HTT ligand [(11)C] DASB to examine the availability of the 5-HTT in seven brain regions in 63 healthy European caucasian volunteers who were genotyped for short (S) and long (L) variants (SLC6A4 and rs25531) of the 5-HTTLPR. [(11)C] DASB binding potential was not influenced by the allelic status of participants whether classified on a biallelic or triallelic basis in any of the regions studied. Our PET findings, in a relatively large sample with a near optimal radiotracer, suggest that 5-HTTLPR polymorphic variation does not affect the availability of 5-HTT to [(11)C] DASB binding in adult human brain. The reported impact of 5-HTTLPR polymorphic variation on emotional processing and vulnerability to depression are more likely therefore to be expressed through effects exerted during neurodevelopment.

Effect of dopamine D3 receptor gene polymorphisms and clozapine treatment response: exploratory analysis of nine polymorphisms and meta-analysis of the Ser9Gly variant

D2 blockade has been implicated in having a central role in antipsychotic response. However, treatment refractoriness, in spite of complete D2 blockade, as well as the efficacy of clozapine (CLZ) in a portion of this patient population, indicates the involvement of other factors as well. Several lines of evidence suggest a role for D3. Furthermore, an earlier meta-analysis by Jönsson et al. (2003) (n=233) suggested a role for genetic variation in the D3 gene. Relevant to this study, Jönsson et al. found the Ser allele of the D3 serine-to-glycine substitution at amino acid position 9 (Ser9Gly) polymorphism to be associated with worse CLZ response compared with the Gly allele. In this study, we attempt to validate these findings by performing a meta-analysis in a much larger sample (n=758). Eight other variants were also tested in our own sample to explore the possible effect of other regions of the gene. We report a negative but consistent trend across individual studies in our meta-analysis for the DRD3 Ser allele and poor CLZ response. A possible minor role for this single-nucleotide polymorphism cannot be disregarded, as our sample size may have been insufficient. Other DRD3 variants and haplotypes of possible interest were also identified for replication in future studies.

Mutation screen and association analysis of the glucocorticoid receptor gene (NR3C1) in childhood-onset mood disorders (COMD)

Depressive disorders are highly heterogeneous psychiatric disorders involving deficits to cognitive, psychomotor, and emotional processing. Considerable evidence links disruption to the hypothalamic-pituitary-adrenal (HPA) axis to the etiology of depression, with specific deficits reported in glucocorticoid receptor (GR)-mediated negative feedback. Given the role of GR-mediated negative feedback in mediating response to stress, and the clear link between stress and depression, it is plausible that polymorphisms in the GR gene (NR3C1) act to increase susceptibility. Maternal behavior in rats epigenetically alters a NGF1-A transcription factor binding-site in the promoter region of the GR gene, providing a mechanism by which environmental cues can regulate GR expression and thus response to stress. The analogous region of the human GR gene (NR3C1) has not been studied, but it is possible that polymorphisms in this region may alter the binding of transcription factors known to regulate GR expression. In this study, we have performed bioinformatic analyses on the promoter region of NR3C1 to identify conserved promoter sequences and predicted transcription factor binding sites. These regions were screened with denaturing high-performance liquid chromatography (DHPLC) and direct re-sequencing, and several novel polymorphic variants were identified. We genotyped nine polymorphisms across NR3C1 in a large sample of Hungarian nuclear families ascertained through affected probands with a diagnosis of childhood-onset mood disorders (COMD). Single-marker analysis provided little evidence for an association of this gene with COMD, but multi-marker analysis across a region of high linkage disequilibrium revealed modest evidence for the biased transmission of several haplotypes.

Cytokine Genes TNF, IL1A, IL1B, IL6, IL1RN and IL10, and childhood-onset mood disorders

BACKGROUND/AIMS

Inflammatory cytokines induce a behavioral syndrome, known as sickness behavior, that strongly resembles symptoms typically seen in depression. This resemblance has led to the theory that an imbalance of inflammatory cytokine activity may be a contributing factor in depressive disorders. Support for this is found in multiple lines of evidence, such as the effects of cytokines on the activities of the hypothalamic-pituitary-adrenal axis, serotonin and brain-derived neurotrophic factor, and hippocampal function, all of which are implicated in the etiology of depression. In addition, associations between inflammatory activity and depressive symptomology have been documented in a number of studies, and the depressogenic effects of cytokine therapy are well known. Accordingly, given that depression has a substantial genetic basis, genes involved in the regulation of inflammatory cytokine activity are strong candidates for involvement in genetic susceptibility to depressive disorders. Here, we have tested 6 key genes of this type, TNF, IL1A, IL1B, IL6, IL1RN and IL10, as candidates for involvement in childhood-onset mood disorders.

METHODS

In this study of 384 families, each ascertained through a child with depression diagnosed before the age of 15 years, 11 polymorphisms of known or likely functional significance (coding and regulatory variants) were analyzed.

RESULTS

Testing for biased transmission of alleles from parents to their affected offspring, we found no evidence for an association between childhood-onset mood disorders and any of the polymorphisms, either individually or as haplotypes.

CONCLUSION

The present study does not support the involvement of the TNF, IL1A, IL1B, IL6, IL1RN and IL10 variants as major genetic risk factors contributing to early-onset mood disorders.

Association of ADHD and the Protogenin gene in the chromosome 15q21.3 reading disabilities linkage region

Twin studies indicate genetic overlap between symptoms of attention deficit hyperactivity disorder (ADHD) and reading disabilities (RD), and linkage studies identify several chromosomal regions possibly containing common susceptibility genes, including the 15q region. Based on a translocation finding and association to two specific alleles, the candidate gene, DYX1C1, has been proposed as the susceptibility gene for RD in 15q. Previously, we tested markers in DYX1C1 for association with ADHD. Although we identified association for haplotypes across the gene, we were unable to replicate the association to the specific alleles reported. Thus, the risk alleles for ADHD are yet to be identified. The susceptibility alleles may be in a remote regulatory element, or DYX1C1 may not be the risk gene. To continue study of 15q, we tested a coding region change in DYX1C1, followed by markers across the gene Protogenin (PRTG) in 253 ADHD nuclear families. PRTG was chosen based on its location and because it is closely related to DCC and Neogenin, two genes known to guide migratory cells and axons during development. The markers in DYX1C1 were not associated to ADHD when analyzed individually; however, six markers in PRTG showed significant association with ADHD as a categorical trait (P = 0.025-0.005). Haplotypes in both genes showed evidence for association. We identified association with ADHD symptoms measured as quantitative traits in PRTG, but no evidence for association with two key components of reading, word identification and decoding was observed. These findings, while preliminary, identify association of ADHD to a gene that potentially plays a role in cell migration and axon growth.

QUANTITATIVE EXAMINATION OF A NOVEL CLUSTERING METHOD USING MAGNETIC RESONANCE DIFFUSION TENSOR TRACTOGRAPHY

Introduction: MR diffusion tensor imaging (DTI) is the most powerful and currentlythe only way to visualize the organization of white matter fiber tracts in vivo. As this is a relatively newimaging technique, new tools are developed for quantifying fiber tracts, andrequire evaluation. We examined scalar indices of the diffusion tensor with two different tractography methods. We compared a novel clustering approach with a multiple region of interest (MROI) approach in a healthy and disease (schizophrenia) population. Methods: DTI images were acquired in 12 participants (n=6 patients withschizophrenia: 58 ± 12 years; n=6 controls: 57 ± 21 years) on a 1.5 Tesla GE system with diffusion gradients applied in 23 non-collinear directions, repeated three times. Tractography andfiber tract creation was performed using 3D Slicer software. Interraterreliability of the clustering approach and its similarity to the MROI methodwere evaluated. Results: The clustering approach was reliable both quantitatively and spatially (k > 0.8 for all tracts). There was high spatial(voxel-based) agreement between the clustering and MROI methods. Fractionalan isotropy and trace values were highly correlated between the clustering and MROI methods (p < 0.001 for all tracts). Discussion: Our clustering method has excellent interrater reliability and thereis a high level of agreement between our clustering method and the MROI method, both quantitatively and spatially. The clustering method is less susceptible touser bias. Moreover, not limited by a priori predictions, our clustering method may be a more robust and efficient way to identify and measure fiber tracts of interest. (colour figure available in PDF version)

Family history of depression is associated with younger age of onset in patients with recurrent depression

BACKGROUND

Genetic epidemiology data suggest that younger age of onset is associated with family history (FH) of depression. The present study tested whether the presence of FH for depression or anxiety in first-degree relatives determines younger age of onset for depression.

METHOD

A sample of 1022 cases with recurrent major depressive disorder (MDD) was recruited at the Max Planck Institute and at two affiliated hospitals. Patients were assessed using the Schedules for Clinical Assessment in Neuropsychiatry and questionnaires including demographics, medical history, questions on the use of alcohol and tobacco, personality traits and life events. Survival analysis and the Cox proportional hazard model were used to determine whether FH of depression signals earlier age of onset of depression.

RESULTS

Patients who reported positive FH had a significantly earlier age of onset than patients who did not report FH of depression (log-rank=48, df=1, p<0.0001). The magnitude of association of FH varies by age of onset, with the largest estimate for MDD onset before age 20 years (hazard ratio=2.2, p=0.0009), whereas FH is not associated with MDD for onset after age 50 years (hazard ratio=0.89, p=0.5). The presence of feelings of guilt, anxiety symptoms and functional impairment due to depressive symptoms appear to characterize individuals with positive FH of depression.

CONCLUSIONS

FH of depression contributes to the onset of depression at a younger age and may affect the clinical features of the illness.

Thermally compensated temperature sensor capable of highly accurate measurements on surfaces

A thermally compensated temperature sensor capable of highly accurate determination of surface temperatures has been demonstrated. The probe consists of a single crystal Y(3)Al(5)O(12) fiber terminating in a laser-heated Yb(3)Al(5)O(12) phosphor. It has been shown to have a measurement accuracy of approximately 1 degrees C. In principle, this device should work in the proximity as well as the contact mode.

Pharmacogenetic studies in depression: a proposal for methodologic guidelines

Pharmacogenetic studies in mood disorders are rapidly proliferating after the initial reports linking gene variants to treatment outcomes. However, a considerable range of methodologies has been used, making it difficult to compare results across studies and limiting the representativeness of findings. Specification of sampling source (inpatients vs outpatients, primary vs tertiary settings), standardization of diagnostic systems and treatments, adequate monitoring of compliance through plasma levels, sufficient length of observation (at least 6 weeks for acute antidepressant treatments, though 3-6 months are preferable), the use of a range of response criteria and the inclusion of possible environmental confounding variables (life events, social support, temperament) are all potentially important issues when planning pharmacogenetic studies. We reviewed the state-of-the-art methodology and suggested possible guideline for future studies.

p75(NTR) gene and suicide attempts in young adults with a history of childhood-onset mood disorder

Recently, evidence has accumulated for the role of neurotrophic processes in mood disorders. Neurotrophins operate on receptors, one of which is the p75 neurotrophin receptor (p75(NTR)). We examined three p75(NTR) markers at the p75(NTR) gene, including a missense polymorphism that changes serine to leucine (S205L), for association with suicide attempt (SA) in 203 childhood-onset mood disorder (COMD) cases. There was no difference between COMD suicide attempters and COMD non-attempters with logistic regression models for any of the three markers. We also compared the three polymorphisms between 192 COMD cases and 192 matched healthy controls and found no significant differences between COMD and healthy controls. Our results do not support an association of the p75(NTR) S205L polymorphism with risk for COMD or SA in COMD.

Association study of the nicotinic acetylcholine receptor alpha4 subunit gene, CHRNA4, in attention-deficit hyperactivity disorder

Attention-deficit hyperactivity disorder (ADHD) is a common childhood-onset psychiatric condition with a strong genetic component. Evidence from pharmacological, clinical and animal studies has suggested that the nicotinic system could be involved in the disorder. Previous studies have implicated the nicotinic acetylcholine receptor alpha4 subunit gene, CHRNA4, in ADHD. Particularly, a polymorphism in the exon 2-intron 2 junction of CHRNA4 has been associated with severe inattention defined by latent class analysis. In the current study, we used the transmission disequilibrium test (TDT) to investigate four polymorphisms encompassing this region of CHRNA4 for association with ADHD in a sample of 264 nuclear families from Toronto. No significant evidence of biased transmission was observed for any of the marker alleles for ADHD defined as a categorical trait (all subtypes included), although one haplotype showed marginal evidence of under-transmission. No association was found with the ADHD predominantly inattentive subtype or with symptom dimension scores of inattention. On the contrary, nominally significant evidence of association of individual markers was obtained for the ADHD combined subtype and with teacher-rated hyperactivity-impulsivity scores, with the same haplotype being under-transmitted. Based on our results and others, CHRNA4 may be involved in ADHD; however, its role in ADHD symptomatology remains to be clarified.

Association of the glutamate receptor subunit gene GRIN2B with attention-deficit/hyperactivity disorder

The glutamatergic signaling pathway represents an ideal candidate susceptibility system for attention-deficit/hyperactivity disorder (ADHD). Disruption of specific N-methyl-D-aspartate-type glutamate receptor subunit genes (GRIN1, 2A-D) in mice leads to significant alterations in cognitive and/or locomotor behavior including impairments in latent learning, spatial memory tasks and hyperactivity. Here, we tested for association of GRIN2B variants with ADHD, by genotyping nine single nucleotide polymorphisms (SNPs) in 205 nuclear families identified through probands with ADHD. Transmission of alleles from heterozygous parents to affected offspring was examined using the transmission/disequilibrium test. Quantitative trait analyses for the ADHD symptom dimensions [inattentive (IA) and hyperactive/impulsive (HI)] and cognitive measures of verbal working memory and verbal short-term memory were performed using the fbat program. Three SNPs showed significantly biased transmission (P < 0.05), with the strongest evidence of association found for rs2,284,411 (chi(2)= 7.903, 1 degree of freedom, P= 0.005). Quantitative trait analyses showed associations of these markers with both the IA and the HI symptom dimensions of ADHD but not with the cognitive measures of verbal short-term memory or verbal working memory. Our data suggest an association between variations in the GRIN2B subunit gene and ADHD as measured categorically or as a quantitatively distributed trait.

Regulation of alpha7-nicotinic receptor subunit and alpha7-like gene expression in the prefrontal cortex of patients with bipolar disorder and schizophrenia

OBJECTIVE

The alpha7-nicotinic receptor subunit gene (CHRNA7) is located at chromosome 15q13-14, a region previously linked with schizophrenia. Genetic association and mRNA expression studies also implicate CHRNA7 in schizophrenia. The CHRNA7 gene has a partial duplication that constitutes the alpha7-like nicotinic receptor gene (CHRFAM7A). We hypothesized that major psychoses could affect the expression of both CHRNA7 and CHRFAM7A.

METHOD

CHRNA7 and CHRFAM7A mRNA levels were measured in postmortem prefrontal cortex (donated by the Stanley Foundation) from subjects with schizophrenia, bipolar disorder and unaffected controls (n = 35 each).

RESULTS

The mRNA levels of alpha7 and alpha7-like genes have a positive correlation overall (r = 0.25; P = 0.009), however, there is no significant difference in the expression of CHRNA7 among the three diagnostic groups.

CONCLUSION

This correlation is driven by the bipolar group (r = 0.43; P = 0.009), and is absent in schizophrenia and unaffected controls, suggesting an alteration in the CHRNA7:CHRFAM7A ratio in bipolar disorder.

The interaction between TPH2 promoter haplotypes and clinical-demographic risk factors in suicide victims with major psychoses

Tryptophan hydroxylase isoform 2 (TPH2) is a rate-limiting enzyme in the biosynthesis of serotonin (5-HT) and is predominantly localized in the brain. Previous studies have suggested that there is an association between serotonergic dysfunction in the brain and suicidality. This study was designed to examine whether the -473T > A and -8396G > C polymorphisms of the TPH2 gene may be associated with completed suicide in subjects with major psychoses from the Stanley Foundation Brain Bank sample. TPH2 genotypes were determined in 69 subjects with a diagnosis of schizophrenia or bipolar disorder, among which 22 died by suicide. Genomic DNA was amplified by polymerase chain reaction and typed by automated methods. Both markers were found to be in Hardy-Weinberg equilibrium and in strong linkage disequilibrium. No association with history of suicide was found for either polymorphism. Haplotype analysis with EHAP showed no association between completed suicide and haplotype distribution (chi2 = 1.877; 3 df; P = 0.598). Nor was there any association between suicide and these genetic markers even when clinical-demographic factors were considered as covariates in the haplotype analysis. These findings suggest that these 5' marker haplotypes in the TPH2 gene do not influence suicidal behaviour.