Genetic predictors of response to treatment with citalopram in depression secondary to traumatic brain injury.

OBJECTIVES: To determine which serotonergic system-related single nucleotide polymorphisms (SNPs) predicted variation in treatment response to citalopram in depression following a traumatic brain injury (TBI). METHODS: Ninety (50 M/40 F, aged 39.9, SD = 18.0 years) post-TBI patients with a major depressive episode (MDE) were recruited into a 6-week open-label study of citalopram (20 mg/day). Six functional SNPs in genes related to the serotonergic system were examined: serotonin transporter (5HTTLPR including rs25531), 5HT1A C-(1019)G and 5HT2A T-(102)C, methylene tetrahydrofolate reductase (MTHFR) C-(677)T, brain-derived neurotrophic factor (BDNF) val66met and tryptophan hydroxylase-2 (TPH2) G-(703)T. Regression analyses were performed using the six SNPs as independent variables: Model 1 with response (percentage Hamilton Depression (HAMD) change from baseline to endpoint) as the dependent variable and Model 2 with adverse event index as the dependent variable (Bonferroni corrected p-value < 0.025). RESULTS: MTHFR and BDNF SNPs predicted greater treatment response (R(2)= 0.098, F = 4.65, p = 0.013). The 5HTTLPR predicted greater occurrence of adverse events (R(2)= 0.069, F = 5.72, p = 0.020). CONCLUSION: Results suggest that polymorphisms in genes related to the serotonergic system may help predict short-term response to citalopram and tolerability to the medication in patients with MDE following a TBI.

Glutamate receptor gene (GRIN2B) associated with reduced anterior cingulate glutamatergic concentration in pediatric obsessive-compulsive disorder.

In this preliminary study, 16 psychotropic-naïve pediatric patients with obsessive-compulsive disorder (OCD) were studied using magnetic resonance spectroscopy (MRS) and genotyped for six candidate polymorphisms in two glutamate system genes. A significant association was identified between the rs1019385 polymorphism of the glutamate receptor, ionotropic, N-methyl-d-aspartate 2B (GRIN2B) and decreased anterior cingulate cortex (ACC) glutamatergic concentration (Glx) but not with occipital Glx. These results suggest that GRIN2B may be associated with Glx in the ACC, a region consistently implicated in OCD.

Glutamate system genes associated with ventral prefrontal and thalamic volume in pediatric obsessive-compulsive disorder.

This pilot study was undertaken to determine if there was a significant association between specific glutamate system genes and regional volumes of interest implicated in the pathogenesis of obsessive-compulsive disorder (OCD). Volumetric magnetic resonance imaging (MRI) and genotyping of 7 polymorphisms in two genes, glutamate receptor, ionotropic, N-methyl-d-aspartate 2B (GRIN2B) and solute linked carrier, family 1, member 1 (SLC1A1) were conducted in 31 psychotropic-naïve pediatric OCD patients. The rs1805476 variant of GRIN2B was associated with left but not right orbital frontal cortex (OFC) (p=0.04) and right but not left anterior cingulate cortex (ACC) volume (p=0.02). The SLC1A1 rs3056 variant was associated with increased total (p=0.01), left (p=0.02) and right (p=0.02) thalamic volume. These results suggest that GRIN2B and SLC1A1 may be associated with regional volumetric alterations in OFC, ACC, and thalamus in children with OCD.

The serotonin transporter polymorphisms and major depression following traumatic brain injury.

OBJECTIVE: The purpose of this study was to examine the role of the serotonin transporter gene polymorphisms on the risk of major depression following traumatic brain injury (TBI). METHODS: Seventy-five patients who had sustained a TBI and who met the Diagnostic and Statistical Manual of Mental Disorders (4th ed) (DSM-IV) criteria for mood disorder due to TBI were compared to 99 controls with TBI but no mood disorder. The severity of depression was rated using the Hamilton Depression Rating Scale (HAMD) for the depressed patients. All patients were genotyped for the serotonin transporter gene-linked polymorphic region (5-HTTLPR) with the assay for the rs25531 allelic variant. RESULTS: The distribution of genotype frequencies was not different between the depressed and control groups (chi(2) = 1.43, df = 2, p = 0.488) and for the depressed patients there was no association between HAMD scores and the polymorphisms (t-test = 1.71, df = 68, p = 0.092). CONCLUSION: There was no evidence of association between the serotonin transporter gene polymorphisms and depression post-TBI. Future research is indicated into the possible role of other candidate genes as risk factors for depression in this population.

Serotonin transporter gene and adverse life events in adult ADHD.

Childhood attention deficit hyperactivity disorder (ADHD) symptomatology persists in a substantial proportion of cases into adult life. ADHD is highly heritable but the etiology of ADHD is complex and heterogeneous, involving both genetic and non-genetic factors. In the present article we analyzed the influence of both genetics and adverse life events on severity of ADHD symptoms in 110 adult ADHD patients. Subjects were genotyped for the norepinephrine transporter (NET), the catechol-O-methyltransferase (COMT), the serotonin transporter promoter polymorphism (SERTPR) and the more rare A/G variant within SERTPR. Three main outcomes were obtained: (1) adverse events showed a small but positive correlation with current ADHD severity; (2) NET, COMT and the A/G variant within SERTPR were not associated with ADHD severity; (3) taking into account stressors, the long (L) SERTPR variant showed a mild effect on ADHD, being associated with an increased severity, particularly as regard affective dysregulations; on the other hand, in subjects exposed to early stressors, it showed a protective effect, as compared to the short (S) variant. In conclusion, our data support the role of environmental factors in adult ADHD symptomatology. SERTPR may be involved in some features of the illness and act as a moderator of environmental influences in ADHD.

Association analyses of the DAOA/G30 and D-amino-acid oxidase genes in schizophrenia: further evidence for a role in schizophrenia.

A number of linkage studies have previously implicated the region of chromosome 13q34 in schizophrenia. Chumakov and colleagues (2002) identified a gene complex called G72 (now termed D-amino acid oxidase activator: DAOA)/G30 in this region and performed association analyses of the DAOA/G30 as well as the D-amino-acid oxidase (DAAO) gene with schizophrenia. DAAO oxidizes D-serine, a potent activator of the N-methyl-D-aspartate (NMDA) type glutamate receptor in the human brain whereas the DAOA protein is considered an activator of DAAO. The interaction of these two genes has thus been implicated in the NMDA receptor regulation pathway in schizophrenia. To date, several studies have shown a relatively consistent positive association between schizophrenia and DAOA/G30, but not with DAAO. The aim of our study was to further evaluate the contributions of these genes to the susceptibility to schizophrenia using two different sample sets. Our sample consisted of 168 matched case-control pairs as well as a family-based sample (n=113) for transmission disequilibrium test. Significant associations between the DAOA/G30 M-7 and M-18 polymorphisms and schizophrenia were observed in our case-control sample whereas no associations were observed for DAAO markers. We also observed significant or suggestive transmission disequilibrium for DAOA/G30 M-7, M-23, and M-24 to probands with schizophrenia in our family-based sample. Subsequent analysis of haplotypes made up of four DAOA/G30 markers, one marker selected from each of two linkage disequilibrium blocks that were observed in our sample as well as both ends (M-7 and M-25), were also associated with schizophrenia. Our data provide further evidence that the DAOA/G30 locus may play a role in the pathophysiology of schizophrenia. Although no direct link to genetic polymorphism in these genes and NMDA receptor function has been revealed, the present findings support previous reports implicating DAOA/G30 as susceptibility genes for schizophrenia. Further research is warranted to determine the functional variation underlying these findings and to relate this to the pathophysiology of schizophrenia.

Monoamine oxidase a gene is associated with borderline personality disorder.

OBJECTIVE: Monoamine oxidase A is a mitochondrial enzyme involved in the degradation of certain neurotransmitter amines: serotonin and norepinephrine. As for its role in aggression, impulsivity, suicide and mood liability, monoamine oxidase A can be considered a functional candidate in borderline personality disorder. METHODS: To test for this hypothesis we genotyped two polymorphic markers in monoamine oxidase A gene, a promoter VNTR and an rs6323 (T941G) in exon 8, in 111 Caucasian borderline personality disorder patients and 289 Caucasian healthy controls. Association analyses using individual marker and haplotype data were performed by a program of COCAPHASE in UNPHASED (MRC Human Genome Mapping Project Resource Centre, Cambridge, UK). RESULTS: We found that the borderline personality disorder patients had a high frequency of the high activity VNTR alleles (chi=4.696, P=0.03) and a low frequency of the low activity haplotype (chi=5.089, P=0.02). CONCLUSION: These results show that the monoamine oxidase A gene may play an important role in the etiological development of the borderline personality disorder.

Further evidence of MAO-A gene variants associated with bipolar disorder.

The aim of this study was to investigate MAOA gene variants in bipolar disorder by using a family-based association approach. The first sample included 331 nuclear families from Western and Central Canada with at least 1 offspring affected with bipolar disorder comprising a total of 1,044 individuals. All subjects were genotyped for MAOA-941T > G and -uVNTR gene variants using PCR techniques. Haplotype TDT was statistically significant (LRS = 12.17; df = 3; P = 0.0068; permutation global significance = 0.00098), with the T-4 haplotype significantly associated with bipolar disorder (OR = 1.63, 95% CI = 1.11-2.37). Single marker analysis evidenced a borderline association for MAOA-941T > G (P = 0.04), but not for the uVNTR. Pooling the Canadian sample with a second previously reported Italian sample genotyped for the uVNTR variant, negative results were obtained as well. No different results were detected when analyzing female subjects separately. In conclusion, our family-based association study gives mild but further support of the involvement of MAOA variants in bipolar disorder.

Brain-derived neurotrophic factor (BDNF) gene and rapid-cycling bipolar disorder: family-based association study.

BACKGROUND: We have previously reported the Val66Met and GT(n) repeat polymorphisms of the brain-derived neurotrophic factor (BDNF) gene to be associated with bipolar disorder. However, these findings have not been replicated consistently. AIMS: To dissect the association of the BDNF gene with bipolar disorder by examining additional markers at the DNA level and by testing the illness categories of bipolar disorder I and II and rapid cycling. METHOD: We performed a family-based association study and haplotype analyses with 312 nuclear families using four single nucleotide polymorphisms (SNPs) and the Val66Met and GT(n) repeat polymorphisms. RESULTS: The SNPs hCV11592756 and rs2049045, the Val66Met and GT(n) were significantly associated with bipolar disorder using transmission disequilibrium analyses (P=0.02, 0.009, 0.001 and 0.008 respectively). The effect atthese markers was mainly driven by the rapid-cycling patients. CONCLUSIONS: Within bipolar disorder, variation in the BDNF gene appears to predict risk for developing rapid cycling according to DSM-IV. Incorporating this clinical sub-phenotyping into other studies of the BDNF gene may help to resolve some of the inconsistencies reported thus far concerning BDNF and bipolar disorder.

Serotonin 2A receptor gene is associated with personality traits, but not to disorder, in patients with borderline personality disorder.

Borderline personality disorder (BPD) is a chronic, disabling, and high-risk mental disorder characterized by a pervasive pattern of instability in regulation of emotion, interpersonal relationships, self-image, and impulse control beginning in early adulthood. BPD affects about 1%-2% of the general population and has a high mortality rate as a result of suicide and impulsive behaviour. The serotonin 2A receptor gene (HTR2A) is considered a candidate gene for BPD because multiple lines of evidence suggest that it plays an important role in suicide, impulsivity and emotional liability. To test for an association between HTR2A and BPD, we genotyped four polymorphisms, rs6313 (T102C), rs4941573, rs2296972 and rs6314 (His452Tyr), in 111 Caucasian patients with BPD and 287 Caucasian healthy controls. The program UNPHASED was used to compare allele and haplotype frequencies between cases and controls. We did not find a significant association between HTR2A and BPD based on allele, genotype or haplotype analyses. However, there were significant associations between HTR2A and personality traits in the BPD patients. The C allele of rs6313 and the A allele of rs4941573 associated with a higher Extraversion score. Our results suggest that the serotonin 2A receptor gene may not play a major role in the aetiology of borderline personality disorder, but may have a role in personality traits.

Glutamate transporter gene SLC1A1 associated with obsessive-compulsive disorder.

CONTEXT: There is strong evidence from family and twin studies that genetic determinants play an important role in the etiology of obsessive-compulsive disorder (OCD). In the only genome scan of OCD to date that we are aware of, suggestive linkage was reported to the chromosomal region 9p24, a finding that was subsequently replicated. This region contains the gene encoding the neuronal glutamate transporter, SLC1A1. SLC1A1 represents an excellent candidate gene for OCD based on evidence from neuroimaging and animal studies that altered glutamatergic neurotransmission is implicated in the pathogenesis of this disorder. OBJECTIVE: To determine whether sequence variants in SLC1A1 are associated with transmission of the OCD trait. DESIGN: A family-based candidate gene association study. SETTING: A specialized anxiety disorders outpatient clinic. PARTICIPANTS: One hundred fifty-seven white probands with DSM-IV OCD recruited from consecutive referrals and their first-degree relatives (476 individuals in total). INTERVENTION: Nine single nucleotide polymorphisms spanning SLC1A1 were genotyped. Single-locus and haplotype analyses were performed using the Family-Based Association Test and the Transmission Disequilibrium Test. Traits examined included DSM-IV OCD diagnosis and highest lifetime symptom severity as measured using the Yale-Brown Obsessive-Compulsive Scale. Correction for multiple comparisons was performed using permutation tests. RESULTS: After correction for multiple comparisons, 2 variants, rs301434 (chi 2 = 12.04; P = .006) and rs301435 (chi 2 = 9.24; P = .03), located within a single haplotype block were found to be associated with transmission of OCD. Furthermore, a specific 2-marker haplotype within this block was significantly associated with OCD (chi 2 = 12.60; P = .005). This haplotype association was statistically significant in transmissions to male but not female offspring. CONCLUSIONS: Although requiring replication in larger samples, these findings provide preliminary evidence that sequence variation in SLC1A1 is associated with susceptibility to OCD, particularly in males. Furthermore, these results provide support for the role of altered glutamatergic neurotransmission in the pathogenesis of OCD.

Association between serotonin transporter gene and borderline personality disorder.

Borderline personality disorder (BPD) is characterized by a pervasive pattern of instability in regulation of emotion, interpersonal relationships, self-image, and impulse control beginning in early adulthood. BPD affects about 1-2% of the general population and has a high mortality rate as a result of suicide and impulsive behaviour. The serotonin transporter gene (5-HTT) is considered as a candidate gene for BPD as multiple lines of evidence have suggested that it plays an important role in suicide, impulsive behaviour, and emotional liability. To test for an association between 5-HTT and BPD, we genotyped three common polymorphisms: the serotonin transporter linked promoter region (5-HTTLPR); a variable number of tandem repeat (VNTR) in intron 2, and a single nucleotide variant (A/G) within the LPR region. Eighty-nine Caucasian patients with BPD and 269 Caucasian healthy controls were analyzed. The program UNPHASED was used to compare allele and haplotype frequencies between cases and controls. Significant differences in allele frequencies of the VNTR marker (p=0.012) and haplotype frequencies (p=0.002) between patients and controls were found. Compared with healthy controls, patients with BPD showed higher frequencies of the 10 repeat of the VNTR marker and the S-10 haplotype, and lower 12 repeat and L(A)-12 haplotype. Our results suggest that the serotonin transporter gene may play a role in the aetiology of borderline personality disorder.

Suggestive association between the C825T polymorphism of the G-protein beta3 subunit gene (GNB3) and clinical improvement with antipsychotics in schizophrenia.

G-proteins are composed of alpha, beta and gamma subunits. Once activated, these subunits play a major role in the conversion of external receptor activation into intracellular signals. The functional C825T polymorphism of the beta3 subunit gene (GNB3) has recently been shown to modulate antidepressant response, with the T-allele conferring an increased signaling and being associated with favorable antidepressant response. We hypothesized that this polymorphism may be associated with response to antipsychotics in a population of 145 chronic schizophrenic patients deriving from two study-samples and being mainly treated with clozapine for up to 6 months. Overall, the C/C genotype was significantly associated with relative clinical improvement as measured by Brief Psychiatric Rating Scale (BPRS) change scores after 6 and 12 weeks (p<0.01 and p=0.03, respectively), with estimated effect sizes ranging from 4.8 to 7%. Our results further suggest that this effect is only attributable to Caucasians when compared to African-Americans. Moreover, our findings point to the role of intracellular mechanisms in antipsychotic response.

Gene-gene interaction between MAOA and COMT in suicidal behavior.

Several lines of evidence suggest that suicidal behavior is associated with altered noradrenergic neurotransmission. Noradrenaline (NA) is catabolized by monoamine oxidase A (MAOA) and cathecol-O-methyl transferase (COMT). We hypothesized that the genes encoding MAOA and COMT might contain genetic variation conferring increased risk for attempted suicide. In order to test this hypothesis, we genotyped the 941T > G and the promoter VNTR polymorphisms in the MAOA gene and the Val 108/158 Met COMT polymorphism in 305 families with at least one member having bipolar disorder (BD). No association with history of suicide attempt was found either in the MAOA polymorphisms (VNTR:LRS = 1.90, d.f. = 1, p = 0.16; 941T > G:LRS = 1.39, d.f. = 1, p = 0.23), or with the Val 158 Met polymorphism (LRS = 1.61, d.f.=1, p = 0.20). When we performed the haplotype analysis for MAOA gene, we found no association between suicide attempt and haplotype distribution (LRS = 3.07, d.f. = 2, p = 0.21). As both genes are involved in degrading noradreanline, we also tested the hypothesis of epistasis between MAOA polymorphisms and Val158Met, however, no additive effect was found in conferring risk for suicide attempt. These findings suggest that MAOA and COMT genes may not influence suicidal behavior in patients with bipolar disorder.

The SNAP-25 gene may be associated with clinical response and weight gain in antipsychotic treatment of schizophrenia.

The synaptosomal-associated protein of 25 kDa (SNAP-25) is an essential component of the core complex that mediates presynaptic vesicle trafficking. Thus, SNAP-25 is directly involved in the release of neurotransmitters. Quantitative alterations of SNAP-25 expression have been reported in brain regions and cerebrospinal fluid (CSF) of schizophrenics and in haloperidol treated rats. This observed altered expression may be influenced by genetic variants of SNAP-25. We hypothesized that polymorphisms of the SNAP-25 gene (sites DdeI, MnlI and TaiI in the 3'UTR) are associated with antipsychotic drug response and induced weight gain. A sample of 59 patients with prior suboptimal response to antipsychotic treatment and diagnosed with DSM-IV schizophrenia or schizoaffective disorder was examined. Patients were administered clozapine, haloperidol, olanzapine or risperidone for up to 14 weeks. Clinical response was defined as the difference between the baseline and the endpoint total scores on the Positive and Negative Syndrome Scale (PANSS). Weight was assessed at baseline and at study endpoint. ANOVA revealed that the MnlI and TaiI polymorphisms were associated with response (F[2,53] = 4.57, p = 0.01 and F[2,52] = 3.53, p = 0.03) and with weight gain (F[2,52] = 4.28, p = 0.01 and F[2,51] = 3.38, p = 0.04). When covariates were included, the MnlI polymorphism remained significantly associated with changes of PANSS scores, but not with weight gain. The DdeI polymorphism was not associated with response or weight gain. These findings suggest that SNAP-25 gene variants affect clinical response in patients with prior poor response to antipsychotics. Weight changes do not seem to be associated with polymorphism of the SNAP-25 gene, however, replication in independent samples is warranted.