Stefanie Behrens

Identification of a Naturally Occurring Polymorphism in the Promoter Region of the Norepinephrine Transporter and Analysis in Major Depression

Disturbances in the noradrenergic neurotransmission system have been implicated in the etiology of mood disorders. The norepinephrine transporter (NET) is a main target of antidepressant action and was shown to be dysregulated in major depression. Despite the clinical and physiological significance of NET gene regulation, little is known about the transcriptional control mechanisms governing its expression. Since it is well established that affective disorders have a genetic component with many genes of small effect contributing to the genetic susceptibility of depression, the NET gene is an interesting candidate gene for affective disorders. In a search for polymorphisms or mutations in the 5′ flanging region of the NET gene we sequenced approximately 1000 bp upstream of the first codon in the NET gene promoter in 100 patients with major depression and 100 healthy controls. We identified a so far unknown T → C polymorphism 182 bp upstream of the start codon in a transcriptional relevant region. In a case control association study we investigated the newly identified T-182C polymorphism and an already known G1287A polymorphism in exon 9 of the NET gene in a sample of 193 patients with major depression and 136 healthy, non-related controls. No statistical significant differences between patients and controls were found for any of the analyzed polymorphisms, either in the genotype distribution or in the allele frequencies. Our results suggest that the investigated polymorphisms are not major susceptibility factors in the etiology of major depression.

Serotonin transporter gene regulatory region polymorphism (5-HTTLPR), [3H]paroxetine binding in healthy control subjects and alcohol-dependent patients and their relationships to impulsivity

The aim of this study was to investigate [3H]paroxetine binding and impulsivity in alcohol-dependent and age-matched control subjects in relation to a 5-promoter region serotonin transporter (5-HTT) polymorphism (5-HTTLPR). Alcohol-dependent subjects were hypothesized to show a decreased number of bindings sites and a lower dissociation constant. 5-HTTLPR S-genotype carriers in both alcohol-dependent and control subjects were expected to show significantly fewer binding sites and a lower dissociation constant. Influences of impulsive traits, chronic daily alcohol intake, duration of alcohol dependence, age of onset and age on [3H]paroxetine binding were also investigated. Inpatients meeting DSM IV alcohol dependence criteria and of German descent were recruited to avoid ethnic stratification effects. One hundred and seventeen control subjects of similar social status were recruited from a town community. Blood samples were taken from both alcohol-dependent and control subjects to determine 5-HTTLPR genotypes using PCR of lymphocyte DNA, and to perform platelet [3H]paroxetine binding (binding capacity: B(max); and dissociation constant: K(D)). Impulsivity was assessed using the Barratt impulsiveness scale version 5 (BIS-5) in alcohol-dependent subjects only. Alcohol-dependent subjects were subdivided into low or high impulsivity groups using a median-split of the BIS-5 scale. The control group was slightly older than the alcohol-dependent group (not statistically significant). [3H]paroxetine binding was investigated in 72 control subjects and 72 patients, of which five patients met type 2 alcohol dependence criteria. Genotyping was carried out in all patients and control subjects. A significant influence of duration of alcohol dependence was found on the [3H]paroxetine binding K(D) but not B(max.) Neither alcohol-dependent nor control subjects showed any differences in B(max) or K(D). S-allele carriers did not show a decreased binding or lower dissociation constant. Furthermore, no significant interaction between B(max) and K(D) with either 5-HTTLPR genotype or impulsivity was revealed. This was the first study to investigate platelet [3H]paroxetine binding in alcohol-dependent and age-matched control subjects in relation to the 5-HTTLPR genotype. No differences concerning 5-HTTLPR-alleles were found in these groups Furthermore, no significant interaction between these parameters and impulsivity was shown in alcohol-dependent subjects. These results do not support previous results of altered [3H]paroxetine binding sites in alcohol-dependent subjects or 5-HTTLPR S-allele carriers. K(D) might be influenced by duration of alcohol dependence, but not sufficiently to yield differences between alcohol-dependent and control subjects.

Beta-1-adrenergic receptor gene in major depression: influence on antidepressant treatment response.

Noradrenergic dysfunction has been implicated in the development of affective disorders. β‐adrenergic receptors (βARs) mediate the response to norephinephrine, are coupled to the cAMP signaling cascade, supposed to be altered in their density and/or sensitivity in depression, and down regulated in several brain regions after long term treatment with different but not all antidepressants. A recently identified functional polymorphism in the β1‐adrenergic receptor (G1165C) leading to the amino acid variation Gly389Arg was associated with an enhanced coupling to the stimulatory Gs‐protein and increased adenylyl cyclase activation, disturbances which are often observed in affective disorders. Therefore, we investigated whether this β1AR polymorphism is associated with major depression or with the response to antidepressant treatment in a sample of 259 patients compared to 206 healthy controls. Although we could not detect an association between the β1AR polymorphism and major depression we found a tendency for a relation between CC homozygosity and a better and even faster response to antidepressant treatment in those patients, which were treated with antidepressants affecting directly or indirectly the β1AR system (tricyclic antidepressants, noradrenergic and serotonergic specific agents, selective noradrenaline reuptake inhibitors) determined by the HAMD and CGI score (Pu2009=u20090.05). However, after correction for multiple testing (Bonferroni) these results did not remain significant. Nevertheless, these findings suggest that the presence of the C allele might be an indicator for antidepressant treatment response.

The dysbindin gene in major depression: an association study.

The pathophysiological mechanisms, as well as the molecular loci of antidepressant drug action have not yet been established, but recent models proposed that several adaptive mechanisms in signal transduction cascades beyond the receptor and reuptake systems are involved in antidepressant action and play an important role in the etiology of affective disorders. In this context, the dysbindin gene (dystrobrevin‐binding‐protein 1, DTNBP1), which was recently reported to be associated with schizophrenia seems to be an interesting candidate gene for affective disorders. Dysbindin is widely expressed in the human brain and binds to the dystrophin‐associated protein complex (DPC) which appears to be involved in signal transduction pathways, which have been repeatedly investigated and described as altered or disturbed in affective disorders [McLeod et al. [2003: Psychopharmacol Bull 35:24–41]; Brambilla et al. [ 2003 : Mol Psychiatry 8:721–737]]. Therefore, we investigated whether five SNPs in the dysbindin gene could be susceptibility factors in the ethiology of major depression or for the response to antidepressant treatment in a sample of 293 patients compared to 220 healthy controls. Applying single SNP evaluation, as well as haplotype analysis we could not detect an association between the dysbindin polymorphisms and major depression or the response to antidepressant treatment. In conclusion, our results suggest that SNPs in the dysbindin gene are unlikely to play a major role in the pathophysiology of major depression or are in linkage disequilibrium (LD) with a neighboring mutation or gene. Further analysis are needed to confirm these results.

Analysis of polymorphisms in the olfactory G-protein Golf in major depression.

It is well established that G-proteins represent essential regulatory components in transmembrane signaling. The α subunit of the olfactory G-protein Golf (GNAL) maps to a region on chromosome 18 where linkage to affective disorders has been reported, as well as a parent-of-origin effect in affective disorders with some markers near the locus for the α subunit of the Golf gene. We investigated whether two polymorphisms in the α subunit of the Golf gene (A→G in intron 3, and T→G in intron 10) are associated with major depression in 176 major depressive patients compared with 145 healthy control subjects, and additionally tested for a parent-of-origin effect in separated gender groups. In the control group, we found a significant increase in the G-allele frequency of the intron 3 polymorphism in females (P =0.0036, odds ratio=2.13, 95% confidence interval=1.29–3.54, Fishers Exact Test). In patients, we found a similar tendency for higher G-allele frequencies in females. Concerning the intron 10 polymorphism, no differences in the genotype or allele frequencies were detectable for any of the separated gender groups. Also, the total patient and control groups showed no differences in allele or genotype frequencies for any of the investigated polymorphisms. The results of this study agree with the reported parent-of-origin effects on chromosome 18, but do not support the hypothesis that the Golf gene is a major susceptibility factor for major depression.

Polymorphisms in the α-2 macroglobulin gene in psychogeriatric patients

Recent reports have suggested that genetic polymorphisms in the alpha-2 macroglobulin (A2M) gene are associated with an increased risk for Alzheimers disease. In the present study we tested two polymorphisms in the alpha-2 macroglobulin gene, a 5 bp deletion at the 5 splice site of exon 18 and a G/A point mutation (V1000I) in exon 24, in a sample of 118 healthy, non demented controls and 238 consecutively recruited gerontopsychiatric patients, diagnosed as: Alzheimers disease (N=88), mild cognitive impairment (N=32), subjective cognitive complaints (N=54) and depression/other psychiatric disorders (N=64). The aim of this study was to test whether the investigated polymorphisms has a high enough selectivity and specificity to distinguish between the different gerontopsychiatric disorders or to differentiate genetically AD from other forms of dementia, respectively. Also a possible relation to the APOE varepsilon4 polymorphism was examined. Our study failed to show an association between the two investigated polymorphisms in the alpha-2 macroglobulin gene and any of the four different psychogeriatric patient subgroups, either alone or in combination with the APOE varepsilon4 genotype.

Analysis of polymorphisms in the α-subunit of the olfactory G-protein Golf in lithium-treated bipolar patients

Objective This study examines the &agr;‐subunit of the olfactory G‐protein (Golf) as a possible candidate gene for bipolar disorder. The &agr;‐subunit of the Golf gene maps to a region on chromosome 18p that has been implicated in several linkage studies as a potential site of a bipolar disorder susceptibility loci. Methods We investigated whether two polymorphisms in the &agr;‐subunit of the Golf gene (A→G in intron 3 and T→G in intron 10) are associated with bipolar disorder in a sample of 149 bipolar patients under lithium treatment compared with 139 healthy controls using haplotype analysis. Results There was no evidence for an association between the investigated polymorphisms in the Golf gene and bipolar disorders, as well as to response to lithium treatment or common side effects, like hand tremor, weight gain and cognitive dysfunction. Conclusion The results of the present study do not support the hypothesis that the Golf gene is a major susceptibility factor for bipolar disorders.

Polymorphisms in the apolipoprotein E (APOE) gene in gerontopsychiatric patients

Abstract Two recently described polymorphisms in the promoter region of the apolipoprotein E (APOE), the −491A7T and Th1/E47csT/G polymorphism, have been suggested to be associated with an increased risk for Alzheimers disease (AD) independent from the APOE ɛ4 carrier status. We studied the association between the APOE ɛ4 polymorphism and the −491A/T and Th1E47csT/G polymorphisms in a sample of 118 healthy, non-demented controls and 239 consecutively recruited gerontopsychiatric patients diagnosed as: Alzheimers disease (N = 89), age mild cognitive impairment (N = 32), memory complainers without any congitive deficit (N = 54) and depression/other psychiatric disorders (N = 64), to test whether the investigated polymorphisms have a high enough selectivity and specificity to distinguish between the different gerontopsychiatric disorders to differentiate AD genetically from other forms of dementia, respectively. Also a possible association with the APOE ɛ4 polymorphism was examined. We found a statistically significant association between the APOE ɛ4 allele and Alzheimers disease (p = 0.0001) and age associated memory impairment (p = 0.006). Our study failed to show an association between the promoter polymorphisms −491A/T and Th1E47csT/G in the APOE gene and gerontopsychiatric disorders either alone or in relationship to the APOE ɛ4 polymorphism. However, if we combine our results with three previous published positive reports there seems to be an association between the −491A/T polymorphism and AD, though its size is less than found in the original publication.