Association of major depression with rare functional variants in norepinephrine transporter and serotonin1A receptor genes.код для вставкиСкачать
BRIEF RESEARCH COMMUNICATION Neuropsychiatric Genetics Association of Major Depression With Rare Functional Variants in Norepinephrine Transporter and Serotonin1A Receptor Genes Britta Haenisch,1 Karoline Linsel,1 Michael Br€uss,1 Ralf Gilsbach,1,2 Peter Propping,3 Markus M. N€othen,3 Marcella Rietschel,4,5 Rolf Fimmers,6 Wolfgang Maier,4 Astrid Zobel,4 Susanne H€ofels,4 Vera Guttenthaler,4 Manfred G€othert,1 and Heinz B€onisch1* 1 Institute of Pharmacology and Toxicology, University of Bonn, Bonn, Germany 2 Institute of Experimental and Clinical Pharmacology, University of Freiburg, Freiburg, Germany Institute of Human Genetics, University of Bonn, Bonn, Germany 3 4 Department of Psychiatry, University of Bonn, Bonn, Germany 5 Central Institute of Mental Health, Mannheim, Germany Institute of Medical Biometry, Informatics and Epidemiology, University of Bonn, Bonn, Germany 6 Received 28 April 2008; Accepted 12 November 2008 Dysregulations of central noradrenergic and serotonergic neurotransmission have been suggested to contribute to the pathogenesis of neuropsychiatric disorders such as depression. The norepinephrine transporter (NET; SLC6A2) and the serotonin (5-HT)1A receptor (5-HT1A receptor; HTR1A) play an important role in central nervous monoaminergic homeostasis. As shown previously, variations in the human NET and 5-HT1A receptor genes can alter noradrenergic and serotonergic signaling in the brain: a single nucleotide polymorphism (SNP) in the coding region of the NET gene resulting in a F528C substitution increased plasma membrane expression of this NET variant, and a SNP in the human 5-HT1A receptor gene leading to the R219L receptor variant almost abolished cellular signal transduction subsequent to receptor activation. The present study aimed at investigating whether these NET and 5-HT1A receptor variants are associated with major depression (MD). The sample comprised 426 patients suffering from unipolar MD as well as 643 healthy control subjects for the variants of the 5-HT1A receptor and the NET. Both SNPs were shown to be associated with MD. In conclusion, our results favor the hypothesis that monoaminergic neurotransmission in general and the F528C NET and R219L 5HT1A receptor variants in particular are involved in the pathogenesis of depression. 2008 Wiley-Liss, Inc. Key words: norepinephrine transporter; 5-HT1A receptor; unipolar depression; association analysis; single nucleotide polymorphism Major depression (MD) is a common and debilitating psychiatric illness with a lifetime prevalence of up to 20%. Despite the limited knowledge about the etiology and pathogenesis of MD, effective antidepressant drugs are available. The ability of most of the clinically used antidepressants (AD) to enhance noradrenergic 2008 Wiley-Liss, Inc. How to Cite this Article: Haenisch B, Linsel K, Br€ uss M, Gilsbach R, Propping P, N€ othen MM, Rietschel M, Fimmers R, Maier W, Zobel A, H€ ofels S, Guttenthaler V, G€ othert M, B€ onisch H. 2009. Association of Major Depression With Rare Functional Variants in Norepinephrine Transporter and Serotonin1A Receptor Genes. Am J Med Genet Part B 150B:1013–1016. and/or serotonergic neurotransmission by inhibiting the respective neurotransmitter inactivation (mainly by blockade of the corresponding reuptake transporter) was the basis for the classical monoamine hypothesis of depression [Schildkraut, 1965; Coppen, 1967]. According to this more than 40 years old concept, depression was suggested to be due to a deficiency of central noradrenergic and/ or serotonergic neurotransmission and the ADs mentioned above would compensate for this deficiency by enhancing neurotransmission. An alternative therapeutic measure would be a direct Britta Haenisch and Karoline Linsel contributed equally to this work. Grant sponsor: Deutsche Forschungsgemeinschaft; Grant sponsor: BONFOR. *Correspondence to: Heinz B€ onisch, Institute of Pharmacology and Toxicology, University of Bonn, Reuterstrasse 2b, 53113 Bonn, Germany. E-mail: email@example.com Published online 22 December 2008 in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/ajmg.b.30912 1013 1014 stimulation of the neurotransmitter receptor which is the target of the respective synaptic transmission. Although the monoamine hypothesis of depression fails to explain the delayed onset of the antidepressant effect, this hypothesis is still an important basis for research in the field of MD. Thus, based on this hypothesis functionally significant single nucleotide polymorphisms (SNPs) in the genes of relevant neurotransmitter transporters and/or receptors may contribute to the pathogenesis of MD. The present article is focused on the norepinephrine (NE) transporter (NET; SLC6A2) and the serotonin (5-HT)1A receptor (5-HT1A receptor; HTR1A) which play an important role in CNS noradrenergic and serotonergic signaling, respectively. The NET mediates rapid re-uptake of released NE into noradrenergic neurons [B€ onisch and Br€ uss, 2006]. It is one of the main targets of important ADs (e.g., reboxetine) causing an elevation of synaptic NE. In the NET gene a naturally occurring, non-synonymous SNP has been identified [Halushka et al., 1999] resulting in the F528C NET variant. This variant displays an increased plasma membrane expression associated with increased NE uptake compared to the wild-type NET [Hahn et al., 2005]. Accordingly, this variant may be expected to lead to decreased levels of NE in the synaptic cleft. Thus, this functional variant may be involved in the pathogenesis of depression, while our previous study on other NET missense variants did not show any association with major psychiatric disorders [St€ ober et al., 1996]. 5-HT1A receptors coupled to Gi/Go proteins occur both in the somadendritic area of the serotonergic neurons in the raphe nuclei where they act as autoreceptors, and on non-serotonergic neurons of the forebrain where they are expressed as somadendritic postsynaptic receptors. Inhibitory 5-HT1A receptors on the cell bodies and/or synaptic boutons of inhibitory GABAergic interneurons impinge on noradrenergic nerves. Thus, activation of these receptors is indirectly involved in facilitation of NE release in the hippocampus and cerebral cortex [Fink and G€ othert, 2007]. Several lines of evidence suggest that not only the NET but also the 5-HT1A receptor is involved in the pathogenesis of anxiety and depression [Hamon, 1997; Strobel et al., 2003]. For example, in patients suffering from depression ligand binding to 5-HT1A receptors measured by positron emission tomography was reduced in cortical regions and in the midbrain raphe [Drevets et al., 1999; Sargent et al., 2000]. As in the case of the NET gene, several SNPs have been found in the coding region of the 5-HT1A receptor gene [see, e.g., G€ othert et al., 2001]. Among them was a SNP resulting in the R219L 5-HT1A receptor variant. Expression of this variant which was first identified in a Tourette0 s syndrome patient [Lam et al., 1996] almost abolished cellular signal transduction subsequent to receptor activation [Br€ uss et al., 2005]. On the basis of the data summarized here, it was conceivable that the R219L 5-HT1A receptor variant may also play a role in the pathogenesis of depression. Taken together, the aim of the present study was to investigate whether genetic variation in two main targets of central monoamine homeostasis, the NET and the 5-HT1A receptor, may contribute to the development of MD. To obtain a hint for this hypothesis, we determined the allele frequency of the F528C NET and R219L 5-HT1A receptor variants in patients with MD and in healthy controls. AMERICAN JOURNAL OF MEDICAL GENETICS PART B The present study included 426 patients with unipolar affective disorder (68% women and 32% men, mean age of 49.26 13.40) comprising 14 individuals with dysthymic disorder, and 643 healthy control subjects (54% women and 46% men, mean age of 43.67 13.92). Within the MD sample, 339 patients suffered from unipolar recurrent disorder, and 87 from unipolar single episode disorder. The average age of onset was 36.37 13.36 for women and 37.99 13.36 for men (for further details, see Table I). All subjects were of German descent. Patients were systematically recruited from consecutive admissions to the Department of Psychiatry at the University of Bonn. Lifetime consensus diagnosis according to DSM-IV criteria was based on multiple sources of information including a personal structured interview [SCID I; First et al., 1997], medical records, and the family history method. Best estimate diagnoses were obtained by at least two experienced psychiatrists/psychologists. Comorbidities were recorded as DSM-IV Axis I diagnosis and are presented in Table II. Control individuals were questioned for a history of psychiatric disorder. Four control individuals had a history of MD and were excluded from the analysis. The study was approved by the ethical review board of the Medical Faculty at the University of Bonn. Genotyping was carried out by employing 50 nuclease assays with fluorescent allele-specific TaqMan probes. We used Custom TaqMan SNP Genotyping Assays (Applied Biosystems, Foster City, CA) for each SNP. The probes used in the bi-allelic system were synthesized with the fluorescent reporter dye FAM (6-carboxyfluorescein) or VIC attached to the 50 end and a NFQ (non-fluorescent quencher) at the 30 end. Allelic discrimination was assayed on a Mx3000P real-time cycler (Stratagene, Amsterdam, the Netherlands). Each assay included negative controls (no-template controls) and positive controls (allele 1 or 2 controls). Genotype frequencies for cases and controls were in Hardy–Weinberg equilibrium. To determine the significance of the genotype distribution, we used the two-tailed Fisher’s exact test. The results of our study are documented in Table III. Both variants are relatively rare, with allele frequencies of 0.3% and 0.2% in the general population and 1.2% and 1.1% in patients for the F528C NET and R219L 5-HT1A receptor variant, respectively. Both variants show significant association with MD (P ¼ 0.017 and 0.024; OR ¼ 4.6 and 3.8; 95% confidence intervals 1.2–17.1 and 1.2–12.3). Logistic regression analysis was used to check for the influence of sex and age. Though we found clear sex and age effects in the combined case and control sample, there was no evidence for an interaction between age and genetic factors as well as between sex TABLE I. Age of Onset in the MD Sample (n ¼ 416) Age of onset <15 15–25 26–35 36–45 46–55 56–65 >65 Women (n ¼ 281) 5 (1.8%) 61 (21.7%) 79 (28.1%) 63 (22.4%) 47 (16.7%) 21 (7.5%) 5 (1.8%) Men (n ¼ 135) 0 (0%) 26 (19.3%) 40 (29.6%) 30 (22.2%) 18 (13.3%) 20 (14.8%) 1 (0.7%) HAENISCH ET AL. 1015 TABLE II. Comorbidities in the MD Sample: 149 of 426 Patients Showed Comorbidities Diagnosis Anxiety disorder Anxiety disorder (not otherwise specified) Panic disorder without agoraphobia Panic disorder with agoraphobia Agoraphobia without history of panic disorder Social phobia Specific phobia Obsessive-compulsive disorder Substance abuse/dependence Alcohol abuse/dependence Sedative-, hypnotic- or anxiolytic abuse/dependence Cannabis abuse/dependence Eating disorder Anorexia nervosa Bulimia nervosa Somatization disorder Somatoform disorder (not otherwise specified) Body dysmorphic disorder Pain disorder associated with psychological factors Pain disorder associated with both psychological factors and a general medical condition and genetic factors with respect to the development of MD. The impact of the genetic factors in logistic modeling with age and sex as covariates (no interaction assumed) was comparable to the results in Table III. These findings are in line with the hypothesis that both variants are involved in the pathogenesis of depression—a contention which is supported by additional findings reported in the literature. (1) As already mentioned, the F528C NET variant is expressed at increased density in the plasma membrane leading to increased NE uptake [Hahn et al., 2005]. This, in turn, may be assumed to result in a decreased NE concentration in the synaptic cleft and at the adrenoceptors in the respective synapses—a finding which conforms to the monoamine hypothesis of depression. (2) This conclusion is also in line with the observation that the serotonin transporter, which is closely related to the NET, is in a hyperfunctional state during depression in seasonal affective disorder [Willeit et al., 2008]. (3) A further mechanism potentially underlying the involvement of the F528C NET variant in the pathogenesis of MD is n 1 38 39 18 12 11 13 20 9 7 3 5 5 3 2 5 the insensitivity of this variant to regulation by protein kinase C (PKC)-linked pathways [Hahn et al., 2005]. PKC-mediated downregulation (internalization) of the wild-type NET can be induced through stimulation of Gq-coupled receptor such as muscarinic receptors co-located with the NET in the neuronal plasma membrane [Apparsundaram et al., 1998]. The F528C NET variant may be insensitive to physiological down-regulation, and this may contribute to sustained overactivity of this NET variant and thus the severity of depression. Furthermore, the F528C NET variant has been shown to be eightfold less sensitive to inhibition by the NETselective tricyclic antidepressant desipramine [Hahn et al., 2005]. This, in turn, may contribute to partial resistance to treatment with NET-selective antidepressants of patients expressing this NET gene variant. Likewise, the suggestion that the 5-HT1A receptor is involved in the pathogenesis of MD, derived from the association between the R219L 5-HT1A receptor variant and MD, is in line with data reported in the literature. (1) The position of the SNP and the TABLE III. Allele and Genotype Distribution of Two Non-Synonymous SNPs Within the Coding Regions of the SLC6A2 and HTR1A Genes Among MD Patients and Control Subjects Genotype distribution Gene (protein) SLC6A2(NET) HTR1A (5-HT1AR) a refSNP ID rs5558 Nucleotide exchangea T1583G Amino acid exchange F528C rs1800044 G659T R219L Sample size MD (n ¼ 426) Controls (n ¼ 643) MD (n ¼ 426) Controls (n ¼ 643) var/var 0 (0.000) 0 (0.000) 0 (0.000) 0 (0.000) Second allele is the rare allele. Fisher’s exact test (allele based); both test results remain significant even after applying Bonferroni correction. Allelic odds ratio with confidence intervals. b c var/wt 9 (0.021) 3 (0.005) 10 (0.023) 4 (0.006) wt/wt 417 (0.979) 640 (0.995) 416 (0.977) 639 (0.994) P-value* OR** [CI] 0.017 4.6 [1.2–17.1] 0.024 3.8 [1.2–12.3] 1016 replaced amino acid in the R219L variant is critical for the function of the receptor since the R219L 5-HT1A receptor variant exhibited an almost complete abolition of cellular signal transduction subsequent to receptor stimulation [Br€ uss et al., 2005]. (2) Downregulation and reduced responsiveness of 5-HT1A receptors have been found in patients suffering from MD [Sargent et al., 2000; Lesch et al., 2003]. (3) 5-HT1A receptor agonists such as ipsapirone, gepirone, and other azapirones have been developed and investigated as potential antidepressant drugs but, in spite of the widespread recognition of their clinical efficiency, their introduction into the clinic has been hampered by their undesirable pharmacokinetic properties [Blier and Ward, 2003]. In support of an antidepressant effect, long-term treatment of rats with such compounds resulted in desensitization of the somadendritic 5-HT1A autoreceptors; this, in turn, leads to an increase in 5-HT release [Hamon 1997]. Blockade of the inhibitory somadendritic 5-HT1A autoreceptors resulting in acceleration of effects of antidepressant drugs by enhancement of 5-HT release is (one of) the mechanism(s) underlying the use of the b-adrenoceptor/5-HT1A/1B receptor antagonist pindolol for adjunct treatment of MD [Artigas et al., 2001; Celada et al., 2004]. (4) Stimulation of 5-HT1A receptors on GABAergic interneurons innervating noradrenergic neurons increases NE release in the hippocampus and cerebral cortex by inhibiting the release of the inhibitory neurotransmitter GABA [Fink and G€ othert, 2007]. The increase in 5-HT and NE release as potential therapeutic mechanisms conforms to the monoamine hypothesis of depression. 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