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Functional promoter and polyadenylation site mapping of the human serotonin (5-HT) transporter gene
Abstract
We have isolated and characterized the 5'-flanking region and the proximal polyadenylation site of the human 5-HT transporter gene. The major gene transcript is 2,793 bp in length and it contains 208 bp of 5'-untranslated region (5'-UTR) and 694 bases of 3'-UTR. While only a single mRNA species occurs in rats and mice, the most proximal signal for polyadenylation in the human gene appears to be highly degenerate in comparison to the rat and murine motif. This polyadenylation signal-like motif may lead to alternate usage of additional polyadenylation sites resulting in multiple mRNA species in humans. A TATA-like motif and several potential binding sites for transcription factors including AP1, AP2, SP1, and a cAMP response element (CRE)-like motif are present in the 5'-flanking region. A approximately 1.7 kb fragment beginning 217 bp downstream from the transcription start site, which had been ligated into a luciferase reporter vector and transiently expressed in JAR human placental choriocarcinoma cells, displayed both constitutive and forskolin/cholera toxin-induced promoter activity. Functional promoter mapping revealed that there are negative attenuating elements between bp -1,428 and -1,185 and positive elements between bp -1,184 and -78 from the transcription initiation site. Studies with deletional mutants also indicated that core promoter sequences are contained within 78 bp of the transcription start site and that regulation of cAMP-inducible promoter activity depends on multiple cis-acting elements including two AP1 binding sites and a single CRE-like element located at bp -99. Our findings suggest that (1) the 5-HT transporter gene promoter is active in human JAR cells, but inactive in 5-HT transporter-deficient human SK-N-SH neuroblastoma and HeLa cells, (2) the information contained within 1.4 kb of 5'-flanking sequence is sufficient to confer its cell-specific expression, (3) the promoter responds to cAMP induction, and (4) the expression of the 5-HT transporter gene is regulated by a combination of positive and negative cis-acting elements operating through a basal promoter unit defined by a TATA-like motif.
... SLC6A4 2 of 12 expression is regulated by the biallelic polymorphism in its promoter region (5-HTTLPR) located upstream of the transcription start site (TTS) [14]. 5-HTTLPR (rs4795541) polymorphism is a 44-base pair (bp) repeat insertion/deletion that generates long (L, with 16 repeats) and short (S, with 14 repeats) alleles, respectively [15][16][17]. Moreover, these two alleles show different transcriptional activity, with the S variant that reduces SLC6A4 expression levels and serotonin uptake compared to the L variant [15][16][17]. ...
... 5-HTTLPR (rs4795541) polymorphism is a 44-base pair (bp) repeat insertion/deletion that generates long (L, with 16 repeats) and short (S, with 14 repeats) alleles, respectively [15][16][17]. Moreover, these two alleles show different transcriptional activity, with the S variant that reduces SLC6A4 expression levels and serotonin uptake compared to the L variant [15][16][17]. Different studies showed that the S allele could be associated with some forms of dependence such as alcohol and heroin [18,19]. Studies on depression characterized the S variant as the sensitive allele due to its reduced ability to remove serotonin (5-HT) from the synaptic space, in comparison to the L allele [17,20]. ...
... The SLC6A4 gene expression is regulated by both the biallelic 5-HTTLPR polymorphism and CpG methylation at the promoter region [15,36]. It is not surprising that the SLC6A4 gene has been studied extensively in recent years. ...
Recently it has been suggested that serotonin transporter (SLC6A4) and its 5HTTLPR polymorphism could be involved in post stroke recovery. Here, we characterized the methylation profile of two different CpG islands within the SLC6A4 promoter region in the whole blood of 50 patients with subacute stroke before and after a six-week rehabilitation treatment. These patients were genotyped for 5HTTLPR polymorphism identifying patients on the basis of short (S) and L (L) alleles: 17 patients LL, 22 patients LS and 11 patients SS. At baseline, all CpG sites for both CpG islands displayed a heterogeneous methylation percentage that were not influenced by the different genotypes. After rehabilitation, we found a significant variation in the methylation levels (increase/decrease) in the specific CpG sites of both CpG islands. The statistical analysis showed a significant relationship between the LL, LS and SS alleles and the outcome of the rehabilitation intervention (χ2 (2,50) = 6.395, p = 0.041). Specifically, we found a significant difference between patients with or without a favorable outcome in the LL (11.1% with a favorable outcome) and in the SS (54.4% with a favorable outcome) groups. Our data suggest that 5-HTTLPR polymorphisms and SLC6A4 promoter methylation may be employed as a non-invasive biological marker of recovery in patients with stroke undergoing rehabilitation.
... These transporters, including SERT, function as oligomeric complexes in the cell membrane, and are regulated primarily through phosphorylation, protein-protein interactions, and trafficking events [11]. Limited data are available on the control of SERT at the transcriptional level, although the genes encoding mammalian forms have been cloned [12]. The 5-prime flanking region of the SERT (5HTT) human gene contains a cyclic AMP-responsive element (CRE) at − 99 bp plus binding sites for AP-1, AP-2, and SP1, all just upstream of a TATA-like motif. ...
... The 5-prime flanking region of the SERT (5HTT) human gene contains a cyclic AMP-responsive element (CRE) at − 99 bp plus binding sites for AP-1, AP-2, and SP1, all just upstream of a TATA-like motif. Sequences within − 1.4 kb of the transcription start site confer cell-specific expression, and the basal promoter responds to induction by cAMP [12]. A functional polymorphism (5HTT-LPR) has been identified in the human 5HTT promoter [13], and evidence has accumulated for an association between alleles of this variation and anxiety traits, affective disorders, as well as autism. ...
Background
Diminished brain levels of two neurohormones, 5-hydroxytryptamine (5-HT; serotonin) and 1,25-dihydroxyvitamin D3 (1,25D; active vitamin D metabolite), are proposed to play a role in the atypical social behaviors associated with psychological conditions including autism spectrum disorders and depression. We reported previously that 1,25D induces expression of tryptophan hydroxylase-2 (TPH2), the initial and rate-limiting enzyme in the biosynthetic pathway to 5-HT, in cultured rat serotonergic neuronal cells. However, other enzymes and transporters in the pathway of tryptophan metabolism had yet to be examined with respect to the actions of vitamin D. Herein, we probed the response of neuronal cells to 1,25D by quantifying mRNA expression of serotonin synthesis isozymes, TPH1 and TPH2, as well as expression of the serotonin reuptake transporter (SERT), and the enzyme responsible for serotonin catabolism, monoamine oxidase-A (MAO-A). We also assessed the direct production of serotonin in cell culture in response to 1,25D.
Results
Employing quantitative real-time PCR, we demonstrate that TPH-1/-2 mRNAs are 28- to 33-fold induced by 10 nM 1,25D treatment of cultured rat serotonergic neuronal cells (RN46A-B14), and the enhancement of TPH2 mRNA by 1,25D is dependent on the degree of neuron-like character of the cells. In contrast, examination of SERT, the gene product of which is a target for the SSRI-class of antidepressants, and MAO-A, which encodes the predominant catabolic enzyme in the serotonin pathway, reveals that their mRNAs are 51–59% repressed by 10 nM 1,25D treatment of RN46A-B14 cells. Finally, serotonin concentrations are significantly enhanced (2.9-fold) by 10 nM 1,25D in this system.
Conclusions
These results are consistent with the concept that vitamin D maintains extracellular fluid serotonin concentrations in the brain, thereby offering an explanation for how vitamin D could influence the trajectory and development of neuropsychiatric disorders. Given the profile of gene regulation in cultured RN46A-B14 serotonergic neurons, we conclude that 1,25D acts not only to induce serotonin synthesis, but also functions at an indirect, molecular-genomic stage to mimic SSRIs and MAO inhibitors, likely elevating serotonin in the CNS. These data suggest that optimal vitamin D status may contribute to improving behavioral pathophysiologies resulting from dysregulation of serotonergic neurotransmission.
... To the best of our knowledge, this is the first genetic association study investigating SI in ACS patients. The 5-HTTLPR has been examined as an important candidate gene for suicidal vulnerability in the general population [1] as it regulates serotonin turnover and its concentrations in the synaptic cleft [26]. Furthermore, it has been suggested that the s allele of 5-HTTLPR is associated with SI in other physical illnesses, stroke [27]. ...
... There are several possible mechanisms explaining this association. First, the s allele of 5-HTTLPR is known to be associated with reduced transcriptional activity [26]. The resulting altered serotonergic signaling may, via platelet aggregation, influence the predisposition toward ACS and may mediate cognitive inflexibility and aggressive behavior [28], which would, in turn, impair the ability to cope with stressful events (e.g., an ACSrelated event). ...
The genetic predisposition toward suicidal ideation has been explored to identify subgroups at high risk and to prevent suicide. Acute coronary syndrome (ACS) is associated with an increased risk of suicide, but few studies have explored the genetic predisposition toward suicide in ACS populations. Therefore, this longitudinal study explored the genetic predisposition toward suicidal ideation in ACS patients. In total, of 969 patients within 2 weeks after ACS, 711 were followed at 1 year after ACS. Suicidal ideation was evaluated with the relevant items on the Montgomery-Åsberg Depression Rating Scale. Ten genetic polymorphisms associated with serotonergic systems, neurotrophic factors, carbon metabolism, and inflammatory cytokines were examined. Associations between genetic polymorphisms and suicidal ideation within 2 weeks and 1 year of ACS were investigated using logistic regression models. The 5-HTTLPR s allele was significantly associated with suicidal ideation within 2 weeks of ACS after adjusting for covariates and after the Bonferroni correction. TNF-a -308G/A, IL-1β -511C/T, and IL-1β + 3953C/T were significantly associated with suicidal ideation within 2 weeks after ACS, but these associations did not reach significance after the Bonferroni correction in unadjusted analyses and after adjusting for covariance. However, no significant association between genetic polymorphisms and suicidal ideation was found at 1 year. Genetic predisposition, 5-HTTLPR s allele in particular, may confer susceptibility to suicidal ideation in ACS patients during the acute phase of ACS.
... reported by Heils et al. [33], as well as to the variable repeat [CAAA] in the second intron of the AP-2β transcription factor gene described by Moser et al. [34]. The associations, however, occurred only in boys. ...
HTR1A (5-hydroxytryptamine receptor 1A) and its polymorphic variants are highly important for athletes in different aspects, allowing us to hypothesize their biological influences. Hence, to investigate at least part of the relationship mentioned in the case literature, it was decided to study the association of the selected HTR1A polymorphism with personality traits measured by the Temperament and Character Inventory (TCI). The participants consisted of 250 mixed martial arts (combat sport) athletes and 209 healthy male participants (control group). The personality traits were measured for the Revised Temperament and Character Inventory (TCI-R). Genetic material was isolated from whole blood collected from patients, and then all samples were genotyped using the real-time PCR method. Statistical analysis was performed using a 2 × 3 factorial ANOVA. The research revealed a statistically significant effect of a complex factor of rs6295 of the HTR1A serotonin receptor gene with combat sport/control and with Novelty Seeking (F2,453 = 6.126; p = 0.0024; η² = 0.026) and Harm Avoidance (F2,453 = 3.709; p = 0.0252; η² = 0.016). The presence of the HTR1A GG genotype (rs6295) was found to be associated with higher scores in self-management and lower scores in harm avoidance, indicating genetic predispositions in the strength group towards better results in combat sports.
... The VNTR composition shows 40 different allelic variants currently known [8] with the insertion or deletion of 20-24 bp repeat units leading to the most common alleles: the long (L) or short (S) allele. As reviewed by Iurescia et al. [8], despite some controversial results [9,10], the majority of in vitro expression studies largely confirmed higher transcriptional activity of the promoter containing the L-allele [11][12][13]. Furthermore, the mRNA transcription efficacy is modulated by the single nucleotide polymorphism (SNP) rs25531, an A to G substitution located within the 5-HTTLPR. The G allele leads to reduced expression [13] and because the S G allele frequency is lower than 1% in humans [14] as well as it is almost in phase with the L allele [15], the HTTLPR is often considered a triallelic polymorphism with L A allele (L') as the highest expressing and L G and S A alleles (S') as the low expressing haplotypes. ...
... Impulsive and aggressive behavior have also been consistently associated with low capacity of the central serotonergic system (Coccaro 1992;Evenden 1999), and the serotonin transporter plays a key role in serotonergic neurotransmission. The s'-allele of the serotonin transporter gene-linked polymorphic region (5-HTTLPR; Heils et al. 1995) has been associated with aggressiveness, hostility, violence, and criminality in some studies (Veroude et al. 2016). It has previously been shown that the 5-HTTLPR s'-allele carriers have lower adaptive impulsivity (Luht et al. 2019) and less violations and accidents in traffic, compared to l'/l' homozygotes (Eensoo et al. 2018). ...
... 5-HTTLPR (serotonintransporter-linked polymorphic region) es la región polimórfica más estudiada, ubicada en la región promotora, 1 kpb "upstream" del sitio de inicio de transcripción (A. Heils et al., 1995). Por su localización, esta región modula: la tasa transcripcional de SLC6A4, la disponibilidad de 5-HTT y la recaptación de 5-HT (K. ...
Antecedentes: El trastorno por estrés postraumático (en adelante TEPT) es un desorden neuropsiquiátrico desarrollado en sujetos tras la exposición a un trauma, caracterizado por un amplio espectro de síntomas. Múltiples causas hacen que un individuo sea más sensible al estrés y, en consecuencia, presente mayor vulnerabilidad a desarrollar TEPT. Objetivo: Esta vulnerabilidad parece ser influenciada por factores genéticos. El objetivo de esta reflexión es presentar hallazgos relevantes en estudios de asociación entre TEPT y dos genes candidatos extensamente explorados, SLC6A4 y BDNF, además de entender las bases moleculares de la influencia de los polimorfismos más estudiados (5-HTTLPR y Val66Met) en estos genes sobre la vulnerabilidad del TEPT. Resultados: En general, se han encontrado asociaciones positivas, específicamente del alelo “S” (gen SLC6A4) y del alelo Met (gen BDNF) y su interacción con factores ambientales como variaciones de riesgo en el TEPT. Conclusiones: Sin embargo, algunos resultados no son concluyentes, por tanto, es necesario que nuevos estudios empleen enfoques genéticos más acertados, contemplen múltiples genes o aborden sus estudios con GWAS.
... The transporter has been a target for anti-depressants (Stein et al., 2021). Among the genetic variations, an HTTLPR polymorphism has been identified in the promoter region (Heils et al., 1995;Nakamura et al., 2000) that gives rise to two alleles (L and S) characterized by 16 and 14 HTTLPR repeats, respectively (Lesch et al., 1996). The L allele has been linked to obsessive compulsive disorders (Hu et al., 2006) but carriers of at least one L allele were more likely to respond to antidepressant therapy (e.g., better prognosis for LL and LS compared to SS) (Stein et al., 2021;Wilkie et al., 2009). ...
SLC6A4 is a serotonin re-uptake transporter which has been a target for anti-depressant therapies but recently some mutations have been described in cancer cells. Here, we characterize mutations in SLC6A4 that appear in cancer cells. We employed several validated computational and artificial intelligence algorithms to characterize the mutations. We identified a previously uncharacterized G100V mutation in lung cancers. In sillico structural analysis reveals that this mutation may affect SLC6A4 ligand binding and subsequently its function. We also identified several other mutations that may affect the structure of the protein. This preliminary analysis highlights the role of SLC6A4 in human cancers.
... Besides, in macaques, 5-HTTLPR has shown a significant correlation with aggressionrelated behavior 20 . L and S alleles are 5-HTTLPR major alleles which S allele results in lower expression and the L allele cause higher transcriptional activity 21,22 . Up to now, several studies investigate the role of different genotypes of 5-HTTLPR in psychosis. ...
Schizophrenia is a severe, disabling psychiatric disorder with unclear etiology. Family-based, twins, and adoption studies have shown that genetic factors have major contributions in schizophrenia occurrence. Until now, many studies have discovered the association of schizophrenia and its comorbid symptoms with functional polymorphisms that lie within serotonin reuptake pathway genes. Here, we aimed to investigate the association of three variable number tandem repeats (VNTR) functional polymorphisms in MAOA and SLC6A4 with schizophrenia in the Iranian population. Two hundred and forty-one subjects with schizophrenia and three hundred and seventy age and sex-matched healthy controls were genotyped for MAOA promoter uVNTR, 5-HTTLPR, and STin2 polymorphisms. Genotyping was performed by polymerase chain reaction (PCR) with locus-specific primers and running the PCR product on agarose 2.5% gel electrophoresis. Finally, the statistical inference was performed using R programming language and Haploview software. MAOA promoter uVNTR analysis of allele frequency showed no differences between schizophrenia subjects and healthy controls in both males and females and no significant differences were observed between female cases and female controls in MAOA promoter uVNTR 4 repeat frequency. Also, there were no differences between Schizophrenia and healthy control groups in 5-HTTLPR allele and genotype frequency but, 5-HTTLPR S allele carriers are significantly more frequent among cases. In addition, STin2.12 repeats were significantly more frequent among schizophrenia patients. Genotype comparison suggested that 5-HTTLPR S allele and STin2.12 repeat carriers were significantly more frequent among schizophrenia cases and being STin2.12 repeat carrier significantly increase the risk of schizophrenia occurrence. Besides, analysis of haplotype showed stronger linkage disequilibrium between 5-HTTLPR and STin2 haplotype block in cases than controls. These results suggest that SLC6A4 functional polymorphisms potentially could play a possible role as risk factors for the incidence of schizophrenia. Schizophrenia (SCZ) is one of the five major psychiatric disorders with an approximate prevalence of 1% worldwide 1. As a multifactorial disease, the exact etiology of SCZ is still unknown. However, family-based, twins, and adoption studies suggest the contribution of 46%-80% of genetic factors in the incidence and pathogenesis of SCZ 2. Even though multiple genes and pathways take a part in the incidence and severity of SCZ, the involvement of monoamine neurotransmitters is one of the most probable theories for decades 3. Serotonin (5-HT) is a neurotransmitter responsible for setting various functions such as emotional features, anxiety traits, aggression, and Etc 4. Earlier, Several studies have given shreds of evidence to show the substantial role of the 5-HT and serotonergic pathway in the pathophysiology of SCZ and other psychiatric disorders 5. Serotonin transporter (5-HTT), encoded by the SLC6A4 gene (location:17q11.1-q12), is known as one of the major regulators of 5-HT via reuptake serotonin from synaptic clefts 6-8. Following the reuptake process, 5-HT
... SLC6A4 encodes solute carrier family 6 member (serotonin transporter), whose abnormal expression levels are predominately associated with various episodes of depression [92]. The genetic mutations in 5HHTLPR are usually linked with the presence of "L allele" (16 GC-rich repeated elements of 20-30 bp) or absence of "S-allele" (14 repeated units of 20-30 bp except for deleted regions from 6th to 8th repeated elements) along with other rare variants containing 15, 19 and >20 repeats and SNPs [93][94][95][96]. Therefore, it is hypothesized that polymorphism or silencing of the SLC6A4 gene may result in abnormal expression of the SLC6A4 mRNA, which induces abnormal serotonin uptake and manifests mood disabilities [96,97]. ...
Major depressive disorder (MDD) is a neuropsychiatric disorder, which remains challenging to diagnose and manage due to its complex endophenotype. In this aspect, circulatory mi-croRNAs (cimiRNAs) offer great potential as biomarkers and may provide new insights for MDD diagnosis. Therefore, we systemically reviewed the literature to explore various cimiRNAs contributing to MDD diagnosis and underlying molecular pathways. A comprehensive literature survey was conducted, employing four databases from 2012 to January 2021. Out of 1004 records, 157 reports were accessed for eligibility criteria, and 32 reports meeting our inclusion criteria were considered for in-silico analysis. This study identified 99 dysregulated cimiRNAs in MDD patients, out of which 20 cimiRNAs found in multiple reports were selected for in-silico analysis. KEGG pathway analysis indicated activation of ALS, MAPK, p53, and P13K-Akt signaling pathways, while gene ontology analysis demonstrated that most protein targets were associated with transcription. In addition , chromosomal location analysis showed clustering of dysregulated cimiRNAs at proximity 3p22-p21, 9q22.32, and 17q11.2, proposing their coregulation with specific transcription factors primarily involved in MDD physiology. Further analysis of transcription factor sites revealed the existence of HIF-1, REST, and TAL1 in most cimiRNAs. These transcription factors are proposed to target genes linked with MDD, hypothesizing that first-wave cimiRNA dysregulation may trigger the second wave of transcription-wide changes, altering the protein expressions of MDD-affected cells. Overall, this systematic review presented a list of dysregulated cimiRNAs in MDD, notably miR-24-3p, let 7a-5p, miR-26a-5p, miR135a, miR-425-3p, miR-132, miR-124 and miR-16-5p as the most prominent cimiRNAs. However, various constraints did not permit us to make firm conclusions on the clinical significance of these cimiRNAs, suggesting the need for more research on single blood compartment to identify the biomarker potential of consistently dysregulated cimiRNAs in MDD, as well as the therapeutic implications of these in-silico insights. Citation: Rasheed, M.; Asghar, R.; Firdoos, S.; Ahmad, N.; Nazir, A.; Ullah, K.M.; Li, N.; Zhuang, F.; Chen, Z.; Deng, Y. A Systematic Review of Circulatory microRNAs in Major Depressive Disorder: Potential Biomarkers for Disease Prognosis.
... The effect of common genotype variants, for example the COMTVal158Met (Lachman et al., 1996), 5-HTTLPR rs 25531 s/L (Heils et al., 1995) and D2DRTaq1A1 (Neville et al., 2004) has not been studied in great detail (see Tables 1, 2 for the reported studies). A few studies have looked at epistasis, i.e., how genotypes interact with each other in a pharmacodynamic way. ...
CNS disorders are lagging behind other indications in implementing genotype-dependent treatment algorithms for personalized medicine. This report uses a biophysically realistic computer model of an associative and dorsal motor cortico-striatal-thalamo-cortical loop and a working memory cortical model to investigate the pharmacodynamic effects of COMTVal158Met rs4680, 5-HTTLPR rs 25531 s/L and D2DRTaq1A1 genotypes on the clinical response of 7 antipsychotics. The effect of the genotypes on dopamine and serotonin dynamics and the level of target exposure for the drugs was calibrated from PET displacement studies. The simulations suggest strong gene-gene pharmacodynamic interactions unique to each antipsychotic. For PANSS Total, the D2DRTaq1 allele has the biggest impact, followed by the 5-HTTLPR rs25531. The A2A2 genotype improved efficacy for all drugs, with a more complex outcome for the 5-HTTLPR rs25531 genotype. Maximal range in PANSS Total for all 27 individual combinations is 3 (aripiprazole) to 5 points (clozapine). The 5-HTTLPR L/L with aripiprazole and risperidone and the D2DRTaq1A2A2 allele with haloperidol, clozapine and quetiapine reduce the motor side-effects with opposite effects for the s/s genotype. The COMT genotype has a limited effect on antipsychotic effect and EPS. For cognition, the COMT MM 5-HTTLPR L/L genotype combination has the best performance for all antipsychotics, except clozapine. Maximal difference is 25% of the total dynamic range in a 2-back working memory task. Aripiprazole is the medication that is best suited for the largest number of genotype combinations (10) followed by Clozapine and risperidone (6), haloperidol and olanzapine (3) and quetiapine and paliperidone for one genotype. In principle, the platform could identify the best antipsychotic treatment balancing efficacy and side-effects for a specific individual genotype. Once the predictions of this platform are validated in a clinical setting the platform has potential to support rational personalized treatment guidance in clinical practice.
... The polymorphic SLC6A4 promoter is composed of a variable number (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24) of tandem repeat units , which are 20-24 bp in length and highly homologous. The common 5-HTTLPR alleles implicated in SSRI response are the long (L; 16 repeats) and short (S; 14 repeats) haplotypes, which are defined by a 43 bp insertion/deletion polymorphism (rs4795541) and are strongly associated with higher and lower gene expression, respectively [9][10][11][12]. In addition to these two alleles, extra-long (XL; 17-24 repeats) and extra-short (XS; 11-13 repeats) promoter alleles, have also been identified with low frequencies in the general population [13][14][15][16][17][18]; however, their effects on gene expression are still being elucidated [19]. ...
The SLC6A4 gene has been implicated in psychiatric disorder susceptibility and antidepressant response variability. The SLC6A4 promoter is defined by a variable number of homologous 20–24 bp repeats (5-HTTLPR), and long (L) and short (S) alleles are associated with higher and lower expression, respectively. However, this insertion/deletion variant is most informative when considered as a haplotype with the rs25531 and rs25532 variants. Therefore, we developed a long-read single molecule real-time (SMRT) sequencing method to interrogate the SLC6A4 promoter region. A total of 120 samples were subjected to SLC6A4 long-read SMRT sequencing, primarily selected based on available short-read sequencing data. Short-read genome sequencing from the 1000 Genomes (1KG) Project (~5X) and the Genetic Testing Reference Material Coordination Program (~45X), as well as high-depth short-read capture-based sequencing (~330X), could not identify the 5-HTTLPR short (S) allele, nor could short-read sequencing phase any identified variants. In contrast, long-read SMRT sequencing unambiguously identified the 5-HTTLPR short (S) allele (frequency of 0.467) and phased SLC6A4 promoter haplotypes. Additionally, discordant rs25531 genotypes were reviewed and determined to be short-read errors. Taken together, long-read SMRT sequencing is an innovative and robust method for phased resolution of the SLC6A4 promoter, which could enable more accurate pharmacogenetic testing for both research and clinical applications.
... JUN was identified as neuronal activator during learning and memory retrieval [67] and J o u r n a l P r e -p r o o f associated with dramatically increases during unconditioned and conditioned fear in amygdala [68]. Reduced expression of SP1, a regulator of SERT [69], is associated with memory deficits [70]. TP53 and RELA have been identified as activated by the hyper-excitation of the stress axis [71], meaning that probably both work as repressors of anxiolytic genes. ...
Social Anxiety Disorder (SAD) is characterized by emotional and attentional biases as well as distorted negative self-beliefs. According this, we proposed to identify the brain structures and hub genes involved in SAD. An analysis in Pubmed and TRANSFAC was conducted and 72 genes were identified. Using Microarray data from Allen Human Brain Atlas it was possible to identify three modules of co-expressed genes from our gene set (R package WGCNA). Higher mean gene expression was found in cortico-medial group, basomedial nucleus, ATZ in amygdala and in head and tail of the caudate nucleus, nucleus accumbens and putamen in striatum. Our enrichment analysis identified the followed hub genes: DRD2, HTR1A, JUN, SP1 and HDAC4. We suggest that SAD is explained by delayed extinction of circuitry for conditioned fear caused by reduced activation of the dopaminergic and serotonergic systems due diminished expectation of reward during social interactions.
... SLC6A4 has a functional polymorphism at a promoter region known as the 5-HTT-linked polymorphic region (5-HTTLPR), ie, classified into short (S) and long (L) alleles, 2 with the S allele exhibiting weaker transcriptional activity. 3,4 Caspi et al 5 reported that gene-by-environment (G × E) interactions between 5-HTTLPR and adverse life experiences are associated with the development of anxiety and depression. To date, numerous case-control association studies have been performed, and several meta-analyses have validated the G × E interactions. ...
Associations between altered DNA methylation of the serotonin transporter (5-HTT)-encoding gene SLC6A4 and early life adversity, mood and anxiety disorders, and amygdala reactivity have been reported. However, few studies have examined epigenetic alterations of SLC6A4 in schizophrenia (SZ). We examined CpG sites of SLC6A4, whose DNA methylation levels have been reported to be altered in bipolar disorder, using 3 independent cohorts of patients with SZ and age-matched controls. We found significant hypermethylation of a CpG site in SLC6A4 in male patients with SZ in all 3 cohorts. We showed that chronic administration of risperidone did not affect the DNA methylation status at this CpG site using common marmosets, and that in vitro DNA methylation at this CpG site diminished the promoter activity of SLC6A4. We then genotyped the 5-HTT-linked polymorphic region (5-HTTLPR) and investigated the relationship among 5-HTTLPR, DNA methylation, and amygdala volume using brain imaging data. We found that patients harboring low-activity 5-HTTLPR alleles showed hypermethylation and they showed a negative correlation between DNA methylation levels and left amygdala volumes. These results suggest that hypermethylation of the CpG site in SLC6A4 is involved in the pathophysiology of SZ, especially in male patients harboring low-activity 5-HTTLPR alleles.
... Interestingly, as opposed to the transcript lengthening observed when polymorphisms or mutations in proximal PAS hexamers reduce CPA efficiency, alterations in distal PAS hexamers predominately result in 3 UTR shortening. An example of this is seen with the serotonin transporter gene, solute carrier family 6 member 4 (SLC6A4), which possesses two 3 UTR PASs [245,246], with the proximal being a variant AATGAA hexamer with low CPA efficiency [58], while the distal contains a common SNP (rs3813034) resulting in either of the very rare hexamers ATTAAC or AGTAAC. The G-allele leads to less efficient use of the distal PAS. ...
A crucial feature of gene expression involves RNA processing to produce 3′ ends through a process termed 3′ end cleavage and polyadenylation (CPA). This ensures the nascent RNA molecule can exit the nucleus and be translated to ultimately give rise to a protein which can execute a function. Further, alternative polyadenylation (APA) can produce distinct transcript isoforms, profoundly expanding the complexity of the transcriptome. CPA is carried out by multi-component protein complexes interacting with multiple RNA motifs and is tightly coupled to transcription, other steps of RNA processing, and even epigenetic modifications. CPA and APA contribute to the maintenance of a multitude of diverse physiological processes. It is therefore not surprising that disruptions of CPA and APA can lead to devastating disorders. Here, we review potential CPA and APA mechanisms involving both loss and gain of function that can have tremendous impacts on health and disease. Ultimately we highlight the emerging diagnostic and therapeutic potential CPA and APA offer.
... SLC6A4 has a functional polymorphism at a promoter region known as the 5-HTT-linked polymorphic region (5-HTTLPR) that is classified into short (S) and long (L) alleles, 2 with the S allele exhibiting weaker transcriptional activity. 3,4 Caspi et al. 5 reported that gene-by-environment (G x E) interactions between 5-HTTLPR and adverse life experiences are associated with the development of anxiety and depression. To date, numerous case-control association studies have been performed, and several meta-analyses have validated the G x E interactions. ...
Associations between altered DNA methylation of the serotonin transporter (5-HTT)-encoding gene SLC6A4 and early life adversity, mood and anxiety disorders, and amygdala reactivity have been reported. However, few studies have examined epigenetic alterations of SLC6A4 in schizophrenia (SZ). We examined CpG sites of SLC6A4 , whose DNA methylation levels have been reported to be altered in bipolar disorder, using three independent cohorts of patients with SZ and age-matched controls. We found significant hypermethylation of a CpG site in SLC6A4 in male patients with SZ in all three cohorts. We showed that chronic administration of risperidone did not affect the DNA methylation status at this CpG site using common marmosets, and that in vitro DNA methylation at this CpG site diminished the promoter activity of SLC6A4 . We then genotyped the 5-HTT-linked polymorphic region (5-HTTLPR) and investigated the relationship among 5-HTTLPR, DNA methylation, and amygdala volume using brain imaging data. We found that patients harboring low-activity 5-HTTLPR alleles showed hypermethylation and they showed a negative correlation between DNA methylation levels and left amygdala volumes. These results suggest that hypermethylation of the CpG site in SLC6A4 is involved in the pathophysiology of SZ, especially in male patients harboring low-activity 5-HTTLPR alleles.
... The serotonin 5-hydroxytryptamine (5-HT) transporter (5-HTT, also known as SERT) is tasked with sequestering synaptic serotonin into the presynaptic neuron for neurotransmission attenuation and recycling (54,55) and is transcribed from the 5-HTT gene on the long arm of chromosome 17 (56)(57)(58). The 5-HT transporter-linked polymorphic region (5-HTTLPR) locus has been associated with differential sensitivity to the environment (59,60). ...
Objective:
New technologies incorporating genetics and neuroimaging into psychiatric care offer the possibility of illuminating associations among genetic alleles, neural functioning, and patients' response to various psychotherapeutic modalities. In this review, the authors survey the literature on the emerging field of genetic predictors of psychotherapy response, particularly in relation to the 5-HTTLPR polymorphism and individual response to manualized psychotherapy.
Methods:
The extant literature was reviewed, with PubMed serving as the primary database.
Results:
Several polymorphisms have been linked with response or resistance to treatment. Given the number of studies assessing the relevance of the 5-HTTLPR polymorphism to treatment response, this review focuses on this genetic variation.
Conclusions:
Because individual genetic endowments may predict nonresponse to manualized treatment modalities, it may become possible to identify individuals who would benefit from insight-oriented, open-ended psychotherapy tailored to their individual distress tolerance levels, rather than from shorter manualized treatment.
... We focus on COMTVal158Met rs4680, 12 5-HTTLPR rs25531 s/L, 13 and APOE, as they are common variants that affect cognitive state and their effects on dopamine and serotonin dynamics (important for cognition) and on amyloid physiology have been documented. ...
Background:
Many trials of amyloid-modulating agents fail to improve cognitive outcome in Alzheimer's disease despite substantial reduction of amyloid β levels.
Methods:
We applied a mechanism-based Quantitative Systems Pharmacology model exploring the pharmacodynamic interactions of apolipoprotein E (APOE), Catechol -O -methyl Transferase (COMTVal158Met), and 5-HT transporter (5-HTTLPR) rs25531 genotypes and aducanumab.
Results:
The model predicts large clinical variability. Anticipated placebo differences on Alzheimer's Disease Assessment Scale (ADAS)-COG in the aducanumab ENGAGE and EMERGE ranged from 0.77 worsening to 1.56 points improvement, depending on the genotype-comedication combination. 5-HTTLPR L/L subjects are found to be the most resilient. Virtual patient simulations suggest improvements over placebo between 4% and 20% at the 10 mg/kg dose, depending on the imbalance of the 5-HTTLPR genotype and exposure. In the Phase II PRIME trial, maximal anticipated placebo difference at 10 mg/kg ranges from 0.3 worsening to 5.3 points improvement.
Discussion:
These virtual patient simulations, once validated against clinical data, could lead to better informed future clinical trial designs.
... The 3′UTR, the region of the mRNA downstream of the proteincoding region, is also known to influence protein expression (Tian and Manley, 2017). The SERT 3′UTR exists as one of two variants, which differ by approximately 130 bp, due to alternative polyadenylation sites (Yoon et al., 2013;Heils et al., 1995;Battersby et al., 1999). Among other functions, the 3′UTR is a common target for protein binding and miRNA binding. ...
The serotonin transporter (SERT, SLC6A4) is a Na⁺-dependent transporter that regulates the availability of serotonin (5-HT, 5-hydroxytryptamine), a key neurotransmitter and hormone in the brain and the intestine. The human SERT gene consists of two alternate promoters that drive expression of an identical SERT protein. However, there are different mRNA transcript variants derived from these two promoters that differ in their 5′ untranslated region (5′UTR), which is the region of the mRNA upstream from the protein-coding region. Two of these transcripts contain exon-1a and are abundant in neuronal tissue, whereas the third transcript contains exon-1c and is abundant in the intestine. The 3′UTR is nearly identical among the transcripts. Current studies tested the hypothesis that the UTRs of SERT influence its expression in intestinal epithelial cells (IECs) by controlling mRNA or protein levels. The SERT UTRs were cloned into luciferase reporter plasmids and luciferase mRNA and activity were measured following transient transfection of the UTR constructs into the model IEC Caco-2. Luciferase activity and mRNA abundance were higher than the empty vector for two of the three 5′UTR variants. Calculation of translation index (luciferase activity divided by the relative luciferase mRNA level) revealed that the exon-1a containing 5′UTRs had enhanced translation when compared to the exon-1c containing 5′UTR which exhibited a low translation efficiency. Compared to the empty vector, the SERT 3′UTR markedly decreased luciferase activity. In silico analysis of the SERT 3′UTR revealed many conserved potential miRNA binding sites that may be responsible for this decrease. In conclusion, we have shown that the UTRs of SERT regulate mRNA abundance and protein expression. Delineating the molecular basis by which the UTRs of SERT influence its expression will lead to an increased understanding of post-transcriptional regulation of SERT in GI disorders associated with altered 5-HT availability.
... Th at region is called polymorphic region linked to the serotonin transporter gene, 5-HTTLPR, named after 5-HT transporter gene-linked polymorphic region. Variations in this region emerge among a variable number of recurring nucleotide sequences (length 20-23 bp), that is their insertion or deletion, which can result in two frequent alleles, i.e. long (insertion) or L variant with 16 recurring sequences and short (deletion) or S variant with 14 recurring sequences 29,30 . Although at the beginning, two original variants (S and L) of 5-HTTLPR polymorphism were intensely researched, in 2006 it was discovered that 5-HTTLPR polymorphism is functionally a three-allele one. ...
Th e aim of the study was to test the correlation between 5-HTTLPR polymor-phism and dental anxiety. Research hypothesis was that positive relation between the expression of dental anxiety and the S allele exists in the population of healthy Caucasians. We conducted a prospective study on 159 subjects, volunteers made up of medical and non-medical staff of the Sestre milosrdnice University Hospital Centre. Both genders were included, age range 19 to 59, mentally and physically healthy (according to DSM-5 classifi cation of mental disorders). For the purpose of this research, we used a sociodemographic questionnaire containing the following information: age, gender, education level, work status, marital status and residence. Corah's Dental Anxiety Scale-Revised (DAS-R) was used to measure dental anxiety. Data distribution was tested by Kolmogorov-Smirnov test, diff erence between the groups by χ 2-test and one-way analysis of variance, and correlation of variables by logistic regression. In the study population, we found positive correlation between S-allele and total result in DAS-R questionnaire. Th e presence of S allele suggests that the person will have a higher result in DAS-R questionnaire, i.e. higher expression of dental anxiety.
... The second gene of interest is the serotonin transporter gene (SLC6A4). It is located on the autosomal chromosome 17 and codes for the serotonin transporter (SERT or 5-HTT), a protein that conveys serotonin from the synaptic cleft back into the neuron (Heils et al., 1995). The SLC6A4 gene has a 44 bp insertion/deletion polymorphism with a 20-23 bp repeat unit in the promoter region, which results in two primary alleles: A short allele with 14 repeats (in the following termed 5-HTTLPR-S), and a long allele with 16 repeats (5-HTTLPR-L). ...
... Alterations in SLC6A4 expression have been associated with food intake and obesity in animals and humans; transgenic mice overexpressing SLC6A4 are lighter and shorter than controls [33], whereas SLC6A4 knockout mice develop late onset obesity, hepatic steatosis, glucose intolerance, and insulin resistance [34][35][36]. In humans, a promoter polymorphism within the SLC6A4 gene results in the formation of either a long or a short allele [37]. The short allele reduces transcription compared to the long allele [38], and is associated Bold values indicate a p value lower than 0.05 Differential SLC6A4 methylation: a predictive epigenetic marker of adiposity from birth to adulthood with obesity in children [18], adult males [19] and with type-2 diabetes [38,39]. ...
Background:
The early life environment may influence susceptibility to obesity and metabolic disease in later life through epigenetic processes. SLC6A4 is an important mediator of serotonin bioavailability, and has a key role in energy balance. We tested the hypothesis that methylation of the SLC6A4 gene predicts adiposity across the life course.
Methods:
DNA methylation at 5 CpGs within the SLC6A4 gene identified from a previous methyl binding domain array was measured by pyrosequencing. We measured DNA methylation in umbilical cord (UC) from children in the Southampton Women's Survey cohort (n = 680), in peripheral blood from adolescents in the Western Australian Pregnancy Cohort Study (n = 812), and in adipose tissue from lean and obese adults from the UK BIOCLAIMS cohort (n = 81). Real-time PCR was performed to assess whether there were corresponding alterations in gene expression in the adipose tissue.
Results:
Lower UC methylation of CpG5 was associated with higher total fat mass at 4 years (p = 0.031), total fat mass at 6-7 years (p = 0.0001) and % fat mass at 6-7 years (p = 0.004). Lower UC methylation of CpG5 was also associated with higher triceps skinfold thickness at birth (p = 0.013), 6 months (p = 0.038), 12 months (p = 0.062), 2 years (p = 0.0003), 3 years (p = 0.00004) and 6-7 years (p = 0.013). Higher maternal pregnancy weight gain (p = 0.046) and lower parity (p = 0.029) were both associated with lower SLC6A4 CpG5 methylation. In adolescents, lower methylation of CpG5 in peripheral blood was associated with greater concurrent measures of adiposity including BMI (p ≤ 0.001), waist circumference (p = 0.011), subcutaneous fat (p ≤ 0.001) and subscapular, abdominal and suprailiac skinfold thicknesses (p = 0.002, p = 0.008, p = 0.004, respectively). In adipose tissue, methylation of both SLC6A4 CpG5 (p = 0.019) and expression of SLC6A4 (p = 0.008) was lower in obese compared with lean adults.
Conclusions:
These data suggest that altered methylation of CpG loci within SLC6A4 may provide a robust marker of adiposity across the life course.
... 1-17q12 (21). In the promotor region of SLC6A4, a 5-HTTLPR (5-hydroxytryptamine transporter-linked polymorphic region) polymorphism was shown to be associated with the availability (the long L allele) or absence (the short S allele) of the 44 bp fragment (22). The L allele bears 16 GC-rich repeated elements of 20-23 bp, whereas the S allele carries 14 similar repeated units that result from the deletion of the region from the 6th to 8th repeated elements (23). ...
Depressive disorders (DDs) are one of the most widespread forms of psychiatric pathology. According to the World Health Organization, about 350 million people in the world are affected by this condition. Family and twin studies have demonstrated that the contribution of genetic factors to the risk of the onset of DDs is quite large. Various methodological approaches (analysis of candidate genes, genome-wide association analysis, genome-wide sequencing) have been used, and a large number of the associations between genes and different clinical DD variants and DD subphenotypes have been published. However, in most cases, these associations have not been confirmed in replication studies, and only a small number of genes have been proven to be associated with DD development risk. To ascertain the role of genetic factors in DD pathogenesis, further investigations of the relevant conditions are required. Special consideration should be given to the polygenic characteristics noted in whole-genome studies of the heritability of the disorder without a pronounced effect of the major gene. These observations accentuate the relevance of the analysis of gene-interaction roles in DD development and progression. It is important that association studies of the inherited variants of the genome should be supported by analysis of dynamic changes during DD progression. Epigenetic changes that cause modifications of a gene's functional state without changing its coding sequence are of primary interest. However, the opportunities for studying changes in the epigenome, transcriptome, and proteome during DD are limited by the nature of the disease and the need for brain tissue analysis, which is possible only postmortem. Therefore, any association studies between DD pathogenesis and epigenetic factors must be supplemented through the use of different animal models of depression. A threefold approach comprising the combination of gene association studies, assessment of the epigenetic state in DD patients, and analysis of different “omic” changes in animal depression models will make it possible to evaluate the contribution of genetic, epigenetic, and environmental factors to the development of different forms of depression and to help develop ways to decrease the risk of depression and improve the treatment of DD.
... Among the genetic variants, previous studies have mainly investigated the role of a transporter-linked polymorphic region (i.e., the 5-HTTLPR polymorphism) in affecting infants' stress response (14)(15)(16)(17). The 5-HTTLPR has a short (S) and long (L) allelic variants (18), with the former being linked to reduced 5-HTT transcription and heightened risk for adverse developmental outcomes, including socio-emotional dysregulation and stress susceptibility (10). ...
Background
Very preterm (VPT) infants are hospitalized in Neonatal Intensive Care Units (NICUs) and are exposed to life-saving procedures eliciting pain-related stress. Recent research documented that pain-related stress might result in birth-to-discharge increased methylation of serotonin transporter gene (SLC6A4) in VPT infants, leading to poorer stress regulation at 3 months of age in VPT infants compared to their full-term (FT) counterparts. Maternal sensitivity is thought to support infants’ stress response, but its role in moderating the effects of altered SLC6A4 methylation is unknown.
Main aim
To assess the role of maternal sensitivity in moderating the association between altered SLC6A4 methylation and stress response in 3-month-old VPT and FT infants.
Methods
53 infants (27 VPTs, 26 FTs) and their mothers were enrolled. SLC6A4 methylation was obtained from peripheral blood samples at NICU discharge for VPT infants and from cord blood at birth for FT infants. At 3 months (age corrected for prematurity), both groups participated to the face-to-face still-face (FFSF) paradigm to measure both infants’ stress response (i.e., negative emotionality) and maternal sensitivity.
Results
Maternal sensitivity did not significantly differ between VPT and FT infants’ mothers. In VPT infants, higher SLC6A4 methylation at hospital discharge associates with higher negative emotionality during the FFSF. In FT infants, SLC6A4 methylation and maternal sensitivity significantly interacted to predict stress response: a positive significant association between SLC6A4 methylation and negative emotionality emerged only in FT infants of less-sensitive mothers.
Discussion
Although no differences emerged in caregiving behavior in the two groups of mothers, maternal sensitivity was effective in moderating the effects of SLC6A4 methylation in FT infants, but not in VPT infants at 3 months. Speculatively, the buffering effect of maternal sensitivity observed in FT infants was disrupted by the altered early mother–infant contact due to NICU stay of the VPT group. These findings indirectly support that the effects of maternal sensitivity on infants’ socio-emotional development might be time dependent, and that mother–infant interventions in the NICU need to be provided precociously within a narrow sensitive period after VPT birth.
... More precisely, drugs used to treat pathological anxiety and depression target the 5-HT system, such as selective serotonin reuptake inhibitors (SSRIs), which block the functioning of the serotonin transporter (5-HTT). A functional polymorphism in the 5-HTT promoter region (5-HTT LPR) has been identified that comprises a 43bp insertion/deletion polymorphism, resulting in a short (s) and a long (l) version differing in transcriptional efficacy(167).The low-efficacy 5-HTT LPR s-allele has consistently been associated with facilitated fear conditioning (i.e. enhanced CS+/CS-differentiation) in uninstructed (Pavlovian) designs(168)(169)(170), instructed fear paradigms(171,172) as well as observational fear learning (173) as assessed by SCRs and FPS in humans. ...
Why do only some individuals develop pathological anxiety following adverse events? Fear acquisition, extinction and return of fear paradigms serve as experimental learning models for the development, treatment and relapse of anxiety. Individual differences in experimental performance were however mostly regarded as ‘noise’ by researchers interested in basic associative learning principles. Our work for the first time presents a comprehensive literature overview and methodological discussion on inter-individual differences in fear acquisition, extinction and return of fear. We tell a story from noise that steadily develops into a meaningful tune and converges to a model of mechanisms contributing to individual risk/resilience with respect to fear and anxiety-related behavior. Furthermore, in light of the present ‘replicability crisis’ we identify methodological pitfalls and provide suggestions for study design and analyses tailored to individual difference research in fear conditioning. Ultimately, synergistic transdisciplinary and collaborative efforts hold promise to not only improve our mechanistic understanding but can also be expected to contribute to the development of specifically tailored (‘individualized’) intervention and targeted prevention programs in the future.
... There are a series of polymorphic regions that might affect the expression or function of serotonin transporter (Ozaki et al., 2003;Wendland et al., 2006). The most studied polymorphism is the 5-HTTLPR, which is a functional polymorphism within the promoter sequence of the serotonin transporter gene (Heils et al., 1995), and it has been linked to variety of behaviours and 17 behavioural disorders, including impulsivity, mood, and anxiety (Gordon & Hen, 2004;Eley & Plomin, 1997). However, the evidence for an association is inconsistent when slightly different measures of the trait (harm avoidance, neuroticism, etc.) are used (Munafò et al., 2009). ...
One of the main goals in current personality research is to identify genes behind the measured behavioral variations. This is important in order to study how, under the influence of the environment, gene expression changes are translated into the observed phenotypes. The advances, especially in genomic technologies, have made it possible to identify genetic loci behind these variations, also concerning non-model species. In this chapter, we will describe the role and relevance of quantitative and molecular genetic approaches in explaining the existence and maintenance of variation in animal personality. We here will provide (1) a timely review on the papers published on this topic, (2) an overview of the current situation and progress, and (3) a view on the likely new avenues the field will take.
... Mutations in the 3′-UTR of the SLC6A4 mRNA can thus alter the termination site, the polyadenylation (polyA) site signals, the ratio of multiple polyA sites usage and the secondary structure of the 3′ terminus of the mRNA, underlining the multiple ways by which 3′-UTR polymorphisms may cause a deregulated translational control and thereby a disease [56,57]. The 3′-UTR of the SLC6A4 mRNA contains multiple functional polyadenylation site signals, located at 567 and 690 bp downstream of the stop codon, actually resulting in two mRNA forms that differ by the presence or absence of a 123-bp element [58,59]. 3′-UTR variants regulating SLC6A4 gene expression are summarized in Table 4. ...
Serotonin (5-HT) is a neurotransmitter that regulates fundamental aspects of brain development, physiology and behaviour. The serotonin transporter (5-HTT) is deputized to the reuptake of 5-HT from the intersynaptic space in the presynaptic neurons. 5-HTT governs duration and magnitude of 5-HT biological actions, acting as a master regulator of the fine-tuning of 5-HT signalling. Genetic variation at SLC6A4 gene locus, encoding 5-HTT, contributes to alteration in 5-HT reuptake. The 5-HTTLPR/rs25531/rs25532 polymorphisms located in the promoter region of SLC6A4 gene have been associated with stress-related psychopathology and functional brain phenotypes. Besides, further DNA variations in functional regulative elements located at 5′ and 3′ termini of the SLC6A4 gene influence transcriptional and post-transcriptional steps. Recently, epigenetic processes including SLC6A4 promoter methylation and transcript silencing by microRNA were shown to be involved in the aetiology of affective disorders. Furthermore, gene-environment interactions such as early life stress often encompass epigenetic changes, which can stably mark the genome in response to environmental stimuli potentially altering gene expression across lifespan. Therefore, it seems well established that functional variations in the SLC6A4 gene expression can no longer be ascribed to the modulating 5-HTTLPR promoter polymorphism but need to be integrated with the contribution arising from other interactive elements and epigenetic mechanisms. In this review, we discuss genetic and epigenetic layers of regulation affecting SLC6A4 gene expression. An overview of human and cellular studies investigating the impact of these regulatory processes on SLC6A4 gene expression is provided.
... Although the effect of cholera toxin could be blocked by the PKA inhibitor H-9, SERT activity elevations require chronic drug exposure with the first effects evident at ;8-16 h after treatment. Later work demonstrated that these treatments elevate SERT steady-state mRNA levels (Ramamoorthy et al., 1993), suggesting a transcriptional regulation of SERT downstream of PKA activation, findings confirmed in later transcriptional reporter studies (Heils et al., 1995). Others have sense detected cAMP stimulation of SERT mRNA expression in 5-HT neurons (Rumajogee et al., 2002). ...
Modulation of neurotransmission by the monoamines dopamine (DA), norepinephrine (NE), and serotonin (5-HT) is critical for normal nervous system function. Precise temporal and spatial control of this signaling in mediated in large part by the actions of monoamine transporters (DAT, NET, and SERT, respectively). These transporters act to recapture their respective neurotransmitters after release, and disruption of clearance and reuptake has significant effects on physiology and behavior and has been linked to a number of neuropsychiatric disorders. To ensure adequate and dynamic control of these transporters, multiple modes of control have evolved to regulate their activity and trafficking. Central to many of these modes of control are the actions of protein kinases, whose actions can be direct or indirectly mediated by kinasemodulated protein interactions. Here, we summarize the current state of our understanding of how protein kinases regulate monoamine transporters through changes in activity, trafficking, phosphorylation state, and interacting partners. We highlight genetic, biochemical, and pharmacological evidence for kinaselinked control of DAT, NET, and SERT and, where applicable, provide evidence for endogenous activators of these pathways.We hope our discussion can lead to a more nuanced and integrated understanding of how neurotransmitter transporters are controlled and may contribute to disorders that feature perturbed monoamine signaling, with an ultimate goal of developing better therapeutic strategies. © 2016 by The American Society for Pharmacology and Experimental Therapeutics, All rights reserved.
... The expression of SLC6A4 is regulated by several mechanisms, including genetic variations. Among them, 5-HTTLPR (Heils et al., 1995) is a polymorphism that has been extensively studied in association with stress-related personality traits, behavior, biological and physiological correlates in humans (Canli and Lesch, 2007). A handful of studies suggest that the 5-HTTLPR is a candidate polymorphism for socio-emotional stress susceptibility (Lesch, 2011;Pauli-Pott et al., 2009;Pluess et al., 2011). ...
The application of epigenetics to the study of behavioral and socio-emotional development in humans has revealed that DNA methylation could be a potential marker of adversity exposure and long-lasting programming of health and disease. The serotonin transporter gene (SLC6A4) is a stress-related gene which has well-documented implications for behavioral and socio-emotional development and which has been shown to be susceptible to transcriptional regulation via epigenetic mechanisms. In the present paper, a systematic review of papers assessing the association among adversity exposures, SLC6A4 methylation and developmental outcomes is reported. Nineteen studies were included. Findings revealed that SLC6A4 methylation has been investigated in humans in association with a number of prenatal and postnatal adverse exposures, encompassing maternal depression during pregnancy, perinatal stress exposure, childhood trauma and abuse, and environmental stress. SLC6A4 is confirmed as a relevant biomarker of early adversity exposures, and epigenetic mechanisms occurring at this gene appear to play a critical role for programming. Nonetheless, specific methodological issues still need to be addressed in future human behavioral epigenetic research.
... Recent studies have been intensified for possible association between PMDD and candidate genes of the serotonergic system. Studies to date have searched for polymorphism in the serotonin transporter (SLC6A4) including the 5'HTTLPR, serotonin transporter promoter rs25531, serotonin receptor 1A C (-1019) G, and activating protein 2β (AP-2β) (18) and found no positive results (15)(16)(17)(18). ...
... Volunteers were recruited from a large pool of genotyped individuals and selected on the basis of their 5-HTTLPR/rs25531 genotypes. The short s-allele of the 5-HTTLPR is associated with reduced 5-HTT expression relative to the long l-allele (Heils et al., 1995) as well as the G-allele of the single-nucleotide polymorphism (SNP), rs25531, that reduces 5-HTT expression levels in 5-HTTLPR l-allele carriers to expression levels nearly equivalent to s-carriers (Hu et al., 2006). On this basis, participants were assigned to either a high or a low 5-HTT expressing group depending on their genetic make-up. ...
Deficits in emotional reactivity and recognition have been reported in psychopathy. Impaired attention to the eyes along with amygdala malfunctions may underlie these problems. Here, we investigated how different facets of psychopathy modulate the visual exploration of facial expressions by comparing personality traits in a sample of healthy young adults to eye-tracking data obtained in a face perception task. Fearless Dominance (the interpersonal-emotional facet of psychopathy) and Coldheartedness scores predicted reduced face exploration consistent with findings on lowered emotional reactivity in psychopathy. Moreover, participants high on the social deviance facet of psychopathy ('Self-Centered Impulsivity') showed a reduced bias to shift attention towards the eyes. Our data suggest that facets of psychopathy modulate face processing in healthy individuals and reveal possible attentional mechanisms which might be responsible for the severe impairments of social perception and behavior observed in psychopathy.
... Genomic DnA was extracted from the whole blood. A combination of polymerase chain reaction (PCR) with restriction fragment length polymorphism was applied to detect the three polymorphisms of the 5-HTTLPR gene (SLC6A4) (Heils et al., 1995). PCR was used to amplify the polymorphic region in SLC6A4 (a gain of function insertion/ deletion in the promoter region), yielding 478 or 522 bp fragments (Short and Long alleles). ...
Objective:
In the present study, we investigate the association between the 5-HTTLPR polymorphism and executive functions in a sample of patients with obsessive compulsive disorder (OCD).
Method:
A total of 98 unmedicated patients diagnosed with OCD according to DSM-IV criteria and 80 healthy controls were included in this study. The genotype frequencies of 5-HTTLPR polymorphism were compared in OCD and healthy control groups. The four subgroups of OCD and healthy control participants, determined according to having LaLa genotype (high expressing) or S- and/or Lg alleles (low expressing), were also compared using neuropsychological tests of executive functions.
Results:
The frequency of SLa genotype of 5-HTTLPR polymorphism was found to be higher in patients with OCD compared with healthy controls. The mean scores of conceptual level responses of the Wisconsin Card Sorting Test (WCST) were significantly lower in the OCD-high-expressing subgroup compared with the low-expressing control group. The mean scores of the number of moves of the Tower of London were found to be significantly higher in the OCD-high-expressing subgroup, compared with the high-expressing subgroup of healthy controls.
Conclusion:
Our findings suggest that the high-expressing variant may be associated with lower performance on some abstraction and planning measures in OCD patients.
... Because the job of the serotonin transporter is to reuptake serotonin from the neuronal synapse, its function likely plays a major role in determining the activity of serotonin in the synapse. The s allele has a lower transcriptional efficiency than the l allele has 5,6) and typically exhibits a greater degree of vulnerability to social stressors. 7,8) However, there is still controversy regarding the association of 5-HTTLPR with depression. ...
Objective
The features of childhood attention deficit hyperactivity disorder (ADHD) are significantly associated with adult mood disorders. Some genetic factors may be common to both ADHD and mood disorders underlie the association between these two phenotypes. The present study aimed to determine whether a genetic role may be played by the serotonin transporter-linked polymorphic region (5-HTTLPR) in the childhood ADHD features of adult patients with mood disorders.
Methods
The present study included 232 patients with major depressive disorder (MDD), 154 patients with bipolar disorder (BPD), and 1,288 normal controls. Childhood ADHD features were assessed with the Korean version of the Wender Utah Rating Scale (WURS-K). The total score and the scores of three factors (impulsivity, inattention, and mood instability) from the WURS-K were analyzed to determine whether they were associated with the 5-HTTLPR genotype.
Results
In the BPD type II group, the 5-HTTLPR genotype was significantly associated with the total score (p=0.029) and the impulsivity factor (p=0.004) on the WURS-K. However, the inattention and mood instability factors were not associated with the 5-HTTLPR genotype. BPD type I, MDD and normal control groups did not exhibit any significant associations between the WURS-K scores and the 5-HTTLPR genotype.
Conclusion
The findings suggest that the 5-HTTLPR genotype may play a role in the impulsivity component of childhood ADHD in patients with BPD type II. Because of a small sample size and a single candidate gene, further studies investigating other candidate genes using a larger sample are warranted to determine any common genetic links.
... These genes either directly modulate serotonin (Mann, 1999) signaling or interact with other genes to alter neuroplastic response of the brain. The long "L" and the short "s" functional variants (Heils et al., 1995) of the 5-HTTLPR have received great attention because the "s" allele has been associated with decreased transcription efficiency of the 5-HTT gene (Lesch and Mossner, 1998), thereby decreasing the density of 5-HTT in presynaptic neurons and increasing the intensity and duration of the serotonin signaling (Glatz et al., 2003). However, because several large studies have failed to associate the 5-HTTLPR polymorphism with depression (Caspi et al., 2003), this polymorphism may only moderate the influence of stressful life events and when exposed to stressful life events, individuals with the "s" allele could be at a greater risk for developing depression than those with the "L" allele (Caspi et al., 2003;Eley et al., 2004;Kendler et al., 2005;Wilhelm et al., 2006;Zalsman et al., 2006). ...
... A variation in the length of the 5 Ј -flanking transcriptional control region (promoter) of the 5-HTT gene (the serotonin-transporter-gene-linked polymorphic region; 5-HTTLPR) has been identified in humans , great apes and rhesus monkeys ( Lesch et al. , 1997 ). This variation affects the transcriptional activity of the 5-HTT gene, and the short length ( s ) allele reduces 5-HTT expression in vitro and lowers prolactin response to clomipramine in humans, which reflects reduced 5-HT function, compared to the long-length ( l/l ) homozygote ( Heils et al. , 1995 ;Lesch et al. , 1996 ;Whale et al. , 2000 ). An association study in humans showed that individuals with one or two copies of the s allele ( s/s , s/l ) were characterized by higher anxiety, depression, hostility and aggression, and lower agreeableness, than l/l homozygotes in both sexes (Lesch et al. , 2000). ...
Traditional clinical research on the neurobiology of aggressive behavior focuses on individuals who are characterized by their impulsive, hostile, antisocial and violent traits and who show some deficiency in brain serotonin (5-HT) activity relative to those who have a propensity to engage in premeditated, calculating and instrumental aggressive acts. Preclinical research has focused on territorial, dominant or maternal aggressive behavior patterns, chiefly for reproductive purposes. Recent efforts study individuals who engage in very high levels of aggressive behavior due to genetic selection, consumption of a moderate dose of alcohol, social instigation or pharmacological insults. The early proposal that lower CSF levels of 5-HT and/or 5-HIAA were associated with a greater propensity for violent outbursts (the ‘serotonin deficiency hypothesis’) has been challenged by the evidence implicating receptor subtypes of the 5-HT1 and 5-HT2 families, the serotonin transporter (5-HTT) and metabolic enzyme monoamine oxidase A (MAOA), acting at different levels of the neuroaxis. In vivo techniques revealed a significant role of cortical 5-HT release during the termination of an aggressive confrontation and its consequences, rather than its initiation. Considerable clinical and preclinical evidence implicates 5-HT1A, 5-HT1B and 5-HT2A as targets for pharmacotherapeutic management of escalated aggressive behavior, which are accompanied to a varying extent by non-specific effects, whereas the genetic data for linking these receptors to specific types of aggression are less consistent. The prevalent anti-aggressive effects emerge with drugs targeting the 5-HTT, and the genetic data from human and non-human primates suggest the short allele 5-HTT polymorphism as a risk factor for violent traits, particularly in combination with environmental stress. Contrary to pharmacological inhibition of MAO, mutation of the MAOA gene in humans and mice suggests that chronically elevated 5-HT levels may promote escalated aggressive behavior, most prominently after early life maltreatment. Interactions between 5-HTT and MAOA polymorphisms suggest that complex epistatic interactions may ultimately reveal strong effects on aggressive phenotypes.
There is a striking lack of studies on the molecular genetic basis of metacognition, i.e., the higher-order ability to monitor mental processes. Here, an initial step toward resolving this issue was undertaken by investigating functional polymorphisms from three genes of the dopaminergic or serotonergic systems (DRD4, COMT, and 5-HTTLPR) in relation to behaviorally assessed metacognition in six paradigms across three cognitive domains. We report evidence for a task-dependent higher average confidence level (metacognitive bias) in carriers of at least one S or LG-allele in the 5-HTTLPR genotype and integrate these findings within a differential susceptibility framework.
Objectives
Risk taking behaviour, including in traffic, is related to impulsivity and aggressiveness, and so is unhealthy lifestyle. The serotonin transporter gene promoter polymorphism (5-HTTLPR) has been associated with impulsivity, aggression, alcohol use, speed limit exceeding and traffic accidents. The aim of this study was to examine whether subjects with less healthy eating and exercise habits take more risks in traffic, and whether impulsivity, aggressiveness and the serotonin transporter genotype could mediate or moderate any such associations.
Method
A sub-sample of the Estonian Psychobiological Study of Traffic Behaviour (EPSTB (n = 817) with mean age (SD) = 31.4 (10.0) years filled out lifestyle questionnaires. Impulsivity was measured by Adaptive and Maladaptive Impulsivity Scale and aggressiveness by Buss – Perry Aggression Questionnaire. Traffic violation data in the previous 5 years period were obtained from police database.
Results
Speed limit exceeders had higher physical and verbal aggression, higher AUDIT scores, they reported more vigorous physical activity and drinking energy drinks more often. Path analysis showed that higher AUDIT scores were associated with speeding via higher physical aggression. 5-HTTLPR was not directly associated with speeding or driving while impaired by alcohol (DWI), but 5-HTTLPR s’-allele carriers had lower AUDIT scores if they were not junk food eaters and the other way around, while l’/l’ homozygosity was associated with DWI via higher AUDIT scores.
Conclusion
Significant associations exist between risky traffic behaviour and aspects of lifestyle such as consumption of alcohol or junk food or energy drinks, as well as engagement in vigorous physical activity, while traits such as aggressiveness and the variation in the serotonergic system appear as mediating and moderating factors. Interventions preventing accidents should focus on wider array of behaviours and use personalised approach. Genetic variation should be investigated regarding associations with risk taking and health behaviour, and response to interventions.
Chronischer Stress hat negative Folgen, die sich im Verhalten und auf neuronaler Ebene äußern können. Als besonders stressempfindlich gelten die Neurone der dritten Region des hippocampalen Ammonshorns CA3. Sie reagieren auch im bereits ausgereiften Zustand noch sehr sensibel auf äußere Einflüsse, was als neuronale Plastizität bezeichnet wird. Sie erfahren unter anderem durch Stress und Serotonin morphologische und funktionelle Veränderungen. Serotonin-Transporter wahren das Serotonin-Gleichgewicht, indem sie dessen Wirkung schließlich durch Wiederaufnahme in die Zellen beenden. Polymorphismen, also verschiedene Gen-Varianten, bedingen Unterschiede in der Zahl der verfügbaren Transporter. Dieses Wechselspiel zwischen Gen-Varianten des Serotonin-Transporters und Stress wurde an Serotonin-Transporter-Knockout-Mäusen untersucht. Einige Mäuse erfuhren bereits früh im Leben Stress, der entweder anhielt oder im späteren Leben positiven Erfahrungen wich; weitere Mäuse hingegen machten in frühen Lebensabschnitten positive Erfahrungen, die sich später entweder fortsetzten oder durch Stresserfahrungen ersetzt wurden. Nach Durchführung von Verhaltenstests wurde zudem in deren Golgi-imprägnierten Gehirnen die Morphologie der Apikaldendriten von CA3-Kurzschaft-Pyramidenzellen lichtmikroskopisch untersucht und in 3D-Computermodellen abgebildet. Aufgrund regionaler Eigenheiten innerhalb von CA3 wurden diese Neurone verschiedenen Subpopulationen zugeordnet. Tatsächlich konnten mithilfe der Kombination aus vier verschiedenen Lebensgeschichten und drei unterschiedlichen Serotonin-Transporter-Genotypen Unterschiede in der Morphologie der CA3-Pyramidenzellen zwischen den einzelnen Gruppen festgestellt werden. Ohne Stresserleben zeigten sich die Neurone meist signifikant verzweigter; nach Stresserleben zeigten sich, zumindest in einer bestimmten Subpopulation, signifikante Verminderungen der Spines. Mäuse mit zwei oder einem wildtypischen Serotonin-Transporter-Allel und ausschließlich späten aversiven Erfahrungen hatten signifikant längere Apikaldendriten als die Referenz mit zwei wildtypischen Allelen und ohne Stresserfahrung; homozygot Serotonin-Transporter-defiziente Mäuse der gleichen Lebensgeschichte hatten zur Referenz signifikant verkürzte Apikaldendriten. Diese Ergebnisse lassen vermuten, dass Stress in Verbindung mit genetisch bedingt geringen Mengen des Serotonin-Transporters durchaus eine erhöhte Vulnerabilität für psychische Erkrankungen bedingen könnte, aber dass ausschließlich späte Stresserfahrungen bei höheren Mengen des Serotonin-Transporters auch protektiv wirken könnten.
Very preterm (VPT) infants requiring hospitalization in the Neonatal Intensive Care Unit (NICU) are exposed to several stressful procedural experiences. One consequence of NICU‐related stress is a birth‐to‐discharge increased serotonin transporter gene (SLC6A4) methylation that has been associated with poorer stress regulation at 3 months of age. Maternal touch is thought to support infants’ stress response, but its role in moderating the effects of SLC6A4 methylation changes is unknown. The aim of this study was to assess the role of maternal touch in moderating the association between increased SLC6A4 methylation and stress response in 3‐month‐old VPT infants. Twenty‐nine dyads were enrolled and at 3 months (age corrected for prematurity), participated in the Face‐to‐Face Still‐Face paradigm to measure infants’ stress response (i.e., negative emotionality) and the amount of maternal touch (i.e., dynamic and static). Results showed that low level of maternal touch is associated with high level of negative emotionality during social stress. Furthermore, during NICU stay SLC6A4 methylation in VPT exposed to low level of maternal touch at 3 months was associated with increased negative emotionality. Thus, low levels of maternal static touch can intensify the negative effects of SLC6A4 epigenetic changes on stress response in 3‐month‐old VPT infants.
Background:
Many Alzheimer's disease patients in clinical practice are on polypharmacy for treatment of comorbidities.
Objective:
While pharmacokinetic interactions between drugs have been relatively well established with corresponding treatment guidelines, many medications and common genotype variants also affect central brain circuits involved in cognitive trajectory, leading to complex pharmacodynamic interactions and a large variability in clinical trials.
Methods:
We applied a mechanism-based and ADAS-Cog calibrated Quantitative Systems Pharmacology biophysical model of neuronal circuits relevant for cognition in Alzheimer's disease, to standard-of-care cholinergic therapy with COMTVal158Met, 5-HTTLPR rs25531, and APOE genotypes and with benzodiazepines, antidepressants, and antipsychotics, all together 9,585 combinations.
Results:
The model predicts a variability of up to 14 points on ADAS-Cog at baseline (COMTVV 5-HTTLPRss APOE 4/4 combination is worst) and a four-fold range for the rate of progression. The progression rate is inversely proportional to baseline ADAS-Cog. Antidepressants, benzodiazepines, first-generation more than second generation, and most antipsychotics with the exception of aripiprazole worsen the outcome when added to standard-of-care in mild cases. Low dose second-generation benzodiazepines revert the negative effects of risperidone and olanzapine, but only in mild stages. Non APOE4 carriers with a COMTMM and 5HTTLPRLL are predicted to have the best cognitive performance at baseline but deteriorate somewhat faster over time. However, this effect is significantly modulated by comedications.
Conclusion:
Once these simulations are validated, the platform can in principle provide optimal treatment guidance in clinical practice at an individual patient level, identify negative pharmacodynamic interactions with novel targets and address protocol amendments in clinical trials.
Experimental fear conditioning and extinction represent basic forms of associative learning with considerable clinical relevance and serve as laboratory models for the development and treatment of anxiety disorders, respectively. There is considerable inter-individual variation in the ability to acquire and extinguish conditioned fear reactions as well as the return of fear and approximately one third of the variance in human fear conditioning and in the vulnerability for anxiety disorders can be attributed to genetic factors. The experimental paradigms of fear conditioning and extinction are particularly well suited for genetic association studies as these optimally investigate simple behavioral paradigms with sufficient inter-individual variability and clear heritability that elicit robust behavioral responses which are easy to measure and quantify and rely on a well-defined underlying neural circuitry. Understanding the molecular pathways that mediate conditioning and extinction might therefore make an important contribution to the study of anxiety pathophysiology and resilience. Because a significant proportion of patients do not respond to or tolerate standard treatments, such advances may ultimately open up new perspectives for pharmacological interventions (i.e. pharmacologically enhanced CBT) or the individualization of current prevention and treatment programs. In the future, translational work employing a synergy between molecular genetics, neuroimaging, psychophysiology and psychopharmacology will be powerful in unraveling the neurobiology of fear learning and extinction processes and the investigation of genetic polymorphisms in fear learning and extinction processes represents one avenue along this path.
Depressive disorders are a common cause of emotional suffering, increased disability, premature mortality, increased healthcare utilization costs, and cognitive decline in the elderly. There appear to be multiple unique pathophysiological pathways to late-life depression. This chapter seeks to review the research performed in this field over the last several decades, describing disturbances in fronto-subcortical function, genetic polymorphisms, chronic stress and inflammation, as well as vascular pathology. We also discuss structural and functional neuroimaging studies of late-life depression. Future research must explore outcomes of early intervention strategies combined with a personalized approach to the depressed elderly patient.
Introduction:
Rape and pedophilic child molestation are the most commonly convicted sexual offenses in Poland. Recent studies have suggested a possible genetic contribution toward pathologic sexual interests and behaviors.
Aim:
To analyze and compare functional polymorphisms of genes associated with the activity of the serotonin and dopamine systems in a group of paraphilic sexual offenders and control subjects.
Methods:
The study sample (n = 97) consisted of two groups: paraphilic sexual offenders (65 pedophilic child molesters and 32 rapists) and controls (n = 76). Genetic polymorphisms previously associated with behavioral control, addictive behaviors, and sexual functions were chosen for analyses. Specifically, functional polymorphisms in dopamine receptors genes (DRD1, DRD2, DRD4), catechol-O-methyltransferase gene (COMT), dopamine transporter gene (DAT), serotonin transporter gene (SLC6A4), serotonin type 2A receptor gene (5HTR2A), tryptophan hydroxylase 2 gene (TPH2), monoamine oxidase A gene (MAOA), and brain-derived neurotrophic factor gene (BDNF) were analyzed.
Main outcome measures:
An association between a history of sexual offense and the distribution of genotypes and alleles in the analyzed polymorphisms.
Results:
Our results found no association between a history of sexual offense and the distribution of genotypes or alleles in the analyzed polymorphisms.
Conclusion:
Although these results are limited by the small sample and are exploratory, they highlight a novel approach to sample selection in a population that is difficult to access and study. Future research should include larger samples and other relevant polymorphisms to advance this field of study.
Impulsivity is often described as a predisposition to act prematurely without foresight and is associated with a number of neuropsychiatric and neurological disorders such as pathological gambling, drug addiction, attention deficit hyperactivity disorder, and Parkinson’s disease. Given the central role of impulsivity in these and other brain disorders there has been widespread interest in elucidating the neurobiological mechanisms and particularly the genetic substrates that govern the expression of specific impulsivity endophenotypes. Ultimately, such research could facilitate the development of new pharmacotherapies for the impulse control disorders, defined within the Diagnostic and Statistical Manual (DSM-5). Here we discuss the gene variants, identified predominantly via candidate gene approaches, associated with impulsivity in healthy subjects and neuropsychiatric patient groups, with a particular focus on those found to predict individual variability in impulse control. We discuss the potential of methodologies beyond candidate gene sequencing, utilizing advances in whole genome sequencing, animal models of impulsivity and neuroimaging that collectively implicate specific gene products in impulsivity.
Family violence, which refers to child maltreatment and intimate partner violence, is a widespread problem in the United States. In 2009, the most recent year for which figures are available, 702,000 children were found to be victims of maltreatment, including physical, sexual, and psychological abuse, and neglect (U.S. Department of Health and Human Services, 2010). A survey of 16,000 men and women in the United States found that the lifetime prevalence of intimate partner violence was 17% and approximately 1.3 million women and 834,732 men had been the victims of partner violence in the 12 months prior to the survey (Tjaden & Thoennes, 2000). Worldwide, the lifetime prevalence of intimate partner violence ranges from 15 to 71% (Garcia-Moreno, Jansen, Ellsberg, Heise, & Watts, 2006).
Der Anteil der über Sechzigjährigen in der Bevölkerung nimmt kontinuierlich zu: Während im Jahr 1900 nur etwa 8% der deutschen Bevölkerung älter als 60 Jahre waren, betrug der Anteil 1993 bereits 20%. Im Jahr 2030 sollen es bereits 33% sein. (Bundesinstitut für Bevölkerungsforschung, Wiesbaden). Der Altersaufbau der Bevölkerung wird sich von einer Bevölkerungspyramide zu einem Bevölkerungspilz im Jahre 2050 wandeln (Abb. 1.4.1). 1999 entfielen 53% des gesamten Fertigarzneimittelumsatzes der gesetzlich krankenversicherten Patienten auf die Gruppe der über Sechzigjährigen. Im Durchschnitt wird jeder über Sechzigjährige mit etwa zweieinhalb Arzneimitteln pro Tag in Dauertherapie behandelt (Schröder et al. 2001). Es besteht hinsichtlich der körperlichen und geistigen Leistungsfähigkeit von alten Menschen jedoch eine erhebliche Variabilität. Viele liegen trotz fortgeschrittenen Alters mit ihren Werten innerhalb der Normgrenzen weitaus jüngerer Personen, was die Unterscheidung zwischen „normal“ und „pathologisch“ bei alten Menschen besonders erschwert (Rowe et al. 1987).
Negative emotions such as fear and acute stress elicit integrated enhancement of responses in the cardiovascular system, hypothalamo–pituitary–adrenocortical axis, and innate immunity. On the other hand, during experiences of positive emotions, secretion of central and peripheral dopamine and natural killer cell activity are enhanced without increased sympathetic activity. Such physiological responses accompanying emotions are not rigid and stereotyped but can be flexibly regulated by the brain on the basis of cognitive appraisal of the emotional situation. Using a combination of neuroimaging and physiological recording in humans, we have shown that a neural network that includes several portions of the prefrontal cortex and limbic regions plays a key role in the regulation of emotion. Furthermore, there are wide individual differences in the emotional reactivity in both negative and positive emotional domains. Genetic factors such as gene polymorphisms of the serotonin transporter gene and the opioid receptor gene can explain portions of the individual differences of emotional reactivity.
Serotonin (5-HT), which acts at multiple pre- and postsynaptic receptor sites, fulfills the criteria for a neurotransmitter and modulator of synaptic signal transduction in many functional systems of the brain. As a consequence of this enormous versatility, brainstem 5-HT systems affect many diverse functions, such as mood, cognition, appetite and satiation, sleep, motor behavior, neuroendocrine and circadian rhythms, social and reproductive behavior. By determining the magnitude and duration of postsynaptic receptor-mediated signaling, carrier-facilitated 5-HT transport into and release from the presynaptic neuron plays a key role in the spatiotemporal fine-tuning of 5-HT neurotransmission (Fig. 1). Recent advances have resulted from the molecular and functional characterization of the serotonin transporter (5-HTT), from pharmacological and neurochemical studies relating the actions of psychoactive drugs (e.g., tricyclics, selective 5-HT reuptake inhibitors, psychostimulants) to discrete effects on 5-HT uptake and release, and from the molecular dissection of the complex changes in functional expression as a consequence of altered gene transcription. On the basis of its molecular structure and anatomical distribution, substrate specificity, electrophysiological properties, and drug-binding profiles the 5-HTT has been placed in the extended gene family of Na+/C1--dependent cell surface transport proteins.
The JAR human placental choriocarcinoma cell line transports serotonin, accumulating the monoamine inside the cell against a concentration gradient. The transport is energized by an NaCl gradient. Tricyclic (imipramine and desipramine) and non-tricyclic (paroxetine and fluoxetine) antidepressants inhibit the transporter markedly, but reserpine and 5-hydroxytryptophan do not. Ouabain, gramicidin, and nigericin, which reduce or abolish the transmembrane Na+ gradient, and phloridzin, which interferes with glucose transport into the cells, inhibit the transport. Preincubation of the cells with glucose-free medium also causes similar inhibition. The activity of the serotonin transporter in this cell line is stimulated in response to overnight (16-h) incubation with increasing concentrations of cholera toxin (0.1-1,000 ng/ml). Under these conditions the stimulation is maximal at 10 ng/ml cholera toxin (3.1 +/- 0.2-fold). Cholera toxin increases the cAMP content of these cells by several hundredfold within 2 h. Isobutylmethylxanthine (100 microM), dibutyryl cAMP (100 microM), and forskolin (100 microM) mimic the action of cholera toxin, eliciting a 1.6-2.5-fold stimulation of the serotonin transporter activity. The stimulatory effect of cholera toxin is antagonized significantly by simultaneous incubation of the cells with 50 microM N-(2-aminoethyl)-5-isoquinolinesulfonamide, a protein kinase inhibitor. The effect of cholera toxin on serotonin transport is specific because, under similar conditions, cholera toxin inhibits 3-O-methyl-D-glucose transport and does not influence taurine transport in this cell line. There is also no significant change in the protein content of the cells after cholera toxin treatment. Kinetic analysis reveals that cholera toxin causes an increase in the maximal velocity (7.89 +/- 0.67 to 17.55 +/- 1.06 pmol/mg of protein/5 min) and a decrease in the Michaelis-Menten constant (0.52 +/- 0.09 to 0.29 +/- 0.04 microM). These data show that the JAR human placental choriocarcinoma cell line expresses a high affinity serotonin transporter that is sensitive to inhibition by antidepressants and that the activity of the transporter is under cAMP-dependent regulation.
Treatment of confluent cultures of JAR human placental choriocarcinoma cells with cholera toxin or forskolin for 16 h markedly stimulated (2.4-fold) serotonin transport activity in these cells. Cycloheximide, an inhibitor of protein synthesis or actinomycin D, an inhibitor of mRNA synthesis effectively blocked this stimulation. Northern blot analysis revealed that treatment with cholera toxin resulted in severalfold increase in the concentrations of the three mRNA species (6.8, 4.9 and 3.0 kilobases in size) which hybridized to the human placental serotonin transporter cDNA. Under similar conditions, the concentrations of the mRNA species which hybridized to the human placental taurine transporter cDNA or to the human beta-actin cDNA were not affected. Analysis of paroxetine-sensitive binding of the cocaine analog 2 beta-carbomethoxy-3 beta-(4- [125I]iodophenyl)tropane to the membranes prepared from control and cholera toxin-treated cells indicated that the maximal binding capacity was increased 2.5-fold by cholera toxin, with no significant change in the binding affinity. Thus, stimulation of serotonin transporter activity in the placental choriocarcinoma cells following cholera toxin treatment is likely a result of an increase in cell surface density of the serotonin transporter protein as a consequence of increased steady state serotonin transporter mRNA levels.
In the last 5 years, there has been considerable progress in the molecular characterisation of multiple neurotransmitter reuptake mechanisms (or neurotransporters). Neurotransporters are high affinity reuptake proteins located in the plasma membrane of both presynaptic nerve and glial cells. They mediate the removal of the neurotransmitter from the synaptic cleft or represent intracellular transport systems that concentrate neurotransmitters in synaptic vesicles. Based on subcellular distribution and pharmacological properties, neurotransporters have been placed into 3 main subgroups: (i) Na+/Cl- or (ii) Na+/K+-dependent cell surface transporters, and (iii) H+-dependent transporters associated with synaptic vesicles. The new insights into neurotransporter diversity provide the means for novel approaches of studying reuptake processes at the molecular level. Current research strategies are focusing on functional mechanisms of substrate translocation and antagonist binding, as well as on molecular regulation of neurotransporter gene expression and on post-translational modification at the neurotransporter protein level. Interesting information will also be derived from the analysis of genomic regulatory elements, as well as from modelling neurotransporter-related disorders and novel therapeutic strategies in genetically engineered animals. Through an improved understanding of the modulation of the function of neurotransporters in the brain, it may be possible to identify the molecular factors underlying both the predisposition to, and the pathogenesis of, psychiatric, neurological and neurodegenerative disorders. Neurotransporters have long been regarded as primary sites of action for tri- and heterocyclic antidepressant drugs in the treatment of a variety of neuropsychiatric conditions. Nevertheless, due to their increasingly appreciated heterogeneity, as well as their specificity for distinct neuronal systems, we are currently witnessing a renaissance of various neurotransmitter reuptake mechanisms as potential targets for novel therapeutic strategies.
Most mRNAs end in a poly(A) tail, the addition of which is catalysed by a poly(A) polymerase in conjunction with a distinct factor that provides specificity for mRNAs. The reaction is dynamic, involving separable initiation, elongation and termination phases. A companion article in next month's TIBS will review the regulation of poly(A) addition and removal during early animal development.
A Na(+)- and Cl(-)-coupled serotonin (5-hydroxytryptamine, 5HT) transporter is expressed on human neuronal, platelet, placental, and pulmonary membranes. The brain 5HT transporter appears to be a principal site of action of therapeutic antidepressants and may mediate behavioral and/or toxic effects of cocaine and amphetamines. Oligonucleotides derived from consensus transporter sequences were used to identify human placental cDNAs highly related to the rat brain 5HT carrier. Transfection of one of these cDNAs into HeLa cells yields a high-affinity (Km = 463 nM), Na(+)- and Cl(-)-dependent 5HT transport activity which can be blocked by selective 5HT transport inhibitors, including paroxetine, fluoxetine, and imipramine, and which is antagonized by cocaine and amphetamine. Sequence analysis reveals a 630-amino acid open reading frame bearing 92% identity to the cloned rat brain 5HT transporter, with identical predicted topological features and conserved sites for posttranslational modifications. Unlike the rodent, where a single mRNA appears to encode 5HT transporters, multiple hybridizing RNAs are observed in human placenta and lung. Somatic cell hybrid and in situ hybridization studies are consistent, however, with a single gene encoding the human 5HT transporter, localized to chromosome 17q11.1-17q12.
Genetic factors have been implicated in the etiology of affective disorders but due to the complex inheritance patterns of these disorders, identification of the responsible gene(s) has so far been unsuccessful. Decreased platelet serotonin (5-HT) transport and reduced binding of imipramine or paroxetine to brain and platelet 5-HT uptake sites/transporters in patients with depression and suicide victims define the 5-HT transporter (5-HTT) as a candidate gene. The primary structure of the 5-HTT was analyzed in 17 patients meeting DSM-III-R diagnostic criteria for major depressive or bipolar disorder and in 4 healthy controls using polymerase chain reaction (PCR-) amplification and sequencing of complementary deoxyribose nucleic acid (cDNA) synthesized from platelet 5-HTT messenger ribose nucleic acid (mRNA). Direct PCR sequencing of the protein coding region failed to reveal changes in the deduced amino acid sequence of the platelet/brain 5-HTT (40,000 base pairs sequence screened), although a conservative single-base substitution representing a silent polymorphism was found. The results provide preliminary evidence that alterations in the primary structure of 5-HTT are not generally involved in the pathogenesis of unipolar depression and manic-depressive illness.
The gene encoding the human serotonin transporter (5-HTT) has been isolated and characterized. The human 5-HTT gene is composed of 14 exons spanning approximately 31 kb. The sequence of all exons including adjacent intronic sequences and a tandem repeat DNA polymorphism (VNTR) has been determined and deposited in the EMBL/GenBank data base with the accession numbers X76753 to X76762. The characterization of 5-HTT gene will aid to advance molecular pharmacologic studies of 5-HT uptake regulation and facilitate investigations of its role in psychiatric disorders.
The characterization and cellular localization of human brain mRNA encoding the serotonin transporter were investigated using northern blot analysis and in situ hybridization histochemistry. In contrast to results from rodent studies, in which single hybridizing mRNAs are detected in brain and periphery, northern analysis of human midbrain raphe tissue revealed the presence of three mRNA species absent from samples prepared from substantia nigra/ventral tegmental area. In situ hybridization studies revealed dense hybridization signal corresponding to serotonin transporter mRNA highly localized to neurons of the dorsal and median raphe nuclei and the caudal linear nucleus. No hybridization signal was observed in neurons of the substantia nigra or locus ceruleus. These findings demonstrate the first anatomical visualization of human brain serotonin transporter gene expression and reveal heterogeneity associated with serotonin transporter transcripts, similar to, but distinct from the pattern of expression visualized in human peripheral tissues.
A cDNA encoding a serotonin transporter (5-HTT) in the human dorsal raphe nucleus was isolated and sequenced using cross-species amplification of human 5-HTT partial cDNA by the polymerase chain reaction (PCR) and the RACE-PCR procedure, designed for rapid amplification of 3' and 5' cDNA ends. The cDNA contains an open reading frame encoding a hydrophobic polypeptide of 630 amino acids with a calculated molecular weight of approximately 70 kDa. The human 5-HTT is approximately 92% homologous to the rat protein but contains an additional consensus phosphorylation site for cAMP-dependent protein kinase recognition located in the cytoplasmic N-terminal region, while a potential protein kinase C phosphorylation site identified in the rat homolog is not conserved in the human 5-HTT. Hydropathicity analysis revealed twelve membrane spanning segments, a topology proposed for other cloned sodium-dependent transporters.
Dysfunctions in serotonergic pathways may underlie several psychiatric disorders. The reuptake of serotonin (5-HT) from synaptic terminals is mediated by a specific transporter (5-HTT). Genetic variation in the gene coding for the 5-HTT protein might be involved in the predisposition to psychiatric disorders. A systematic screening of the whole coding sequence of the 5-HTT gene in mood disorder (MD) and obsessive-compulsive disorder (OCD) patients, as well as in healthy controls, using PCR and denaturing gradient gel electrophoresis (DGGE) revealed the presence of two mutations. The first was in intron 4, and the second was a C-->A transversion leading to an amino-acid exchange (Leu-->Met) in position 255 of the deduced protein sequence. No further occurrence of this substitution was found in an extended sample of patients and controls. Therefore, structural modifications of the 5-HTT gene do not seem to play either a major or minor role in the genetic predisposition to MD or OCD.