An intronic polymorphic domain often associated with susceptibility to affective disorders has allele dependent differential enhancer activity in embryonic stem cells

Genetic polymorphisms in the serotonin, dopamine and opioid pathways influence social attention in rhesus macaques (Macaca mulatta)

Behaviour has a significant heritable component; however, unpicking the variants of interest in the neural circuits and molecular pathways that underpin these has proven difficult. Here, we present a comprehensive analysis of the relationship between known and new candidate genes from identified pathways and key behaviours for survival in 109 adult rhesus macaques (Macaca mulatta). Eight genes involved in emotion were analysed for variation at a total of nine loci. Genetic data were then correlated with cognitive and observational measures of behaviour associated with wellbeing and survival using MCMC-based Bayesian GLMM in R, to account for relatedness within the macaque population. For four loci the variants genotyped were length polymorphisms (SLC6A4 5-hydroxytryptamine transporter length-polymorphic repeat (5-HTTLPR), SLC6A4 STin polymorphism, Tryptophan 5-hydroxylase 2 (TPH2) and Monoamine oxidase A (MAOA)) whilst for the other five (5-hydroxytryptamine receptor 2A (HTR2A), Dopamine Receptor D4 (DRD4), Oxytocin receptor (OXTR), Arginine vasopressin receptor 1A (AVPR1a), Opioid receptor mu(μ) 1 (OPRM1)) SNPs were analysed. STin genotype, DRD4 haplotype and OXTR haplotype were significantly associated with the cognitive and observational measures of behaviour associated with wellbeing and survival. Genotype for 5-HTTLPR, STin and AVPR1a, and haplotype for HTR2A, DRD4 and OXTR were significantly associated with the duration of behaviours including fear and anxiety. Understanding the biological underpinnings of individual variation in negative emotion (e.g., fear and anxiety), together with their impact on social behaviour (e.g., social attention including vigilance for threat) has application for managing primate populations in the wild and captivity, as well as potential translational application for understanding of the genetic basis of emotions in humans.

Serotonin transporter availability in physically aggressive personality disordered patients: associations with trait and state aggression, and response to fluoxetine

RATIONALE

Characterizing the neuroanatomical basis of serotonergic abnormalities in severe, chronic, impulsive aggression will allow for rational treatment selection, development of novel therapeutics, and biomarkers to identify at-risk individuals.

OBJECTIVES

The aim of this study is to identify associations between regional serotonin transporter (5-HTT) availability and trait and state aggression, as well as response to the anti-aggressive effects of fluoxetine.

METHODS

We examined 5-HTT availability using positron emission tomography (PET) imaging with [¹¹C]DASB in personality disordered patients with current physical intermittent explosive disorder (IED; n = 18), and healthy comparison participants (HC; n = 11), in the anterior cingulate cortex (ACC), amygdala (AMY), ventral striatum (VST), and midbrain (MID). After PET imaging, IED patients were treated with fluoxetine 20 mg daily (n = 9) or placebo (n = 6) for 12 weeks. Trait and state aggression, trait callousness, and childhood trauma were assessed.

RESULTS

In IED patients, trait aggression was positively associated with [¹¹C]DASB binding in the ACC and VST; covarying for trait callousness and childhood trauma enhanced these correlations. Baseline state aggression was positively correlated with ACC [¹¹C]DASB in IED patients. Greater baseline VST [¹¹C]DASB binding predicted greater decreases in state aggression with fluoxetine treatment.

CONCLUSIONS

Consistent with prior reports, ACC 5-HTT is related to trait aggression, and adjusting for factors related to proactive (callousness) and reactive (childhood trauma) aggression subtypes further resolves this relationship. Novel findings of the study include a better understanding of the association between regional 5-HTT availability and state aggression, and the involvement of VST 5-HTT with trait aggression, and with the anti-aggressive effects of fluoxetine.

Role of serotonin transporter and receptor gene polymorphisms in treatment response to selective serotonin reuptake inhibitors in major depressive disorder

OBJECTIVE

Significant challenges in the management of major depressive disorder include the lag period from treatment initiation to an evident response, low response rates and unpredictable disparities in outcome between patients. As a large part of these has been linked to genetic mechanisms, we tried to establish a relationship between genes associated with serotonin neurotransmission and outcome to selective serotonin reuptake inhibitor (SSRI) treatment.

METHODS

One hundred and twenty-five patients with moderate to severe depression [at least 15 on the Hamilton Depression (HAM-D) Rating Scale] being started on SSRI were recruited. Those with a reduction of at least 50% from baseline or an absolute score of 7 or less after 8 weeks of treatment were considered as responders. The serotonin transporter linked polymorphic region 5HTTLPR, serotonin transporter intron 2 (STin2) polymorphism and the 5-HT receptor 1A rs6295 polymorphisms were studied in association with outcome.

RESULTS

The l/l genotype of the 5HTTLPR was associated with greater likelihood of response (OR: 4.65, CI: 1.74-12.38, p = 0.003). Patients with the 12/12 repeat variant of the STin2 VNTR polymorphism showed a greater reduction in HAM-D score, compared to patients with the 10/10 genotype (OR: 0.12, CI: 0.03-0.44, p = 0.001). We found no association of the 5HTR1Ars6295 polymorphism with response.

CONCLUSIONS

The 5HTTLPR polymorphism and the SLC6A4 intron 2 polymorphism were associated with treatment response, with the l/l genotype and 12-copy allele showing a tendency towards better outcomes, respectively.

Genes Predisposing to Erectile Dysfunction and Management: A Review

Background: The burden of erectile dysfunction (ED) is rising worldwide due to unresponsiveness of some affected individuals to existing drugs and treatment strategies. Fortunately, improvement in biological techniques has led to the understanding that some cases of the disorder may have a genetic etiology, which, when fully understood, may lead to improved treatment.

Objective: This review articulated established ED candidate genes and pathophysiology to assist researchers and medical practitioners to formulate effective drugs and treatment procedures.

Methods: The Google search engine was used to retrieve relevant information on the topic from reputable academic databases, including PubMed, Medline, Google Scholar, Scopus, and SpringerLink.

Results: The search discovered 10 ED candidate genes, which are SIM1, SLC6A4, 5-HTTLPR, TGFB1, DAT1, MC4R, NOS3, GNB3, AR, and MTHFR. Polymorphisms or mutations in these genes may disrupt erectile activities of the hypothalamus, neurotransmitters such as dopamine, serotonin, and nitric oxide as well as relaxation of penile tissues. Clinical presentations of ED include loss of erection, weak vaginal penetration, premature ejaculation, and anejaculation. Each gene has a distinct mechanism, which, if targeted in the affected may reverse the disorder or reduce the effects.

Conclusion: Some cases of ED are genetic, which, when fully understood, may give an insight into new treatment procedures or improve on the current ones. Medical practitioners are advised to formulate treatment procedures that target the affected gene (s) in individuals.

Differential Relations of Parental Behavior to Children's Early Executive Function as a Function of Child Genotype: A Systematic Review

Child genotype is an important biologically based indicator of sensitivity to the effects of parental behavior on children's executive function (EF) in early childhood, birth to age 5. While evidence for gene × parental behavior interactions on children's early EF is growing, researchers have called the quality of evidence provided by gene × environment interaction studies into question. For this reason, this review comprehensively examined the literature and evaluated the evidence for gene × parental behavior interactions on children's early EF abilities. Psychology and psychiatry databases were searched for published peer-reviewed studies. A total of 18 studies met inclusion criteria. Twenty-nine of 89 (33%) examined interactions were significant. However, a p-curve analysis did not find the significant interactions to be of evidential value. A high rate of false positives, due to the continued use of candidate gene and haplotype measures of child genotype and small sample sizes, likely contributed to the high rate of significant interactions and low evidential value. The use of contemporary molecular genetic measures and larger sample sizes are necessary to advance our understanding of child genotype as a moderator of parental effects on children's EF during early childhood and the biopsychosocial mechanisms underlying children's EF development during this critical period. Without these changes, future research is likely to be stymied by the same limitations as current research.

Association of serotonin system-related genes with homicidal behavior and criminal aggression in a prison population of Pakistani Origin

The serotonin transporter (SLC6A4), 5-HT_2A (HTR2A) and 5-HT_2B (HTR2B) recepter genes, express proteins that are important regulators of serotonin reuptake and signaling, and thereby may contribute to the pathogenesis of aggressive criminal behavior. 370 sentenced murderers in Pakistani prisons and 359 men without any history of violence or criminal delinquency were genotyped for six candidate polymorphisms in SLC6A4, HTR2A and HTR2B genes. An association of higher expressing L/L and L_A/L_A variants of the 5-HTTLPR polymorphism was observed with homicidal behavior (bi-allelic: OR = 1.29, p = 0.016, tri-allelic: OR = 1.32, p = 0.015) and in the murderer group only with response to verbal abuse (OR = 2.11, p = 0.015), but not with other measures of self-reported aggression. L/L and L_A/L_A genotypes of the 5-HTTLPR polymorphism were associated with higher aggression scores on STAX1 scale of aggression compared to lower expressing genotypes (S/S, S/L_G, L_G/L_G) in prison inmates. No associations were apparent for other serotonergic gene polymorphisms analyzed. Using the Braineac and GTEx databases, we demonstrated significant eQTL based functional effects for rs25531 in HTTLPR and other serotonergic polymorphisms analyzed in different brain regions and peripheral tissues. In conclusion, these findings implicate SLC6A4* HTTLPR as a major genetic determinant associated with criminal aggression. Future studies are needed to replicate this finding and establish the biologic intermediate phenotypes mediating this relationship.

Serotonin re-uptake transporter gene polymorphisms are associated with imatinib-induced diarrhoea in chronic myeloid leukaemia patients

Tyrosine kinase inhibitors (TKIs), the treatment of choice for chronic myeloid leukaemia (CML), can cause lower gastrointestinal (GI) toxicity which is manifested as diarrhoea. The mechanisms are not fully understood. The enteroendocrine signalling compound, serotonin (5-HT), is important for regulating peristaltic motion, fluid secretion and visceral hypersensitivity in the GI tract, and has been implicated in diseases such as irritable bowel syndrome. In this study, we have evaluated whether TKI-induced diarrhoea may be related to variation in the serotonin re-uptake transporter (SERT) gene. CML patients with and without diarrhoea on the SPIRIT2 trial (imatinib, n = 319; and dasatinib, n = 297) were genotyped for the promoter 5-HTTLPR, intron 2 VNTR and rs25531 polymorphisms by PCR-based methods. Diarrhoea was more prevalent in imatinib, than in dasatinib treated patients (P = 0.015), which when stratified by gender was seen to be driven by female patients (P = 0.036). Logistic regression analysis revealed that age, and the dominant HTTLPR with the rs25531 single nucleotide polymorphism (SNP) model, explained the occurrence of diarrhoea in ~10% of imatinib-treated female CML patients. These data suggest SERT polymorphisms influence imatinib-induced diarrhoea but not that of dasatinib.

Associations of the serotonin transporter promoter polymorphism (5-HTTLPR) with bipolar disorder and treatment response: A systematic review and meta-analysis

BACKGROUND

Associations of the serotonin transporter promoter polymorphism (5-HTTLPR) with bipolar disorder (BPD) and treatment response in bipolar patients were not conclusive. This study not only assessed the association between the 5-HTTLPR and BPD with accumulating relevant studies, but also in the first time evaluated the effect of the 5-HTTLPR on both anti-depressive and anti-manic treatment responses in bipolar patients.

METHODS

PubMed, Embase, PsycINFO, Cochrane Library and Cochrane Control Trials databases were systematically searched before February 2017. This meta-analysis followed the PRISMA guidelines.

RESULTS

A total of 32 population-based studies (5567 cases and 6993 controls) and 9 family-based studies (837 trios) were finally screened out and statistically joined into a single meta-analysis that revealed an association between S allele and an increased risk of BPD (OR = 1.06, p = .038). Pooled analysis of the 32 population-based studies indicated an association of S-carrier genotypes with an increased risk of BPD (OR = 1.10, p = .029). Meanwhile, the association remained significant in Caucasians (OR = 1.15, p = .004), which could provide an enough power (88%) to detect a significant association. Regarding the treatment response studies, 6 studies reporting the relationship of the 5-HTTLPR in anti-depressive remission rate (1034 patients) and 7 studies reporting in response rate (1098 patients) were included for pooled analyses. We observed a significant association of S-carrier genotypes with a reduced anti-depressive remission rate (OR = 0.64, p = .006) but not with anti-depressive response rate. The association between the 5-HTTLPR with anti-manic response rate was not observed in the included 6 studies (676 patients).

CONCLUSIONS

The present study supported the presence of a marginal but detectable effect of the 5-HTTLPR on susceptibility to BPD. Moreover, the detected association in Caucasian was statistically reliable. Besides, the 5-HTTLPR was identified as a useful predictor for anti-depressive remission but not for anti-depressive or anti-manic response.

Multifaceted Regulations of the Serotonin Transporter: Impact on Antidepressant Response

Serotonin transporter, SERT (SLC64A for solute carrier family 6, member A4), is a twelve transmembrane domain (TMDs) protein that assumes the uptake of serotonin (5-HT) through dissipation of the Na⁺ gradient established by the electrogenic pump Na/K ATPase. Abnormalities in 5-HT level and signaling have been associated with various disorders of the central nervous system (CNS) such as depression, obsessive-compulsive disorder, anxiety disorders, and autism spectrum disorder. Since the 50s, SERT has raised a lot of interest as being the target of a class of antidepressants, the Serotonin Selective Reuptake Inhibitors (SSRIs), used in clinics to combat depressive states. Because of the refractoriness of two-third of patients to SSRI treatment, a better understanding of the mechanisms regulating SERT functions is of priority. Here, we review how genetic and epigenetic regulations, post-translational modifications of SERT, and specific interactions between SERT and a set of diverse partners influence SERT expression, trafficking to and away from the plasma membrane and activity, in connection with the neuronal adaptive cell response to SSRI antidepressants.

Association between the SLC6A4 gene and schizophrenia: an updated meta-analysis

BACKGROUND

In order to explore the association between the SLC6A4 gene and the risk of schizophrenia, an updated meta-analysis was conducted using a total of 46 scientific articles.

METHODS

Through a literature search, papers studied included 35 articles on serotonin-transporter-linked polymorphic region (5-HTTLPR) with 8,752 cases and 10,610 controls, 17 articles on second intron variable number of tandem repeats with 7,284 cases and 8,544 controls, four studies on rs1042173 with 1,351 cases and 2,101 controls, and four studies on rs140700 with 1,770 cases and 2,386 controls. Pooled, subgroup, and sensitivity analyses were performed, and the results were visualized by forest and funnel plots.

RESULTS

An association between 5-HTTLPR and the risk of schizophrenia was not found, except for an Indian subgroup analysis (P_z =0.014, OR =1.749, 95% CI =1.120-2.731). A 10 repeats/12 repeats (10R/12R) genotype was a protective factor against schizophrenia (P_z =0.020, OR =0.789, 95% CI =0.646-0.963), but a 12R/12R genotype was a risk factor for schizophrenia (P_z =0.004, OR =1.936, 95% CI =1.238-3.029) in the pooled analyses. In Caucasians, a GG genotype of rs1042173 may be a risk factor for schizophrenia (P_z =0.006, OR =1.299, 95% CI =1.079-1.565). No association was found between rs140700 and the risk for schizophrenia.

CONCLUSION

Through meta-analysis, we were able to gain insight into previously reported associations between SLC6A4 polymorphism and schizophrenia.

Appetitive and reactive aggression are differentially associated with the STin2 genetic variant in the serotonin transporter gene

Appetitive aggression is a sub-category of instrumental aggression, characterised by the primary intrinsic enjoyment of aggressive activity. Aggression is heritable, and serotonergic and monoaminergic neurotransmitter systems have been found to contribute to the underlying molecular mechanisms. The aim of this study was to investigate the role that genetic variants in the serotonin transporter (SLC6A4) and monoamine oxidase A (MAOA) genes play in the aetiology of appetitive aggression in South African Xhosa males (n = 290). SLC6A4 5-HTTLPR, rs25531, and STin2 variants, as well as MAOA-uVNTR were investigated for their association with levels of appetitive aggression using Poisson regression analysis. The STin2 VNTR12 allele was found to be associated with increased levels of appetitive aggression (p = 0.003), but with decreased levels of reactive aggression (p = 7 × 10^-5). This study is the first to investigate genetic underpinnings of appetitive aggression in a South African population, with preliminary evidence suggesting that SCL6A4 STin2 variants play a role in its aetiology, and may also be important in differentiating between appetitive and reactive aggression. Although the results require replication, they shed some preliminary light on the molecular dichotomy that may underlie the two forms of aggression.

Association of Polymorphisms of Serotonin Transporter (5HTTLPR) and 5-HT2C Receptor Genes with Criminal Behavior in Russian Criminal Offenders

BACKGROUND

Human aggression is a heterogeneous behavior with biological, psychological, and social backgrounds. As the biological mechanisms that regulate aggression are components of both reward-seeking and adversity-fleeing behavior, these phenomena are difficult to disentangle into separate neurochemical processes. Nevertheless, evidence exists linking some forms of aggression to aberrant serotonergic neurotransmission. We determined possible associations between 6 serotonergic neurotransmission-related gene variants and severe criminal offenses.

METHODS

Male Russian prisoners who were convicted for murder (n = 117) or theft (n = 77) were genotyped for variants of the serotonin transporter (5HTTLPR), tryptophan hydroxylase, tryptophan-2,3-dioxygenase, or type 2C (5-HT2C) receptor genes and compared with general-population male controls (n = 161). Prisoners were psychologically phenotyped using the Buss-Durkee Hostility Inventory and the Beck Depression Inventory.

RESULTS

No differences were found between murderers and thieves either concerning genotypes or concerning psychological measures. Comparison of polymorphism distribution between groups of prisoners and controls revealed highly significant associations of 5HTTLPR and 5-HTR2C (rs6318) gene polymorphisms with being convicted for criminal behavior.

CONCLUSIONS

The lack of biological differences between the 2 groups of prisoners indicates that the studied 5HT-related genes do not differentiate between the types of crimes committed.

Association analysis of SLC6A4 and HTR2A genes with obsessive-compulsive disorder: Influence of the STin2 polymorphism

BACKGROUND

Obsessive-Compulsive Disorder (OCD) is a complex and chronic disorder characterized by recurrent thoughts and/or repetitive behaviors. Given the potent anti-obsessional effects of the so-called serotonin reuptake inhibitors, genes related to serotonergic system may be well implicated in the etiopathogenesis of OCD. The gene encoding the serotonin transporter (SLC6A4), which shows a variable number of tandem repeat (VNTR) polymorphism in intron 2 (STin2), have been previously associated with OCD. Additionally, the serotonin 2A receptor gene (HTR2A) has two polymorphisms (A-1438G - rs6311, and T102C - rs6313), which have also been overrepresented among OCD patients. Therefore, the aim of this study is to evaluate the association of these three polymorphisms with OCD, through the examination of potential sources of heterogeneity in previous studies including age of onset, sex and symptom dimensions.

METHODS

Polymorphisms were genotyped by Polymerase Chain Reaction (PCR) in a sample of 203 OCD patients and 205 healthy controls from Brazil.

RESULTS

Although we did not observe any statistically significant association between the HTR2A gene polymorphisms and OCD or its clinical features, SLC6A4 STin2 polymorphism was significantly more common among OCD patients as compared to health controls. Further, a significant association between the STin2.12 allele and OCD, as well as a dominant effect of the STin2.12 allele in OCD was seen. Of note, late-onset (>18years) OCD was significantly more often seen in association with homozygosis for STin2.12 allele. No significant associations were observed with different OCD symptom dimensions.

CONCLUSION

Our results indicate an important influence of the STin2 polymorphism in OCD, but more studies are warranted to confirm these results.

Serotonin transporter gene polymorphisms may be associated with poststroke neurological recovery after escitalopram use

OBJECTIVE

Selective serotonin reuptake inhibitors (SSRIs) putatively improve neurological recovery after stroke. We aimed to investigate whether serotonin transporter (SERT) gene polymorphisms are related to the responsiveness to SSRIs in the poststroke neurological recovery.

METHODS

This was a post hoc analysis of the EMOTION study (ClinicalTrials.gov NCT01278498), a randomised, placebo-controlled, double-blind trial examining the efficacy of escitalopram on emotional and neurological disturbances after acute stroke. Patients with no/minimal disability initially (modified Rankin Scale (mRS) 0-1) were excluded. Of the participants, 301 underwent genetic studies of the STin2 (a variable number tandem repeat (VNTR) in intron 2) (STin2 12/10 and STin2 12/12 genotypes) and 5-HTTLPR (a variable-length repeat in the promoter region) polymorphisms of SERT. We explored whether neurological function (National Institutes of Health Stroke Scale (NIHSS) score and mRS) at 3 months would differ according to SERT polymorphisms within each treatment arm (escitalopram and placebo).

RESULTS

Among the escitalopram users (n=159), neurological function in subjects with STin2 12/10 (n=29) improved significantly more than that in STin2 12/12 carriers (n=130) at 3 months. After adjusting for age, initial NIHSS and depression, STin2 12/10 independently predicted a good clinical outcome (mRS 0-1) (OR 2.99, 95% CI 1.04 to 8.58) at 3 months. However, differences between STin2 polymorphisms were not shown in the placebo group (n=142). 5-HTTLPR polymorphisms were not associated with neurological recovery in any treatment group.

CONCLUSION

STin2 VNTR polymorphisms may be associated with poststroke neurological recovery after SSRI therapy. Further studies are needed to identify the role of serotonin in neurological recovery after stroke.

Blood-based biomarkers predicting response to antidepressants

Major depressive disorder is a common, serious and in some cases, life-threatening condition and affects approximately 350 million people globally. Although there is effective treatment available for it, more than 50% of the patients fail to respond to the first antidepressant they receive. The selection of a distinct treatment is still exclusively based on clinical judgment without incorporating lab-derived objective measures. However, there is growing evidence of biomarkers that it helps to improve diagnostic processes and treatment algorithms. Here genetic markers and blood-based biomarkers of the monoamine pathways, inflammatory pathways and the hypothalamic-pituitary-adrenal (HPA) axis are reviewed. Promising findings arise from studies investigating inflammatory pathways and immune markers that may identify patients suitable for anti-inflammatory based treatment regimes. Next, an early normalization of a disturbed HPA axis or depleted neurotrophic factors may predict stable treatment response. Genetic markers within the serotonergic system may identify patients who are vulnerable because of stressful life events, but evidence for guiding treatment regimes still is inconsistent. Therefore, there is still a great need for studies investigating and validating biomarkers for the prediction of treatment response to facilitate the treatment selection and shorten the time to remission and thus provide personalized medicine in psychiatry.

Resequencing three candidate genes discovers seven potentially deleterious variants susceptibility to major depressive disorder and suicide attempts in Chinese

BACKGROUND

To date almost 200 genes were found to be associated with major depressive disorder (MDD) or suicide attempts (SA), but very few genes were reported for their molecular mechanisms. This study aimed to find out whether there were common or rare variants in three candidate genes altering the risk for MDD and SA in Chinese.

METHODS

Three candidate genes (HOMER1, SLC6A4 and TEF) were chosen for resequencing analysis and association studies as they were reported to be involved in the etiology of MDD and SA. Following that, bioinformatics analyses were applied on those variants of interest.

RESULTS

After resequencing analysis and alignment for the amplicons, a total of 34 common or rare variants were found in the randomly selected 36 Hong Kong Chinese patients with both MDD and SA. Among those, seven variants show potentially deleterious features. Rs60029191 and a rare variant located in regulatory region of the HOMER1 gene may affect the promoter activities through interacting with predicted transcription factors. Two missense mutations existed in the SLC6A4 coding regions were firstly reported in Hong Kong Chinese MDD and SA patients, and both of them could affect the transport efficiency of SLC6A4 to serotonin. Moreover, a common variant rs6354 located in the untranslated region of this gene may affect the expression level or exonic splicing of serotonin transporter. In addition, both of a most studied polymorphism rs738499 and a low-frequency variant in the promoter region of the TEF gene were found to be located in potential transcription factor binding sites, which may let the two variants be able to influence the promoter activities of the gene.

CONCLUSIONS

This study elucidated the potentially molecular mechanisms of the three candidate genes altering the risk for MDD and SA. These findings implied that not only common variants but rare variants could make contributions to the genetic susceptibility to MDD and SA in Chinese.

Association of STin2 VNTR Polymorphism of Serotonin Transporter Gene with Lifelong Premature Ejaculation: A Case-Control Study in Han Chinese Subjects

Background

The STin2 VNTR polymorphism has a variable number of tandem repeats in intron 2 of the serotonin transporter gene. We aimed to explore the relationship between STin2 VNTR polymorphism and lifelong premature ejaculation (LPE).

Material/Methods

We recruited a total of 115 outpatients who complained of ejaculating prematurely and who were diagnosed as LPE, and 101 controls without PE complaint. Allelic variations of STin2 VNTR were genotyped using PCR-based technology. We evaluated the associations between STin2 VNTR allelic and genotypic frequencies and LPE, as well as the intravaginal ejaculation latency time (IELT) of different STin2 VNTR genotypes among LPE patients.

Results

The patients and controls did not differ significantly in terms of any characteristic except age. A significantly higher frequency of STin2.12/12 genotype was found among LPE patients versus controls (P=0.026). Frequency of patients carrying at least 1 copy of the 10-repeat allele was significantly lower compared to the control group (28.3% vs. 41.8%, OR=0.55; 95%CI=0.31–0.97, P=0.040). In the LPE group, the mean IELT showed significant difference in STin2.12/12 genotype when compared to those with STin2.12/10 and STin2.10/10 genotypes. The mean IELT in10-repeat allele carriers was 50% longer compared to homozygous carriers of the STin2.12 allele.

Conclusions

Our results indicate the presence of STin2.10 allele is a protective factor for LPE. Men carrying the higher expression genotype STin2. 12/12 have shorter IELT than 10-repeat allele carriers.

A polymorphic minisatellite region of BORIS regulates gene expression and its rare variants correlate with lung cancer susceptibility

Aberrant expression of BORIS/CTCFL (Brother of the Regulator of Imprinted Sites/CTCF-like protein) is reported in different malignancies. In this study, we characterized the entire promoter region of BORIS/CTCFL, including the CpG islands, to assess the relationship between BORIS expression and lung cancer. To simplify the construction of luciferase reporter cassettes with various-sized portions of the upstream region, genomic copies of BORIS were isolated using TAR cloning technology. We analyzed three promoter blocks: the GATA/CCAAT box, the CpG islands and the minisatellite region BORIS-MS2. Polymorphic minisatellite sequences were isolated from genomic DNA prepared from the blood of controls and cases. Of the three promoter blocks, the GATA/CCAAT box was determined to be a critical element of the core promoter, while the CpG islands and the BORIS-MS2 minisatellite region were found to act as regulators. Interestingly, the polymorphic minisatellite region BORIS-MS2 was identified as a negative regulator that repressed the expression levels of luciferase reporter cassettes less effectively in cancer cells compared with normal cells. We also examined the association between the size of BORIS-MS2 and lung cancer in a case–control study with 590 controls and 206 lung cancer cases. Rare alleles of BORIS-MS2 were associated with a statistically significantly increased risk of lung cancer (odds ratio, 2.04; 95% confidence interval, 1.02–4.08; and P=0.039). To conclude, our data provide information on the organization of the BORIS promoter region and gene regulation in normal and cancer cells. In addition, we propose that specific alleles of the BORIS-MS2 region could be used to identify the risk for lung cancer.

Association of HOMER1 rs2290639 with suicide attempts in Hong Kong Chinese and the potentially functional role of this polymorphism

OBJECTIVE

Animal evidence and genetic studies suggest that HOMER1 (homer homolog 1) is involved in the etiology of suicidal behavior and major depression disorder (MDD). However, most of genetic studies were performed in Caucasians and the potentially functional role of associated polymorphisms in HOMER1 was seldom reported. The purpose of this study was to investigate the association of a HOMER1 polymorphism rs2290639 with suicide attempts (SA) and MDD in Hong Kong Chinese, and then briefly elucidate the potentially functional role of the associated polymorphism.

METHODS

NEO personality inventory, impulsiveness and depression rating scales were completed by the subjects. The association studies of HOMER1 rs2290639 with SA or MDD were performed by case-control association studies. The bioinformatics analyses were adapted to predict potential transcription factors binding sites for the associated polymorphism.

RESULTS

The association studies and meta-analysis suggested that the HOMER1 rs2290639 was significantly associated with susceptibility to SA but seemed not to be associated with MDD in Hong Kong Chinese. This polymorphism might affect the transcription of the HOMER1 gene through interacting with a reliable transcription factor as found by three of four bioinformatics tools. In addition, close correlations between impulsiveness and NEO personality five factors were found in SA and MDD patients, which provide a possible way to assess the impulsiveness of patients through subjects' personality profiles for Hong Kong Chinese.

CONCLUSIONS

The HOMER1 rs2290639 polymorphism was significantly associated with susceptibility to SA in Hong Kong Chinese affected by psychiatric disorders, which might be explained by the potentially functional role of this polymorphism.

An animal model of detrusor overactivity induced by depression

INTRODUCTION

Depression is frequently found in patients suffering from overactive bladder. The aim of the study was to verify whether the 13-cis-retinoic acid, a synthetic retinoid used in the treatment of acne, which was proven to induce depressive changes in both humans and animals, can cause detrusor overactivity symptoms in conscious rats.

METHODS

In order to assess the 13-cis-retinoic acid impact on the behavioural parameters, after 6weeks of intraperitoneal administration of retinoid in a dose of 1mg/kg/day, a forced swim test and cystometry were performed, and the locomotor activity of animals was assessed. The control group received a mixture of DMSO and physiological saline at a 1:1 ratio.

RESULTS

13-cis-retinoic acid caused cystometric parameter changes analogous to those observed in people with a urodynamic diagnosis of detrusor overactivity. The retinoid caused also an extension of the immobility time in the forced swim test which is consistent with increased depression-related behaviour, with no impact on the locomotor activity of rats. The intravenous administration of solifenacin succinate in a single dose of 0.03mg/kg turned out to reverse changes in the cystometric parameters modified by 13-cis-retinoic acid treatment. The histopathological analysis of bladders did not show any lesions in the upper layer of the umbrella cells, urothelium or muscles. The retinoid concentration level achieved in the animals tested turned out to be identical to that occurring in humans.

DISCUSSION

13-cis-retinoic acid can induce detrusor overactivity symptoms that are reversed by solifenacin succinate.

Association of serotonin transporter gene (5HTT) polymorphism and juvenile myoclonic epilepsy: a case-control study

Serotonin levels might alter susceptibility to seizures. Serotonin transporter (5HTT) gene polymorphisms were found to be associated with some forms of epilepsy. Here, we attempted to examine an association between 5HTT VNTR allele variants in a serotonin transporter gene and epileptogenesis in juvenile myoclonic epilepsy (JME) cases. We conducted a case-control candidate gene study evaluating the frequencies of 5HTT VNTR allele variants using SYBR green real-time PCR with melting curve analysis in JME patients and healthy subjects. Forty patients with JME were selected from the Epilepsy Outpatient Clinic of Kasr Al Ainy Hospital, Cairo University, who had been classified according to the electroclinical classification of the ILAE. The control group consisted of 40 healthy Egyptian subjects. The less efficient transcriptional genotypes for 5-HTT polymorphisms were more frequent in JME patients (OR 9.33, CI 2.85-30.60; p value < 0.001). In our study we detected an association between the presence of 5-HTTVNTR with less transcriptional efficient genotypes and JME, which suggests that modulation of the serotoninergic system might be indicated in epileptogenesis in JME.

Polymorphisms of serotonin neurotransmission and their effects on antipsychotic drug action

The receptor pharmacology of many antipsychotic drugs includes actions at various serotonin (5-hydroxytryptamine [5-HT]) receptors. The 5-HT neurotransmitter system is thought to be involved in many of the consequences of treatment with antipsychotic drugs, including both symptom response, primarily of negative and depressive symptoms, and adverse effects, notably extrapyramidal side effects and weight gain. There is substantial interindividual variability in these drug effects, to which genetic variability contributes. We review here the influence of functional polymorphisms in genes associated with 5-HT function, including the various processes of neurotransmitter synthesis, receptors, transporters and metabolism, on the clinical response to, and adverse effects of, antipsychotic drugs. The relatively young field of epigenetics also contributes to the variability of 5-HT-related genes in influencing drug response. Several of these findings inform our understanding of the mechanisms of antipsychotic drug action, and also provide the opportunity for the development of genetic testing for personalized medicine.

Serotonin mediated immunoregulation and neural functions: Complicity in the aetiology of autism spectrum disorders

Serotonergic system has long been implicated in the aetiology of autism spectrum disorders (ASD), since platelet hyperserotonemia is consistently observed in a subset of autistic patients, who respond well to selective serotonin reuptake inhibitors. Apart from being a neurotransmitter, serotonin functions as a neurotrophic factor directing brain development and as an immunoregulator modulating immune responses. Serotonin transporter (SERT) regulates serotonin level in lymphoid tissues to ensure its proper functioning in innate and adaptive responses. Immunological molecules such as cytokines in turn regulate the transcription and activity of SERT. Dysregulation of serotonergic system could trigger signalling cascades that affect normal neural-immune interactions culminating in neurodevelopmental and neural connectivity defects precipitating behavioural abnormalities, or the disease phenotypes. Therefore, we suggest that a better understanding of the cross talk between serotonergic genes, immune systems and serotonergic neurotransmission will open wider avenues to develop pharmacological leads for addressing the core ASD behavioural deficits.

Lineage specific evolution of the VNTR composite retrotransposon central domain and its role in retrotransposition of gibbon LAVA elements

Background

VNTR (Variable Number of Tandem Repeats) composite retrotransposons - SVA (SINE-R-VNTR-Alu), LAVA (LINE-1-Alu-VNTR-Alu), PVA (PTGR2-VNTR-Alu) and FVA (FRAM-VNTR-Alu) - are specific to hominoid primates. Their assembly, the evolution of their 5’ and 3’ domains, and the functional significance of the shared 5’ Alu-like region are well understood. The central VNTR domain, by contrast, has long been assumed to represent a more or less random collection of 30-50 bp GC-rich repeats. It is only recently that it attracted attention in the context of regulation of SVA expression.

Results

Here we provide evidence that the organization of the VNTR is non-random, with conserved repeat unit (RU) arrays at both the 5’ and 3’ ends of the VNTRs of human, chimpanzee and orangutan SVA and gibbon LAVA. The younger SVA subfamilies harbour highly organized internal RU arrays. The composition of these arrays is specific to the human/chimpanzee and orangutan lineages, respectively. Tracing the development of the VNTR through evolution we show for the first time how tandem repeats evolve within the constraints set by a functional, non-autonomous non-LTR retrotransposon in two different families - LAVA and SVA - in different hominoid lineages. Our analysis revealed that a microhomology-driven mechanism mediates expansion/contraction of the VNTR domain at the DNA level.

Elements of all four VNTR composite families have been shown to be mobilized by the autonomous LINE1 retrotransposon in trans. In case of SVA, key determinants of mobilization are found in the 5’ hexameric repeat/Alu-like region. We now demonstrate that in LAVA, by contrast, the VNTR domain determines mobilization efficiency in the context of domain swaps between active and inactive elements.

Conclusions

The central domain of VNTR composites evolves in a lineage-specific manner which gives rise to distinct structures in gibbon LAVA, orangutan SVA, and human/chimpanzee SVA. The differences observed between the families and lineages are likely to have an influence on the expression and mobilization of the elements.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1543-z) contains supplementary material, which is available to authorized users.

Characterization of a REST-Regulated Internal Promoter in the Schizophrenia Genome-Wide Associated Gene MIR137

MIR137 has been identified as a candidate gene for schizophrenia from genome-wide association studies via association with an intronic single nucleotide polymorphism (SNP), rs1625579. The location of the SNP suggests one mechanism in which transcriptional or posttranscriptional regulation of miR-137 expression could underlie schizophrenia. We identified and validated a novel promoter of the MIR137 gene adjacent to miR-137 itself which can direct the expression of distinct mRNA isoforms encoding miR-137. Analysis of both endogenous gene expression and reporter gene assays determined that this internal promoter is regulated by repressor element-1 silencing transcription factor (REST), which has previously been associated with pathways linked to schizophrenia. Distinct isoforms of REST mediate differential expression at this locus, suggesting the relative levels of these isoforms are important for miR-137 expression profiles. The internal promoter contains a variable number tandem repeat (VNTR) domain adjacent to the pre-miR-137 sequence. The reporter gene activity directed by this promoter was modified by the genotype of the VNTR. Differential expression was also observed in response to cocaine, which is known to regulate the REST pathway in SH-SY5Y cells. Our data support the hypothesis that a "gene × environment" interaction could modify the level of miR-137 expression via this internal promoter and that the genotype of the VNTR could modulate transcriptional responses. We demonstrate that this promoter region is not in disequilibrium with rs1625579 and therefore would supply a distinct pathway to potentially alter miR-137 levels in response to environmental cues.

SLC6A4 markers modulate platelet 5-HT level and specific behaviors of autism: a study from an Indian population

Presence of platelet hyperserotonemia and effective amelioration of behavioral dysfunctions by selective serotonin reuptake inhibitors (SSRI) in autism spectrum disorders (ASD) indicate that irregularities in serotonin (5-HT) reuptake and its homeostasis could be the basis of behavioral impairments in ASD patients. SLC6A4, the gene encoding serotonin transporter (SERT) is considered as a potential susceptibility gene for ASD, since it is a quantitative trait locus for blood 5-HT levels. Three functional polymorphisms, 5-HTTLPR, STin2 and 3'UTR-SNP of SLC6A4 are extensively studied for possible association with the disorder, with inconclusive outcome. In the present study, we investigated association of these polymorphisms with platelet 5-HT content and symptoms severity as revealed by childhood autism rating scale in ASD children from an Indian population. Higher 5-HT level observed in ASD was highly significant in children with heterozygous and homozygous genotypes comprising of minor alleles of the markers. Quantitative transmission disequilibrium test demonstrated significant genetic effect of STin2 allele as well as STin2/3'UTR-SNP and 5-HTTLPR/3'UTR-SNP haplotypes on 5-HT levels, but no direct association with overall CARS score and ASD phenotype. Significant genetic effect of the markers on specific behavioral phenotypes was observed for various sub-phenotypes of CARS in quantitative trait analysis. Even though the 5-HT level was not associated with severity of behavioral CARS score, a significant negative relationship was observed for 5-HT levels and level and consistency of intellectual response and general impression in ASD children. Population-based study revealed higher distribution of the haplotype 10/G of STin2/3'UTR-SNP in male controls, suggesting protective effect of this haplotype in male cases. Overall results of the study suggest that SLC6A4 markers have specific genetic effect on individual ASD behavioral attributes, might be through the modulation of 5-HT content.

Possible Association between Serotonin Transporter Gene Polymorphism and Suicide Behavior in Major Depressive Disorder

OBJECTIVE

The serotonin transporter (5-HTT) genes are major candidate genes for modulating the suicidal behavior. We investigated the association between serotonin transporter polymorphisms and suicidal behavior in patients with major depressive disorder (MDD).

METHODS

Serotonin transporter intron 2 VNTR polymorphism (5-HTTVNTR) and serotonin transporter linked polymorphic region polymorphism (5-HTTLPR) were analyzed in 132 depressed patients with suicidal attempt as well as in 122 normal controls. Hamilton's 17-item Depression Rating Scale (HDRS), the Risk-Rescue rating system (RRR) and the Lethality Suicide Attempt Rating Scale updated (LSARS-II) were assessed for the depressed patients.

RESULTS

Although not statistically significant, a trend was found such that the 10/10 and 10/12 alleles of 5-HTTVNTR were more common in suicidal subjects than in control subjects. Comparing allele frequency, those with a 10 allele or 10 allele carriers were higher in suicidal subjects than in control subjects. No difference was noted in 5-HTTLPR genotypes and haplotype distribution between the suicidal subjects and control subjects. The RRR scores in subjects with the 10/10 5-HTTVNTR genotype or 10 5-HTTVNTR allele were significantly lower than those in subjects with other genotypes.

CONCLUSION

These results show the possibility that 10 allele of 5-HTTVNTR is related to suicidal behavior in the suicidal subjects with MDD and suggest that 12 allele of 5-HTTVNTR might be related to more lethality in the suicidal subjects with MDD.

Specific and common genes implicated across major mental disorders: a review of meta-analysis studies

Major efforts have been directed at family-based association and case-control studies to identify the involvement of candidate genes in the major disorders of mental health. What remains unknown is whether candidate genes are associated with multiple disorders via pleiotropic mechanisms, and/or if other genes are specific to susceptibility for individual disorders. Here we undertook a review of genes that have been identified in prior meta-analyses examining specific genes and specific mental disorders that have core disruptions to emotional and cognitive function and contribute most to burden of illness- major depressive disorder (MDD), anxiety disorders (AD, including panic disorder and obsessive compulsive disorder), schizophrenia (SZ) and bipolar disorder (BD) and attention deficit hyperactivity disorder (ADHD). A literature review was conducted up to end-March 2013 which included a total of 1519 meta-analyses across 157 studies reporting multiple genes implicated in one or more of the five disorders studied. A total of 134 genes (206 variants) were identified as significantly associated risk variants for MDD, AD, ADHD, SZ or BD. Null genetic effects were also reported for 195 genes (426 variants). 13 genetic variants were shared in common between two or more disorders (APOE e4, ACE Ins/Del, BDNF Val66Met, COMT Val158Met, DAOA G72/G30 rs3918342, DAT1 40-bp, DRD4 48-bp, SLC6A4 5-HTTLPR, HTR1A C1019G, MTHR C677T, MTHR A1298C, SLC6A4 VNTR and TPH1 218A/C) demonstrating evidence for pleiotrophy. Another 12 meta-analyses of GWAS studies of the same disorders were identified, with no overlap in genetic variants reported. This review highlights the progress that is being made in identifying shared and unique genetic mechanisms that contribute to the risk of developing several major psychiatric disorders, and identifies further steps for progress.

New evidence of heterogeneity in social anxiety disorder: defining two qualitatively different personality profiles taking into account clinical, environmental and genetic factors

PURPOSE

To study qualitatively different subgroups of social anxiety disorder (SAD) based on harm avoidance (HA) and novelty seeking (NS) dimensions.

METHOD

One hundred and forty-two university students with SAD (SCID-DSM-IV) were included in the study. The temperament dimensions HA and NS from the Cloninger's Temperament and Character Inventory were subjected to cluster analysis to identify meaningful subgroups. The identified subgroups were compared for sociodemographics, SAD severity, substance use, history of suicide and self-harm attempts, early life events, and two serotonin transporter gene polymorphisms (5-HTTLPR and STin2.VNTR).

RESULTS

Two subgroups of SAD were identified by cluster analysis: a larger (61% of the sample) inhibited subgroup of subjects with "high-HA/low-NS", and a smaller (39%) atypical impulsive subgroup with high-moderate HA and NS. The two groups did not differ in social anxiety severity, but did differ in history of lifetime impulsive-related-problems. History of suicide attempts and self-harm were as twice as frequent in the impulsive subgroup. Significant differences were observed in the pattern of substance misuse. Whereas subjects in the inhibited subgroup showed a greater use of alcohol (P=0.002), subjects in the impulsive subgroup showed a greater use of substances with a high-sensation-seeking profile (P<0.001). The STin2.VNTR genotype frequency showed an inverse distribution between subgroups (P=0.005).

CONCLUSIONS

Our study provides further evidence for the presence of qualitatively different SAD subgroups and the propensity of a subset of people with SAD to exhibit impulsive, high-risk behaviors.

Genetic determinants of selective serotonin reuptake inhibitor related sexual dysfunction

Sexual dysfunction is a troubling obstacle for individuals being treated for depression and can be caused by both depressive symptoms as well as antidepressant drugs. Selective serotonin reuptake inhibitors (SSRIs) represent a class of antidepressants commonly associated with sexual dysfunction, even after symptomatic improvement. Candidate gene studies have identified associations between sexual dysfunction and altered SSRI pharmacokinetics or to the neurotransmitter systems affected by depression and SSRI treatment. The multifactorial nature of this phenotype and study heterogeneity are currently limitations to the translation of these findings to clinical use. Larger, prospective studies of genetic-guided antidepressant selection may help to clarify the clinical utility of pharmacogenetics in minimizing sexual side effects.

Influence of social environment on loneliness in older adults: Moderation by polymorphism in the CRHR1

OBJECTIVE

Both adverse social environments and genetic factors contribute to loneliness in old age. Mixed findings between older adults' social relations with their children and their levels of loneliness suggested that a gene × social environment interaction may be operating. We examine whether the effects of infrequent contact with children and low levels of perceived social support from children on loneliness in older adults are moderated by two candidate single nucleotide polymorphisms (i.e., rs1876831 and rs242938) in the corticotrophin releasing hormone receptor 1 (CRHR1) gene.

DESIGN

This was a longitudinal observational study.

SETTING

and

PARTICIPANTS

A population-based sub-sample of 1,374 community-dwelling older adults aged 65 years and older was examined from both the 2003-2004 and 2006-2007 English Longitudinal Study of Aging assessments.

MEASUREMENTS

Our main outcome measure is loneliness, which was assessed by four items extracted from the ULCA loneliness scale.

RESULTS

Compared with older adults carrying the CT/TT genotypes, individuals homozygous for the C allele of rs1876831 reported higher levels of loneliness in the context of infrequent social contact with children and lower levels of perceived social support from children. No gene × social environment interactions were found for loneliness between rs242938 and an adverse social environment related to children.

CONCLUSIONS

This study provides the first evidence in humans that the CRHR1 gene interacts with exposure to a negative social environment to predict loneliness in older adults.

Treatment-resistant schizophrenia and DAT and SERT polymorphisms

One fifth to one third of all patients diagnosed with schizophrenia are resistant to drug treatment, which makes it a major clinical challenge. Genetic studies have focused on the association between treatment resistant schizophrenia (TRS) and a number of candidate genes, including serotonin and dopamine system genes. We explored associations between carefully characterized TRS and DAT-VNTR, SERT-PR and SERT-in2 polymorphisms. There were 173 patients enrolled in the study that were clinically evaluated using Positive and Negative Syndrome Scale and Clinical Global Impressions Scales and divided into two groups based on treatment resistance (92 patients in TRS group). Patients with a combination of SERT-in2 ll and DAT 9/10, 9/11, 9/9 and 6/6 genotypes were more likely to have TRS, compared to those with 10/10 or 10/12 genotype (OR=5.1; 95% CI=1.6-16.8). In the group of patients with DAT 10/10 or 10/12 genotype, those who also shared SERT-in2 ls or ss genotype were more likely to have TRS, compared to ll genotype carriers (OR=2.7; 95% CI=1.0-7.0). The model in which interaction between SERT-in2 and DAT polymorphisms is linked to TRS can possibly explain contradictory previous results regarding role of DAT and SERT in TRS, but further research is needed.

Identification of two secreted ferritin subunits involved in immune defense of Yesso scallop Patinopecten yessoensis

As an important iron storage protein, ferritin plays a crucial role in the iron-withholding defense system. In this study, two secreted ferritin subunits (PyFerS1 and PyFerS2) were identified from the Yesso scallop, Patinopecten yessoensis. The complete DNA sequences of the two ferritins are 7101 and 5359 bp, consisting of seven and five exons, respectively. The full-length cDNAs of PyFerS1 and PyFerS2 are 960 and 956 bp in length, encoding 228 and 220 amino acids, respectively. They have typical ferritin structures, with four long α-helices, one short α-helix and an L-loop. Signal peptides were found at the N-terminus of both ferritins, and phylogenetic analysis showed that they both clustered with secreted mollusc ferritins. PyFerS1 possesses all seven conserved residues of the ferroxidase center, whereas PyFerS2 only has two. Real-time PCR analysis indicated high expression level of PyFerS2 in the D-shaped larvae, and PyFerS1 in both D-shaped larvae and fertilized eggs. In adult scallops, PyFerS1 was only detected in the hepatopancreas, whereas PyFerS2 was detected in both hepatopancreas and mantle. After the scallops were challenged by iron ion or bacteria Vibrio anguillarum, the expression of both PyFerS1 and PyFerS2 was significantly elevated, suggesting they may play a role in scallop innate immune defense. For the first time, secreted ferritins were cloned and comprehensively characterized in bivalve molluscs. It will assist in better understanding of the role of secreted ferritins in bivalve innate immunity.

Neurogenetics of aggressive behavior: studies in primates

Aggressive behavior can have adaptive value in certain environmental contexts, but when extreme or executed inappropriately, can also lead to maladaptive outcomes. Neurogenetic studies performed in nonhuman primates have shown that genetic variation that impacts reward sensitivity, impulsivity, and anxiety can contribute to individual differences in aggressive behavior. Genetic polymorphisms in the coding or promoter regions of the Mu-Opioid Receptor (OPRM1), Corticotropin Releasing Hormone (CRH), Monoamine Oxidase A (MAOA), Dopamine D4 Receptor (DRD4), and Serotonin Transporter (SLC6A4) genes have been shown to be functionally similar in humans and rhesus macaques and have been demonstrated to contribute to individual differences in aggression. This body of literature suggests mechanisms by which genetic variation that promotes aggressivity could simultaneously increase evolutionary success while making modern humans more vulnerable to psychopathology.

The evolutionary history of SLC6A4 and the role of plasticity in Macaca

Serotonin has been repeatedly indicated as a biological marker of behavior. In particular, the serotonin transporter gene, SLC6A4, has been the focus of a large body of research. Interestingly, both rhesus macaques (Macaca mulatta) and humans have independently evolved a number of shared polymorphisms for this gene, which is indicative of parallel evolution between the two species. However, little is known about the evolution of this gene, particularly within macaques. Although there are several hypotheses as to the adaptive values of various polymorphisms, few authors have gone beyond theoretical discussion. Here, we examined the genetic variation in SLC6A4 within and between several species of macaques and investigate whether selection has played a significant role in its evolutionary history. In addition, we assayed the promoter region polymorphism, 5-HTTLPR, which is known to play a significant role in regulating both serotonin turnover and behavior. In examining the distribution of the 5-HTTLPR polymorphism, we identified significant differences between Indian and Chinese populations of Macaca mulatta; furthermore, we discovered its presence in Macaca cyclopis, which has not been described before. In regard to the evolutionary history of SLC6A4, we found little evidence for selection and conclude that SLC6A4 largely evolved through neutral processes, possibly due to its potential role in regulating behavioral plasticity. However, we also found very low levels of linkage between the coding regions and 5-HTTLPR. Because we limited evolutionary analyses to the coding regions, it is possible that the promoter region shows a distinct evolutionary history from SLC6A4.

Worldwide population variation and haplotype analysis at the serotonin transporter gene SLC6A4 and implications for association studies

BACKGROUND

Variation at the serotonin transporter gene, SLC6A4, has been associated with a variety of neuropsychiatric disorders and could be involved in other health-related phenotypes.

METHODS

To determine the extent of variation at SLC6A4, we genotyped 23 markers on approximately 2500 individuals from 47 global populations, including the promoter variable number tandem repeat (VNTR) and 2 single nucleotide polymorphisms (SNPs) immediately flanking its variable region (rs25531 and rs25532), the intron 2 VNTR, and 19 additional SNPs.

RESULTS

We observed several rare alleles at the promoter VNTR (some novel) and population-specific distributions of the reported functional SNPs rs25531, rs25532, and rs6355, as well as two alleles at the intron 2 VNTR. Alleles of interest at the VNTRs occurred on specific haplotype backgrounds. The repeat-number variants at the promoter VNTR and the intron 2 VNTR, as well as the putative functional SNPs, showed ethnic variation in frequencies. The more common alleles at the VNTR polymorphisms show wide geographic distributions, whereas rare alleles at both show more restricted distributions. The derived alleles at the two functional SNPs in the promoter VNTR show restricted distributions and occur primarily on different repeat number alleles.

CONCLUSIONS

Our findings illustrate significant variation worldwide at SLC6A4 and that the functionally implicated alleles at the SNPs rs25531, rs25532, and rs6355 occur on limited haplotypes and vary significantly in global distribution. Association studies at SLC6A4 cannot a priori extrapolate across populations and should account for the multiple polymorphisms with possible functional variation across this locus, rather than focusing solely on one or two polymorphisms as commonly seen.

Polymorphisms in serotonergic pathways influence the outcome of antidepressant therapy in psychiatric inpatients

Serotonergic pathways are known to play an essential role in the effects generated by antidepressants. Polymorphisms in serotonin receptor and transporter genes have been identified as an important factor. To investigate which of these polymorphisms may be useful to predict clinical outcome, we assessed their effect in a naturalistic clinical study. We studied the influence of the 5-hydroxytryptamine transporter (5-HTT) variable number of tandem repeats (VNTR), 5-HTTLPR/rs25531 and a 5-HTR2A intron 2 SNP with regard to response and side effects in 273 psychiatric inpatients. Main clinical assessments included Clinical Global Impressions ratings, paranoid depression scale self-rating scale and Dosage Record, and Treatment Emergent Symptoms (DOTES) Scale. We found significant associations between 5-HTTLPR/rs25531 S/L(G) alleles and response and side effects in 100 patients with selective serotonin reuptake inhibitor (SSRI) treatment (p = 0.037, CGI-I ≤ 2: 0% vs. 19% and p = 0.0005, DOTES cluster c: 0.76 vs. 0.19). 5-HTT VNTR and 5-HTR2A intron 2 polymorphisms were associated significantly with adverse effects in patients with selective and nonselective SRI (5-HTT VNTR 12/12: n = 170, p = 0.0001, side effect rates: 51% vs. 19% and rs7997012 [A/A]: n = 50, p = 0.020, side effects rates: 43% vs. 11%). No impact of the polymorphisms on mirtazapine treatment was found. Our study confirms the influence of serotonergic polymorphisms at the receptor and transporter level on SSRI response and side effects, supporting previous reports based on various study designs. The effects were strong enough to be noticed clinically in this naturalistic setting. However, randomized controlled trials are warranted to provide unequivocal evidence of the clinical usefulness of pretherapeutic screening for these polymorphisms.

Study of the association of serotonin transporter triallelic 5-HTTLPR and STin2 VNTR polymorphisms with lithium prophylaxis response in bipolar disorder

The 5-hydroxy tryptamine transporter (5-HTT) gene has been previously implicated in lithium response, but the roles of the triallelic 5-HTT linked promoter region (5-HTTLPR) and variable number tandem repeats in the second intron [serotonin transporter intron 2 (STin2)] have not been reported. We examined these polymorphisms in 122 patients with bipolar I disorder, among which 49 patients were classified as good responders, 49 as nonresponders, and 24 as partial responders to lithium prophylaxis. We observed significant variation in the genotype frequencies of STin2 polymorphism among the response groups (P=0.02). There was also a significant association of haplotype consisting of the S allele of 5-HTTLPR and 10 repeat allele of STin2 with lithium response (P=0.01) and no such relationship was found with 5-HTTLPR variants. Our data support preliminary information of a possible association of STin2 and its combined effect with 5-HTTLPR variants with lithium response and also suggest that lithium is likely to be more effective for patients carrying 5-HTT polymorphisms associated with reduced transcriptional activity.

Genetic modulation of borderline personality disorder: systematic review and meta-analysis

Borderline personality disorder (BPD) is a highly prevalent psychiatric disorder with high morbidity and mortality. Early theories ascribed an environmental etiology of BPD, but growing evidence supports a genetic vulnerability as well. The primary aim of this study was to systematically review genetic association studies focused on BPD. PubMed, ISI Web of Knowledge and PsycINFO databases were searched for studies published until December 2012. Meta-analyses were also performed when three or more studies reported genetic data on the same polymorphism. Data were analyzed with Cochrane Collaboration Review Manager Software (RevMan, version 5.0). Quality and publication bias were assessed. The systematic review of association studies examining genetic polymorphisms and BPD produced conflicting results. Meta-analyses were performed for three serotonergic polymorphisms: two common polymorphisms of the serotonin transporter gene (SLC6A4), the promoter insertion/deletion (5-HTTLPR) and the intron 2 VNTR (STin2 VNTR), and the rs1800532 (A218C) polymorphism of the tryptophan hydroxylase 1 gene (TPH1), all showing no association. No direct role of genetic polymorphisms was found in BPD. However, a few studies only are present in literature to draw definite conclusions. Further studies focusing on gene × gene and gene × environment interactions are needed to more deeply dissect the genetic role in the modulation of BPD.

Pharmacogenetics of antidepressant drugs: an update after almost 20 years of research

Major depressive disorder (MDD) is an emergent cause of personal and socio-economic burden, both for the high prevalence of the disorder and the unsatisfying response rate of the available antidepressant treatments. No reliable predictor of treatment efficacy and tolerance in the single patient is available, thus drug choice is based on a trial and error principle with poor clinical efficiency. Among modulators of treatment outcome, genetic polymorphisms are thought to explain a significant share of the inter-individual variability. The present review collected the main pharmacogenetic findings primarily about antidepressant response and secondly about antidepressant induced side effects, and discussed the main strengths and limits of both candidate and genome-wide association studies and the most promising methodological opportunities and challenges of the field. Despite clinical applications of antidepressant pharmacogenetics are not available yet, previous findings suggest that genotyping may be applied in the clinical practice. In order to reach this objective, further rigorous pharmacogenetic studies (adequate sample size, study of better defined clinical subtypes of MDD, adequate covering of the genetic variability), their combination with the results obtained through complementary methodologies (e.g., pathway analysis, epigenetics, transcriptomics, and proteomics), and finally cost-effectiveness trials are required.

Development of Ego-Resiliency: Relations to Observed Parenting and Polymorphisms in the Serotonin Transporter Gene During Early Childhood

We used observed parenting behaviors, along with genetic variants and haplotypes of the serotonin transporter gene (SLC6A4), as predictors of children's ego-resiliency during early childhood (N =153). Quality of mothers' parenting was observed at 18 months of age and mothers' reports of ego-resiliency were collected at six time points from 18 to 84 months. Genetic data were collected at 72 months. Observed parenting was positively associated with initial levels of children's ego-resiliency. Furthermore, although individual genetic variants of the serotonin transporter gene (LPR, STin2) were not associated with ego-resiliency, the S10 haplotype (that combines information from these two variants) was negatively associated with initial levels of ego-resiliency. Both parenting and serotonin genetic variation uniquely predicted children's ego-resiliency, suggesting an additive effect of genetic and parental factors.

Serotonin gene variants are unlikely to play a significant role in the pathogenesis of the sudden infant death syndrome

Sudden infant death syndrome (SIDS) is defined as the sudden and unexpected death of an infant less than 12 months of age that is related to a sleep period and remains unexplained after a complete autopsy, death scene investigation, and review of the clinical history. The cause of SIDS is unknown, but a major subset of SIDS is proposed to result from abnormalities in serotonin (5-HT) and related neurotransmitters in regions of the lower brainstem that result in failure of protective homeostatic responses to life-threatening challenges during sleep. Multiple studies have implicated gene variants that affect different elements of 5-HT neurotransmission in the pathogenesis of these abnormalities in SIDS. In this review I discuss the data from these studies together with some new data correlating genotype with brainstem 5-HT neurochemistry in the same SIDS cases and conclude that these gene variants are unlikely to play a major role in the pathogenesis of the medullary 5-HT abnormalities observed in SIDS.

Allele-specific expression of the serotonin transporter and its transcription factors following lamotrigine treatment in vitro

Lamotrigine, a mood stabilizer used clinically in the treatment of bipolar disorder, is thought to exert actions on the serotonin system. However lamotrigine's exact mechanism of action remains unclear. The current study investigated whether lamotrigine might exert its effects through altering the expression of the serotonin transporter (5-HTT) gene and its regulatory transcription factors Y box binding protein 1 (YB-1) and CCCTC-binding factor (CTCF). We further considered whether functional variable number tandem repeat (VNTR) polymorphisms in the promoter region of 5-HTT, (5-HTTLPR) and within intron 2 (Stin2) of the gene, moderated any putative gene expression changes. The study employed an in vitro design carried out in human lymphoblastoid cell lines (LCLs) to investigate the effects of lamotrigine treatment at 0.04, 0.2, and 0.4 mM doses for 24 hr on the mRNA expression of 5-HTT, YB-1, and CTCF. LCLs were selected based on combinations of haplotypes of the two VNTRs in the serotonin transporter gene; creating low-expressing and high-expressing LCL groups. Ubiquitin C (UBC) and topoisomerase I (TOP1) genes were found to be the most stably expressed housekeeping genes in drug-treated LCLs. Subsequently, quantitative PCR revealed that higher doses of lamotrigine significantly lowered 5-HTT expression and increased CTCF expression. Haplotype-specific differences in CTCF expression were found in response to lamotrigine, with strongest expression changes observed in the high-expressing LCLs. These data provide an allele-specific in vitro model for examining the molecular targets of lamotrigine, and support the important role of the serotonin transporter gene in its clinical mechanism of action.

Human amygdala volume is predicted by common DNA variation in the stathmin and serotonin transporter genes

Despite the relevance of changes in amygdala volume to psychiatric illnesses and its heritability in both health and disease, the influence of common genetic variation on amygdala morphology remains largely unexplored. In the present study, we investigated the influence of a number of novel genetic variants on amygdala volume in 139 neurologically healthy individuals of European descent. Amygdala volume was significantly associated with allelic variation in the stathmin (STMN1) and serotonin transporter (SLC6A4) genes, which have been linked to healthy and disordered affective processing. These results were replicated across both manual and automated methods of amygdala parcellation, although manual tracing showed stronger effects, providing a cautionary note to studies relying on automated parcellation methods. Future studies will need to determine whether amygdala volume mediates the impact of stathmin and serotonin transporter gene variants on normal and dysfunctional emotion processing.