Genotyping serotonin transporter polymorphisms 5-HTTLPR and rs25531 in European- and African-American subjects from the National Institute of Mental Health's Collaborative Center for Genomic Studies

Genetic and Phenotypic Profiling of Triptan Users in a Swedish Cluster Headache Cohort

Up to 25% of individuals who live with cluster headache (CH), an extremely painful primary headache disorder, do not adequately respond to the first-line treatment, triptans. Studies have indicated that genetic variants can play a role in treatment response. Likewise, differences in clinical characteristics can give clues to mechanisms underlying triptan non-response. Our aim was to investigate five genetic variants previously implicated in triptan response and their relation to triptan usage in our Swedish CH cohort and to investigate potential distinctions in clinical characteristics. 545 CH patients were screened for the genetic variants rs1024905, rs6724624, rs4795541, rs5443, and rs2651899 with a case control design based on triptan usage. Analysis of clinical characteristics was based on self-reported questionnaire data from 893 patients. One genetic variant, rs1024905, was significantly associated with triptan non-usage in CH (Pc = 0.010). In addition, multi-allele effector analysis showed that individuals with a higher number of effector variants were less likely to use triptans (P = 0.007). Analysis of clinical characteristics showed that triptan users were more likely to have alcohol as a trigger (57.4% vs 43.4%, P = 0.002), have autonomic symptoms (95.1% vs 88.1%, P = 0.002), and be current smokers (27.0% vs 21.9%, P = 0.033) compared to non-users. These results support the hypothesis that genetic variants can play a role in triptan usage in CH and that patients with a typical CH phenotype are more likely to use triptans.

Pharmacogenetics of selective serotonin reuptake inhibitors (SSRI): A serotonin reuptake transporter (SERT)-based approach

Neuropsychiatric disorders are considered to be the most common cause of disability worldwide. Serotonin and its transporter is a prominent paradigm in mood disorders. Response to selective serotonin reuptake inhibitors (SSRI) is altered due to heterogeneity in the serotonin transporter gene, SLC6A4 (solute carrier family 6 member 4). The reported polymorphisms are found to be in different regions of the transporter gene: promoter region (5-HTTLPR and various single nucleotide polymorphisms within it), intron (STin2), and exon 9 (I425V). The long and short alleles of the 5-HTTLPR gene, which are prevalent among variations, may mediate differential effects. In long allelic variant carriers, an increased response to SSRI and timely recovery is due to increased availability of SERT. Whereas, SERT availability is significantly decreased in short allelic carriers, necessitating a reduction in SSRI dosage due to the increased risk of adverse drug reactions. Thus, pharmacogenetic investigations are required to understand the impact of functional variations on the efficacy and tolerability of SSRI. Identifying the carrier variants may aid in clear-decision making of the treatment regimen, aiding the approach of personalized medication.

Contrasting ABCB1 pharmacogenetics and psychotropic responses in child and adolescent psychiatry: a case comparison

This case comparison illustrates pharmacogenetic testing in psychotropic and clinical management in relation to the ABCB1 gene, which encodes the P-glycoprotein transporter affecting blood-brain barrier (BBB) permeability. Two pediatric patients (9 and 11 years old) were selected for similar clinical presentations with opposing ABCB1 genotype, while they were identically matched for key CYP450, dopaminergic and serotonergic genes (CYP2C9, CYP2C19, DRD2, SLC6A4, 5HTR2A). Case A was functional for the ABCB1 gene (G/G rs1045642), suggesting that the BBB had a functional P-glycoprotein transporter. Case B was subfunctional for the ABCB1 gene (A/A rs1045642), suggesting that the patient's BBB may be permeable to psychotropic drugs. Case A had more medication trials and dose adjustments than Case B. Case A had two inpatient admissions and interspersed emergency room visits, while case B had none.

The interplay of pineal hormones and socioeconomic status leading to colorectal cancer disparity

Colorectal cancer (CRC) is the third leading cause of cancer-related deaths in the United States. Despite increased screening options and state-of-art treatments offered in clinics, racial differences remain in CRC. African Americans (AAs) are disproportionately affected by the disease; the incidence and mortality are higher in AAs than Caucasian Americans (CAs). At the time of diagnosis, AAs more often present with advanced stages and aggressive CRCs, primarily accounting for the racial differences in therapeutic outcomes and mortality. The early incidence of CRC in AAs could be attributed to race-specific gene polymorphisms and lifestyle choices associated with socioeconomic status (SES). Altered melatonin-serotonin signaling, besides the established CRC risk factors (age, diet, obesity, alcoholism, and tobacco use), steered by SES, glucocorticoid, and Vitamin D status in AAs could also account for the early incidence in this racial group. This review focuses on how the lifestyle factors, diet, allelic variants, and altered expression of specific genes could lead to atypical serotonin and melatonin signaling by modulating the synthesis, secretion, and signaling of these pineal hormones in AAs and predisposing them to develop more aggressive CRC earlier than CAs. Crosstalk between gut microbiota and pineal hormones and its impact on CRC pathobiology is addressed from a race-specific perspective. Lastly, the status of melatonin-focused CRC treatments, the need to better understand the perturbed melatonin signaling, and the potential of pineal hormone-directed therapeutic interventions to reduce CRC-associated disparity are discussed.

Pharmacogenetically Guided Escitalopram Treatment for Pediatric Anxiety Disorders: Protocol for a Double-Blind Randomized Trial

Current pharmacologic treatments for pediatric anxiety disorders (e.g., selective serotonin reuptake inhibitors (SSRIs)) frequently use "one size fits all" dosing strategies based on average responses in clinical trials. However, for some SSRIs, including escitalopram, variation in CYP2C19 activity produces substantial variation in medication exposure (i.e., blood medication concentrations). This raises an important question: would refining current SSRI dosing strategies based on CYP2C19 phenotypes increase response and reduce side effect burden? To answer this question, we designed a randomized, double-blind trial of adolescents 12-17 years of age with generalized, separation, and/or social anxiety disorders (N = 132). Patients are randomized (1:1) to standard escitalopram dosing or dosing based on validated CYP2C19 phenotypes for escitalopram metabolism. Using this approach, we will determine whether pharmacogenetically-guided treatment-compared to standard dosing-produces faster and greater reduction in anxiety symptoms (i.e., response) and improves tolerability (e.g., decreased risk of treatment-related activation and weight gain). Secondarily, we will examine pharmacodynamic variants associated with treatment outcomes, thus enhancing clinicians' ability to predict response and tolerability. Ultimately, developing a strategy to optimize dosing for individual patients could accelerate response while decreasing side effects-an immediate benefit to patients and their families. ClinicalTrials.gov Identifier: NCT04623099.

Genetic Predictors of Response to Acupuncture or Cognitive Behavioral Therapy for Insomnia in Cancer Survivors: An Exploratory Analysis

CONTEXT

Insomnia is a common problem affecting cancer survivors. While effective nonpharmacological treatments are available, it is unknown whether individual genetic characteristics influence treatment response.

OBJECTIVES

We conducted an exploratory analysis of genetic associations with insomnia treatment response in a randomized trial of cognitive behavioral therapy for insomnia (CBT-I) vs. acupuncture in a heterogeneous group of cancer survivors.

METHODS

We successfully genotyped 136 participants for 11 genetic variants. Successful treatment response was defined as a reduction in Insomnia Severity Index score of at least eight points from baseline to week 8. We used Fisher exact tests to evaluate associations between genotype and treatment success for each treatment arm, for an alpha level of 0.05 with unadjusted and Holm-Bonferroni-adjusted P-values.

RESULTS

We found that more carriers of COMT rs4680-A alleles responded to acupuncture compared to the GG carriers (63.6% vs. 27.8%, P = 0.013). More carriers of the NFKB2 rs1056890 CC genotype also responded to acupuncture compared to TT or CT carriers (72.2% vs. 38.9%, P = 0.009). There were no significant differences found between any of the tested gene variants and CBT-I response. None of the results remained statistically significant after adjustment for multiple testing.

CONCLUSION

In cancer survivors, specific variants in the COMT and NFKB2 genes are potentially associated with response to acupuncture but not to CBT-I. Confirming these preliminary results will help inform precision insomnia management for cancer survivors.

5-HTTLPR-rs25531 and Antidepressant Treatment Outcomes in Korean Patients with Major Depression

INTRODUCTION

Despite the ethnic differences in 5-HTTLPR (S allele relates to better antidepressant response in Korean and Japanese people, while L allele with better response in Caucasians), it is unclear whether 5-HTTLPR and its high expression locus rs25531 are interactively associated with antidepressant treatment outcome. We investigated the individual and interaction effects of these polymorphisms on antidepressant treatment outcomes in the Korean population.

METHODS

A total of 464 Korean subjects with major depressive disorder completed 6 weeks of antidepressant monotherapy. Venous blood was extracted for genotyping 5-HTTLPR and rs25531 by polymerase chain reaction and DNA sequencing. We used logistic regression analyses to verify the main and interaction effects of 5-HTTLPR and rs25531 on response and remission after antidepressant treatment.

RESULTS

After adjusting for covariates, the SS genotype of 5-HTTLPR was significantly associated with better treatment outcomes (p<0.001, odds ratio [OR] [95% confidence interval (CI)]=2.435 [1.551, 3.823] in response; p<0.001, OR [95% CI]=2.912 [1.730, 4.903] in remission), while G-containing genotype (AG+GG) of rs25531 was only associated with remission (p=0.034, OR [95% CI]=2.104 [1.058, 4.181]). The interaction effect of 5-HTTLPR and rs25531 on response and remission was insignificant (all p>0.05).

DISCUSSION

Our findings suggest variations in allelic frequency and functionality of 5-HTTLPR and rs25531 among the different ethnicities. We found a minor advantage of rs25531 in achieving remission. However, there was no interaction effect with 5-HTTLPR.

Racial differences in platelet serotonin polymorphisms in acute coronary syndrome

INTRODUCTION

Genetic differences between races have been hypothesized to contribute to differences in outcome from acute coronary syndromes (ACS). Our objective was to assess racial differences in genetic variations in the platelet serotonin transporter (5HTT) and receptor in patients with ACS.

MATERIALS AND METHODS

127 consecutive patients, African Americans (AA) = 27; Caucasian (C) =100, admitted with ACS were evaluated for platelet function by serotonin (5HT) induced platelet activation. All patients were genotyped for two polymorphisms in the serotonin-transporter-linked polymorphic region (5-HTTLPR) S/L and L_G/L_A and one polymorphism of the serotonin 2A receptor (5-HT2A, T102C) gene. All patients were followed for major and minor adverse cardiac events at 12 months.

RESULTS

AA when compared to C had a lower prevalence of the HTTLPR S allele (21% vs 45%, p = 0.0003) and a higher prevalence of the L_G allele (24% vs 4.5%, p = 0.0001). Allelic frequency of the 5-HT2A T102C allele was not significantly different between the races. Platelet activation was lower in AA compared to C, median EC50 5HT was 12.08 μg vs 2.14 μg (p = 0.001). The 5-HTTLPR and the 5-HT2A polymorphisms were not associated with platelet functional responses to serotonin. There were no significant differences in major or minor adverse cardiac events in patients with serotonin transporter or receptor polymorphisms.

CONCLUSION

We found a lower prevalence of the S allele and a higher prevalence of the G allele in AA with ACS. We also found decreased platelet activation in AA which did not correlate with serotonin-related platelet polymorphisms. It is unclear if other contributing factors may explain these platelet functional differences.

Maltreatment timing, HPA axis functioning, multigenic risk, and depressive symptoms in African American youth: Differential associations without moderated mediation

Utilizing a large (N = 739), ancestrally homogenous sample, the current study aimed to better understand biological risk processes involved in the development of depressive symptoms in maltreated, African American children age 8-12 years. Maltreatment was independently coded from Child Protective Services records and maternal report. Self-reported depressive symptoms were attained in the context of a week-long, summer research camp. DNA was acquired from buccal cell or saliva samples and genotyped for nine polymorphisms in four hypothalamic-pituitary-adrenal (HPA)-axis-related genes: FKBP5, NR3C1, NR3C2, and CRHR1. Salivary cortisol samples were collected each morning (9 a.m.) and late afternoon (4 p.m.) throughout the week to assess HPA functioning. Results revealed that experiences of maltreatment beginning prior to age 5 were most predictive of depressive symptoms, whereas maltreatment onset after age 5 was most predictive of HPA axis dysregulation (blunted daytime cortisol patterns). Multigenic risk did not relate to HPA functioning, nor did it moderate the relationship between maltreatment and HPA activity. There was no mediation of the relationship between maltreatment and depressive symptoms by HPA dysfunction. Results are interpreted through a developmental psychopathology lens, emphasizing the principle of equifinality while carefully appraising racial differences. Implications for future research, particularly the need for longitudinal studies, and important methodological considerations are discussed.

Association of Serotonin Transporter (SERT) Polymorphisms with Opioid Dependence and Dimensional Aspects of Cocaine Use in a Caucasian Cohort of Opioid Users

INTRODUCTION

A functional tandem repeat polymorphism in the promoter of the serotonin transporter (SERT) gene (SLC6A4) has been studied for association to neuropsychiatric conditions, including substance use disorders. Short (S) forms of this repeat result in reduced transcription, and presumably greater synaptic levels of serotonin, which are involved in opioid and cocaine-induced reward. Dual exposure to heroin and cocaine is a common pattern of poly-drug use and is associated with considerable morbidity. We hypothesize that SLC6A4 variants are associated with cocaine exposure in subjects with an opioid dependence diagnosis (OD), and also in non-dependent opioid users (NOD). Other single nucleotide polymorphisms (SNPs) of SLC6A4 may also be likewise associated.

MATERIALS AND METHODS

This study determined whether variants of the SLC6A4 promoter repeats and two intronic SNPs, rs16965628 and rs2066713, are associated with categorical diagnoses of opioid dependence (DSM-IV criteria) and with dimensional aspects of cocaine use, in a Caucasian cohort (n=591). Three groups of subjects were examined: (1) 276 subjects with opioid dependence diagnosis (OD); (2) 163 subjects who had used opioids for non-medical reasons but never had an opioid dependence diagnosis (NOD); (3) 152 healthy controls (HC).

RESULTS

Aside from high exposure to heroin in the OD group, relatively high exposure to cocaine was detected in both OD and NOD groups. The SERT repeat genotype (classified as "long-long" [LL] versus "short-long" plus "short-short" [SL+SS]) was not associated with categorical opioid dependence diagnoses. A nominally significant association was identified with the [SL+SS] genotype of SLC6A4 and cocaine KMSK scores ≥"cutpoint" for a cocaine dependence diagnosis (p=0.026). The [SL+SS] genotype was associated with more rapid cocaine escalation than the LL genotype. No significant associations of rs16965628 and rs2066713 SNPs were found overall.

CONCLUSION

The functional SERT promoter tandem repeat genotype may be associated to heavy cocaine exposure and more rapid escalation of cocaine use, in persons with and without opioid dependence diagnosis.

Serotonin Transporter Gene Promoter Hypomethylation as a Predictor of Antidepressant Treatment Response in Major Depression: A Replication Study

BACKGROUND

The serotonin transporter gene (SLC6A4; 5-HTT; SERT) is considered a prime candidate in pharmacogenetic research in major depressive disorder (MDD). Besides genetic variation, recent advances have spotlighted the involvement of epigenetic mechanisms such as DNA methylation in predicting antidepressant treatment response in "pharmaco-epigenetic" approaches. In MDD, lower SLC6A4 promoter methylation has been suggested to predict impaired response to serotonergic antidepressants. The present study sought to replicate and extend this finding in a large, independent sample of MDD patients.

METHODS

The sample comprised n = 236 Caucasian patients with MDD receiving antidepressant medication in a naturalistic treatment setting. Functional DNA methylation of 9 CpG sites located in the SLC6A4 promoter region was analyzed via direct sequencing of sodium bisulfite- treated DNA extracted from blood cells. Patients were assessed over the course of a 6-week in-patient treatment using the Hamilton Depression Scale (HAM-D).

RESULTS

Results confirm relative SLC6A4 hypomethylation to predict impaired antidepressant response both dimensionally and categorically (HAM-D reductions < 50%) and to furthermore be indicative of nonremission (HAM-D > 7). This also held true in a homogenous subgroup of patients continuously treated with selective serotonin reuptake inhibitors or serotonin/noradrenaline reuptake inhibitors (n = 110).

CONCLUSIONS

Impaired response to serotonergic antidepressants via SLC6A4 hypomethylation may be conveyed by increased gene expression and consequently decreased serotonin availability, which may counteract the effects of serotonergic antidepressants. The present results could in the future inform clinical decision-making towards a more personalized treatment of MDD.

The role of 5-HTTLPR in autism spectrum disorder: New evidence and a meta-analysis of this polymorphism in Latin American population with psychiatric disorders

The autism spectrum disorder (ASD) is a complex disorder encompassing a broad phenotypic and genotypic variability. The short (S)/long (L) 5-HTTLPR polymorphism has a functional role in the regulation of extracellular serotonin levels and both alleles have been associated to ASD. Most studies including European, American, and Asian populations have suggested an ethnical heterogeneity of this polymorphism; however, the short/long frequencies from Latin American population have been under-studied in recent meta-analysis. Here, we evaluated the 5-HTTLPR polymorphism in Colombian individuals with idiopathic ASD and reported a non-preferential S or L transmission and a non-association with ASD risk or symptom severity. Moreover, to recognize the allelic frequencies of an under-represented population we also recovered genetic studies from Latin American individuals and compared these frequencies with frequencies from other ethnicities. Results from meta-analysis suggest that short/long frequencies in Latin American are similar to those reported in Caucasian population but different to African and Asian regions.

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.

Pharmacogenomics: an Update for Child and Adolescent Psychiatry

PURPOSE OF REVIEW

This paper aims to acquaint child and adolescent psychiatrists with the field of pharmacogenomics (PGX) and review the most up-to-date evidence-based practices to guide the application of this field in clinical care.

RECENT FINDINGS

Despite much research being done in this area, the field of PGX continues to yield controversial findings. In the adult world, studies have focused on the impact of combinatorial gene panels that guide medication selection by providing reports that estimate the impact of multiple pharmacodynamic and pharmacokinetic genes, but to date, these have not been directly examined in younger patient populations. Pharmacokinetic genes, CYP2D6 and CYP2C19, and hypersensitivity genes, HLA-A and HLA-B, have the strongest evidence base for application to pharmacotherapy in children. Although the field is evolving, and the evidence is mixed, there may be a role for PGX testing in children to help guide dosing and monitoring strategies. However, evidence-based medicine, rather than PGX testing, continues to play the lead role in guiding medication selection in pediatric psychopharmacology.

A Review of Mental Health and Mental Health Care Disparities Research: 2011-2014

Racial/ethnic minorities in the United States are more likely than Whites to have severe and persistent mental disorders and less likely to access mental health care. This comprehensive review evaluates studies of mental health and mental health care disparities funded by the National Institute of Mental Health (NIMH) to provide a benchmark for the 2015 NIMH revised strategic plan. A total of 615 articles were categorized into five pathways underlying mental health care and three pathways underlying mental health disparities. Identified studies demonstrate that socioeconomic mechanisms and demographic moderators of disparities in mental health status and treatment are well described, as are treatment options that support diverse patient needs. In contrast, there is a need for studies that focus on community- and policy-level predictors of mental health care disparities, link discrimination- and trauma-induced neurobiological pathways to disparities in mental illness, assess the cost effectiveness of disparities reduction programs, and scale up culturally adapted interventions.

Characterization of Serotonin Signaling Components in Patients with Inflammatory Bowel Disease

BACKGROUND

Tryptophan hydroxylase (TPH)1 catalyzes the biosynthesis of serotonin (5-hydroxytrptamine; 5-HT) in enterochromaffin (EC) cells, the predominant source of gut 5-HT. Secreted 5-HT regulates various gut functions through diverse 5-HT receptor (5-HTR) families, and 5-HT transporter (5-HTT) sequesters its activity via uptake into surrounding cells. In inflammatory bowel disease (IBD) mucosal 5-HT signaling is altered, including upregulated EC cell numbers and 5-HT levels. We examined key mucosal 5-HT signaling components and blood 5-HT levels and, as part of a pilot study, investigated the association between 5-HTT gene-linked polymorphic region (5HTTLPR) and Crohn's disease (CD).

METHODS

In the context of inflammation, colonic expressions of TPH1, 5-HTT and 5-HTRs were studied in CD patients (n=15) and healthy controls (HC; n=10) using quantitative polymerase chain reaction (qPCR). We also investigated 5HTTLPR in 40 CD patients and HC utilizing PCR and measured platelet-poor plasma (PPP) and plasma 5-HT concentrations.

RESULTS

Compared with HC, inflammation in CD patients was associated with elevated TPH1, 5-HTR3, 5-HTR4, 5-HTR7 and downregulated 5-HTT expressions. In our second cohort of participants, significantly higher PPP and plasma 5-HT levels and higher S-genotype (L/S+S/S) than L/L genotype were observed in CD patients compared with HC.

CONCLUSION

Our results suggest that augmented mucosal 5-HT signaling and specific 5-HTTLPR genotype-associated decreased efficiency in 5-HT reuptake, the latter through increased 5-HT availability, may contribute to inflammation in CD patients. These findings revealed important information on various components of 5-HT signaling in intestinal inflammation which may ultimately lead to effective strategies targeting this pathway in IBD.

Ways of knowing in precision health

Precision health can provide an avenue to bridge and integrate ways of knowing for research and practice. Nurse scientists have a long-standing interest in using multiple sources of information to address research questions of significance to the profession and discipline of nursing, which can lead to much needed contributions to precision health care. In this paper, nursing scientists discuss emerging research methods including omics, electronic sensors, and geospatial data, and mixed methods that further develop nursing science and contribute to precision health initiatives. The authors provide exemplars of the types of knowledge and ways of knowing that, using these and other advanced data and analytic strategies, may advance precision health within the context of nursing science.

Pharmacogenetics of Sertraline Tolerability and Response in Pediatric Anxiety and Depressive Disorders

Objective: To determine whether genetic variants in a pharmacokinetic gene (the number of CYP2C19 reduced function alleles [RFAs]), and in pharmacodynamic genes (HTR2A, SLC6A4, and GRIK4) influence sertraline tolerability and response in a cohort of pediatric patients with anxiety and depressive disorders. Methods: A retrospective analysis was performed using the electronic medical record data of 352 patients <19 years of age being treated for anxiety and/or depressive disorders with sertraline and who underwent routine clinical CYP2C19 genotyping. Additional genotyping and analysis of variants in HTR2A, SLC6A4, and GRIK4 were conducted for 249 patients. Multivariate regression models testing for associations with CYP2C19 were adjusted for concomitant use of interacting medications. Combinatorial classification and regression tree (CART) analyses containing all pharmacokinetic and pharmacodynamic genes and clinical factors were performed. Results: The maximum sertraline dose during the initial titration period of sertraline was inversely associated with the number of CYP2C19 RFAs and sertraline dose at 60 (p = 0.025) and 90 days (p = 0.025). HTR2A rs6313 was associated with sertraline dose (p = 0.011) and time to the average maximum sertraline dose (p = 0.039). Regarding efficacy, the number of CYP2C19 RFAs was not associated with the sertraline dose at the time of response (p = 0.22), whereas for the pharmacodynamic genes, only HTR2A rs6313 was associated with response dose (p = 0.022). An association was observed between predicted expression levels of SLC6A4 and the duration on sertraline (p = 0.025). Combinatorial CART and multivariate regression analyses implicated that pharmacodynamic genes and clinical factors influence the maximum sertraline dose and response dose. The total number of side effects was not associated with any of the variants tested. Conclusion: Both pharmacokinetic and pharmacodynamic factors, in addition to clinical and demographic components, influence sertraline dose, response, and tolerability, thereby necessitating further research to assess for the validity of these pharmacogenetic associations in children and adolescents.

Association Study Between Serotonin Transporter Gene and Fluoxetine Response in Mexican Patients With Major Depressive Disorder

OBJECTIVE

Pharmacogenetic studies have identified genetic variants associated with fluoxetine response in patients with major depression disorder (MDD). The serotonin transporter gene is the principal site of action of selective serotonin reuptake inhibitors. Previous studies analyzing SLC6A4 gene variants are inconsistent and differ among populations. The aim of the present study was to analyze the association between 5-HTTLPR/rs24531 triallelic polymorphism and fluoxetine response in Mexican patients with MDD.

METHODS

We analyzed a sample of 150 patients with MDD. Fluoxetine response was assessed according to a reduction in the Hamilton Depression Rating Scale and Montgomery Depression Rating Scale scores of 50% or more at 8 weeks from baseline. In addition, we analyzed the genotype and allele distribution between responder and nonresponder patients in a subgroup of very severe depression patients.

RESULTS

We did not find association between fluoxetine responders and 5-HTTLPR/rs25531 variants (P = 0.0637). However, in the analysis of severe depression at baseline (Hamilton Depression Rating Scale ≥ 25), we observed a high frequency of low activity alleles (S/LG) in nonresponders patients (P = 0.0102).

CONCLUSIONS

Our findings showed an association between low activity alleles of SLC6A4 gene and fluoxetine nonresponse in patients with severe depression.

Familial aggregation of major depressive disorder in an African-American community

BACKGROUND

African Americans (AAs) with major depressive disorder (MDD) experience more impairment and poorer treatment outcomes relative to Whites, yet are underrepresented in family studies of MDD. This is the first study to investigate the familial aggregation of major depression among AAs.

METHODS

Participants' reports of depression from clinical and family history (FH) interviews were used to examine depression rates among 435 first-degree relatives and half-siblings of 63 depressed cases and 222 relatives of 33 nondepressed controls. Binary logistic regression was used to compute odds ratios (ORs) for FH of MDD and level of trauma exposure (high and low) in cases versus controls. Poisson regression models with generalized estimating equations were used to assess MDD in relatives of cases versus relatives of controls.

RESULTS

Cases and controls did not differ in either FH of MDD (OR = 1.2, 95% confidence interval [CI] = 0.5-2.9), or prevalence of MDD in relatives (relative risk [RR] = 1.5, 95% CI = 0.8-2.5). However, exposure to high trauma was associated with increased risk of MDD (OR = 3.0, 95% CI = 1.22-7.17) and the combined effect of FH and trauma was greater than expected under an additive model. Similarly, the RR for MDD among relatives of cases with high-trauma levels was 2.2 (1.24-4.2), compared to relatives of controls with low trauma.

CONCLUSION

The effect of FH of MDD appears to be exacerbated among individuals exposed to high trauma. Replication and further research on the chronology and subtypes of trauma and MDD, and their interactions, remain essential in AA populations.

Serotonergic 5HTTLPR/rs25531 s-allele homozygosity associates with violent suicides in male citalopram users

Depressive disorders are involved as a background factor in over 50% of suicide cases. The most widely used antidepressants today are serotonin selective reuptake inhibitors (SSRIs). However, not all users benefit from SSRI medication. Although the overall number of suicides in Finland have decreased notably during the last decade, the annual rate is still relatively high, particularly in male population. In this study, we tested the hypothesis that the genetic variants associated with decreased citalopram efficiency, 5HTTLPR/rs25531, and increased impulsive behavior, MAOA-uVNTR and HTR2B Q20*, are more frequent among citalopram users committing suicide than among the citalopram users in general. Also the effect of alcohol was evaluated. The study population comprised 349 suicide victims (184 males and 165 females). Based on the suicide method used, cases were divided into two groups; violent (88 males and 49 females) and non-violent (96 males and 116 females). The control group (284; 159 males and 125 females) consisted of citalopram users who died of causes other than suicide. We found that male citalopram users with low functioning s/s genotype of 5HTTLPR/rs25531 were in increased risk to commit violent suicide (OR 2.50, 95%CI 1.15-5.42, p = 0.020). Surprisingly, high blood alcohol concentration was observed to be a risk factor only in non-violent suicides (both males and females), but not in violent ones. No association between suicides and MAOA-uVNTR and HTR2B Q20*, which have been previously connected to violent and impulsive behavior, was detected.

Associations between serotonin transporter and behavioral traits and diagnoses related to anxiety

The role of the serotonin transporter promoter-linked polymorphism (5-HTTLPR) in psychiatric disease remains unclear. Behavioral traits could serve as alternative outcomes that are stable, precede psychopathology, and capture more sub-clinical variation. We test associations between 5-HTTLPR and (1) behavioral traits and (2) clinical diagnoses of anxiety and depression. Second and third generation participants (N=203, 34.2±13.8 years, 54% female) at high- or low- familial risk for depression (where risk was defined by the presence of major depression in the 1st generation) were assessed longitudinally using the Schedule for Affective Disorders and Schizophrenia-lifetime interview, Barratt Impulsiveness Scale-11, Buss-Perry Aggression Questionnaire, and the NEO-Five Factor Inventory. High (but not low)-risk offspring with two risk (short, s) alleles had higher impulsivity (+13%), hostility (+31%) and neuroticism (+23%). SS was associated higher rates of panic (OR=7.05 [2.44, 20.38], p=0.0003) and phobic (OR=2.68[1.04, 6.93], p=0.04), but not other disorders. Impulsivity accounted for 16% of associations between 5-HTTLPR and panic, and 52% of association between 5-HTTLPR and phobias. We show that 5-HTTLPR predicts higher impulsivity, hostility, and neuroticism, and that impulsivity could serve as a useful independent outcome or intermediary phenotype in genetic studies of anxiety.

Epigenetic adaptation of the placental serotonin transporter gene (SLC6A4) to gestational diabetes mellitus

We tested the hypothesis that gestational diabetes mellitus (GDM) alters the DNA methylation pattern of the fetal serotonin transporter gene (SLC6A4), and examined the functional relevance of DNA methylation for regulation of the SLC6A4 expression in the human placenta. The study included 50 mother-infant pairs. Eighteen mothers were diagnosed with GDM and 32 had normal glucose tolerance (NGT). All neonates were of normal birth weight and born at term by planned Cesarean section. DNA and RNA were isolated from samples of tissue collected from the fetal side of the placenta immediately after delivery. DNA methylation was quantified at 7 CpG sites within the SLC6A4 distal promoter region using PCR amplification of bisulfite treated DNA and subsequent DNA sequencing. SLC6A4 mRNA levels were measured by reverse transcription—quantitative PCR (RT-qPCR). Functional SLC6A4 polymorphisms (5HTTLPR, STin2, rs25531) were genotyped using standard PCR-based procedures. Average DNA methylation across the 7 analyzed loci was decreased in the GDM as compared to the NGT group (by 27.1%, p = 0.037) and negatively correlated, before and after adjustment for potential confounder/s, with maternal plasma glucose levels at the 24th to 28th week of gestation (p<0.05). Placental SLC6A4 mRNA levels were inversely correlated with average DNA methylation (p = 0.010) while no statistically significant association was found with the SLC6A4 genotypes (p>0.05). The results suggest that DNA methylation of the fetal SLC6A4 gene is sensitive to the maternal metabolic state in pregnancy. They also indicate a predominant role of epigenetic over genetic mechanisms in the regulation of SLC6A4 expression in the human placenta. Longitudinal studies in larger cohorts are needed to verify these results and determine to which degree placental SLC6A4 changes may contribute to long-term outcomes of infants exposed to GDM.

Effects of the serotonin transporter gene, sensitivity of response to alcohol, and parental monitoring on risk for problem alcohol use

The serotonin transporter-linked polymorphic region (5-HTTLPR) of the serotonin transporter gene (SLC6A4) has been previously associated with alcohol-related risk. Most findings point to short (S) allele carriers being at increased risk for negative alcohol outcomes relative to long allele homozygotes, although some work indicates a more complex relationship. The current prospective study aimed to clarify how and under what circumstances variations in 5-HTTLPR transmit risk for various alcohol-related outcomes. Participants were 218 adolescents and young adults (29% female) enrolled in the Michigan Longitudinal Study. We tested a moderated mediation model with 5-HTTLPR as the predictor, Self-Rating of the Effects of Alcohol (SRE) score as the mediator, alcohol-related outcomes as the dependent variables, parental monitoring as the moderator of the SRE to alcohol outcomes path, and prior drinks, sex, age, and body mass index as covariates. Four alcohol-related outcomes were tested. The S allele was associated with higher SRE scores (i.e., lower response to alcohol). Parental monitoring was a significant moderator: At low levels of parental monitoring, higher SRE scores predicted more drinks consumed and binge drinking episodes. At high levels of monitoring, higher SRE scores were significantly related to fewer alcohol-related problems. Findings suggest that one mechanism by which 5-HTTLPR variation transmits alcohol-related risk is through level of response to alcohol. Furthermore, the strength and direction of this effect varied by level of parental monitoring, indicating that even in the presence of genetic and physiological vulnerability, parents can influence the likelihood of offspring developing problematic alcohol-related behaviors.

Consensus paper of the WFSBP Task Force on Genetics: Genetics, epigenetics and gene expression markers of major depressive disorder and antidepressant response

Major depressive disorder (MDD) is a heritable disease with a heavy personal and socio-economic burden. Antidepressants of different classes are prescribed to treat MDD, but reliable and reproducible markers of efficacy are not available for clinical use. Further complicating treatment, the diagnosis of MDD is not guided by objective criteria, resulting in the risk of under- or overtreatment. A number of markers of MDD and antidepressant response have been investigated at the genetic, epigenetic, gene expression and protein levels. Polymorphisms in genes involved in antidepressant metabolism (cytochrome P450 isoenzymes), antidepressant transport (ABCB1), glucocorticoid signalling (FKBP5) and serotonin neurotransmission (SLC6A4 and HTR2A) were among those included in the first pharmacogenetic assays that have been tested for clinical applicability. The results of these investigations were encouraging when examining patient-outcome improvement. Furthermore, a nine-serum biomarker panel (including BDNF, cortisol and soluble TNF-α receptor type II) showed good sensitivity and specificity in differentiating between MDD and healthy controls. These first diagnostic and response-predictive tests for MDD provided a source of optimism for future clinical applications. However, such findings should be considered very carefully because their benefit/cost ratio and clinical indications were not clearly demonstrated. Future tests may include combinations of different types of biomarkers and be specific for MDD subtypes or pathological dimensions.

Gender-specific association between serotonin transporter polymorphisms (5-HTTLPR and rs25531) and neuroticism, anxiety and depression in well-defined healthy Han Chinese

BACKGROUND

A tri-allelic serotonin transporter promoter polymorphism (5-HTTLPR/rs25531) more effectively determines the levels of transcriptional efficacy than that with the bi-allelic 5-HTTLPR polymorphism in vitro. Both are reportedly associated with personality traits of negative emotionality, but with conflicting findings. One explanation for this is that a gender difference may play a role in genetic contribution. Here, we hypothesized that the tri-allelic genotype of the serotonin transporter is more closely linked to neuroticism, an anxiety- and depression-related trait, than the bi-allelic variation, particularly in a gender-dependent way.

METHODS

The genotypes of the 5-HTTLPR and rs25531 loci were determined in 1139 well-defined physically and mentally healthy Han Chinese (550 men, 589 women; mean age 38.3±10.3 years). All participants completed the neuroticism measure of the short-form Maudsley Personality Inventory (MPI). The levels of anxiety and depression were assessed by the Beck Anxiety Inventory (BAI) and the Beck Depression Inventory (BDI), respectively.

RESULTS

A significant tri-allelic genotype-by-gender interaction effect was found in the MPI-neuroticism measure. S'S' homozygotes were associated with higher neuroticism than L' allele carriers in men. Also, both the BAI and BDI scores were higher in the S'S' homozygotic men. In the bi-allelic analyses, however, there was only an association between SS genotype and MPI-neuroticism in men.

LIMITATIONS

Sub-analyses by gender-stratification may reduce the statistical power.

CONCLUSIONS

Our findings confirm that gender differences exist in the genetic contributions of the serotonin transporter in human neuroticism, and anxiety/depression. Our data provide further support for rs25531, strengthening the effects of 5-HTTLPR.

5-HTTLPR polymorphism is linked to neural mechanisms of selective attention in preschoolers from lower socioeconomic status backgrounds

While a growing body of research has identified experiential factors associated with differences in selective attention, relatively little is known about the contribution of genetic factors to the skill of sustained selective attention, especially in early childhood. Here, we assessed the association between the serotonin transporter linked polymorphic region (5-HTTLPR) genotypes and the neural mechanisms of selective attention in young children from lower socioeconomic status (SES) backgrounds. Event-related potentials (ERPs) were recorded during a dichotic listening task from 121 children (76 females, aged 40-67 months), who were also genotyped for the short and long allele of 5-HTTLPR. The effect of selective attention was measured as the difference in ERP mean amplitudes elicited by identical probe stimuli embedded in stories when they were attended versus unattended. Compared to children homozygous for the long allele, children who carried at least one copy of the short allele showed larger effects of selective attention on neural processing. These findings link the short allele of the 5-HTTLPR to enhanced neural mechanisms of selective attention and lay the groundwork for future studies of gene-by-environment interactions in the context of key cognitive skills.

Prenatal maternal depression and child serotonin transporter linked polymorphic region (5-HTTLPR) and dopamine receptor D4 (DRD4) genotype predict negative emotionality from 3 to 36 months

Prenatal maternal depression and a multilocus genetic profile of two susceptibility genes implicated in the stress response were examined in an interaction model predicting negative emotionality in the first 3 years. In 179 mother-infant dyads from the Maternal Adversity, Vulnerability, and Neurodevelopment cohort, prenatal depression (Center for Epidemiologic Studies Depressions Scale) was assessed at 24 to 36 weeks. The multilocus genetic profile score consisted of the number of susceptibility alleles from the serotonin transporter linked polymorphic region gene (5-HTTLPR): no long-rs25531(A) (LA: short/short, short/long-rs25531(G) [LG], or LG/LG] vs. any LA) and the dopamine receptor D4 gene (six to eight repeats vs. two to five repeats). Negative emotionality was extracted from the Infant Behaviour Questionnaire-Revised at 3 and 6 months and the Early Child Behavior Questionnaire at 18 and 36 months. Mixed and confirmatory regression analyses indicated that prenatal depression and the multilocus genetic profile interacted to predict negative emotionality from 3 to 36 months. The results were characterized by a differential susceptibility model at 3 and 6 months and by a diathesis-stress model at 36 months.

Neighborhood × Serotonin Transporter Linked Polymorphic Region (5-HTTLPR) interactions for substance use from ages 10 to 24 years using a harmonized data set of African American children

This study investigated the influences of neighborhood factors (residential stability and neighborhood disadvantage) and variants of the serotonin transporter linked polymorphic region (5-HTTLPR) genotype on the development of substance use among African American children aged 10-24 years. To accomplish this, a harmonized data set of five longitudinal studies was created via pooling overlapping age cohorts to establish a database with 2,689 children and 12,474 data points to span ages 10-24 years. A description of steps used in the development of the harmonized data set is provided, including how issues such as the measurement equivalence of constructs were addressed. A sequence of multilevel models was specified to evaluate Gene × Environment effects on growth of substance use across time. Findings indicated that residential instability was associated with higher levels and a steeper gradient of growth in substance use across time. The inclusion of the 5-HTTLPR genotype provided greater precision to the relationships in that higher residential instability, in conjunction with the risk variant of 5-HTTLPR (i.e., the short allele), was associated with the highest level and steepest gradient of growth in substance use across ages 10-24 years. The findings demonstrated how the creation of a harmonized data set increased statistical power to test Gene × Environment interactions for an under studied sample.

Genetic moderation of interpersonal psychotherapy efficacy for low-income mothers with major depressive disorder: implications for differential susceptibility

Genetic moderation of interpersonal psychotherapy (IPT) efficacy for economically disadvantaged women with major depressive disorder was examined. Specifically, we investigated whether genotypic variation in corticotropin releasing hormone receptor 1 (CRHR1) and the linked polymorphic region of the serotonin transporter gene (5-HTTLPR) moderated effects of IPT on depressive symptoms over time. We also tested genotype moderation of IPT mechanisms on social adjustment and perceived stress. Non-treatment-seeking urban women at or below the poverty level with infants were recruited from the community (N = 126; M age = 25.33 years, SD = 4.99; 54.0% African American, 22.2% Caucasian, and 23.8% Hispanic/biracial) and randomized to individual IPT or Enhanced Community Standard groups. The results revealed that changes in depressive symptoms over time depended on both intervention group and genotypes (5-HTTLPR and CRHR1). Moreover, multiple-group path analysis indicated that IPT improved depressive symptoms, increased social adjustment, and decreased perceived stress at posttreatment among women with the 0 copies of the CRHR1 TAT haplotype only. Finally, improved social adjustment at postintervention significantly mediated the effect of IPT on reduced depressive symptoms at 8 months postintervention for women with 0 copies of the TAT haplotype only. Post hoc analyses of 5-HTTLPR were indicative of differential susceptibility, albeit among African American women only.

Latent trajectories of adolescent antisocial behavior: Serotonin transporter linked polymorphic region (5-HTTLPR) genotype influences sensitivity to perceived parental support

Although prevailing theories of antisocial behavior (ASB) emphasize distinct developmental trajectories, few studies have explored gene–environment interplay underlying membership in empirically derived trajectories. To improve knowledge about the development of overt (e.g., aggression) and covert (e.g., delinquency) ASB, we tested the association of the 44-base pair promoter polymorphism in the serotonin transporter linked polymorphic region gene (5-HTTLPR), perceived parental support (e.g., closeness and warmth), and their interaction with ASB trajectories derived using latent class growth analysis in 2,558 adolescents followed prospectively into adulthood from the National Longitudinal Study of Adolescent Health. Three distinct trajectories emerged for overt (low desisting, adolescent peak, and late onset) and covert ASB (high stable, low stable, and nonoffending). Controlling for sex, parental support inversely predicted membership in the adolescent-peak overt ASB trajectory (vs. low desisting), but was unrelated to class membership for covert ASB. Furthermore, the 5-HTTLPR genotype significantly moderated the association of parental support on overt ASB trajectory membership. It is interesting that the pattern of Gene × Environment interaction differed by trajectory class: whereas short allele carriers were more sensitive to parental support in predicting the late-onset trajectory, the long/long genotype functioned as a potential “plasticity genotype” for the adolescent-peak trajectory group. We discuss these preliminary findings in the context of the differential susceptibility hypothesis and discuss the need for future studies to integrate gene–environment interplay and prospective longitudinal designs.

Genetic Susceptibility and Sleep Disturbance in Black Mothers of Preterm Infants: An Exploratory Study

Serotonin (5HT) is involved in emotion and sleep regulation and the 5HT transporter (5HTT) regulates 5HT function. A common 44-base pair deletion (short allele) or insertion (long allele) polymorphism in the promoter region of 5HTT (5-HTTLPR) is differentially associated with 5HTT transcription efficiency. Under stressful conditions, the short allele of 5-HTTLPR has been associated with depression and sleep disturbance. Black women are at higher risk for preterm labor and depressive symptoms. Thus, this exploratory study aimed to examine whether depressive symptoms and sleep disturbance in Black mothers would vary as a function of the 5-HTTLPR genotype when they faced the stress of infant hospitalization after preterm birth at early postpartum. A total of 30 Black mothers filled out a battery of questionnaires, including the Perceived Stress Scale, Edinburgh Postnatal Depression Scale, and General Sleep Disturbance Scale. A wrist actigraph was used to assess total sleep time and circadian activity rhythms. Buccal cells from saliva were collected to test the 5-HTTLPR genotype. Results showed that about 38% of the mothers were heterozygous for the short (S/L) allele, and 62% were homozygous for the long (L/L) allele. Mothers’ perceived global stress, depressive symptoms, and circadian activity rhythms did not vary with their 5-HTTLPR genotypes. Unexpectedly, mothers with the L/L allele reported greater sleep disturbances than those with the S/L allele. Ethnic specificity in genetic susceptibility to stress was discussed.

Serotonergic medication enhances the association between suicide and sunshine

BACKGROUND

An association between suicide and sunshine has been reported. The effect of sunshine on hormones and neurotransmitters such as serotonin has been hypothesized to exert a possible triggering effect on susceptible individuals. The aim of this study is to examine if there is an association between sunshine and suicide, adjusting for season, and if such an association differs between individuals on different antidepressants.

METHODS

By using Swedish Registers and the Swedish Meteorological and Hydrological Institute we obtained information, including forensic data on antidepressive medication for 12,448 suicides and data on monthly sunshine duration. The association between monthly suicide and sunshine hours was examined with Poisson regression analyses while stratifying for sex and age and controlling for time trend and season. These analyses were repeated in different groups of antidepressant treatment.

RESULTS

We found a significantly increased suicide risk with increasing sunshine in both men and women. This finding disappeared when we adjusted for season. Among both men and women treated with selective serotonin reuptake inhibitors (SSRIs) there was a positive association between sunshine and suicide even after adjustment for season and time trend for suicide. Pair comparisons showed that the sunshine-suicide association was stronger among men treated with SSRIs compared to other antidepressant medications or no medication at all.

LIMITATIONS

Other meteorological factors were not controlled (i.e. temperature) for in the analyses.

CONCLUSIONS

There is an enhanced association between sunshine and suicide among those with SSRI medication, even after adjusting for season. This may have interesting theoretical and clinical implications.

Genetic moderation of child maltreatment effects on depression and internalizing symptoms by serotonin transporter linked polymorphic region (5-HTTLPR), brain-derived neurotrophic factor (BDNF), norepinephrine transporter (NET), and corticotropin releasing hormone receptor 1 (CRHR1) genes in African American children

Genetic moderation of the effects of child maltreatment on depression and internalizing symptoms was investigated in a sample of low-income maltreated and nonmaltreated African American children (N = 1,096). Lifetime child maltreatment experiences were independently coded from Child Protective Services records and maternal report. Child depression and internalizing problems were assessed in the context of a summer research camp by self-report on the Children's Depression Inventory and adult counselor report on the Teacher Report Form. DNA was obtained from buccal cell or saliva samples and genotyped for polymorphisms of the following genes: serotonin transporter linked polymorphic region (5-HTTLPR), brain-derived neurotrophic factor (BDNF), norepinephrine transporter, and corticotropin releasing hormone receptor 1. Analyses of covariance with age and gender as covariates were conducted, with maltreatment status and respective polymorphism as main effects and their Gene × Environment (G × E) interactions. Maltreatment consistently was associated with higher Children's Depression Inventory and Teacher Report Form symptoms. The results for child self-report symptoms indicated a G × E interaction for BDNF and maltreatment. In addition, BDNF and triallelic 5-HTTLPR interacted with child maltreatment in a G × G × E interaction. Analyses for counselor report of child anxiety/depression symptoms on the Teacher Report Form indicated moderation of child maltreatment effects by triallelic 5-HTTLPR. These effects were elaborated based on variation in developmental timing of maltreatment experiences. Norepinephrine transporter was found to further moderate the G × E interaction of 5-HTTLPR and maltreatment status, revealing a G × G × E interaction. This G × G × E was extended by consideration of variation in maltreatment subtype experiences. Finally, G × G × E effects were observed for the co-action of BDNF and the corticotropin releasing hormone receptor 1 haplotype. The findings illustrate the variable influence of specific genotypes in G × E interactions based on variation in maltreatment experiences and the importance of a multigenic approach for understanding influences on depression and internalizing symptoms among African American children.

Genetic Variations in the Serotonergic System Mediate a Combined, Weakened Response to SSRI Treatment: A Proposed Model

Individuals with the short (S) allele in the promoter region of the serotonin transporter gene (5-HTTLPR) show a less favorable response to selective serotonin reuptake inhibitor (SSRI) treatment than individuals with the long (L) allele. Similarly, individuals with the C(-1019)G allele for the mutation found in the promoter region of the serotonin 1A receptor gene (5-HTR1A) have shown blunted responses to SSRI treatment when compared with individuals lacking this polymorphism. While these findings have been replicated across multiple studies, only two studies to date have reported data for a gene-gene interaction associated with response to SSRI treatment. Both of these studies reported a combined effect for these genotypes, with individuals homozygous for the L allele and the C allele (5-HTT(L/L)-1A(C/C)) reporting the most favorable response to SSRI treatment, and individuals homozygous for the S allele and the G allele (5-HTT(S/S)-1A(G/G)) reporting the least favorable response to SSRI treatment. Additionally, no neural mechanisms have been proposed to explain why this gene-gene interaction has been observed. To that end, this article provides a review of the relevant literature associated with these polymorphisms and proposes a feasible model that describes a genotype-dependent modulation of postsynaptic serotonin signaling associated with the 5-HTT and 5-HTR1A genes.

Population frequencies of the Triallelic 5HTTLPR in six Ethnicially diverse samples from North America, Southeast Asia, and Africa

Genetic differences between populations are potentially an important contributor to health disparities around the globe. As differences in gene frequencies influence study design, it is important to have a thorough understanding of the natural variation of the genetic variant(s) of interest. Along these lines, we characterized the variation of the 5HTTLPR and rs25531 polymorphisms in six samples from North America, Southeast Asia, and Africa (Cameroon) that differ in their racial and ethnic composition. Allele and genotype frequencies were determined for 24,066 participants. Results indicated higher frequencies of the rs25531 G-allele among Black and African populations as compared with White, Hispanic and Asian populations. Further, we observed a greater number of 'extra-long' ('XL') 5HTTLPR alleles than have previously been reported. Extra-long alleles occurred almost entirely among Asian, Black and Non-White Hispanic populations as compared with White and Native American populations where they were completely absent. Lastly, when considered jointly, we observed between sample differences in the genotype frequencies within racial and ethnic populations. Taken together, these data underscore the importance of characterizing the L-G allele to avoid misclassification of participants by genotype and for further studies of the impact XL alleles may have on the transcriptional efficiency of SLC6A4.

Serotonin transporter gene hypomethylation predicts impaired antidepressant treatment response

Variation in the serotonin transporter gene (5-HTT; SERT; SLC6A4) has been suggested to pharmacogenetically drive interindividual differences in antidepressant treatment response. In the present analysis, a 'pharmaco-epigenetic' approach was applied by investigating the influence of DNA methylation patterns in the 5-HTT transcriptional control region on antidepressant treatment response. Ninety-four patients of Caucasian descent with major depressive disorder (MDD) (f = 61) were analysed for DNA methylation status at nine CpG sites in the 5-HTT transcriptional control region upstream of exon 1A via direct sequencing of sodium bisulfite treated DNA extracted from blood cells. Patients were also genotyped for the functional 5-HTTLPR/rs25531 polymorphisms. Clinical response to treatment with escitalopram was assessed by intra-individual changes of HAM-D-21 scores after 6 wk of treatment. Lower average 5-HTT methylation across all nine CpGs was found to be associated with impaired antidepressant treatment response after 6 wk (p = 0.005). This effect was particularly conferred by one individual 5-HTT CpG site (CpG2 (GRCh37 build, NC_000017.10 28.563.102; p = 0.002). 5-HTTLPR/rs25531 haplotype was neither associated with 5-HTT DNA methylation nor treatment response. This analysis suggests that DNA hypomethylation of the 5-HTT transcriptional control region - possibly via increased serotonin transporter expression and consecutively decreased serotonin availability - might impair antidepressant treatment response in Caucasian patients with MDD. This pharmaco-epigenetic approach could eventually aid in establishing epigenetic biomarkers of treatment response and thereby a more personalized treatment of MDD.