Genomic structure and expression of the human serotonin 2A receptor gene (HTR2A) locus: identification of novel HTR2A and antisense (HTR2A-AS1) exons

Methylation of serotonin regulating genes in cord blood cells: association with maternal metabolic parameters and correlation with methylation in peripheral blood cells during childhood and adolescence

BACKGROUND

Serotonin (5-hydroxytryptamine, 5-HT) signaling is involved in neurodevelopment, mood regulation, energy metabolism, and other physiological processes. DNA methylation plays a significant role in modulating the expression of genes responsible for maintaining 5-HT balance, such as 5-HT transporter (SLC6A4), monoamine oxidase A (MAOA), and 5-HT receptor type 2A (HTR2A). Maternal metabolic health can influence long-term outcomes in offspring, with DNA methylation mediating these effects. We investigated associations between maternal metabolic parameters-pre-pregnancy body mass index (pBMI), gestational weight gain (GWG), and glucose tolerance status (GTS), i.e., gestational diabetes mellitus (GDM) versus normal glucose tolerance (NGT)-and cord blood methylation of SLC6A4, MAOA, and HTR2A in participants from our PlaNS birth cohort. CpG sites (15, 9, and 2 in each gene, respectively) were selected based on literature and in silico data. Methylation levels were quantified by bisulfite pyrosequencing. We also examined the stability of methylation patterns in these genes in circulating blood cells from birth to adolescence using longitudinal DNA methylation data from the ARIES database.

RESULTS

None of the 203 PlaNS mothers included in this study had preexisting diabetes, 99 were diagnosed with GDM, and 104 had NGT; all neonates were born at full term by planned Cesarean section. Methylation at most CpG sites differed between male and female newborns. SLC6A4 methylation correlated inversely with maternal pBMI and GWG, while methylation at HTR2A site -1665 correlated positively with GWG. None of the maternal metabolic parameters statistically associated with MAOA methylation. DNA methylation data in cord blood and peripheral blood at ages 7 and 15 years were available for 808 participants from the ARIES database; 4 CpG sites (2 in SLC6A4 and 2 in HTR2A) overlapped between the PlaNS and ARIES cohorts. A positive correlation between methylation levels in cord blood and peripheral blood at 7 and 15 years of age was observed for both SLC6A4 and HTR2A CpG sites.

CONCLUSIONS

Methylation of 5-HT regulating genes in cord blood cells is influenced by neonatal sex, with maternal metabolism playing an additional role. Inter-individual variations present in circulating blood cells at birth are still pronounced in childhood and adolescence.

A comprehensive review of the ten main platelet receptors involved in platelet activity and cardiovascular disease

Cardiovascular disease (CVD) is a major cause of death worldwide. Although there are many variables that contribute to the development of this disease, it is predominantly the activity of platelets that provides the mechanisms by which this disease prevails. While there are numerous platelet receptors expressed on the surface of platelets, it is largely the consensus that there are 10 main platelet receptors that contribute to a majority of platelet function. Understanding these key platelet receptors is vitally important for patients suffering from myocardial infarction, CVD, and many other diseases that arise due to overactivation or mutations of these receptors. The goal of this manuscript is to review the main platelet receptors that contribute most to platelet activity.

Associations of Germline Genetic Variants With Depression and Fatigue Among Hematologic Cancer Patients Treated With Allogeneic Hematopoietic Cell Transplantation

OBJECTIVE

Depression and fatigue are common among cancer patients and are associated with germline genetic variation. The goal of this pilot study was to examine genetic associations with depression and fatigue in the year after allogeneic hematopoietic cell transplant (HCT).

METHODS

Blood was collected from patients and their donors before HCT. Patients completed self-report measures of depression and fatigue before HCT (T1), 90 days post-HCT (T2), and 1 year post-HCT (T3). Of the 384 genetic variants genotyped on a custom Illumina BeadChip microarray, 267 were retained for analysis based on quality control. Main effects of patient and donor variants as well as their interaction were examined using regression analyses. Significant variants were defined as those with a false discovery rate-adjusted p value of <.05.

RESULTS

The sample consisted of 59 patient-donor pairs. Mean levels of depression and fatigue did not change significantly over time ( p values of > .41). Increases in depression from T1 to T2 were associated with patient-donor interactions at rs1928040 ( p = 3.0 × 10 -4 ) and rs6311 ( p = 2.0 × 10 -4 ) in HTR2A . Increases in fatigue from T1 to T2 were associated with patient rs689021 in SORL1 ( p = 6.0 × 10 -5 ) and a patient-donor interaction at rs1885884 in HTR2A ( p < 1.0 × 10 -4 ).

CONCLUSIONS

Data suggest that variants in genes regulating the serotonergic system ( HTR2A ) and lipid metabolism ( SORL1 ) are associated with changes in depression and fatigue in allogeneic HCT patients, implicating patients' own genetic inheritance as well as that of donors. Additional studies are warranted to confirm these findings.

Development of a Novel Senolysis Approach Targeting the Senescent Fibroblast Marker HTR2A via Antibody-Dependent Cellular Cytotoxicity

Abnormal remodeling of collagen and extracellular matrix caused by the accumulation of senescent fibroblasts in the dermis is the most likely cause of skin aging. Therefore, the application of "senolysis," in which only senescent cells are cleared from the body, has a potential in the development of antiaging treatments for skin. However, markers that label senescent fibroblasts only reflect the state of senescence, and it is important to develop markers as therapeutic targets to aid senolysis application. We investigated the potential of serotonin 2A receptor (HTR2A), which is involved in melanin production in response to ultraviolet light, as a senescent cell marker. The results showed that HTR2A is upregulated in aging dermal fibroblasts but is expressed at low levels in proliferating young cells. Flow cytometry demonstrated the presence of many HTR2A-positive cells in the aging cell population and few in the young cells. Furthermore, antibody-dependent cytotoxicity assays revealed that HTR2A preferentially sensitizes senescent fibroblasts and specifically damages only senescent cells by natural killer cells that recognize it. In conclusion, selective labeling of the novel senescent cell marker, HTR2A, could preferentially eliminate senescent cells and may contribute to the future development of novel skin senolysis approaches.

The contribution of the 5-hydroxytryptamine receptor 2 A gene polymorphisms rs6311 and rs6313 to Schizophrenia in Iran

OBJECTIVE

Schizophrenia is an acute mental disorder with an undefined etiology. Its high heritability suggests that several genetic variants and polymorphisms may contribute to the severity and emergence of its symptoms. Former molecular evidence has shed some light on the association of serotonergic pathway genetic polymorphisms with schizophrenia. This study aimed to investigate the association between schizophrenia and two SNPs from one haplotype block, which lies in the 5-hydroxytryptamine receptor 2 A (5-HTR2A) gene in the Iranian population.

MATERIAL AND METHODS

Blood samples were collected from one-hundred and fifty-two patients diagnosed with schizophrenia and one-hundred and fifty-eight cases of the healthy control, who were matched in terms of age and gender. The participants were genotyped for rs6311 and rs6313 using PCR-RFLP. R programming language and Haploview software were respectively leveraged for statistical and haplotype inferencing.

RESULTS

The results showed that there was no significant association between rs6313 and schizophrenia. However, the rs6311 T allele was independently associated with schizophrenia, and it was significantly associated with SCZ in an rs6311-rs6313 haplotype. Moreover, the general linear model confirmed the potential predictor role of rs6311 for schizophrenia and the C allele of rs6313 demonstrated a higher frequency among females compared to males.

CONCLUSION

The findings of this study indicated the association of rs6311 and rs6311-rs6313 haplotype with schizophrenia in the Iranian population and also suggested a potential schizophrenia risk predictor role for rs6311.

Genetic and epigenetic analysis of the serotonin 2A receptor in the context of cocaine abuse

Despite more than 2 million American cocaine users monthly, there is no approved drug for treating cocaine use disorder. Cocaine use disorder has a multifactorial aetiology, including both genetic and environmental factors. Both cocaine use and genetic variations demonstrably alter DNA methylation and gene expression in the brain in a complex manner. How these factors interact in the context of cocaine abuse in humans is unknown. We propose that we can identify potential drug targets for treating cocaine use disorders by examining genetic, epigenetic, and expression changes in the brains of individuals that abused cocaine. In this study, we identified the interaction between the epigenetics changes (DNA CpG methylation) and genetic variants (SNPs) in the HTR2A gene in the context of cocaine addiction by using brain tissue collected from individuals that overdosed on cocaine (N = 14) and healthy matched controls (N = 16). We generated DNA CpG methylation profiles in eight regions of HTR2A harbouring frequent SNPs, measuring both allelic and total methylation, and compared these methylation profiles with HTR2A mRNA expression. Furthermore, we examined the influence of common variants rs6311 and rs6313 on cocaine abuse, methylation, and gene expression. We found evidence that rs6311 regulates HTR2A methylation, consistent with earlier studies. Furthermore, the minor alleles for rs6311 and rs6313 are associated with significantly increased expression of a splice isoform in which exon 2 is truncated in both cocaine and control samples. These results reveal specific roles for HTR2A in the context of cocaine abuse, highlighting opportunities to modulate this target for treating cocaine use disorder.

Maternal Metabolic State and Fetal Sex and Genotype Modulate Methylation of the Serotonin Receptor Type 2A Gene (HTR2A) in the Human Placenta

The serotonin receptor 2A gene (HTR2A) is a strong candidate for the fetal programming of future behavior and metabolism. Maternal obesity and gestational diabetes mellitus (GDM) have been associated with an increased risk of metabolic and psychological problems in offspring. We tested the hypothesis that maternal metabolic status affects methylation of HTR2A in the placenta. The prospective study included 199 pairs of mothers and healthy full-term newborns. Genomic DNA was extracted from feto-placental samples and analyzed for genotypes of two polymorphisms (rs6311, rs6306) and methylation of four cytosine residues (−1665, −1439, −1421, −1224) in the HTR2A promoter region. Placental HTR2A promoter methylation was higher in male than female placentas and depended on both rs6311 and rs6306 genotypes. A higher maternal pre-gestational body mass index (pBMI) and, to a lesser extent, diagnosis of GDM were associated with reduced HTR2A promoter methylation in female but not male placentas. Higher pBMI was associated with reduced methylation both directly and indirectly through increased GDM incidence. Tobacco use during pregnancy was associated with reduced HTR2A promoter methylation in male but not female placentas. The obtained results suggest that HTR2A is a sexually dimorphic epigenetic target of intrauterine exposures. The findings may contribute to a better understanding of the early developmental origins of neurobehavioral and metabolic disorders associated with altered HTR2A function.

Serotonin system in the human placenta - the knowns and unknowns

The biogenic monoamine serotonin (5-hydroxytryptamine, 5-HT) is a chemical messenger widely distributed in the brain and various other organs. Its homeostasis is maintained by the coordinated activity of a variety of proteins, including enzymes of serotonin metabolism, transmembrane transporters of serotonin, and serotonin receptors. The serotonin system has been identified also in the placenta in rodent models as a key component of placental physiology. However, serotonin pathways in the human placenta are far from well understood. Their alterations may have long-lasting consequences for the fetus that can manifest later in life. In this review, we summarize information on the location of the components of the serotonin system in the human placenta, their regulation, function, and alterations in pathological pregnancies. We highlight current controversies and discuss important topics for future research.

Associations of Genetic Polymorphisms and Neuroimmune Markers With Some Parameters of Frontal Lobe Dysfunction in Schizophrenia

We investigated the associations of DRD3 rs6280, HTR1A rs6295, BDNF rs6265, SCL6A4 rs16965628, and 5HT2A rs7322347 with schizophrenia in a case-control study, and associations of these genetic variants with several clinical features. We also investigated markers of inflammatory response (C-reactive protein, IL-2, IL-6, IL-10), the activity of leukocytic elastase (LE) and α1-proteinase inhibitor (a1-PI), antibodies to S100B and myelin basic protein (MBP) in schizophrenia. Clinical symptoms were assessed on three scales: Positive and Negative Syndrome Scale, The Bush - Francis Catatonia Rating Scale and Frontal Assessment Battery. All SNPs were typed using predesigned TaqMan SNP genotyping assays. The biomarkers related to the immune system were routinely tested using ELISA kits. The association with schizophrenia was found for DRD3 rs6280 (p = 0.05) and HTR2A rs7322347 (p = 0.0013). We found differences between groups by parameters of LE and a1-PI and LE/a1-PI (p < 0.001). And IL-6 was evaluated in the schizophrenia group (p < 0.001). We showed that patients with the TT allele (BDNF rs6265) had more severe impairments in frontal lobe function. a1-PI can serve as a marker for assessing the severity of frontal lobe damage in patients with frontal dementia. We found some biological parameters reflecting the severity of frontal dysfunction in schizophrenia.

Associations and interactions of the serotonin receptor genes 5-HT1A, 5-HT2A, and childhood trauma with alexithymia in two independent general-population samples

Previous studies suggested that childhood trauma and a disturbed serotonergic neurotransmission are involved in the pathogenesis of alexithymia. Specifically, genetic polymorphisms of the serotonin receptors 5-HT1A and 5-HT2A were found to be associated with alexithymia. However, it is unclear whether these factors show main or interaction effects with childhood trauma on alexithymia. Data from two independent general-population cohorts of the Study of Health in Pomerania (SHIP-Trend: N=3,706, Age: range=20-83, 51.6% female, SHIP-LEGEND: N=2,162, Age: range=20-80, 52.5% female) were used. The Toronto Alexithymia Scale-20 (TAS-20) and the Childhood Trauma Questionnaire (CTQ) were applied. Genotypes of rs6295 of 5-HT1A and rs6311 of 5-HT2A were determined. Ordinary least-squared regression models with robust standard errors were applied to investigate associations of the main and interaction effects of childhood maltreatment and the polymorphisms with alexithymia. Childhood trauma, but none of the investigated polymorphisms showed main effects on alexithymia. However, childhood trauma showed significant CTQ sum score x rs6295 interactions in male subjects in both samples such that the presence of the G-allele diminished the CTQ associated increase in the TAS-20 sum scores. Our results support a strong role of early life stress and interactions with rs6295 on alexithymic personality features at least in male subjects.

Aberrant alternative splicing of HTR2A exon II in peripheral blood lymphocytes of drug-naïve schizophrenic patients

The aim of the study was to characterize the pattern of transcript isoforms of HTR2A exon II in lymphocytes of the blood as peripheral biomarkers of schizophrenia development and the effectiveness of antipsychotic therapy. We primarily observed an increase in mRNA levels and elevation of alternative variants in a sample of drug-naïve schizophrenic patients compared to the control group. There was no association of the expression level of HTR2A transcript isoforms with the effectiveness of the antipsychotic therapy. Antipsychotic-induced akathisia was associated with a significant reduction in the mRNA levels of the studied isoforms. In summary, our results suggest that levels of HTR2A exon II transcript isoforms are upregulated in patients with schizophrenia, but at the same time, elevated expression level of the studied HTR2A transcripts is associated with fewer side effects of the therapy.

The serotonin receptor 2A (HTR2A) rs6313 variant is associated with higher ongoing pain and signs of central sensitization in neuropathic pain patients

BACKGROUND

The serotonin receptor 2A (HTR2A) has been described as an important facilitation mediator of spinal nociceptive processing leading to central sensitization (CS) in animal models of chronic pain. However, whether HTR2A single nucleotide variants (SNVs) modulate neuropathic pain states in patients has not been investigated so far. The aim of this study was to elucidate the potential association of HTR2A variants with sensory abnormalities or ongoing pain in neuropathic pain patients.

METHODS

At total of 240 neuropathic pain patients and 253 healthy volunteers were included. Patients were phenotypically characterized using standardized quantitative sensory testing (QST). Patients and controls were genotyped for HTR2A g.-1438G > A (rs6311) and c.102C > T (rs6313). Genotype-related differences in QST parameters were assessed considering QST profile clusters, principal somatosensory components and sex.

RESULTS

There was an equal distribution of rs6313 and linked rs6311 between patients and controls. However, the rs6313 variant was significantly associated with a principal component of pinprick hyperalgesia and dynamic mechanical allodynia, indicating enhanced CS in patients with sensory loss (-0.34 ± 0.15 vs. +0.31 ± 0.11 vs., p < .001). In this cluster, the variant allele was also associated with single QST parameters of pinprick hyperalgesia (MPT, +0.64 ± 0.18 vs. -0.34 ± 0.23 p = .002; MPS, +0.66 ± 0.17 vs. -0.09 ± 0.23, p = .009) and ongoing pain was increased by 30%.

CONCLUSIONS

The specific association of the rs6313 variant with pinprick hyperalgesia and increased levels of ongoing pain suggests that the HTR2A receptor might be an important modulator in the development of CS in neuropathic pain.

SIGNIFICANCE

This article presents new insights into serotonin receptor 2A-mediating mechanisms of central sensitization in neuropathic pain patients. The rs6313 variant allele was associated with increased mechanical pinprick sensitivity and increased levels of ongoing pain supporting a contribution of central sensitization in the genesis of ongoing pain providing a possible route for mechanism-based therapies.

The association of HTR2A polymorphisms with obsessive-compulsive disorder and its subtypes: A meta-analysis

BACKGROUND

Genetic risk factors that contribute to obsessive-compulsive disorder (OCD) have yet to be elucidated. Historically, serotonergic dysfunction has been implicated. Evidence from the literature points towards the serotonin receptor 2A gene (HTR2A) as a primary candidate. Our meta-analysis investigated whether polymorphisms in HTR2A are associated with OCD or its subtypes, based on sex and age of onset.

METHODS

Studies employing case-control or family-based designs were systematically searched, and those meeting eligibility underwent quality assessment, resulting in 18 studies. A random-effects meta-analysis using standard inverse-variance weighting to compute odds ratio (OR) was conducted. To examine sensitivity, results were also obtained using a more conservative statistical method.

RESULTS

Three HTR2A variants were identified: T102C, G-1438A, and C516T. T102C and G-1438A were analyzed together due to strong linkage disequilibrium, where the 102T allele co-occurs with -1438A allele. Results reported as OR [95%CI] showed that the T/A allele were significantly associated with OCD, 1.14 [1.01, 1.29]. After stratification, results remained significant for females, 1.20 [1.00, 1.45], and early-onset OCD, 1.27 [1.02, 1.58], but not males, 1.06 [0.91, 1.23]. No associations were found for late-onset OCD, 0.98 [0.70, 1.37], or C516T, 1.22 [0.14, 10.37], but conclusions cannot be drawn from two studies.

LIMITATIONS

Associations no longer reached significance with the conservative statistical approach. HTR2A alone cannot explain OCD complexity and limited samples reporting genetic data according to subtypes.

CONCLUSIONS

These results suggest a possible association of HTR2A polymorphisms with OCD, but further investigations considering sex and age of onset with larger samples is needed.

The rs6311 of serotonin receptor 2A (5-HT2A) gene is associated with alexithymia and mental health

BACKGROUNDS

Alexithymia, difficulties in identifying and describing one's own feelings, is related to substantial clinical practice. Inspired by the links between serotonin functions and affective disorders, this study investigated associations of the serotonin receptor 2A (5-HT2A) gene with alexithymia and mental health.

METHODS

We differentiated subjects according to two functional polymorphisms (i.e., rs6311 and rs6313) of 5-HT2A gene and scored alexithymia and mental health of college students with the Toronto Alexithymia Scale (TAS-20) and the Symptom Check List-90 (SCL-90), respectively.

RESULTS

The analyses basing on sample 1 (N = 566) and sample 2 (N = 602) indicated that the G allele of rs6311 was related to higher score on the TAS-20 as compared to the AA genotype. The analysis with 467 individuals from sample 2 indicated that the rs6311 was associated with mental health, and this association was mediated by alexithymia.

LIMITATIONS

The potential confounding variables such as depression and anxiety were neglected in the analyses.

CONCLUSIONS

These findings demonstrate the contribution of the 5-HT2A to alexithymia, and highlight the link between alexithymia and mental health at genetic level.

The T102C polymorphism of 5HT2A receptor in oral epithelial dysplasia: A pilot case-control study

OBJECTIVE

investigate the T102C polymorphism of 5HT2A receptor in dysplasia in oral potentially malignant lesions and its association with smoking and alcohol habits.

METHODS

case-control study that included patients with oral potentially malignant lesions (OPML) histopathologically diagnosed with dysplasia and healthy controls, and within these group patients with and without smoking and alcohol consumption habits. Cell samples from the oral lesions were collected with the patients previously anesthetized using disposable cytological brushes. Deoxyribonucleic acid (DNA) extraction was performed and the T102C polymorphism (rs6313) was genotyped in a real-time polymerase chain reaction (PCR) allelic discrimination assays.

RESULTS

110 individuals were included in this study (38 with dysplasia and 72 controls). The genotype (p = 0.016), allele (p = 0.020) and smoking habits (<0.001) distribution differed significantly between dysplasia and control group, where the CT and TT (C - cytosine/ T - thymine) genotype and the T allele showed a higher frequency in dysplasia (65.6, 18.8 and 84.4 %, respectively) than in controls (55.7, 4.9 and 60.7). Concerning smoking habits, the higher frequency was in the dysplasia group. The multivariate logistic regression analysis, associating variables of interest and the presence of dysplasia, showed that individuals with smoking habits present 7.58 increase risk to develop dysplasia than non-smokers; and individuals carrying the T allele for the T102C polymorphism have a 4.6 increased risk to develop oral dysplasia in OPML.

CONCLUSIONS

the T102C polymorphism is associated with oral dysplasia in OPML, however, failed to show association with smoking and alcohol habits in OPML dysplasia.

Alternative splicing in serotonergic system: Implications in neuropsychiatric disorders

BACKGROUND

The serotonergic system is a key component of physiological brain function and is essential for proper neurological activity. Numerous neuropsychiatric disorders are associated with deregulation of the serotonergic system. Accordingly, many pharmacological treatments are focused on modulation of this system. While providing a promising line of therapeutic moderation, these approaches may be complicated due to the presence of alternative splicing events for key genes in this pathway. Alternative splicing is a co-transcriptional process by which different mRNA transcripts can be produced from the same gene. These different isoforms may have diverse activities and functions, and their relative balance is often critical for the maintenance of homeostasis. Alternative splicing greatly increases the production of proteins, augmenting cell plasticity, and provides an important control point for regulation of gene expression.

AIM

The objective of this narrative review is to discuss the potential impact of alternative splicing of different components of the serotonergic system and speculate on their involvement in several neuropsychiatric disorders.

CONCLUSIONS

The specific role of each isoform in disease and their relative activities in the signalling pathways involved are yet to be determined. We need to gain a better understanding of the basis of alternative isoforms of the serotonergic system in order to fully understand their impact and be able to develop new effective pharmacological isoform-specific targets.

Genetic variants as risk factors for cigarette smoking at an early age and relapse to smoking cessation treatment: A pilot study

OBJECTIVES

Tobacco smoking is a complex and multifactorial disease involving both environmental and genetic factors. In the Mexican mestizo population, single-nucleotide polymorphisms (SNPs) associated with cigarette smoking and a greater degree of nicotine addiction have been identified; however, no possible roles have been explored in regard to the age of onset of smoking or in the success of quitting.

METHODS

In this study, 151 Mexican mestizo, who smoke cigarettes, were included. They were grouped according to the age at which they started smoking: those who started smoking before 18 years of age (early smokers, ES) and those who started smoking ≥18 years of age (late smokers, LS). In addition, relapse in smoking was evaluated at the first month after the end of treatment. Genetic association was evaluated characterizing 10 SNPs in 4 genes (CHRNA5, CHRNA3, NRXN1, and HTR2A).

RESULTS

According to the dominant model of genetic inheritance, rs6313 (CT+TT) of the HTR2A gene was associated (p = 0.0201) with cigarette consumption at early ages (OR = 2.68, CI = 1.18-6.07). When the risk of relapse was analyzed one month after the end of treatment, regardless of the age of onset, the T allele (rs6313) of HTR2A appeared to be a risk factor for relapse (OR = 2.92, 95% CI = 1.06-8.11); the T allele was found more frequently in those who relapsed (50.0%) compared with people who maintained abstinence (25.4%) (p = 0.0332).

CONCLUSIONS

Our findings suggest that in Mexican mestizos who smoke cigarettes, the presence of the T allele in rs6313 of the HTR2A gene increases the risk for the early onset of cigarette smoking as well as the risk for relapsing one month after completing smoking cessation treatment.

The Interaction of TPH2 and 5-HT2A Polymorphisms on Major Depressive Disorder Susceptibility in a Chinese Han Population: A Case-Control Study

Purpose: TPH2 and 5-HT2A appear to play vital roles in the homeostatic regulation of serotonin levels in the brain, their genetic variations may lead to impaired homeostatic regulation of serotonin resulting in abnormal levels of serotonin in the brain, thus predisposing individuals to MDD. However, research studies have yet to confirm which gene-gene interaction effect between TPH2 and 5-HT2A polymorphisms results in increased susceptibility to MDD. Methods: A total of 565 participants, consisting of 278 MDD patients and 287 healthy controls from the Chinese Han population, were recruited for the present study. Six single nucleotide polymorphisms (SNPs) of TPH2/5-HT2A were selected to assess their interaction by use of a generalized multifactor dimensionality reduction method. Results: A-allele carriers of rs11178997 and rs120074175 were more likely to suffer from MDD than T-allele carriers of rs11178997, or G-allele carriers of rs120074175. The interaction between TPH2 (rs120074175, rs11178997) and 5-HT2A (rs7997012) was considered as the best multi-locus model upon the MDD susceptibility. Conclusions: Our data identified an important effect of TPH2 genetic variants (rs11178997 and rs120074175) upon the risk of MDD, and suggested that the interaction of TPH2/5-HT2A polymorphism variants confer a greater susceptibility to MDD in Chinese Han population.

Genetic variability in the serotoninergic system and age of onset in anorexia nervosa and obsessive-compulsive disorder

The age of onset of some psychiatric disorders may have etiopathogenic and clinical effects and may influence outcome. Following on from previous work by our group where we showed that early onset anorexia nervosa (AN) and obsessive-compulsive disorder (OCD) shared a common genetic background, the aim of the present study is to assess genetic pleiotropy related to the serotonergic system (SLC6A4, 5HTR2A, 5HTR2C, TPH2, SLC18A1), in a common phenotype such as very-early age of onset. One hundred and sixteen adolescents diagnosed with AN and 74 adolescents diagnosed with OCD participated in the present study. We confirmed the existence of a genetic overlap between OCD and AN. Specifically, we described genetic pleiotropy for age at onset across these disorders, associating two SNPs (rs6311, rs4942587) of the HTR2A with the very-early onset phenotype.

Testing genetic modifiers of behavior and response to atomoxetine in autism spectrum disorder with ADHD

BACKGROUND

Frequent non-pathogenic genetic variants may act as moderators of phenotypic severity for complex disorders such as autism spectrum disorder (ASD). We previously identified polymorphisms affecting mRNA expression of candidate genes, including tryptophan hydroxylase 2 (TPH2), dopamine beta hydroxylase (DBH), and dopamine transporter (DAT, SLC6A3).

METHOD

We compare genotypes and (1) clinical response to atomoxetine, (2) scores from the Autism Diagnostic Interview-Revised (ADI-R), and (3) severity of Attention Deficit Hyperactivity Disorder (ADHD) symptoms in a cohort of patients with ASD from multiple study sites.

RESULTS

There was no association between CYP2D6 metabolizer status and atomoxetine response. TPH2 rs7305115 genotype was associated with ADI-R Restrictive/Repetitive Behavior score (p=0.03). DBH rs1611115 genotype was associated with ADI-R Social score (p=0.002) and Restrictive/Repetitive Behavior score (p=0.04). The DAT intron 8 5/6 repeat was associated with ADHD symptoms (ABC Hyperactivity p=0.01 and SNAP ADHD p=0.03), replicating a previous finding.

CONCLUSIONS

We find associations between ASD phenotypes and regulatory variants in catecholamine biosynthesis genes. This work may help guide future genetics studies related to ASD.

Genetic analysis of impulsive personality traits: Examination of a priori candidates and genome-wide variation

Impulsive personality traits are heritable risk factors and putative endophenotypes for addiction and other psychiatric disorders involving disinhibition. This study examined the genetic basis of impulsive personality traits, defined as scores on the Barratt Impulsiveness Scale (BIS-11) and the UPPS-P Impulsive Behavior Scale (UPPS-P). In 983 healthy young adults of European ancestry, the study examined genetic variation in relation to a combined phenotype of seven subscales based on high phenotypic intercorrelations. The study first tested 14 a priori loci that have previously been associated impulsive personality traits or closely related constructs. Second, the study included an exploratory genome-wide scan (i.e., GWAS), acknowledging that only relatively large effects would be detectable in a sample size of ~ 1000. A priori SNP analyses revealed a significant association between the combined impulsivity phenotype and two SNPs within the 5-HT2a receptor gene (HTR2A; rs6313 and rs6311). Follow-up analyses suggested that the effects were specific to the Motor and Non-planning subscales on the BIS-11, and also that the two loci were in linkage disequilibrium. The GWAS yielded no statistically significant findings. This study further implicates loci within HTR2A with certain forms of self-reported impulsivity and identifies candidates for future investigation from the genome-wide analyses.

Identification, expression and functional characterization of M4L, a muscarinic acetylcholine M4 receptor splice variant

Rodent genomic alignment sequences support a 2-exon model for muscarinic M4 receptor. Using this model a novel N-terminal extension was discovered in the human muscarinic acetylcholine M₄ receptor. An open reading frame was discovered in the human, mouse and rat with a common ATG (methionine start codon) that extended the N-terminus of the muscarinic acetylcholine M₄ receptor subtype by 155 amino acids resulting in a longer variant. Transcriptional evidence for this splice variant was confirmed by RNA-Seq and RT-PCR experiments performed from human donor brain prefrontal cortices. We detected a human upstream exon indicating the translation of the mature longer M₄ receptor transcript. The predicted size for the longer two-exon M₄ receptor splice variant with the additional 155 amino acid N-terminal extension, designated M₄L is 69.7 kDa compared to the 53 kDa canonical single exon M₄ receptor (M₄S). Western blot analysis from a mammalian overexpression system, and saturation radioligand binding with [³H]-NMS (N-methyl-scopolamine) demonstrated the expression of this new splice variant. Comparative pharmacological characterization between the M₄L and M₄S receptors revealed that both the orthosteric and allosteric binding sites for both receptors were very similar despite the addition of an N-terminal extension.

Polymorphisms in HTR2A and DRD4 Predispose to Smoking and Smoking Quantity

BACKGROUND

Genes encoding the receptors involved in the dopaminergic and serotonergic pathways are potential candidates in the mechanisms of nicotine addiction.

AIMS

To identify genetic variants in the promoter regions and exons of the DRD4 and HTR2A genes associated with tobacco smoking and the degree of nicotine addiction in Mexican mestizos.

METHODS

The study included 438 non-smokers (NS) and 1,157 current smokers, ranked based on their consumption of cigarettes per day (cpd): 574 heavy smokers (HS, >20 cpd) and 583 light smokers (LS, 1-10 cpd). Genotyping was performed for 4 and 8 single nucleotide polymorphisms (SNPs) in the DRD4 and HTR2A genes, respectively.

RESULTS

The C allele of rs1800955 in DRD4 was found to be associated with cigarette smoking in the HS vs. NS and LS vs. NS comparisons (p = 2.34E-03 and p = 1.13E-03, respectively); the association was maintained in the homozygous CC genotype (p = 5.00E-04 and p = 2.00E-04, respectively). The T allele of rs6313 in HTR2A was significantly associated with cigarette smoking and a greater degree of nicotine addiction (p = 4.77E-03, OR = 1.55); the association was maintained in the homozygous genotype (TT) (p = 4.90E-03, OR = 1.96). The A allele of rs6313 was associated with cigarette smoking in the HS vs. NS comparison (p = 1.53E-02, OR = 1.36); the risk was nearly doubled in the homozygous AA genotype (p = 1.30E-03, OR = 1.83) compared with the heterozygous GA genotype (OR = 1.38).

CONCLUSIONS

Among Mexican mestizos, the C allele of rs1800955 in the DRD4 gene and the A allele of rs6311 in the HTR2A gene are associated with cigarette smoking, whereas the T allele of rs6313 in HTR2A is associated with cigarette smoking and the degree of nicotine addiction.