Meta-analysis and systematic review of ADGRL3 (LPHN3) polymorphisms in ADHD susceptibility.

The gene encoding adhesion G protein-coupled receptor L3 (ADGRL3, also referred to as latrophilin 3 or LPHN3) has been associated with ADHD susceptibility in independent ADHD samples. We conducted a systematic review and a comprehensive meta-analysis to summarize the associations between the most studied ADGRL3 polymorphisms (rs6551665, rs1947274, rs1947275, and rs2345039) and both childhood and adulthood ADHD. Eight association studies (seven published and one unpublished) fulfilled criteria for inclusion in our meta-analysis. We also incorporated GWAS data for ADGRL3. In order to avoid overlapping samples, we started with summary statistics from GWAS samples and then added data from gene association studies. The results of our meta-analysis suggest an effect of ADGRL3 variants on ADHD susceptibility in children (n = 8724/14,644 cases/controls and 1893 families): rs6551665 A allele (Z score = -2.701; p = 0.0069); rs1947274 A allele (Z score = -2.033; p = 0.0421); rs1947275 T allele (Z score = 2.339; p = 0.0978); and rs2345039 C allele (Z score = 3.806; p = 0.0026). Heterogeneity was found in analyses for three SNPs (rs6551665, rs1947274, and rs2345039). In adults, results were not significant (n = 6532 cases/15,874 controls): rs6551665 A allele (Z score = 2.005; p = 0.0450); rs1947274 A allele (Z score = 2.179; p = 0.0293); rs1947275 T allele (Z score = -0.822; p = 0.4109); and rs2345039 C allele (Z score = -1.544; p = 0.1226). Heterogeneity was found just for rs6551665. In addition, funnel plots did not suggest publication biases. Consistent with ADGRL3's role in early neurodevelopment, our findings suggest that the gene is predominantly associated with childhood ADHD.

A Potential Role for the STXBP5-AS1 Gene in Adult ADHD Symptoms.

We aimed to detect Attention-deficit/hyperactivity (ADHD) risk-conferring genes in adults. In children, ADHD is characterized by age-inappropriate levels of inattention and/or hyperactivity-impulsivity and may persists into adulthood. Childhood and adulthood ADHD are heritable, and are thought to represent the clinical extreme of a continuous distribution of ADHD symptoms in the general population. We aimed to leverage the power of studies of quantitative ADHD symptoms in adults who were genotyped. Within the SAGA (Study of ADHD trait genetics in adults) consortium, we estimated the single nucleotide polymorphism (SNP)-based heritability of quantitative self-reported ADHD symptoms and carried out a genome-wide association meta-analysis in nine adult population-based and case-only cohorts of adults. A total of n = 14,689 individuals were included. In two of the SAGA cohorts we found a significant SNP-based heritability for self-rated ADHD symptom scores of respectively 15% (n = 3656) and 30% (n = 1841). The top hit of the genome-wide meta-analysis (SNP rs12661753; p-value = 3.02 × 10-7) was present in the long non-coding RNA gene STXBP5-AS1. This association was also observed in a meta-analysis of childhood ADHD symptom scores in eight population-based pediatric cohorts from the Early Genetics and Lifecourse Epidemiology (EAGLE) ADHD consortium (n = 14,776). Genome-wide meta-analysis of the SAGA and EAGLE data (n = 29,465) increased the strength of the association with the SNP rs12661753. In human HEK293 cells, expression of STXBP5-AS1 enhanced the expression of a reporter construct of STXBP5, a gene known to be involved in "SNAP" (Soluble NSF attachment protein) Receptor" (SNARE) complex formation. In mouse strains featuring different levels of impulsivity, transcript levels in the prefrontal cortex of the mouse ortholog Gm28905 strongly correlated negatively with motor impulsivity as measured in the five choice serial reaction time task (r2 = - 0.61; p = 0.004). Our results are consistent with an effect of the STXBP5-AS1 gene on ADHD symptom scores distribution and point to a possible biological mechanism, other than antisense RNA inhibition, involved in ADHD-related impulsivity levels.

[The gut-brain axis in attention deficit hyperactivity disorder: the role of the microbiota]. / El eje intestino-cerebro en el trastorno por deficit de atencion/hiperactividad: papel de la microbiota.

INTRODUCTION: Attention deficit hyperactivity disorder (ADHD) has a complex aetiology, mainly attributed to a number of susceptibility genes and environmental factors. Genetic association studies, however, have been inconsistent and have identified genetic variants with a moderate effect that explain a small proportion of the estimated inheritability of the disorder (< 10%). Recent studies suggest that the gut microbiota and diet play an important role in the development and symptoms of different mental disorders. Nevertheless, no clear evidence exists on the issue. This project proposes an alternative approach to identify mechanisms by which the intestinal microbial ecosystem and diet could contribute to the presence of ADHD. AIM: To identify biomarkers for ADHD by examining the gut microbiota. SUBJECTS AND METHODS: We conducted a cross-sectional study of adult patients with ADHD (n = 100) and control subjects (n = 100). Measures of ADHD evaluation and eating habits were performed in both groups. Samples of faecal material were obtained from which to extract bacterial DNA, then used to characterise the participants' gut microbiota. A meta-genomic association study was later performed to attempt to correlate the bacterial composition of the intestine with the clinical subtypes of the disorder. RESULTS AND CONCLUSIONS: Comparing the gut microbiota profiles of subjects with ADHD and controls is expected to help account for the clinical heterogeneity of the disorder and identify new mechanisms involved in its development.

TITLE: El eje intestino-cerebro en el trastorno por deficit de atencion/hiperactividad: papel de la microbiota.Introduccion. El trastorno por deficit de atencion/hiperactividad (TDAH) presenta una etiologia compleja, atribuida principalmente a multiples genes de susceptibilidad y factores ambientales. No obstante, los estudios geneticos de asociacion han sido inconsistentes, identificando variantes geneticas de efecto moderado que explican una pequeña proporcion de la heredabilidad estimada del trastorno (< 10%). Recientes estudios sugieren que la microbiota intestinal y la dieta desempeñan un papel importante en el desarrollo y los sintomas de diferentes trastornos mentales. Sin embargo, en la actualidad no existe una claridad absoluta al respecto. El presente proyecto propone un abordaje alternativo para identificar mecanismos a traves de los cuales el ecosistema microbiano intestinal y la dieta podrian contribuir a la presencia del TDAH. Objetivo. Identificar biomarcadores para el TDAH a traves del estudio de la microbiota intestinal. Sujetos y metodos. Estudio transversal de pacientes adultos con TDAH (n = 100) y de individuos control (n = 100). En ambos grupos se tomaran medidas de evaluacion de TDAH y habitos alimentarios. Se obtendran muestras fecales para la extraccion del ADN bacteriano, que permitiran caracterizar la microbiota intestinal de los participantes, para posteriormente realizar un estudio de asociacion metagenomico e intentar correlacionar la composicion bacteriana intestinal con subtipos clinicos del trastorno. Resultados y conclusiones. Se espera que la comparacion de los perfiles de microbiota intestinal entre sujetos con TDAH y controles ayude a explicar la heterogeneidad clinica del trastorno e identificar nuevos mecanismos implicados en su desarrollo.

Pharmacogenetics of methylphenidate response and tolerability in attention-deficit/hyperactivity disorder.

Methylphenidate (MPH) is the most frequently used pharmacological treatment in children with attention-deficit/hyperactivity disorder. However, a considerable interindividual variability exists in clinical outcome, which may reflect underlying genetic influences. We analyzed 57 single-nucleotide polymorphisms in 9 dopamine-related candidate genes (TH, DBH, COMT, DAT1 and DRD1-5) as potential predictors of MPH efficacy and tolerability, and we considered prenatal and perinatal risk factors as environmental hazards that may influence treatment effects in a gene-by-environment analysis. Our results provide evidence for the contribution of DRD3 (P=0.041; odds ratio (OR)=4.00), DBH (P=0.032; OR=2.85), TH (P=5.5e-03; OR=4.34) and prenatal smoking (P=1.7e-03; OR=5.10) to the clinical efficacy of MPH, with a higher risk for treatment failure in genetically susceptible subjects whose mother smoked during pregnancy. Adverse events after MPH treatment were significantly associated with variation in DBH (P=6.4e-03; OR=0.28) and DRD2 (P=0.047; OR=3.76). This study suggests that the dopaminergic system together with prenatal smoking exposure may moderate MPH treatment effects.

Preliminary evidence for association of genetic variants in pri-miR-34b/c and abnormal miR-34c expression with attention deficit and hyperactivity disorder.

Attention deficit and hyperactivity disorder (ADHD) is a prevalent neurodevelopmental disorder characterized by impairment to sustain attention and inability to control impulses and activity level. The etiology of ADHD is complex, with an estimated heritability of 70-80%. Under the hypothesis that alterations in the processing or target binding of microRNAs (miRNAs) may result in functional alterations predisposing to ADHD, we explored whether common polymorphisms potentially affecting miRNA-mediated regulation are involved in this psychiatric disorder. We performed a comprehensive association study focused on 134 miRNAs in 754 ADHD subjects and 766 controls and found association between the miR-34b/c locus and ADHD. Subsequently, we provided preliminary evidence for overexpression of the miR-34c-3p mature form in peripheral blood mononuclear cells of ADHD subjects. Next, we tested the effect on gene expression of single-nucleotide polymorphisms within the ADHD-associated region and found that rs4938923 in the promoter of the pri-miR-34b/c tags cis expression quantitative trait loci for both miR-34b and miR-34c and has an impact on the expression levels of 681 transcripts in trans, including genes previously associated with ADHD. This gene set was enriched for miR-34b/c binding sites, functional categories related to the central nervous system, such as axon guidance or neuron differentiation, and serotonin biosynthesis and signaling canonical pathways. Our results provide preliminary evidence for the contribution to ADHD of a functional variant in the pri-miR-34b/c promoter, possibly through dysregulation of the expression of mature forms of miR-34b and miR-34c and some target genes. These data highlight the importance of abnormal miRNA function as a potential epigenetic mechanism contributing to ADHD.

Genome-wide association study of lifetime cannabis use based on a large meta-analytic sample of 32 330 subjects from the International Cannabis Consortium.

Cannabis is the most widely produced and consumed illicit psychoactive substance worldwide. Occasional cannabis use can progress to frequent use, abuse and dependence with all known adverse physical, psychological and social consequences. Individual differences in cannabis initiation are heritable (40-48%). The International Cannabis Consortium was established with the aim to identify genetic risk variants of cannabis use. We conducted a meta-analysis of genome-wide association data of 13 cohorts (N=32 330) and four replication samples (N=5627). In addition, we performed a gene-based test of association, estimated single-nucleotide polymorphism (SNP)-based heritability and explored the genetic correlation between lifetime cannabis use and cigarette use using LD score regression. No individual SNPs reached genome-wide significance. Nonetheless, gene-based tests identified four genes significantly associated with lifetime cannabis use: NCAM1, CADM2, SCOC and KCNT2. Previous studies reported associations of NCAM1 with cigarette smoking and other substance use, and those of CADM2 with body mass index, processing speed and autism disorders, which are phenotypes previously reported to be associated with cannabis use. Furthermore, we showed that, combined across the genome, all common SNPs explained 13-20% (P<0.001) of the liability of lifetime cannabis use. Finally, there was a strong genetic correlation (rg=0.83; P=1.85 × 10(-8)) between lifetime cannabis use and lifetime cigarette smoking implying that the SNP effect sizes of the two traits are highly correlated. This is the largest meta-analysis of cannabis GWA studies to date, revealing important new insights into the genetic pathways of lifetime cannabis use. Future functional studies should explore the impact of the identified genes on the biological mechanisms of cannabis use.

Transcriptomic and genetic studies identify NFAT5 as a candidate gene for cocaine dependence.

Cocaine reward and reinforcing effects are mediated mainly by dopaminergic neurotransmission. In this study, we aimed at evaluating gene expression changes induced by acute cocaine exposure on SH-SY5Y-differentiated cells, which have been widely used as a dopaminergic neuronal model. Expression changes and a concomitant increase in neuronal activity were observed after a 5 µM cocaine exposure, whereas no changes in gene expression or in neuronal activity took place at 1 µM cocaine. Changes in gene expression were identified in a total of 756 genes, mainly related to regulation of transcription and gene expression, cell cycle, adhesion and cell projection, as well as mitogen-activeated protein kinase (MAPK), CREB, neurotrophin and neuregulin signaling pathways. Some genes displaying altered expression were subsequently targeted with predicted functional single-nucleotide polymorphisms (SNPs) in a case-control association study in a sample of 806 cocaine-dependent patients and 817 controls. This study highlighted associations between cocaine dependence and five SNPs predicted to alter microRNA binding at the 3'-untranslated region of the NFAT5 gene. The association of SNP rs1437134 with cocaine dependence survived the Bonferroni correction for multiple testing. A functional effect was confirmed for this variant by a luciferase reporter assay, with lower expression observed for the rs1437134G allele, which was more pronounced in the presence of hsa-miR-509. However, brain volumes in regions of relevance to addiction, as assessed with magnetic resonance imaging, did not correlate with NFAT5 variation. These results suggest that the NFAT5 gene, which is upregulated a few hours after cocaine exposure, may be involved in the genetic predisposition to cocaine dependence.

Inflammatory myofibroblastic tumor of the esophagus treated by endoscopy.

Inflammatory myofibroblastic tumors are rare lesions that have been described in virtually every organ including the gastrointestinal tract. The esophagus is an extremely unusual site for these tumors, with only a few cases described in the literature. Surgery has been the most common therapeutic approach used for the resection of these lesions. In the present case, a patient diagnosed with an inflammatory myofibroblastic tumor of the upper esophagus was reported, and it was successfully removed by endoscopy with no complications.

Association study of 37 genes related to serotonin and dopamine neurotransmission and neurotrophic factors in cocaine dependence.

Cocaine dependence is a neuropsychiatric disorder in which both environmental and genetic factors are involved. Several processes, that include reward and neuroadaptations, mediate the transition from use to dependence. In this regard, dopamine and serotonin neurotransmission systems are clearly involved in reward and other cocaine-related effects, whereas neurotrophic factors may be responsible for neuroadaptations associated with cocaine dependence. We examined the contribution to cocaine dependence of 37 genes related to the dopaminergic and serotoninergic systems, neurotrophic factors and their receptors through a case-control association study with 319 single nucleotide polymorphisms selected according to genetic coverage criteria in 432 cocaine-dependent patients and 482 sex-matched unrelated controls. Single marker analyses provided evidence for association of the serotonin receptor HTR2A with cocaine dependence [rs6561333; nominal P-value adjusted for age = 1.9e-04, odds ratio = 1.72 (1.29-2.30)]. When patients were subdivided according to the presence or absence of psychotic symptoms, we confirmed the association between cocaine dependence and HTR2A in both subgroups of patients. Our data show additional evidence for the involvement of the serotoninergic system in the genetic susceptibility to cocaine dependence.

[Genetic bases of attention deficit hyperactivity disorder]. / Bases geneticas del trastorno por deficit de atencion/hiperactividad.

AIMS: The purpose of this study is to update the information available on the main group of genes that have been related with a susceptibility to attention deficit hyperactivity disorder (ADHD) or with the pharmacological response to different drugs used in the treatment of ADHD, in a number of different association and meta-analysis studies. DEVELOPMENT: Different studies have provided evidence of the importance of the genetic load in the susceptibility to ADHD. The work carried out to date point to genes in the dopaminergic system, such as the gene that codes for the dopamine transporter (DAT1 or SLC6A3) and for the dopamine receptor D4 (DRD4); in the noradrenergic system, like the gene coding for the adrenergic alpha-2A receptor (ADRA2A), the COMT gene, which codes for the enzyme catechol-O-methyltransferase and the gene that codes for latrophilin 3 (LPHN3), as genes that are candidates for playing a part in the susceptibility to ADHD, and being involved in the pharmacological response as well as in the risk of presenting associated behavioural disorders. On the other hand, the genes involved in regulating the metabolism of the drugs used in the treatment of ADHD, such as the gene CYP2D6 and gene CES1, play a role in the efficiency and tolerance of these psycho-pharmaceuticals. CONCLUSIONS: Although in recent years there has been an increase in the number of pharmacogenetic studies conducted on ADHD, findings differ significantly from one study to another. Integrating and meta-analytical studies are needed to be able to develop a more personalised treatment for ADHD.

Association of neurexin 3 polymorphisms with smoking behavior.

The Neurexin 3 gene (NRXN3) has been associated with dependence on various addictive substances, as well as with the degree of smoking in schizophrenic patients and impulsivity among tobacco abusers. To further evaluate the role of NRXN3 in nicotine addiction, we analyzed single nucleotide polymorphisms (SNPs) and a copy number variant (CNV) within the NRXN3 genomic region. An initial study was carried out on 157 smokers and 595 controls, all of Spanish Caucasian origin. Nicotine dependence was assessed using the Fagerström index and the number of cigarettes smoked per day. The 45 NRXN3 SNPs genotyped included all the SNPs previously associated with disease, and a previously described deletion within NRXN3. This analysis was replicated in 276 additional independent smokers and 568 controls. Case-control association analyses were performed at the allele, genotype and haplotype levels. Allelic and genotypic association tests showed that three NRXN3 SNPs were associated with a lower risk of being a smoker. The haplotype analysis showed that one block of 16 Kb, consisting of two of the significant SNPs (rs221473 and rs221497), was also associated with lower risk of being a smoker in both the discovery and the replication cohorts, reaching a higher level of significance when the whole sample was considered [odds ratio = 0.57 (0.42-0.77), permuted P = 0.0075]. By contrast, the NRXN3 CNV was not associated with smoking behavior. Taken together, our results confirm a role for NRXN3 in susceptibility to smoking behavior, and strongly implicate this gene in genetic vulnerability to addictive behaviors.

Contribution of LPHN3 to the genetic susceptibility to ADHD in adulthood: a replication study.

Attention-deficit/hyperactivity disorder (ADHD) is a common and highly heritable developmental disorder characterized by a persistent impairing pattern of inattention and/or hyperactivity-impulsivity. Using families from a genetic isolate, the Paisa population from Colombia, and five independent datasets from four different populations (United States, Germany, Norway and Spain), a highly consistent association was recently reported between ADHD and the latrophilin 3 (LPHN3) gene, a brain-specific member of the LPHN subfamily of G-protein-coupled receptors that is expressed in ADHD-related regions, such as amygdala, caudate nucleus, cerebellum and cerebral cortex. To replicate the association between LPHN3 and ADHD in adults, we undertook a case-control association study in 334 adult patients with ADHD and 334 controls with 43 single nucleotide polymorphisms (SNPs) covering the LPNH3 gene. Single- and multiple-marker analyses showed additional evidence of association between LPHN3 and combined type ADHD in adulthood [P = 0.0019; df = 1; odds ratio (OR) = 1.82 (1.25-2.70) and P = 5.1e-05; df = 1; OR = 2.25 (1.52-3.34), respectively]. These results further support the LPHN3 contribution to combined type ADHD, and specifically to the persistent form of the disorder, and point at this new neuronal pathway as a common susceptibility factor for ADHD throughout the lifespan.

An international multicenter association study of the serotonin transporter gene in persistent ADHD.

Attention deficit hyperactivity disorder (ADHD) is a common behavioral disorder affecting children and adults. It has been suggested that gene variants related to serotonin neurotransmission are associated with ADHD. We tested the functional promoter polymorphism 5-HTTLPR and seven single nucleotide polymorphisms in SLC6A4 for association with ADHD in 448 adult ADHD patients and 580 controls from Norway. Replication attempts were performed in a sample of 1454 Caucasian adult ADHD patients and 1302 controls from Germany, Spain, the Netherlands and USA, and a meta-analysis was performed also including a previously published adult ADHD study. We found an association between ADHD and rs140700 [odds ratio (OR ) = 0.67; P = 0.01] and the short (S) allele of the 5-HTTLPR (OR = 1.19; P = 0.06) in the Norwegian sample. Analysis of a possible gender effect suggested that the association might be restricted to females (rs140700: OR = 0.45; P = 0.00084). However, the meta-analysis of 1894 cases and 1878 controls could not confirm the association for rs140700 [OR = 0.85, 95% confidence interval (CI) = 0.67-1.09; P = 0.20]. For 5-HTTLPR, five of six samples showed a slight overrepresentation of the S allele in patients, but meta-analysis refuted a strong effect (OR = 1.10, 95% CI = 1.00-1.21; P = 0.06). Neither marker showed any evidence of differential effects for ADHD subtype, gender or symptoms of depression/anxiety. In conclusion, our results do not support a major role for SLC6A4 common variants in persistent ADHD, although a modest effect of the 5-HTTLPR and a role for rare variants cannot be excluded.

Meta-analysis of brain-derived neurotrophic factor p.Val66Met in adult ADHD in four European populations.

Attention-deficit hyperactivity disorder (ADHD) is a multifactorial, neurodevelopmental disorder that often persists into adolescence and adulthood and is characterized by inattention, hyperactivity and impulsiveness. Before the advent of the first genome-wide association studies in ADHD, genetic research had mainly focused on candidate genes related to the dopaminergic and serotoninergic systems, although several other genes had also been assessed. Pharmacological data, analysis of animal models and association studies suggest that Brain-Derived Neurotrophic Factor (BDNF) is also a strong candidate gene for ADHD. Several polymorphisms in BDNF have been reported and studied in psychiatric disorders but the most frequent is the p.Val66Met (rs6265G > A) single nucleotide polymorphism (SNP), with functional effects on the intracellular trafficking and secretion of the protein. To deal with the inconsistency raised among different case-control and family-based association studies regarding the p.Val66Met contribution to ADHD, we performed a meta-analysis of published as well as unpublished data from four different centers that are part of the International Multicentre Persistent ADHD CollaboraTion (IMpACT). A total of 1,445 adulthood ADHD patients and 2,247 sex-matched controls were available for the study. No association between the p.Val66Met polymorphism and ADHD was found in any of the four populations or in the pooled sample. The meta-analysis also showed that the overall gene effect for ADHD was not statistically significant when gender or comorbidity with mood disorders were considered. Despite the potential role of BDNF in ADHD, our data do not support the involvement of p.Val66Met in the pathogenesis of this neuropsychiatric disorder.