The genetic basis of Gilles de la Tourette Syndrome

Mechanistic insights and therapeutic approaches in tic disorders: The distinctive role of ethnomedicine and modern medical interventions

Tic disorders (TDs) are a class of neurodevelopmental disorders that have received considerable scientific attention. The genesis of TDs is increasingly understood as a complex interplay of neurobiological, genetic, and immunological factors. Animal model studies have elucidated the pathophysiology of TDs, paving the way for innovative therapeutic approaches. This review provides a comprehensive analysis of the etiologic basis, experimental framework, and treatment strategies for TDs, highlighting the contributions of ethnomedicine and modern medicine. Our synthesis aims to deepen the understanding of the disease and spur the development of superior treatments. In addition, we present new insights and hypotheses for the future management of TDs, emphasizing the need for continued research into their etiology and progression, as well as the pursuit of more effective therapies. We advocate personalized, holistic care strategies that focus on symptom relief and improving patients' quality of life. Overall, this review provides a critical compendium for TD researchers and practitioners to help navigate the complexities of these disorders.

Genetic architecture of tic disorders: A systematic review of 125 observational studies

BACKGROUND

To summarize and evaluate recent advances in the genetics of tic disorders (TDs) and to understand the possible pathogenic mechanisms behind this disorder.

METHODS

PubMed, EMBASE, the Cochrane Library, and four Chinese databases were searched from inception to September 2022. Observational original studies that explored genetic or chromosomal variations associated with the etiology, diagnosis, treatment, or prognosis of TDs were included. The Strengthening the Reporting of Genetic Association Studies (STREGA) statement was used to evaluate the quality of the included studies.

RESULTS

125 studies were finally included with 119 of moderate quality and 6 of low quality. A total of 32,439 cases with different types of TDs and 81,923 controls were included. The results involved 98 genes, 16 chromosomes, and multiple gene sets. Genome-wide studies were also included. The top three systems were the dopamine system, nervous system development, and the serotonin system. 96 loci in 56 genes and 20 regions in 14 chromosomes were reported to be relevant to TDs, with SLC6A4 (serotonin system) and NTN4 genes being relatively strongly correlated with the occurrence of TS, and ACP1 (serotonin system) and DBH (dopamine system) being relatively strongly correlated with TS comorbid with attention deficit hyperactivity disorder (ADHD).

CONCLUSION

Polygenic loci were found to play a key role in the occurrence and development of TDs. However, the applicability of the findings may be limited due to the small sample size, single-center design and the limited study quality of included studies. Future research with more comprehensive study designs and improved reporting transparency is needed to confirm the findings.

Network Pharmacology Combined with Animal Models to Investigate the Mechanism of ChangPu YuJin Tang in the Treatment of Tourette Syndrome

BACKGROUND

ChangPu YuJin Tang (CPYJT) is a Chinese herbal formula that has been shown to be an effective therapeutic strategy for pediatric patients with Tourette Syndrome (TS). Using an integrated strategy of network pharmacology and animal model, the aim of this study was to investigate the mechanism of CPYJT in the treatment of TS.

METHODS

Compound libraries of CPYJT were established using databases, such as the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP). The TCMSP database and Swiss Target Prediction database were used to predict the targets. The above results were constructed into a CPYJT-Drug-Component-Target network. Moreover, TS targets were predicted using GeneCards and other databases. The targets corresponding to the potential ingredients in CPYJT and the targets corresponding to TS were taken as the intersections to construct the CPYJT-TS network. The target network was analysed by PPI using the string database. GO and KEGG enrichment analyses were performed on the target network. The whole process was performed using Cytoscape 3.7.2 to make visual network diagrams of the results. CPYJT was characterised by Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry (UHPLC-MS). Transmission Electron Microscopy (TEM) was used to observe the structural changes of CPYJT on the neuronal cells of the IDPN model rats. RT-PCR and Western Blot were used to analyse the changes in the mRNA and protein expression levels of BDNF, TrkB, PI3K, and AKT in the cortex, striatum, and thalamus brain regions after CPYJT administration in IDPN model rats.

RESULTS

Network pharmacology and UHPLC-MS studies revealed that CPYJT acted on the TS through multiple neurotransmitters and the BDNF/TrkB and PI3K/AKT signalling pathways. CPYJT ameliorated neurocellular structural damage in the cortex, striatum, and thalamus of TS model rats. Additionally, CPYJT up-regulated the levels of BDNF, TrkB, PI3k, and AKT in the cortex, striatum, and thalamus of TS model rats.

CONCLUSION

It was found that CPYJT protected neuronal cells from structural damage in multiple brain regions and affected the expression levels of BDNF, TrkB, PI3K, and Akt in the cortex, striatum, and thalamus during TS treatment.

Advances in Clustering and Classification of Tic Disorders: A Systematic Review

Purpose

Tic disorders (TD) are common neurodevelopmental disorders characterized by heterogeneous tic symptoms in children, making diagnostic classification difficult. This complexity requires accurate subtyping using data-driven computational methods to identify patterns within clinical data. This systematic review primarily summarizes the current evidence for the classification of TD using a data-driven approach.

Patients and Methods

We conducted a systematic literature search on PubMed and Web of Science up to December 2023 and identified 16 publications analyzing 14 unique samples, totaling approximately 6000 subjects.

Results

Nine studies classified different subtypes of TD based on symptoms and behavior. Seven studies identified novel factor structures based on TD and its complex comorbidity patterns. Seven studies highlighted associations between TD symptom patterns and genetics, reflecting the diversity of underlying genetic mechanisms underlying TD.

Conclusion

This systematic review reveals significant variability in research on the classification of TD, which limits the application of findings for accurate diagnosis and guiding treatment strategies in pediatric psychiatry. Further research incorporating multidimensional information (such as genetic, neuroimaging, and environmental and social factors) is essential to improve the understanding of TD subtypes.

Structural Variants and Implicated Processes Associated with Familial Tourette Syndrome

Gilles de la Tourette syndrome (GTS) is a neurodevelopmental psychiatric disorder with complex and elusive etiology with a significant role of genetic factors. The aim of this study was to identify structural variants that could be associated with familial GTS. The study group comprised 17 multiplex families with 80 patients. Structural variants were identified from whole-genome sequencing data and followed by co-segregation and bioinformatic analyses. The localization of these variants was used to select candidate genes and create gene sets, which were subsequently processed in gene ontology and pathway enrichment analysis. Seventy putative pathogenic variants shared among affected individuals within one family but not present in the control group were identified. Only four private or rare deletions were exonic in LDLRAD4, B2M, USH2A, and ZNF765 genes. Notably, the USH2A gene is involved in cochlear development and sensory perception of sound, a process that was associated previously with familial GTS. In addition, two rare variants and three not present in the control group were co-segregating with the disease in two families, and uncommon insertions in GOLM1 and DISC1 were co-segregating in three families each. Enrichment analysis showed that identified structural variants affected synaptic vesicle endocytosis, cell leading-edge organization, and signaling for neurite outgrowth. The results further support the involvement of the regulation of neurotransmission, neuronal migration, and sound-sensing in GTS.

Impacts of ADHD Symptomatology on the Response to Cognitive-Behavioural Therapy with Gilles de la Tourette Syndrome Patients

(1) Background: Gilles de la Tourette Syndrome (TS) is a neurodevelopmental disorder characterized by motor and vocal tics. Attention deficit and hyperactivity disorder (ADHD) is a common comorbidity of TS that adds further impairment. Cognitive-behavioural therapy (CBT) has shown efficacy in treating tics, yet its effectiveness in individuals with TS and comorbid ADHD remains unclear. Also, it is suggested that ADHD characteristics like executive dysfunction and inattention could hinder the response to CBT. This study aims to compare the response to CBT for tics and its maintenance six months post-therapy among TS individuals with and without ADHD symptoms. (2) Methods: In this study, 55 TS participants who completed 14-week CBT for tics were split into high (TS+) or low (TS-) ADHD symptomatology groups. Outcomes were evaluated using the Yale Global Tic Severity Scale (YGTSS) regarding global tic severity and motor and vocal tic frequency post-CBT and at a 6-month follow-up. (3) Results: No significant group difference was found regarding improvements post-CBT (n = 55), nor the maintenance six months later (n = 45). (4) Conclusions: ADHD symptoms may not hinder the response to CBT or its maintenance, suggesting that TS individuals with ADHD symptoms may not require specialized CBT interventions.

G protein-coupled receptors in neurodegenerative diseases and psychiatric disorders

Neuropsychiatric disorders are multifactorial disorders with diverse aetiological factors. Identifying treatment targets is challenging because the diseases are resulting from heterogeneous biological, genetic, and environmental factors. Nevertheless, the increasing understanding of G protein-coupled receptor (GPCR) opens a new possibility in drug discovery. Harnessing our knowledge of molecular mechanisms and structural information of GPCRs will be advantageous for developing effective drugs. This review provides an overview of the role of GPCRs in various neurodegenerative and psychiatric diseases. Besides, we highlight the emerging opportunities of novel GPCR targets and address recent progress in GPCR drug development.

Copy Number Variations in Children with Tourette Syndrome: Systematic Investigation in a Clinical Setting

Tourette syndrome (TS) is a neurodevelopmental disturbance with heterogeneous and not completely known etiology. Clinical and molecular appraisal of affected patients is mandatory for outcome amelioration. The current study aimed to understand the molecular bases underpinning TS in a vast cohort of pediatric patients with TS. Molecular analyses included array-CGH analyses. The primary goal was to define the neurobehavioral phenotype of patients with or without pathogenic copy number variations (CNVs). Moreover, we compared the CNVs with CNVs described in the literature in neuropsychiatric disorders, including TS, to describe an effective clinical and molecular characterization of patients for prognostic purposes and for correctly taking charge. Moreover, this study showed that rare deletions and duplications focusing attention on significant genes for neurodevelopment had a statistically higher occurrence in children with tics and additional comorbidities. In our cohort, we determined an incidence of potentially causative CNVs of about 12%, in line with other literature studies. Clearly, further studies are needed to delineate the genetic background of patients with tic disorders in a superior way to elucidate the complex genetic architecture of these disorders, to describe the outcome, and to identify new possible therapeutic targets.

Association of Pre- and Perinatal Risk Factors With Tourette Syndrome or Chronic Tic Disorders in a Korean School-Age Population

Objectives

Tic disorders are highly heritable; however, growing evidence suggests that environmental factors play a significant role in their pathogenesis. Studies on these factors have been inconsistent, with conflicting results. Therefore, this study aimed to examine the associations of pre- and perinatal exposure to Tourette syndrome (TS) or chronic tic disorders (CTD) in Korean school-aged children.

Methods

This case-control study used data from a large prospective cohort study. The primary outcome was TS/CTD diagnosis according to the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5) criteria and Kiddie-Schedule for Affective Disorders and Schizophrenia-Present and Lifetime Version-Korean Version. Demographic, pre-, and perinatal information was obtained from the maternal questionnaires. Data between the TS/CTD and control groups were compared using the chi-squared or Student's t-test, as appropriate. Two-step logistic regression analyses were used to test the association between TS/CTD and pre- and perinatal risk factors.

Results

We included of 223 children (78 with TS/CTD and 145 controls). Significant differences in the demographic data between the two groups were observed. The male sex ratio, mean parental age, parental final education level, and family history of tics were included as confounders. In the final adjusted multivariable model, TS/CTD was significantly associated with antiemetic exposure during pregnancy (odds ratio [OR]=16.61, 95% confidence interval [CI] 1.49-185.22, p=0.02) and medically assisted reproduction (OR=7.89, 95% CI 2.28-27.28, p=0.01).

Conclusion

Antiemetic exposure and medically assisted reproduction are significantly associated with the risk of TS/CTD. These results should be replicated in future prospective and gene-by-environment studies.

Comprehensive exploration of the genetic contribution of the dopaminergic and serotonergic pathways to psychiatric disorders

Psychiatric disorders are highly prevalent and display considerable clinical and genetic overlap. Dopaminergic and serotonergic neurotransmission have been shown to play an important role in many psychiatric disorders. Here we aim to assess the genetic contribution of these systems to eight psychiatric disorders (attention-deficit hyperactivity disorder (ADHD), anorexia nervosa (ANO), autism spectrum disorder (ASD), bipolar disorder (BIP), major depression (MD), obsessive-compulsive disorder (OCD), schizophrenia (SCZ) and Tourette's syndrome (TS)) using publicly available GWAS analyses performed by the Psychiatric Genomics Consortium that include more than 160,000 cases and 275,000 controls. To do so, we elaborated four different gene sets: two 'wide' selections for dopamine (DA) and for serotonin (SERT) using the Gene Ontology and KEGG pathways tools, and two'core' selections for the same systems, manually curated. At the gene level, we found 67 genes from the DA and/or SERT gene sets significantly associated with one of the studied disorders, and 12 of them were associated with two different disorders. Gene-set analysis revealed significant associations for ADHD and ASD with the wide DA gene set, for BIP with the wide SERT gene set, and for MD with the core SERT set. Interestingly, interrogation of a cross-disorder GWAS meta-analysis of the eight psychiatric conditions displayed association with the wide DA gene set. To our knowledge, this is the first systematic examination of genes encoding proteins essential to the function of these two neurotransmitter systems in these disorders. Our results support a pleiotropic contribution of the dopaminergic and serotonergic systems in several psychiatric conditions.

Enhancing neuroimaging genetics through meta-analysis for Tourette syndrome (ENIGMA-TS): A worldwide platform for collaboration

Tourette syndrome (TS) is characterized by multiple motor and vocal tics, and high-comorbidity rates with other neuropsychiatric disorders. Obsessive compulsive disorder (OCD), attention deficit hyperactivity disorder (ADHD), autism spectrum disorders (ASDs), major depressive disorder (MDD), and anxiety disorders (AXDs) are among the most prevalent TS comorbidities. To date, studies on TS brain structure and function have been limited in size with efforts mostly fragmented. This leads to low-statistical power, discordant results due to differences in approaches, and hinders the ability to stratify patients according to clinical parameters and investigate comorbidity patterns. Here, we present the scientific premise, perspectives, and key goals that have motivated the establishment of the Enhancing Neuroimaging Genetics through Meta-Analysis for TS (ENIGMA-TS) working group. The ENIGMA-TS working group is an international collaborative effort bringing together a large network of investigators who aim to understand brain structure and function in TS and dissect the underlying neurobiology that leads to observed comorbidity patterns and clinical heterogeneity. Previously collected TS neuroimaging data will be analyzed jointly and integrated with TS genomic data, as well as equivalently large and already existing studies of highly comorbid OCD, ADHD, ASD, MDD, and AXD. Our work highlights the power of collaborative efforts and transdiagnostic approaches, and points to the existence of different TS subtypes. ENIGMA-TS will offer large-scale, high-powered studies that will lead to important insights toward understanding brain structure and function and genetic effects in TS and related disorders, and the identification of biomarkers that could help inform improved clinical practice.

Candidate Genes and Pathways Associated with Gilles de la Tourette Syndrome-Where Are We?

Gilles de la Tourette syndrome (GTS) is a childhood-onset neurodevelopmental and -psychiatric tic-disorder of complex etiology which is often comorbid with obsessive-compulsive disorder (OCD) and/or attention deficit hyperactivity disorder (ADHD). Twin and family studies of GTS individuals have shown a high level of heritability suggesting, that genetic risk factors play an important role in disease etiology. However, the identification of major GTS susceptibility genes has been challenging, presumably due to the complex interplay between several genetic factors and environmental influences, low penetrance of each individual factor, genetic diversity in populations, and the presence of comorbid disorders. To understand the genetic components of GTS etiopathology, we conducted an extensive review of the literature, compiling the candidate susceptibility genes identified through various genetic approaches. Even though several strong candidate genes have hitherto been identified, none of these have turned out to be major susceptibility genes yet.

Role of Ash1l in Tourette syndrome and other neurodevelopmental disorders

Ash1l potentially contributes to neurodevelopmental diseases. Although specific Ash1l mutations are rare, they have led to informative studies in animal models that may bring therapeutic advances. Ash1l is highly expressed in the brain and correlates with the neuropathology of Tourette syndrome (TS), autism spectrum disorder, and intellectual disability during development, implicating shared epigenetic factors and overlapping neuropathological mechanisms. Functional convergence of Ash1l generated several significant signaling pathways: chromatin remodeling and transcriptional regulation, protein synthesis and cellular metabolism, and synapse development and function. Here, we systematically review the literature on Ash1l, including its discovery, expression, function, regulation, implication in the nervous system, signaling pathway, mutations, and putative involvement in TS and other neurodevelopmental traits. Such findings highlight Ash1l pleiotropy and the necessity of transcending a single gene to complicated mechanisms of network convergence underlying these diseases. With the progress in functional genomic analysis (highlighted in this review), and although the importance and necessity of Ash1l becomes increasingly apparent in the medical field, further research is required to discover the precise function and molecular regulatory mechanisms related to Ash1l. Thus, a new perspective is proposed for basic scientific research and clinical interventions for cross-disorder diseases.

The α6 GABAA Receptor Positive Allosteric Modulator DK-I-56-1 Reduces Tic-Related Behaviors in Mouse Models of Tourette Syndrome

Tourette syndrome (TS) is a disabling neurodevelopmental disorder characterized by multiple, recurrent tics. The pharmacological treatment of TS is currently based on dopaminergic antagonists; however, these drugs are associated with extrapyramidal symptoms and other serious adverse events. Recent evidence suggests that positive allosteric modulators (PAMs) of GABA_A receptors containing α6 subunits (α6 GABA_ARs) oppose the behavioral effects of dopamine. Building on this evidence, in the present study, we tested the efficacy of DK-I-56-1, a highly selective PAM for α6 GABA_ARs, in mouse models of TS exhibiting tic-related responses. DK-I-56-1 significantly reduced tic-like jerks and prepulse inhibition (PPI) deficits in D1CT-7 transgenic mice, a well-documented mouse model of TS. DK-I-56-1 also prevented the exacerbation of spontaneous eyeblink reflex induced by the potent dopamine D₁ receptor agonist SKF 82958, a proxy for tic-like responses. We also showed that both systemic and prefrontal cortical administration of DK-I-56-1 countered the PPI disruption caused by SKF 82958. Although the effects of DK-I-56-1 were akin to those elicited by dopaminergic antagonists, this drug did not elicit extrapyramidal effects, as measured by catalepsy. These results point to α6 GABA_AR PAMs as promising TS therapies with a better safety profile than dopaminergic antagonists.

Association of Genetic Variation in the 3'UTR of LHX6, IMMP2L, and AADAC With Tourette Syndrome

Background: Tourette Syndrome (TS) is a neurodevelopmental disorder that presents with motor and vocal tics early in childhood. The aim of this study was to investigate genetic variants in the 3' untranslated region (3'UTR) of TS candidate genes with a putative link to microRNA (miRNA) mediated regulation or gene expression. Methods: We used an in silico approach to identify 32 variants in the 3'UTR of 18 candidate genes putatively changing the binding site for miRNAs. In a sample composed of TS cases and controls (n = 290), as well as TS family trios (n = 148), we performed transmission disequilibrium test (TDT) and meta-analysis. Results: We found positive association of rs3750486 in the LIM homeobox 6 (LHX6) gene (p = 0.021) and rs7795011 in the inner mitochondrial membrane peptidase subunit 2 (IMMP2L) gene (p = 0.029) with TS in our meta-analysis. The TDT showed an over-transmission of the A allele of rs1042201 in the arylacetamide deacetylase (AADAC) gene in TS patients (p = 0.029). Conclusion: This preliminary study provides further support for the involvement of LHX6, IMMP2L, and AADAC genes, as well as epigenetic mechanisms, such as altered miRNA mediated gene expression regulation in the etiology of TS.

The cognitive neuropsychiatry of Tourette syndrome

Introduction: Converging evidence from both clinical and experimental studies has shown that Tourette syndrome (TS) is not a unitary condition, but a cluster of multiple phenotypes, which encompass both tics and specific behavioural and cognitive symptoms (mainly attention-deficit and hyperactivity disorder and obsessive-compulsive disorder). Methods: We conducted a narrative review of the recent literature on the cognitive neuropsychiatry of TS. Results: Although clinical research has shown that TS is not associated with cognitive deficits per se, the findings of recent studies have suggested the presence of subtle alterations in specific cognitive functions. A promising line of research on imitative behaviour could provide a common background for the alterations in executive control and social cognition observed in TS. Two different (but not mutually exclusive) neurocognitive theories have recently suggested that TS could originate from altered perception-action binding and social decision-making dysfunction, respectively. Conclusions: Since the presence of behavioural comorbidities influences individualised treatment approaches, it is likely that a more precise characterisation of TS phenotypes, including cognitive aspects, will result in improved levels of care for patients with tic disorders.

Pharmacogenomics of Pain Management: The Impact of Specific Biological Polymorphisms on Drugs and Metabolism

PURPOSE OF REVIEW

Pain is multifactorial and complex, often with a genetic component. Pharmacogenomics is a relative new field, which allows for the development of a truly unique and personalized therapeutic approach in the treatment of pain.

RECENT FINDINGS

Until recently, drug mechanisms in humans were determined by testing that drug in a population and calculating response averages. However, some patients will inevitably fall outside of those averages, and it is nearly impossible to predict who those outliers might be. Pharmacogenetics considers a patient's unique genetic information and allows for anticipation of that individual's response to medication. Pharmacogenomic testing is steadily making progress in the management of pain by being able to identify individual differences in the perception of pain and susceptibility and sensitivity to drugs based on genetic markers. This has a huge potential to increase efficacy and reduce the incidence of iatrogenic drug dependence and addiction. The streamlining of relevant polymorphisms of genes encoding receptors, transporters, and drug-metabolizing enzymes influencing the pain phenotype can be an important guide to develop safe new strategies and approaches to personalized pain management. Additionally, some challenges still prevail and preclude adoption of pharmacogenomic testing universally. These include lack of knowledge about pharmacogenomic testing, inadequate standardization of the process of data handling, questionable benefits about the clinical and financial aspects of pharmacogenomic testing-guided therapy, discrepancies in clinical evidence supporting these tests, and doubtful reimbursement of the tests by health insurance agencies.

Tourette's disorder in children and adolescents

Tourette's disorder (TD) is one of the five American Psychiatric Association's 2013 Diagnostic and Statistical Manual of Mental Disorders (DSM-5) classifications of tic disorders. Eponymously linked with the noted 19th century French physician, Gilles de la Tourette [1857-1904], this disorder is identified in 0.3% to 0.7% of the population. It is characterized as a familial neuropsychiatric condition with multiple motor tics and vocal tics (one or more) present for more than 1 year with varying severity. The underlying pathophysiology involves dysfunctional activity of the basal ganglia and circuitry of the frontal cortex as well as dorsolateral striatum deficits. Contributory factors include genetic features interacting with milieu influences. A number of comorbid disorders are seen including obsessive-compulsive disorder (OCD) and attention-deficit/hyperactivity disorder (ADHD). Concepts of management are considered including behavioral therapy and pharmacologic approaches with alpha-adrenoceptor agonists, atypical antipsychotics (AAs), haloperidol, pimozide and others. Other management includes botulinum injections and deep brain stimulation in adults.

Social stigma and self-perception in adolescents with tourette syndrome

Tourette syndrome (TS) is a complex neurodevelopmental disorder characterized by multiple motor and vocal tics, which commonly presents with multiple behavioral problems, including co-morbid attention-deficit and hyperactivity disorder and obsessive-compulsive disorder. Both tics and co-morbid conditions have been shown to potentially affect patients’ health-related quality of life. While TS typically presents in childhood, its manifestations peak in severity during adolescence, a critical period in which affected individuals are exposed to potential stigma from peers. Physical and behavioral manifestations can also contribute to stigma, which subsequently leads to poorer health outcomes, discrimination, and a reduced willingness to seek help. The available evidence suggests that young patients with TS can experience reduced social acceptance from peers and difficulties establishing relationships. There is also evidence that some health care professionals share the unhelpful belief that young patients with TS should be disciplined in order to correct their disruptive behavior, based on the erroneous assumption that tics can be consciously controlled. Studies focussed on self-perception in patients with TS have yielded inconsistent results, with some studies showing problems in the domains of self-concept and self-esteem. Feelings of isolation, loneliness, and experiences of bullying have been reported more consistently. Interventions are required to reduce misconceptions about the condition and thus reduce stigma through targeted education and behavioral interventions. A multi-faceted approach that focuses on educating children, adults, and educators about TS would be beneficial to help alleviate stigma. This can be combined with self-advocacy and tailored psychological therapies for young patients with TS. The present paper reviews the current literature on stigma and self-perception in adolescents with TS in order to inform clinical decisions about management strategies and possible interventions to improve health-related quality of life.

Pure delta-9-tetrahydrocannabinol and its combination with cannabidiol in treatment-resistant Tourette syndrome: A case report

OBJECTIVES

Anecdotal reports and preliminary studies suggest a therapeutic potential of cannabis in Tourette syndrome. We report the case of a female patient suffering from treatment-resistant Tourette syndrome.

METHODS

Guideline-directed antipsychotic treatment with risperidone and aripiprazole as well as pure delta-9-tetrahydrocannabinol had no significant effect on Tourette syndrome symptomatology.

RESULTS

Following administration of a daily dosage of 10 mg delta-9-tetrahydrocannabinol combined with 20 mg cannabidiol (CBD), the patient showed a rapid and highly significant improvement in the Yale Global Tic Severity Scale.

CONCLUSIONS

It can be speculated whether the beneficial effects may rely on the pharmacological properties of cannabidiol.

Heroin Addiction in Serbian Patients With Tourette Syndrome

INTRODUCTION

Tourette syndrome (TS) is a neurodevelopmental disorder with a high prevalence of psychiatric comorbidity. The most common comorbid disorder in patients with TS is attention-deficit/hyperactivity disorder (ADHD). To date, there have been few reports concerning the association of TS with addiction.

METHODS

We report on 4 patients with TS, ADHD, and heroin addiction.

RESULTS

All 4 patients were male and initially presented with TS when they were between 5 and 12 years of age, although 2 of the patients were not diagnosed with TS until they were adults. The patients currently range in age from 21 to 52 years, all having experienced the onset of heroin addiction in adolescence. A reduction in tics during periods of heroin abuse was noted in all patients.

DISCUSSION

The lifetime prevalence of psychiatric comorbidity in patients with TS is 85.7%, with 57.7% of patients having ≥2 psychiatric conditions in addition to TS. All of the 4 patients in our case series demonstrated a pattern of severe tics, ADHD, impulsive behavior, and heroin addiction. Our observation that these 4 patients with TS showed reduced tics during periods of heroin dependence could be related to the previously described effects of opiates on dopaminergic transmission.

CONCLUSIONS

The observed reduction of tics during heroin dependence warrants further clinical research.

Perinatal risk factors in Tourette's and chronic tic disorders: a total population sibling comparison study

Adverse perinatal events may increase the risk of Tourette's and chronic tic disorders (TD/CTD), but previous studies have been unable to control for unmeasured environmental and genetic confounding. We aimed to prospectively investigate potential perinatal risk factors for TD/CTD, taking unmeasured factors shared between full siblings into account. A population-based birth cohort, consisting of all singletons born in Sweden in 1973-2003, was followed until December 2013. A total of 3 026 861 individuals were identified, 5597 of which had a registered TD/CTD diagnosis. We then studied differentially exposed full siblings from 947 942 families; of these, 3563 families included siblings that were discordant for TD/CTD. Perinatal data were collected from the Medical Birth Register and TD/CTD diagnoses were collected from the National Patient Register, using a previously validated algorithm. In the fully adjusted models, impaired fetal growth, preterm birth, breech presentation and cesarean section were associated with a higher risk of TD/CTD, largely independent from shared family confounders and measured covariates. Maternal smoking during pregnancy was associated with risk of TD/CTD in a dose-response manner but the association was no longer statistically significant in the sibling comparison models or after the exclusion of comorbid attention-deficit/hyperactivity disorder. A dose-response relationship between the number of adverse perinatal events and increased risk for TD/CTD was also observed, with hazard ratios ranging from 1.41 (95% confidence interval (CI): 1.33-1.50) for one event to 2.42 (95% CI: 1.65-3.53) for five or more events. These results pave the way for future gene by environment interaction and epigenetic studies in TD/CTD.

Sensory aspects of Tourette syndrome

Motor and vocal tics have long been recognised as the core features of Tourette syndrome (TS). However, patients' first-person accounts have consistently reported that these involuntary motor manifestations have specific sensory correlates. These sensory symptoms are often described as feelings of mounting inner tension ("premonitory urges") and are transiently relieved by tic expression. Multimodal hypersensitivity to external stimuli, perceived as triggers and/or exacerbating factors for specific tic symptoms, is also commonly reported by patients with TS. This article focuses on the rapidly expanding literature on the clinical and neurobiological aspects of the premonitory urge and multimodal hypersensitivity in patients with TS, with particular attention to pathophysiological mechanisms and possible treatment implications. These findings suggest that TS is a neurobehavioural condition characterised by intrinsic perceptual abnormalities involving the insula and sensorimotor areas, in addition to basal ganglia dysfunction. Further research will clarify the role of sensory symptoms in TS, as well as the effects of external sensory input on underlying motor abnormalities.

Tourette disorder and other tic disorders

Tourette disorder is a developmental neuropsychiatric condition characterized by vocal and motor tics that can range in severity from mild to disabling. It represents one end of a spectrum of tic disorders and is estimated to affect 0.5-0.7% of the population. Accumulated evidence supports a substantial genetic contribution to disease risk, but the identification of genetic variants that confer risk has been challenging. Positive findings in candidate gene association studies have not replicated, and genomewide association studies have not generated signals of genomewide significance, in large part because of inadequate sample sizes. Rare mutations in several genes have been identified, but their causality is difficult to establish. As in other complex neuropsychiatric disorders, it is likely that Tourette disorder risk involves a combination of common, low-effect and rare, larger-effect variants in multiple genes acting together with environmental factors. With the ongoing collection of larger patient cohorts and the emergence of affordable high-throughput genomewide sequencing, progress is expected to accelerate in coming years.

Investigation of previously implicated genetic variants in chronic tic disorders: a transmission disequilibrium test approach

Genetic studies in Tourette syndrome (TS) are characterized by scattered and poorly replicated findings. We aimed to replicate findings from candidate gene and genome-wide association studies (GWAS). Our cohort included 465 probands with chronic tic disorder (93% TS) and both parents from 412 families (some probands were siblings). We assessed 75 single nucleotide polymorphisms (SNPs) in 465 parent-child trios; 117 additional SNPs in 211 trios; and 4 additional SNPs in 254 trios. We performed SNP and gene-based transmission disequilibrium tests and compared nominally significant SNP results with those from a large independent case-control cohort. After quality control 71 SNPs were available in 371 trios; 112 SNPs in 179 trios; and 3 SNPs in 192 trios. 17 were candidate SNPs implicated in TS and 2 were implicated in obsessive-compulsive disorder (OCD) or autism spectrum disorder (ASD); 142 were tagging SNPs from eight monoamine neurotransmitter-related genes (including dopamine and serotonin); 10 were top SNPs from TS GWAS; and 13 top SNPs from attention-deficit/hyperactivity disorder, OCD, or ASD GWAS. None of the SNPs or genes reached significance after adjustment for multiple testing. We observed nominal significance for the candidate SNPs rs3744161 (TBCD) and rs4565946 (TPH2) and for five tagging SNPs; none of these showed significance in the independent cohort. Also, SLC1A1 in our gene-based analysis and two TS GWAS SNPs showed nominal significance, rs11603305 (intergenic) and rs621942 (PICALM). We found no convincing support for previously implicated genetic polymorphisms. Targeted re-sequencing should fully appreciate the relevance of candidate genes.

Association of the AADAC gene and Tourette syndrome in a Han Chinese cohort

Tourette syndrome (TS) is a complex neuropsychiatric disorder with chronic motor and vocal tics. Though the etiology is elusive, strong evidence for a genetic contribution to TS has been established. To date, various chromosomal or genetic alterations have been implicated in its pathogenesis. Recently, the deletion in the arylacetamide deacetylase gene (AADAC) was reported to be associated with TS. To investigate the association between the AADAC gene variants and TS, we conducted genetic analysis of the AADAC gene in 200 Han Chinese patients and 300 ethnicity-matched normal controls. Two variants, including a heterozygous splice-site variant, c.361 + 1G > A (rs762169706), and a missense variant, c.744A > T (p.R248S, rs186388618), were identified in two unrelated patients. The c.361 + 1G > A variant, absent in 300 ethnicity-matched controls, led to the deletion of exon 2 in AADAC mRNA, probably associated with development of TS. The c.744A > T variant, predicted to be damaging, was identified in two normal controls. The findings indicate that the AADAC gene c.361 + 1G > A variant may be a potential candidate factor for TS development, though further investigations are warranted.

Association between the polymorphism of C861G (rs6296) in the serotonin 1B receptor gene and Tourette syndrome in Han Chinese people

INTRODUCTION

Clinical, neuroimaging and other studies provided evidence that the dysfunction of the serotonin neurotransmitter system were found in Tourette syndrome (TS). This study is to explore the association between the polymorphism of C861G (rs6296) in HTR1B and TS in Han Chinese people.

METHODS

Two hundred ninety-nine TS patients (260 TS trios and 39 TS patients) and 388 healthy controls were collected. The genotype of HTR1B C861G was detected using Taqman probes. The case-control study and family-based study was used separately to study association between HTR1B C861G and TS in Han Chinese people.

RESULTS

In case-control study, no statistically significant difference was found in the distribution of HTR1B C861G polymorphism between TS patients and controls (for genotype: χ²  = 3.408, P = 0.182; for allele: χ²  = 0.395, P = 0.530, OR = 0.934, 95%CI: 0.754-1.156). In family-based study, we observed nonsignificant over-transmission of the G861 allele in HTR1B to TS offspring using the transmission disequilibrium test (TDT), haplotype relative risk (HRR) and haplotype-based HRR (HHRR) (TDT χ²  = 0.410, P = 0.560; HRR = 1.151, χ²  = 0.421, P = 0.517, 95% CI: 0.753-1.759; HHRR = 0.919, χ²  = 0.467, P = 0.495, 95%CI: 0.720-1.172).

DISCUSSION

Our study suggested that the polymorphism of HTR1B C861G is not a risk factor for TS in Han Chinese population. However, the result should be replicated in larger sample and different population.

Gilles de la Tourette syndrome is associated with hypermethylation of the dopamine D2 receptor gene

Several lines of evidence support a "dopaminergic hypothesis" in the pathophysiology of Gilles de la Tourette syndrome (TS). The aim of this study was to investigate for the first time epigenetic changes in DNA methylation in different dopamine genes in adult patients with TS. We included 51 well characterized adult patients with TS (41 males, 10 females, mean age = 35 ± 12.6 years, range, 18-71 years) and compared results with data from a group of 51 sex- and age-matched healthy controls. Bisulfite sequencing was used to measure peripheral DNA methylation of the dopamine transporter (DAT), the dopamine D2 receptor (DRD2), and the catechol-O-methyltransferase (COMT) genes. Compared to healthy controls, patients with TS showed significantly elevated methylation level of the DRD2 gene that positively correlated with tic severity. In contrast, DAT methylation was lower in more severely affected patients. Our results provide evidence for a role of altered epigenetic regulation of dopaminergic genes in the pathophysiology of TS. While DRD2 hypermethylation seems to be directly related to the neurobiology of TS that may lead to dopaminergic dysfunction resulting in enhanced thalamo-cortical movement-stimulating activity, DAT hypomethylation might reflect a secondary mechanism in order to compensate for increased dopaminergic signal transduction due to DRD2 hypermethylation. In addition, it can be speculated that spontaneous fluctuations of tics may be caused by short-term alterations of methylation levels of dopaminergic genes resulting in dynamic changes of tonic/phasic dopaminergic signaling in the striatum and thalamo-cortical output pathways.

A search for the common ground between Tic; Obsessive-compulsive and Autism Spectrum Disorders: part I, Tic disorders

This article is the first of four articles designed to explore the complex interrelationship between Autism Spectrum Disorders (ASD); Obsessive compulsive and Related Disorders (OCRD) and Tic Disorders/Tourette's Syndrome (TD/TS). We begin with an overview TD/TS and follow-up with reviews of OCRD and ASD. The final article in this series represents a synthesis of the neurobiological and genetic markers shared by patients presenting with all three syndromes. The goal is to describe the complex endophenotype of these patients in an effort to better define gene markers that underlie these heterogeneous clinical syndromes. Tic disorders (TD) are a collection of hyperkinetic movements that begin in early childhood. Tics are transient for most affected preschool children but a subgroup development persistent movements or progress to develop Tourette Syndrome (TS). TDs as a group display high heritability rates but definitive gene markers still elude us. The difficulty defining genetic markers is in large part due to the diverse neurodevelopmental trajectory, changing topography and typology, development of a broad spectrum of neurocognitive and behavioral complications, and a mixed pattern of psychiatric comorbidities.

Gilles de la Tourette syndrome

Gilles de la Tourette syndrome (GTS) is a childhood-onset neurodevelopmental disorder that is characterized by several motor and phonic tics. Tics usually develop before 10 years of age, exhibit a waxing and waning course and typically improve with increasing age. A prevalence of approximately 1% is estimated in children and adolescents. The condition can result in considerable social stigma and poor quality of life, especially when tics are severe (for example, with coprolalia (swearing tics) and self-injurious behaviours) or when GTS is accompanied by attention-deficit/hyperactivity disorder, obsessive-compulsive disorder or another neuropsychiatric disorder. The aetiology is complex and multifactorial. GTS is considered to be polygenic, involving multiple common risk variants combined with rare, inherited or de novo mutations. These as well as non-genetic factors (such as perinatal events and immunological factors) are likely to contribute to the heterogeneity of the clinical phenotype, the structural and functional brain anomalies and the neural circuitry involvement. Management usually includes psychoeducation and reassurance, behavioural methods, pharmacotherapy and, rarely, functional neurosurgery. Future research that integrates clinical and neurobiological data, including neuroimaging and genetics, is expected to reveal the pathogenesis of GTS at the neural circuit level, which may lead to targeted interventions.

Rats overexpressing the dopamine transporter display behavioral and neurobiological abnormalities with relevance to repetitive disorders

The dopamine transporter (DAT) plays a pivotal role in maintaining optimal dopamine signaling. DAT-overactivity has been linked to various neuropsychiatric disorders yet so far the direct pathological consequences of it has not been fully assessed. We here generated a transgenic rat model that via pronuclear microinjection overexpresses the DAT gene. Our results demonstrate that DAT-overexpression induces multiple neurobiological effects that exceeded the expected alterations in the corticostriatal dopamine system. Furthermore, transgenic rats specifically exhibited behavioral and pharmaco-therapeutic profiles phenotypic of repetitive disorders. Together our findings suggest that the DAT rat model will constitute a valuable tool for further investigations into the pathological influence of DAT overexpression on neural systems relevant to neuropsychiatric disorders.

Investigation of SNP rs2060546 Immediately Upstream to NTN4 in a Danish Gilles de la Tourette Syndrome Cohort

Gilles de la Tourette syndrome (GTS) is a neuropsychiatric disorder characterized by multiple motor and vocal tics. GTS is a complex disorder, with environmental factors and several genes involved. Although variations within a few genes such as AADAC, NRXN1, SLITRK1, HDC, and IMMP2L have been tentatively associated with GTS (in a small number of patients), the causative genes underlying GTS pathophysiology remain unknown. In a previous genome-wide association study (GWAS) a single nucleotide polymorphism (SNP, rs2060546) near the Netrin-4 (NTN4 - MIM 610401) gene was shown to be associated with GTS [odds ratio (OR) = 1.7; p-value = 5.8 × 10-7] thus warranting further investigations. As NTN4 is one of the axon guidance molecules expressed in the central nervous system and it interacts with the encoded proteins of SLIT and WNT genes guiding the growth cone toward its target, it is an attractive candidate susceptibility gene for GTS. In this study we attempted to replicate the association of rs2060546 with GTS by genotyping a Danish cohort of 240 GTS patients and 1006 healthy controls. Our results did not reveal an association (OR = 1.363; p-value = 0.3329) in the Danish cohort alone, which may be due to the small sample size. However, a meta-analysis including the present cohort and a total of 1316 GTS patients and 5023 controls from the GTS GWAS Replication Initiative (GGRI) and the first GTS-GWAS yielded a significant signal (OR = 3.74; p-value = 0.00018) and same direction of effect in the three cohorts. Thus, our study strengthens the evidence of the possible involvement of NTN4 in GTS etiology, suggesting that further studies in even larger samples and functional studies are warranted to investigate the role of this region in GTS pathogenesis.

TS-EUROTRAIN: A European-Wide Investigation and Training Network on the Etiology and Pathophysiology of Gilles de la Tourette Syndrome

Gilles de la Tourette Syndrome (GTS) is characterized by the presence of multiple motor and phonic tics with a fluctuating course of intensity, frequency, and severity. Up to 90% of patients with GTS present with comorbid conditions, most commonly attention-deficit/hyperactivity disorder (ADHD), and obsessive-compulsive disorder (OCD), thus providing an excellent model for the exploration of shared etiology across disorders. TS-EUROTRAIN (FP7-PEOPLE-2012-ITN, Grant Agr.No. 316978) is a Marie Curie Initial Training Network (http://ts-eurotrain.eu) that aims to elucidate the complex etiology of the onset and clinical course of GTS, investigate the neurobiological underpinnings of GTS and related disorders, translate research findings into clinical applications, and establish a pan-European infrastructure for the study of GTS. This includes the challenges of (i) assembling a large genetic database for the evaluation of the genetic architecture with high statistical power; (ii) exploring the role of gene-environment interactions including the effects of epigenetic phenomena; (iii) employing endophenotype-based approaches to understand the shared etiology between GTS, OCD, and ADHD; (iv) establishing a developmental animal model for GTS; (v) gaining new insights into the neurobiological mechanisms of GTS via cross-sectional and longitudinal neuroimaging studies; and (vi) partaking in outreach activities including the dissemination of scientific knowledge about GTS to the public. Fifteen partners from academia and industry and 12 PhD candidates pursue the project. Here, we aim to share the design of an interdisciplinary project, showcasing the potential of large-scale collaborative efforts in the field of GTS. Our ultimate aims are to elucidate the complex etiology and neurobiological underpinnings of GTS, translate research findings into clinical applications, and establish Pan-European infrastructure for the study of GTS and associated disorders.

The Genetic Etiology of Tourette Syndrome: Large-Scale Collaborative Efforts on the Precipice of Discovery

Gilles de la Tourette Syndrome (TS) is a childhood-onset neurodevelopmental disorder that is characterized by multiple motor and phonic tics. It has a complex etiology with multiple genes likely interacting with environmental factors to lead to the onset of symptoms. The genetic basis of the disorder remains elusive. However, multiple resources and large-scale projects are coming together, launching a new era in the field and bringing us on the verge of discovery. The large-scale efforts outlined in this report are complementary and represent a range of different approaches to the study of disorders with complex inheritance. The Tourette Syndrome Association International Consortium for Genetics (TSAICG) has focused on large families, parent-proband trios and cases for large case-control designs such as genomewide association studies (GWAS), copy number variation (CNV) scans, and exome/genome sequencing. TIC Genetics targets rare, large effect size mutations in simplex trios, and multigenerational families. The European Multicentre Tics in Children Study (EMTICS) seeks to elucidate gene-environment interactions including the involvement of infection and immune mechanisms in TS etiology. Finally, TS-EUROTRAIN, a Marie Curie Initial Training Network, aims to act as a platform to unify large-scale projects in the field and to educate the next generation of experts. Importantly, these complementary large-scale efforts are joining forces to uncover the full range of genetic variation and environmental risk factors for TS, holding great promise for identifying definitive TS susceptibility genes and shedding light into the complex pathophysiology of this disorder.

From Genetics to Epigenetics: New Perspectives in Tourette Syndrome Research

Gilles de la Tourette Syndrome (TS) is a neurodevelopmental disorder marked by the appearance of multiple involuntary motor and vocal tics. TS presents high comorbidity rates with other disorders such as attention deficit hyperactivity disorder (ADHD) and obsessive compulsive disorder (OCD). TS is highly heritable and has a complex polygenic background. However, environmental factors also play a role in the manifestation of symptoms. Different epigenetic mechanisms may represent the link between these two causalities. Epigenetic regulation has been shown to have an impact in the development of many neuropsychiatric disorders, however very little is known about its effects on Tourette Syndrome. This review provides a summary of the recent findings in genetic background of TS, followed by an overview on different epigenetic mechanisms, such as DNA methylation, histone modifications, and non-coding RNAs in the regulation of gene expression. Epigenetic studies in other neurological and psychiatric disorders are discussed along with the TS-related epigenetic findings available in the literature to date. Moreover, we are proposing that some general epigenetic mechanisms seen in other neuropsychiatric disorders may also play a role in the pathogenesis of TS.

Functional Evaluations of Genes Disrupted in Patients with Tourette's Disorder

Tourette's disorder (TD) is a highly heritable neurodevelopmental disorder with complex genetic architecture and unclear neuropathology. Disruptions of particular genes have been identified in subsets of TD patients. However, none of the findings have been replicated, probably due to the complex and heterogeneous genetic architecture of TD that involves both common and rare variants. To understand the etiology of TD, functional analyses are required to characterize the molecular and cellular consequences caused by mutations in candidate genes. Such molecular and cellular alterations may converge into common biological pathways underlying the heterogeneous genetic etiology of TD patients. Herein, we review specific genes implicated in TD etiology, discuss the functions of these genes in the mammalian central nervous system and the corresponding behavioral anomalies exhibited in animal models, and importantly, review functional analyses that can be performed to evaluate the role(s) that the genetic disruptions might play in TD. Specifically, the functional assays include novel cell culture systems, genome editing techniques, bioinformatics approaches, transcriptomic analyses, and genetically modified animal models applied or developed to study genes associated with TD or with other neurodevelopmental and neuropsychiatric disorders. By describing methods used to study diseases with genetic architecture similar to TD, we hope to develop a systematic framework for investigating the etiology of TD and related disorders.

The role of GRIN2B in Tourette syndrome: Results from a transmission disequilibrium study

BACKGROUND

Previous studies have indicated that dopamine interacts with glutamatergic projection neurons and that N-methyl-d-aspartate (NMDA) receptors might be involved in the pathogenesis of Tourette syndrome (TS). In this study, we examined whether two functional polymorphisms (rs1805476 and rs1805502) in the 3'UTR of the NMDA receptor 2B subunit gene (GRIN2B) were associated with TS in Chinese Han trios.

METHODS

DNA samples collected from 261 TS nuclear families were genotyped by PCR and direct sequencing technology. Haplotype relative risk (HRR), transmission disequilibrium test (TDT) and Haplotype-based haplotype relative risk (HHRR) analyses were performed on the genotype data.

RESULTS

We found an over-transmission of the A allele in rs1805476 and the T allele in rs1805502 from parents to their affected children, using the HRR (rs1805476: HRR=0.696, χ(2)=4.161, P=0.041, 95% CI: 0.491-0.986; rs1805502: HRR=0.697, χ(2)=3.954, P=0.047, 95% CI: 0.488-0.995). There was also strong evidence for a linkage between polymorphisms and TS using the TDT (rs1805476: TDT=5.447, df=1, P=0.024; rs1805502: TDT=5.233, df=1, P=0.027).

LIMITATIONS

The sample is small and the current population is just limited to the Chinese Han population.

CONCLUSIONS

These data support the hypothesis that GRIN2B might play a major role in the pathogenesis of TS in Chinese Han trios. However, these results need to be replicated using larger datasets collected from different populations.

Epigenome-Wide Association Study of Tic Disorders

Tic disorders are moderately heritable common psychiatric disorders that can be highly troubling, both in childhood and in adulthood. In this study, we report results obtained in the first epigenome-wide association study (EWAS) of tic disorders. The subjects are participants in surveys at the Netherlands Twin Register (NTR) and the NTR biobank project. Tic disorders were measured with a self-report version of the Yale Global Tic Severity Scale Abbreviated version (YGTSS-ABBR), included in the 8th wave NTR data collection (2008). DNA methylation data consisted of 411,169 autosomal methylation sites assessed by the Illumina Infinium HumanMethylation450 BeadChip Kit (HM450k array). Phenotype and DNA methylation data were available in 1,678 subjects (mean age = 41.5). No probes reached genome-wide significance (p < 1.2 × 10(-7)). The strongest associated probe was cg15583738, located in an intergenic region on chromosome 8 (p = 1.98 × 10(-6)). Several of the top ranking probes (p < 1 × 10(-4)) were in or nearby genes previously associated with neurological disorders (e.g., GABBRI, BLM, and ADAM10), warranting their further investigation in relation to tic disorders. The top significantly enriched gene ontology (GO) terms among higher ranking methylation sites included anatomical structure morphogenesis (GO:0009653, p = 4.6 × 10-(15)) developmental process (GO:0032502, p = 2.96 × 10(-12)), and cellular developmental process (GO:0048869, p = 1.96 × 10(-12)). Overall, these results provide a first insight into the epigenetic mechanisms of tic disorders. This first study assesses the role of DNA methylation in tic disorders, and it lays the foundations for future work aiming to unravel the biological mechanisms underlying the architecture of this disorder.

Association between Tourette syndrome and the dopamine D3 receptor gene rs6280

BACKGROUND

Tourette syndrome (TS) is a complex, heterozygous genetic disorder. The number of molecular genetic studies have investigated several candidate genes, particularly those implicated in the dopamine system. The dopamine D3 receptor (DRD3) gene has been considered as a candidate gene in TS. There was not any report about the association study of TS and DRD3 gene in Han Chinese population. We combined a case-control genetic association analysis and nuclear pedigrees transmission disequilibrium test (TDT) analysis to investigate the association between DRD3 gene rs6280 single nucleotide polymorphisms (SNPs) and TS in a Han Chinese population.

METHODS

A total of 160 TS patients was diagnosed by the diagnostic criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. The DRD3 gene rs6280 SNPs were genotyped by TaqMan SNP genotyping assay technique in all subjects. We used a case-control genetic association analysis to compare the difference in genotype and allele frequencies between 160 TS patients and 90 healthy controls. At the same time, we used TDT analysis to identify the DRD3 gene rs6280 transmission disequilibrium among 101 nuclear pedigrees.

RESULTS

The genotype and allele frequency of DRD3 gene rs6280 SNPs had no statistical difference between control group (90) and TS group (160) (χ2 = 3.647, P = 0.161; χ2 = 0.643, P = 0.423) using Chi-squared test. At the basis of the 101 nuclear pedigrees, TDT analysis showed no transmission disequilibrium of DRD3 gene rs6280 SNPs (χ2 = 0; P = 1).

CONCLUSIONS

Our findings provide no evidence for an association between DRD3 gene rs6280 and TS in the Han Chinese population.

Association of ADORA1 rs2228079 and ADORA2A rs5751876 Polymorphisms with Gilles de la Tourette Syndrome in the Polish Population

BACKGROUND

Gilles de la Tourette syndrome (GTS) is a neurodevelopmental disorder characterized by motor and vocal tics. Hyperactivity of dopaminergic transmission is considered a prime abnormality in the pathophysiology of tics. There are reciprocal antagonistic interactions between adenosine and dopamine transmission. The aim of the study was to analyze the association of two polymorphisms, rs2228079 in ADORA1 and rs5751876 in ADORA2A, with the risk of GTS and co-morbid disorders.

MATERIAL AND METHODS

A total of 162 Polish GTS patients and 270 healthy persons were enrolled in the study. Two polymorphisms were selected on the basis of knowledge of SNPs frequencies in ADORA1 and ADORA2A. Chi-square test was used for allelic and genotypic association studies. Association of genotypes with age of tic onset was analyzed with Mann-Whitney test. Multivariate logistic regression was used to find independent predictors of GTS risk.

RESULTS

We found that the risk of GTS was associated with rs2228079 and rs5751876 polymorphisms. The GG+GT genotypes of rs2228079 in ADORA1 were underrepresented in GTS patients (p = 0.011), whereas T allele of rs5751876 in ADORA2A was overrepresented (p = 0.017). The GG genotype of rs2228079 was associated with earlier age of tic onset (p = 0.046). We found also that the minor allele G of rs2228079 was more frequent in GTS patients with depression as compared to the patients without depression (p = 0.015). Also the genotype GG was significantly more frequent in patients with obsessive compulsive disorder/behavior (OCD/OCB, p = 0.021) and depression (p = 0.032), as compared to the patients without these co-morbidities. The minor allele T frequency of rs5751876 was lower in GTS patients with co-morbid attention deficit hyperactivity disorder (p = 0.022), and TT+TC genotypes were less frequent in the non-OCD anxiety disorder group (p = 0.045).

CONCLUSION

ADORA1 and ADORA2A variants are associated with the risk of GTS, co-morbid disorders, and may affect the age of tic onset.

Association between DRD2/ANKK1 TaqIA Polymorphism and Susceptibility with Tourette Syndrome: A Meta-Analysis

Background

Genetic factors are important in the pathogenesis of Tourette syndrome (TS). Notably, Dopamine receptor D2 (DRD2) gene has been suggested as a possible candidate gene for this disorder. Several studies have demonstrated that DRD2/ANKK1 TaqIA polymorphism is associated with an increased risk of developing TS. However, past results remain conflicting. We addressed this controversy by performing a meta-analysis of the relationship between DRD2/ANKK1 TaqIA polymorphism and TS.

Methods

Literature was searched in multiple databases including PUBMED, COCHRANE and WEB OF SCIENCE up to July 2014. The number of the genotypes for DRD2/ANKK1 TaqIA in the TS and control subjects was extracted and statistical analysis was performed using Review Manager 5.0.16 and Stata 12.0 software. Summary odds ratios (ORs) and 95% confidence intervals (95%CIs) were utilized to calculate the risk of TS with DRD2/ANKK1 TaqIA. Stratified analysis based on ethnicity was also conducted.

Results

523 patients with TS, 564 controls and 87 probands plus 152 relatives from five published studies were finally involved in this meta-analysis. Combined analysis revealed that the overall ORs for the DRD2/ANKK1 TaqIA A1 allele were 1.69 (95%CIs = 1.42-2.00) in the fixed-effect model and 1.66 (95%CIs = 1.33-2.08) in the random-effects model. Stratification by ethnicity indicated the TaqIA A1 allele was significantly associated with TS in Caucasians (fixed-effect model: OR=1.75, 95%CI = 1.43-2.16; random-effect model: OR=1.69, 95%CI = 1.25-2.28) and in Asians (OR=1.54, 95%CI = 1.12-2.10). Meta-analysis of the A1A1 vs. A2A2 (homozygous model), A1A2 vs. A2A2 (heterozygous model) and A1A1+A1A2 vs. A2A2 (dominant model) of this polymorphism revealed a significant association with TS in overall populations and Caucasians.

Conclusions

This meta-analysis suggested that the DRD2/ANKK1 TaqIA polymorphism might contribute to TS susceptibility, especially in Caucasian population. However, further investigation with a larger number of worldwide studies should be conducted to verify the association.