Tourette Syndrome Association International Consortium for Genetics. Genome scan for Tourette disorder in affected-sibling-pair and multigenerational families

Advances in understanding and treatment of Tourette syndrome

Tourette syndrome is a hereditary, childhood-onset neurodevelopmental disorder that was first clearly described in France in 1885. This disorder is characterized by sudden, rapid, recurrent, nonrhythmic movements (motor tics) or sounds (vocal or phonic tics), often preceded by premonitory sensations or urges. Some individuals also have psychiatric comorbidities, notably attention-deficit hyperactivity disorder or obsessive-compulsive disorder. Tourette syndrome occurs worldwide, in all races and ethnicities, in both sexes and in children as well as in adults. Estimates of its prevalence in children vary, with rates of up to 1% being reported, but rates of 0.3-0.8% are thought to accurately reflect the occurrence of the disorder. Research has led to progress in many aspects of Tourette syndrome, although many questions and unmet needs remain. For example, except for rare cases, the genetic basis remains elusive. The anatomical and neuronal changes in the brain that underlie Tourette syndrome are also unclear, although the evidence increasingly implicates alterations in basal ganglia function. Treatment is often unnecessary for individuals with mild tics, but for those with moderate to severe forms of the syndrome, some drugs are available, albeit frequently ineffective. Behavioral and surgical therapies, in particular deep brain stimulation, are currently undergoing development and show promising results. This Review examines the history of Tourette syndrome and describes its clinical presentation. The article also provides an overview of the epidemiology and pathophysiology of this disorder. Current treatment strategies and potential future therapies are also discussed.

Neurobiology of tourette syndrome: current status and need for further investigation

Tourette syndrome (TS) is a common, chronic neuropsychiatric disorder characterized by the presence of fluctuating motor and phonic tics. The typical age of onset is ∼5-7 years, and the majority of children improve by their late teens or early adulthood. Affected individuals are at increased risk for the development of various comorbid conditions, such as obsessive-compulsive disorder, attention deficit hyperactivity disorder, school problems, depression, and anxiety. There is no cure for tics, and symptomatic therapy includes behavioral and pharmacological approaches. Evidence supports TS being an inherited disorder; however, the precise genetic abnormality remains unknown. Pathologic involvement of cortico-striatal-thalamo-cortical (CSTC) pathways is supported by neurophysiological, brain imaging, and postmortem studies, but results are often confounded by small numbers, age differences, severity of symptoms, comorbidity, use of pharmacotherapy, and other factors. The primary site of abnormality remains controversial. Although numerous neurotransmitters participate in the transmission of messages through CSTC circuits, a dopaminergic dysfunction is considered a leading candidate. Several animal models have been used to study behaviors similar to tics as well as to pursue potential pathophysiological deficits. TS is a complex disorder with features overlapping a variety of scientific fields. Despite description of this syndrome in the late 19th century, there remain numerous unanswered neurobiological questions.

Thimerosal exposure in early life and neuropsychological outcomes 7-10 years later

OBJECTIVE

The authors used a public use data set to investigate associations between the receipt of thimerosal-containing vaccines and immune globulins early in life and neuropsychological outcomes assessed at 7-10 years.

METHODS

The data were originally created by evaluating 1,047 children ages 7-10 years and their biological mothers. This study developed seven latent neuropsychological factors and regressed them on a comprehensive set of covariates and thimerosal exposure variables.

RESULTS

The authors found no statistically significant associations between thimerosal exposure from vaccines early in life and six of the seven latent constructs. There was a small, but statistically significant association between early thimerosal exposure and the presence of tics in boys.

CONCLUSIONS

This finding should be interpreted with caution due to limitations in the measurement of tics and the limited biological plausibility regarding a causal relationship.

Tourette syndrome and other tic disorders

Tic disorders, including Tourette syndrome, are an intriguing group of paroxysmal movement abnormalities that begin in childhood, have a fluctuating course, are capable of causing psychosocial and physical problems, and often improve by early adulthood. These disorders are frequently associated with a variety of comorbid problems whose negative effects may exceed those of tics. Therapy is strictly symptomatic and usually includes educational, behavioral, and a variety of pharmacological therapies. Although there is strong evidence supporting an inherited basis, the precise genetic abnormality remains unknown. A proposed poststreptococcal autoimmune etiology remains controversial. Pathophysiologically, tics appear to arise from an alteration within cortico-striatal-thalamo-cortical circuits, but the definitive site is unknown. Evidence supports an abnormality of synaptic neurotransmission, likely involving the dopaminergic system.

Exome sequencing of a pedigree with Tourette syndrome or chronic tic disorder

Ten members of a 3-generation pedigree with 7 showing Tourette syndrome/chronic tic phenotype (TS-CTD) were evaluated with whole exome sequencing. We identified 3 novel, nonsynonymous single nucleotide variants in the MRPL3, DNAJC13, and OFCC1 genes that segregated with chronic tic phenotype. These variants were not present in 100 control subjects or in dbSNP/1000 Genomes databases. A novel variant in the 5' untranslated region of the OFCC1 gene was found in 2 TS-CTD patients from a different pedigree. Further studies will clarify the importance of variants in MRPL3, DNAJC13, and OFCC1 genes in TS.

Translocation breakpoint at 7q31 associated with tics: further evidence for IMMP2L as a candidate gene for Tourette syndrome

Gilles de la Tourette syndrome is a complex neuropsychiatric disorder with a strong genetic basis. We identified a male patient with Tourette syndrome-like tics and an apparently balanced de novo translocation [46,XY,t(2;7)(p24.2;q31)]. Further analysis using array comparative genomic hybridisation (CGH) revealed a cryptic deletion at 7q31.1-7q31.2. Breakpoints disrupting this region have been reported in one isolated and one familial case of Tourette syndrome. In our case, IMMP2L, a gene coding for a human homologue of the yeast inner mitochondrial membrane peptidase subunit 2, was disrupted by the breakpoint on 7q31.1, with deletion of exons 1-3 of the gene. The IMMP2L gene has previously been proposed as a candidate gene for Tourette syndrome, and our case provides further evidence of its possible role in the pathogenesis. The deleted region (7q31.1-7q31.2) of 7.2 Mb of genomic DNA also encompasses numerous genes, including FOXP2, associated with verbal dyspraxia, and the CFTR gene.

The genetics of Tourette disorder

Tourette disorder (TD) is a childhood onset neuropsychiatric syndrome defined by persistent motor and vocal tics. Despite a long-standing consensus for a strong genetic contribution, the pace of discovery compared to other disorders of similar prevalence has been slow, due in part to a paucity of studies and both clinical heterogeneity and a complex genetic architecture. However, the potential for rapid progress is high. Recent rare variant findings have pointed to the importance of copy number variation, the overlap of risks among distinct diagnostic entities, the contribution of novel molecular mechanisms, and the value of family based studies. Finally, analysis of a cohort of sufficient size to identify common polymorphisms of plausible effect is underway, promising key information regarding the contribution of common alleles to TD.

Familiality of Tourette syndrome, obsessive-compulsive disorder, and attention-deficit/hyperactivity disorder: heritability analysis in a large sib-pair sample

OBJECTIVE

Tourette syndrome (TS) is a neuropsychiatric disorder with a genetic component that is highly comorbid with obsessive-compulsive disorder (OCD) and attention deficit/hyperactivity disorder (ADHD). However, the genetic relations between these disorders have not been clearly elucidated. This study examined the familial relations among TS, OCD, and ADHD in a large sample of TS families.

METHOD

Parent-offspring concordance of TS, OCD, and ADHD was examined in 952 individuals from 222 TS-affected sib-pair families originally collected for genetic studies using logistic regression with generalized estimating equations to control for correlated data. Variance components methods were used to estimate the heritability and genetic and environmental correlations among TS, OCD, and ADHD. Bilineal families where both parents had TS or OCD were excluded.

RESULTS

OCD and ADHD were highly heritable in these TS families. There were significant genetic correlations between TS and OCD and between OCD and ADHD, but not between TS and ADHD. In addition, significant environmental correlations were found between TS and ADHD and between OCD and ADHD. Parental OCD + ADHD was associated with offspring OCD + ADHD.

CONCLUSIONS

This study provides further evidence for a genetic relation between TS and OCD and suggests that the observed relation between TS and ADHD may due in part be to a genetic association between OCD and ADHD and in part due to shared environmental factors.

The genetics of child psychiatric disorders: focus on autism and Tourette syndrome

Investigations into the genetics of child psychiatric disorders have finally begun to shed light on molecular and cellular mechanisms of psychopathology. The first strains of success in this notoriously difficult area of inquiry are the result of an increasingly sophisticated appreciation of the allelic architecture of common neuropsychiatric and neurodevelopmental disorders, the consolidation of large patient cohorts now beginning to reach sufficient size to power reliable studies, the emergence of genomic tools enabling comprehensive investigations of rare as well as common genetic variation, and advances in developmental neuroscience that are fueling the rapid translation of genetic findings.

Behavioral interventions for tic disorders

A variety of treatment approaches have been used to manage tic symptoms in Tourette syndrome and other tic disorders. Pharmacological interventions remain the most common approach, but in the past 3 decades, various nonpharmacological treatment options have emerged including: (1) massed practice, (2) relaxation training, (3) self-monitoring, (4) function-based/contingency management procedures, (5) habit reversal training, (6) exposure and response prevention, and (7) cognitive behavior therapy. Each of these procedures is described along with the evidence reflecting its efficacy and usefulness. A synthesis of the findings and implications is provided, including directions and recommendations for future treatment and research.

An update on Tourette syndrome

Recent advances in our understanding of the phenomenology, etiology, pathophysiology, and treatment of Tourette syndrome are discussed. Tourette syndrome appears to involve dysfunction of limbic and somatosensory "traffic" through the basal ganglia, within corticostriatal-thalamocortical circuits. Dynamic alterations in the balance of these inputs may dictate the manifestations (sensory, motor, affective, and behavioral) of the disorder at any given time. Individualized assessment and treatment are the keys to optimal treatment of this condition.

The genetics of obsessive-compulsive disorder and Tourette syndrome: an epidemiological and pathway-based approach for gene discovery

OBJECTIVE

To provide a contemporary perspective on genetic discovery methods applied to obsessive-compulsive disorder (OCD) and Tourette syndrome (TS).

METHOD

A review of research trends in genetics research in OCD and TS is conducted, with emphasis on novel approaches.

RESULTS

Genome-wide association studies (GWAS) are now in progress in OCD and TS and will provide a platform for future discovery of common gene variants. Optimally, newer next-generation genome sequencing methods can also be used to detect larger effect genes (rare gene variants), taking advantage of pedigrees. Studies of gene networks or sets rather than individual genes will be required to elucidate biological etiology, as neural systems appear to act redundantly. Newer phenotyping strategies, such as symptom-based subtypes, cross-disorder latent class types, and intermediate phenotypes (endophenotypes) will need to be developed and tested to better align clinical and physiological measures with genetic architecture.

CONCLUSION

Although genetics research has made significant advances based on computational strength and bioinformatics advances, newer approaches to phenotyping and judicious study of gene etiological networks will be needed to uncover the genetic etiology of OCD and TS.

An Association Test for Multiple Traits Based on the Generalized Kendall's Tau

In many genetics studies, especially in the investigation of mental illness and behavioral disorders, it is common for researchers to collect multiple phenotypes to characterize the complex disease of interest. It may be advantageous to analyze those phenotypic measurements simultaneously if they share a similar genetic mechanism. In this study, we present a nonparametric approach to studying multiple traits together rather than examining each trait separately. Through simulation we compared the nominal type I error and power of our proposed test to an existing test, i.e., a generalized family-based association test. The empirical results suggest that our proposed approach is superior to the existing test in the analysis of ordinal traits. The advantage is demonstrated on a data set concerning alcohol dependence. In this application, the use of our methods enhanced the signal of the association test.

Tic disorders: some key issues for DSM-V

This study provides a focused review of issues that are relevant to the nosology of the tic disorders and presents preliminary recommendations to be considered for DSM-V. The recommended changes are designed to clarify and simplify the diagnostic criteria, reduce the use of the residual category, tic disorder not otherwise specified, and are not intended to alter substantially clinical practice or the continuity of past and future research. Specific recommendations include: (1) a more precise definition of motor and vocal tics; (2) simplification of the duration criterion for the tic disorders; (3) revising the term "transient tic disorder" for those with tic symptoms of less than 12-month duration; (4) establishing new tic disorder categories for those with substance induced tic disorder and tic disorder due to a general medical condition; and (5) including a motor tic only and vocal tic only specifier for the chronic motor or vocal tic disorder category.

Tourette disorder spectrum maps to chromosome 14q31.1 in an Italian kindred

Tourette syndrome (TS) is a frequent neuropsychiatric disorder of unknown etiology. A number of chromosomal regions have been nominated as TS loci in linkage studies, but confirmation has met with limited success and causative mutations have not yet been definitely identified. Furthermore, TS, chronic tics, and obsessive–compulsive disorder (OCD) occur at increased frequencies among TS relatives, supporting the view that these phenotypes represent parts of the same genetically determined spectrum. We ascertained a four-generation Italian kindred segregating TS, chronic multiple motor tics (CMT), and OCD, and we performed a ten-centimorgan (cM) genome-wide linkage scan in order to map the underlying genetic defect. Suggestive linkage to chromosome 14q31.1 (multipoint LOD = 2.4) was detected by affected-only analysis under an autosomal dominant model and a narrower phenotype definition (only the subjects with TS and CMT were considered as affected). The linkage peak increased and it approached genome-wide significance (LOD = 3.29) when a broader phenotype definition was adopted (subjects with TS, CMT, and OCD considered as affected). Haplotype analysis defined a ∼2.3 cM critical region, shared by all the relatives with TS, CMT, or OCD. In conclusion, we provide strong evidence for linkage of TS spectrum to chromosome 14q31.1. Suggestive linkage to an overlapping region of chromosome 14q was reported in a recent scan of TS sibling pairs. This region might therefore contain an important gene for TS, and it should be prioritized for further study.

Tourette syndrome is associated with recurrent exonic copy number variants

BACKGROUND

Multiple rare copy number variants (CNVs) including genomic deletions and duplications play a prominent role in neurodevelopmental disorders such as mental retardation, autism, and schizophrenia, but have not been systematically studied in Tourette syndrome (TS).

METHODS

We performed a genome-wide screening of single nucleotide polymorphism (SNP) genotyping microarray data to identify recurrent or de novo rare exonic CNVs in a case-control association study of patients with TS.

RESULTS

We identified 5 exon-affecting rare CNVs that are either de novo or recurrent in 10 out of 111 patients with TS but were not found in 73 ethnically matched controls or in the entries of the Database of Genomic Variants (containing 21,178 CNVs at 6,558 loci). Three out of the 5 CNVs have been implicated previously by other studies in schizophrenia, autism, and attention-deficit hyperactivity disorder, suggesting that these CNVs produce a continuum of neuropsychiatric disturbances that manifest in different ways depending on other genetic, environmental, or stochastic factors.

CONCLUSIONS

Rare, recurrent exonic copy number variants are associated in a subset of patients with Tourette syndrome.

Linkage analysis of Tourette syndrome in a large Utah pedigree

Tourette syndrome (TS) is a neuropsychiatric disorder characterized by multiple motor and phonic tics. The heritability of TS has been well established, yet there is a lack of consensus in genome-wide linkage studies. The purpose of this study was to conduct a genome-wide linkage analysis on a unique, large, high-risk TS Utah pedigree. We examined a qualitative trait (TS1) where cases had a definitive diagnosis of TS as observed by a clinical interviewer (n = 66) and a quantitative phenotype based on the total Yale global motor and phonic tic severity scores (n = 102). Both parametric and non-parametric multipoint linkage analyses based on MCMC methods were performed using a 10 cM spaced micro-satellite autosomal marker set. Two regions of interest were identified under affecteds-only recessive models; a LOD score of 3.3 on chromosome 1p for Yale tic severity and a LOD score of 3.1 on chromosome 3p for the TS1 phenotype. Twenty-seven individuals shared linked segregating haplotypes for the 1p region. They had significantly higher Yale tic phonic scores than non-sharers (P = 0.01). There were 46 haplotype sharers on chromosome 3p with significantly higher percentage of females among these individuals compared to the non-sharers (P = 0.03). The significant linkage peaks on chromosomes 1p and 3p are in new areas of the genome for TS, and replication of these findings is necessary.

Glutamatergic modulatory therapy for Tourette syndrome

Tourette syndrome (TS) is a neuropsychiatric disorder characterized by the presence of chronic, fluctuating motor and vocal (phonic) tics. The disorder is commonly associated with a variety of comorbidities including obsessive-compulsive disorder (OCD), attention deficit hyperactivity disorder (ADHD), school problems, anxiety, and depression. Therapeutically, if tics are causing psychosocial or physical problems, symptomatic medications are often prescribed, typically alpha-adrenergic agonists or dopamine antagonists. Recognizing that therapy is often ineffective and frequently associated with unacceptable side-effects, there is an ongoing effort to identify new tic-suppressing therapies. Several lines of evidence are presented that support the use of glutamate modulators in TS including glutamate's major role in cortico-striatal-thalamo-cortical circuits (CSTC), the recognized extensive interaction between glutamate and dopamine systems, results of familial genetic studies, and data from neurochemical analyses of postmortem brain samples. Since insufficient data is available to determine whether TS is definitively associated with a hyper- or hypo-glutamatergic state, potential treatment options using either glutamate antagonists or agonists are reviewed. Data from studies using these agents in the treatment of OCD are presented. If validated, modulation of the glutamate system could provide a valuable new pharmacological approach in the treatment of tics associated with Tourette syndrome.

The genetics of Tourette syndrome: a review

OBJECTIVES

This article summarizes and evaluates recent advances in the genetics of Gilles de la Tourette syndrome (GTS).

METHODS

This is a review of recent literature focusing on (1) the genetic etiology of GTS; (2) common genetic components of GTS, attention deficit hyperactivity disorder (ADHD), and obsessive compulsive disorder (OCD); (3) recent linkage studies of GTS; (4) chromosomal translocations in GTS; and (5) candidate gene studies.

RESULTS

Family, twin, and segregation studies provide strong evidence for the genetic nature of GTS. GTS is a heterogeneous disorder with complex inheritance patterns and phenotypic manifestations. Family studies of GTS and OCD indicate that an early-onset form of OCD is likely to share common genetic factors with GTS. While there apparently is an etiological relationship between GTS and ADHD, it appears that the common form of ADHD does not share genetic factors with GTS. The largest genome wide linkage study to date observed evidence for linkage on chromosome 2p23.2 (P=3.8x10(-5)). No causative candidate genes have been identified, and recent studies suggest that the newly identified candidate gene SLITRK1 is not a significant risk gene for the majority of individuals with GTS.

CONCLUSION

The genetics of GTS are complex and not well understood. The Genome Wide Association Study (GWAS) design can hopefully overcome the limitations of linkage and candidate gene studies. However, large-scale collaborations are needed to provide enough power to utilize the GWAS design for discovery of causative mutations. Knowledge of susceptibility mutations and biological pathways involved should eventually lead to new treatment paradigms for GTS.

SLITRK1 binds 14-3-3 and regulates neurite outgrowth in a phosphorylation-dependent manner

BACKGROUND

Rare genetic variants of SLITRK1 have been previously associated with Tourette syndrome (TS), attention-deficit/hyperactivity disorder (ADHD), and obsessive-compulsive disorder (OCD) symptoms.

METHODS

We studied SLITRK1 processing and phosphorylation. To explore potential signaling pathways of the cytoplasmic domain of SLITRK1, we made use of the yeast two-hybrid screen.

RESULTS

We observed that the extracellular domain of SLITRK1 is secreted in vitro and in vivo and that this process is activated by protein kinase C and inhibited by an inhibitor of tumor necrosis factor-alpha converting enzyme (TACE). We observed that SLITRK1 undergoes gamma-secretase cleavage to release a SLITRK1 intracellular domain (SICD). We identified an interaction between SLITRK1 and 14-3-3 proteins and observed that these proteins co-localized in cortical neuronal cultures and were coprecipitated from rat brain lysates, consistent with an interaction in vivo. We mapped the binding site to the very COOH-terminus of SLITRK1, as deletion of the last six amino acids of SLITRK1 abolished the interaction. We demonstrated phosphorylation of SLITRK1 by protein kinase A (PKA), protein kinase C (PKC), and casein kinase II (CK2) and observed that CK2 phosphorylates SLITRK1 in the 14-3-3 binding site. Mutating the CK2 phosphorylation site of SLITRK1 decreased binding to 14-3-3 and inhibited SLITRK1-mediated neurite outgrowth.

CONCLUSIONS

Our results shed light on the cell biology of SLITRK1, including its protein phosphorylation and potential molecular pathways for SLITRK1 function, and should contribute to further understanding the role of SLIRTK1 in developmental neuropsychiatric conditions such TS, OCD, and ADHD.

Striatal [11C]dihydrotetrabenazine and [11C]methylphenidate binding in Tourette syndrome

OBJECTIVE

Tourette syndrome (TS) is a common neurodevelopmental disorder marked by tics and behavioral comorbidities. Clinical pharmacology suggests that dopaminergic signaling abnormalities are part of the pathophysiology of TS. Prior molecular imaging studies of nigrostriatal dopaminergic terminal markers report conflicting results. Our goal was to characterize the distribution of nigrostriatal dopaminergic terminals in subjects with TS.

METHODS

Thirty-three adult subjects with TS were studied with PET using [11C]dihydrotetrabenazine (DTBZ), a ligand for the type 2 vesicular monoamine transporter, and with [11C] methylphenidate (MP), a ligand for the plasmalemmal dopamine transporter. Subjects were characterized with standard rating instruments for tic severity, obsessive-compulsive behaviors, and attentional deficits.

RESULTS

We found no differences between subjects with TS and control subjects in DTBZ and MP binding in any striatal region. There was no correlation between binding measures and clinical variables. Ventral striatal DTBZ and MP binding distributions in subjects with TS were normal.

CONCLUSIONS

We found no evidence of increased striatal dopaminergic innervation in Tourette syndrome (TS). Discrepancy between our present results and those of other studies may be explained by heterogeneity of TS.

The genetics of obsessive-compulsive disorder and Tourette's syndrome: what are the common factors?

Genetic discovery in obsessive-compulsive disorder and Tourette's syndrome has made significant progress in the past decade. The two disorders are phenomenologically, epidemiologically, and probably pathophysiologically related; however, as with most neuropsychiatric disorders, gene discovery has been challenging. Genetic epidemiology studies support the existence of susceptibility genes in both disorders, and more extensive genome-wide studies are under way. Gene pathways involving neurotransmitter (serotonin, dopamine, glutamate) and neurodevelopment (synaptic, homeobox) domains have been examined, but more complex genetic mechanisms remain largely unexplored. This review addresses the current state of genetic research in obsessive-compulsive disorder and Tourette's syndrome, emphasizing commonalities between the disorders. Questions on common genetic substrates, the use of endophenotypes, and the utility of genetic data to inform pharmacologic treatment are also addressed.

What's wrong with Tourette syndrome?

Gilles de la Tourette Syndrome (Tourette Syndrome, TS) and related tic disorders have known fascinated researchers since their initial description around 1884 by the French marquis Georges Albert Edouard Brutus Gilles de la Tourette. Particularly the "cause" of the disorder has been a much sought-after prize, but unfortunately this goal has appeared remarkably elusive. Many clues have been pursued, both genetic and environmental factors, but no compelling major contribution to the pathogenesis of the disease has yet emerged. What's wrong with TS? Is it lack of data or lack of concepts? It should be noted that TS is not unique in this respect. Despite decades of intensive data gathering, many prevalent psychiatric disorders, such as schizophrenia, major depressive disorder or obsessive-compulsive disorder still face a more or less similar situation.

Chromosome 5 and Gilles de la Tourette syndrome: Linkage in a large pedigree and association study of six candidates in the region

Gilles de la Tourette Syndrome (TS) is a neuropsychiatric disorder characterized by both motor and vocal tics. In our previous genome scan for TS we identified evidence for linkage to the centromeric region of chromosome 5 in a single large family of 32 individuals with 10 family members with TS or chronic multiple tics (CMT). In this paper we report further analyses of the 5p-centromeric region in this pedigree. An additional 11 family members were identified and screened for TS. Using a set of 14 microsatellite markers we refined the linked region to a approximately 28 Mb interval between the markers D5S1506 and D5S76. A set of six candidate genes located in this region were selected to be tested for genetic association with TS. These genes were GDNF, ITGA1, ISL1, FGF10, HCN1 and SLC1A3. The TDT statistic was used for the association tests in a sample of 171 independent nuclear families with 241 affected children with TS. We found no evidence for an association between TS and markers in these genes in this sample of families. This study represents the first efforts to narrow the linkage region in the extended pedigree and the first tests of candidate genes in the chromosome 5 region linked to TS.

New Jersey Center for Tourette Syndrome sharing repository: methods and sample description

BACKGROUND

Tourette Syndrome is a neuropsychiatric disorder characterized by chronic motor and phonic tics. Affected individuals and their family members are at an increased risk for other neuropsychiatric conditions including obsessive-compulsive disorder and attention deficit hyperactivity disorder. While there is consistent evidence that genetic factors play a significant etiologic role, no replicable susceptibility alleles have thus far been identified.

DESCRIPTION

Here we discuss a sharing resource of clinical and genetic data, the New Jersey Center for Tourette Syndrome Sharing Repository, whose goal is to provide clinical data, DNA, and lymphoblastoid cell lines to qualified researchers.

CONCLUSION

Opening access to the data and patient material to the widest possible research community will hasten the identification of causal genetic factors and facilitate better understanding and treatment of this often impairing disorder.

Latent class analysis of gilles de la tourette syndrome using comorbidities: clinical and genetic implications

BACKGROUND

Although susceptibility loci exist for Gilles de la Tourette syndrome (GTS), no causative gene has been identified, perhaps in part because of phenotypic heterogeneity. This study used latent class analyses (LCA) to identify GTS subphenotypes and assess characteristics and heritability of the classes.

METHODS

The study included 952 individuals from 222 GTS families recruited for genetic studies. LCA identified a best-fit model for combinations of the diagnoses of GTS, obsessive-compulsive disorder (OCD), OC symptoms and behaviors (OCS/OCB), and attention-deficit/hyperactivity disorder (ADHD) in a random sample of one sibling from each family (n = 197), a replication sample randomly chosen from the remaining siblings (n = 203), and in the entire sample (all siblings and parents, N = 952). Heritabilities were assessed for all categoric diagnoses and LCA classes using a variance components approach.

RESULTS

In this large sample of GTS sib pairs and their parents, three GTS-affected groups were identified-GTS + OCS/OCB (Class III), GTS + OCD (Class IV), and GTS + OCD + ADHD (Class V)-in addition to a minimally affected class (I) and a small chronic tics + OCD class (II). A preponderance of males and younger age at onset was found in more comorbidly affected classes. Only the GTS + OCD + ADHD class was highly heritable.

CONCLUSIONS

Our data suggest that GTS classes may represent distinct entities, with both shared and unique etiologies. In particular, GTS + OCD + ADHD may represent a separate, heritable phenotype that can be used to further inform genetic studies.

Haplotype evolution of SLITRK1, a candidate gene for Gilles de la Tourette syndrome

Gilles de la Tourette syndrome (GTS) is a complex disorder with a clear genetic component but no clearly identified genes with variation of etiologic relevance. Various candidate regions and genes show some evidence of affecting risk, though clearly not all patients/families can be explained by any one of them. Resequencing one candidate gene, SLITRK1, has identified four new variants. Including them, we have typed over 2,300 normal individuals from 44 populations for 11 SNPs spanning the gene. The unusual global pattern seen is that one non-ancestral haplotype is the single most common haplotype worldwide. Other haplotypes appear to result from accumulation of mutations with no evidence of historical recombination. Although there is no evidence of selection, the haplotype frequency variation seen around the world will need to be considered in any future association studies of this locus with GTS or any other neuropsychiatric disorder.

Association study between Gilles de la Tourette Syndrome and two genes in the Robo-Slit pathway located in the chromosome 11q24 linked/associated region

Gilles de la Tourette Syndrome (GTS) is an inherited neuropsychiatric disorder characterized by the presence of motor and phonic tics. Previous genetic studies have identified linkage and association between GTS and the 11q24 chromosomal region. We selected for study, within this region, two possible susceptibility genes for GTS, the ROBO3 and ROBO4 genes. These two genes were selected because of the recent identification of SLITRK1 as a potential susceptibility gene for GTS based on a translocation breakpoint and the further finding of two mutations in the SLITRK1 gene in three patients with GTS. While thus far, the SLITRK1 gene appears to account for only a few cases of GTS, these findings, if confirmed, point to other genes in these pathways that may contribute to GTS. Based on this, we examined two genes in the Slit-Robo pathway involved in cell migration, axonal pathfinding, and/or neuronal differentiation because of their location in 11q24, a region previously identified as linked and associated with GTS. We selected six haplotype tagging single nucleotide polymorphisms (SNPs) for ROBO3 and four for ROBO4 and genotyped them in our sample of trios and sibpair families diagnosed with GTS. Based on 155 nuclear families with 255 affected children, we did not find evidence for association between GTS and either the ROBO3 or ROBO4 genes. Thus, these two genes are unlikely to be the susceptibility genes contributing to GTS on 11q24.

Evidence for a susceptibility locus on chromosome 10p15 in early-onset obsessive-compulsive disorder

BACKGROUND

The goal of this study was to identify chromosomal regions likely to contain susceptibility loci for obsessive-compulsive disorder (OCD).

METHODS

We conducted a genome-wide linkage scan, with average marker spacing less than 10 centimorgans (cM), in 121 subjects from 26 families ascertained through probands with early-onset OCD. Best estimate lifetime psychiatric diagnoses were based on semistructured interviews and all other available sources of information. Parametric and nonparametric linkage analyses were conducted with GENEHUNTER+ and Allegro. Family-based association analyses were done using 35 single nucleotide polymorphisms (SNPs) in the 10p15 region.

RESULTS

The maximum nonparametric log of odds (NLOD) score was 2.43 on chromosome 10p15 at position 4.37. When data from our first genome scan were added to data from this scan, the maximum NLOD score in the 10p15 region was 1.79. Association was detected on 10p15 with three adjacent SNPs, including the amino acid variant rs2271275 in the 3' region of adenosine deaminase acting on RNA 3 (ADAR3) (p < .05).

CONCLUSIONS

The results provide suggestive evidence for linkage on chromosome 10p15. Evidence for association in the linkage region was found with three markers in the 3' end of ADAR3. Limitations include the lack of significant linkage and association findings when corrected for multiple testing.