Human mutations in high-confidence Tourette disorder genes affect sensorimotor behavior, reward learning, and striatal dopamine in mice.

Tourette disorder (TD) is poorly understood, despite affecting 1/160 children. A lack of animal models possessing construct, face, and predictive validity hinders progress in the field. We used CRISPR/Cas9 genome editing to generate mice with mutations orthologous to human de novo variants in two high-confidence Tourette genes, CELSR3 and WWC1. Mice with human mutations in Celsr3 and Wwc1 exhibit cognitive and/or sensorimotor behavioral phenotypes consistent with TD. Sensorimotor gating deficits, as measured by acoustic prepulse inhibition, occur in both male and female Celsr3 TD models. Wwc1 mice show reduced prepulse inhibition only in females. Repetitive motor behaviors, common to Celsr3 mice and more pronounced in females, include vertical rearing and grooming. Sensorimotor gating deficits and rearing are attenuated by aripiprazole, a partial agonist at dopamine type II receptors. Unsupervised machine learning reveals numerous changes to spontaneous motor behavior and less predictable patterns of movement. Continuous fixed-ratio reinforcement shows that Celsr3 TD mice have enhanced motor responding and reward learning. Electrically evoked striatal dopamine release, tested in one model, is greater. Brain development is otherwise grossly normal without signs of striatal interneuron loss. Altogether, mice expressing human mutations in high-confidence TD genes exhibit face and predictive validity. Reduced prepulse inhibition and repetitive motor behaviors are core behavioral phenotypes and are responsive to aripiprazole. Enhanced reward learning and motor responding occur alongside greater evoked dopamine release. Phenotypes can also vary by sex and show stronger affection in females, an unexpected finding considering males are more frequently affected in TD.

Rate of manifesting carriers and other unexpected findings on carrier screening.

OBJECTIVES: To ascertain the rate of unexpected findings on carrier screening (CS) and assess whether implications are disclosed to patients. METHODS: We performed a retrospective observational study of subjects who had CS after pre-test counseling from a licensed genetic counselor at a large tertiary care center. We quantified the rate of unexpected finding on CS, defined as manifesting carriers (MCs), genotypes predicting phenotype, and chromosome abnormalities. We determined how often patients were informed of implications. We performed subgroup analyses by type of unexpected finding and calculated odds ratios (OR) and 95% confidence intervals (CI) for carrier testing methodology (genotype) and number of genes tested. RESULTS: A total of 4685 patients had CS over the selected time frame. Of those patients, 412 patients (8.8%) had one unexpected finding and 29 patients (0.6%) had two or more findings. In total, 466 unexpected findings were identified, including 437 MC conditions, 23 genotypes predicting phenotype, and 6 chromosome abnormalities. Patients were informed of the implications for MCs, genotypes predicting phenotype, and chromosome abnormalities in 27.6%, 91.3%, and 100% of cases, respectively. More unexpected findings were detected with sequencing compared to genotyping (OR 2.21 and 95% CI 1.76-2.76) and with ≥200 gene panels compared to <200 gene panels (OR 1.79 and 95% CI 1.47-2.17). CONCLUSION: This study highlights that nondisclosure of unexpected findings on CS is common and underscores the need for further research to improve post-test counseling and follow-up.

Polygenic and environmental determinants of tics in the Avon Longitudinal Study of Parents and Children.

Tourette syndrome (TS) is caused by multiple genetic and environmental factors. Yet, little is known about the interplay of these factors in the occurrence of tics. We investigated whether polygenic risk score (PRS) of TS and pregnancy-related factors together enhance the explained variance of tic occurrence in the Avon Longitudinal Study of Parents and Children (Ncases  = 612; Ncontrols  = 4,201; 50% male; mean age 13.8 years). We included a cumulative adverse pregnancy risk score, maternal anxiety and depression, and maternal smoking and alcohol use during pregnancy. We investigated possible joint effects of genetic and pregnancy-related risk factors using a multivariable approach, and explored mediation effects between the pregnancy-related risk factors in explaining tic presence. The PRS and the cumulative adverse pregnancy risk score, maternal anxiety, or maternal depression explained significantly more variance of tic presence compared to models including only the PRS. Furthermore, we found that the cumulative adverse pregnancy risk score mediated the association between several pregnancy-related factors (maternal anxiety, depression, and smoking) and tics. The combination of a PRS and pregnancy-related risk factors explained more variance of tics in a general population cohort compared to studying these factors in isolation.

Whole-exome sequencing identifies genes associated with Tourette's disorder in multiplex families.

Tourette's Disorder (TD) is a neurodevelopmental disorder (NDD) that affects about 0.7% of the population and is one of the most heritable NDDs. Nevertheless, because of its polygenic nature and genetic heterogeneity, the genetic etiology of TD is not well understood. In this study, we combined the segregation information in 13 TD multiplex families with high-throughput sequencing and genotyping to identify genes associated with TD. Using whole-exome sequencing and genotyping array data, we identified both small and large genetic variants within the individuals. We then combined multiple types of evidence to prioritize candidate genes for TD, including variant segregation pattern, variant function prediction, candidate gene expression, protein-protein interaction network, candidate genes from previous studies, etc. From the 13 families, 71 strong candidate genes were identified, including both known genes for NDDs and novel genes, such as HtrA Serine Peptidase 3 (HTRA3), Cadherin-Related Family Member 1 (CDHR1), and Zinc Finger DHHC-Type Palmitoyltransferase 17 (ZDHHC17). The candidate genes are enriched in several Gene Ontology categories, such as dynein complex and synaptic membrane. Candidate genes and pathways identified in this study provide biological insight into TD etiology and potential targets for future studies.

Clinical and EEG factors associated with antiseizure medication resistance in idiopathic generalized epilepsy.

OBJECTIVE: We sought to determine which combination of clinical and electroencephalography (EEG) characteristics differentiate between an antiseizure medication (ASM)-resistant vs ASM-responsive outcome for patients with idiopathic generalized epilepsy (IGE). METHODS: This was a case-control study of ASM-resistant cases and ASM-responsive controls with IGE treated at five epilepsy centers in the United States and Australia between 2002 and 2018. We recorded clinical characteristics and findings from the first available EEG study for each patient. We then compared characteristics of cases vs controls using multivariable logistic regression to develop a predictive model of ASM-resistant IGE. RESULTS: We identified 118 ASM-resistant cases and 114 ASM-responsive controls with IGE. First, we confirmed our recent finding that catamenial epilepsy is associated with ASM-resistant IGE (odds ratio [OR] 3.53, 95% confidence interval [CI] 1.32-10.41, for all study subjects) after covariate adjustment. Other independent factors seen with ASM resistance include certain seizure-type combinations (absence, myoclonic, and generalized tonic-clonic seizures [OR 7.06, 95% CI 2.55-20.96]; absence and generalized tonic-clonic seizures [OR 4.45, 95% CI 1.84-11.34]), as well as EEG markers of increased generalized spike-wave discharges (GSWs) in sleep (OR 3.43, 95% CI 1.12-11.36 for frequent and OR 7.21, 95% CI 1.50-54.07 for abundant discharges in sleep) and the presence of generalized polyspike trains (GPTs; OR 5.49, 95% CI 1.27-38.69). The discriminative ability of our final multivariable model, as measured by area under the receiver-operating characteristic curve, was 0.80. SIGNIFICANCE: Multiple clinical and EEG characteristics independently predict ASM resistance in IGE. To improve understanding of a patient's prognosis, clinicians could consider asking about specific seizure-type combinations and track whether they experience catamenial epilepsy. Obtaining prolonged EEG studies to record the burden of GSWs in sleep and assessing for the presence of GPTs may provide additional predictive value.

Genetic counseling certificate program: A program evaluation of undergraduate exposure to genetic counseling.

Undergraduate genetic counseling exposure can generate interest in a growing field, help students prepare to apply to graduate-level programs, and introduce underrepresented populations to the career. One form of exposure that currently exists is the Genetic Counseling Certificate Program (GCCP), which is offered to undergraduate students at Rutgers University. To determine the effectiveness, benefits, and limitations of the GCCP, a program evaluation was conducted. Former GCCP students were surveyed to assess how they perceived the program. Overall, most students thought the program successfully met its objectives and thought their participation in the GCCP was beneficial. Because it is viewed favorably by former students, implementing something similar to the GCCP may be an option for institutions looking to offer additional opportunities to their undergraduates. Not only could creating programs like the GCCP enhance undergraduates' knowledge of the genetic counseling profession, but it could also contribute toward diversification of the field.

Investigation of gene-environment interactions in relation to tic severity.

Tourette syndrome (TS) is a neuropsychiatric disorder with involvement of genetic and environmental factors. We investigated genetic loci previously implicated in Tourette syndrome and associated disorders in interaction with pre- and perinatal adversity in relation to tic severity using a case-only (N = 518) design. We assessed 98 single-nucleotide polymorphisms (SNPs) selected from (I) top SNPs from genome-wide association studies (GWASs) of TS; (II) top SNPs from GWASs of obsessive-compulsive disorder (OCD), attention-deficit/hyperactivity disorder (ADHD), and autism spectrum disorder (ASD); (III) SNPs previously implicated in candidate-gene studies of TS; (IV) SNPs previously implicated in OCD or ASD; and (V) tagging SNPs in neurotransmitter-related candidate genes. Linear regression models were used to examine the main effects of the SNPs on tic severity, and the interaction effect of these SNPs with a cumulative pre- and perinatal adversity score. Replication was sought for SNPs that met the threshold of significance (after correcting for multiple testing) in a replication sample (N = 678). One SNP (rs7123010), previously implicated in a TS meta-analysis, was significantly related to higher tic severity. We found a gene-environment interaction for rs6539267, another top TS GWAS SNP. These findings were not independently replicated. Our study highlights the future potential of TS GWAS top hits in gene-environment studies.

Reproductive male partner testing when the female is identified to be a genetic disease carrier.

OBJECTIVE: To quantify carrier testing uptake rates for male partners of women found to be a carrier(s) for autosomal recessive conditions and to understand reasons for declining testing (uptake rate). METHODS: A retrospective chart review of 513 female patients seen at Rutgers-Robert Wood Johnson Medical School found to be carriers through expanded carrier screening (ECS) panels. The aims of this study were to determine how often their male partner chose testing, reasons for declining and the type of methodology chosen for their screening. RESULTS: Male partner uptake rate was 77%. We identified that the most significant barrier to male partner testing is female patients not following up on their own carrier screening results, thus missing the opportunity for partner testing. When male partners were provided options for testing, the most reported reason for declining is the belief it would have no impact on pregnancy management (20%). A carrier couple rate of 8.3% was identified of partners tested. CONCLUSION: Despite a relatively high male testing uptake rate, a quarter of carrier females did not proceed with testing their partner. To ascertain fetal risk, results for both parents is necessary. Pretest counseling should stress need for potential male partner follow-up testing.

Mood disorders in familial epilepsy: A test of shared etiology.

OBJECTIVE: Mood disorders are the most common comorbid conditions in epilepsy, but the cause remains unclear. One possible explanation is a shared genetic susceptibility to epilepsy and mood disorders. We tested this hypothesis by evaluating lifetime prevalence of mood disorders in relatives with and without epilepsy in families containing multiple individuals with epilepsy, and comparing the findings with rates from a general population sample. METHODS: The Composite International Diagnostic Interview was administered to 192 individuals from 60 families, including 110 participants with epilepsy of unknown cause (50 focal epilepsy [FE], 42 generalized epilepsy [GE], 6 FE and GE, 12 unclassifiable) and 82 relatives without epilepsy (RWOE). Odds ratios (ORs) for lifetime prevalence of mood disorders in participants with versus without epilepsy were computed through logistic regression, using generalized estimation equations to account for familial clustering. Standardized prevalence ratios (SPRs) were used to compare prevalence in family members with general population rates. RESULTS: Compared with RWOE, ORs for mood disorders were significantly increased in participants with FE (OR = 2.4, 95% confidence interval [CI] = 1.1-5.2) but not in those with GE (OR = 1.0, 95% CI = 0.4-2.2). In addition, prevalence of mood disorders was increased in individuals with epilepsy who had ≥1 relative with FE. Compared with general population rates, mood disorders were significantly increased in individuals with FE but not in those with GE. Rates were also increased in RWOE, but not significantly so (SPR = 1.4, P = .14). SIGNIFICANCE: These findings are consistent with the hypothesis of shared genetic susceptibility to epilepsy and mood disorders, but suggest (1) the effect may be restricted to FE, and (2) the shared genetic effect on risk of mood disorders and epilepsy may be restricted to individuals with epilepsy, that is, to those in whom the genetic risk for epilepsy is "penetrant."

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.

An Analytic Solution to the Computation of Power and Sample Size for Genetic Association Studies under a Pleiotropic Mode of Inheritance.

Our motivation here is to calculate the power of 3 statistical tests used when there are genetic traits that operate under a pleiotropic mode of inheritance and when qualitative phenotypes are defined by use of thresholds for the multiple quantitative phenotypes. Specifically, we formulate a multivariate function that provides the probability that an individual has a vector of specific quantitative trait values conditional on having a risk locus genotype, and we apply thresholds to define qualitative phenotypes (affected, unaffected) and compute penetrances and conditional genotype frequencies based on the multivariate function. We extend the analytic power and minimum-sample-size-necessary (MSSN) formulas for 2 categorical data-based tests (genotype, linear trend test [LTT]) of genetic association to the pleiotropic model. We further compare the MSSN of the genotype test and the LTT with that of a multivariate ANOVA (Pillai). We approximate the MSSN for statistics by linear models using a factorial design and ANOVA. With ANOVA decomposition, we determine which factors most significantly change the power/MSSN for all statistics. Finally, we determine which test statistics have the smallest MSSN. In this work, MSSN calculations are for 2 traits (bivariate distributions) only (for illustrative purposes). We note that the calculations may be extended to address any number of traits. Our key findings are that the genotype test usually has lower MSSN requirements than the LTT. More inclusive thresholds (top/bottom 25% vs. top/bottom 10%) have higher sample size requirements. The Pillai test has a much larger MSSN than both the genotype test and the LTT, as a result of sample selection. With these formulas, researchers can specify how many subjects they must collect to localize genes for pleiotropic phenotypes.

Drug-resistant epilepsy in adults: Outcome trajectories after failure of two medications.

OBJECTIVE: To examine the seizure trajectories of adults with epilepsy developing drug-resistant epilepsy (DRE) and to identify the predictors of seizure trajectory outcome. METHODS: Adult patients failing two antiepileptic drugs (AEDs) due to inefficacy and starting their third AED at a tertiary epilepsy center were followed for seizure trajectory outcome during medical management. Seizure trajectories were categorized into one of four patterns: (1) course with constant seizures; (2) fluctuating course; (3) delayed attainment of seizure freedom (seizure freedom delayed for >12 months after start of the study, but patient stayed in seizure freedom); and (4) early attainment of seizure freedom (within 12 months of starting study). Multiple ordinal logistic regression models were used to estimate the association between trajectory categories and clinical factors. RESULTS: Four hundred three adult patients met the eligibility criteria. Of these, 212 (53%) never achieved a seizure-free period of a year or more. The trajectories of 63 patients (16%) had a complex fluctuating trajectory, 62 (15%) had delayed onset of seizure freedom, and 66 (16%) had an early seizure freedom. Independent predictors associated with more favorable outcome trajectories were epilepsy type and length of follow-up. Specifically, compared to patients with focal epilepsy of temporal lobe, patients with focal epilepsy of occipital lobe (OR 3.80, 95% confidence interval [CI] 1.00-14.51, p = 0.04), generalized genetic (OR 3.23, 95% CI 1.88-5.57, p < 0.0001), unclear epilepsy type (OR 3.82, 95% CI 1.53-9.52, p < 0.005), and both focal and generalized epilepsy(OR 11.73, 95% CI 1.69-81.34, p = 0.01) were significantly more likely to experience a better trajectory pattern. SIGNIFICANCE: Examination of patterns of seizure trajectory of patients with incident DRE showed that 31% were in continuous seizure freedom at the end of the observation period.

Partitioning the heritability of Tourette syndrome and obsessive compulsive disorder reveals differences in genetic architecture.

The direct estimation of heritability from genome-wide common variant data as implemented in the program Genome-wide Complex Trait Analysis (GCTA) has provided a means to quantify heritability attributable to all interrogated variants. We have quantified the variance in liability to disease explained by all SNPs for two phenotypically-related neurobehavioral disorders, obsessive-compulsive disorder (OCD) and Tourette Syndrome (TS), using GCTA. Our analysis yielded a heritability point estimate of 0.58 (se = 0.09, p = 5.64e-12) for TS, and 0.37 (se = 0.07, p = 1.5e-07) for OCD. In addition, we conducted multiple genomic partitioning analyses to identify genomic elements that concentrate this heritability. We examined genomic architectures of TS and OCD by chromosome, MAF bin, and functional annotations. In addition, we assessed heritability for early onset and adult onset OCD. Among other notable results, we found that SNPs with a minor allele frequency of less than 5% accounted for 21% of the TS heritability and 0% of the OCD heritability. Additionally, we identified a significant contribution to TS and OCD heritability by variants significantly associated with gene expression in two regions of the brain (parietal cortex and cerebellum) for which we had available expression quantitative trait loci (eQTLs). Finally we analyzed the genetic correlation between TS and OCD, revealing a genetic correlation of 0.41 (se = 0.15, p = 0.002). These results are very close to previous heritability estimates for TS and OCD based on twin and family studies, suggesting that very little, if any, heritability is truly missing (i.e., unassayed) from TS and OCD GWAS studies of common variation. The results also indicate that there is some genetic overlap between these two phenotypically-related neuropsychiatric disorders, but suggest that the two disorders have distinct genetic architectures.

GDNF gene is associated with tourette syndrome in a family study.

BACKGROUND: Tourette syndrome is a disorder characterized by persistent motor and vocal tics, and frequently accompanied by the comorbidities attention deficit hyperactivity disorder and obsessive-compulsive disorder. Impaired synaptic neurotransmission has been implicated in its pathogenesis. Our aim was to investigate the association of 28 candidate genes, including genes related to synaptic neurotransmission and neurotrophic factors, with Tourette syndrome. METHODS: We genotyped 506 polymorphisms in a discovery cohort from the United States composed of 112 families and 47 unrelated singletons with Tourette syndrome (201 cases and 253 controls). Genes containing significant polymorphisms were imputed to fine-map the signal(s) to potential causal variants. Allelic analyses in Tourette syndrome cases were performed to check the role in attention deficit hyperactivity disorder and obsessive-compulsive disorder comorbidities. Target polymorphisms were further studied in a replication cohort from southern Spain composed of 37 families and three unrelated singletons (44 cases and 73 controls). RESULTS: The polymorphism rs3096140 in glial cell line-derived neurotrophic factor gene (GDNF) was significant in the discovery cohort after correction (P = 1.5 × 10(-4) ). No linkage disequilibrium was found between rs3096140 and other functional variants in the gene. We selected rs3096140 as target polymorphism, and the association was confirmed in the replication cohort (P = 0.01). No association with any comorbidity was found. CONCLUSIONS: As a conclusion, a common genetic variant in GDNF is associated with Tourette syndrome. A defect in the production of GDNF could compromise the survival of parvalbumin interneurons, thus altering the excitatory/inhibitory balance in the corticostriatal circuitry. Validation of this variant in other family cohorts is necessary.

The Tourette International Collaborative Genetics (TIC Genetics) study, finding the genes causing Tourette syndrome: objectives and methods.

Tourette syndrome (TS) is a neuropsychiatric disorder characterized by recurrent motor and vocal tics, often accompanied by obsessive-compulsive disorder and/or attention-deficit/hyperactivity disorder. While the evidence for a genetic contribution is strong, its exact nature has yet to be clarified fully. There is now mounting evidence that the genetic risks for TS include both common and rare variants and may involve complex multigenic inheritance or, in rare cases, a single major gene. Based on recent progress in many other common disorders with apparently similar genetic architectures, it is clear that large patient cohorts and open-access repositories will be essential to further advance the field. To that end, the large multicenter Tourette International Collaborative Genetics (TIC Genetics) study was established. The goal of the TIC Genetics study is to undertake a comprehensive gene discovery effort, focusing both on familial genetic variants with large effects within multiply affected pedigrees and on de novo mutations ascertained through the analysis of apparently simplex parent-child trios with non-familial tics. The clinical data and biomaterials (DNA, transformed cell lines, RNA) are part of a sharing repository located within the National Institute for Mental Health Center for Collaborative Genomics Research on Mental Disorders, USA, and will be made available to the broad scientific community. This resource will ultimately facilitate better understanding of the pathophysiology of TS and related disorders and the development of novel therapies. Here, we describe the objectives and methods of the TIC Genetics study as a reference for future studies from our group and to facilitate collaboration between genetics consortia in the field of TS.

L-histidine decarboxylase and Tourette's syndrome.

Tourette's syndrome is a common developmental neuropsychiatric disorder characterized by chronic motor and vocal tics. Despite a strong genetic contribution, inheritance is complex, and risk alleles have proven difficult to identify. Here, we describe an analysis of linkage in a two-generation pedigree leading to the identification of a rare functional mutation in the HDC gene encoding L-histidine decarboxylase, the rate-limiting enzyme in histamine biosynthesis. Our findings, together with previously published data from model systems, point to a role for histaminergic neurotransmission in the mechanism and modulation of Tourette's syndrome and tics.

Common and rare alleles of the serotonin transporter gene, SLC6A4, associated with Tourette's disorder.

To evaluate the hypothesis that functionally over-expressing alleles of the serotonin transporter (SERT) gene (solute carrier family 6, member 4, SLC6A4) are present in Tourette's disorder (TD), just as we previously observed in obsessive compulsive disorder (OCD), we evaluated TD probands (N = 151) and controls (N = 858). We genotyped the refined SERT-linked polymorphic region 5-HTTLPR/rs25531 and the associated rs25532 variant in the SLC6A4 promoter plus the rare coding variant SERT isoleucine-to-valine at position 425 (I425V). The higher expressing 5-HTTLPR/rs25531 LA allele was more prevalent in TD probands than in controls (χ(2) = 5.75; P = 0.017; odds ratio [OR], 1.35); and, in a secondary analysis, surprisingly, it was significantly more frequent in probands who had TD alone than in those who had TD plus OCD (Fisher's exact test; P = 0.0006; OR, 2.29). Likewise, the higher expressing LAC haplotype (5-HTTLPR/rs25531/rs25532) was more frequent in TD probands than in controls (P = 0.024; OR, 1.33) and also in the TD alone group versus the TD plus OCD group (P = 0.0013; OR, 2.14). Furthermore, the rare gain-of-function SERT I425V variant was observed in 3 male siblings with TD and/or OCD and in their father. Thus, the cumulative count of SERT I425V becomes 1.57% in OCD/TD spectrum conditions versus 0.15% in controls, with a recalculated, family-adjusted significance of χ(2) = 15.03 (P < 0.0001; OR, 9.0; total worldwide genotyped, 2914). This report provides a unique combination of common and rare variants in one gene in TD, all of which are associated with SERT gain of function. Thus, altered SERT activity represents a potential contributor to serotonergic abnormalities in TD. The present results call for replication in a similarly intensively evaluated sample. © 2013 Movement Disorder Society.

Human mutations in high-confidence Tourette disorder genes affect sensorimotor behavior, reward learning, and striatal dopamine in mice.

Tourette disorder (TD) is poorly understood, despite affecting 1/160 children. A lack of animal models possessing construct, face, and predictive validity hinders progress in the field. We used CRISPR/Cas9 genome editing to generate mice with mutations orthologous to human de novo variants in two high-confidence Tourette genes, CELSR3 and WWC1 . Mice with human mutations in Celsr3 and Wwc1 exhibit cognitive and/or sensorimotor behavioral phenotypes consistent with TD. Sensorimotor gating deficits, as measured by acoustic prepulse inhibition, occur in both male and female Celsr3 TD models. Wwc1 mice show reduced prepulse inhibition only in females. Repetitive motor behaviors, common to Celsr3 mice and more pronounced in females, include vertical rearing and grooming. Sensorimotor gating deficits and rearing are attenuated by aripiprazole, a partial agonist at dopamine type II receptors. Unsupervised machine learning reveals numerous changes to spontaneous motor behavior and less predictable patterns of movement. Continuous fixed-ratio reinforcement shows Celsr3 TD mice have enhanced motor responding and reward learning. Electrically evoked striatal dopamine release, tested in one model, is greater. Brain development is otherwise grossly normal without signs of striatal interneuron loss. Altogether, mice expressing human mutations in high-confidence TD genes exhibit face and predictive validity. Reduced prepulse inhibition and repetitive motor behaviors are core behavioral phenotypes and are responsive to aripiprazole. Enhanced reward learning and motor responding occurs alongside greater evoked dopamine release. Phenotypes can also vary by sex and show stronger affection in females, an unexpected finding considering males are more frequently affected in TD. Significance Statement: We generated mouse models that express mutations in high-confidence genes linked to Tourette disorder (TD). These models show sensorimotor and cognitive behavioral phenotypes resembling TD-like behaviors. Sensorimotor gating deficits and repetitive motor behaviors are attenuated by drugs that act on dopamine. Reward learning and striatal dopamine is enhanced. Brain development is grossly normal, including cortical layering and patterning of major axon tracts. Further, no signs of striatal interneuron loss are detected. Interestingly, behavioral phenotypes in affected females can be more pronounced than in males, despite male sex bias in the diagnosis of TD. These novel mouse models with construct, face, and predictive validity provide a new resource to study neural substrates that cause tics and related behavioral phenotypes in TD.

Rare X-linked variants carry predominantly male risk in autism, Tourette syndrome, and ADHD.

Autism spectrum disorder (ASD), Tourette syndrome (TS), and attention-deficit/hyperactivity disorder (ADHD) display strong male sex bias, due to a combination of genetic and biological factors, as well as selective ascertainment. While the hemizygous nature of chromosome X (Chr X) in males has long been postulated as a key point of "male vulnerability", rare genetic variation on this chromosome has not been systematically characterized in large-scale whole exome sequencing studies of "idiopathic" ASD, TS, and ADHD. Here, we take advantage of informative recombinations in simplex ASD families to pinpoint risk-enriched regions on Chr X, within which rare maternally-inherited damaging variants carry substantial risk in males with ASD. We then apply a modified transmission disequilibrium test to 13,052 ASD probands and identify a novel high confidence ASD risk gene at exome-wide significance (MAGEC3). Finally, we observe that rare damaging variants within these risk regions carry similar effect sizes in males with TS or ADHD, further clarifying genetic mechanisms underlying male vulnerability in multiple neurodevelopmental disorders that can be exploited for systematic gene discovery.

Genome-wide Association Study Points to Novel Locus for Gilles de la Tourette Syndrome.

BACKGROUND: Tourette syndrome (TS) is a childhood-onset neurodevelopmental disorder of complex genetic architecture and is characterized by multiple motor tics and at least one vocal tic persisting for more than 1 year. METHODS: We performed a genome-wide meta-analysis integrating a novel TS cohort with previously published data, resulting in a sample size of 6133 individuals with TS and 13,565 ancestry-matched control participants. RESULTS: We identified a genome-wide significant locus on chromosome 5q15. Integration of expression quantitative trait locus, Hi-C (high-throughput chromosome conformation capture), and genome-wide association study data implicated the NR2F1 gene and associated long noncoding RNAs within the 5q15 locus. Heritability partitioning identified statistically significant enrichment in brain tissue histone marks, while polygenic risk scoring of brain volume data identified statistically significant associations with right and left thalamus volumes and right putamen volume. CONCLUSIONS: Our work presents novel insights into the neurobiology of TS, thereby opening up new directions for future studies.