1. Identification of Two Heritable Cross-Disorder Endophenotypes for Tourette Syndrome.
- Author
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Darrow SM, Hirschtritt ME, Davis LK, Illmann C, Osiecki L, Grados M, Sandor P, Dion Y, King R, Pauls D, Budman CL, Cath DC, Greenberg E, Lyon GJ, Yu D, McGrath LM, McMahon WM, Lee PC, Delucchi KL, Scharf JM, and Mathews CA
- Subjects
- Adolescent, Adult, Attention Deficit Disorder with Hyperactivity diagnosis, Attention Deficit Disorder with Hyperactivity psychology, Child, Child of Impaired Parents, Child, Preschool, Comorbidity, Female, Genetic Predisposition to Disease genetics, Genome-Wide Association Study, Humans, Male, Middle Aged, Mothers psychology, Multifactorial Inheritance genetics, Obsessive-Compulsive Disorder diagnosis, Obsessive-Compulsive Disorder psychology, Phenotype, Risk Assessment, Tourette Syndrome diagnosis, Tourette Syndrome psychology, Young Adult, Attention Deficit Disorder with Hyperactivity genetics, Endophenotypes, Obsessive-Compulsive Disorder genetics, Tourette Syndrome genetics
- Abstract
Objective: Phenotypic heterogeneity in Tourette syndrome is partly due to complex genetic relationships among Tourette syndrome, obsessive-compulsive disorder (OCD), and attention deficit hyperactivity disorder (ADHD). Identifying symptom-based endophenotypes across diagnoses may aid gene-finding efforts., Method: Assessments for Tourette syndrome, OCD, and ADHD symptoms were conducted in a discovery sample of 3,494 individuals recruited for genetic studies. Symptom-level factor and latent class analyses were conducted in Tourette syndrome families and replicated in an independent sample of 882 individuals. Classes were characterized by comorbidity rates and proportion of parents included. Heritability and polygenic load associated with Tourette syndrome, OCD, and ADHD were estimated., Results: The authors identified two cross-disorder symptom-based phenotypes across analyses: symmetry (symmetry, evening up, checking obsessions; ordering, arranging, counting, writing-rewriting compulsions, repetitive writing tics) and disinhibition (uttering syllables/words, echolalia/palilalia, coprolalia/copropraxia, and obsessive urges to offend/mutilate/be destructive). Heritability estimates for both endophenotypes were high and statistically significant (disinhibition factor=0.35, SE=0.03; symmetry factor=0.39, SE=0.03; symmetry class=0.38, SE=0.10). Mothers of Tourette syndrome probands had high rates of symmetry (49%) but not disinhibition (5%). Polygenic risk scores derived from a Tourette syndrome genome-wide association study (GWAS) were significantly associated with symmetry, while risk scores derived from an OCD GWAS were not. OCD polygenic risk scores were significantly associated with disinhibition, while Tourette syndrome and ADHD risk scores were not., Conclusions: The analyses identified two heritable endophenotypes related to Tourette syndrome that cross traditional diagnostic boundaries. The symmetry phenotype correlated with Tourette syndrome polygenic load and was present in otherwise Tourette-unaffected mothers, suggesting that this phenotype may reflect additional Tourette syndrome (rather than OCD) genetic liability that is not captured by traditional DSM-based diagnoses.
- Published
- 2017
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