7/9 Rare Genetic Disorders as a Window into the Genetic Architecture of Mental Disorders

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PROJECT SUMMARY The International Consortium on Brain and Behavior Copy Number Variants (IBBC-CNVs) is a collaborative effort of 9 institutions with complementary experience and expertise in phenomics and genomics. The 22q11.2 and 16p11.2 loci are associated with significant risk for neuropsychiatric disorders across the lifespan. The clinical presentations are heterogeneous, manifesting in a range of developmental neuropsychiatric disorders, including Attention Deficit Hyperactivity, Anxiety, Autism Spectrum, and Psychosis Spectrum Disorders. Taking a `genetics first' approach of ascertaining patients based on known, homogeneous genetic etiologies will allow us to overcome barriers posed by the genetic and phenotypic complexity of idiopathic developmental neuropsychiatric disorders. We postulate that CNVs exert a large main effect on psychopathology, but the nature and degree of psychopathology observed in CNV carriers is multifactorial, with contributions from additional rare and common genetic variants, as well as environmental factors. Therefore, dissecting the effects of major CNV hits as well as additional rare and common variants on dimensional measures of psychopathology can elucidate the combined contribution of genetic mechanisms to psychiatric conditions and build models of risk prediction. Notably, the presentation and course of psychopathology in the CNVs resemble these features in idiopathic disorders. Therefore, beyond the specific genetic syndromes investigated, such a cross-CNV effort will identify convergent risk mechanisms for developmental neuropsychiatric disorders that are of relevance to the broader population. We propose to dissect dimensional measures of psychosis, social-emotional processing and neurocognition, and their genetic and environmental modifiers, to elucidate the architecture of risk for neuropsychiatric disorders in CNV carriers. Prospective evaluation with dimensional measures relevant to neuropsychiatric disorders will be applied to a cohort of 2000 individuals with 22q11.2 and 16p11.2 deletions and duplications (500 per group) and their relatives as feasible. In addition, categorical psychiatric diagnoses will be assessed in CNV carriers. Recruitment for prospective phenotyping will leverage existing large cohorts that carry these reciprocal CNVs, many of whom have already been ascertained and characterized with a range of phenotypic measures. New whole genome sequencing (WGS) will be performed in CNV carriers that have not yet been sequenced. We will also utilize existing genetic data from the largest available case-control samples diagnosed with SZ, ASD, and ADHD in the PGC. Finally, analysis of common variants for a subset of family members will allow us to complement our primary analysis by exploring models of complex genetic inheritance in extended pedigrees that carry CNVs. Our ability to conceive such a large scale study capitalizes on our existing successful collaborations, complementary expertise, and institutional commitments to achieve these goals.