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Am J Psychiatry. 2017 Nov 1;174(11):1054-1063. doi: 10.1176/appi.ajp.2017.16121417. Epub 2017 Jul 28.

Rare Genome-Wide Copy Number Variation and Expression of Schizophrenia in 22q11.2 Deletion Syndrome.

Author information

1
From the Dalglish Family 22q Clinic, Department of Psychiatry, University Health Network, Toronto; the Department of Psychiatry and Toronto General Research Institute, University Health Network, Toronto; the Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto; the Department of Psychiatry, University of Toronto, Toronto; the Clinical Genetics Research Program, Centre for Addiction and Mental Health, Toronto; the Centre for Applied Genomics and Program in Genetics and Genome Biology, the Hospital for Sick Children, Toronto; the Medical Genetics Residency Training Program, University of Toronto, Toronto; the Department of Psychiatry and Psychology, Maastricht University, Maastricht, the Netherlands; the Division of Human Genetics, Children's Hospital of Philadelphia, Philadelphia; the Departments of Pediatrics and of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia; the Centre for Human Genetics, University of Leuven (KU Leuven), Leuven, Belgium; the Division of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff, Wales; the Department of Psychiatry, Royal College of Surgeons in Ireland, Dublin; the Department of Child and Adolescent Psychiatry, King's College London; the Department of Psychiatry, Tel Aviv University, Tel Aviv, Israel; the Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, UCLA, Los Angeles; Office Médico-Pédagogique Research Unit, Department of Psychiatry, University of Geneva School of Medicine, Geneva; the Department of Psychiatry and Behavioral Sciences, Upstate Medical University, State University of New York, Syracuse; Département de Génétique Médicale, Centre Hospitalier Universitaire de Marseille - Hôpital de la Timone, Marseilles, France; the Department of Pediatrics, Duke University, Durham, N.C.; the Department of Psychology, University of Newcastle, Newcastle, Australia; the Department of Psychiatry, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, the Netherlands; the Department of Human Genetics, Emory University, Atlanta; Centro de Genética y Genómica, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile; the Department of Psychiatry and Behavioral Sciences, UC Davis, Sacramento, Calif.; Molecular Genetics and McLaughlin Centre, and Laboratory Medicine and Pathobiology, University of Toronto, Toronto; the Department of Genetics, Albert Einstein College of Medicine, Bronx, N.Y.; and Genome Diagnostics, Department of Paediatric Laboratory Medicine, the Hospital for Sick Children, Toronto.

Abstract

OBJECTIVE:

Chromosome 22q11.2 deletion syndrome (22q11.2DS) is associated with a more than 20-fold increased risk for developing schizophrenia. The aim of this study was to identify additional genetic factors (i.e., "second hits") that may contribute to schizophrenia expression.

METHOD:

Through an international consortium, the authors obtained DNA samples from 329 psychiatrically phenotyped subjects with 22q11.2DS. Using a high-resolution microarray platform and established methods to assess copy number variation (CNV), the authors compared the genome-wide burden of rare autosomal CNV, outside of the 22q11.2 deletion region, between two groups: a schizophrenia group and those with no psychotic disorder at age ≥25 years. The authors assessed whether genes overlapped by rare CNVs were overrepresented in functional pathways relevant to schizophrenia.

RESULTS:

Rare CNVs overlapping one or more protein-coding genes revealed significant between-group differences. For rare exonic duplications, six of 19 gene sets tested were enriched in the schizophrenia group; genes associated with abnormal nervous system phenotypes remained significant in a stepwise logistic regression model and showed significant interactions with 22q11.2 deletion region genes in a connectivity analysis. For rare exonic deletions, the schizophrenia group had, on average, more genes overlapped. The additional rare CNVs implicated known (e.g., GRM7, 15q13.3, 16p12.2) and novel schizophrenia risk genes and loci.

CONCLUSIONS:

The results suggest that additional rare CNVs overlapping genes outside of the 22q11.2 deletion region contribute to schizophrenia risk in 22q11.2DS, supporting a multigenic hypothesis for schizophrenia. The findings have implications for understanding expression of psychotic illness and herald the importance of whole-genome sequencing to appreciate the overall genomic architecture of schizophrenia.

KEYWORDS:

22q11 Deletion Syndrome; DiGeorge Syndrome; Microdeletion; Psychosis; Schizophrenia; Structural Variants; Velocardiofacial Syndrome

PMID:
28750581
PMCID:
PMC5665703
DOI:
10.1176/appi.ajp.2017.16121417
[Indexed for MEDLINE]
Free PMC Article

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