Exome sequencing in bipolar disorder identifies AKAP11 as a risk gene shared with schizophrenia

Exome sequencing analysis of 13,933 individuals with bipolar disorder finds enrichment of ultra-rare protein-truncating variants in constrained genes. Combined analysis with schizophrenia exome data identifies AKAP11 as a risk gene for both disorders. We report results from the Bipolar Exome (BipEx) collaboration analysis of whole-exome sequencing of 13,933 patients with bipolar disorder (BD) matched with 14,422 controls. We find an excess of ultra-rare protein-truncating variants (PTVs) in patients with BD among genes under strong evolutionary constraint in both major BD subtypes. We find enrichment of ultra-rare PTVs within genes implicated from a recent schizophrenia exome meta-analysis (SCHEMA; 24,248 cases and 97,322 controls) and among binding targets of CHD8. Genes implicated from genome-wide association studies (GWASs) of BD, however, are not significantly enriched for ultra-rare PTVs. Combining gene-level results with SCHEMA, AKAP11 emerges as a definitive risk gene (odds ratio (OR) = 7.06, P = 2.83 x 10(-9)). At the protein level, AKAP-11 interacts with GSK3B, the hypothesized target of lithium, a primary treatment for BD. Our results lend support to BD's polygenicity, demonstrating a role for rare coding variation as a significant risk factor in BD etiology.

Automated summary

Exome sequencing analysis of individuals with bipolar disorder reveals enrichment of ultra-rare protein-truncating variants in constrained genes. AKAP11 is identified as a risk gene for both bipolar disorder and schizophrenia. This study highlights the importance of rare coding variation in the development of bipolar disorder.