Open Chromatin Profiling in hiPSC-Derived Neurons Prioritizes Functional Noncoding Psychiatric Risk Variants and Highlights Neurodevelopmental Loci

Most disease variants lie within noncoding genomic regions, making their functional interpretation challenging. Because chromatin openness strongly influences transcriptional activity, we hypothesized that cell-type-specific open chromatin regions (OCRs) might highlight disease-relevant noncoding sequences. To investigate, we mapped global OCRs in neurons differentiating from hiPSCs, a cellular model for studying neurodevelopmental disorders such as schizophrenia (SZ). We found that the OCRs are highly dynamic and can stratify GWAS-implicated SZ risk variants. Of the more than 3,500 SZ-associated variants analyzed, we prioritized ∼100 putatively functional ones located in neuronal OCRs, including rs1198588, at a leading risk locus flanking MIR137. Excitatory neurons derived from hiPSCs with CRISPR/Cas9-edited rs1198588 or a rare proximally located SZ risk variant showed altered MIR137 expression, dendrite arborization, and synapse maturation. Our study shows that noncoding disease variants in OCRs can affect neurodevelopment, and that analysis of open chromatin regions can help prioritize functionally relevant noncoding variants identified by GWAS. [Display omitted] •Open chromatin undergoes dynamic change during hiPSC neuronal differentiation•Neuronal open chromatin prioritizes a subset of noncoding psychiatric risk variants•Schizophrenia risk SNPs alter promoter open chromatin and expression of MIR137•CRISPR editing of schizophrenia risk SNP in MIR137 OCR affects neurodevelopment Forrest et al. outline an approach for prioritizing noncoding GWAS risk variants using open chromatin analysis in differentiating hiPSCs. They further show that CRISPR/Cas9 editing of prioritized schizophrenia risk SNPs near MIR137 alters gene expression, open chromatin, and neurodevelopment in hiPSC-derived neurons.