Interpreting type 1 diabetes risk with genetics and single cell epigenomics

Genetic risk variants identified in genome-wide association studies (GWAS) of complex disease are primarily non-coding, and translating risk variants into mechanistic insight requires detailed gene regulatory maps in disease-relevant cell types. Here, we combined a GWAS of type 1 diabetes (T1D) in 520,580 samples with candidate cis-regulatory elements (cCREs) in pancreas and peripheral blood mononuclear cell types defined using single nucleus ATAC-seq (snATAC-seq) of 131,554 nuclei. T1D risk variants were enriched in cCREs active in T cells and additional cell types, including acinar and ductal cells of the exocrine pancreas. Risk variants at multiple T1D signals overlapped exocrine-specific cCREs linked to genes with exocrine-specific expression. At the CFTR locus, T1D risk variant rs7795896 mapped in a ductal-specific cCRE which regulated CFTR, and the risk allele reduced transcription factor binding, enhancer activity and CFTR expression in ductal cells. These findings support a role for the exocrine pancreas in T1D pathogenesis and highlight the power of large-scale GWAS and single cell epigenomics for understanding the cellular origins of complex disease. Overall design: Single nucleus ATAC-seq of purified pancreatic islets, whole pancreas, and peripheral mononuclear blood cells from human donors.