Evidence for enhancer activity in intron 1 of TNFRSF1A using CRISPR/Cas9 in human induced pluripotent stem cell-derived macrophages.

TNFα is a common drug target in the treatment of autoimmune diseases, with pro-inflammatory functions that are primarily mediated through its receptor, TNFRSF1A. TNFRSF1A has been genetically associated with many immune-mediated diseases including ankylosing spondylitis, multiple sclerosis, and inflammatory bowel disease. Many of the genetic variants within or near TNFRSF1A that have been associated with disease through genome-wide association studies (GWAS) lie in non-coding regions of the genome. Understanding the functional consequences of these genetic variants is limited by incomplete understanding of TNFRSF1A gene regulation, including for specific cellular contexts relevant to inflammation and immunity such as macrophages. This work used CRISPR/Cas9 in human induced pluripotent stem cells followed by differentiation into macrophages to investigate putative regulatory elements in the TNFRSF1A gene locus. Through gene editing, with functional genomic readouts including the assay for transposase-accessible chromatin using sequencing (ATAC-Seq), chromatin immunoprecipitation with sequencing (ChIP-Seq), and RNA-Seq to assess the consequences of these edits, we present evidence for an enhancer of TNFRSF1A contained within an intron of the gene. Understanding gene regulation and the genomic context in which GWAS variants lie could bring us closer to deconvoluting the genetic basis of common disease aetiology and uncover effective drug targets.