285-OR: Surveying Specific and Shared Responses of Human Islets to T2D-Associated Stressors

Abstract

Endoplasmic reticulum (ER) and inflammatory stress in islets is linked to Type 2 Diabetes (T2D). We hypothesize that a subset of non-coding T2D-associated genetic variants (T2D SNPs) modulate these pathophysiologic responses in human islets. To test this, we compared chromatin accessibility and gene expression in human islets before and after exposure to ER stress (thapsigargin) or pro-inflammatory cytokines (IL-1β+IFN-γ) to identify specific and shared stress-responsive cis-regulatory elements (CREs) and their target genes. Approximately 13% of CREs (n=14,966) and 30% of genes (n=5,131) are modulated by ≥1 stressor (ER stress-specific: ~41% CREs & ~33% genes, inflammation-specific: ~52% CREs & ~42% genes, shared: ~7% CREs & ~25% genes), implying that changes in accessibility and expression in islets are stress-specific. For example, ER stress-specific genes (ex: DDIT3 & ATF4) are involved in unfolded protein response, and ER stress-specific CREs enrich for 157 transcription factor (TF) binding sites (ex: CHOP & ATF4). Many genes nearest to stress-responsive CREs are also stress-responsive genes (ER stress-specific: n=596, inflammation-specific: n=827, shared: n=91) suggesting a context-specific modulation of gene expression by CREs. Of these CREs, 92 (ER stress: n=53, inflammation: n=39) harbor 114 T2D SNPs, of which 19 T2D SNPs become accessible only upon ER stress. For example, rs6444081 (A>G) overlaps an ER stress-specific CRE and resides downstream of ETV5 (ER stress-responsive gene). The T2D risk allele (G) is predicted to be bound by ER stress-specific TF ETV1. In a separate cohort, ETV5 expression is higher in T2D vs non-T2D beta cells, suggesting that ETV5 is a putative target gene of rs6444081 and that its activity is genetically modulated in islets. Our results nominate T2D SNPs that we propose modulate stress-specific islet responses. Further study of these CREs and their target genes should help to functionally compartmentalize T2D risk variants. Disclosure E.K.Sokolowski: None. R.M.Bhuiyan: None. R.Kursawe: None. M.L.Stitzel: None. D.Ucar: None. Funding National Institutes of Health (R01DK118011-01A1); U.S. Department of Defense (W81XWH-18-0401)