Epigenetic modulation of ß-cells by interferon-a via PNPT11-miR-26a-TET2 triggers autoimmune diabetes [RNA-seq]

Type 1 diabetes (T1D) is caused by autoimmune destruction of pancreatic ß cells. Mounting evidence supports a central role for ß-cell alterations in triggering the activation of self-reactive T-cells in T1D. However, the early deleterious events that occur in ß cells, underpinning islet autoimmunity are not known. We hypothesized that epigenetic modifications induced in ß cells by inflammatory mediators play a key role in initiating the autoimmune response. We analyzed DNA methylation (DNAm) patterns and gene expression in human islets exposed to IFNa, a cytokine associated with T1D development. We found that IFNa triggers DNA demethylation and increases expression of genes controlling inflammatory and immune pathways. We then demonstrated that DNA demethylation was caused by up-regulation of the exoribonuclease, PNPase Old-35 (PNPT1), which caused degradation of miR-26a. This in turn promoted the up-regulation of ten-eleven translocation TET2 enzyme and increased 5-hydoxymethylcytosine levels in human islets and pancreatic ß-cells. Moreover, we showed that specific IFNa expression in the ß cells of IFNa-INS1CreERT2 transgenic mice, led to development of T1D that was preceded by increased islet DNA hydroxymethylation through a PNPT1/TET2-dependent mechanism. Our results suggest a new mechanism through which IFNa regulates DNAm in ß cells, leading to changes in expression of genes in inflammatory and immune pathways that can initiate islet autoimmunity in T1D. Overall design: We exposed human pancreatic islets from three donors to 2000 IU IFNa and assessed gene expression by RNAseq. The cDNA library was prepared using Illumina TruSeq RNA Sample Prep Kits. Next generation sequencing was performed on Illumina HiSeq2000 using the Single-Read Cluster Generation kit v2 and SBS Sequencing kit v3. Image analysis and base calling were conducted using the SDS 2.5/RTA1.5 software.

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Stefan-Lifshitz M, Karakose E, Cui L, Ettela A, Yi Z, Zhang W, Tomer Y