Type 1 diabetes (T1D) is an autoimmune disease characterized by a progressive destruction of β-cells and several candidate genes associated with T1D have been linked to innate immunity. Recently, N6-methyladenosine (m6A) has been shown to modulate human β-cell biology and to target type I interferons. Here, we focused on the contribution of m6A mRNA methylation in modulating innate immunity and β-cell destruction. Immune cells contribute to β-cell apoptosis by the release of pro-inflammatory cytokines during the onset of T1D. We assessed whether m6A abundance or expression of m6A modulators was altered in human islets and EndoC-βH1 cells treated with cytokines to mimick T1D onset. LC-MS/MS analyses of human islets showed that treatment with IL-1β plus IFN-α for 48h increased m6A levels. Consistently, IL-1β plus IFN-α treatment of human islets and EndoC-βH1 induced upregulation of the m6A writer METTL3. Next, we applied m6A-sequencing in cytokine-treated human islet preparations, and in parallel studies, treated EndoC-βH1 cells followed by RNA-sequencing. Intersection of m6A-decorated genes in cytokine-treated human islets with common differentially expressed genes in human islets and EndoC-βH1 cells revealed enrichment in pathways associated with the innate immune response, negative regulation of immune response, and extrinsic apoptotic signaling pathway. Differentially expressed and m6A decorated genes included genes associated with T1D that are involved in innate immunity. Re-analyses of RNA-seq. data in sorted-β-cells from T1D patients revealed downregulation of METTL3. These data suggest that while healthy β-cells are able to upregulate m6A levels and METTL3 early in T1D (e.g., when they are exposed to cytokines), this response is lost in established T1D that allows an exacerbated immune response and β-cell death. Together, these results point to a possible therapeutic approach in targeting METTL3 to modulate innate immunity and promote β-cell survival.
D. F. De jesus: None. C. He: None. R. Kulkarni: None. Z. Zhang: None. N. K. Brown: None. J. Hu: None. S. Kahraman: None. C. E. Mathews: None. A. C. Powers: None. M. A. Atkinson: None. D. L. Eizirik: None.
National Institutes of Health (1UC4DK116278)