The Role of m6A RNA Methylation in Intestinal Inflammation

FUT2 is identified as a genetic risk factor for CD. It regulates epithelial fucosylation and shapes host–microbiota interactions. We observed that FUT2 was upregulated in CD patients in publicly available transcriptome data. Given that Fut2 transcript was found to be differentially methylated between germ-free and conventional mice⁴², we generated a Fut2 knock-in mouse model with point mutations at identified methylation sites to further understand the role of the microbiota regulating FUT2 expression and potential effects in modulating intestinal inflammation. We observed that Fut2 KI mice displayed higher Fut2 expression on both mRNA and protein levels compared with WT mice, indicating that m⁶A modifications reduce the stability of the Fut2 transcript. We assessed multiple proinflammatory cytokines in the gut from WT and Fut2-KI mice, but we didn’t find any induction of spontaneous inflammation, which was confirmed by histological stainings.

Based on a previous study by Jabs et al. demonstrating reduced expression of Mettl16 in the absence of a microbiota, we wanted to understand whether Mettl16 was the RNA-methyltransferase responsible for methylating the Fut2 transcript, thereby regulating its expression. We established Mettl16ΔIEC mice and analyzed the RNA and protein expression of Fut2. However, the results showed that Fut2 is not a direct target of Mettl16 in the IEC-specific KO mice. We observed that loss of METTL16 in intestinal epithelial cells leads to spontaneous downregulation of pro-inflammatory cytokines such as Cxcl10 and Ifng, as well as a reduced crypt depth. Although Fut2 expression remained unchanged, Mettl16 deficiency resulted in a decreased intensity of the fucose-specific lectin UEA1, suggesting its role in impaired fucosylation processes.

Taken together, our data supported a potential role for m⁶A in modulating Fut2 expression, offering a foundation for future mechanistic and functional studies in the context of gut inflammation.