m6A RNA modification is implicated in multiple cellular responses. However, its function in the innate immune cells is poorly understood. Here, we identified major m6A “writers” as the top candidate genes regulating macrophage activation by LPS in an RNA binding protein focused CRISPR screening. We have confirmed that Mettl3-deficient macrophages exhibited reduced TNF-α production upon LPS stimulation in vitro. Consistently, Mettl3flox/flox;Lyzm-Cre mice displayed increased susceptibility to bacterial infection and showed faster tumor growth. Mechanistically, the transcripts of the Irakm gene encoding a negative regulator of TLR4 signaling were highly decorated by m6A modification. METTL3 deficiency led to the loss of m6A modification on Irakm mRNA and slowed down its degradation, resulting in a higher level of IRAKM, which ultimately suppressed TLR signaling–mediated macrophage activation. Our findings demonstrate a previously unknown role for METTL3-mediated m6A modification in innate immune responses and implicate the m6A machinery as a potential cancer immunotherapy target.

Colonic mucosal barrier dysfunction is one of the major causes of inflammatory bowel disease (IBD). However, the mechanisms underlying mucosal barrier dysfunction are poorly understood. N 6 -methyladenosine (m 6 A) mRNA modification is an important modulator of epitranscriptional regulation of gene expression, participating in multiple physiological and pathological processes. However, the function of m 6 A modification in colonic epithelial cells and stem cells is unknown. Here, we show that m 6 A modification is essential for maintaining the homeostatic self-renewal in colonic stem cells. Specific deletion of the methyltransferase 14 ( Mettl14 ) gene in mouse colon resulted in colonic stem cell apoptosis, causing mucosal barrier dysfunction and severe colitis. Mechanistically, we revealed that Mettl14 restricted colonic epithelial cell death by regulating the stability of Nfkbia mRNA and modulating the NF-κB pathway. Our results identified a previously unidentified role for m 6 A modification in colonic epithelial cells and stem cells, suggesting that m 6 A modification may be a potential therapeutic target for IBD.

Glomerulonephritis is the one of the major causes of the end‐stage kidney disease, whereas the pathological process of glomerulonephritis is still not completely understood. Single‐cell RNA sequencing (scRNA‐seq) emerges to be a powerful tool to evaluate the full heterogeneity of kidney diseases. To reveal cellular gene expression profiles of glomerulonephritis, we performed scRNA‐seq of 2 human kidney transplantation donor samples, 4 human glomerulonephritis samples, 1 human malignant hypertension (MH) sample and 1 human chronic interstitial nephritis (CIN) sample, all tissues were taken from the biopsy. After filtering the cells with < 200 genes and > 10% mitochondria (MT) genes, the resulting 14 932 cells can be divided into 20 cell clusters, consistently with the previous report, in disease samples dramatic immune cells infiltration was found, among which a proximal tubule (PT) subset characterized by wnt‐β catenin activation and a natural killer T (NKT) subset high expressing LTB were found. Furthermore, in the cluster of the podocyte, three glomerulonephritis related genes named FXYD5, CD74 and B2M were found. Compared with the mesangial of donor, the gene CLIC1 and RPS26 were up‐regulated in mesangial of IgA nephropathy(IgAN), whereas the gene JUNB was up‐regulated in podocyte of IgAN in comparison with that of donor. Meanwhile, some membranous nephropathy (MN) high expressed genes such as HLA‐DRB5, HLA‐DQA2, IFNG, CCL2 and NR4A2, which involve in highest enrichment pathway, display the cellular‐specific expression style, whereas monocyte marker of lupus nephritis (LN) named TNFSF13B was also found and interferon alpha/beta signalling pathway was enriched in B and NKT of LN comparing with donor. By scRNA‐seq, we first defined the podocyte markers of glomerulonephritis and specific markers in IgA, MN and LN were found at cellular level. Furthermore, the critical role of interferon alpha/beta signalling pathway was enriched in B and NKT of LN was declared.