A New Model of Spontaneous Colitis in Mice Induced by Deletion of an RNA m6A Methyltransferase Component METTL14 in T Cells

Abstract

We have found that deletion of RNA methylation writer METTL14 in T cells induced spontaneous colitis in mice. This is characterized by a Th1/Th17 phenotype. The colitis development was due to dysfunctional regulatory T cells and is dependent on the microbiome. BACKGROUND AND AIMS: Mouse models of colitis have been used to study the pathogenesis of inflammatory bowel disease (IBD) and for pre-clinical development of therapeutic agents. Various epigenetic pathways have been shown to play important regulatory roles in IBD. Reversible N 6-methyladenosine (m 6 A) methylation represents a new layer of post-transcriptional gene regulation that affects a variety of biological processes. We aim to study how deletion of a critical component of m 6 A writer complex, METTL14, in T cells affects the development of colitis. METHODS: Conditional Mettl14 was lineage specifically deleted with CD4-regulated Cre in T cells. Colitis phenotype was determined by H&E staining, colon weight-to-length ratio and cytokine expression. We additionally utilized T cell transfer model of colitis and adoptive transfer of regulatory T cells. Mice were treated with antibiotics to determine if the colitis could be attenuated. RESULTS: METTL14 deficiency in T cells induced spontaneous colitis in mice. This was characterized by increased inflammatory cell infiltration, increased colonic weight-to-length ratio and increased Th1 and Th17 cytokines. The colitis development was due to dysfunctional regulatory T (T reg) cells, as adoptive transfer of WT T reg cells attenuated the colitis phenotype. The METTL14-deficient T reg cells have decreased RORgt expression compared with WT controls. METTL14 deficiency caused impaired induction of naïve T cells into induced T reg cells. Antibiotic treatment notably attenuated the colitis development. CONCLUSION: Here we report a new mouse model of spontaneous colitis based on perturbation of RNA methylation in T cells. The colitis is T cell-mediated and dependent on the microbiome. This model represents a new tool for elucidating pathogenic pathways, studying the contribution of intestinal microbiome and preclinical testing of therapeutic agents for inflammatory bowel disease.

Emerging role of RNA modification N6-methyladenosine in immune evasion

“…Different from total CD4 T cell, the depletion of METTL3 in Treg cells lead to increase in the mRNAs of the SOCS gene family, suppress the IL2-STAT5 signaling pathway, and sustains the Treg suppressive function 53 . In addition, METTL14 deficiency in T cells increased inflammatory cell infiltration, also increased Th1 and Th17 cytokines 42 . METTL14 deficiency in mice could inhibit the naive T cells into induced T reg cells 42 .…”

“…In addition, METTL14 deficiency in T cells increased inflammatory cell infiltration, also increased Th1 and Th17 cytokines 42 . METTL14 deficiency in mice could inhibit the naive T cells into induced T reg cells 42 . Disruption of mTOR signal in Treg cells leads to Treg suppressive activity in immune tolerance because foreign signals through the TCR and IL-2 provide major inputs for mTOR activation 54 , while another study reports that the m6A modification could upregulated PI3K/Akt/mTOR signal pathway in cancer 55 .…”

“…We still think m6A mechanism plays an important role in TCR signals in response to antigen recognition on APC. It’s interestingly that METTL14 deficiency was characterized by increased inflammatory cell infiltration, with increase of Th1 and Th17 cytokines, and inhibits naive T cells into induced T reg cells 42 . However, another study suggests that METTL3-deficient T naive cells failed to proliferate under the lymphopenic conditions and are unable to differentiate into pathogenic effector T cells 43 .…”

Emerging Perspectives of RNA N6-methyladenosine (m6A) Modification on Immunity and Autoimmune Diseases

“…Although the etiology of IBD is illdefined, the dysregulation of proinflammatory Th17 cells and anti-inflammatory Treg cells contributes to the pathogenesis of IBD (78,79). Using CD4-Cre +/Tg Mettl14 FL/FL conditional knockout mice, Thomas X et al firstly demonstrated that METTL14 deficiency in T cells causes the development of spontaneous colitis by dramatically increasing the release of Th17 cell-related proinflammatory cytokines (80). Given the important role of m 6 A modification in maintaining Treg cell stability and their suppressive functions, it is reasonable to find that deletion of METTL14 impairs induction of Treg cells and consequently results in the imbalance between Th17 and Treg cells, ultimately inducing spontaneous colitis development.…”

RNA Methylation in Systemic Lupus Erythematosus

“…In addition to METTL3, METTL14 deficiency in T cells also induces unbalanced T cell homeostasis. A METTL14 deficiency in T cells induces spontaneous colitis in mice, manifesting as increased inflammatory cell infiltration and cytokine production from Th1 and Th17 cells ( Lu T. X. et al, 2020 ). The Mettl14 deficiency also caused impaired induction of the differentiation of naïve T cells into induced Tregs ( Lu T. X. et al, 2020 ).…”