Expansion of Interleukin-22-producing Innate Lymphoid Cells in Tristetraprolindeficient mice protects against Dextran Sulfate Sodium-induced Colitis
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ABSTRACT: Tristetraprolin (TTP, encoded by Zfp36) is an RNA-binding protein that plays a major role in the control of inflammation. Zfp36 -/-mice spontaneously develop a complex multi-organ inflammatory syndrome that shares many features with spondyloarthritis. Herein, we show that Zfp36 -/-mice are paradoxically protected from Dextran Sulfate Sodium (DSS)-induced colitis. This effect was maintained on a Rag2 -/- background but was lost in Rag2 -/-Il2rg -/-Zfp36 -/-mice that lack innate lymphoid cells (ILCs). Furthermore, we observed a local expansion of type 3 ILCs in the lamina propria of Zfp36 -/-mice. These cells produced large amounts of Interleukin (IL)-22 and were expanded in response to systemic inflammation. Finally, we show that IL-22 contributed to protection of Zfp36 -/-mice against DSSinduced colitis but had a minor impact on their spontaneous inflammatory syndrome. Taken together, these data highlight the complex role of TTP in the control of organ-specific inflammation.
Project description:Tristetraprolin (TTP), encoded by the Zfp36 gene, is a zinc-finger protein that regulates RNA stability primarily through association with 3’ untranslated regions (3’UTRs) of target mRNAs. While TTP is expressed abundantly in the intestines, its function in intestinal epithelial cells (IECs) is unknown. Here we used a cre-lox system to remove Zfp36 in the mouse epithelium to uncover a role for TTP in IECs and to identify target genes in these cells. While TTP was largely dispensable for establishment and maintenance of the colonic epithelium, we found an expansion of the proliferative zone and an increase in goblet cell numbers in the colon crypts of Zfp36ΔIEC mice. Furthermore, through RNA-sequencing of transcripts isolated from the colons of Zfp36fl/fl and Zfp36ΔIEC mice, we found that expression of inducible nitric oxide synthase (iNos or Nos2) was elevated in TTP-knockout IECs. We demonstrate that TTP interacts with AU-rich elements in the Nos2 3’UTR and suppresses Nos2 expression. In comparison to control Zfp36fl/fl mice, Zfp36ΔIEC mice were less susceptible to dextran sodium sulfate (DSS)-induced acute colitis. Together, these results demonstrate that TTP targets Nos2 expression in IECs and aggravates acute colitis.
Project description:Members of the tristetraprolin (TTP) family of RNA-binding proteins can bind to and promote the decay of specific transcripts containing AU-rich motifs. ZFP36 (TTP) is best known for regulating cytokine expression in myeloid cells; however, the mammalian paralogues ZFP36L1 and ZFP36L2 have not been viewed as important in controlling inflammation. To study potential functional overlaps of these three TTP family proteins in myeloid cells, we developed myeloid-specific knock-out (M-KO) mice of these genes, singly and together. M-Zfp36-KO mice exhibited a mild inflammatory syndrome late in life, while M-Zfp36l1-KO and M-Zfp36l2-KO mice had no apparent spontaneous phenotypes. Mice with simultaneous deficiency of all three TTP family members in myeloid cells developed a severe, spontaneous, inflammatory phenotype, with a median survival of 8 weeks. Macrophages derived from these mice contained many more stabilized transcripts than cells from M-Zfp36-KO mice, many encoding pro-inflammatory cytokines and chemokines. Our findings emphasize the importance of all three family members, acting in concert, in myeloid cell function.
Project description:Members of the tristetraprolin (TTP) family of RNA-binding proteins can bind to and promote the decay of specific transcripts containing AU-rich motifs. ZFP36 (TTP) is best known for regulating cytokine expression in myeloid cells; however, the mammalian paralogues ZFP36L1 and ZFP36L2 have not been viewed as important in controlling inflammation. To study potential functional overlaps of these three TTP family proteins in myeloid cells, we developed myeloid-specific knock-out (M-KO) mice of these genes, singly and together. M-Zfp36-KO mice exhibited a mild inflammatory syndrome late in life, while M-Zfp36l1-KO and M-Zfp36l2-KO mice had no apparent spontaneous phenotypes. Mice with simultaneous deficiency of all three TTP family members in myeloid cells developed a severe, spontaneous, inflammatory phenotype, with a median survival of 8 weeks. Macrophages derived from these mice contained many more stabilized transcripts than cells from M-Zfp36-KO mice, many encoding pro-inflammatory cytokines and chemokines. Our findings emphasize the importance of all three family members, acting in concert, in myeloid cell function.
Project description:Tristetraprolin (TTP, encoded by Zfp36) regulates the mRNA stability of several important cytokines. Due to the critical role of this RNA-binding protein in the control of inflammation, TTP deficiency leads to the spontaneous development of a complex inflammatory syndrome. So far, this phenotype has been largely attributed to dysregulated production of TNF and IL-23 by myeloid cells such as macrophages or dendritic cells. Here, we generated mice with conditional deletion of TTP in keratinocytes. These mice developed exacerbated inflammation in the imiquimod-induced psoriasis model. Furthermore, these mice progressively developed a spontaneous pathology with systemic inflammation, psoriatic-like skin lesions and dactylitis. Finally, we provide evidence that keratinocyte-derived TNF productin drives the different pathological features. In summary, these findings expand current views on the initiation of psoriasis and related arthritis by revealing the keratinocyte-intrinsic role of TTP.
Project description:The fidelity of immune responses depends on a timely controlled and selective mRNA degradation that is largely driven by RNA-binding proteins (RBPs). It remains unclear whether the selection of an individual mRNA molecule for degradation is governed by stochastic or directed processes. Here, we show that tristetraprolin (TTP, also known as ZFP36), an essential anti-inflammatory RBP, destabilizes target mRNAs via a hierarchical molecular assembly. The formation of the assembly strictly relies on the interaction of TTP with RNA. The TTP homolog ZFP36L1 exhibits similar requirements, indicating a broader relevance of this regulatory program. Unexpectedly, the assembly of the cytoplasmic mRNA-destabilization complex is licensed in the nucleus by TTP binding to pre-mRNA, while cytoplasmic mRNA does not constitute a de novo TTP target. Hence, the fate of an inflammation-induced mRNA is decided concomitantly with its synthesis. This mechanism prevents the translation of excessive and potentially harmful inflammation mediators, irrespective of transcription.
Project description:Basophils play crucial roles in type 2 immune responses, such as chronic allergic inflammation and protective immunity against parasites. However, the molecular mechanisms regulating basophil activation and effector molecule production remain poorly understood. To investigate the role of RNA-binding proteins (RBPs), we first analyzed the gene expression of CCCH zinc finger proteins in antigen/IgE-stimulated basophils. Among these proteins, we identified that Zfp36, encoding tristetraprolin (TTP), was the most significantly upregulated gene. Therefore, we focused on the functions of TTP in basophils. We generated TTP-KO mice using the CRISPR-Cas9 method and conducted bulk RNA-seq analysis of antigen/IgE-stimulated basophils from wild-type (WT) and TTP-knockout (TTP-KO) mice. TTP-KO basophils exhibited elevated mRNA expression of pro-inflammatory mediators, such as Il4, Il13, Areg, Ccl3, and Cxcl2, compared to WT basophils. These data suggest that TTP is a key regulator of basophil activation, controlling the mRNA expression of inflammatory mediators.
Project description:Successful immune responses are dependent on a precisely controlled balance between transcription and mRNA degradation. mRNA decay is driven through RNA-binding proteins (RBP), yet it remains unclear, how and when an individual mRNA molecule is selected for degradation. We investigated this fundamental question by using the anti-inflammatory RBP tristetraprolin (TTP, also known as Zfp36) as a model. Here, we show that TTP determines the fate of its targets concomitantly with their synthesis by binding to the pre-mRNA in the nucleus. Furthermore, we provide evidence that TTP orchestrates the target destabilization via a hierarchical molecular assembly that culminates by the association of mature mRNA with the RNA degradation machinery in the cytoplasm. The early fate decision in the life cycle of a TTP target mRNA prevents the translation of inflammatory mediators, particularly cytokine mRNAs, and promotes efficient cessation of the immune response. Importantly, the TTP homolog ZFP36L1 displays similar characteristics, suggesting a conserved mode of action within the ZFP36 family of RBPs.
Project description:In order to examine the effects of bone marrow TTP deficiency on inflammation and lipid metabolism and determine the driving force during atherosclerosis, 8 week-old female LDLR−/− mice on C57BL/6J background were lethally irradiated and reconstituted with a wild type (TTP+/+) or TTP knockout (TTP−/−) bone marrow cells and fed a Western diet for 12 weeks. Then mice were sacrificed and tissues were collected for analysis. Liver tissues were collected and gene expression was analysed using a whole genome microarray. Bone marrow TTP−/− recipients displayed a significantly higher systemic and multi-organ inflammation compared to the BM-TTP+/+ recipients. BM-TTP−/− mice displayed a significant reduction of serum lipid levels, attenuated hepatic steatosis, and decreased lipid excretion than the control mice. microarray data showed that BM-TTP deficiency modulate liver genes involved in lipid metabolism and inflammatory response. RT-qPCR was used to confirm the results in several genes from microarray data. BM-TTP deficiency did not further accelerate atherorogenesis process in LDLR−/− mice after a Western diet feeding. TTP promoted VLDL to drive proinflammatory mechanism into proatherogenic mechanism.
Project description:we cloned and overexpressed human TTP-encoding gene ZFP36 in HeLa cell in the absence of inflammatory stimuli. The transcriptomes of the control and ZFP36-overexpression cells were sequenced and subjected to analysis and validation. Upon ZFP36 overexpression, expression of genes in innate immunity, including those in type I interferon signaling pathway and viral response, were specifically up-regulated, implying a transcriptional regulatory mechanism associated with the predicted DNA binding activity of TTP. TTP preferentially regulates the alternative splicing of genes involved in positive regulation of I-B/NF-B cascade and TRIF-dependent toll-like receptor signaling pathway, MAPK signaling pathway, TNF signaling pathway and T cell receptor signaling pathways.Our study indicates that TTP may regulates immune response via alternative splicing regulation and possibly by transcriptional regulation as well, which greatly expands the current understanding of the central role of TTP in regulating immune response and tumorigenesis.
Project description:Tristetraprolin (TTP), encoded by Zfp36 in mice, is one of the best characterized tandem zinc-finger mRNA binding protein involved in mRNA deadenylation and decay. TTPΔARE mice lack an AU-rich motif in the 3’ untranslated regions of TTP mRNA leading to increased TTP mRNA stability and more TTP protein, resulting in elevated mRNA decay rates of TTP targets. We examined the effect of TTP overexpression on the hematopoietic system and found alterations in red blood cell and white blood cell frequencies, with loss of platelets and B220 cells and gains of eosinophils and T-cells. TTPΔARE mice also have skewed primitive populations in the bone marrow with increases in myeloid-biased HSCs, but loss of granulocyte/macrophage biased MPP3 in both young and mid-aged mice. These populations changes were associated with cell-specific transcriptional alterations, but surprisingly consistent upregulation of TNF and TGFB signaling pathways in both progenitor populations. HSCs with overexpression of TTP had decreased reconstitution potential but generate hematopoietic environments that mitigate the inflammatory response induced by collagen antibody-induced arthritis (CAIA) model- even when TTP overexpressing cells are present at low frequencies. We present an overall analysis of elevated TTP expression in the early hematopoietic compartments which drives reduced overall reconstitution potential of the HSCs but leads to a dominant repression of inflammation induced in a rheumatoid arthritis model.