Hepatocyte-macrophage crosstalk via the PGRN-EGFR axis modulates ADAR1-mediated immunity in the liver -Spatial Transcriptomics
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ABSTRACT: ADAR1 is thought to be an immune suppressor maintaining self-tolerance to endogenous nucleic acids. Lack of ADAR1 results in MDA5 (Ifih1) activation and MDA5 deletion rescues ADAR1 null embryonic lethality. We generated liver specific ADAR1; MDA5 double KO mice and performed high throughput sequencing to investigate hepatic inflammation in these mice. Spatial transcriptomics (Visium, 10x Genomics) was performed on FFPE mice liver tissues. Constructed libraries were sequenced on the Novaseq 6000 platform. Over 250 million pairs of mappable reads for each sample were obtained.
Project description:ADAR1 is thought to be an immune suppressor maintaining self-tolerance to endogenous nucleic acids. Lack of ADAR1 results in MDA5 (Ifih1) activation and MDA5 deletion rescues ADAR1 null embryonic lethality. We generated liver specific ADAR1; MDA5 double KO mice and performed high throughput sequencing to investigate hepatic inflammation in these mice. Bulk RNA was sequenced on the HiSeq X platform. Over 100 million pairs of mappable reads for each sample were obtained.
Project description:ADAR1 is thought to be an immune suppressor maintaining self-tolerance to endogenous nucleic acids. Lack of ADAR1 results in MDA5 (Ifih1) activation and MDA5 deletion rescues ADAR1 null embryonic lethality. We generated liver specific ADAR1; MDA5 double KO mice and performed high throughput sequencing to investigate hepatic inflammation in these mice. Single cell RNA sequencing was performed on cells isolated from mice livers. Constructed libraries were sequenced on the HiSeq X platform. Over 100 million pairs of mappable reads for each sample were obtained.
Project description:ADAR1 is thought to be an immune suppressor maintaining self-tolerance to endogenous nucleic acids. ADAR1 is often overexpressed in hepatocellular carcinoma tumors, and might contribute to immunosuppression and immune evasion of cancer cells. We performed single cell RNA sequencing on non-tumor and tumor HCC samples. Constructed libraries were sequenced on the HiSeq X platform. Over 150 million pairs of mappable reads for each sample were obtained.
Project description:Adenosine deaminases acting on RNA (Adar1 and Adar2) catalyze I-to-A RNA editing, a post-transcriptional mechanism involved in multiple cellular functions. The role of Adar1-dependent RNA editing in cardiomyocytes (CMs) remains unclear. Here we show that conditional deletion of Adar1 in CMs results in myocarditis progressively evolving into dilated cardiomyopathy and heart failure at only 6 months of age. Adar1 depletion drives activation of interferon signaling genes (ISGs) in the absence of apoptosis and cytokine activation, and reduces the hypertrophic response of CMs upon pressure overload. Interestingly, ablation of the cytosolic sensor MDA5 prevents cardiac ISG activation and delays disease onset, but does not rescue the long-term lethal phenotype elicited by conditional deletion of Adar1. Retention of a single catalytically inactive Adar1 allele in CMs, in combination with MDA5 depletion, however, completely restores the cardiac function and prevents heart failure. Finally, ablation of interferon regulatory factor 7 (Irf7) attenuates the phenotype of Adar1-deficient CMs to a similar extent as MDA5 depletion, highlighting Irf7 as the main regulator of the immune response triggered by lack of Adar1 in CMs.
Project description:The antiviral defense in vertebrates requires the innate immune system to sense foreign “non-self” nucleic acids while avoiding “self” nucleic acids, which is accomplished by an intricate system. Cellular double-stranded RNAs (dsRNAs) are edited by the RNA editing enzyme ADAR1 to prevent their dsRNA structure pattern from being recognized as viral dsRNA. Lack of RNA editing by ADAR1 enables activation of MDA5, a cytosolic dsRNA sensor, by cellular dsRNA. Additional RNA editing- independent functions of ADAR1 have been proposed, but the specific mechanism remains elusive. Here we demonstrate that RNA binding by ADAR1, independent of its editing activity, restricts the activation of PKR, another cytosolic dsRNA sensor, by cellular dsRNA. Mechanistically, the loss of ADAR1 editing caused MDA5 activation to induce interferon signaling, while a lack of ADAR1 protein or its dsRNA binding ability led to PKR activation, with subsequent stress granule formation and proliferation arrest. Based on these findings we rescued the Adar1−/− mice from embryonic lethality to adulthood by deleting both MDA5 and PKR, in contrast to the limited rescue of Adar1−/− mice by removing MDA5 or PKR alone. Our findings reveal a multifaceted contribution of ADAR1 in regulating the immunogenicity of “self” dsRNAs. Furthermore, ADAR1 is an immuno-oncology target for drug development, and the separation of ADAR1’s RNA editing and binding functions provides mechanistic insights for such developments.
Project description:Adenosine-to-Inosine (A-to-I) editing of dsRNA by ADAR proteins is a pervasive feature of the epitranscriptome. There are estimated to be over 100 million potential A-to-I editing sites in humans and A-to-I editing can have varying consequences for gene expression. Whilst editing resulting in protein recoding defines the role of ADAR2, ADAR1 has been proposed to have both editing-dependent and -independent functions. The relative contribution of these putative functions to ADAR1 biology is unclear. We demonstrate that the absence of ADAR1-mediated editing is well tolerated when the cytosolic dsRNA sensor MDA5 is deleted. These mice have normal hematopoiesis, tissue patterning and life span. A direct comparison of the complete deletion of ADAR1 and the specific loss of A-to-I editing activity demonstrates that RNA editing is the only essential function of ADAR1 in adult mice. Therefore, preventing MDA5 substrate formation by endogenous RNA is the essential in vivo function of ADAR1-mediated editing.
Project description:Adenosine-to-Inosine (A-to-I) editing of dsRNA by ADAR proteins is a pervasive feature of the epitranscriptome. There are estimated to be over 100 million potential A-to-I editing sites in humans and A-to-I editing can have varying consequences for gene expression. Whilst editing resulting in protein recoding defines the role of ADAR2, ADAR1 has been proposed to have both editing-dependent and -independent functions. The relative contribution of these putative functions to ADAR1 biology is unclear. We demonstrate that the absence of ADAR1-mediated editing is well tolerated when the cytosolic dsRNA sensor MDA5 is deleted. These mice have normal hematopoiesis, tissue patterning and life span. A direct comparison of the complete deletion of ADAR1 and the specific loss of A-to-I editing activity demonstrates that RNA editing is the only essential function of ADAR1 in adult mice. Therefore, preventing MDA5 substrate formation by endogenous RNA is the essential in vivo function of ADAR1-mediated editing.
Project description:Adenosine-to-Inosine (A-to-I) editing of dsRNA by ADAR proteins is a pervasive feature of the epitranscriptome. There are estimated to be over 100 million potential A-to-I editing sites in humans and A-to-I editing can have varying consequences for gene expression. Whilst editing resulting in protein recoding defines the role of ADAR2, ADAR1 has been proposed to have both editing-dependent and -independent functions. The relative contribution of these putative functions to ADAR1 biology is unclear. We demonstrate that the absence of ADAR1-mediated editing is well tolerated when the cytosolic dsRNA sensor MDA5 is deleted. These mice have normal hematopoiesis, tissue patterning and life span. A direct comparison of the complete deletion of ADAR1 and the specific loss of A-to-I editing activity demonstrates that RNA editing is the only essential function of ADAR1 in adult mice. Therefore, preventing MDA5 substrate formation by endogenous RNA is the essential in vivo function of ADAR1-mediated editing.
Project description:Leukemia initiating cells (LICs) are regarded as the origin of leukemia relapse and therapeutic resistance. Identifying direct stemness determinants that fuel LIC self-renewal is critical for developing targeted approaches to eliminate LICs and prevent relapse. Here, we show that the RNA editing enzyme ADAR1 is a crucial stemness factor that promotes LIC self-renewal by attenuating aberrant double-stranded RNA (dsRNA) sensing. Elevated adenosine-to-inosine (A-to-I) editing is a common attribute of relapsed T-ALL regardless of molecular subtypes. Consequently, knockdown of ADAR1 severely inhibits LIC self-renewal capacity and prolongs survival in T-ALL PDX models. Mechanistically, ADAR1 directs hyper-editing of immunogenic dsRNA to avoid detection by the innate immune sensor MDA5. Moreover, we uncovered that the cell intrinsic level of MDA5 dictates the dependency on ADAR1-MDA5 axis in T-ALL. Collectively, our results show that ADAR1 functions as a self-renewal factor that limits the sensing of endogenous dsRNA. Thus, targeting ADAR1 presents an effective therapeutic strategy for eliminating T-ALL LICs.
Project description:In this study we show that intronic and intergenic SINE elements, specifically inverted repeats (IR) Alus, are the major source of drug-induced immunogenic dsRNA. These IR-Alus are frequently located downstream of ‘orphan’ CpG Islands (CGIs). In mammals, the enzyme Adenosine Deaminases Acting on RNA (ADAR1) targets and destabilizes IR-Alu dsRNA, which prevents activation of MDA5. We found that ADAR1 establishes a negative feedback loop, restricting the viral mimicry response to epigenetic therapy. Depletion of ADAR1 in patient-derived cancer cells potentiates the efficacy of epigenetic therapy, restraining tumour growth and reducing cancer initiation. Thus, epigenetic therapies trigger viral mimicry by inducing a subset of IR-Alus, leading to an ADAR1 dependency. Our findings suggest that combining epigenetic therapies with ADAR1 inhibitors represents a promising new strategy for cancer treatment.