ORCID Profile
0000-0002-4784-9031
Current Organisation
St Vincent's Institute of Medical Research
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Medical Biochemistry and Metabolomics | Medical Biochemistry: Nucleic Acids | Innate Immunity
Expanding Knowledge in the Biological Sciences | Expanding Knowledge in the Medical and Health Sciences |
Publisher: Cold Spring Harbor Laboratory
Date: 26-06-2022
DOI: 10.1101/2022.06.24.497437
Abstract: ADAR1 mediated A-to-I RNA editing is a self/non-self discrimination mechanism for cellular double stranded RNAs. ADAR mutations are one cause of Aicardi-Goutières Syndrome, an inherited paediatric encephalopathy, broadly classed as a “Type I interferonopathy”. The most common ADAR1 mutation is a proline 193 alanine (p.P193A) mutation, mapping to the ADAR1p150 isoform specific Zα domain. We report the development of an independent murine P195A knock-in mouse, homologous to the human P193A mutation. The Adar1 P195A/P195A mice are largely normal and the mutation is well tolerated. Contrasting with previous reports when the P195A mutation was compounded with an ADAR1 null allele, the majority of mice have only a modest reduction in weaning weight and survived long-term. Severe runting and shortened survival of Adar1 P195A/- animals are dependent on the parental genotype. The P195A mutation is well tolerated in vivo and the loss of MDA5 is sufficient to completely rescue the Adar1 P195A/- mice.
Publisher: Elsevier BV
Date: 08-2014
Publisher: Cold Spring Harbor Laboratory
Date: 25-01-2023
DOI: 10.1101/2023.01.25.525475
Abstract: Effective immunity requires the innate immune system to distinguish foreign (non-self) nucleic acids from cellular (self) nucleic acids. Cellular double-stranded RNAs (dsRNAs) are edited by the RNA editing enzyme ADAR1 to prevent their dsRNA structure pattern being recognized as viral dsRNA by cytoplasmic dsRNA sensors including MDA5, PKR and ZBP1. A loss of ADAR1-mediated RNA editing of cellular dsRNA activates MDA5. However, additional RNA editing-independent functions of ADAR1 have been proposed, but a specific mechanism has not been delineated. We now demonstrate that the loss of ADAR1-mediated RNA editing specifically activates MDA5, while loss of the cytoplasmic ADAR1p150 isoform or its dsRNA binding activity enabled PKR activation. Deleting both MDA5 and PKR resulted in complete rescue of the embryonic lethality of Adar1p150 -/- mice to adulthood, contrasting with the limited or no rescue by removing MDA5, PKR or ZBP1 alone, demonstrating that this is a species conserved function of ADAR1p150. Our findings demonstrate that MDA5 and PKR are the primary in vivo effectors of fatal autoinflammation following the loss of ADAR1p150.
Publisher: Springer Science and Business Media LLC
Date: 21-07-2015
DOI: 10.1038/ONC.2014.217
Abstract: Osteosarcoma (OS) is the most common cancer of bone. Parathyroid hormone (PTH) regulates calcium homeostasis and bone development, while the paracrine/autocrine PTH-related protein (PTHrP) has central roles in endochondral bone formation and bone remodeling. Using a murine OS model, we found that OS cells express PTHrP and the common PTH/PTHrP receptor (PTHR1). To investigate the role of PTHR1 signaling in OS cell behavior, we used shRNA to reduce PTHR1 expression. This only mildly inhibited proliferation in vitro, but markedly reduced invasion through collagen and reduced expression of RANK ligand (RANKL). Administration of PTH(1-34) did not stimulate OS proliferation in vivo but, strikingly, PTHR1 knockdown resulted in a profound growth inhibition and increased differentiation/mineralization of the tumors. Treatment with neutralizing antibody to PTHrP did not recapitulate the knockdown of PTHR1. Consistent with this lack of activity, PTHrP was predominantly intracellular in OS cells. Knockdown of PTHR1 resulted in increased expression of late osteoblast differentiation genes and upregulation of Wnt antagonists. RANKL production was reduced in knockdown tumors, providing for reduced homotypic signaling through the receptor, RANK. Loss of PTHR1 resulted in the coordinated loss of gene signatures associated with the polycomb repressive complex 2 (PRC2). Using Ezh2 inhibitors, we demonstrate that the increased expression of osteoblast maturation markers is in part mediated by the loss of PRC2 activity. Collectively these results demonstrate that PTHR1 signaling is important in maintaining OS proliferation and undifferentiated state. This is in part mediated by intracellular PTHrP and through regulation of the OS epigenome.
Publisher: Public Library of Science (PLoS)
Date: 05-07-2019
Publisher: Elsevier BV
Date: 02-2019
DOI: 10.1016/J.EXPHEM.2018.11.001
Abstract: Myelodysplastic syndromes (MDS) and related myelodysplastic/myeloproliferative neoplasms (MDS/MPNs) are clonal stem cell disorders, primarily affecting patients over 65 years of age. Mapping of the MDS and MDS/MPN genome identified recurrent heterozygous mutations in the RNA splicing machinery, with the SF3B1, SRSF2, and U2AF1 genes being frequently mutated. To better understand how spliceosomal mutations contribute to MDS pathogenesis in vivo, numerous groups have sought to establish conditional murine models of SF3B1, SRSF2, and U2AF1 mutations. The high degree of conservation of hematopoiesis between mice and human and the well-established phenotyping and genetic modification approaches make murine models an effective tool with which to study how a gene mutation contributes to disease pathogenesis. The murine models of spliceosomal mutations described to date recapitulate human MDS or MDS/MPN to varying extents. Reasons for the differences in phenotypes reported between alleles of the same mutation are varied, but the nature of the genetic modification itself and subsequent analysis methods are important to consider. In this review, we summarize recently reported murine models of SF3B1, SRSF2, and U2AF1 mutations, with a particular focus on the genetically engineered modifications underlying the models and the experimental approaches applied.
Publisher: Cold Spring Harbor Laboratory
Date: 15-06-2008
DOI: 10.1101/GAD.1656808
Abstract: Osteosarcoma is the most common primary malignant tumor of bone. Analysis of familial cancer syndromes and sporadic cases has strongly implicated both p53 and pRb in its pathogenesis however, the relative contribution of these mutations to the initiation of osteosarcoma is unclear. We describe here the generation and characterization of a genetically engineered mouse model in which all animals develop short latency malignant osteosarcoma. The genetically engineered mouse model is based on osteoblast-restricted deletion of p53 and pRb . Osteosarcoma development is dependent on loss of p53 and potentiated by loss of pRb, revealing a dominance of p53 mutation in the development of osteosarcoma. The model reproduces many of the defining features of human osteosarcoma including cytogenetic complexity and comparable gene expression signatures, histology, and metastatic behavior. Using a novel in silico methodology termed cytogenetic region enrichment analysis, we demonstrate high conservation of gene expression changes between murine osteosarcoma and known cytogentically rearranged loci from human osteosarcoma. Due to the strong similarity between murine osteosarcoma and human osteosarcoma in this model, this should provide a valuable platform for addressing the molecular genetics of osteosarcoma and for developing novel therapeutic strategies.
Publisher: American Society for Clinical Investigation
Date: 24-06-2014
DOI: 10.1172/JCI75334
Publisher: Springer Science and Business Media LLC
Date: 07-12-2008
DOI: 10.1038/NI.1680
Publisher: Springer Science and Business Media LLC
Date: 06-2007
DOI: 10.1038/NATURE05883
Publisher: Springer Science and Business Media LLC
Date: 04-04-2016
DOI: 10.1038/ONC.2016.68
Abstract: Osteosarcoma (OS) is the most common cancer of bone and the 5th leading cause of cancer-related death in young adults. Currently, 5-year survival rates have plateaued at ~70% for patients with localized disease. Those with disseminated disease have an ~20% 5-year survival. An improved understanding of the molecular genetics of OS may yield new approaches to improve outcomes for OS patients. To this end, we applied murine models that replicate human OS to identify and understand dysregulated microRNAs (miRNAs) in OS. miRNA expression patterns were profiled in murine primary osteoblasts, osteoblast cultures and primary OS cell cultures (from primary and paired metastatic locations) isolated from two genetically engineered murine models of OS. The differentially expressed miRNA were further assessed by a cross-species comparison with human osteoblasts and OS cultures. We identified miR-155-5p and miR-148a-3p as deregulated in OS. miR-155-5p suppression or miR-148a-3p overexpression potently reduced proliferation and induced apoptosis in OS cells, yet strikingly, did not impact normal osteoblasts. To define how these miRNAs regulated OS cell fate, we used an integrated computational approach to identify putative candidate targets and then correlated these with the cell biological impact. Although we could not resolve the mechanism through which miR-148a-3p impacts OS, we identified that miR-155-5p overexpression suppressed its target Ripk1 (receptor (TNFRSF)-interacting serine-threonine kinase 1) expression, and miR-155-5p inhibition elevated Ripk1 levels. Ripk1 is directly involved in apoptosis/necroptosis. In OS cells, small interfering RNA against Ripk1 prevented cell death induced by the sequestration of miR-155-5p. Collectively, we show that miR-148a-3p and miR-155-5p are species-conserved deregulated miRNA in OS. Modulation of these miRNAs was specifically toxic to tumor cells but not normal osteoblasts, raising the possibility that these may be tractable targets for miRNA-based therapies for OS.
Publisher: Springer Science and Business Media LLC
Date: 06-05-2015
DOI: 10.1038/SREP10120
Abstract: Osteosarcoma (OS) survival rates have plateaued in part due to a lack of new therapeutic options. Here we demonstrate that bromodomain inhibitors (BETi), JQ1, I-BET151, I-BET762, exert potent anti-tumour activity against primary and established OS cell lines, mediated by inhibition of BRD4. Strikingly, unlike previous observations in long-term established human OS cell lines, the antiproliferative activity of JQ1 in primary OS cells was driven by the induction of apoptosis, not cell cycle arrest. In further contrast, JQ1 activity in OS was mediated independently of MYC downregulation. We identified that JQ1 suppresses the transcription factor FOSL1 by displacement of BRD4 from its locus. Loss of FOSL1 phenocopied the antiproliferative effects of JQ1, identifying FOSL1 suppression as a potential novel therapeutic approach for OS. As a monotherapy JQ1 demonstrated significant anti-tumour activity in vivo in an OS graft model. Further, combinatorial treatment approaches showed that JQ1 increased the sensitivity of OS cells to doxorubicin and induced potent synergistic activity when rationally combined with CDK inhibitors. The greater level of activity achieved with the combination of BETi with CDK inhibitors demonstrates the efficacy of this combination therapy. Taken together, our studies show that BET inhibitors are a promising new therapeutic for OS.
Publisher: Springer Science and Business Media LLC
Date: 12-2019
DOI: 10.1186/S13059-019-1873-2
Abstract: Adenosine-to-inosine (A-to-I) RNA editing, mediated by ADAR1 and ADAR2, occurs at tens of thousands to millions of sites across mammalian transcriptomes. A-to-I editing can change the protein coding potential of a transcript and alter RNA splicing, miRNA biology, RNA secondary structure and formation of other RNA species. In vivo, the editing-dependent protein recoding of GRIA2 is the essential function of ADAR2, while ADAR1 editing prevents innate immune sensing of endogenous RNAs by MDA5 in both human and mouse. However, a significant proportion of A-to-I editing sites can be edited by both ADAR1 and ADAR2, particularly within the brain where both are highly expressed. The physiological function(s) of these shared sites, including those evolutionarily conserved, is largely unknown. To generate completely A-to-I editing-deficient mammals, we crossed the viable rescued ADAR1-editing-deficient animals ( Adar1 E861A/E861A Ifih1 −/− ) with rescued ADAR2-deficient ( Adarb1 −/− Gria2 R/R ) animals. Unexpectedly, the global absence of editing was well tolerated. Adar1 E861A/E861A Ifih1 −/− Adarb1 −/− Gria2 R/R were recovered at Mendelian ratios and age normally. Detailed transcriptome analysis demonstrated that editing was absent in the brains of the compound mutants and that ADAR1 and ADAR2 have similar editing site preferences and patterns. We conclude that ADAR1 and ADAR2 are non-redundant and do not compensate for each other’s essential functions in vivo. Physiologically essential A-to-I editing comprises a small subset of the editome, and the majority of editing is dispensable for mammalian homeostasis. Moreover, in vivo biologically essential protein recoding mediated by A-to-I editing is an exception in mammals.
Publisher: Springer Science and Business Media LLC
Date: 05-2009
DOI: 10.1038/NI0509-551A
Publisher: Elsevier BV
Date: 08-2020
Publisher: Elsevier BV
Date: 07-2013
Publisher: American Society of Hematology
Date: 09-08-2018
DOI: 10.1182/BLOOD-2018-04-845602
Abstract: Srsf2 P95H/+ mutation within hemopoietic stem cells is required to initiate myeloid-biased hemopoiesis. Mutation of Srsf2 is sufficient to initiate the development of MDS/MPN in vivo in the setting of native hemopoiesis.
Publisher: Ferrata Storti Foundation (Haematologica)
Date: 14-12-2012
Publisher: Elsevier
Date: 2015
Publisher: Public Library of Science (PLoS)
Date: 17-01-2017
Publisher: Cold Spring Harbor Laboratory
Date: 24-04-2023
DOI: 10.1101/2023.04.24.538176
Abstract: The homeobox gene, Hoxa1 , has two different isoforms generated by alternative splicing: a full-length homeodomain-containing Hoxa1 ( Hoxa1-FL ), and a truncated Hoxa1 ( Hoxa1-T ), that lacks the homeodomain. Oncoretroviral overexpression of wildtype Hoxa1 cDNA ( WT-Hoxa1 ), which generates both Hoxa1 isoforms, in murine hematopoietic stem and progenitor cells (HSPCs) perturbed hematopoiesis, resulting in myelodysplastic syndromes (MDS) in mice. Overexpression of a mutated Hoxa1 cDNA ( MUT-Hoxa1 ) that generates Hoxa1-FL but not Hoxa1-T led to a more severe MDS capable of transforming to secondary acute myeloid leukemia (sAML). Similar to human MDS, DNA damage repair pathways were downregulated in Hoxa1 -overexpressing hematopoietic progenitor cells. Conditional knock-in mouse models revealed a Hoxa1-FL dosage-dependent effect on MDS disease severity. Our data reveal that increased expression of Hoxa1-FL in HSPCs is sufficient to initiate MDS in mice. CD34+ cells from up to 50% of patients with MDS had elevated HOXA1-FL expression, highlighting the clinical relevance of our mouse models. Our study demonstrates that Hoxa1 is a key regulator of HSPCs and that increased expression of the transcriptionally active Hoxa1-FL can initiate MDS in mice. Furthermore, HOXA1-FL expression is upregulated in a significant proportion of human MDS patients and likely contributes to the disease in these patients.
Publisher: Springer Science and Business Media LLC
Date: 07-05-2019
DOI: 10.1038/S41598-019-43373-6
Abstract: Deletion of long arm of chromosome 20 [del(20q)] is the second most frequent recurrent chromosomal abnormality in hematological malignancies. It is detected in 10% of myeloproliferative neoplasms, 4–5% of myelodysplastic syndromes, and 1–2% of acute myeloid leukaemia. Recurrent, non-random occurrence of del(20q) indicates that it is a pathogenic driver in myeloid malignancies. Genetic mapping of patient s les has identified two regions of interest on 20q – the “Common Deleted Region” (CDR) and “Common Retained Region” (CRR), which was often lified. We proposed that the CDR contained tumor suppressor gene(s) (TSG) and the CRR harbored oncogene(s) loss of a TSG together with over-expression of an oncogene favored development of myeloid malignancies. Protein Tyrosine Phosphatase Receptor T (PTPRT) and Hemopoietic cell kinase (HCK) were identified to be the likely candidate TSG and oncogene respectively. Retroviral transduction of HCK into PTPRT-null murine LKS+ stem and progenitor cells resulted in hyperproliferation in colony forming assays and hyperphosphorylation of intracellular STAT3. Furthermore, over half of the murine recipients of these transduced cells developed erythroid hyperplasia, polycythemia and splenomegaly at 12 months, although no leukemic phenotype was observed. The findings suggested that HCK lification coupled with PTPRT loss in del(20q) leads to development of a myeloproliferative phenotype.
Publisher: Wiley
Date: 27-02-2017
DOI: 10.1002/JCB.26601
Abstract: Osteosarcoma (OS) is the most common cancer of bone in children and young adults. Despite extensive research efforts, there has been no significant improvement in patient outcome for many years. An improved understanding of the biology of this cancer and how genes frequently mutated contribute to OS may help improve outcomes for patients. While our knowledge of the mutational burden of OS is approaching saturation, our understanding of how these mutations contribute to OS initiation and maintenance is less clear. Murine models of OS have now been demonstrated to be highly valid recapitulations of human OS. These models were originally based on the frequent disruption of p53 and Rb in familial OS syndromes, which are also common mutations in sporadic OS. They have been applied to significantly improve our understanding about the functions of recurrently mutated genes in disease. The murine models can be used as a platform for preclinical testing and identifying new therapeutic targets, in addition to testing the role of additional mutations in vivo. Most recently these models have begun to be used for discovery based approaches and screens, which hold significant promise in furthering our understanding of the genetic and therapeutic sensitivities of OS. In this review, we discuss the mouse models of OS that have been reported in the last 3‐5 years and newly identified pathways from these studies. Finally, we discuss the preclinical utilization of the mouse models of OS for identifying and validating actionable targets to improve patient outcome.
Publisher: Informa UK Limited
Date: 08-12-2014
Publisher: Elsevier BV
Date: 07-2013
DOI: 10.1016/J.BONE.2013.02.016
Abstract: Osteosarcoma is the most common primary cancer of bone and one that predominantly affects children and adolescents. Osteoblastic osteosarcoma represents the major subtype of this tumor, with approximately equal representation of fibroblastic and chondroblastic subtypes. We and others have previously described murine models of osteosarcoma based on osteoblast-restricted Cre:lox deletion of Trp53 (p53) and Rb1 (Rb), resulting in a phenotype most similar to fibroblastic osteosarcoma in humans. We now report a model of the most prevalent form of human osteosarcoma, the osteoblastic subtype. In contrast to other osteosarcoma models that have used Cre:lox mediated gene deletion, this model was generated through shRNA-based knockdown of p53. As is the case with the human disease the shRNA tumors most frequently present in the long bones and preferentially disseminate to the lungs feature less consistently modeled using Cre:lox approaches. Our approach allowed direct comparison of the in vivo consequences of targeting the same genetic drivers using two different technologies, Cre:lox and shRNA. This demonstrated that the effects of Cre:lox and shRNA mediated knock-down are qualitatively different, at least in the context of osteosarcoma, and yielded distinct subtypes of osteosarcoma. Through the use of complementary genetic modification strategies we have established a model of the most common clinical subtype of osteosarcoma that was not previously represented and more fully recapitulated the clinical spectrum of this cancer.
Publisher: Springer Science and Business Media LLC
Date: 15-06-2020
DOI: 10.1038/S41467-020-16840-2
Abstract: The caudal-related homeobox transcription factor CDX2 is expressed in leukemic cells but not during normal blood formation. Retroviral overexpression of Cdx2 induces AML in mice, however the developmental stage at which CDX2 exerts its effect is unknown. We developed a conditionally inducible Cdx2 mouse model to determine the effects of in vivo, inducible Cdx2 expression in hematopoietic stem and progenitor cells (HSPCs). Cdx2-transgenic mice develop myelodysplastic syndrome with progression to acute leukemia associated with acquisition of additional driver mutations. Cdx2-expressing HSPCs demonstrate enrichment of hematopoietic-specific enhancers associated with pro-differentiation transcription factors. Furthermore, treatment of Cdx2 AML with azacitidine decreases leukemic burden. Extended scheduling of low-dose azacitidine shows greater efficacy in comparison to intermittent higher-dose azacitidine, linked to more specific epigenetic modulation. Conditional Cdx2 expression in HSPCs is an inducible model of de novo leukemic transformation and can be used to optimize treatment in high-risk AML.
Publisher: Informa UK Limited
Date: 03-2021
DOI: 10.1128/MCB.00590-20
Publisher: Elsevier BV
Date: 06-2007
Publisher: Springer Science and Business Media LLC
Date: 12-01-2015
DOI: 10.1038/LEU.2015.8
Publisher: American Society of Hematology
Date: 15-02-2004
DOI: 10.1182/BLOOD-2003-07-2391
Abstract: Retinoids are potent inducers of cell cycle arrest and differentiation of numerous cell types, notably granulocytes. However the mechanisms by which retinoids mediate cell cycle arrest during differentiation remain unclear. We have used myeloid differentiation to characterize the molecular pathways that couple cell cycle withdrawal to terminal differentiation. Using primary cells from mice deficient for either the cyclin-dependent kinase inhibitor (CDKi) p27Kip1, the Myc antagonist Mad1, or both Mad1 and p27Kip1, we observed that signals mediated through retinoic acid receptor α (RARα), but not RARβ or γ, required both Mad1 and p27Kip1 to induce cell cycle arrest and to accelerate terminal differentiation of granulocytes. Although RARα did not directly regulate Mad1 or p27Kip1, the RARα target gene C/EBPϵ directly regulated transcription of Mad1. Induction of C/EBPϵ activity in granulocytic cells led to rapid induction of Mad1 protein and transcript, with direct binding of C/EBPϵ to the Mad1 promoter demonstrated through chromatin immunoprecipitation assay. These data demonstrate that cell cycle arrest in response to RARα specifically requires Mad1 and p27Kip1 and that Mad1 is transcriptionally activated by CCAAT/enhancer-binding protein ϵ (C/EBPϵ). Moreover, these data demonstrate selectivity among the RARs for cell cycle arrest pathways and provide a direct mechanism to link differentiation induction and regulation of the Myc antagonist Mad1.
Publisher: Springer Science and Business Media LLC
Date: 21-10-2015
DOI: 10.1038/SREP15529
Abstract: The gp130 receptor and its binding partners play a central role in cytokine signalling. Ciliary neurotrophic factor (CNTF) is one of the cytokines that signals through the gp130 receptor complex. CNTF has previously been shown to be a negative regulator of trabecular bone remodelling and important for motor neuron development. Since haematopoietic cell maintenance and differentiation is dependent on the bone marrow (BM) microenvironment, where cells of the osteoblastic lineage are important regulators, we hypothesised that CNTF may also have important roles in regulating haematopoiesis. Analysis of haematopoietic parameters in male and female Cntf −/− mice at 12 and 24 weeks of age revealed altered B lymphopoiesis. Strikingly, the B lymphocyte phenotype differed based on sex, age and also the BM microenvironment in which the B cells develop. When BM cells from wildtype mice were transplanted into Cntf −/− mice, there were minimal effects on B lymphopoiesis or bone parameters. However, when Cntf −/− BM cells were transplanted into a wildtype BM microenvironment, there were changes in both haematopoiesis and bone parameters. Our data reveal that haematopoietic cell-derived CNTF has roles in regulating BM B cell lymphopoiesis and both trabecular and cortical bone, the latter in a sex-dependent manner.
Publisher: Elsevier BV
Date: 06-2011
Publisher: Informa UK Limited
Date: 21-01-2015
DOI: 10.3109/10428194.2014.907897
Abstract: The Src family protein tyrosine kinases (SFKs) are non-receptor intracellular kinases that have important roles in both hematopoiesis and leukemogenesis. The derangement of their expression or activation has been demonstrated to contribute to hematological malignancies. This review first examines the mechanisms of SFK overexpression and hyperactivation, emphasizing the dysregulation of the upstream modulators. Subsequently, the role of SFK up-regulation in the initiation, progression and therapy resistance of many hematological malignancies is also analyzed. The presented evidence endeavors to highlight the influence of SFK up-regulation on an extensive number of hematological malignancies and the need to consider them as candidates in targeted anticancer therapy.
Publisher: Wiley
Date: 21-12-2015
DOI: 10.1002/WRNA.1322
Abstract: The conversion of genomically encoded adenosine to inosine in dsRNA is termed as A‐to‐I RNA editing. This process is catalyzed by two of the three mammalian ADAR proteins ( ADAR1 and ADAR2 ) both of which have essential functions for normal organismal homeostasis. The phenotype of ADAR2 deficiency can be primarily ascribed to a lack of site‐selective editing of a single transcript in the brain. In contrast, the biology and substrates responsible for the Adar1 −/− phenotype have remained more elusive. Several recent studies have identified that a feature of absence or reductions of ADAR1 activity, conserved across human and mouse models, is a profound activation of interferon‐stimulated gene signatures and innate immune responses. Further analysis of this observation has lead to the conclusion that editing by ADAR1 is required to prevent activation of the cytosolic innate immune system, primarily focused on the dsRNA sensor MDA5 and leading to downstream signaling via MAVS . The delineation of this mechanism places ADAR1 at the interface between the cells ability to differentiate self‐ from non‐self dsRNA . Based on MDA5 dsRNA recognition requisites, the mechanism indicates that the type of dsRNA must fulfil a particular structural characteristic, rather than a sequence‐specific requirement. While additional studies are required to molecularly verify the genetic model, the observations to date collectively identify A‐to‐I editing by ADAR1 as a key modifier of the cellular response to endogenous dsRNA . WIREs RNA 2016, 7:157–172. doi: 10.1002/wrna.1322 This article is categorized under: RNA Processing RNA Editing and Modification
Publisher: Springer Science and Business Media LLC
Date: 30-08-2002
Abstract: The role/s of retinoids in granulopoiesis has been recognised for many years, being powerful differentiation inducers. The physiological role/s of retinoic acid receptor (RAR)-mediated signalling during adult haemopoiesis has by contrast proved more elusive. The recent generation of highly specific pan-RAR antagonists has now made possible an assessment of the specific physiological role/s of RAR signalling, allowing the separation for the first time of the RAR and RXR pathways. Mice were treated with AGN194310, a synthetic retinoid that antagonises the physiological function of the three RAR isotypes (alpha, beta, gamma) but does not interact with RXRs. Analyses of the granulocytic lineage using Gr-1, c-Kit and CD11b antibodies, demonstrated that granulocyte numbers were strikingly increased across haemopoietic compartments in all AGN194310-treated mice. A significant increase in the frequency of progenitor cells containing granulocytes was observed in the bone marrow of mice following treatment with AGN194310. In contrast we were not able to detect any differences in cell death of either mature granulocytes or granulocytic progenitors from AGN194310-treated mice compared with control animals. These data demonstrate an essential role for RAR signalling in regulating the numbers of granulocytic precursors in vivo.
Publisher: Elsevier BV
Date: 10-2023
Publisher: Elsevier BV
Date: 12-2016
DOI: 10.1016/J.BONE.2016.09.009
Abstract: The EphB receptor tyrosine kinase family and their ephrinB ligands have been implicated as mediators of skeletal development and bone homeostasis in humans, where mutations in ephrinB1 contribute to frontonasal dysplasia and coronal craniosynostosis. In mouse models, ephrinB1 has been shown to be a critical factor mediating osteoblast function. The present study examined the functional importance of ephrinB1 during endochondral ossification using the Cre recombination system with targeted deletion of ephrinB1 (EfnB1
Publisher: Springer Berlin Heidelberg
Date: 2011
DOI: 10.1007/82_2011_150
Abstract: RNA editing by deamination of adenosine to inosine (A-to-I editing) is a physiologically important posttranscriptional mechanism that can regulate expression of genes by modifying their transcripts. A-to-I editing is mediated by adenosine deaminases acting on RNA (ADAR) that can catalytically exchange adenosines to inosines, with varying efficiency, depending on the structure of the RNA substrates. Significant progress in understanding the biological function of mammalian ADARs has been made in the past decade by the creation and analysis of gene-targeted mice with disrupted or modified ADAR alleles. These studies have revealed important roles of ADARs in neuronal and hematopoietic tissue during embryonic and postnatal stages of mouse development.
Publisher: American Society of Hematology
Date: 30-03-2022
DOI: 10.1182/BLOODADVANCES.2021004571
Abstract: Current strategies to target RNA splicing mutant myeloid cancers proposes targeting the remaining splicing apparatus. This approach has only been modestly sensitizing and is also toxic to non-mutant-bearing wild-type cells. To explore potentially exploitable genetic interactions with spliceosome mutations, we combined data mining and functional screening for synthetic lethal interactions with an Srsf2P95H/+ mutation. Analysis of missplicing events in a series of both human and murine SRSF2P95H mutant s les across multiple myeloid diseases (acute myeloid leukemia, myelodysplastic syndromes, chronic myelomonocytic leukemia) was performed to identify conserved missplicing events. From this analysis, we identified that the cell-cycle and DNA repair pathways were overrepresented within the conserved misspliced transcript sets. In parallel, to functionally define pathways essential for survival and proliferation of Srsf2P95H/+ cells, we performed a genome-wide Clustered regularly interspaced short palindromic repeat loss-of-function screen using Hoxb8 immortalized R26-CreERki/+Srsf2P95H/+ and R26-CreERki/+Srsf2+/+ cell lines. We assessed loss of single guide RNA representation at 3 timepoints: immediately after Srsf2P95H/+ activation, and at 1 week and 2 weeks after Srsf2P95H/+ mutation. Pathway analysis demonstrated that the cell-cycle and DNA damage response pathways were among the top synthetic lethal pathways with Srsf2P95H/+ mutation. Based on the loss of guide RNAs targeting Cdk6, we identified that palbociclib, a CDK6 inhibitor, showed preferential sensitivity in Srsf2P95H/+ cell lines and in primary nonimmortalized lin−cKIT+Sca-1+ cells compared with wild-type controls. Our data strongly suggest that the cell-cycle and DNA damage response pathways are required for Srsf2P95H/+ cell survival, and that palbociclib could be an alternative therapeutic option for targeting SRSF2 mutant cancers.
Publisher: Springer Science and Business Media LLC
Date: 21-10-2022
DOI: 10.1038/S41375-022-01727-6
Abstract: Recurrent mutations in RNA splicing proteins and epigenetic regulators contribute to the development of myelodysplastic syndrome (MDS) and related myeloid neoplasms. In chronic myelomonocytic leukemia (CMML), SRSF2 mutations occur in ~50% of patients and TET2 mutations in ~60%. Clonal analysis indicates that either mutation can arise as the founder lesion. Based on human cancer genetics we crossed an inducible Srsf2
Publisher: American Dairy Science Association
Date: 04-2011
Abstract: The objective of the present study was to compare the enteric methane (CH4) emissions and milk production of spring-calving Holstein-Friesian cows offered either a grazed perennial ryegrass diet or a total mixed ration (TMR) diet for 10 wk in early lactation. Forty-eight spring-calving Holstein-Friesian dairy cows were randomly assigned to 1 of 2 nutritional treatments for 10 wk: 1) grass or 2) TMR. The grass group received an allocation of 17 kg of dry matter (DM) of grass per cow per day with a pre-grazing herbage mass of 1,492 kg of DM/ha. The TMR offered per cow per day was composed of maize silage (7.5 kg of DM), concentrate blend (8.6 kg of DM), grass silage (3.5 kg of DM), molasses (0.7 kg of DM), and straw (0.5 kg of DM). Daily CH4 emissions were determined via the emissions from ruminants using a calibrated tracer technique for 5 consecutive days during wk 4 and 10 of the study. Simultaneously, herbage dry matter intake (DMI) for the grass group was estimated using the n-alkane technique, whereas DMI for the TMR group was recorded using the Griffith Elder feeding system. Cows offered TMR had higher milk yield (29.5 vs. 21.1 kg/d), solids-corrected milk yield (27.7 vs. 20.1 kg/d), fat and protein (FP) yield (2.09 vs. 1.54 kg/d), bodyweight change (0.54 kg of gain/d vs. 0.37 kg of loss/d), and body condition score change (0.36 unit gain vs. 0.33 unit loss) than did the grass group over the course of the 10-wk study. Methane emissions were higher for the TMR group than the grass group (397 vs. 251 g/cow per day). The TMR group also emitted more CH4 per kg of FP (200 vs. 174 g/kg of FP) than did the grass group. They also emitted more CH4 per kg of DMI (20.28 vs. 18.06 g/kg of DMI) than did the grass group. In this study, spring-calving cows, consuming a high quality perennial ryegrass diet in the spring, produced less enteric CH4 emissions per cow, per unit of intake, and per unit of FP than did cows offered a standard TMR diet.
Publisher: Springer Science and Business Media LLC
Date: 09-02-2011
DOI: 10.1038/NATURE09787
Publisher: Rockefeller University Press
Date: 08-05-2006
DOI: 10.1084/JEM.20052105
Abstract: Hematopoietic stem cells (HSCs) sustain lifelong production of all blood cell types through finely balanced isions leading to self-renewal and differentiation. Although several genes influencing HSC self-renewal have been identified, to date no gene has been described that, when activated, enhances HSC self-renewal and, when activated, promotes HSC differentiation. We observe that the retinoic acid receptor (RAR)γ is selectively expressed in primitive hematopoietic precursors and that the bone marrow of RARγ knockout mice exhibit markedly reduced numbers of HSCs associated with increased numbers of more mature progenitor cells compared with wild-type mice. In contrast, RARα is widely expressed in hematopoietic cells, but RARα knockout mice do not exhibit any HSC or progenitor abnormalities. Primitive hematopoietic precursors overexpressing RARα differentiate predominantly to granulocytes in short-term culture, whereas those overexpressing RARγ exhibit a much more undifferentiated phenotype. Furthermore, loss of RARγ abrogated the potentiating effects of all-trans retinoic acid on the maintenance of HSCs in ex vivo culture. Finally, pharmacological activation of RARγ ex vivo promotes HSC self-renewal, as demonstrated by serial transplant studies. We conclude that the RARs have distinct roles in hematopoiesis and that RARγ is a critical physiological and pharmacological regulator of the balance between HSC self-renewal and differentiation.
Publisher: Rockefeller University Press
Date: 06-12-2004
Abstract: The molecular basis for the inverse relationship between differentiation and tumorigenesis is unknown. The function of runx2, a master regulator of osteoblast differentiation belonging to the runt family of tumor suppressor genes, is consistently disrupted in osteosarcoma cell lines. Ectopic expression of runx2 induces p27KIP1, thereby inhibiting the activity of S-phase cyclin complexes and leading to the dephosphorylation of the retinoblastoma tumor suppressor protein (pRb) and a G1 cell cycle arrest. Runx2 physically interacts with the hypophosphorylated form of pRb, a known coactivator of runx2, thereby completing a feed-forward loop in which progressive cell cycle exit promotes increased expression of the osteoblast phenotype. Loss of p27KIP1 perturbs transient and terminal cell cycle exit in osteoblasts. Consistent with the incompatibility of malignant transformation and permanent cell cycle exit, loss of p27KIP1 expression correlates with dedifferentiation in high-grade human osteosarcomas. Physiologic coupling of osteoblast differentiation to cell cycle withdrawal is mediated through runx2 and p27KIP1, and these processes are disrupted in osteosarcoma.
Publisher: Cold Spring Harbor Laboratory
Date: 08-06-2023
Abstract: The RNA editing enzyme adenosine deaminase acting on RNA 1 (ADAR1) is an essential regulator of the innate immune response to both cellular and viral double-stranded RNA (dsRNA). Adenosine-to-inosine (A-to-I) editing by ADAR1 modifies the sequence and structure of endogenous dsRNA and masks it from the cytoplasmic dsRNA sensor melanoma differentiation-associated protein 5 (MDA5), preventing innate immune activation. Loss-of-function mutations in ADAR are associated with rare autoinflammatory disorders including Aicardi–Goutières syndrome (AGS), defined by a constitutive systemic up-regulation of type I interferon (IFN). The murine Adar gene encodes two protein isoforms with distinct functions: ADAR1p110 is constitutively expressed and localizes to the nucleus, whereas ADAR1p150 is primarily cytoplasmic and is inducible by IFN. Recent studies have demonstrated the critical requirement for ADAR1p150 to suppress innate immune activation by self dsRNAs. However, detailed in vivo characterization of the role of ADAR1p150 during development and in adult mice is lacking. We identified a new ADAR1p150-specific knockout mouse mutant based on a single nucleotide deletion that resulted in the loss of the ADAR1p150 protein without affecting ADAR1p110 expression. The Adar1p150 − / − died embryonically at E11.5–E12.5 accompanied by cell death in the fetal liver and an activated IFN response. Somatic loss of ADAR1p150 in adults was lethal and caused rapid hematopoietic failure, demonstrating an ongoing requirement for ADAR1p150 in vivo. The generation and characterization of this mouse model demonstrates the essential role of ADAR1p150 in vivo and provides a new tool for dissecting the functional differences between ADAR1 isoforms and their physiological contributions.
Publisher: Cold Spring Harbor Laboratory
Date: 31-08-2022
DOI: 10.1101/2022.08.31.506069
Abstract: The RNA editing enzyme Adenosine deaminase acting on RNA 1 (ADAR1) is an essential regulator of innate immune activation by both cellular and viral dsRNA. Adenosine-to-Inosine (A-to-I) editing by ADAR1 modifies the sequence and structure of endogenous dsRNA and masks it from the cytoplasmic dsRNA sensor melanoma differentiation-associated protein 5 (MDA5), preventing innate immune activation. Loss of function mutations in ADAR are associated with rare autoinflammatory disorders including Aicardi-Goutières Syndrome (AGS), defined by a constitutive systemic upregulation of type I interferon (IFN). The murine Adar gene encodes two protein isoforms with distinct functions: ADAR1p110 is constitutively expressed and localizes to the nucleus, whereas ADAR1p150 is primarily cytoplasmic and is inducible by IFN. Recent studies have demonstrated the critical requirement for ADAR1p150 to suppress innate immune activation by self dsRNAs, however, detailed in vivo characterization of the role of ADAR1p150 during development and in adult mice is lacking. We developed a new ADAR1p150-specific knockout mouse mutant based on a single nucleotide deletion that resulted in the loss of the ADARp150 protein without affecting ADAR1p110 expression. The Adar1p150 -/- died embryonically at E11.5-E12.5 due to cell death in the fetal liver accompanied by an activated IFN response. Somatic loss of ADAR1p150 in adults was lethal and caused rapid hematopoietic failure, demonstrating an ongoing requirement for ADAR1p150 in vivo . The generation and characterization of this mouse model demonstrates the essential role of ADAR1p150 in vivo and provides a new tool for dissecting the functional differences between ADAR1 isoforms and their physiological contributions.
Publisher: American Dairy Science Association
Date: 10-2010
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 02-2007
Publisher: Springer Science and Business Media LLC
Date: 16-10-2023
Publisher: Springer Science and Business Media LLC
Date: 25-05-2022
Publisher: American Society of Hematology
Date: 27-01-2022
Publisher: Springer Science and Business Media LLC
Date: 28-08-2018
DOI: 10.1038/S41419-018-0944-8
Abstract: The loss of p53 function is a central event in the genesis of osteosarcoma (OS). How mutation of p53 enables OS development from osteoblastic lineage cells is poorly understood. We and others have reported a key role for elevated and persistent activation of the cAMP/PKA/Creb1 pathway in maintenance of OS. In view of the osteoblast lineage being the cell of origin of OS, we sought to determine how these pathways interact within the context of the normal osteoblast. Normal osteoblasts (p53 WT) rapidly underwent apoptosis in response to acute elevation of cAMP levels or activity, whereas p53-deficient osteoblasts tolerated this aberrant cAMP/Creb level and activity. Using the p53 activating small-molecule Nutlin-3a and cAMP/Creb1 activator forskolin, we addressed the question of how p53 responds to the activation of cAMP. We observed that p53 acts dominantly to protect cells from excessive cAMP accumulation. We identify a Creb1-Cbp complex that functions together with and interacts with p53. Finally, translating these results we find that a selective small-molecule inhibitor of the Creb1-Cbp interaction demonstrates selective toxicity to OS cells where this pathway is constitutively active. This highlights the cAMP/Creb axis as a potentially actionable therapeutic vulnerability in p53-deficient tumors such as OS. These results define a mechanism through which p53 protects normal osteoblasts from excessive or abnormal cAMP accumulation, which becomes fundamentally compromised in OS.
Publisher: Cold Spring Harbor Laboratory
Date: 07-02-2008
DOI: 10.1101/GAD.1627208
Abstract: Regulation of the cell cycle is intimately linked to erythroid differentiation, yet how these processes are coupled is not well understood. To gain insight into this coordinate regulation, we examined the role that the retinoblastoma protein (Rb), a central regulator of the cell cycle, plays in erythropoiesis. We found that Rb serves a cell-intrinsic role and its absence causes ineffective erythropoiesis, with a differentiation block at the transition from early to late erythroblasts. Unexpectedly, in addition to a failure to properly exit the cell cycle, mitochondrial biogenesis fails to be up-regulated concomitantly, contributing to this differentiation block. The link between erythropoiesis and mitochondrial function was validated by inhibition of mitochondrial biogenesis. Erythropoiesis in the absence of Rb resembles the human myelodysplastic syndromes, where defects in cell cycle regulation and mitochondrial function frequently occur. Our work demonstrates how these seemingly disparate pathways play a role in coordinately regulating cellular differentiation.
Publisher: Springer Science and Business Media LLC
Date: 08-09-2008
Abstract: The retinoblastoma protein, Rb, was one of the first tumor suppressor genes identified as a result of the familial syndrome retinoblastoma. In the period since its identification and cloning a large number of studies have described its role in various cellular processes. The application of conditional somatic mutation with lineage and temporally controlled gene deletion strategies, thus circumventing the lethality associated with germ-line deletion of Rb, have allowed for a reanalysis of the in vivo role of Rb. In the hematopoietic system, such approaches have led to new insights into stem cell biology and the role of the microenvironment in regulating hematopoietic stem cell fate. They have also clarified the role that Rb plays during erythropoiesis and defined a novel mechanism linking mitochondrial function to terminal cell cycle withdrawal. These studies have shed light on the in vivo role of Rb in the regulation of hematopoiesis and also prompt further analysis of the role that Rb plays in both the regulation of hematopoietic stem cells and the terminal differentiation of their progeny.
Publisher: Public Library of Science (PLoS)
Date: 10-04-2015
Publisher: American Chemical Society (ACS)
Date: 12-2017
Publisher: eLife Sciences Publications, Ltd
Date: 12-04-2016
DOI: 10.7554/ELIFE.13446
Abstract: Mutations in the P53 pathway are a hallmark of human cancer. The identification of pathways upon which p53-deficient cells depend could reveal therapeutic targets that may spare normal cells with intact p53. In contrast to P53 point mutations in other cancer, complete loss of P53 is a frequent event in osteosarcoma (OS), the most common cancer of bone. The consequences of p53 loss for osteoblastic cells and OS development are poorly understood. Here we use murine OS models to demonstrate that elevated Pthlh (Pthrp), cAMP levels and signalling via CREB1 are characteristic of both p53-deficient osteoblasts and OS. Normal osteoblasts survive depletion of both PTHrP and CREB1. In contrast, p53-deficient osteoblasts and OS depend upon continuous activation of this pathway and undergo proliferation arrest and apoptosis in the absence of PTHrP or CREB1. Our results identify the PTHrP-cAMP-CREB1 axis as an attractive pathway for therapeutic inhibition in OS.
Publisher: Cold Spring Harbor Laboratory
Date: 30-01-2023
DOI: 10.1101/2023.01.29.526130
Abstract: Adenosine to inosine editing (A-to-I) in regions of double stranded RNA (dsRNA) is mediated by adenosine deaminase acting on RNA 1 (ADAR1) or ADAR2. ADAR1 and A-to-I editing levels are increased in many human cancers. It is not established if elevated ADAR1 represents a driver or passenger during cancer formation. We established a series of murine alleles to allow in vivo overexpression of ADAR1, its in idual isoforms or mutant forms of ADAR1 to understand how it contributes to cancer pathogenesis. The widespread overexpression of ADAR1 or either the p110 or p150 isoforms as sole lesions was well tolerated and did not result in cancer formation. Therefore, ADAR1 overexpression alone is not sufficient to initiate cancer. We demonstrate that endogenous ADAR1 and A-to-I editing levels increased upon immortalization by loss of p53 in murine cells, consistent with the observations from human cancers. We tested if ADAR1 overexpression could co- operate with cancer initiated by loss of tumour suppressors using a model of osteosarcoma. We did not see a disease potentiating or modifying effect of overexpressing ADAR1 or its isoforms. We conclude that the increase in ADAR1 expression and A-to-I editing in cancers is a passenger, rather than a driver, of tumor formation.
Publisher: Elsevier BV
Date: 10-2016
Publisher: Springer Science and Business Media LLC
Date: 22-06-2011
DOI: 10.1038/NATURE10223
Publisher: EMBO
Date: 28-03-2023
Abstract: ADAR1 ‐mediated A‐to‐I RNA editing is a self‐/non‐self‐discrimination mechanism for cellular double‐stranded RNAs. ADAR mutations are one cause of Aicardi–Goutières Syndrome, an inherited paediatric encephalopathy, classed as a “Type I interferonopathy.” The most common ADAR1 mutation is a proline 193 alanine (p.P193A) mutation, mapping to the ADAR1p150 isoform‐specific Zα domain. Here, we report the development of an independent murine P195A knock‐in mouse, homologous to human P193A. The Adar1 P195A / P195A mice are largely normal and the mutation is well tolerated. When the P195A mutation is compounded with an Adar1 null allele ( Adar1 P195A /− ), approximately half the animals are runted with a shortened lifespan while the remaining Adar1 P195A /− animals are normal, contrasting with previous reports. The phenotype of the Adar1 P195A /− animals is both associated with the parental genotype and partly non‐genetic/environmental. Complementation with an editing‐deficient ADAR1 ( Adar1 P195A / E861A ), or the loss of MDA5, rescues phenotypes in the Adar1 P195A /− mice.
Publisher: Elsevier BV
Date: 11-2013
DOI: 10.1016/J.STEM.2013.10.010
Abstract: In recent years, technical developments in mouse genetics and imaging equipment have substantially advanced our understanding of hematopoietic stem cells (HSCs) and their niche. The availability of numerous Cre strains for targeting HSCs and microenvironmental cells provides extensive flexibility in experimental design, but it can also pose significant challenges due to strain-specific differences in cell specificity. Here we outline various genetic approaches for isolating, detecting, and ablating HSCs and niche components and provide a guide for advantages and caveats to consider. We also discuss opportunities and limitations presented by imaging technologies that allow investigation of HSC behavior in situ.
Publisher: Springer Science and Business Media LLC
Date: 28-09-2018
DOI: 10.1038/S41598-018-32858-5
Abstract: Skeletal osteoblasts are important regulators of B-lymphopoiesis, serving as a rich source of factors such as CXCL12 and IL-7 which are crucial for B-cell development. Recent studies from our laboratory and others have shown that deletion of Rptor , a unique component of the mTORC1 nutrient-sensing complex, early in the osteoblast lineage development results in defective bone development in mice. In this study, we now demonstrate that mTORC1 signalling in pre-osteoblasts is required for normal B-lymphocyte development in mice. Targeted deletion of Rptor in osterix-expressing pre-osteoblasts ( Rptor ob −/− ) leads to a significant reduction in the number of B-cells in the bone marrow, peripheral blood and spleen at 4 and 12 weeks of age. Rptor ob −/− mice also exhibit a significant reduction in pre-B and immature B-cells in the BM, indicative of a block in B-cell development from the pro-B to pre-B cell stage. Circulating levels of IL-7 and CXCL12 are also significantly reduced in Rptor ob −/− mice. Importantly, whilst Rptor -deficient osteoblasts are unable to support HSC differentiation to B-cells in co-culture, this can be rescued by the addition of exogenous IL-7 and CXCL12. Collectively, these findings demonstrate that mTORC1 plays an important role in extrinsic osteoblastic regulation of B-cell development.
Publisher: Springer Science and Business Media LLC
Date: 04-05-2020
Publisher: Springer Science and Business Media LLC
Date: 26-06-2020
Publisher: EMBO
Date: 25-10-2018
Publisher: Elsevier BV
Date: 04-2007
Publisher: Ferrata Storti Foundation (Haematologica)
Date: 10-01-2014
Publisher: American Association for Cancer Research (AACR)
Date: 14-07-2015
DOI: 10.1158/1078-0432.CCR-14-3026
Abstract: Purpose: Osteosarcoma is the most common cancer of bone occurring mostly in teenagers. Despite rapid advances in our knowledge of the genetics and cell biology of osteosarcoma, significant improvements in patient survival have not been observed. The identification of effective therapeutics has been largely empirically based. The identification of new therapies and therapeutic targets are urgently needed to enable improved outcomes for osteosarcoma patients. Experimental Design: We have used genetically engineered murine models of human osteosarcoma in a systematic, genome-wide screen to identify new candidate therapeutic targets. We performed a genome-wide siRNA screen, with or without doxorubicin. In parallel, a screen of therapeutically relevant small molecules was conducted on primary murine– and primary human osteosarcoma–derived cell cultures. All results were validated across independent cell cultures and across human and mouse osteosarcoma. Results: The results from the genetic and chemical screens significantly overlapped, with a profound enrichment of pathways regulated by PI3K and mTOR pathways. Drugs that concurrently target both PI3K and mTOR were effective at inducing apoptosis in primary osteosarcoma cell cultures in vitro in both human and mouse osteosarcoma, whereas specific PI3K or mTOR inhibitors were not effective. The results were confirmed with siRNA and small molecule approaches. Rationale combinations of specific PI3K and mTOR inhibitors could recapitulate the effect on osteosarcoma cell cultures. Conclusions: The approaches described here have identified dual inhibition of the PI3K–mTOR pathway as a sensitive, druggable target in osteosarcoma, and provide rationale for translational studies with these agents. Clin Cancer Res 21(14) 3216–29. ©2015 AACR.
Publisher: Rockefeller University Press
Date: 30-05-2006
Publisher: Wiley
Date: 24-09-2013
DOI: 10.1111/BJH.12578
Abstract: Vitamin A and its derivatives (retinoids) are important regulators of haematopoiesis, acting via retinoic acid receptors (RARs). Epidemiological studies indicated an association of vitamin A deficiency with anaemia in humans. To define the requirements of RARs in erythropoiesis, we evaluated erythroid parameters in RAR germ-line deficient and conditional knock out mice with erythroid specific deletion of RARs. Adult RARγ(-/-) mice were anaemic, however, Epor-Cre Rara(fl/fl) , Epor-Cre Rarg(fl/fl) and Epor-Cre Rara(fl/fl) g(fl/fl) mice were normal, indicating a lack of an erythroid intrinsic RAR function. Therefore, erythroid-specific RAR function is dispensable for erythropoiesis and RARγ plays an erythroid extrinsic role in erythropoiesis.
Publisher: Elsevier BV
Date: 06-2016
Publisher: Elsevier BV
Date: 06-2007
Publisher: The Royal Society
Date: 07-2020
DOI: 10.1098/RSOB.200085
Abstract: Adenosine-to-inosine (A-to-I) editing is a post-transcriptional modification of RNA which changes its sequence, coding potential and secondary structure. Catalysed by the adenosine deaminase acting on RNA (ADAR) proteins, ADAR1 and ADAR2, A-to-I editing occurs at approximately 50 000–150 000 sites in mice and into the millions of sites in humans. The vast majority of A-to-I editing occurs in repetitive elements, accounting for the discrepancy in total numbers of sites between species. The species-conserved primary role of editing by ADAR1 in mammals is to suppress innate immune activation by unedited cell-derived endogenous RNA. In the absence of editing, inverted paired sequences, such as Alu elements, are thought to form stable double-stranded RNA (dsRNA) structures which trigger activation of dsRNA sensors, such as MDA5. A small subset of editing sites are within coding sequences and are evolutionarily conserved across metazoans. Editing by ADAR2 has been demonstrated to be physiologically important for recoding of neurotransmitter receptors in the brain. Furthermore, changes in RNA editing are associated with various pathological states, from the severe autoimmune disease Aicardi-Goutières syndrome, to various neurodevelopmental and psychiatric conditions and cancer. However, does detection of an editing site imply functional importance? Genetic studies in humans and genetically modified mouse models together with evolutionary genomics have begun to clarify the roles of A-to-I editing in vivo . Furthermore, recent developments suggest there may be the potential for distinct functions of editing during pathological conditions such as cancer.
Publisher: Informa UK Limited
Date: 02-05-2005
DOI: 10.4161/CC.4.7.1831
Abstract: Pluripotent hematopoietic stem cells (HSCs) sustain blood cell production throughout an in idual's lifespan through complex processes supported by self-renewal, differentiation, senescence or cell death decisions of the HSCs. These decisions are tightly regulated under homeostatic conditions, allowing both the continuous generation of progenitors and mature cells in addition to the maintenance and replenishment of the HSC pool. Several recent studies have provided insights into some of the key molecular mechanisms regulating these different cell fate decisions. One of the emerging themes of these studies is that of the importance of cell cycle regulators in the maintenance of HSCs.
Publisher: Wiley
Date: 29-07-2004
Publisher: Springer Science and Business Media LLC
Date: 30-10-2017
Publisher: Springer Science and Business Media LLC
Date: 05-09-2017
Publisher: Springer Science and Business Media LLC
Date: 2011
DOI: 10.1007/S12185-010-0759-6
Abstract: The in vivo regulation of erythropoiesis involves the integration of a range of intrinsic and cell extrinsic cues. The macrophage contained within the erythroblastic island is central to the normal differentiation and support of erythroid development. The contributions of other cell types found within the local bone marrow microenvironment are also likely to play important roles depending on the context. Such cell types include osteoblasts, osteoclasts, adipocytes, endothelial cells in addition to developing hematopoietic cells. There are data correlating changes in erythroid homeostasis, particularly in anemic states such as hemoglobinopathies, with alterations in the skeleton. The interaction and coordination of erythroid development and skeletal homeostasis, particularly in setting of erythroid demand, may represent a centrally regulated axis that is important physiologically, pharmacologically and in the pathology of anemia states.
Publisher: Elsevier BV
Date: 06-2011
DOI: 10.1016/J.STEM.2011.04.010
Abstract: The Notch signaling pathway is activated in the majority of T cell acute lymphoblastic leukemias (T-ALL). Adding to the complexity of Notch signaling in hematopoiesis, recently in Nature, Klinakis et al. (2011) demonstrate a tumor-suppressor function for the Notch pathway in myeloid malignancy.
Publisher: Impact Journals, LLC
Date: 25-04-2016
Publisher: Springer Science and Business Media LLC
Date: 13-06-2022
DOI: 10.1038/S41592-022-01513-3
Abstract: Inosine is a prevalent RNA modification in animals and is formed when an adenosine is deaminated by the ADAR family of enzymes. Traditionally, inosines are identified indirectly as variants from Illumina RNA-sequencing data because they are interpreted as guanosines by cellular machineries. However, this indirect method performs poorly in protein-coding regions where exons are typically short, in non-model organisms with sparsely annotated single-nucleotide polymorphisms, or in disease contexts where unknown DNA mutations are pervasive. Here, we show that Oxford Nanopore direct RNA sequencing can be used to identify inosine-containing sites in native transcriptomes with high accuracy. We trained convolutional neural network models to distinguish inosine from adenosine and guanosine, and to estimate the modification rate at each editing site. Furthermore, we demonstrated their utility on the transcriptomes of human, mouse and Xenopus. Our approach expands the toolkit for studying adenosine-to-inosine editing and can be further extended to investigate other RNA modifications.
Publisher: Elsevier BV
Date: 12-2014
Publisher: Elsevier BV
Date: 09-2018
Publisher: Springer Science and Business Media LLC
Date: 05-04-2016
DOI: 10.1007/S00109-016-1416-1
Abstract: The innate immune system is the first line of the cellular defence against invading pathogens. A critical component of this defence is the capacity to discriminate foreign RNA molecules, which are distinct from most cellular RNAs in structure and/or modifications. However, a series of rare autoimmune/autoinflammatory diseases in humans highlight the propensity for the innate immune sensing system to be activated by endogenous cellular double-stranded RNAs (dsRNAs), underscoring the fine line between distinguishing self from non-self. The RNA editing enzyme ADAR1 has recently emerged as a key regulator that prevents innate immune pathway activation, principally the cytosolic dsRNA sensor MDA5, from inducing interferon in response to double-stranded RNA structures within endogenous RNAs. Adenosine-to-Inosine RNA editing by ADAR1 is proposed to destabilise duplexes formed from inverted repetitive elements within RNAs, which appear to prevent MDA5 from sensing these RNA as virus-like in the cytoplasm. Aberrant activation of these pathways has catastrophic effects at both a cellular and organismal level, contributing to one of the causes of the conditions collectively known as the type I interferonopathies.
Publisher: Oxford University Press (OUP)
Date: 11-03-2023
Abstract: Adenosine to inosine editing (A-to-I) in regions of double stranded RNA (dsRNA) is mediated by adenosine deaminase acting on RNA 1 (ADAR1) or ADAR2. ADAR1 and A-to-I editing levels are increased in many human cancers. Inhibition of ADAR1 has emerged as a high priority oncology target, however, whether ADAR1 overexpression enables cancer initiation or progression has not been directly tested. We established a series of in vivo models to allow overexpression of full-length ADAR1, or its in idual isoforms, to test if increased ADAR1 expression was oncogenic. Widespread over-expression of ADAR1 or the p110 or p150 isoforms in idually as sole lesions was well tolerated and did not result in cancer initiation. Therefore, ADAR1 overexpression alone is not sufficient to initiate cancer. We demonstrate that endogenous ADAR1 and A-to-I editing increased upon immortalization in murine cells, consistent with the observations from human cancers. We tested if ADAR1 over-expression could co-operate with cancer initiated by loss of tumour suppressors using a model of osteosarcoma. We did not see a disease potentiating or modifying effect of overexpressing ADAR1 or its isoforms in the models assessed. We conclude that increased ADAR1 expression and A-to-I editing in cancers is most likely a consequence of tumor formation.
Publisher: Elsevier BV
Date: 04-2012
Publisher: Springer Science and Business Media LLC
Date: 08-2009
DOI: 10.1038/NATURE08243
Publisher: Springer Science and Business Media LLC
Date: 04-12-2019
DOI: 10.1038/S41419-019-2160-6
Abstract: Modifications of RNA, collectively termed as the epitranscriptome, are widespread, evolutionarily conserved and contribute to gene regulation and protein ersity in healthy and disease states. There are RNA modifications described, greatly exceeding the number of modifications to DNA. Of these, adenosine-to-inosine (A-to-I) RNA editing is one of the most common. There are tens of thousands of A-to-I editing sites in mouse, and millions in humans. Upon translation or sequencing an inosine base is decoded as guanosine, leading to A-to-G mismatches between the RNA and DNA. Inosine has different base pairing properties to adenosine and as a result editing not only alters the RNA code but can also change the RNA structure. In mammals A-to-I editing is performed by ADAR1 and ADAR2. A feature of murine loss of function ADAR1 alleles is cell death and a failure to survive embryogenesis. Adar1 −/− and editing deficient ( Adar1 E861A/E861A ) mice die between E11.75–13.5 of failed hematopoiesis. Strikingly this phenotype is rescued by the deletion of the cytosolic dsRNA sensor MDA5 or its downstream adaptor MAVS, a mechanism conserved in human and mouse. Current literature indicates that the loss of ADAR1 leads to cell death via apoptosis, yet this has not been genetically established. We report that blockade of the intrinsic (mitochondrial) apoptosis pathway, through the loss of both BAK and BAX, does not rescue or modify the cellular phenotype of the fetal liver or extend the lifespan of ADAR1 editing deficient embryos. We had anticipated that the loss of BAK and BAX would rescue, or at least significantly extend, the gestational viability of Adar1 E861A/E861A embryos. However, the triple mutant Adar1 E861A/E861A Bak −/− Bax −/− embryos that were recovered at E13.5 were indistinguishable from the Adar1 E861A/E861A embryos with BAK and BAX. The results indicate that cell death processes not requiring the intrinsic apoptosis pathway are triggered by MDA5 following the loss of ADAR1.
Publisher: American Society of Hematology
Date: 04-05-2017
DOI: 10.1182/BLOOD-2016-06-725093
Abstract: Combined loss of Ssb1/Ssb2 induces rapid lethality due to replication stress–associated loss of hematopoietic stem and progenitor cells. Functionally, loss of Ssb1/Ssb2 activates p53 and IFN pathways, causing enforced cell cycling in quiescent HSPCs and apoptotic cell loss.
Publisher: Rockefeller University Press
Date: 13-08-2012
DOI: 10.1084/JEM.20120785
Abstract: Developing B lymphocytes expressing defective or autoreactive pre-B or B cell receptors (BCRs) are eliminated by programmed cell death, but how the balance between death and survival signals is regulated to prevent immunodeficiency and autoimmunity remains incompletely understood. In this study, we show that absence of the essential ATM (ataxia telangiectasia mutated) substrate Chk2-interacting Zn2+-finger protein (ASCIZ also known as ATMIN/ZNF822), a protein with dual functions in the DNA damage response and as a transcription factor, leads to progressive cell loss from the pre-B stage onwards and severely diminished splenic B cell numbers in mice. This lymphopenia cannot be suppressed by deletion of p53 or complementation with a prearranged BCR, indicating that it is not caused by impaired DNA damage responses or defective V(D)J recombination. Instead, ASCIZ-deficient B cell precursors contain highly reduced levels of DYNLL1 (dynein light chain 1 LC8), a recently identified transcriptional target of ASCIZ, and normal B cell development can be restored by ectopic Dynll1 expression. Remarkably, the B cell lymphopenia in the absence of ASCIZ can also be fully suppressed by deletion of the proapoptotic DYNLL1 target Bim. Our findings demonstrate a key role for ASCIZ in regulating the survival of developing B cells by activating DYNLL1 expression, which may then modulate Bim-dependent apoptosis.
Publisher: Cold Spring Harbor Laboratory
Date: 12-11-2020
DOI: 10.1101/2020.11.11.379214
Abstract: Rothmund-Thomson Syndrome (RTS) is an autosomal recessive disorder characterized by poikiloderma, sparse or absent hair, and defects in the skeletal system such as bone hypoplasia, short stature, low bone mass, and an increased incidence of osteosarcoma. RTS type 2 patients typically present with germline compound bi-allelic protein-truncating mutations of RECQL4 . As existing murine models predominantly employ Recql4 null alleles, we have here attempted to more accurately model the mutational spectrum of RTS by generating mice with patient-mimicking truncating Recql4 mutations. We found that truncating mutations impaired stability and subcellular localization of RECQL4, which translated to a homozygous embryonic lethality and haploinsufficient low bone mass and reduced cortical bone thickness phenotypes. Combination of a truncating mutation with a conditional Recql4 null allele demonstrated that these defects were intrinsic to the osteoblast lineage. However, the truncating mutations did not promote tumorigenesis, even after exposure to irradiation. We also utilized murine Recql4 null cells to assess the impact of a wider range of human RECQL4 mutations using an in vitro complementation assay. We found differential effects of distinct RECQL4 mutations. While some created unstable protein products, others altered subcellular localization of the protein. Interestingly, the severity of the phenotypes correlated with the extent of protein truncation. Collectively, our results reveal that truncating RECQL4 mutations lead to the development of an osteoporosis-like phenotype through defects in early osteoblast progenitors in mice and identify RECQL4 gene dosage as a novel regulator of bone mass.
Publisher: Elsevier BV
Date: 08-2020
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 07-2019
Publisher: Informa UK Limited
Date: 05-2002
Publisher: American Society for Clinical Investigation
Date: 12-2011
DOI: 10.1172/JCI58577
Publisher: Elsevier BV
Date: 05-2014
DOI: 10.1016/J.BONE.2014.02.003
Abstract: Osteosarcoma is a disease with many complex genetic abnormalities but few well defined genetic drivers of tumor initiation and evolution. The disease is diagnosed and defined through the observation of malignant osteoblastic cells that produce osteoid, however the exact cell of origin for this cancer remains to be definitively defined. Evidence exists to support a mesenchymal stem cell as well as committed osteoblast precursors as the cell of origin. Increasing numbers of experimental models have begun to shed light on to the likely cell population that gives rise to OS in vivo with the weight of evidence favoring an osteoblastic population as the cell of origin. As more information is gathered regarding osteosarcoma initiating cells and how they may relate to the cell of origin we will derive a better understanding of the development of this disease which may ultimately lead to clinical improvements through more personalized therapeutic approaches.
Publisher: Cold Spring Harbor Laboratory
Date: 21-06-2022
DOI: 10.1101/2022.06.21.496931
Abstract: Recurrent mutations in two pathways - the RNA spliceosome (eg. SRSF2, SF3B1, U2AF1 ) and epigenetic regulators (eg. DNMT3, TET2 ) – contribute to the development of myelodysplastic syndrome (MDS) and related myeloid neoplasms. In chronic myelomonocytic leukemia (CMML), SRSF2 mutations occur in ∼50% of patients and TET2 mutations in ∼60%, representing two of the most frequent mutations in these cancers. Clonal analysis has indicated that either mutation can arise as the founder lesion, however, our understanding of the basis for the co-operativity of these mutations in the evolution of CMML is limited. Based on human cancer genetics we crossed an inducible Srsf2 P95H/+ mutant model with Tet2 fl/fl mice to mutate both concomitantly (or in idually) in hematopoietic stem cells. At 20-24 weeks post gene mutation, we observed subtle differences in the Srsf2 / Tet2 mutants compared to either single mutant. Under conditions of native hematopoiesis with aging, we see a distinct myeloid bias and monocytosis in the Srsf2 / Tet2 mutants. A subset of the compound Srsf2 / Tet2 mutants display an increased granulocytic and distinctive monocytic proliferation (myelo-monocytic hyperplasia), with increased immature promonocytes and monoblasts (∼10-15% total nucleated cells), and evidence of binucleate promonocytes. Exome analysis of progressed disease demonstrates mutations in genes and pathways similar to those reported in human CMML. Upon transplantation, recipients developed leukocytosis, monocytosis and splenomegaly. This demonstrates we can reproduce Srsf2/Tet2 co-operativity in vivo , yielding a disease with core characteristics of CMML, unlike single Srsf2 or Tet2 mutation. This model represents a significant step toward building high fidelity and genetically tractable models of CMML. Srsf2 P95H/+ co-operates with Tet2 -/- to initiate CMML in a murine model Srsf2 P95H and Tet2 null mutations synergize in the development of monocytosis
Publisher: American Society for Clinical Investigation
Date: 15-11-2013
DOI: 10.1172/JCI70559
Publisher: Springer New York
Date: 2019
DOI: 10.1007/978-1-4939-8997-3_18
Abstract: This chapter describes the procedures for inducing bone sarcoma in mice. Two models based on inoculation of cancer cells in paraosseous and intraosseous site will be described. In addition to providing technical aspects of anesthesia and surgical options, key information of cell preparation and postoperative follow-up will be discussed.
Publisher: Wiley
Date: 18-04-2011
DOI: 10.1002/JCB.23085
Abstract: Understanding the in vivo regulation of hematopoietic stem cells (HSCs) will be critical to identifying key factors involved in the regulation of HSC self-renewal and differentiation. The niche (microenvironment) in which HSCs reside has recently regained attention accompanied by a dramatic increase in the understanding of the cellular constituents of the bone marrow HSC niche. The use of sophisticated genetic models allowing modulation of specific lineages has demonstrated roles for mesenchymal-derived elements such as osteoblasts and adipocytes, vasculature, nerves, and a range of hematopoietic progeny of the HSC as being participants in the regulation of the bone marrow microenvironment. Whilst providing significant insight into the cellular composition of the niche, is it possible to manipulate any given cell lineage in vivo without impacting, knowingly or unknowingly, on those that remain?
Publisher: Springer Science and Business Media LLC
Date: 12-10-2017
DOI: 10.1038/NATURE24041
Publisher: Proceedings of the National Academy of Sciences
Date: 13-06-2006
Abstract: Stem cells have been identified as essential for maintaining multiple organ systems, including the hematopoietic system. The distinct cell fates of self-renewal and differentiation of hematopoietic stem cells (HSCs) depend on cell ision. Recently, several negative regulators of the cell cycle, such as the cyclin-dependent kinase inhibitors p21 Cip1 , p27 Kip1 , and p16 INK4a 19 ARF , have been demonstrated to have a role in regulating HSC fate decisions, suggesting that regulation of the G 1 –S phase transition can contribute to HSC self-renewal. Because the retinoblastoma protein, Rb, plays a central role in the regulation of the G 1 –S phase cell cycle, we sought to determine whether it has an intrinsic role in the regulation of HSC fate. Surprisingly, we found that HSC function was essentially normal in the absence of Rb. Rb Δ/Δ HSCs contributed normally to both myeloid and lymphoid lineages in both primary and secondary recipients, and no evidence of transformation was observed. Additionally, we observed a mild myeloid expansion and decrease in mature B cells within the Rb Δ/Δ bone marrow but a similar contribution to phenotypic HSC populations compared with nondeleted bone marrow. The Rb family members p107 and p130 were not deregulated in cells in which Rb had been deleted, as determined by quantitative RT-PCR on the highly enriched stem and primitive progenitor cell lin − c-Kit + Sca-1 + population. These studies demonstrate that Rb is not intrinsically required for self-renewal and multilineage differentiation of adult HSCs.
Publisher: Elsevier BV
Date: 02-2016
DOI: 10.1016/J.CELREP.2016.01.012
Abstract: How MYC promotes the development of cancer remains to be fully understood. Here, we report that the Zn(2+)-finger transcription factor ASCIZ (ATMIN, ZNF822) synergizes with MYC to activate the expression of dynein light chain (DYNLL1, LC8) in the murine Eμ-Myc model of lymphoma. Deletion of Asciz or Dynll1 prevented the abnormal expansion of pre-B cells in pre-cancerous Eμ-Myc mice and potentiated the pro-apoptotic activity of MYC in pre-leukemic immature B cells. Constitutive loss of Asciz or Dynll1 delayed lymphoma development in Eμ-Myc mice, and induced deletion of Asciz in established lymphomas extended the survival of tumor-bearing mice. We propose that ASCIZ-dependent upregulation of DYNLL1 levels is essential for the development and expansion of MYC-driven lymphomas by enabling the survival of pre-neoplastic and malignant cells.
Publisher: Springer Science and Business Media LLC
Date: 16-01-2005
DOI: 10.1038/NCB1214
Abstract: Haematopoietic stem cells (HSCs) are capable of shifting from a state of relative quiescence under homeostatic conditions to rapid proliferation under conditions of stress. The mechanisms that regulate the relative quiescence of stem cells and its association with self-renewal are unclear, as is the contribution of molecular regulators of the cell cycle to these decisions. Understanding the mechanisms that govern these transitions will provide important insights into cell-cycle regulation of HSCs and possible therapeutic approaches to expand HSCs. We have investigated the role of two negative regulators of the cell cycle, p27(Kip1) and MAD1, in controlling this transition. Here we show that Mad1(-/-)p27(Kip1-/-) bone marrow has a 5.7-fold increase in the frequency of stem cells, and surprisingly, an expanded pool of quiescent HSCs. However, Mad1(-/-)p27(Kip1-/-) stem cells exhibit an enhanced proliferative response under conditions of stress, such as cytokine stimulation in vitro and regeneration of the haematopoietic system after ablation in vivo. Together these data demonstrate that the MYC-antagonist MAD1 and cyclin-dependent kinase inhibitor p27(Kip1) cooperate to regulate the self-renewal and differentiation of HSCs in a context-dependent manner.
Publisher: American Society of Hematology
Date: 26-05-2011
DOI: 10.1182/BLOOD-2010-11-320564
Abstract: Erythropoietin (Epo) has been used in the treatment of anemia resulting from numerous etiologies, including renal disease and cancer. However, its effects are controversial and the expression pattern of the Epo receptor (Epo-R) is debated. Using in vivo lineage tracing, we document that within the hematopoietic and mesenchymal lineage, expression of Epo-R is essentially restricted to erythroid lineage cells. As expected, adult mice treated with a clinically relevant dose of Epo had expanded erythropoiesis because of lification of committed erythroid precursors. Surprisingly, we also found that Epo induced a rapid 26% loss of the trabecular bone volume and impaired B-lymphopoiesis within the bone marrow microenvironment. Despite the loss of trabecular bone, hematopoietic stem cell populations were unaffected. Inhibition of the osteoclast activity with bisphosphonate therapy blocked the Epo-induced bone loss. Intriguingly, bisphosphonate treatment also reduced the magnitude of the erythroid response to Epo. These data demonstrate a previously unrecognized in vivo regulatory network coordinating erythropoiesis, B-lymphopoiesis, and skeletal homeostasis. Importantly, these findings may be relevant to the clinical application of Epo.
Publisher: Elsevier BV
Date: 11-2010
DOI: 10.1016/J.BONE.2010.07.028
Abstract: Osteosarcoma (OS) is the most common primary tumour of bone, occurring predominantly in the second decade of life. High-dose cytotoxic chemotherapy and surgical resection have improved prognosis, with long-term survival for patients with localized (non-metastatic) disease approaching 70%. At presentation approximately 20% of patients have metastases and almost all patients with recurrent OS have metastatic disease and cure rates for patients with metastatic or recurrent disease remain poor (<20% survival). Over the past 20 years, considerable progress has been made in the understanding of OS pathogenesis, yet these insights have not translated into substantial therapeutic advances and clinical outcomes. Further progress is essential in order to develop molecularly based therapies that target both primary lesions as well as metastatic disease. The increasing sophistication with which gene expression can be modulated in the mouse, both positively and negatively in addition to temporally, has allowed for the recent generation of more faithful OS models than have previously been available. These murine OS models can recapitulate all aspects of the disease process, from initiation and establishment to invasion and dissemination to distant sites. The development and utilisation of murine models that faithfully recapitulate human osteosarcoma, complementing existing approaches using human and canine disease, holds significant promise in furthering our understanding of the genetic basis of the disease and, more critically, in advancing pre-clinical studies aimed at the rational development and trialing of new therapeutic approaches.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 04-09-2015
Abstract: Adenosine bases in messenger RNA (mRNAs) can be enzymatically modified and changed into inosine bases. This RNA “editing” is mediated by adenosine deaminase acting on RNA (ADAR) enzymes. Liddicoat et al. show that the in vivo targets of the principal editing enzyme, ADAR1, are long double-stranded RNA (dsRNA) structures in noncoding portions of cellular mRNAs. ADAR1-directed editing of these cellular targets is critical to avoid activation of an immune response to dsRNA in the cytoplasm, because dsRNA is also a marker of viral infection. Science , this issue p. 1115
Publisher: Elsevier BV
Date: 04-2015
DOI: 10.1016/J.BONE.2014.12.063
Abstract: Wnt pathway targeting is of high clinical interest for treating bone loss disorders such as osteoporosis. These therapies inhibit the action of negative regulators of osteoblastic Wnt signaling. The report that Wnt inhibitory factor 1 (WIF1) was epigenetically silenced via promoter DNA methylation in osteosarcoma (OS) raised potential concerns for such treatment approaches. Here we confirm that Wif1 expression is frequently reduced in OS. However, we demonstrate that silencing is not driven by DNA methylation. Treatment of mouse and human OS cells showed that Wif1 expression was robustly induced by HDAC inhibition but not by methylation inhibition. Consistent with HDAC dependent silencing, the Wif1 locus in OS was characterized by low acetylation levels and a bivalent H3K4/H3K27-trimethylation state. Wif1 expression marked late stages of normal osteoblast maturation and stratified OS tumors based on differentiation stage across species. Culture of OS cells under differentiation inductive conditions increased expression of Wif1. Together these results demonstrate that Wif1 is not targeted for silencing by DNA methylation in OS. Instead, the reduced expression of Wif1 in OS cells is in context with their stage in differentiation.
Start Date: 2018
End Date: 12-2020
Amount: $425,349.00
Funder: Australian Research Council
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