Publications by authors named "Louise E Purton"

62 Publications

Sugar Rush: Supercharging Blood Cell Specification via the Inflammasome.

Dev Cell 2020 10;55(2):109-111

Stem Cell Regulation Unit, St. Vincent's Institute, Fitzroy, VIC 3065, Australia; The University of Melbourne Department of Medicine at St. Vincent's Hospital, Fitzroy, VIC 3065, Australia. Electronic address:

The generation of adult hematopoietic stem and progenitor cells (HSPCs) from embryonic and induced pluripotent stem cells (iPSCs) will provide therapeutic benefits but is currently elusive. In this issue of Developmental Cell, Frame et al. reveal that the inflammasome has a key role in HSPCs specification during endothelial-to-hematopoietic transition (EHT).
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http://dx.doi.org/10.1016/j.devcel.2020.09.026DOI Listing
October 2020

retinoic acid in non-promyelocytic acute myeloid leukemia: driver lesion dependent effects on leukemic stem cells.

Cell Cycle 2020 Oct 8;19(20):2573-2588. Epub 2020 Sep 8.

Division of Oncology, Department of Medicine I, Medical University of Vienna , Vienna, Austria.

Acute myeloid leukemia (AML) is an aggressive, often fatal hematopoietic malignancy. retinoic acid (atRA), one of the first molecularly targeted drugs in oncology, has greatly improved the outcome of a subtype of AML, acute promyelocytic leukemia (APL). In contrast, atRA has so far provided little therapeutic benefit in the much larger group of patients with non-APL AML. Attempts to identify genetically or molecularly defined subgroups of patients that may respond to atRA have not yielded consistent results. Since AML is a stem cell-driven disease, understanding the effectiveness of atRA may require an appreciation of its impact on AML stem cells. Recent studies reported that atRA decreased stemness of AML with an -ITD mutation, yet increased it in driven or -overexpressing AML. This review summarizes the role of atRA in normal hematopoiesis and in AML, focusing on its impact on AML stem cells.
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http://dx.doi.org/10.1080/15384101.2020.1810402DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7644151PMC
October 2020

Effects of chemotherapy agents used to treat pediatric acute lymphoblastic leukemia patients on bone parameters and longitudinal growth of juvenile mice.

Exp Hematol 2020 02 10;82:1-7. Epub 2020 Feb 10.

St. Vincent's Institute of Medical Research, Fitzroy, VIC, Australia; Department of Medicine, University of Melbourne, Parkville, VIC, Australia. Electronic address:

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer. Therapies for pediatric ALL have improved such that more than 80% of patients survive to 5 years post-therapy, and most survive to adulthood. These ALL patients experience long-term side effects that permanently affect their quality of life, with bone loss and reduced longitudinal growth being the most common skeletal complications. To determine the effects of the chemotherapeutic agents used in ALL induction therapy on bone density and longitudinal growth in mice, we treated juvenile mice with doxorubicin, dexamethasone, vincristine, l-asparaginase, or combination therapy. At adulthood, mice were culled and bones collected and scanned by micro-computed tomography (micro-CT). Mice that received doxorubicin and combination therapy exhibited reduced longitudinal growth and significant reductions in trabecular bone volume, trabecular thickness, and trabecular number, with increased trabecular separation. Mean cortical thickness, cortical area, marrow area, endocortical perimeter, and polar moment of inertia were significantly reduced by doxorubicin and combination therapy. Vincristine treatment significantly decreased trabecular bone volume, trabecular number, and increased trabecular separation but had no effects on cortical bone. Dexamethasone treatment increased trabecular bone separation, cortical marrow area, and cortical bone periosteal perimeter. Mice treated with l-asparaginase did not have any bone phenotypes. In conclusion, these data indicate that the majority of the chemotherapy agents used in induction therapy for pediatric ALL have long-term effects on bone in mice. A single dose of doxorubicin in juvenile mice was sufficient to cause the majority of the bone phenotypes, with combination therapy intensifying these effects.
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http://dx.doi.org/10.1016/j.exphem.2020.01.010DOI Listing
February 2020

All-trans retinoic acid enhances, and a pan-RAR antagonist counteracts, the stem cell promoting activity of EVI1 in acute myeloid leukemia.

Cell Death Dis 2019 12 10;10(12):944. Epub 2019 Dec 10.

Division of Oncology, Clinic of Medicine I, Medical University of Vienna, Vienna, Austria.

Ecotropic virus integration site 1 (EVI1), whose overexpression characterizes a particularly aggressive subtype of acute myeloid leukemia (AML), enhanced anti-leukemic activities of all-trans retinoic acid (atRA) in cell lines and patient samples. However, the drivers of leukemia formation, therapy resistance, and relapse are leukemic stem cells (LSCs), whose properties were hardly reflected in these experimental setups. The present study was designed to address the effects of, and interactions between, EVI1 and retinoids in AML LSCs. We report that Evi1 reduced the maturation of leukemic cells and promoted the abundance, quiescence, and activity of LSCs in an MLL-AF9-driven mouse model of AML. atRA further augmented these effects in an Evi1 dependent manner. EVI1 also strongly enhanced atRA regulated gene transcription in LSC enriched cells. One of their jointly regulated targets, Notch4, was an important mediator of their effects on leukemic stemness. In vitro exposure of leukemic cells to a pan-RAR antagonist caused effects opposite to those of atRA. In vivo antagonist treatment delayed leukemogenesis and reduced LSC abundance, quiescence, and activity in Evi1 AML. Key results were confirmed in human myeloid cell lines retaining some stem cell characteristics as well as in primary human AML samples. In summary, our study is the first to report the importance of EVI1 for key properties of AML LSCs. Furthermore, it shows that atRA enhances, and a pan-RAR antagonist counteracts, the effects of EVI1 on AML stemness, thus raising the possibility of using RAR antagonists in the therapy of EVI1 AML.
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http://dx.doi.org/10.1038/s41419-019-2172-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6904467PMC
December 2019

A population of nonneuronal GFRα3-expressing cells in the bone marrow resembles nonmyelinating Schwann cells.

Cell Tissue Res 2019 Dec 14;378(3):441-456. Epub 2019 Jul 14.

Department of Anatomy and Neuroscience, University of Melbourne, Melbourne, Victoria, 3010, Australia.

Artemin is a neurotrophic factor that plays a crucial role in the regulation of neural development and regeneration and has also been implicated in the pathogenesis of inflammatory pain. The receptor for artemin, GFRα3, is expressed by sympathetic and nociceptive sensory neurons, including some that innervate the bone marrow, but it is unclear if it is also expressed in other cell types in the bone marrow. Our goal in the present study was to characterise the expression of GFRα3 in nonneuronal cells in the bone marrow. Immunohistochemical studies revealed that GFRα3-expressing cells in the bone marrow are spatially associated with blood vessels and are in intimate contact with nerve fibres. We used various combinations of markers to distinguish different cell types and found that the GFRα3-expressing cells expressed markers of nonmyelinating Schwann cells (e.g. GFAP, p75NTR, nestin). Analysis of bone marrow sections of Wnt1-reporter mice also demonstrated that they originate from the neural crest. Further characterisation using flow cytometry revealed that GFRα3 is expressed in a population of CD51Sca1PDGFRα cells, reinforcing the notion that they are neural crest-derived, nonmyelinating Schwann cells. In conclusion, there is a close association between peripheral nerve terminals and a population of nonneuronal cells that express GFRα3 in the bone marrow. The nonneuronal cells have characteristics consistent with a neural crest-derived, nonmyelinating Schwann cell phenotype. Our findings provide a better understanding of the expression pattern of GFRα3 in the bone marrow microenvironment.
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http://dx.doi.org/10.1007/s00441-019-03068-wDOI Listing
December 2019

Hemopoietic Cell Kinase amplification with Protein Tyrosine Phosphatase Receptor T depletion leads to polycythemia, aberrant marrow erythoid maturation, and splenomegaly.

Sci Rep 2019 05 7;9(1):7050. Epub 2019 May 7.

Department of Medicine, St Vincent's Hospital, The University of Melbourne, 3065, Fitzroy, Australia.

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 samples has identified two regions of interest on 20q - the "Common Deleted Region" (CDR) and "Common Retained Region" (CRR), which was often amplified. 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 amplification coupled with PTPRT loss in del(20q) leads to development of a myeloproliferative phenotype.
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http://dx.doi.org/10.1038/s41598-019-43373-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6505535PMC
May 2019

The haematopoietic stem cell niche: a new player in cardiovascular disease?

Cardiovasc Res 2019 02;115(2):277-291

Division of Immunometabolism, Haematopoiesis and Leukocyte Biology, Baker Heart & Diabetes Institute, 75 Commercial Road, Melbourne, VIC, Australia.

Haematopoiesis, the process of blood production, can be altered during the initiation or progression of many diseases. Cardiovascular disease (CVD) has been shown to be heavily influenced by changes to the haematopoietic system, including the types and abundance of immune cells produced. It is now well established that innate immune cells are increased in people with CVD, and the mechanisms contributing to this can be vastly different depending on the risk factors or comorbidities present. Many of these changes begin at the level of the haematopoietic stem and progenitor cells (HSPCs) that reside in the bone marrow (BM). In general, the HSPCs and downstream myeloid progenitors are expanded via increased proliferation in the setting of atherosclerotic CVD. However, HSPCs can also be encouraged to leave the BM and colonise extramedullary sites (i.e. the spleen). Within the BM, HSPCs reside in specialized microenvironments, often referred to as a niche. To date in depth studies assessing the damage or dysregulation that occurs in the BM niche in varying CVDs are scarce. In this review, we provide a general overview of the complex components and interactions within the BM niche and how they influence the function of HSPCs. Additionally, we discuss the main findings regarding changes in the HSPC niche that influence the progression of CVD. We hypothesize that understanding the influence of the BM niche in CVD will aid in delineating new pathways for therapeutic interventions.
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http://dx.doi.org/10.1093/cvr/cvy308DOI Listing
February 2019

Modeling human RNA spliceosome mutations in the mouse: not all mice were created equal.

Exp Hematol 2019 02 6;70:10-23. Epub 2018 Nov 6.

St. Vincent's Institute, Fitzroy, Victoria 3065, Australia; Department of Medicine, St. Vincent's Hospital, University of Melbourne, Fitzroy, Victoria 3065, Australia; Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, Victoria 3000, Australia. Electronic address:

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.
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http://dx.doi.org/10.1016/j.exphem.2018.11.001DOI Listing
February 2019

mTORC1 plays an important role in osteoblastic regulation of B-lymphopoiesis.

Sci Rep 2018 09 28;8(1):14501. Epub 2018 Sep 28.

Myeloma Research Laboratory, Adelaide Medical School, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, Australia.

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) 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 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 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.
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http://dx.doi.org/10.1038/s41598-018-32858-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6162303PMC
September 2018

Retinoic Acid Receptor γ Activity in Mesenchymal Stem Cells Regulates Endochondral Bone, Angiogenesis, and B Lymphopoiesis.

J Bone Miner Res 2018 12 8;33(12):2202-2213. Epub 2018 Aug 8.

St Vincent's Institute, Fitzroy, VIC, Australia.

Retinoic acid receptor (RAR) signaling regulates bone structure and hematopoiesis through intrinsic and extrinsic mechanisms. This study aimed to establish how early in the osteoblast lineage loss of RARγ (Rarg) disrupts the bone marrow microenvironment. Bone structure was analyzed by micro-computed tomography (μCT) in Rarg mice and mice with Rarg conditional deletion in Osterix-Cre-targeted osteoblast progenitors or Prrx1-Cre-targeted mesenchymal stem cells. Rarg tibias exhibited less trabecular and cortical bone and impaired longitudinal and radial growth. The trabecular bone and longitudinal, but not radial, growth defects were recapitulated in Prrx1:Rarg mice but not Osx1:Rarg mice. Although both male and female Prrx1:Rarg mice had low trabecular bone mass, males exhibited increased numbers of trabecular osteoclasts and Prrx1:Rarg females had impaired mineral deposition. Both male and female Prrx1:Rarg growth plates were narrower than controls and their epiphyses contained hypertrophic chondrocyte islands. Flow cytometry revealed that male Prrx1:Rarg bone marrow exhibited elevated pro-B and pre-B lymphocyte numbers, accompanied by increased Cxcl12 expression in bone marrow cells. Prrx1:Rarg bone marrow also had elevated megakaryocyte-derived Vegfa expression accompanied by smaller sinusoidal vessels. Thus, RARγ expression by Prrx1-Cre-targeted cells directly regulates endochondral bone formation and indirectly regulates tibial vascularization. Furthermore, RARγ expression by Prrx1-Cre-targeted cells extrinsically regulates osteoclastogenesis and B lymphopoiesis in male mice. © 2018 American Society for Bone and Mineral Research.
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http://dx.doi.org/10.1002/jbmr.3558DOI Listing
December 2018

Protagonist or antagonist? The complex roles of retinoids in the regulation of hematopoietic stem cells and their specification from pluripotent stem cells.

Exp Hematol 2018 09 4;65:1-16. Epub 2018 Jul 4.

St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia; The University of Melbourne, Department of Medicine at St. Vincent's Hospital, Fitzroy, Victoria, Australia. Electronic address:

Hematopoietic stem cells (HSCs) are multipotent cells responsible for the maintenance of the hematopoietic system throughout life. Dysregulation of the balance in HSC self-renewal, death, and differentiation can have serious consequences such as myelodysplastic syndromes or leukemia. All-trans retinoic acid (ATRA), the biologically active metabolite of vitamin A/RA, has been shown to have pleiotropic effects on hematopoietic cells, enhancing HSC self-renewal while also increasing differentiation of more mature progenitors. Furthermore, ATRA has been shown to have key roles in regulating the specification and formation of hematopoietic cells from pluripotent stem cells including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). Here, we summarize the known roles of vitamin A and RA receptors in the regulation of hematopoiesis from HSCs, ES, and iPSCs.
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http://dx.doi.org/10.1016/j.exphem.2018.06.287DOI Listing
September 2018

initiates myeloid bias and myelodysplastic/myeloproliferative syndrome from hemopoietic stem cells.

Blood 2018 08 14;132(6):608-621. Epub 2018 Jun 14.

St. Vincent's Institute, Fitzroy, VIC, Australia.

Mutations in occur in myelodysplastic syndromes (MDS) and MDS/myeloproliferative neoplasms (MPN). mutations cluster at proline 95, with the most frequent mutation being a histidine (P95H) substitution. They undergo positive selection, arise early in the course of disease, and have been identified in age-related clonal hemopoiesis. It is not clear how mutation of modifies hemopoiesis or contributes to the development of myeloid bias or MDS/MPN. Two prior mouse models of mutation have been reported; however, these models do not recapitulate many of the clinical features of -mutant disease and relied on bone marrow (BM) transplantation stress to elicit the reported phenotypes. We describe a new conditional murine mutation model, where the P95H mutation is expressed physiologically and heterozygously from its endogenous locus after Cre activation. Using multiple Cre lines, we demonstrate that during native hemopoiesis (ie, no BM transplantation), the mutation needs to occur within the hemopoietic stem-cell-containing populations to promote myelomonocytic bias and expansion with corresponding transcriptional and RNA splicing changes. With age, nontransplanted animals developed a progressive, transplantable disease characterized by myeloid bias, morphological dysplasia, and monocytosis, hallmarks of MDS/MPN in humans. Analysis of cooccurring mutations within the BM demonstrated the acquisition of additional mutations that are recurrent in humans with mutations. The tractable knock-in model we have generated is highly relevant to human disease and will serve to elucidate the effect of mutations on initiation and maintenance of MDS/MPN.
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http://dx.doi.org/10.1182/blood-2018-04-845602DOI Listing
August 2018

Imaging methods used to study mouse and human HSC niches: Current and emerging technologies.

Bone 2019 02 25;119:19-35. Epub 2018 Apr 25.

Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, London, UK; The Sir Francis Crick Institute, London, UK. Electronic address:

Bone marrow contains numerous different cell types arising from hematopoietic stem cells (HSCs) and non-hematopoietic mesenchymal/skeletal stem cells, in addition to other cell types such as endothelial cells- these non-hematopoietic cells are commonly referred to as stromal cells or microenvironment cells. HSC function is intimately linked to complex signals integrated by their niches, formed by combinations of hematopoietic and stromal cells. Studies of hematopoietic cells have been significantly advanced by flow cytometry methods, enabling the quantitation of each cell type in normal and perturbed situations, in addition to the isolation of these cells for molecular and functional studies. Less is known, however, about the specific niches for distinct developing hematopoietic lineages, or the changes occurring in the niche size and function in these distinct anatomical sites in the bone marrow under stress situations and ageing. Significant advances in imaging technology during the last decade have permitted studies of HSC niches in mice. Additional imaging technologies are emerging that will facilitate the study of human HSC niches in trephine BM biopsies. Here we provide an overview of imaging technologies used to study HSC niches, in addition to highlighting emerging technology that will help us to more precisely identify and characterize HSC niches in normal and diseased states.
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http://dx.doi.org/10.1016/j.bone.2018.04.022DOI Listing
February 2019

Inhibition of Endosteal Vascular Niche Remodeling Rescues Hematopoietic Stem Cell Loss in AML.

Cell Stem Cell 2018 01 21;22(1):64-77.e6. Epub 2017 Dec 21.

Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, SW7 2AZ London, UK; The Francis Crick Institute, WC2A 3LY London, UK. Electronic address:

Bone marrow vascular niches sustain hematopoietic stem cells (HSCs) and are drastically remodeled in leukemia to support pathological functions. Acute myeloid leukemia (AML) cells produce angiogenic factors, which likely contribute to this remodeling, but anti-angiogenic therapies do not improve AML patient outcomes. Using intravital microscopy, we found that AML progression leads to differential remodeling of vasculature in central and endosteal bone marrow regions. Endosteal AML cells produce pro-inflammatory and anti-angiogenic cytokines and gradually degrade endosteal endothelium, stromal cells, and osteoblastic cells, whereas central marrow remains vascularized and splenic vascular niches expand. Remodeled endosteal regions have reduced capacity to support non-leukemic HSCs, correlating with loss of normal hematopoiesis. Preserving endosteal endothelium with the small molecule deferoxamine or a genetic approach rescues HSCs loss, promotes chemotherapeutic efficacy, and enhances survival. These findings suggest that preventing degradation of the endosteal vasculature may improve current paradigms for treating AML.
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http://dx.doi.org/10.1016/j.stem.2017.11.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5766835PMC
January 2018

Mesenchymal lineage cells and their importance in B lymphocyte niches.

Bone 2019 02 26;119:42-56. Epub 2017 Nov 26.

St Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia; The University of Melbourne, Department of Medicine at St Vincent's Hospital, Fitzroy, Victoria, Australia. Electronic address:

Early B lymphopoiesis occurs in the bone marrow and is reliant on interactions with numerous cell types in the bone marrow microenvironment, particularly those of the mesenchymal lineage. Each cellular niche that supports the distinct stages of B lymphopoiesis is unique. Different cell types and signaling molecules are important for the progressive stages of B lymphocyte differentiation. Cells expressing CXCL12 and IL-7 have long been recognized as having essential roles in facilitating progression through stages of B lymphopoiesis. Recently, a number of other factors that extrinsically mediate B lymphopoiesis (positively or negatively) have been identified. In addition, the use of transgenic mouse models to delete specific genes in mesenchymal lineage cells has further contributed to our understanding of how B lymphopoiesis is regulated in the bone marrow. This review will cover the current understanding of B lymphocyte niches in the bone marrow and key extrinsic molecules and signaling pathways involved in these niches, with a focus on how mesenchymal lineage cells regulate B lymphopoiesis.
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http://dx.doi.org/10.1016/j.bone.2017.11.018DOI Listing
February 2019

T-cell acute leukaemia exhibits dynamic interactions with bone marrow microenvironments.

Nature 2016 10 17;538(7626):518-522. Epub 2016 Oct 17.

Department of Life Sciences, Sir Alexander Fleming Building, Imperial College London, London SW7 2AZ, UK.

It is widely accepted that complex interactions between cancer cells and their surrounding microenvironment contribute to disease development, chemo-resistance and disease relapse. In light of this observed interdependency, novel therapeutic interventions that target specific cancer stroma cell lineages and their interactions are being sought. Here we studied a mouse model of human T-cell acute lymphoblastic leukaemia (T-ALL) and used intravital microscopy to monitor the progression of disease within the bone marrow at both the tissue-wide and single-cell level over time, from bone marrow seeding to development/selection of chemo-resistance. We observed highly dynamic cellular interactions and promiscuous distribution of leukaemia cells that migrated across the bone marrow, without showing any preferential association with bone marrow sub-compartments. Unexpectedly, this behaviour was maintained throughout disease development, from the earliest bone marrow seeding to response and resistance to chemotherapy. Our results reveal that T-ALL cells do not depend on specific bone marrow microenvironments for propagation of disease, nor for the selection of chemo-resistant clones, suggesting that a stochastic mechanism underlies these processes. Yet, although T-ALL infiltration and progression are independent of the stroma, accumulated disease burden leads to rapid, selective remodelling of the endosteal space, resulting in a complete loss of mature osteoblastic cells while perivascular cells are maintained. This outcome leads to a shift in the balance of endogenous bone marrow stroma, towards a composition associated with less efficient haematopoietic stem cell function. This novel, dynamic analysis of T-ALL interactions with the bone marrow microenvironment in vivo, supported by evidence from human T-ALL samples, highlights that future therapeutic interventions should target the migration and promiscuous interactions of cancer cells with the surrounding microenvironment, rather than specific bone marrow stroma, to combat the invasion by and survival of chemo-resistant T-ALL cells.
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http://dx.doi.org/10.1038/nature19801DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5164929PMC
October 2016

Adenosine-to-inosine RNA editing by ADAR1 is essential for normal murine erythropoiesis.

Exp Hematol 2016 10 1;44(10):947-63. Epub 2016 Jul 1.

St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia; Department of Medicine, St. Vincent's Hospital, University of Melbourne, Fitzroy, Victoria, Australia. Electronic address:

Adenosine deaminases that act on RNA (ADARs) convert adenosine residues to inosine in double-stranded RNA. In vivo, ADAR1 is essential for the maintenance of hematopoietic stem/progenitors. Whether other hematopoietic cell types also require ADAR1 has not been assessed. Using erythroid- and myeloid-restricted deletion of Adar1, we demonstrate that ADAR1 is dispensable for myelopoiesis but is essential for normal erythropoiesis. Adar1-deficient erythroid cells display a profound activation of innate immune signaling and high levels of cell death. No changes in microRNA levels were found in ADAR1-deficient erythroid cells. Using an editing-deficient allele, we demonstrate that RNA editing is the essential function of ADAR1 during erythropoiesis. Mapping of adenosine-to-inosine editing in purified erythroid cells identified clusters of hyperedited adenosines located in long 3'-untranslated regions of erythroid-specific transcripts and these are ADAR1-specific editing events. ADAR1-mediated RNA editing is essential for normal erythropoiesis.
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http://dx.doi.org/10.1016/j.exphem.2016.06.250DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5035604PMC
October 2016

PDGF-AB and 5-Azacytidine induce conversion of somatic cells into tissue-regenerative multipotent stem cells.

Proc Natl Acad Sci U S A 2016 Apr 4;113(16):E2306-15. Epub 2016 Apr 4.

Lowy Cancer Research Centre, University of New South Wales (UNSW) Australia, Sydney, NSW 2052, Australia; The Prince of Wales Clinical School, UNSW Australia, Sydney, NSW 2052, Australia; Department of Haematology, The Prince of Wales Hospital, Sydney, NSW 2032, Australia

Current approaches in tissue engineering are geared toward generating tissue-specific stem cells. Given the complexity and heterogeneity of tissues, this approach has its limitations. An alternate approach is to induce terminally differentiated cells to dedifferentiate into multipotent proliferative cells with the capacity to regenerate all components of a damaged tissue, a phenomenon used by salamanders to regenerate limbs. 5-Azacytidine (AZA) is a nucleoside analog that is used to treat preleukemic and leukemic blood disorders. AZA is also known to induce cell plasticity. We hypothesized that AZA-induced cell plasticity occurs via a transient multipotent cell state and that concomitant exposure to a receptive growth factor might result in the expansion of a plastic and proliferative population of cells. To this end, we treated lineage-committed cells with AZA and screened a number of different growth factors with known activity in mesenchyme-derived tissues. Here, we report that transient treatment with AZA in combination with platelet-derived growth factor-AB converts primary somatic cells into tissue-regenerative multipotent stem (iMS) cells. iMS cells possess a distinct transcriptome, are immunosuppressive, and demonstrate long-term self-renewal, serial clonogenicity, and multigerm layer differentiation potential. Importantly, unlike mesenchymal stem cells, iMS cells contribute directly to in vivo tissue regeneration in a context-dependent manner and, unlike embryonic or pluripotent stem cells, do not form teratomas. Taken together, this vector-free method of generating iMS cells from primary terminally differentiated cells has significant scope for application in tissue regeneration.
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http://dx.doi.org/10.1073/pnas.1518244113DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4843430PMC
April 2016

Retinoic Acid Receptor γ Regulates B and T Lymphopoiesis via Nestin-Expressing Cells in the Bone Marrow and Thymic Microenvironments.

J Immunol 2016 Mar 3;196(5):2132-44. Epub 2016 Feb 3.

Stem Cell Regulation Unit, St. Vincent's Institute of Medical Research, Fitzroy, Victoria 3065, Australia; and Department of Medicine, St. Vincent's Hospital, Fitzroy, Victoria 3065, Australia

Vitamin A has essential but largely unexplained roles in regulating lymphopoiesis. We have previously shown that retinoic acid receptor (RAR) γ-deficient mice have hematopoietic defects, some phenotypes of which were microenvironment induced. Bone marrow (BM) microenvironment cells identified by either their expression of nestin (Nes) or osterix (Osx) have previously been shown to have roles in regulating lymphopoiesis. We therefore conditionally deleted Rarγ in Nes- or Osx-expressing microenvironment cells. Osx cell-specific deletion of Rarγ had no impact on hematopoiesis. In contrast, deletion of Rarγ in Nes-expressing cells resulted in reductions in peripheral blood B cells and CD4(+) T cells, accompanied by reductions of immature PreB cells in BM. The mice lacking Rarγ in Nes-expressing cells also had smaller thymi, with reductions in double-negative 4 T cell precursors, accompanied by reduced numbers of both TCRβ(low) immature single-positive CD8(+) cells and double-positive T cells. In the thymus, Nes expression was restricted to thymic stromal cells that expressed cerebellar degeneration-related Ag 1 and lacked expression of epithelial cell adhesion molecule. These cells expressed platelet-derived growth factor α and high transcript levels of Rars, Cxcl12, and stem cell factor (Scf). Short-term treatment of mice with all-trans retinoic acid resulted in increased PreB lymphopoiesis in BM and an increase in thymic double-negative 4 T cells, inverse to that observed upon Nes cell-specific deletion of Rarγ. Collectively, these studies show that RARγ is a regulator of B and T lymphopoiesis via Nes-expressing cells in the BM and thymic microenvironments, respectively.
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http://dx.doi.org/10.4049/jimmunol.1501246DOI Listing
March 2016

Arrested Hematopoiesis and Vascular Relaxation Defects in Mice with a Mutation in Dhfr.

Mol Cell Biol 2016 Apr 31;36(8):1222-36. Epub 2016 Mar 31.

Adult Cancer Program, Prince of Wales Clinical School, Lowy Cancer Research Centre, University of New South Wales, Sydney, NSW, Australia Department of Haematology, Prince of Wales Hospital, Sydney, NSW, Australia

Dihydrofolate reductase (DHFR) is a critical enzyme in the folate metabolism pathway and also plays a role in regulating nitric oxide (NO) signaling in endothelial cells. Although both coding and noncoding mutations with phenotypic effects have been identified in the human DHFR gene, no mouse model is currently available to study the consequences of perturbing DHFR in vivo In order to identify genes involved in definitive hematopoiesis, we performed a forward genetic screen and produced a mouse line, here referred to as Orana, with a point mutation in the Dhfr locus leading to a Thr136Ala substitution in the DHFR protein. Homozygote Orana mice initiate definitive hematopoiesis, but expansion of progenitors in the fetal liver is compromised, and the animals die between embryonic day 13.5 (E13.5) and E14.5. Heterozygote Orana mice survive to adulthood but have tissue-specific alterations in folate abundance and distribution, perturbed stress erythropoiesis, and impaired endothelium-dependent relaxation of the aorta consistent with the role of DHFR in regulating NO signaling. Orana mice provide insight into the dual roles of DHFR and are a useful model for investigating the role of environmental and dietary factors in the context of vascular defects caused by altered NO signaling.
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http://dx.doi.org/10.1128/MCB.01035-15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4836279PMC
April 2016

Ciliary neurotrophic factor has intrinsic and extrinsic roles in regulating B cell differentiation and bone structure.

Sci Rep 2015 Oct 21;5:15529. Epub 2015 Oct 21.

Stem Cell Regulation Unit, St. Vincent's Institute of Medical Research, Fitzroy, Vic. 3065, Australia.

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.
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http://dx.doi.org/10.1038/srep15529DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4614391PMC
October 2015

The role of vitamin A and retinoic acid receptor signaling in post-natal maintenance of bone.

J Steroid Biochem Mol Biol 2016 Jan 4;155(Pt A):135-46. Epub 2015 Nov 4.

St Vincent's Institute, Fitzroy, Victoria 3065, Australia; Department of Medicine at St. Vincent's Hospital, The University of Melbourne, Victoria 3065, Australia.

Vitamin A and retinoid derivatives are recognized as morphogens that govern body patterning and skeletogenesis, producing profound defects when in excess. In post-natal bone, both high and low levels of vitamin A are associated with poor bone heath and elevated risk of fractures. Despite this, the precise mechanism of how retinoids induce post-natal bone changes remains elusive. Numerous studies have been performed to discover how retinoids induce these changes, revealing a complex morphogenic regulation of bone through interplay of different cell types. This review will discuss the direct and indirect effects of retinoids on mediators of bone turnover focusing on differentiation and activity of osteoblasts and osteoclasts and explains why some discrepancies in this field have arisen. Importantly, the overall effect of retinoids on the skeleton is highly site-specific, likely due to differential regulation of osteoblasts and osteoclasts at trabecular vs. cortical periosteal and endosteal bone surfaces. Further investigation is required to discover the direct gene targets of retinoic acid receptors (RARs) and molecular mechanisms through which these changes occur. A clear role for RARs in regulating bone is now accepted and the therapeutic potential of retinoids in treating bone diseases has been established.
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http://dx.doi.org/10.1016/j.jsbmb.2015.09.036DOI Listing
January 2016

EphB4 Expressing Stromal Cells Exhibit an Enhanced Capacity for Hematopoietic Stem Cell Maintenance.

Stem Cells 2015 Sep 23;33(9):2838-49. Epub 2015 Jun 23.

Mesenchymal Stem Cell Laboratory, School of Medical Sciences, Faculty of Health Sciences, University of Adelaide, Adelaide, South Australia, Australia.

The tyrosine kinase receptor, EphB4, mediates cross-talk between stromal and hematopoietic populations during bone remodeling, fracture repair and arthritis, through its interactions with the ligand, ephrin-B2. This study demonstrated that transgenic EphB4 mice (EphB4 Tg), over-expressing EphB4 under the control of collagen type-1 promoter, exhibited higher frequencies of osteogenic cells and hematopoietic stem/progenitor cells (HSC), correlating with a higher frequency of long-term culture-initiating cells (LTC-IC), compared with wild type (WT) mice. EphB4 Tg stromal feeder layers displayed a greater capacity to support LTC-IC in vitro, where blocking EphB4/ephrin-B2 interactions decreased LTC-IC output. Similarly, short hairpin RNA-mediated EphB4 knockdown in human bone marrow stromal cells reduced their ability to support high ephrin-B2 expressing CD34(+) HSC in LTC-IC cultures. Notably, irradiated EphB4 Tg mouse recipients displayed enhanced bone marrow reconstitution capacity and enhanced homing efficiency of transplanted donor hematopoietic stem/progenitor cells relative to WT controls. Studies examining the expression of hematopoietic supportive factors produced by stromal cells indicated that CXCL12, Angiopoietin-1, IL-6, FLT-3 ligand, and osteopontin expression were more highly expressed in EphB4 Tg stromal cells compared with WT controls. These findings indicate that EphB4 facilitates stromal-mediated support of hematopoiesis, and constitute a novel component of the HSC niche.
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http://dx.doi.org/10.1002/stem.2069DOI Listing
September 2015

The DNA helicase recql4 is required for normal osteoblast expansion and osteosarcoma formation.

PLoS Genet 2015 Apr 10;11(4):e1005160. Epub 2015 Apr 10.

St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia; Department of Medicine, St. Vincent's Hospital, The University of Melbourne, Fitzroy, Victoria, Australia; ACRF Rational Drug Discovery Centre, St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia.

RECQL4 mutations are associated with Rothmund Thomson Syndrome (RTS), RAPADILINO Syndrome and Baller-Gerold Syndrome. These patients display a range of benign skeletal abnormalities such as low bone mass. In addition, RTS patients have a highly increased incidence of osteosarcoma (OS). The role of RECQL4 in normal adult bone development and homeostasis is largely uncharacterized and how mutation of RECQL4 contributes to OS susceptibility is not known. We hypothesised that Recql4 was required for normal skeletal development and both benign and malignant osteoblast function, which we have tested in the mouse. Recql4 deletion in vivo at the osteoblastic progenitor stage of differentiation resulted in mice with shorter bones and reduced bone volume, assessed at 9 weeks of age. This was associated with an osteoblast intrinsic decrease in mineral apposition rate and bone formation rate in the Recql4-deficient cohorts. Deletion of Recql4 in mature osteoblasts/osteocytes in vivo, however, did not cause a detectable phenotype. Acute deletion of Recql4 in primary osteoblasts or shRNA knockdown in an osteoblastic cell line caused failed proliferation, accompanied by cell cycle arrest, induction of apoptosis and impaired differentiation. When cohorts of animals were aged long term, the loss of Recql4 alone was not sufficient to initiate OS. We then crossed the Recql4fl/fl allele to a fully penetrant OS model (Osx-Cre p53fl/fl). Unexpectedly, the Osx-Cre p53fl/flRecql4fl/fl (dKO) animals had a significantly increased OS-free survival compared to Osx-Cre p53fl/fl or Osx-Cre p53fl/flRecql4fl/+ (het) animals. The extended survival was explained when the Recql4 status in the tumors that arose was assessed, and in no case was there complete deletion of Recql4 in the dKO OS. These data provide a mechanism for the benign skeletal phenotypes of RECQL4 mutation syndromes. We propose that tumor suppression and osteosarcoma susceptibility are most likely a function of mutant, not null, alleles of RECQL4.
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http://dx.doi.org/10.1371/journal.pgen.1005160DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4393104PMC
April 2015

RARγ is a negative regulator of osteoclastogenesis.

J Steroid Biochem Mol Biol 2015 Jun 20;150:46-53. Epub 2015 Mar 20.

St. Vincent's Institute, Fitzroy, Victoria 3065, Australia; Department of Medicine at St. Vincent's Hospital, The University of Melbourne, Victoria 3065, Australia. Electronic address:

Vitamin A is known to influence post-natal bone content, with excess intake being associated with reduced bone mineral density and increased fracture risk. Despite this, the roles retinoids play in regulating osteoclastogenesis, particularly in vivo, remain unresolved. This study therefore aimed to determine the effect of loss of retinoic acid receptors (RAR)α or RARγ on bone mass (analyzed by histomorphometry and dual-energy X-ray absorptiometry) and osteoclastogenesis in mice in vivo. RARγ null mice had significantly less trabecular bone at 8 weeks of age compared to wildtype littermates. In contrast, no change in trabecular bone mass was detected in RARα null mice at this age. Further histomorphometric analysis revealed a significantly greater osteoclast surface in bones from 8-week-old RARγ null male mice. This in vivo effect was cell lineage autonomous, and was associated with increased osteoclastogenesis in vitro from hematopoietic cells obtained from 8-week-old RARγ null male mice. The use of highly selective agonists in RANKL-induced osteoclast differentiation of wild type mouse whole bone marrow cells and RAW264.7 cells in vitro showed a stronger inhibitory effect of RARγ than RARα agonists, suggesting that RARγ is a more potent inhibitor of osteoclastogenesis. Furthermore, NFAT activation was also more strongly inhibited by RARγ than RARα agonists. While RARα and RARγ antagonists did not significantly affect osteoclast numbers in vitro, larger osteoclasts were observed in cultures stimulated with the antagonists, suggesting increased osteoclast fusion. Further investigation into the effect of retinoids in vivo revealed that oral administration of 5mg/kg/day ATRA for 10 days protected against bone loss induced by granulocyte colony-stimulating factor (G-CSF) by inhibiting the pro-osteoclastogenic action of G-CSF. Collectively, our data indicates a physiological role for RARγ as a negative regulator of osteoclastogenesis in vivo and in vitro, and reveals distinct influences of RARα and RARγ in bone structure regulation.
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http://dx.doi.org/10.1016/j.jsbmb.2015.03.005DOI Listing
June 2015

Wnt inhibitory factor 1 (WIF1) is a marker of osteoblastic differentiation stage and is not silenced by DNA methylation in osteosarcoma.

Bone 2015 Apr 5;73:223-32. Epub 2015 Jan 5.

Stem Cell Regulation Unit, St. Vincent's Institute of Medical Research, Fitzroy, Australia; Department of Medicine, St. Vincent's Hospital, University of Melbourne, Fitzroy, Australia. Electronic address:

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.
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http://dx.doi.org/10.1016/j.bone.2014.12.063DOI Listing
April 2015

Myelosuppressive therapies significantly increase pro-inflammatory cytokines and directly cause bone loss.

J Bone Miner Res 2015 May;30(5):886-97

Stem Cell Regulation Unit, St Vincent's Institute of Medical Research, Fitzroy, Australia.

Skeletal-related events resulting from accelerated bone loss are common complications in patients treated for a range of cancers. However, the mechanisms and rate of bone loss after myelosuppression are unclear. We, therefore, investigated this in mice and humans. We treated mice with different myelosuppressive therapies (chemotherapy or irradiation with or without transplantation) and studied their effects on bone structure. Myelosuppression of mice rapidly caused an increase in bone resorption that was not matched by bone formation. The resultant significant and persistent bone loss early after therapy was associated with increased inflammatory cytokines, in particular, monocyte chemoattractant protein 1 (MCP1). Therapy-induced bone loss was prevented with a single dose of the bisphosphonate zoledronic acid (ZA), administered before myelosuppression. Importantly, ZA treatment of mice did not impair hematopoiesis, including hematopoietic stem cell function. Furthermore, examination of serum from patients before and after autologous or allogeneic stem cell transplantion (SCT) revealed altered levels of bone turnover markers and elevated inflammatory cytokines. MCP1 levels in serum obtained between days 7 and 14 post-SCT positively correlated with bone loss observed at 100 days after allogeneic SCT. Similar to that observed in our studies in mice, the bone loss was long term, persisting at 12 months post-SCT. Furthermore, patients who received chemotherapy less than 100 days before SCT had significantly more bone loss at the hip. In these patients, serum levels of MCP1, but not routine biomarkers of bone turnover, including C-terminal cross-linking telopeptide of type-1 collagen (β-CTx), positively correlated with their bone loss. Hence, myelosuppressive therapies increase inflammation and directly contribute to bone loss. Administration of an osteoclast inhibitor before the initiation of cancer therapy is likely to have the best outcome in preventing bone loss in patients with cancer.
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http://dx.doi.org/10.1002/jbmr.2415DOI Listing
May 2015

The Rothmund-Thomson syndrome helicase RECQL4 is essential for hematopoiesis.

J Clin Invest 2014 Aug 24;124(8):3551-65. Epub 2014 Jun 24.

Mutations within the gene encoding the DNA helicase RECQL4 underlie the autosomal recessive cancer-predisposition disorder Rothmund-Thomson syndrome, though it is unclear how these mutations lead to disease. Here, we demonstrated that somatic deletion of Recql4 causes a rapid bone marrow failure in mice that involves cells from across the myeloid, lymphoid, and, most profoundly, erythroid lineages. Apoptosis was markedly elevated in multipotent progenitors lacking RECQL4 compared with WT cells. While the stem cell compartment was relatively spared in RECQL4-deficent mice, HSCs from these animals were not transplantable and even selected against. The requirement for RECQL4 was intrinsic in hematopoietic cells, and loss of RECQL4 in these cells was associated with increased replicative DNA damage and failed cell-cycle progression. Concurrent deletion of p53, which rescues loss of function in animals lacking the related helicase BLM, did not rescue BM phenotypes in RECQL4-deficient animals. In contrast, hematopoietic defects in cells from Recql4Δ/Δ mice were fully rescued by a RECQL4 variant without RecQ helicase activity, demonstrating that RECQL4 maintains hematopoiesis independently of helicase activity. Together, our data indicate that RECQL4 participates in DNA replication rather than genome stability and identify RECQL4 as a regulator of hematopoiesis with a nonredundant role compared with other RecQ helicases.
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http://dx.doi.org/10.1172/JCI75334DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4109528PMC
August 2014

Src family kinases and their role in hematological malignancies.

Leuk Lymphoma 2015 Mar 21;56(3):577-86. Epub 2015 Jan 21.

Haematology Department and Victorian Cancer Cytogenetics Service, St Vincent's Hospital , Fitzroy , Australia.

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.
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http://dx.doi.org/10.3109/10428194.2014.907897DOI Listing
March 2015

Erythroid-extrinsic regulation of normal erythropoiesis by retinoic acid receptors.

Br J Haematol 2014 Jan 24;164(2):280-5. Epub 2013 Sep 24.

Department of Medicine at St. Vincent's Hospital, St. Vincent's Institute of Medical Research, University of Melbourne, Fitzroy, Vic., Australia.

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.
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http://dx.doi.org/10.1111/bjh.12578DOI Listing
January 2014