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Supplementary Table S3 from Down-Regulation of hsa-miR-10a in Chronic Myeloid Leukemia CD34+ Cells Increases USF2-Mediated Cell Growth

Supplementary Figures S1-S6 from Down-Regulation of hsa-miR-10a in Chronic Myeloid Leukemia CD34+ Cells Increases USF2-Mediated Cell Growth

Fibroblast activation includes differentiation to myofibroblasts and is a key feature of organ fibrosis. The Notch pathway has been involved in myofibroblast differentiation in several tissues, inc...

Metabolic alterations in cancer represent convergent effects of oncogenic mutations. We hypothesized that a metabolism-restricted genetic screen, comparing normal primary mouse hematopoietic cells and their malignant counterparts in an ex vivo system mimicking the bone marrow microenvironment, would define distinctive vulnerabilities in acute myeloid leukemia (AML). Leukemic cells, but not their normal myeloid counterparts, depended on the aldehyde dehydrogenase 3a2 (Aldh3a2) enzyme that oxidizes long-chain aliphatic aldehydes to prevent cellular oxidative damage. Aldehydes are by-products of increased oxidative phosphorylation and nucleotide synthesis in cancer and are generated from lipid peroxides underlying the non–caspase-dependent form of cell death, ferroptosis. Leukemic cell dependence on Aldh3a2 was seen across multiple mouse and human myeloid leukemias. Aldh3a2 inhibition was synthetically lethal with glutathione peroxidase-4 (GPX4) inhibition; GPX4 inhibition is a known trigger of ferroptosis that by itself minimally affects AML cells. Inhibiting Aldh3a2 provides a therapeutic opportunity and a unique synthetic lethality to exploit the distinctive metabolic state of malignant cells.

A Smart City based on data acquisition, handlingand intelligent analysis requires efficient design and implementationof the respective AI technologies and the underlyinginfrastructure for seamlessly analyzing the large amounts of datain real-time. The EU project MARVEL will research solutionsthat can improve the integration of multiple data sources in aSmart City environment for harnessing the advantages rooted inmultimodal perception of the surrounding environment.

Eradicating leukemia requires a deep understanding of the interaction between leukemic cells and their protective microenvironment. The CXCL12/CXCR4 axis has been postulated as a critical pathway dictating leukemia stem cell (LSC) chemoresistance in AML due to its role in controlling cellular egress from the marrow. Nevertheless, the cellular source of CXCL12 in the acute myeloid leukemia (AML) microenvironment and the mechanism by which CXCL12 exerts its protective role in vivo remain unresolved. Here, we show that CXCL12 produced by Prx1+ mesenchymal cells but not by mature osteolineage cells provide the necessary cues for the maintenance of LSCs in the marrow of an MLL::AF9-induced AML model. Prx1+ cells promote survival of LSCs by modulating energy metabolism and the REDOX balance in LSCs. Deletion of Cxcl12 leads to the accumulation of reactive oxygen species and DNA damage in LSCs, impairing their ability to perpetuate leukemia in transplantation experiments, a defect that can be attenuated by antioxidant therapy. Importantly, our data suggest that this phenomenon appears to be conserved in human patients. Hence, we have identified Prx1+ mesenchymal cells as an integral part of the complex niche-AML metabolic intertwining, pointing towards CXCL12/CXCR4 as a target to eradicate parenchymal LSCs in AML.

Part of this work has been developed in the context of the project "SEMULIN" (German project number 19A20012D) and financed by the German Federal Ministry for Economic Affairs and Energy (BMWi), and the project P20-00265 funded by the "Junta de Andalucia" of Spain., This work studies the feasibility of a novel two-step algorithm for infrastructure and object positioning, using pairwise distances. The proposal is based on the optimization algorithms, Scaling-by-Majorizing-a-Complicated-Function and the Limited-Memory-Broyden-Fletcher- Goldfarb-Shannon. A qualitative evaluation of these algorithms is performed for 3D positioning. As the final stage, smoothing filtering techniques are applied to estimate the trajectory, from the previously obtained positions. This approach can also be used as a synthetic gesture data generator framework. This framework is independent from the hardware and can be used to simulate the estimation of trajectories from noisy distances gathered with a large range of sensors by modifying the noise properties of the initial distances. The framework is validated, using a system of ultrasound transceivers. The results show this framework to be an efficient and simple positioning and filtering approach, accurately reconstructing the real path followed by the mobile object while maintaining low latency. Furthermore, these capabilities can be exploited by using the proposed algorithms for synthetic data generation, as demonstrated in this work, where synthetic ultrasound gesture data are generated., project "SEMULIN" 19A20012D, German Federal Ministry for Economic Affairs and Energy (BMWi), Junta de Andalucia P20-00265

Understanding the regulation of normal and malignant human hematopoiesis requires comprehensive cell atlas of the hematopoietic stem cell (HSC) regulatory microenvironment. Here, we develop a tailored bioinformatic pipeline to integrate public and proprietary single-cell RNA sequencing (scRNA-seq) datasets. As a result, we robustly identify for the first time 14 intermediate cell states and 11 stages of differentiation in the endothelial and mesenchymal BM compartments, respectively. Our data provide the most comprehensive description to date of the murine HSC-regulatory microenvironment and suggests a higher level of specialization of the cellular circuits than previously anticipated. Furthermore, this deep characterization allows to infer conserved features in human, suggesting that the layers of microenvironmental regulation of hematopoiesis may also be shared between species. Our resource and methodology are a steppingstone towards a comprehensive cell atlas of the BM microenvironment.

Extracellular vesicles transfer complex biologic material between cells, whose role in in-vivo organismal physiology is poorly defined. Here, we demonstrate that osteoblastic cells in the bone marrow elaborate extracellular vesicles that are taken up by hematopoietic progenitor cells in vivo. Genotoxic or infectious stress rapidly increased stromal-derived extracellular vesicle transfer to granulocyte-monocyte progenitors. Stimulating osteoblastic cells with parathyroid hormone or activating its receptor enhanced extracellular vesicle transfer, myeloid recovery post radiation and improved animal survival from Candida sepsis. The extracellular vesicles contained tiRNAs known to modulate protein translation. 5’-ti-Pro-CGG-1 was preferentially abundant in osteoblast-derived extracellular vesicles and when transferred to granulocyte macrophage progenitors, increased protein translation, cell proliferation and myeloid differentiation. Therefore, EV-mediated tiRNA transfer provides a stress modulated signaling axis distinct from conventional cytokine-driven stress responses.One sentence summaryStress regulated tiRNA transfer alters hematopoiesis

Loss of protein quality is a driving force of aging1. The accumulation of misfolded proteins represents a vulnerability for long-lived cells, such as haematopoietic stem cells. How these cells, which have the ability to reconstitute all haematopoietic lineages throughout life2, maintain their regenerative potential and avert the effects of aging is poorly understood. Here, we determined the protein content in haematopoietic stem and progenitor cells to identify prevalent chaperones that support proteome integrity. We identified Peptidyl-Prolyl Isomerase A (PPIA or Cyclophilin A) as the dominant cytosolic foldase in this cell population. Loss of PPIA accelerated aging in the mouse stem cell compartment. In an effort to define targets of PPIA, we found that RNA- and DNA-binding proteins are common substrates of this chaperone. These proteins are enriched in intrinsically disordered regions (IDRs), which can catalyse protein condensation3. Isomerized target prolines are almost exclusively located within IDRs. We discovered that over 20% of PPIA client proteins are known to participate in liquid-liquid phase separation, enabling the formation of supramolecular membrane-less organelles. Using the poly-A binding protein PABPC1 as an example, we demonstrate that PPIA promotes phase separation of ribonucleoprotein particles, thereby increasing cellular stress resistance. Haematopoietic stem cell aging is associated with a decreased expression of PPIA and reduced synthesis of intrinsically disordered proteins. Our findings link the ubiquitously expressed chaperone PPIA to phase transition and identify macromolecular condensation as a potential determinant of the aging process in haematopoietic stem cells.

Hematopoietic stem cell transplantation (HSCT) is a curative therapy for blood and immune diseases with potential for many settings beyond current standard-of-care. Broad HSCT application is currently precluded largely due to morbidity and mortality associated with genotoxic irradiation or chemotherapy conditioning. Here we show that a single dose of a CD117-antibody-drug-conjugate (CD117-ADC) to saporin leads to > 99% depletion of host HSCs, enabling rapid and efficient donor hematopoietic cell engraftment. Importantly, CD117-ADC selectively targets hematopoietic stem cells yet does not cause clinically significant side-effects. Blood counts and immune cell function are preserved following CD117-ADC treatment, with effective responses by recipients to both viral and fungal challenges. These results suggest that CD117-ADC-mediated HSCT pre-treatment could serve as a non-myeloablative conditioning strategy for the treatment of a wide range of non-malignant and malignant diseases, and might be especially suited to gene therapy and gene editing settings in which preservation of immunity is desired., Hematopoietic stem cell (HSC) transplantation is a desirable treatment for many non-malignant and malignant diseases, but its use requires preconditioning of recipients with irradiation or chemotherapy that often induces high toxicity. Here the authors show that antibody-drug-conjugate to CD117, a HSC marker, allows specific and efficient preconditioning for HSC therapy.

Stem cells reside in specialized anatomical locations called niches where supportive stromal cells and the extracellular matrix (ECM) regulate their self-renewal and differentiation. This review explores the critical roles of the ECM in stem cell maintenance in tissue homeostasis, aging, and disease. It is well established that ECM proteins and their biomechanical properties control stem cell fate. In addition to specific molecular interactions, the ECM composition determines the topology and stiffness of the substrate, which also regulate stem cell behavior. Changes in the ECM during aging and disease can impair cell-ECM interactions and ultimately contribute to aging and disease pathogenesis. A deeper understanding of the mechanisms by which the ECM regulates stem cell behavior in health, as well as during aging and in disease states, will facilitate the development of therapeutic strategies. These therapies should focus on recovering normal matrix synthesis and deposition aiming at promoting endogenous repair.

Extracellular vesicles (EV) transfer complex biologic material between cells. However the role of this process in in-vivo organismal physiology is poorly defined. Here, we demonstrate that osteoblastic cells in the bone marrow elaborate extracellular vesicles that are taken up by hematopoietic progenitor cells in vivo. Genotoxic or infectious stress rapidly increased stromal-derived extracellular vesicle transfer to granulocyte-monocyte progenitors. Stimulating osteoblastic cells with parathyroid hormone or activating the parathyroid hormone receptor enhanced extracellular vesicle transfer, myeloid recovery post radiation and improved animal survival from Candida sepsis. The extracellular vesicles contained tiRNAs known to modulate protein translation. 5’-ti-Pro-CGG-1 was preferentially abundant in osteoblast-derived extracellular vesicles and when transferred to granulocyte- monocyte progenitors, increased protein translation, cell proliferation and myeloid differentiation. Therefore, EV-mediated tiRNA transfer provides a stress modulated signaling axis distinct from conventional cytokine-driven stress responses.

Understanding the regulation of normal and malignant human hematopoiesis requires a comprehensive cell atlas of the hematopoietic stem cell (HSC) regulatory microenvironment. Recent studies using scRNA-seq technologies have shed light on the organization of the hematopoietic regulatory microenvironment in the mouse. These studies have resolved some of the controversies regarding the overlap of stromal populations, the description of certain discrete stromal cells as professional, hematopoietic cytokine-producing populations, but also helped to delineate the relationship between specific stromal cell types in the murine BM. Nevertheless, these studies are limited by the number of cells sequenced, potentially hampering our ability to resolve the full spectrum of cellular states and differentiation stages that define the stromal BM microenvironment. Further, knowledge on the conservation of the cellular composition in the human BM stroma is in its infancy due to the difficulty of obtaining high-quality samples with sufficient stromal cell numbers from healthy individuals. This leaves us with two outstanding challenges; how to piece together such different fragments towards a comprehensive molecular atlas and to what extent such an atlas in mice is conserved in the human bone marrow. Here, we dissect the intrinsic organization and the heterogeneity within the endothelial (EC) and mesenchymal cell populations (MSC) governing the BM microenvironment in mouse and human. This was accomplished through customized bioinformatics integration of multiple scRNA-seq datasets along with the inclusion of over 50.000 murine and human bone marrow stromal cells. By these means, we were able to identify new subsets of MSC and EC, but more importantly, to define new molecular markers to identify highly specialized subpopulations of cells in the murine BM microenvironment. Pathway enrichment analysis unveiled multiple, potentially transient cell states defined by differential gene expression and the enrichment of specific functional characteristics. Importantly, 14 EC subsets were characterized by enrichment in pathways known to be essential for endothelial homeostasis maintenance, demonstrating a high degree of specialization in the endothelium. Similarly, 11 transient cell states in the MSC compartment were defined and characterized by their differentiation capacity. Importantly, our deep deconvolution of the heterogeneous mesenchymal and endothelial compartments became feasible only by integrating multiple datasets. Furthermore, based on the knowledge generated in the mouse, we were able to describe how much of the information and targets from the mouse can be of interest in human characterization. This analysis identified the expression of the human orthologs to the murine cluster-defining genes with different degrees of enrichment in the endothelium and mesenchyme. Moreover, some of these shared genes in mice and human stromal cells corresponded to the GO-defining genes of the different clusters identified in the mouse. These findings suggest a significant degree of conservation regarding the cellular states that define the stromal microenvironment in mouse and human. Although additional studies and improved processing of human samples will be required for deep characterization of the human BM microenvironment, these preliminary results validate our integrative cross-species approach. Taken together, our study provides a deeper understanding of the composition and specialization of the BM microenvironment and point towards a significant degree of conservation between species. Moreover, we demonstrate the usefulness of the multi-dataset integration and the customized clustering approach used in our study to improve the resolution of complex tissues and organs. This approach promises to aid in the construction of cell atlases by reducing the resources associated with sequencing that a single lab will need to invest in order to obtain meaningful depth in single-cell analysis. Future studies integrating genome, transcriptome, epigenome, proteome, and anatomical positioning together with functional assays to correlate descriptive phenotypes with functional data will help fully resolve the composition, regulation, and connectivity in the BM microenvironment in health and disease. Figure 1 Figure 1. Disclosures Paiva: Adaptive, Amgen, Bristol-Myers Squibb-Celgene, Janssen, Kite Pharma, Sanofi and Takeda: Honoraria; Bristol-Myers Squibb-Celgene, Janssen, and Sanofi: Consultancy; Celgene, EngMab, Roche, Sanofi, Takeda: Research Funding. Saez: Magenta Therapeutics: Patents & Royalties. Prosper: BMS-Celgene: Honoraria, Research Funding; Janssen: Honoraria; Oryzon: Honoraria.

Despite the bone marrow microenvironment being widely recognised as a key player in cancer research, the current animal models that represent a human haematopoietic system lack the contribution of the humanised marrow microenvironment. Here we describe a murine model that relies on the combination of an orthotopic humanised tissue-engineered bone construct (ohTEBC) with patient-specific bone marrow (BM) cells to create a humanised bone marrow (hBM) niche capable of supporting the engraftment of human haematopoietic cells. Results showed that this model supports the engraftment of human CD34+ cells from a healthy BM with human haematopoietic cells migrating into the mouse BM, human BM compartment, spleen and peripheral blood. We compared these results with the engraftment capacity of human CD34+ cells obtained from patients with multiple myeloma (MM). We demonstrated that CD34+ cells derived from a diseased BM had a reduced engraftment potential compared to healthy patients and that a higher cell dose is required to achieve engraftment of human haematopoietic cells in peripheral blood. Finally, we observed that hematopoietic cells obtained from the mobilised peripheral blood of patients yields a higher number of CD34+, overcoming this problem. In conclusion, this humanised mouse model has potential as a unique and patient-specific pre-clinical platform for the study of tumour&ndash, microenvironment interactions, including human bone and haematopoietic cells, and could, in the future, serve as a drug testing platform.

Hematopoietic stem cell transplantation (HSCT) offers curative therapy for patients with hemoglobinopathies, congenital immunodeficiencies, and other conditions, possibly including AIDS. Autologous HSCT using genetically corrected cells would avoid the risk of graft-versus-host disease (GVHD), but the genotoxicity of conditioning remains a substantial barrier to the development of this approach. Here we report an internalizing immunotoxin targeting the hematopoietic-cell-restricted CD45 receptor that effectively conditions immunocompetent mice. A single dose of the immunotoxin, CD45-saporin (SAP), enabled efficient (>90%) engraftment of donor cells and full correction of a sickle-cell anemia model. In contrast to irradiation, CD45-SAP completely avoided neutropenia and anemia, spared bone marrow and thymic niches, enabling rapid recovery of T and B cells, preserved anti-fungal immunity, and had minimal overall toxicity. This non-genotoxic conditioning method may provide an attractive alternative to current conditioning regimens for HSCT in the treatment of non-malignant blood diseases.

Production of the cells that ultimately populate the thymus to generate α/β T cells has been controversial, and their molecular drivers remain undefined. Here, we report that specific deletion of bone-producing osteocalcin (Ocn)-expressing cells in vivo markedly reduces T-competent progenitors and thymus-homing receptor expression among bone marrow hematopoietic cells. Decreased intrathymic T cell precursors and decreased generation of mature T cells occurred despite normal thymic function. The Notch ligand DLL4 is abundantly expressed on bone marrow Ocn+ cells, and selective depletion of DLL4 from these cells recapitulated the thymopoietic abnormality. These data indicate that specific mesenchymal cells in bone marrow provide key molecular drivers enforcing thymus-seeding progenitor generation and thereby directly link skeletal biology to the production of T cell–based adaptive immunity.

The glycosyltransferase gene, Ext1, is essential for heparan sulfate production. Induced deletion of Ext1 selectively in Mx1-expressing bone marrow (BM) stromal cells, a known population of skeletal stem/progenitor cells, in adult mice resulted in marked changes in hematopoietic stem and progenitor cell (HSPC) localization. HSPC egressed from BM to spleen after Ext1 deletion. This was associated with altered signaling in the stromal cells and with reduced vascular cell adhesion molecule 1 production by them. Further, pharmacologic inhibition of heparan sulfate mobilized qualitatively more potent and quantitatively more HSPC from the BM than granulocyte colony-stimulating factor alone, including in a setting of granulocyte colony-stimulating factor resistance. The reduced presence of endogenous HSPC after Ext1 deletion was associated with engraftment of transfused HSPC without any toxic conditioning of the host. Therefore, inhibiting heparan sulfate production may provide a means for avoiding the toxicities of radiation or chemotherapy in HSPC transplantation for nonmalignant conditions.

SummaryD-type cyclins (D1, D2, and D3) are components of the mammalian core cell-cycle machinery and function to drive cell proliferation. Here, we report that D-cyclins perform a rate-limiting antiapoptotic function in vivo. We found that acute shutdown of all three D-cyclins in bone marrow of adult mice resulted in massive apoptosis of all hematopoietic cell types. We demonstrate that adult hematopoietic stem cells are particularly dependent on D-cyclins for survival and that they are especially sensitive to cyclin D loss. Surprisingly, we found that the antiapoptotic function of D-cyclins also operates in quiescent hematopoietic stem and progenitor cells. Our analyses revealed that D-cyclins repress the expression of the death receptor Fas and its ligand, FasL. Acute ablation of D-cyclins upregulated these proapoptotic genes and led to Fas- and caspase 8-dependent apoptosis. These results reveal an unexpected function of cell-cycle proteins in controlling apoptosis in normal cell homeostasis.

The bone marrow (BM) niche, is an extrinsic regulator of hematopoietic stem and progenitor cells (HSPCs) (Morrison and Scadden 2014). The niche can drive disease and loss of HSPC function (Raaijmakers et al., 2010; Kode et al., 2014; Dong et al., 2016). Of particular interest, deletion in specific niche cells of the small RNA processing enzymes, Dicer1 and Angiogenin (Ang1) resulted in hematopoietic transformation (Raaijmakers et al., 2010) and loss of HSC quiescence (Goncalves et al., 2016), respectively. We tested mechanisms by which small non-coding RNAs (sncRNA) from niche cells might contribute to HSPC regulation. The transfer of cytoplasmic contents from specific mesenchymal subsets to wild type (WT) transplanted hematopoietic cells was evaluated by GFP. Osteoblastic cell reporter mice (Ocn-GFP, Col1-GFP) transferred 40-fold more GFP to HSPC than mesenchymal stem cells (Nes-GFP) or osteoprogenitors (Osx-GFP). GFP cannot transfer through gap junctions, however 100nM extracellular vesicles (EVs) labeled with the endocytic marker TSG-101 and GFP were found in Ocn-GFP bone marrow plasma. Granulocyte macrophage progenitor (GMPs) cells were the major hematopoietic recipients of osteoblast derived EVs (Fig. 1A). Small RNA analysis of mouse BM EVs demonstrated >85% were tRNA (Fig. 1B) while Northern blot (NB) revealed both tRNAs and stress induced RNAs (tiRNAs) (Fig. 1C). tRNAs were evident in EVs and in EV generating and recipient cells, while tiRNAs were highly enriched in EVs compared to cells (Fig. 1C). Extracellular vesicle recipient and non-recipient GMPs (GMP[GFP+] and GMP[GFP-]) respectively demonstrated a 2-fold enrichment in reads mapping to tRNAs in GMP[GFP+]. Principle component analysis demonstrated that the two populations are distinct in their tRNA content. In addition, twelve specific tRNAs were present at a significantly higher levels in GMP[GFP+]. Gene expression analysis of GMP[GFP+]and GMP[GFP-] revealed an enrichment of protein translation and cell cycle related functions in GMP[GFP+] which were validated using an in vivo protein translation assay and cell cycle analyses. Synthetic oligos corresponding to the sequence of top ten tiRNAs that are enriched in GMP[GFP+] were transfected into primary GMPs. 5'-Pro-CGG-1 and 5'-Cys-GCA-27 increased the rate of protein translation and cellular proliferation in transfected GMPs (Fig. 1D-E). The physiologic relevance of EV transfer was assessed using two stress states, systemic Candida albicans infection and low dose gamma irradiation. The frequency of GMP[GFP+] increased in both states in concert with increased cell proliferation. Therefore, EV transfer of sncRNAs from niche to hematopoietic progenitors in vivo is a rapid means of conveying information between cells. It alters progenitor protein translation and proliferation in a manner responsive to stress. The transfer of 5'tiRNA EV from specific niche cells to specific hematopoietic cells is an additional mechanism for niche regulation of blood cell production. Disclosures Sykes: Clear Creek Bio: Equity Ownership, Other: Co-Founder. Scadden:Clear Creek Bio: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Magenta Therapeutics: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Fog Pharma: Consultancy; Agios Pharmaceuticals: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; LifeVaultBio: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Editas Medicine: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Bone Therapeutics: Consultancy; Novartis: Other: Sponsored research; Fate Therapeutics: Consultancy, Equity Ownership; Red Oak Medicines: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees.

Stem cells determine homeostasis and repair of many tissues and are increasingly recognized as functionally heterogeneous. To define the extent of—and molecular basis for—heterogeneity, we overlaid functional, transcriptional, and epigenetic attributes of hematopoietic stem cells (HSCs) at a clonal level using endogenous fluorescent tagging. Endogenous HSC had clone-specific functional attributes over time in vivo. The intra-clonal behaviors were highly stereotypic, conserved under the stress of transplantation, inflammation, and genotoxic injury, and associated with distinctive transcriptional, DNA methylation, and chromatin accessibility patterns. Further, HSC function corresponded to epigenetic configuration but not always to transcriptional state. Therefore, hematopoiesis under homeostatic and stress conditions represents the integrated action of highly heterogeneous clones of HSC with epigenetically scripted behaviors. This high degree of epigenetically driven cell autonomy among HSCs implies that refinement of the concepts of stem cell plasticity and of the stem cell niche is warranted.

Tissue homeostasis in complex organisms is accomplished through interactions between cells, communication through circulating or locally distributed chemicals, and biophysical properties of their environment. Stem cells are preserved in specific anatomical sites known as niches where these cellular, biochemical, and biophysical interactions drive tissue maintenance and regeneration. Our understanding of mammalian stem cell niches has advanced greatly in recent years; yet, as available technology becomes more sophisticated, several well-accepted paradigms are being discovered to be less than generalizable or being challenged altogether. In this chapter we summarize what is known about the three components of the niche to which stem cells and their neoplastic counterparts are native: cellular, biochemical, and biophysical. As we apply improving technologies to our age-old questions and ask new ones, our understanding of this complex ecosystem is likely to evolve and will hopefully yield insights that are of benefit to patients.

Alternative splicing generates a diversity of messenger RNA (mRNA) transcripts from a single mRNA precursor and contributes to the complexity of our proteome. Splicing is perturbed by a variety of mechanisms in cancer. Recurrent mutations in splicing factors have emerged as a hallmark of several hematologic malignancies. Splicing factor mutations tend to occur in the founding clone of myeloid cancers, and these mutations have recently been identified in blood cells from normal, healthy elderly individuals with clonal hematopoiesis who are at increased risk of subsequently developing a hematopoietic malignancy, suggesting that these mutations contribute to disease initiation. Splicing factor mutations change the pattern of splicing in primary patient and mouse hematopoietic cells and alter hematopoietic differentiation and maturation in animal models. Recent developments in this field are reviewed here, with an emphasis on the clinical consequences of splicing factor mutations, mechanistic insights from animal models, and implications for development of novel therapies targeting the precursor mRNA splicing pathway.

Anemia of inflammation develops in settings of chronic inflammatory, infectious, or neoplastic disease. In this highly prevalent form of anemia, inflammatory cytokines, including IL-6, stimulate hepatic expression of hepcidin, which negatively regulates iron bioavailability by inactivating ferroportin. Hepcidin is transcriptionally regulated by IL-6 and bone morphogenetic protein (BMP) signaling. We hypothesized that inhibiting BMP signaling can reduce hepcidin expression and ameliorate hypoferremia and anemia associated with inflammation. In human hepatoma cells, IL-6–induced hepcidin expression, an effect that was inhibited by treatment with a BMP type I receptor inhibitor, LDN-193189, or BMP ligand antagonists noggin and ALK3-Fc. In zebrafish, the induction of hepcidin expression by transgenic expression of IL-6 was also reduced by LDN-193189. In mice, treatment with IL-6 or turpentine increased hepcidin expression and reduced serum iron, effects that were inhibited by LDN-193189 or ALK3-Fc. Chronic turpentine treatment led to microcytic anemia, which was prevented by concurrent administration of LDN-193189 or attenuated when LDN-193189 was administered after anemia was established. Our studies support the concept that BMP and IL-6 act together to regulate iron homeostasis and suggest that inhibition of BMP signaling may be an effective strategy for the treatment of anemia of inflammation.

MicroRNAs (miRNA) are small noncoding, single-stranded RNAs that inhibit gene expression at a posttranscriptional level, whose abnormal expression has been described in different tumors. The aim of our study was to identify miRNAs potentially implicated in chronic myeloid leukemia (CML). We detected an abnormal miRNA expression profile in mononuclear and CD34+ cells from patients with CML compared with healthy controls. Of 157 miRNAs tested, hsa-miR-10a, hsa-miR-150, and hsa-miR-151 were down-regulated, whereas hsa-miR-96 was up-regulated in CML cells. Down-regulation of hsa-miR-10a was not dependent on BCR-ABL1 activity and contributed to the increased cell growth of CML cells. We identified the upstream stimulatory factor 2 (USF2) as a potential target of hsa-miR-10a and showed that overexpression of USF2 also increases cell growth. The clinical relevance of these findings was shown in a group of 85 newly diagnosed patients with CML in which expression of hsa-miR-10a was down-regulated in 71% of the patients, whereas expression of USF2 was up-regulated in 60% of the CML patients, with overexpression of USF2 being significantly associated with decreased expression of hsa-miR-10a (P = 0.004). Our results indicate that down-regulation of hsa-miR-10a may increase USF2 and contribute to the increase in cell proliferation of CML implicating a miRNA in the abnormal behavior of CML. (Mol Cancer Res 2008;6(12):1830–40)

Tle1 (transducin-like enhancer of split 1) is a corepressor that interacts with a variety of DNA-binding transcription factors and has been implicated in many cellular functions; however, physiological studies are limited. Tle1-deficient (Tle1(Δ/Δ)) mice, although grossly normal at birth, exhibit skin defects, lung hypoplasia, severe runting, poor body condition, and early mortality. Tle1(Δ/Δ) mice display a chronic inflammatory phenotype with increased expression of inflammatory cytokines and chemokines in the skin, lung, and intestine and increased circulatory IL-6 and G-CSF, along with a hematopoietic shift toward granulocyte macrophage progenitor and myeloid cells. Tle1(Δ/Δ) macrophages produce increased inflammatory cytokines in response to Toll-like receptor (TLR) agonists and lipopolysaccharides (LPS), and Tle1(Δ/Δ) mice display an enhanced inflammatory response to ear skin 12-O-tetradecanoylphorbol-13-acetate treatment. Loss of Tle1 not only results in increased phosphorylation and activation of proinflammatory NF-κB but also results in decreased Hes1 (hairy and enhancer of split-1), a negative regulator of inflammation in macrophages. Furthermore, Tle1(Δ/Δ) mice exhibit accelerated growth of B6-F10 melanoma xenografts. Our work provides the first in vivo evidence, to our knowledge, that TLE1 is a major counterregulator of inflammation with potential roles in a variety of inflammatory diseases and in cancer progression.

The t(7;11)(p15;p15.4) has been reported to fuse the NUP98 gene (11p15), a component of the nuclear pore complex, with the class-1 homeobox gene HOXA9 at 7p15. This translocation has been associated with myeloid leukemias, predominantly acute myeloid leukemia (AML) M2 subtype with trilineage myelodysplastic features, and with a poor prognosis. The derived fusion protein retains the FG repeat motif of NUP98 N-terminus and the homeodomain shared by the HOX genes, acting as an oncogenic transcription factor critical for leukemogenesis. We report here a new complex t(7;11)-variant, i.e., t(7;11;13;17)(p15;p15;p?;p1?2) in a patient with AML-M2 and poor prognosis. The NUP98-HOXA9 fusion transcript was detected by RT-PCR, suggesting its role in the malignant transformation as it has been postulated for other t(7;11)-associated leukemias. No other fusion transcripts involving the NUP98 or HOXA9 genes were present, although other mechanisms involving several genes on chromosomes 13 and 17 may also be involved. To our knowledge, this is the first t(7;11) variant involving NUP98 described in hematological malignancies.

Activation of an oncogene via its juxtaposition to the IGH locus by a chromosomal translocation or, less frequently, by genomic amplification is considered a major mechanism of B-cell lymphomagenesis. However, amplification of an IGH/oncogene fusion, coined a complicon, is a rare event in human cancers and has been associated with poor outcome and resistance to treatment. In this article are descriptions of two cases of germinal-center-derived B-cell lymphomas with IGH/BCL2 fusion that additionally displayed amplification of an IGH/MYC fusion. As shown by fluorescence in situ hybridization, the first case contained a IGH/MYC complicon in double minutes, whereas the second case showed a BCL2/IGH/MYC complicon on a der(8)t(8;14)t(14;18). Additional molecular cytogenetic and mutation analyses revealed that the first case also contained a chromosomal translocation affecting the BCL6 oncogene and a biallelic inactivation of TP53. The second case harbored a duplication of REL and acquired a translocation affecting IGL and a biallelic inactivation of TP53 during progression. Complicons affecting Igh/Myc have been reported previously in lymphomas of mouse models simultaneously deficient in Tp53 and in genes of the nonhomologous end–joining DNA repair pathway. To the best of our knowledge, this is the first time that IGH/MYC complicons have been reported in human lymphomas. Our findings imply that the two mechanisms resulting in MYC deregulation, that is, translocation and amplification, can occur simultaneously. © 2005 Wiley-Liss, Inc.

Chromosomal abnormalities clustering in multiple myeloma reveals cytogenetic subgroups with nonrandom acquisition of chromosomal changes

SummaryFollowing injury, stem cells restore normal tissue architecture by producing the proper number and proportions of differentiated cells. Current models of airway epithelial regeneration propose that distinct cytokeratin 8-expressing progenitor cells, arising from p63+ basal stem cells, subsequently differentiate into secretory and ciliated cell lineages. We now show that immediately following injury, discrete subpopulations of p63+ airway basal stem/progenitor cells themselves express Notch pathway components associated with either secretory or ciliated cell fate commitment. One basal cell population displays intracellular Notch2 activation and directly generates secretory cells; the other expresses c-myb and directly yields ciliated cells. Furthermore, disrupting Notch ligand activity within the basal cell population at large disrupts the normal pattern of lineage segregation. These non-cell-autonomous effects demonstrate that effective airway epithelial regeneration requires intercellular communication within the broader basal stem/progenitor cell population. These findings have broad implications for understanding epithelial regeneration and stem cell heterogeneity.

Following myocardial infarction (MI), myeloid cells derived from the hematopoietic system drive a sharp increase in systemic leukocyte levels that correlates closely with mortality. The origin of these myeloid cells, and the response of hematopoietic stem and progenitor cells (HSPCs) to MI, however, is unclear. Here, we identify a CCR2(+)CD150(+)CD48(-) LSK hematopoietic subset as the most upstream contributor to emergency myelopoiesis after ischemic organ injury. This subset has 4-fold higher proliferation rates than CCR2(-)CD150(+)CD48(-) LSK cells, displays a myeloid differentiation bias, and dominates the migratory HSPC population. We further demonstrate that the myeloid translocation gene 16 (Mtg16) regulates CCR2(+) HSPC emergence. Mtg16(-/-) mice have decreased levels of systemic monocytes and infarct-associated macrophages and display compromised tissue healing and post-MI heart failure. Together, these data provide insights into regulation of emergency hematopoiesis after ischemic injury and identify potential therapeutic targets to modulate leukocyte output after MI.

Background The bone marrow microenvironment (BMEV) regulates the highly regenerative hematopoietic system. However, there are a limited number of BMEV-derived molecules with a definitive role in maintaining hematopoietic stem and progenitor cells (HSPCs). Extracellular vesicles (EVs) encapsulate bioactive molecules, and may modify the physiology of their target cells. In hematopoiesis, EVs derived from culture-expanded mesenchymal cells can rescue irradiation damage, expand human umbilical cord blood cells and support HSPCs in vitro . However, in vivo evidence of EV function is lacking. We therefore sought to investigate the role of EVs in the interaction between the BMEV and the hematopoietic system and took advantage of existing mice bearing genetic reporters of key mesenchymal cell types. Results While analyzing the bone marrow (BM) of different mesenchymal cell-GFP reporter mice, we unexpectedly found CD45+ GFP+ cells. These were confirmed as single cells with intracellular GFP as demonstrated by imaging flow cytometry and confocal microscopy (Fig. 1A). Moreover, their hematopoietic identity was confirmed by their ability to form myeloid colonies in methylcellulose. Transplanted CD45.1 BM into Osteocalcin-Topaz (Ocn-Topaz) and Collagen1-GFP (Col1-GFP) mice that label osteoblasts, as well as Nestin-GFP (Nes-GFP) that labels mesenchymal stem cells demonstrated that donor cells are comparably labeled with GFP in Ocn-Topaz and Col1-GFP (2.2%) but at a much lower frequency (0.05%) in Nes-GFP. We therefore decided to proceed with the Ocn-Topaz model to investigate the role of osteoblast derived EVs in hematopoietic communication. Within the lineage negative compartment, the frequency of GFP+ cells increased with maturation. The highest frequency found in GMPs (0.06% of live cells were GFP+), followed by CMPs (0.01%), MEPs (0.002%) and LKS (0.004%) (Fig. 1B). Of particular interest, Lin- GFP+ cells formed ~5 fold more colonies as compared to their GFP- counterparts. However, transplantation assays demonstrated that the GFP+ cells possessed a decreased ability for long term reconstitution. Given the molecular weight of GFP, we hypothesized that EVs were the basis for transfer. Transmission electron microscopy coupled with immunogold staining revealed microvesicular structures of ~100 nm in size that contained GFP and that were labeled with the exosome marker TSG101 (Fig. 1C). Western blotting and flow cytometry detected labeling with exosome markers CD81 and CD9. Heparin sulfate proteoglycans (HSPGs) have been implicated in the biogenesis and uptake of EVs. Osteoblast-specific disruption of HSPGs by the knock out of the glycosyl transferase EXT1 resulted in a (40%) drop in the frequency of GFP+ cells in the GMP compartment. These findings demonstrate the EV-dependent transfer of GFP from osteoblasts to BM hematopoietic cells, and confirm GFP as a marker for the isolation and characterization of EV target cells. Exosomes from the BM of Ocn-Topaz mice in addition to GFP+ and GFP- GMPs were isolated for small RNA sequencing. In parallel, GMP populations were collected for mRNA sequencing. Global analysis of small RNA libraries from EVs and GMPs demonstrated that piRNAs was the most abundant species in both EVs (30%) and GMPs (18%). Surprisingly, EVs had low miRNA content (1.4%) compared to GMPs (9.2%) (Fig. 1D). When comparing GFP+ GMPs to GFP- ones, 6 miRNAs (mir-143, mir-122, mir-423-5p, mir-451, mir-206, mir-146b*) showed at least 100% increase in the GFP+GMPs. Predicted targets of mir-143, mir-206, mir-146 emerged as enriched sets when comparing gene expression of GFP+ and GFP- GMPs. In contrast, tRNAs was the most enriched species in EVs (10.5%) when compared to GMPs (2.5%) (Fig. 1D) and interestingly, GFP+ GMPs had higher content of tRNA when compared to GFP- (3.3% vs 1.7%) respectively. Given the role of tRNAs in translation and the emerging role of tRNA fragments (tRFs) in translation regulation and stress signaling, it was of interest to see translation and ribosome genesis among the top enriched gene sets when comparing GFP+ and GFP- GMPs. In conclusion, we present evidence for the in vivo transfer of bioactive EVs from osteoblasts to BM progenitor populations, and that this transfer alters hematopoietic cell function and gene expression. Moreover, we identify piRNAs and tRNAs as the most enriched species of small RNAs within BM derived EVs. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

R loop, a transcription intermediate containing RNA:DNA hybrids and displaced single-stranded DNA (ssDNA), has emerged as a major source of genomic instability. RNaseH1, which cleaves the RNA in RNA:DNA hybrids, plays an important role in R loop suppression. Here, we show that replication protein A (RPA), a ssDNA-binding protein, interacts with RNaseH1 and colocalizes with both RNaseH1 and R loops in cells. In vitro, purified RPA directly enhances the association of RNaseH1 with RNA:DNA hybrids and stimulates the activity of RNaseH1 on R loops. An RPA binding-defective RNaseH1 mutant is not efficiently stimulated by RPA in vitro, fails to accumulate at R loops in cells, and loses the ability to suppress R loops and associated genomic instability. Thus, in addition to sensing DNA damage and replication stress, RPA is a sensor of R loops and a regulator of RNaseH1, extending the versatile role of RPA in suppression of genomic instability.

Stem cells integrate inputs from multiple sources. Stem cell niches provide signals that promote stem cell maintenance, while differentiated daughter cells are known to provide feedback signals to regulate stem cell replication and differentiation. Recently, stem cells have been shown to regulate themselves using an autocrine mechanism. The existence of a 'stem cell niche' was first postulated by Schofield in 1978 to define local environments necessary for the maintenance of haematopoietic stem cells. Since then, an increasing body of work has focused on defining stem cell niches. Yet little is known about how progenitor cell and differentiated cell numbers and proportions are maintained. In the airway epithelium, basal cells function as stem/progenitor cells that can both self-renew and produce differentiated secretory cells and ciliated cells. Secretory cells also act as transit-amplifying cells that eventually differentiate into post-mitotic ciliated cells . Here we describe a mode of cell regulation in which adult mammalian stem/progenitor cells relay a forward signal to their own progeny. Surprisingly, this forward signal is shown to be necessary for daughter cell maintenance. Using a combination of cell ablation, lineage tracing and signalling pathway modulation, we show that airway basal stem/progenitor cells continuously supply a Notch ligand to their daughter secretory cells. Without these forward signals, the secretory progenitor cell pool fails to be maintained and secretory cells execute a terminal differentiation program and convert into ciliated cells. Thus, a parent stem/progenitor cell can serve as a functional daughter cell niche.