MicroRNAs in Normal and Malignant Myelopoiesis

__abstract__ Hematopoiesis is the lifelong continuous process in which hematopoietic stem and progenitor cells (HSPCs) proliferate and differentiate towards mature blood cells. Hematopoiesis is tightly controlled by a network of growth factors and the hematopoietic niche in the bone marrow (BM). This ensures the balanced blood cell production under homeostatic conditions and allows for transient elevation of specific blood cell types production in response to infections or bleeding 1. In mammalian organisms, long-term hematopoietic stem cells (LT-HSCs) reside in the BM and have self-renewal capacity over the lifespan of the organism 2,3. The estimated amount of LT-HSCs is approximately 0.007% of all hematopoietic cells in the BM 4. LT-HSCs give rise to short-term HSCs (ST-HSCs) and multipotent progenitors (MPPs) (Figure 1). These cells have the potential to differentiate into all the different hematopoietic cell types but have less self-renewal capacity 4. Together, LT-HCSs, ST-HCSs and MPPs constitute 0.05% of mouse BM cells 2. MPPs differentiate into common lymphoid progenitors (CLPs) and common myeloid progenitors (CMPs) (Figure 1). Subsequently, CLPs differentiate into B-cell and T-cell lineages. CMPs first develop into more specified myeloid progenitors, which are megakaryocyte/erythroid progenitors (MEPs) and granulocyte/monocyte progenitors (GMPs). Granulocytes, monocytes and macrophages arise from GMPs, whereas MEPs differentiate towards erythrocytes and thrombocytes (platelets) (Figure 1). The process of differentiation of HSPCs towards mature myeloid cells is referred as myelopoiesis. In adult mammalian organisms, myelopoiesis occurs in the BM. Disruption of the balance between cell proliferation, differentiation and cell death leads to different hematopoietic disorders, e.g., leukemia, characterized by proliferation of undifferentiated cells, or bone marrow failure (BMF), characterized by impaired hematopoiesis involving one or multiple hematopoietic lineages 5,6. Proliferation and differentiation of HSPCs are coordinated by gene expression programs driven by endogenous and exogenous factors. MicroRNAs (miRNAs) are a class of non-coding RNAs which function as regulators of gene expression. In the studies described in this thesis the role of miRNAs in normal myelopoiesis and their involvement in acute myeloid leukemia (AML) and Fanconi anemia (FA), the most frequent inherited form of BMF syndromes are investigated. AML, FA and miRNAs will be further introduced in the following sections

Stop the dicing in hematopoiesis: What have we learned?

MicroRNAs (miRNAs) belong to an abundant class of highly conserved small (22nt) non-coding RNAs. MiRNA profiling studies indicate that their expression is highly cell type-dependent. DICER1 is an essential RNase III endoribonuclease for miRNA processing. Hematopoietic cell type- and developmental stage-specific Dicer1 deletion models show that miRNAs are essential regulators of cellular survival, differentiation and function. For instance, miRNA deficiency in hematopoietic stem cells and progenitors of different origins results in decreased cell survival, dramatic developmental aberrations or dysfunctions in mice. We recently found that homozygous Dicer1 deletion in myeloid-committed progenitors results in an aberrant expression of stem cell genes and induces a regained self-renewal capacity. Moreover, Dicer1 deletion causes a block in macrophage development and myeloid dysplasia, a cellular condition that may be considered as a preleukemic state. However, Dicer1-null cells do not develop leukemia in mice, indicating that depletion of miRNAs is not enough for tumorigenesis. Surprisingly, we found that heterozygous Dicer1 deletion in myeloid-committed progenitors, but not Dicer1 knockout, collaborates with p53 deletion in leukemic progression and results in various types of leukemia. Our data indicate that Dicer1 is a haploinsufficient tumorsuppressor in hematopoietic neoplasms, which is consistent with the observed downregulation of miRNA expression in human leukemia samples. Here, we review the various hematopoietic specific Dicer1 deletion mouse models and the phenotypes observed within the different hematopoietic lineages and cell developmental stages. Finally, we discuss the role for DICER1 in mouse and human malignant hematopoiesis

Performance evaluation of PCBN, coated carbide and mixed ceramic inserts in finish-turning of AISI D2 steel

The present study compares the performance of three different cutting tools, viz., PCBN, mixed ceramic and coated carbide tool in finish turning of hardened D2 tool steel in terms of tool wear, surface roughness, and economic feasibility under dry cutting conditions. Results showed that tool life of PCBN inserts was better than mixed ceramic and coated carbide inserts. The flank wear of PCBN tools was observed to be lower than mixed ceramic and coated carbide inserts. The surface roughness achieved under all cutting conditions for mixed ceramic and coated-carbide inserts was comparable with that achieved with PCBN inserts and was below 1.6μm. Experimental results showed that the wear mechanism of ceramic tool is pre-dominantly abrasive wear at lower speeds and abrasive wear followed by adhesive wear at medium and higher speeds and for PCBN tools the dominant wear mechanism is abrasive wear and cratering at lower speeds followed by adhesive wear at higher speeds. For carbide tool the dominant wear mechanism was abrasive wear and cratering at lower speeds followed by adhesion and chipping at higher speeds. Obtained results revealed that PCBN tools can outperform both ceramic and carbide tools in terms of tool life under different machinability criteria used

Diversidad e incidencia de hongos asociados a enfermedades foliares de la avena (Avena sativa L.) en los valles altos de México

El objetivo de este estudio fue determinar las especies de hongos asociados a enfermedades foliares de la avena en los Valles Altos de México. Durante los ciclos agrícolas primavera–verano 2009 y 2010, se recolectaron en 163 sitios diferentes un total de 815 muestras de plantas de avena exhibiendo síntomas de enfermedades foliares y signos en el caso de royas. La identificación de los hongos se basó en caracteres morfológicos. Se identificaron seis especies de hongos fitopatógenos: Colletotrichum graminicola, Curvularia hawaiiensis, Drechslera avenacea, Passalora graminis, Puccinia coronata y Puccinia graminis f. sp. avenae. Además, se encontraron cinco especies de hongos saprófitos o patógenos débiles: Alternaria triticicola, A. triticina, A. uredinis, Curvularia protuberata y Pleospora sp. Los hongos fitopatógenos que presentaron mayor frecuencia fueron: P. graminis f. sp. avenae (73%), P. coronata (61%) y D. avenacea (19%).The aim of this study was to determine the fungal species associated to foliar diseases on oat in the highlands of Mexico. During spring-fall seasons 2009 and 2010, a total of 815 samples of oat plants exhibiting foliar diseases were collected from 163 different oat fields. Fungal identification was based on morphological characteristics. Six different pathogenic fungal species were identified: Colletotrichum graminicola, Curvularia hawaiiensis, Drechslera avenacea, Passalora graminis, Puccina coronata, Puccinia graminis f. sp. avenae. Whereas, that the saprophytic and weakly pathogenic fungi founded were: Alternaria triticicola, A. triticina, A. uredinis, Curvularia protuberata y Pleospora sp. The species P. graminis f. sp. avenae (73%), P. coronata (61%) and D. avenacea (19%) were the pathogenic fungi most frequently founded.Gerencia de Comunicación e Imagen InstitucionalFil: García-León, E. Colegio de Postgraduados. Instituto de Fitosanidad. Fitopatología; MéxicoFil: Leyva-Mir, S.G. Universidad Autónoma Chapingo. Departamento de Parasitología Agrícola; México.Fil: Villaseñor-Mir, H.E. Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias. Campo Experimental del Valle de México; México.Fil: Rodríguez-García, M.F. Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias. Campo Experimental del Valle de México; México.Fil: Tovar-Pedraza, J.M. Colegio de Postgraduados. Instituto de Fitosanidad. Fitopatología; Méxic

Central Pb+Pb Collisions at 158 A GeV/c Studied by Pion-Pion Interferometry

Two-particle correlations have been measured for identified negative pions from central 158 AGeV Pb+Pb collisions and fitted radii of about 7 fm in all dimensions have been obtained. A multi-dimensional study of the radii as a function of kT is presented, including a full correction for the resolution effects of the apparatus. The cross term Rout-long of the standard fit in the Longitudinally CoMoving System (LCMS) and the vl parameter of the generalised Yano-Koonin fit are compatible with 0, suggesting that the source undergoes a boost invariant expansion. The shapes of the correlation functions in Qinv and Qspace have been analyzed in detail. They are not Gaussian but better represented by exponentials. As a consequence, fitting Gaussians to these correlation functions may produce different radii depending on the acceptance of the experimental setup used for the measurement.Comment: 13 pages including 10 figure

Search for Disoriented Chiral Condensates in 158 AGeV Pb+Pb Collisions

The restoration of chiral symmetry and its subsequent breaking through a phase transition has been predicted to create regions of Disoriented Chiral Condensates (DCC). This phenomenon has been predicted to cause anomalous fluctuations in the relative production of charged and neutral pions in high-energy hadronic and nuclear collisions. The WA98 experiment has been used to measure charged and photon multiplicities in the central region of 158 AGeV Pb+Pb collisions at the CERN SPS. In a sample of 212646 events, no clear DCC signal can be distinguished. Using a simple DCC model, we have set a 90% C.L. upper limit on the maximum DCC production allowed by the data.Comment: 20 Pages, LaTeX, uses elsart.cls, 8 eps figures included, submitted to Physics Letters

First Measurement of Z/gamma* Production in Compton Scattering of Quasi-real Photons

We report the first observation of Z/gamma* production in Compton scattering of quasi-real photons. This is a subprocess of the reaction e+e- to e+e-Z/gamma*, where one of the final state electrons is undetected. Approximately 55 pb-1 of data collected in the year 1997 at an e+e- centre-of-mass energy of 183 GeV with the OPAL detector at LEP have been analysed. The Z/gamma* from Compton scattering has been detected in the hadronic decay channel. Within well defined kinematic bounds, we measure the product of cross-section and Z/gamma* branching ratio to hadrons to be (0.9+-0.3+-0.1) pb for events with a hadronic mass larger than 60 GeV, dominated by (e)eZ production. In the hadronic mass region between 5 GeV and 60 GeV, dominated by (e)egamma* production, this product is found to be (4.1+-1.6+-0.6) pb. Our results agree with the predictions of two Monte Carlo event generators, grc4f and PYTHIA.Comment: 18 pages, LaTeX, 5 eps figures included, submitted to Physics Letters

Search for Higgs Bosons in e+e- Collisions at 183 GeV

The data collected by the OPAL experiment at sqrts=183 GeV were used to search for Higgs bosons which are predicted by the Standard Model and various extensions, such as general models with two Higgs field doublets and the Minimal Supersymmetric Standard Model (MSSM). The data correspond to an integrated luminosity of approximately 54pb-1. None of the searches for neutral and charged Higgs bosons have revealed an excess of events beyond the expected background. This negative outcome, in combination with similar results from searches at lower energies, leads to new limits for the Higgs boson masses and other model parameters. In particular, the 95% confidence level lower limit for the mass of the Standard Model Higgs boson is 88.3 GeV. Charged Higgs bosons can be excluded for masses up to 59.5 GeV. In the MSSM, mh > 70.5 GeV and mA > 72.0 GeV are obtained for tan{beta}>1, no and maximal scalar top mixing and soft SUSY-breaking masses of 1 TeV. The range 0.8 < tanb < 1.9 is excluded for minimal scalar top mixing and m{top} < 175 GeV. More general scans of the MSSM parameter space are also considered.Comment: 49 pages. LaTeX, including 33 eps figures, submitted to European Physical Journal

A Measurement of the Product Branching Ratio f(b->Lambda_b).BR(Lambda_b->Lambda X) in Z0 Decays

The product branching ratio, f(b->Lambda_b).BR(Lambda_b->Lambda X), where Lambda_b denotes any weakly-decaying b-baryon, has been measured using the OPAL detector at LEP. Lambda_b are selected by the presence of energetic Lambda particles in bottom events tagged by the presence of displaced secondary vertices. A fit to the momenta of the Lambda particles separates signal from B meson and fragmentation backgrounds. The measured product branching ratio is f(b->Lambda_b).BR(Lambda_b->Lambda X) = (2.67+-0.38(stat)+0.67-0.60(sys))% Combined with a previous OPAL measurement, one obtains f(b->Lambda_b).BR(Lambda_b->Lambda X) = (3.50+-0.32(stat)+-0.35(sys))%.Comment: 16 pages, LaTeX, 3 eps figs included, submitted to the European Physical Journal

Measurement of the Michel Parameters in Leptonic Tau Decays

The Michel parameters of the leptonic tau decays are measured using the OPAL detector at LEP. The Michel parameters are extracted from the energy spectra of the charged decay leptons and from their energy-energy correlations. A new method involving a global likelihood fit of Monte Carlo generated events with complete detector simulation and background treatment has been applied to the data recorded at center-of-mass energies close to sqrt(s) = M(Z) corresponding to an integrated luminosity of 155 pb-1 during the years 1990 to 1995. If e-mu universality is assumed and inferring the tau polarization from neutral current data, the measured Michel parameters are extracted. Limits on non-standard coupling constants and on the masses of new gauge bosons are obtained. The results are in agreement with the V-A prediction of the Standard Model.Comment: 32 pages, LaTeX, 9 eps figures included, submitted to the European Physical Journal