A role for dystroglycan in the pathophysiology of acute leukemic cells.

AIMS: Previous reports have demonstrated that alterations or reduced expression of Dystroglycan (Dg) complex (αDg and βDg subunits) are related to progression and severity of neoplastic solid tissues. Therefore we determined the expression pattern and subcellular distribution of Dg complex in Acute Myeloid Leukemia (AML) primary blasts (M1, M2, and M3 phenotypes), as well as HL-60 and Kasumi-1 leukemia cell lines. Additionally, we evaluated the relative expression of the main enzymes controlling α-Dg glycosylation to ascertain the post-translational modifications in the leukemia cell phenotype. MAIN METHODS: Primary leukemia blasts and leukemia cell lines were processed by confocal analysis to determine the subcellular distribution of α-Dg, β-Dg, and phosphorylated β-Dg (Y892), to evaluate the expression pattern of the different Dg species we performed Western Blot (WB) assays, while the messenger RNA (mRNA) expression of enzymes involved in α-Dg glycosylation, such as POMGnT1, POMT1, POMT2, LARGE, FKTN, and FKRP, were evaluated by qualitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR). Finally, in an attempt to ameliorate the leukemia cell phenotype, we transfected leukemia cells with a plasmid expressing the Dg complex. KEY FINDINGS: The Dg complex was altered in leukemia cells, including decreased mRNA, protein, and α-Dg glycosylated levels, mislocalization of β-Dg, and a diminution of mRNA expression of LARGE in patients leukemia blasts and in cell lines. Interestingly, the exogenous expression of Dg complex promoted filopodial formation, differentiation, and diminished proliferation, attenuating some HL-60 and Kasumi cells characteristics. SIGNIFICANCE: Dg complex integrity and balance are required for a proper hematopoietic cell function, in that its disruption might contribute to leukemia pathophysiology

Search for W' bosons decaying to an electron and a neutrino with the D0 detector

This Letter describes the search for a new heavy charged gauge boson W' decaying into an electron and a neutrino. The data were collected with the D0 detector at the Fermilab Tevatron proton-antiproton Collider at a center-of-mass energy of 1.96 TeV, and correspond to an integrated luminosity of about 1 inverse femtobarn. Lacking any significant excess in the data in comparison with known processes, an upper limit is set on the production cross section times branching fraction, and a W' boson with mass below 1.00 TeV can be excluded at the 95% C.L., assuming standard-model-like couplings to fermions. This result significantly improves upon previous limits, and is the most stringent to date.Comment: submitted to Phys. Rev. Let

Measurement of the ratios of the Z/G* + >= n jet production cross sections to the total inclusive Z/G* cross section in ppbar collisions at sqrt(s) = 1.96 TeV

We present a study of events with Z bosons and jets produced at the Fermilab Tevatron Collider in ppbar collisions at a center of mass energy of 1.96 TeV. The data sample consists of nearly 14,000 Z/G* -> e+e- candidates corresponding to the integrated luminosity of 0.4 fb-1 collected using the D0 detector. Ratios of the Z/G* + >= n jet cross sections to the total inclusive Z/G* cross section have been measured for n = 1 to 4 jet events. Our measurements are found to be in good agreement with a next-to-leading order QCD calculation and with a tree-level QCD prediction with parton shower simulation and hadronization.Comment: 7 pages, 2 figures, slightly modified, submitted to Phys. Lett.

Search for single top quarks in the tau+jets channel using 4.8 fb−1^{-1} of ppˉp\bar{p} collision data

We present the first direct search for single top quark production using tau leptons. The search is based on 4.8 fb$^{-1}$ of integrated luminosity collected in $p\bar{p}$ collisions at $\sqrt{s}$=1.96 TeV with the D0 detector at the Fermilab Tevatron Collider. We select events with a final state including an isolated tau lepton, missing transverse energy, two or three jets, one or two of them $b$ tagged. We use a multivariate technique to discriminate signal from background. The number of events observed in data in this final state is consistent with the signal plus background expectation. We set in the tau+jets channel an upper limit on the single top quark cross section of \TauLimObs pb at the 95% C.L. This measurement allows a gain of 4% in expected sensitivity for the observation of single top production when combining it with electron+jets and muon+jets channels already published by the D0 collaboration with 2.3 fb$^{-1}$ of data. We measure a combined cross section of \SuperCombineXSall pb, which is the most precise measurement to date.Comment: 12 pages, 5 figure

b-Jet Identification in the D0 Experiment

Algorithms distinguishing jets originating from b quarks from other jet flavors are important tools in the physics program of the D0 experiment at the Fermilab Tevatron p-pbar collider. This article describes the methods that have been used to identify b-quark jets, exploiting in particular the long lifetimes of b-flavored hadrons, and the calibration of the performance of these algorithms based on collider data.Comment: submitted to Nuclear Instruments and Methods in Physics Research

Search for pair production of the scalar top quark in the electron-muon final state

We report the result of a search for the pair production of the lightest supersymmetric partner of the top quark ($\tilde{t}_1$) in $p\bar{p}$ collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider corresponding to an integrated luminosity of 5.4 fb$^{-1}$. The scalar top quarks are assumed to decay into a $b$ quark, a charged lepton, and a scalar neutrino ($\tilde{\nu}$), and the search is performed in the electron plus muon final state. No significant excess of events above the standard model prediction is detected, and improved exclusion limits at the 95% C.L. are set in the the ($M_{\tilde{t}_1}$,$M_{\tilde{\nu}}$) mass plane

Measurement of the dijet invariant mass cross section in proton anti-proton collisions at sqrt{s} = 1.96 TeV

The inclusive dijet production double differential cross section as a function of the dijet invariant mass and of the largest absolute rapidity of the two jets with the largest transverse momentum in an event is measured in proton anti-proton collisions at sqrt{s} = 1.96 TeV using 0.7 fb^{-1} integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The measurement is performed in six rapidity regions up to a maximum rapidity of 2.4. Next-to-leading order perturbative QCD predictions are found to be in agreement with the data.Comment: Published in Phys. Lett. B, 693, (2010), 531-538, 8 pages, 2 figures, 6 table

Measurement of Z/gamma*+jet+X angular distributions in ppbar collisions at sqrt{s}=1.96 TeV

We present the first measurements at a hadron collider of differential cross sections for Z+jet+X production in delta phi(Z, jet), |delta y(Z, jet)| and |y_boost(Z, jet)|. Vector boson production in association with jets is an excellent probe of QCD and constitutes the main background to many small cross section processes, such as associated Higgs production. These measurements are crucial tests of the predictions of perturbative QCD and current event generators, which have varied success in describing the data. Using these measurements as inputs in tuning event generators will increase the experimental sensitivity to rare signals.Comment: Published in Physics Letters B 682 (2010), pp. 370-380. 15 pages, 6 figure

Search for the standard model Higgs boson in tau final states

We present a search for the standard model Higgs boson using hadronically decaying tau leptons, in 1 inverse femtobarn of data collected with the D0 detector at the Fermilab Tevatron ppbar collider. We select two final states: tau plus missing transverse energy and b jets, and tau+ tau- plus jets. These final states are sensitive to a combination of associated W/Z boson plus Higgs boson, vector boson fusion and gluon-gluon fusion production processes. The observed ratio of the combined limit on the Higgs production cross section at the 95% C.L. to the standard model expectation is 29 for a Higgs boson mass of 115 GeV.Comment: publication versio

Search for scalar bottom quarks and third-generation leptoquarks in ppbar collisions at sqrt(s) = 1.96 TeV

We report the results of a search for pair production of scalar bottom quarks (sbottom) and scalar third-generation leptoquarks in 5.2 fb-1 of ppbar collisions at the D0 experiment of the Fermilab Tevatron Collider. Scalar bottom quarks are assumed to decay to a neutralino and a $b$ quark, and we set 95% C.L. lower limits on their production in the (m_sbottom, m_neutralino) mass plane such as m_sbottom>247 GeV for m_neutralino=0 and m_neutralino>110 GeV for 160<m_sbottom<200 GeV. The leptoquarks are assumed to decay to a tau neutrino and a $b$ quark, and we set a 95% C.L. lower limit of 247 GeV on the mass of a charge-1/3 third-generation scalar leptoquark.Comment: Published by Phys. Lett.