Authors: Williams LH, Fromm G, Gokey NG, Henriques T, Muse GW, Burkholder A, Fargo DC, Hu G, Adelman K
Journal: Mol Cell. 2015 Mar 11. pii: S1097-2765(15)00095-7. doi: 10.1016/j.molcel.2015.02.003. [Epub ahead of print]
The remarkable capacity for pluripotency and self-renewal in embryonic stem cells (ESCs) requires a finely tuned transcriptional circuitry wherein the pathways and genes that initiate differentiation are suppressed, but poised to respond rapidly to developmental signals. To elucidate transcriptional control in mouse ESCs in the naive, ground state, we defined the distribution of engaged RNA polymerase II (Pol II) at high resolution. We find that promoter-proximal pausing of Pol II is most enriched at genes regulating cell cycle and signal transduction and not, as expected, at developmental or bivalent genes. Accordingly, ablation of the primary pause-inducing factor NELF does not increase expression of lineage markers, but instead causes proliferation defects, embryonic lethality, and dysregulation of ESC signaling pathways. Indeed, ESCs lacking NELF have dramatically attenuated FGF/ERK activity, rendering them resistant to differentiation. This work thus uncovers a key role for NELF-mediated pausing in establishing the responsiveness of stem cells to developmental cues.
Authors: Zhang D, Gao ZG, Zhang K, Kiselev E, Crane S, Wang J, Paoletta S, Yi C, Ma L, Zhang W, Han GW, Liu H, Cherezov V, Katritch V4, Jiang H5, Stevens RC6, Jacobson KA2, Zhao Q1, Wu B1.
Journal: Nature. 2015 Mar 30. doi: 10.1038/nature14287. [Epub ahead of print]
In response to adenosine 5'-diphosphate, the P2Y1 receptor (P2Y1R) facilitates platelet aggregation, and thus serves as an important antithrombotic drug target. Here we report the crystal structures of the human P2Y1R in complex with a nucleotide antagonist MRS2500 at 2.7 Å resolution, and with a non-nucleotide antagonist BPTU at 2.2 Å resolution. The structures reveal two distinct ligand-binding sites, providing atomic details of P2Y1R's unique ligand-binding modes. MRS2500 recognizes a binding site within the seven transmembrane bundle of P2Y1R, which is different in shape and location from the nucleotide binding site in the previously determined structure of P2Y12R, representative of another P2YR subfamily. BPTU binds to an allosteric pocket on the external receptor interface with the lipid bilayer, making it the first structurally characterized selective G-protein-coupled receptor (GPCR) ligand located entirely outside of the helical bundle. These high-resolution insights into P2Y1R should enable discovery of new orthosteric and allosteric antithrombotic drugs with reduced adverse effects.
Authors: Gadalla SM, Wang T, Haagenson M, Spellman SR, Lee SJ, Williams KM, Wong JY, De Vivo I, Savage SA
Journal: JAMA. 2015 Feb 10;313(6):594-602. doi: 10.1001/jama.2015.7
IMPORTANCE: Telomeres protect chromosome ends and are markers of cellular aging and replicative capacity.
OBJECTIVE: To evaluate the association between recipient and donor pretransplant leukocyte telomere length with outcomes after unrelated donor allogeneic hematopoietic cell transplantation (HCT) for patients with severe aplastic anemia.
DESIGN, PARTICIPANTS, AND SETTING: The study included 330 patients (235 acquired, 85 Fanconi anemia, and 10 Diamond-Blackfan anemia) and their unrelated donors who had pre-HCT blood samples and clinical and outcome data available at the Center for International Blood and Marrow Transplant Research. Patients underwent HCT between 1989 and 2007 in 84 centers and were followed-up to March 2013.
EXPOSURES: Recipient and donor pre-HCT leukocyte telomere length classified into long (third tertile) and short (first and second tertiles combined) based on donor telomere length distribution.
MAIN OUTCOMES AND MEASURES: Overall survival, neutrophil recovery, and acute and chronic graft-vs-host disease, as ascertained by transplant centers through regular patient follow-up.
RESULTS: Longer donor leukocyte telomere length was associated with higher survival probability (5-year overall survival, 56%; number at risk, 57; cumulative deaths, 50) than shorter donor leukocyte telomere length (5-year overall survival, 40%; number at risk, 71; cumulative deaths, 128; P = .009). The association remained statistically significant after adjusting for donor age, disease subtype, Karnofsky performance score, graft type, HLA matching, prior aplastic anemia therapy, race/ethnicity, and calendar year of transplant (hazard ratio [HR], 0.61; 95% CI, 0.44-0.86). Similar results were noted in analyses stratified on severe aplastic anemia subtype, recipient age, HLA matching, calendar year of transplant, and conditioning regimen. There was no association between donor telomere length and neutrophil engraftment at 28 days (cumulative incidence, 86% vs 85%; HR, 0.94; 95% CI, 0.73-1.22), acute graft-vs-host disease grades III-IV at 100 days (cumulative incidence, 22% vs 28%; HR, 0.77; 95% CI, 0.48-1.23), or chronic graft-vs-host disease at 1-year (cumulative incidence, 28% vs 30%; HR, 0.81; 95% CI, 0.53-1.24) for long vs short, respectively. Pretransplant leukocyte telomere length in the recipients was not associated with posttransplant survival (HR, 0.91; 95% CI, 0.64-1.30).
CONCLUSIONS AND RELEVANCE: Longer donor leukocyte telomere length was associated with increased 5-year survival in patients who received HCT for severe aplastic anemia. Patient leukocyte telomere length was not associated with survival. The results of this observational study suggest that donor leukocyte telomere length may have a role in long-term posttransplant survival.
Authors: Robbins HA, Pfeiffer RM, Shiels MS, Li J, Hall HI, Engels EA
Journal: J Natl Cancer Inst. 2015 Feb 6;107(4). pii: dju503. doi: 10.1093/jnci/dju503. Print 2015 Apr.
BACKGROUND: Nearly 900 000 people in the United States are living with diagnosed human immunodeficiency virus (HIV) infection and therefore increased cancer risk. The total number of cancers occurring among HIV-infected people and the excess number above expected background cases are unknown.
METHODS: We derived cancer incidence rates for the United States HIV-infected and general populations from Poisson models applied to linked HIV and cancer registry data and from Surveillance, Epidemiology, and End Results program data, respectively. We applied these rates to estimates of people living with diagnosed HIV at mid-year 2010 to estimate total and expected cancer counts, respectively. We subtracted expected from total cancers to estimate excess cancers.
RESULTS: An estimated 7760 (95% confidence interval [CI] = 7330 to 8320) cancers occurred in 2010 among HIV-infected people, of which 3920 cancers (95% CI = 3480 to 4470) or 50% (95% CI = 48 to 54%) were in excess of expected. The most common excess cancers were non-Hodgkin's lymphoma (NHL; n = 1440 excess cancers, occurring in 88% excess), Kaposi's sarcoma (KS, n = 910, 100% excess), anal cancer (n = 740, 97% excess), and lung cancer (n = 440, 52% excess). The proportion of excess cancers that were AIDS defining (ie, KS, NHL, cervical cancer) declined with age and time since AIDS diagnosis (both P < .001). For anal cancer, 83% of excess cases occurred among men who have sex with men, and 71% among those living five or more years since AIDS onset. Among injection drug users, 22% of excess cancers were lung cancer, and 16% were liver cancer.
CONCLUSIONS: The excess cancer burden in the US HIV population is substantial, and patterns across groups highlight opportunities for cancer control initiatives targeted to HIV-infected people.
Authors: Wang Q, Qian L, Chen SH, Chu CH, Wilson B, Oyarzabal E, Ali S, Robinson B, Rao D, Hong JS
Journal: Brain. 2015 Feb 25. pii: awv034. [Epub ahead of print]
Nicotinamide adenine dinucleotide phosphate oxidase, a key superoxide-producing enzyme, plays a critical role in microglia-mediated chronic neuroinflammation and subsequent progressive dopaminergic neurodegeneration in Parkinson's disease. Although nicotinamide adenine dinucleotide phosphate oxidase-targeting anti-inflammatory therapy for Parkinson's disease has been proposed, its application in translational research remains limited. The aim of this study was to obtain preclinical evidence supporting this therapeutic strategy by testing the efficacy of an ultra-low dose of the nicotinamide adenine dinucleotide phosphate oxidase inhibitor diphenyleneiodonium in both endotoxin (lipopolysaccharide)- and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated mice using post-treatment regimens. Our data revealed that post-treatment with diphenyleneiodonium significantly attenuated progressive dopaminergic degeneration and improved rotarod activity. Remarkably, post-treatment with diphenyleneiodonium 10 months after lipopolysaccharide injection when mice had 30% loss of nigral dopaminergic neurons, showed high efficacy in protecting the remaining neuronal population and restoring motor function. Diphenyleneiodonium-elicited neuroprotection was associated with the inhibition of microglial activation, a reduction in the expression of proinflammatory factors and an attenuation of α-synuclein aggregation. A pathophysiological evaluation of diphenyleneiodonium-treated mice, including assessment of body weight, organs health, and neuronal counts, revealed no overt signs of toxicity. In summary, infusion of ultra-low dose diphenyleneiodonium potently reduced microglia-mediated chronic neuroinflammation by selectively inhibiting nicotinamide adenine dinucleotide phosphate oxidase and halted the progression of neurodegeneration in mouse models of Parkinson's disease. The robust neuroprotective effects and lack of apparent toxic side effects suggest that diphenyleneiodonium at ultra-low dose may be a promising candidate for future clinical trials in Parkinson's disease patients.
Authors: Kim YJ, Igiesuorobo O, Ramos CI, Bao H, Zhang B, Serpe M
Journal: PLoS Genet. 2015 Feb 27;11(2):e1004988. doi: 10.1371/journal.pgen.1004988. eCollection 2015
Stabilization of neurotransmitter receptors at postsynaptic specializations is a key step in the assembly of functional synapses. Drosophila Neto (Neuropillin and Tolloid-like protein) is an essential auxiliary subunit of ionotropic glutamate receptor (iGluR) complexes required for the iGluRs clustering at the neuromuscular junction (NMJ). Here we show that optimal levels of Neto are crucial for stabilization of iGluRs at synaptic sites and proper NMJ development. Genetic manipulations of Neto levels shifted iGluRs distribution to extrajunctional locations. Perturbations in Neto levels also produced small NMJs with reduced synaptic transmission, but only Neto-depleted NMJs showed diminished postsynaptic components. Drosophila Neto contains an inhibitory prodomain that is processed by Furin1-mediated limited proteolysis. neto null mutants rescued with a Neto variant that cannot be processed have severely impaired NMJs and reduced iGluRs synaptic clusters. Unprocessed Neto retains the ability to engage iGluRs in vivo and to form complexes with normal synaptic transmission. However, Neto prodomain must be removed to enable iGluRs synaptic stabilization and proper postsynaptic differentiation.
Authors: Tiano JP, Springer DA, Rane SG
Journal: J Biol Chem. 2015 Feb 3. pii: jbc.M114.617399. [Epub ahead of print]
Beige adipose cells are a distinct and inducible type of thermogenic fat cell that express the mitochondrial uncoupling protein-1 and thus represent a powerful target for treating obesity. Mice lacking the transforming growth factor-beta (TGF-β) effector protein SMAD3 are protected against diet-induced obesity due to browning of their white adipose tissue (WAT) leading to increased whole body energy expenditure. However, the role SMAD3 plays in WAT browning is not clearly understood. Irisin is an exercise-induced skeletal muscle hormone that induces WAT browning similar to that observed in SMAD3 deficient mice. Together these observations suggested that SMAD3 may negatively regulate irisin production and/or secretion from skeletal muscle. To address this question we used wild type and SMAD3 knockout (Smad3-/-) mice subjected to an exercise regime and C2C12 myotubes treated with TGF-β, a TGF-β receptor-1 pharmacological inhibitor, adenovirus expressing constitutively active SMAD3 or siRNA against SMAD3. We find that in Smad3-/- mice exercise increases serum irisin and skeletal muscle FNDC5 (irisin precursor) and its upstream activator peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α) to a greater extent than in wild type mice. In C2C12 myotubes TGF-β suppresses FNDC5 and PGC-1α mRNA and protein levels via SMAD3 and promotes SMAD3 binding to the FNDC5 and PGC-1α promoters. These data establish that SMAD3 suppresses FNDC5 and PGC-1α in skeletal muscle cells. These findings shed light on the poorly understood regulation of irisin/FNDC5 by demonstrating a novel association between irisin and SMAD3 signaling in skeletal muscle.
Authors: Aroda VR, Christophi CA, Edelstein SL, Zhang P, Herman WH, Barrett-Connor E, Delahanty LM, Montez MG, Ackermann RT, Zhuo X, Knowler WC, Ratner RE; for the Diabetes Prevention Program Research Group
Journal: J Clin Endocrinol Metab. 2015 Feb 23:jc20143761. [Epub ahead of print]
Context: Gestational diabetes (GDM) confers a high risk of type 2 diabetes. In the Diabetes Prevention Program (DPP), intensive lifestyle (ILS) and metformin prevented or delayed diabetes in women with a history of GDM. Objective: The objective of the study was to evaluate the impact of ILS and metformin intervention over 10 years in women with and without a history of GDM in the DPP/Diabetes Prevention Program Outcomes Study. Design: This was a randomized controlled clinical trial with an observational follow-up. Setting: The study was conducted at 27 clinical centers. Participants: Three hundred fifty women with a history of GDM and 1416 women with previous live births but no history of GDM participated in the study. The participants had an elevated body mass index and fasting glucose and impaired glucose tolerance at study entry. Interventions: Interventions included placebo, ILS, or metformin. Outcomes Measure: Outcomes measure was diabetes mellitus. Results: Over 10 years, women with a history of GDM assigned to placebo had a 48% higher risk of developing diabetes compared with women without a history of GDM. In women with a history of GDM, ILS and metformin reduced progression to diabetes compared with placebo by 35% and 40%, respectively. Among women without a history of GDM, ILS reduced the progression to diabetes by 30%, and metformin did not reduce the progression to diabetes. Conclusions: Women with a history of GDM are at an increased risk of developing diabetes. In women with a history of GDM in the DPP/Diabetes Prevention Program Outcomes Study, both lifestyle and metformin were highly effective in reducing progression to diabetes during a 10-year follow-up period. Among women without a history of GDM, lifestyle but not metformin reduced progression to diabetes.
Authors: Caballero MT, Serra ME, Acosta PL, Marzec J, Gibbons L, Salim M, Rodriguez A, Reynaldi A, Garcia A, Bado D, Buchholz UJ, Hijano DR, Coviello S, Newcomb D, Bellabarba M, Ferolla FM, Libster R, Berenstein A, Siniawaski S, Blumetti V, Echavarria M, Pinto L, Lawrence A, Ossorio MF, Grosman A, Mateu CG, Bayle C, Dericco A, Pellegrini M, Igarza I, Repetto HA, Grimaldi LA, Gudapati P, Polack NR, Althabe F, Shi M, Ferrero F, Bergel E, Stein RT, Peebles RS, Boothby M, Kleeberger SR, Polack FP.
Journal: J Clin Invest. 2015 Feb;125(2):571-82. doi: 10.1172/JCI75183
While 30%-70% of RSV-infected infants develop bronchiolitis, 2% require hospitalization. It is not clear why disease severity differs among healthy, full-term infants; however, virus titers, inflammation, and Th2 bias are proposed explanations. While TLR4 is associated with these disease phenotypes, the role of this receptor in respiratory syncytial virus (RSV) pathogenesis is controversial. Here, we evaluated the interaction between TLR4 and environmental factors in RSV disease and defined the immune mediators associated with severe illness. Two independent populations of infants with RSV bronchiolitis revealed that the severity of RSV infection is determined by the TLR4 genotype of the individual and by environmental exposure to LPS. RSV-infected infants with severe disease exhibited a high GATA3/T-bet ratio, which manifested as a high IL-4/IFN-γ ratio in respiratory secretions. The IL-4/IFN-γ ratio present in infants with severe RSV is indicative of Th2 polarization. Murine models of RSV infection confirmed that LPS exposure, Tlr4 genotype, and Th2 polarization influence disease phenotypes. Together, the results of this study identify environmental and genetic factors that influence RSV pathogenesis and reveal that a high IL-4/IFN-γ ratio is associated with severe disease. Moreover, these molecules should be explored as potential targets for therapeutic intervention.
Authors: Naik S, Bouladoux N, Linehan JL, Han SJ, Harrison OJ, Wilhelm C, Conlan S, Himmelfarb S, Byrd AL, Deming C, Quinones M, Brenchley JM, Kong HH, Tussiwand R, Murphy KM, Merad M, Segre JA, Belkaid Y
Journal: Nature. 2015 Jan 5. doi: 10.1038/nature14052. [Epub ahead of print]
The skin represents the primary interface between the host and the environment. This organ is also home to trillions of microorganisms that play an important role in tissue homeostasis and local immunity. Skin microbial communities are highly diverse and can be remodelled over time or in response to environmental challenges. How, in the context of this complexity, individual commensal microorganisms may differentially modulate skin immunity and the consequences of these responses for tissue physiology remains unclear. Here we show that defined commensals dominantly affect skin immunity and identify the cellular mediators involved in this specification. In particular, colonization with Staphylococcus epidermidis induces IL-17A+ CD8+ T cells that home to the epidermis, enhance innate barrier immunity and limit pathogen invasion. Commensal-specific T-cell responses result from the coordinated action of skin-resident dendritic cell subsets and are not associated with inflammation, revealing that tissue-resident cells are poised to sense and respond to alterations in microbial communities. This interaction may represent an evolutionary means by which the skin immune system uses fluctuating commensal signals to calibrate barrier immunity and provide heterologous protection against invasive pathogens. These findings reveal that the skin immune landscape is a highly dynamic environment that can be rapidly and specifically remodelled by encounters with defined commensals, findings that have profound implications for our understanding of tissue-specific immunity and pathologies.