lin-28 Controls the Succession of Cell Fate Choices via Two Distinct Activities

lin-28 is a conserved regulator of cell fate succession in animals. In Caenorhabditis elegans, it is a component of the heterochronic gene pathway that governs larval developmental timing, while its vertebrate homologs promote pluripotency and control differentiation in diverse tissues. The RNA binding protein encoded by lin-28 can directly inhibit let-7 microRNA processing by a novel mechanism that is conserved from worms to humans. We found that C. elegans LIN-28 protein can interact with four distinct let-7 family pre-microRNAs, but in vivo inhibits the premature accumulation of only let-7. Surprisingly, however, lin-28 does not require let-7 or its relatives for its characteristic promotion of second larval stage cell fates. In other words, we find that the premature accumulation of mature let-7 does not account for lin-28's precocious phenotype. To explain let-7's role in lin-28 activity, we provide evidence that lin-28 acts in two steps: first, the let-7–independent positive regulation of hbl-1 through its 3′UTR to control L2 stage-specific cell fates; and second, a let-7–dependent step that controls subsequent fates via repression of lin-41. Our evidence also indicates that let-7 functions one stage earlier in C. elegans development than previously thought. Importantly, lin-28's two-step mechanism resembles that of the heterochronic gene lin-14, and the overlap of their activities suggests a clockwork mechanism for developmental timing. Furthermore, this model explains the previous observation that mammalian Lin28 has two genetically separable activities. Thus, lin-28's two-step mechanism may be an essential feature of its evolutionarily conserved role in cell fate succession

Photo-antagonism of the GABAA receptor

Neurotransmitter receptor trafficking is fundamentally important for synaptic transmission and neural network activity. GABAA receptors and inhibitory synapses are vital components of brain function, yet much of our knowledge regarding receptor mobility and function at inhibitory synapses is derived indirectly from using recombinant receptors, antibody-tagged native receptors and pharmacological treatments. Here we describe the use of a set of research tools that can irreversibly bind to and affect the function of recombinant and neuronal GABAA receptors following ultraviolet photoactivation. These compounds are based on the competitive antagonist gabazine and incorporate a variety of photoactive groups. By using site-directed mutagenesis and ligand-docking studies, they reveal new areas of the GABA binding site at the interface between receptor β and α subunits. These compounds enable the selected inactivation of native GABAA receptor populations providing new insight into the function of inhibitory synapses and extrasynaptic receptors in controlling neuronal excitation

Social functioning and behaviour in Mucopolysaccharidosis IH [Hurlers Syndrome]

Background: Mucopolysaccharidosis type IH (MPS-IH) [Hurlers Syndrome] is a developmental genetic disorder characterised by severe physical symptoms and cognitive decline. This study aimed to investigate the behavioural phenotype of MPS-IH treated by haematopoietic cell transplantation, focusing on social functioning and sleep. Parental stress was also measured. Methods: Participants were 22 children with MPS-IH (mean age 9 years 1 month), of whom 10 were male (45%). Parents completed the Social Responsiveness Scale (SRS), Child Behaviour Checklist (CBCL), Children’s Sleep Habit Questionnaire and Parent Stress Index, Short Form (PSI-SF). Results: Twenty-three per cent of children with MPS-IH scored in the severe range of the SRS, suggesting significant difficulties in social functioning. Children with MPS-IH were more than 30 times more likely to receive scores in the severe range than typically developing children. Thirty-six per cent scored in the mild-to-moderate range, suggesting milder, but marked, difficulties in social interaction. Although children with MPS-IH did not show significantly higher rates of internalising, externalising or total behaviour problems than the normative sample, they received scores that were significantly higher on social, thought and attention problems and rule-breaking behaviour, and all the competence areas of the CBCL. Parents of children with MPS-IH did not score significantly higher on parental stress than parents in a normative sample. Conclusions: Parents of children with MPS-IH rate their children as having problems with social functioning and various areas of competence more frequently than previously thought, with implications for clinical support

The Volunteer Satisfaction Index: A Validation Study in the Chinese Cultural Context

Using a Hong Kong-sourced sample of 261 participants, this study set out to validate the Volunteer Satisfaction Index (VSI) in the Chinese cultural context and to evaluate its psychometric properties. The VSI was originally developed by Galindo-Kuhn and Guzley (2001) to measure the outcomes of volunteer experiences. In this study, exploratory factor analysis (EFA) yielded a different factor structure from that proposed by the scale developer. The three factors found were personal gain, relationship within organization and relationship with peers. Cronbach’s alpha values were high for all three subscales. Results from correlation and regression analysis also confirmed the construct and criterion-related validity of the scale. Thus, the reliability and validity of the scale were confirmed. Implications for the assessment of volunteer satisfaction and further directions for cross-cultural studies on related topics are discussed

DAF-12 Regulates a Connected Network of Genes to Ensure Robust Developmental Decisions

The nuclear receptor DAF-12 has roles in normal development, the decision to pursue dauer development in unfavorable conditions, and the modulation of adult aging. Despite the biologic importance of DAF-12, target genes for this receptor are largely unknown. To identify DAF-12 targets, we performed chromatin immunoprecipitation followed by hybridization to whole-genome tiling arrays. We identified 1,175 genomic regions to be bound in vivo by DAF-12, and these regions are enriched in known DAF-12 binding motifs and act as DAF-12 response elements in transfected cells and in transgenic worms. The DAF-12 target genes near these binding sites include an extensive network of interconnected heterochronic and microRNA genes. We also identify the genes encoding components of the miRISC, which is required for the control of target genes by microRNA, as a target of DAF-12 regulation. During reproductive development, many of these target genes are misregulated in daf-12(0) mutants, but this only infrequently results in developmental phenotypes. In contrast, we and others have found that null daf-12 mutations enhance the phenotypes of many miRISC and heterochronic target genes. We also find that environmental fluctuations significantly strengthen the weak heterochronic phenotypes of null daf-12 alleles. During diapause, DAF-12 represses the expression of many heterochronic and miRISC target genes, and prior work has demonstrated that dauer formation can suppress the heterochronic phenotypes of many of these target genes in post-dauer development. Together these data are consistent with daf-12 acting to ensure developmental robustness by committing the animal to adult or dauer developmental programs despite variable internal or external conditions

Transfer of MicroRNAs by Embryonic Stem Cell Microvesicles

Microvesicles are plasma membrane-derived vesicles released into the extracellular environment by a variety of cell types. Originally characterized from platelets, microvesicles are a normal constituent of human plasma, where they play an important role in maintaining hematostasis. Microvesicles have been shown to transfer proteins and RNA from cell to cell and they are also believed to play a role in intercellular communication. We characterized the RNA and protein content of embryonic stem cell microvesicles and show that they can be engineered to carry exogenously expressed mRNA and protein such as green fluorescent protein (GFP). We demonstrate that these engineered microvesicles dock and fuse with other embryonic stem cells, transferring their GFP. Additionally, we show that embryonic stem cells microvesicles contain abundant microRNA and that they can transfer a subset of microRNAs to mouse embryonic fibroblasts in vitro. Since microRNAs are short (21–24 nt), naturally occurring RNAs that regulate protein translation, our findings open up the intriguing possibility that stem cells can alter the expression of genes in neighboring cells by transferring microRNAs contained in microvesicles. Embryonic stem cell microvesicles may be useful therapeutic tools for transferring mRNA, microRNAs, protein, and siRNA to cells and may be important mediators of signaling within stem cell niches

Jet energy measurement with the ATLAS detector in proton-proton collisions at root s=7 TeV

The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of √s = 7TeV corresponding to an integrated luminosity of 38 pb-1. Jets are reconstructed with the anti-kt algorithm with distance parameters R=0. 4 or R=0. 6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta pT≥20 GeV and pseudorapidities {pipe}η{pipe}<4. 5. The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations. The jet energy uncertainty is less than 2. 5 % in the central calorimeter region ({pipe}η{pipe}<0. 8) for jets with 60≤pT<800 GeV, and is maximally 14 % for pT<30 GeV in the most forward region 3. 2≤{pipe}η{pipe}<4. 5. The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon pT, the sum of the transverse momenta of tracks associated to the jet, or a system of low-pT jets recoiling against a high-pT jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response. The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-pT jets. Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating from light quarks, heavy quarks or gluons are also discussed and the corresponding uncertainties are determined. © 2013 CERN for the benefit of the ATLAS collaboration

Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector

Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente

Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

The inclusive and dijet production cross-sections have been measured for jets containing b-hadrons (b-jets) in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV, using the ATLAS detector at the LHC. The measurements use data corresponding to an integrated luminosity of 34 pb^-1. The b-jets are identified using either a lifetime-based method, where secondary decay vertices of b-hadrons in jets are reconstructed using information from the tracking detectors, or a muon-based method where the presence of a muon is used to identify semileptonic decays of b-hadrons inside jets. The inclusive b-jet cross-section is measured as a function of transverse momentum in the range 20 < pT < 400 GeV and rapidity in the range |y| < 2.1. The bbbar-dijet cross-section is measured as a function of the dijet invariant mass in the range 110 < m_jj < 760 GeV, the azimuthal angle difference between the two jets and the angular variable chi in two dijet mass regions. The results are compared with next-to-leading-order QCD predictions. Good agreement is observed between the measured cross-sections and the predictions obtained using POWHEG + Pythia. MC@NLO + Herwig shows good agreement with the measured bbbar-dijet cross-section. However, it does not reproduce the measured inclusive cross-section well, particularly for central b-jets with large transverse momenta.Comment: 10 pages plus author list (21 pages total), 8 figures, 1 table, final version published in European Physical Journal