Perturbation of Chromatin Structure Globally Affects Localization and Recruitment of Splicing Factors

Chromatin structure is an important factor in the functional coupling between transcription and mRNA processing, not only by regulating alternative splicing events, but also by contributing to exon recognition during constitutive splicing. We observed that depolarization of neuroblastoma cell membrane potential, which triggers general histone acetylation and regulates alternative splicing, causes a concentration of SR proteins in nuclear speckles. This prompted us to analyze the effect of chromatin structure on splicing factor distribution and dynamics. Here, we show that induction of histone hyper-acetylation results in the accumulation in speckles of multiple splicing factors in different cell types. In addition, a similar effect is observed after depletion of the heterochromatic protein HP1α, associated with repressive chromatin. We used advanced imaging approaches to analyze in detail both the structural organization of the speckle compartment and nuclear distribution of splicing factors, as well as studying direct interactions between splicing factors and their association with chromatin in vivo. The results support a model where perturbation of normal chromatin structure decreases the recruitment efficiency of splicing factors to nascent RNAs, thus causing their accumulation in speckles, which buffer the amount of free molecules in the nucleoplasm. To test this, we analyzed the recruitment of the general splicing factor U2AF65 to nascent RNAs by iCLIP technique, as a way to monitor early spliceosome assembly. We demonstrate that indeed histone hyper-acetylation decreases recruitment of U2AF65 to bulk 3' splice sites, coincident with the change in its localization. In addition, prior to the maximum accumulation in speckles, ∼20% of genes already show a tendency to decreased binding, while U2AF65 seems to increase its binding to the speckle-located ncRNA MALAT1. All together, the combined imaging and biochemical approaches support a model where chromatin structure is essential for efficient co-transcriptional recruitment of general and regulatory splicing factors to pre-mRNA

Signs of late infall and possible planet formation around DR Tau using VLT/SPHERE and LBTI/LMIRCam

Context. Protoplanetary disks around young stars often contain substructures like rings, gaps, and spirals that could be caused by interactions between the disk and forming planets. Aims: We aim to study the young (1-3 Myr) star DR Tau in the near-infrared and characterize its disk, which was previously resolved through submillimeter interferometry with ALMA, and to search for possible substellar companions embedded into it. Methods: We observed DR Tau with VLT/SPHERE both in polarized light (H broad band) and total intensity (in Y, J, H, and K spectral bands). We also performed L' band observations with LBTI/LMIRCam on the Large Binocular Telescope (LBT). We applied differential imaging techniques to analyze both the polarized data, using dual beam polarization imaging, and the total intensity data, using angular and spectral differential imaging. Results: We found two previously undetected spirals extending north-east and south of the star, respectively. We further detected an arc-like structure north of the star. Finally a bright, compact and elongated structure was detected at a separation of 303 ± 10 mas and a position angle 21.2 ± 3.7 degrees, just at the root of the north-east spiral arm. Since this feature is visible both in polarized light and total intensity and has a blue spectrum, itis likely caused by stellar light scattered by dust. Conclusions: The two spiral arms are at different separations from the star, have very different pitch angles, and are separated by an apparent discontinuity, suggesting they might have a different origin. The very open southern spiral arm might be caused by infalling material from late encounters with cloudlets into the formation environment of the star itself. The compact feature could be caused by interaction with a planet in formation still embedded in its dust envelope and it could be responsible for launching the north-east spiral. We estimate a mass of the putative embedded object of the order of few MJup. Reduced images are also available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/658/A63 Based on observations made with European Southern Observatory (ESO) telescopes at Paranal Observatory in Chile, under programs ID 0102.C-0453(A) and 1104.C-0416(A). It also makes partial use of LBT/LMIRCam observations under program ID 74

Quantum mass correction for the twisted kink

We present an analytic result for the 1-loop quantum mass correction in semiclassical quantization for the twisted \phi^4 kink on S^1 without explicit knowledge of the fluctuation spectrum. For this purpose we use the contour integral representation of the spectral zeta function. By solving the Bethe ansatz equations for the n=2 Lame equation we obtain an analytic expression for the corresponding spectral discriminant. We discuss the renormalization issues of this model. An energetically preferred size for the compact space is finally obtained.Comment: 18 pages, 2 figures;v2:references and discussion added, typos correcte

Characterizing the morphology of the debris disk around the low-mass star GSC 07396-00759

Context. Debris disks have commonly been studied around intermediate-mass stars. Their intense radiation fields are believed to efficiently remove the small dust grains that are constantly replenished by collisions. For lower-mass central objects, in particular M stars, the dust removal mechanism needs to be further investigated given the much weaker radiation field produced by these objects. Aims. We present new observations of the nearly edge-on disk around the pre-main-sequence M-type star GSC 07396-00759, taken with VLT/SPHERE IRDIS in dual-beam polarimetric imaging mode, with the aim to better understand the morphology of the disk, its dust properties, and the star-disk interaction via the stellar mass-loss rate.Methods. We model the polarimetric observations to characterize the location and properties of the dust grains using the Henyey-Greenstein approximation of the polarized phase function. We use the estimated phase function to evaluate the strength of the stellar winds.Results. We find that the polarized light observations are best described by an extended and highly inclined disk (i approximate to 84.3 degrees +/- 0.3) with a dust distribution centered at a radius r(0) approximate to 107 +/- 2 au. Our modeling suggests an anisotropic scattering factor g approximate to 0.6 to best reproduce the polarized phase function S-12. We also find that the phase function is reasonably well reproduced by small micron-sized dust grains with sizes s > 0.3 mu m. We discuss some of the caveats of the approach, mainly that our model probably does not fully recover the semimajor axis of the disk and that we cannot readily determine all dust properties due to a degeneracy between the grain size and the porosity.Conclusions. Even though the radius of the disk may be overestimated, our best-fit model not only reproduces the observations well but is also consistent with previous published data obtained in total intensity. Similarly to previous studies of debris disks, we suggest that using a given scattering theory might not be sufficient to fully explain key aspects, such as the shape of the phase function or the dust grain size. Taking into consideration the aforementioned caveats, we find that the average mass-loss rate of GSC 07396-00759 can be up to 500 times stronger than that of the Sun, supporting the idea that stellar winds from low-mass stars can evacuate small dust grains in an efficient way

YETI observations of the young transiting planet candidate CVSO 30 b

CVSO 30 is a unique young low-mass system, because, for the first time, a close-in transiting and a wide directly imaged planet candidates are found around a common host star. The inner companion, CVSO 30 b, is the first possible young transiting planet orbiting a previously known weak-lined T-Tauri star. With five telescopes of the 'Young Exoplanet Transit Initiative' (YETI) located in Asia, Europe and South America we monitored CVSO 30 over three years in a total of 144 nights and detected 33 fading events. In two more seasons we carried out follow-up observations with three telescopes. We can confirm that there is a change in the shape of the fading event between different observations and that the fading event even disappears and reappears. A total of 38 fading event light curves were simultaneously modelled. We derived the planetary, stellar, and geometrical properties of the system and found them slightly smaller but in agreement with the values from the discovery paper. The period of the fading event was found to be 1.36 s shorter and 100 times more precise than the previous published value. If CVSO 30 b would be a giant planet on a precessing orbit, which we cannot confirm, yet, the precession period may be shorter than previously thought. But if confirmed as a planet it would be the youngest transiting planet ever detected and will provide important constraints on planet formation and migration time-scales.Comment: 14 pages (20 with appendix), 7 figures (16 with appendix), 6 tables (7 with appendix

Quantum kink and its excitations

We show how detailed properties of a kink in quantum field theory can be extracted from field correlation functions. This makes it possible to study quantum kinks in a fully non-perturbative way using Monte Carlo simulations. We demonstrate this by calculating the kink mass as well as the spectrum and approximate wave functions of its excitations. This way of measuring the kink mass has clear advantages over the existing approaches based on creation and annihilation operators or the kink free energy. Our methods are straightforward to generalise to more realistic theories and other defect types.Comment: 21 pages, 11 figures, v2: typos corrected, references adde

One-loop spectroscopy of semiclassically quantized strings: bosonic sector

We make a further step in the analytically exact quantization of spinning string states in semiclassical approximation, by evaluating the exact one-loop partition function for a class of two-spin string solutions for which quadratic fluctuations form a non-trivial system of coupled modes. This is the case of a folded string in the SU(2) sector, in the limit described by a quantum Landau–Lifshitz model. The same applies to the full bosonic sector of fluctuations over the folded spinning string in AdS5 with an angular momentum J in S5. Fluctuations are governed by a special class of fourth-order differential operators, with coefficients being meromorphic functions on the torus, which we are able to solve exactly

Is undernutrition prognostic of infection complications in children undergoing surgery? A systematic review

Background: Healthcare-associated infections are costly and are increasingly viewed as an indicator of the quality of care. Although strategies to reduce infections have become widespread, few studies have formally investigated the role of undernutrition on the development of infection-related complications in children after surgery. Aim: To perform a systematic review of the literature to determine if undernutrition is prognostic of postoperative infection complications in children. Methods: Electronic bibliographic and research databases were searched from 1950 to 2014. Inclusion criteria were studies in children (age <18 years) evaluating pre-operative nutritional status and reporting postoperative infection complications. Quality assessment was performed independently by two reviewers, with disagreements resolved by a third reviewer. The quality of the evidence was judged to be low in the majority of studies. Findings: Ten cohort and two caseecontrol studies met the inclusion criteria. Five studies reported an outcome combining infection-related complications, with the remainder reporting individual infection complications. Six studies reported surgical site infection (SSI) alone or in combination with other infection complications. Direct comparison between studies was difficult due to clinical and diagnostic heterogeneity. Unadjusted analyses (for patient or clinical variables) were suggestive of a relationship between undernutrition and infection complications. In studies controlling for other variables, the analyses did not remain significant for SSI. Conclusion: There was low-quality evidence that undernutrition may be predictive of postoperative infection complications in children, with the exception of SSI. However, inconsistencies in nutritional and outcome assessments made it difficult to draw conclusions. Larger, high-quality studies are warranted to further investigate a potential prognostic relationship

Debris Disks: Probing Planet Formation

Debris disks are the dust disks found around ~20% of nearby main sequence stars in far-IR surveys. They can be considered as descendants of protoplanetary disks or components of planetary systems, providing valuable information on circumstellar disk evolution and the outcome of planet formation. The debris disk population can be explained by the steady collisional erosion of planetesimal belts; population models constrain where (10-100au) and in what quantity (>1Mearth) planetesimals (>10km in size) typically form in protoplanetary disks. Gas is now seen long into the debris disk phase. Some of this is secondary implying planetesimals have a Solar System comet-like composition, but some systems may retain primordial gas. Ongoing planet formation processes are invoked for some debris disks, such as the continued growth of dwarf planets in an unstirred disk, or the growth of terrestrial planets through giant impacts. Planets imprint structure on debris disks in many ways; images of gaps, clumps, warps, eccentricities and other disk asymmetries, are readily explained by planets at >>5au. Hot dust in the region planets are commonly found (<5au) is seen for a growing number of stars. This dust usually originates in an outer belt (e.g., from exocomets), although an asteroid belt or recent collision is sometimes inferred.Comment: Invited review, accepted for publication in the 'Handbook of Exoplanets', eds. H.J. Deeg and J.A. Belmonte, Springer (2018