Germ cells commit somatic stem cells to differentiation following priming by PI3K/Tor activity in the Drosophila testis

How and when potential becomes restricted in differentiating stem cell daughters is poorly understood. While it is thought that signals from the niche are actively required to prevent differentiation, another model proposes that stem cells can reversibly transit between multiple states, some of which are primed, but not committed, to differentiate. In the Drosophila testis, somatic cyst stem cells (CySCs) generate cyst cells, which encapsulate the germline to support its development. We find that CySCs are maintained independently of niche self-renewal signals if activity of the PI3K/Tor pathway is inhibited. Conversely, PI3K/Tor is not sufficient alone to drive differentiation, suggesting that it acts to license cells for differentiation. Indeed, we find that the germline is required for differentiation of CySCs in response to PI3K/Tor elevation, indicating that final commitment to differentiation involves several steps and intercellular communication. We propose that CySC daughter cells are plastic, that their fate depends on the availability of neighbouring germ cells, and that PI3K/Tor acts to induce a primed state for CySC daughters to enable coordinated differentiation with the germline

Deux méthodes de comparaison d'images pour l'identification d'objets à partir de données prospectives

Cette étude aborde le problème de l'identification d'objets mobiles à partir de données délivrées par un senseur prospectif dont la conception est actuellement en cours. Le but est d'estimer la faisabilité d'une telle identification à l'aide d'outils disponibles à ce jour en reconnaissance des formes. On présente dans ce papier la réalisation complète d'une chaîne de simulation, comprenant à la fois la génération des données (non disponibles) et la mise en place de processus capables de les exploiter dans un but d'identification. Des paramètres variables contrôlent la nature des images (richesse, niveau de bruit) tout au long de la simulation, ceci afin de pouvoir prendre en compte des données de qualité variable

Monitoring global protein thiol-oxidation and protein S-mycothiolation in Mycobacterium smegmatis under hypochlorite stress.

Hillion M, Bernhardt J, Busche T, et al. Monitoring global protein thiol-oxidation and protein S-mycothiolation in Mycobacterium smegmatis under hypochlorite stress. Sci Rep. 2017;7(1): 1195.Mycothiol (MSH) is the major low molecular weight (LMW) thiol in Actinomycetes. Here, we used shotgun proteomics, OxICAT and RNA-seq transcriptomics to analyse protein S-mycothiolation, reversible thiol-oxidations and their impact on gene expression in Mycobacterium smegmatis under hypochlorite stress. In total, 58 S-mycothiolated proteins were identified under NaOCl stress that are involved in energy metabolism, fatty acid and mycolic acid biosynthesis, protein translation, redox regulation and detoxification. Protein S-mycothiolation was accompanied by MSH depletion in the thiol-metabolome. Quantification of the redox state of 1098 Cys residues using OxICAT revealed that 381 Cys residues (33.6%) showed >10% increased oxidations under NaOCl stress, which overlapped with 40 S-mycothiolated Cys-peptides. The absence of MSH resulted in a higher basal oxidation level of 338 Cys residues (41.1%). The RseA and RshA anti-sigma factors and the Zur and NrdR repressors were identified as NaOCl-sensitive proteins and their oxidation resulted in an up-regulation of the SigH, SigE, Zur and NrdR regulons in the RNA-seq transcriptome. In conclusion, we show here that NaOCl stress causes widespread thiol-oxidation including protein S-mycothiolation resulting in induction of antioxidant defense mechanisms in M. smegmatis. Our results further reveal that MSH is important to maintain the reduced state of protein thiols

Circulating autoreactive proteinase 3(+) B cells and tolerance checkpoints in ANCA-associated vasculitis

BACKGROUND: Little is known about the autoreactive B cells in antineutrophil cytoplasmic antibody–associated (ANCA-associated) vasculitis (AAV). We aimed to investigate tolerance checkpoints of circulating antigen-specific proteinase 3–reactive (PR3(+)) B cells. METHODS: Multicolor flow cytometry in combination with bioinformatics and functional in vitro studies were performed on baseline samples of PBMCs from 154 well-characterized participants of the RAVE trial (NCT00104299) with severely active PR3-AAV and myeloperoxidase-AAV (MPO-AAV) and 27 healthy controls (HCs). Clinical data and outcomes from the trial were correlated with PR3(+) B cells (total and subsets). RESULTS: The frequency of PR3(+) B cells among circulating B cells was higher in participants with PR3-AAV (4.77% median [IQR, 3.98%–6.01%]) than in participants with MPO-AAV (3.16% median [IQR, 2.51%–5.22%]) and participants with AAV compared with HCs (1.67% median [IQR, 1.27%–2.16%], P < 0.001 for all comparisons), implying a defective central tolerance checkpoint in patients with AAV. Only PBMCs from participants with PR3-AAV contained PR3(+) B cells capable of secreting PR3-ANCA IgG in vitro, proving they were functionally distinct from those of participants with MPO-AAV and HCs. Unsupervised clustering identified subtle subsets of atypical autoreactive PR3(+) memory B cells accumulating through the maturation process in patients with PR3-AAV. PR3(+) B cells were enriched in the memory B cell compartment of participants with PR3-AAV and were associated with higher serum CXCL13 levels, suggesting an increased germinal center activity. PR3(+) B cells correlated with systemic inflammation (C-reactive protein and erythrocyte sedimentation rate, P < 0.05) and complete remission (P < 0.001). CONCLUSION: This study suggests the presence of defective central antigen-independent and peripheral antigen-dependent checkpoints in patients with PR3-AAV, elucidating the selection process of autoreactive B cells. TRIAL REGISTRATION: ClinicalTrials.gov NCT00104299. FUNDING: The Vasculitis Foundation, the National Institute of Allergy and Infectious Diseases of the NIH, and the Mayo Foundation for Education and Research

On the Existence of Undistorted Progressive Waves (UPWs) of Arbitrary Speeds 0≤v<∞0 \leq v< \infty in Nature

We present the theory, the experimental evidence, and fundamental physical consequences concerning the existence of families of undistorted progressive waves (UPWs) of arbitrary speeds $0\leq v < \infty$, which are solutions of the homogeneous wave equation, Maxwell equations, and Dirac and Weyl equations.Comment: 77 pages, Latex article, with figures. Includes corrections to the published versio

Low Temperature Ferromagnetism in Chemically Ordered FeRh Nanocrystals

In sharp contrast to previous studies on FeRh bulk, thin films, and nanoparticles, we report the persistence of ferromagnetic order down to 3 K for size-selected 3.3 nm diameter nanocrystals embedded into an amorphous carbon matrix. The annealed nanoparticles have a B2 structure with alternating atomic Fe and Rh layers. X-ray magnetic dichroism and superconducting quantum interference device measurements demonstrate ferromagnetic alignment of the Fe and Rh magnetic moments of 3 and 1 mu(B), respectively. The ferromagnetic order is ascribed to the finite-size induced structural relaxation observed in extended x-ray absorption spectroscopy. DOI: 10.1103/PhysRevLett.110.08720

The P2Y4 receptor forms homo-oligomeric complexes in several CNS and PNS neuronal cells

It is well established that several cell surface receptors interact with each other to form dimers and oligomers, which are essential for their activation. Since little is known about the quaternary structure of P2Y receptors, in the present work, we investigated the expression of the G-protein-coupled P2Y4 subunit as monomeric or higher-order complex protein. We examined both endogenously expressed P2Y4 subtype with the aid of specific anti-P2Y4 antiserum, and heterologously transfected P2Y4-tagged receptors with the use of antitag antibodies. In both cases, we found the P2Y4 receptor displaying molecular masses corresponding to monomeric, dimeric and oligomeric structures. Experiments performed in the absence of reducing agents demonstrated that there is a strict correlation among the multiple protein bands and that the multimeric forms are at least partially assembled by disulphide bonds. The direct demonstration of P2Y4 homodimerisation comes instead from co–transfection and differential co–immunoprecipitation experiments, with the use of differently tagged P2Y4 receptors and antitag antibodies. The structural propensity of the P2Y4 protein to form homo-oligomers may open the possibility of a novel regulatory mechanism of physiopathological functions for this and additional P2Y receptors