Correction: The Endocytic Adaptor Eps15 Controls Marginal Zone B Cell Numbers.

Eps15 is an endocytic adaptor protein involved in clathrin and non-clathrin mediated endocytosis. In Caenorhabditis elegans and Drosophila melanogaster lack of Eps15 leads to defects in synaptic vesicle recycling and synapse formation. We generated Eps15-KO mice to investigate its function in mammals. Eps15-KO mice are born at the expected Mendelian ratio and are fertile. Using a large-scale phenotype screen covering more than 300 parameters correlated to human disease, we found that Eps15-KO mice did not show any sign of disease or neural deficits. Instead, altered blood parameters pointed to an immunological defect. By competitive bone marrow transplantation we demonstrated that Eps15-KO hematopoietic precursor cells were more efficient than the WT counterparts in repopulating B220⁺ bone marrow cells, CD19⁻ thymocytes and splenic marginal zone (MZ) B cells. Eps15-KO mice showed a 2-fold increase in MZ B cell numbers when compared with controls. Using reverse bone marrow transplantation, we found that Eps15 regulates MZ B cell numbers in a cell autonomous manner. FACS analysis showed that although MZ B cells were increased in Eps15-KO mice, transitional and pre-MZ B cell numbers were unaffected. The increase in MZ B cell numbers in Eps15 KO mice was not dependent on altered BCR signaling or Notch activity. In conclusion, in mammals, the endocytic adaptor protein Eps15 is a regulator of B-cell lymphopoiesis

Constitutive CD40 signaling in B cells selectively activates the noncanonical NF-κB pathway and promotes lymphomagenesis

CD40, a member of the tumor necrosis factor (TNF) receptor family, plays an essential role in T cell–dependent immune responses. Because CD40 is widely expressed on the surface of tumor cells in various B cell malignancies, deregulated CD40 signaling has been suggested to contribute to lymphomagenesis. In this study, we show that B cell-specific expression of a constitutively active CD40 receptor, in the form of a latent membrane protein 1 (LMP1)/CD40 chimeric protein, promoted an increase in the number of follicular and marginal zone B cells in secondary lymphoid organs in transgenic mice. The B cells displayed an activated phenotype, prolonged survival and increased proliferation, but were significantly impaired in T cell-dependent immune responses. Constitutive CD40 signaling in B cells induced selective and constitutive activation of the noncanonical NF-κB pathway and the mitogen-activated protein kinases Jnk and extracellular signal–regulated kinase. LMP1/CD40-expressing mice older than 12 mo developed B cell lymphomas of mono- or oligoclonal origin at high incidence, thus showing that the interplay of the signaling pathways induced by constitutive CD40 signaling is sufficient to initiate a tumorigenic process, ultimately leading to the development of B cell lymphomas

A Spatially Resolved Dark- versus Light-Zone Microenvironment Signature Subdivides Germinal Center-Related Aggressive B Cell Lymphomas

We applied digital spatial profiling for 87 immune and stromal genes to lymph node germinal center (GC) dark- and light-zone (DZ/LZ) regions of interest to obtain a differential signature of these two distinct microenvironments. The spatially resolved 53-genes signature, comprising key genes of the DZmutational machinery and LZ immune and mesenchymal milieu, was applied to the transcriptomes of 543 GC-related diffuse large B cell lymphomas and double-hit ( DH) lymphomas. According to the DZ/LZ signature, the GC-related lymphomas were sub-classified into two clusters. The subgroups differed in the distribution of DH cases and survival, with most DH displaying a distinct DZ-like profile. The clustering analysis was also performed using a 25-genes signature composed of genes positively enriched in the non-B, stromal sub-compartments, for the first time achieving DZ/LZ discrimination based on stromal/immune features. The report offers new insight into the GC microenvironment, hinting at a DZ microenvironment of origin in DH lymphomas

PLC-γ2 is essential for formation and maintenance of memory B cells

Resting antigen-experienced memory B cells are thought to be responsible for the more rapid and robust antibody responses after antigen reencounter, which are the hallmark of memory humoral responses. The molecular basis for the development and survival of memory B cells remains largely unknown. We report that phospholipase C (PLC) γ2 is required for efficient formation of germinal center (GC) and memory B cells. Moreover, memory B cell homeostasis is severely hampered by inducible loss of PLC-γ2. Accordingly, mice with a conditional deletion of PLC-γ2 in post-GC B cells had an almost complete abrogation of the secondary antibody response. Collectively, our data suggest that PLC-γ2 conveys a survival signal to GC and memory B cells and that this signal is required for a productive secondary immune response

Polycomb proteins control proliferation and transformation independently of cell cycle checkpoints by regulating DNA replication

The ability of PRC1 and PRC2 to promote proliferation is a main feature that links polycomb (PcG) activity to cancer. PcGs silence the expression of the tumour suppressor locus Ink4a/Arf, whose products positively regulate pRb and p53 functions. Enhanced PcG activity is a frequent feature of human tumours, and PcG inhibition has been proposed as a strategy for cancer treatment. However, the recurrent inactivation of pRb/p53 responses in human cancers raises a question regarding the ability of PcG proteins to affect cellular proliferation independently from this checkpoint. Here we demonstrate that PRCs regulate cellular proliferation and transformation independently of the Ink4a/Arf-pRb-p53 pathway. We provide evidence that PRCs localize at replication forks, and that loss of their function directly affects the progression and symmetry of DNA replication forks. Thus, we have identified a novel activity by which PcGs can regulate cell proliferation independently of major cell cycle restriction checkpoints. \ua92014 Macmillan Publishers Limited. All rights reserved

Germinal center dysregulation by histone methyltransferase EZH2 promotes lymphomagenesis

Protection against deadly pathogens requires the production of high-affinity antibodies by B cells, which are generated in germinal centers (GCs). Alteration of the GC developmental program is common in many B cell malignancies. Identification of regulators of the GC response is crucial to develop targeted therapies for GC B cell dysfunctions, including lymphomas. The histone H3 lysine 27 methyltransferase enhancer of zeste homolog 2 (EZH2) is highly expressed in GC B cells and is often constitutively activated in GC-derived non-Hodgkin lymphomas (NHLs). The function of EZH2 in GC B cells remains largely unknown. Herein, we show that Ezh2 inactivation in mouse GC B cells caused profound impairment of GC responses, memory B cell formation, and humoral immunity. EZH2 protected GC B cells against activation-induced cytidine deaminase (AID) mutagenesis, facilitated cell cycle progression, and silenced plasma cell determinant and tumor suppressor B-lymphocyte–induced maturation protein 1 (BLIMP1). EZH2 inhibition in NHL cells induced BLIMP1, which impaired tumor growth. In conclusion, EZH2 sustains AID function and prevents terminal differentiation of GC B cells, which allows antibody diversification and affinity maturation. Dysregulation of the GC reaction by constitutively active EZH2 facilitates lymphomagenesis and identifies EZH2 as a possible therapeutic target in NHL and other GC-derived B cell diseases.Published versio

A compositional modelling approach for large Sensor Networks design

Sensor Networks are required to be properly designed in order to avoid resource waste and optimize their lifetime. Large monitoring applications require proper methodologies and tools supporting the design, when multiple solutions increase the complexity of this task. Indeed, different parameters affect the performance of a solution, as node distribution, sensing coverage, battery usage, etc. A compositional modelling approach can provide early measures, allowing to evaluate and compare different solutions since the design phase. The main contribution of the paper is the definition of a general modelling framework to integrate simple models representing the main components and features of sensor networks. A library for specific sensor devices have been developed, using the Stochastic Activity Network (SAN) formalism. This approach is shown to be compositional since the creation of complex networks can be accomplished by simple subcomponents aggregation. With this approach, obtained models can analyse the dynamic evolution of the overall network, even if complex. First experimental results are also reported and discussed. �� 2013 IEEE

Nonequivalence of equivalence principles

Equivalence principles played a central role in the development of general relativity. Furthermore, they have provided operative procedures for testing the validity of general relativity, or constraining competing theories of gravitation. This has led to a flourishing of different, and inequivalent, formulations of these principles, with the undesired consequence that often the same name, "equivalence principle," is associated with statements having a quite different physical meaning. In this paper, we provide a precise formulation of the several incarnations of the equivalence principle, clarifying their uses and reciprocal relations. We also discuss their possible role as selecting principles in the design and classification of viable theories of gravitation.\ua9 2015 American Association of Physics Teachers

An integrated lifetime and network quality model of large WSNs.

This paper introduces a modeling approach to the design and evaluation of large wireless sensor networks against the topology of the network and the monitoring application and taking into account the performance degradation due to the power consumption. The model is built by composing Stochastic Activity Network (SAN) models of the nodes and a Markovian Agent Model (MAM) of the whole network. The SAN models are used to conduct a performance analysis of the nodes (i.e. to measure their sampling time) and evaluate their mean time to discharge. The MAM is used to compose the results of the SAN model analysis into a complex topology-aware model able to evaluate the Packet Delivery Ratio (PDR) and the power consumption of the network. The possibility to model spatially distributed interdependencies featured by the MAM makes the integrated model a concrete, scalable mean to evaluate different design choices and perform meaningful what-if analyses. The model has been validated by comparing the analysis results with real node values: specifically we present the experimental results obtained by using TelosB nodes equipped with TinyOs