Nonparametric estimation of a renewal reward process from discrete data

We study the nonparametric estimation of the jump density of a renewal reward process from one discretely observed sample path over [0,T]. We consider the regime when the sampling rate goes to 0. The main difficulty is that a renewal reward process is not a Levy process: the increments are non stationary and dependent. We propose an adaptive wavelet threshold density estimator and study its performance for the Lp loss over Besov spaces. We achieve minimax rates of convergence for sampling rates that vanish with T at polynomial rate. In the same spirit as Buchmann and Gr\"ubel (2003) and Duval (2012), the estimation procedure is based on the inversion of the compounding operator. The inverse has no closed form expression and is approached with a fixed point technique.Comment: arXiv admin note: substantial text overlap with arXiv:1203.313

Discussion on the paper ''Hypotheses testing by convex optimization'' by A. Goldenschluger, A. Juditsky and A. Nemirovski.

International audienceTesting statistical composite hypotheses is a very difficult area of the mathematical statistics theory and optimal solutions are found in very seldom cases. It is precisely in this respect that the paper ''Hypotheses testing by convex optimization'' brings a new insight and a powerful contribution. The optimality of solutions depends strongly on the criterion adopted for measuring the risk of a statistical procedure. In our opinion, the novelty here lies in the introduction of a new criterion different from the usual one. In the present discussion, we give some more precise details on the main results necessary to enlighten the strength and the limits of the new theory

Diachronique des arrangements contractuels dans le marché des céréales du Bassin Parisien

L’environnement institutionnel des marchés européens des céréales a évolué très significativement ces deux dernières décennies avec une dérégulation communautaire des marchés agricoles alors que jusqu’au début des années 2000, la Politique Agricole Commune protégeait les agriculteurs européens de la volatilité des marchés des commodités agricoles mondiaux. De nombreux auteurs se sont interrogés sur les effets de ces changements de politiques sur les pratiques de gestion de la mise en marché par les producteurs. Au regard des chocs répercutés le long de la filière blé tendre française, on peut s’interroger sur le rôle du contrat dans l’élaboration des choix de production et de commercialisation des producteurs. Le marché du blé tendre est-il-aussi impersonnel et proche du spot que ce que l’on pourrait croire au vu des volumes produits et échangés ? Les modèles d’analyse économique développés jusqu’ici postulent que les arrangements contractuels s’adaptent de façon fluide aux conditions conjoncturelles et aux des agents. Ils ne prennent pas en compte l’inertie des contrats ainsi que de leur environnement institutionnel et explicitent insuffisamment le rôle des paramètres qualitatifs. Nous proposons une contribution au renouvellement de l’analyse des relations amont-aval en essayant d’amener une perspective moins frustre des marchés de commodités en nous appuyant sur une base de données relative aux transactions effectuées par une coopérative céréalière du Bassin Parisien

Hit-and-Run Epigenetic Editing for Vectors of Snail-Borne Parasitic Diseases

Snail-borne parasitic diseases represent an important challenge to human and animal health. Control strategies that target the intermediate snail host has proved very effective. Epigenetic mechanisms are involved in developmental processes and therefore play a fundamental role in developmental variation. DNA methylation is an important epigenetic information carrier in eukaryotes that plays a major role in the control of chromatin structure. Epigenome editing tools have been instrumental to demonstrate functional importance of this mark for gene expression in vertebrates. In invertebrates, such tools are missing, and the role of DNA methylation remains unknown. Here we demonstrate that methylome engineering can be used to modify in vivo the CpG methylation level of a target gene in the freshwater snail Biomphalaria glabrata, intermediate host of the human parasite Schistosoma mansoni. We used a dCas9-SunTag-DNMT3A complex and synthetic sgRNA to transfect B. glabrata embryos and observed an increase of CpG methylation at the target site in 50% of the hatching snails

Schistosoma mansoni Mucin gene (SmPoMuc) expression: epigenetic control to shape adaptation to a new host

The digenetic trematode Schistosoma mansoni is a human parasite that uses the mollusc Biomphalaria glabrata as intermediate host. Specific S. mansoni strains can infect efficiently only certain B. glabrata strains (compatible strain) while others are incompatible. Strain-specific differences in transcription of a conserved family of polymorphic mucins (SmPoMucs) in S. mansoni are the principle determinants for this compatibility. In the present study, we investigated the bases of the control of SmPoMuc expression that evolved to evade B. glabrata diversified antigen recognition molecules. We compared the DNA sequences and chromatin structure of SmPoMuc promoters of two S. mansoni strains that are either compatible (C) or incompatible (IC) with a reference snail host. We reveal that although sequence differences are observed between active promoter regions of SmPoMuc genes, the sequences of the promoters are not diverse and are conserved between IC and C strains, suggesting that genetics alone cannot explain the evolution of compatibility polymorphism. In contrast, promoters carry epigenetic marks that are significantly different between the C and IC strains. Moreover, we show that modifications of the structure of the chromatin of the parasite modify transcription of SmPoMuc in the IC strain compared to the C strain and correlate with the presence of additional combinations of SmPoMuc transcripts only observed in the IC phenotype. Our results indicate that transcription polymorphism of a gene family that is responsible for an important adaptive trait of the parasite is epigenetically encoded. These strain-specific epigenetic marks are heritable, but can change while the underlying genetic information remains stable. This suggests that epigenetic changes may be important for the early steps in the adaptation of pathogens to new hosts, and might be an initial step in adaptive evolution in general

Sex-Biased Transcriptome of Schistosoma mansoni: Host-Parasite Interaction, Genetic Determinants and Epigenetic Regulators Are Associated with Sexual Differentiation

Background Among more than 20,000 species of hermaphroditic trematodes, Schistosomatidae are unusual since they have evolved gonochorism. In schistosomes, sex is determined by a female heterogametic system, but phenotypic sexual dimorphism appears only after infection of the vertebrate definitive host. The completion of gonad maturation occurs even later, after pairing. To date, the molecular mechanisms that trigger the sexual differentiation in these species remain unknown, and in vivo studies on the developing schistosomulum stages are lacking. To study the molecular basis of sex determination and sexual differentiation in schistosomes, we investigated the whole transcriptome of the human parasite Schistosoma mansoni in a stage-and sex-comparative manner. Methodology/Principal Findings We performed a RNA-seq on males and females for five developmental stages: cercariae larvae, three in vivo schistosomulum stages and adults. We detected 7,168 genes differentially expressed between sexes in at least one of the developmental stages, and 4,065 of them were functionally annotated. Transcriptome data were completed with H3K27me3 histone modification analysis using ChIP-Seq before (in cercariae) and after (in adults) the phenotypic sexual dimorphism appearance. In this paper we present (i) candidate determinants of the sexual differentiation, (ii) sex-biased players of the interaction with the vertebrate host, and (iii) different dynamic of the H3K27me3 histone mark between sexes as an illustration of sex-biased epigenetic landscapes. Conclusions/Significance Our work presents evidence that sexual differentiation in S. mansoni is accompanied by distinct male and female transcriptional landscapes of known players of the host-parasite crosstalk, genetic determinants and epigenetic regulators. Our results suggest that such combination could lead to the optimized sexual dimorphism of this parasitic species. As S. mansoni is pathogenic for humans, this study represents a promising source of therapeutic targets, providing not only data on the parasite development in interaction with its vertebrate host, but also new insights on its reproductive function

Bacterial capsular polysaccharides with antibiofilm activity share common biophysical and electrokinetic properties

Abstract Bacterial biofilms are surface-attached communities that are difficult to eradicate due to a high tolerance to antimicrobial agents. The use of non-biocidal surface-active compounds to prevent the initial adhesion and aggregation of bacterial pathogens is a promising alternative to antibiotic treatments and several antibiofilm compounds have been identified, including some capsular polysaccharides released by various bacteria. However, the lack of chemical and mechanistic understanding of the activity of these high-molecular-weight polymers limits their use for control of biofilm formation. Here, we screened a collection of 32 purified capsular polysaccharides and identified seven new compounds with non-biocidal activity against biofilms formed by Escherichia coli and/or Staphylococcus aureus . We analyzed the polysaccharide mobility under applied electric field conditions and showed that active and inactive polysaccharide polymers display distinct electrokinetic properties and that all active macromolecules shared high intrinsic viscosity features. Based on these characteristics, we identified two additional antibiofilm capsular polysaccharides with high density of electrostatic charges and their permeability to fluid flow. Our study therefore provides insights into key biophysical properties discriminating active from inactive polysaccharides. This characterization of a specific electrokinetic signature for polysaccharides displaying antibiofilm activity opens new perspectives to identify or engineer non-biocidal surface-active macromolecules to control biofilm formation in medical and industrial settings. Significance statement Some bacteria produce non-biocidal capsular polysaccharides that reduce the adhesion of bacterial pathogens to surfaces. Due to a lack of molecular and structural definition, the basis of their antiadhesion activity is unknown, thus hindering their prophylactic use for biofilm control. Here, we identified nine new active compounds and compared their composition, structure and biophysical properties with other inactive capsular polysaccharides. Despite the absence of specific molecular motif, we demonstrate that all active polysaccharides share common electrokinetic properties that distinguish them from inactive polymers. This characterization of the biophysical properties of antibiofilm bacterial polysaccharide provides key insights to engineer non-biocidal and bio-inspired surface-active compounds to control bacterial adhesion in medical and industrial settings

<i>Sm</i>PoMuc expression of each group in C and IC strains.

<p>mRNA were extracted from miracidia pool from the IC (black bars) and C (dashed grey bars) strains and qPCR were performed with primers targeting <i>Sm</i>PoMuc group 1, group 2, group 3.1(r1–r2). Results represents the mean value of 3 biological repeats, * indicates a p-value below 0.05.</p