Mylène Weill

• Research Director at French National Centre for Scientific Research

Background Histological alterations such as nuclear abnormalities are sensitive biomarkers associated with diseases, tissue injury and environmental insults. While visual inspection and human interpretation of histology images are useful for initial characterization, such low-throughput procedures suffer from inherent limitations in terms of reliab...

Understanding how life is adapting to urban environments represents an important challenge in evolutionary biology. Here we investigate a widely cited example of urban adaptation, Culex pipiens form molestus, also known as the London Underground Mosquito. Population genomic analysis of ~350 contemporary and historical samples counter the popular hy...

Wolbachia are endosymbiotic bacteria inducing various reproductive manipulations of which cytoplasmic incompatibility (CI) is the most common. CI leads to reduced embryo viability in crosses between males carrying Wolbachia and uninfected females or those carrying an incompatible symbiont strain. In the mosquito Culex pipiens, the Wolbachia wPip ca...

We report the complete CDS of five viruses: an iflavirus, a protoambidensovirus and three microviruses),which were detected by viromics surveillance of mosquitoes (Aedes albopictus and Culex quinquefasciatus) from the Réunion Island. We detected the protoambidensovirus, which belongs to a clade previously reported only in C. pipiens, in A. albopict...

Background Mosquitoes of the Culex pipiens complex are widely distributed vectors for several arboviruses affecting humans. Consequently, their populations have long been controlled using insecticides, in response to which different resistance mechanisms have been selected. Moreover, their ecological preferences and broad adaptability allow C. pipi...

Mosquitoes of the Culex pipiens complex are worldwide vectors of arbovirus, filarial nematodes, and avian malaria agents. In these hosts, the endosymbiotic bacteria Wolbachia induce cytoplasmic incompatibility (CI), i.e., reduced embryo viability in so-called incompatible crosses. Wolbachia infecting Culex pipiens (wPip) cause CI patterns of unpara...

Anopheles gambiae s.l . has been the target of intense insecticide treatment since the mid-20th century to try and control malaria. A substitution in the ace-1 locus has been rapidly selected for, allowing resistance to organophosphate and carbamate insecticides. Since then, two types of duplication of the ace-1 locus have been found in An. gambiae...

This protocol describes approaches to qualify Wolbachia-induced cytoplasmic incompatibility (CI) patterns (compatible, uni or bidirectional) in crosses between two or more Culex pipiens isofemale lines, hosting different Wolbachia (wPip) strains. Here, we describe how to (1) collect the larvae in the field and grow them to the adult stage in the in...

Anopheles gambiae s.l. has been the target of intense insecticide treatment since the mid-XX th century to try and control malaria. A substitution in the ace-1 locus has been rapidly selected for, allowing resistance to organophosphate and carbamate insecticides. Since then, two types of duplication of the ace-1 locus have been found in An. gambiae...

The importance of gene amplifications in evolution is more and more recognized. Yet, tools to study multi-copy gene families are still scarce, and many such families are overlooked using common sequencing methods. Haplotype reconstruction is even harder for polymorphic multi-copy gene families. Here, we show that all variants (or haplotypes) of a m...

The mosquitoes of the Culex pipiens complex are worldwide vectors of arboviruses, filarial nematodes and avian malaria agents. In these hosts, the endosymbiotic bacteria Wolbachia induce cytoplasmic incompatibility (CI), a reduced embryo viability in so-called incompatible crosses. The Wolbachia infecting Culex (wPip) cause CI patterns of an unpara...

A. gambiae s.l. has been the target of intense insecticide treatment since the mid-XXth century to try and control malaria, and a substitution in the ace-1 locus allowing resistance to organophosphate and carbamates insecticides has been rapidly selected for. Since then, several duplications of the ace-1 locus have been found in A. gambiae s.l. pop...

Wolbachia are common bacteria among terrestrial arthropods. These endosymbionts transmitted through the female germline manipulate their host reproduction through several mechanisms whose most prevalent form called Cytoplasmic Incompatibility -CI- is a conditional sterility syndrome eventually favoring the infected progeny. Upon fertilization, the...

Organophosphate and carbamate insecticides have largely been used worldwide to control mosquito populations. As a response, the same amino acid substitution in the ace-1 gene (G119S), conferring resistance to both insecticides, has been selected independently in many mosquito species. In Anopheles gambiae , it has recently been shown that the G119S...

This study developed a new bioinformatics pipeline to acquire all the different copies of multi-copy gene families based on Oxford Nanopore Technologies sequencing of PCR products. We used this pipeline to acquire the sequences of highly similar copies of the cidA and cidB genes present in the genomes of Wolbachia pipientis (wPip) bacteria infectin...

Background Mosquitoes of the Culex pipiens complex are found across the globe and are the focus of many research studies. Among the temperate species C. pipiens sensu stricto (s.s.), two forms are usually described: molestus and pipiens . These two forms are indistinguishable in terms of morphology but show behavioral and physiological differences...

The control of mosquito populations using insecticides is increasingly threatened by the spread of resistance mechanisms. Dieldrin resistance, conferred by point mutations in the Rdl gene encoding the γ-aminobutyric acid receptor, has been reported at high prevalence in mosquito populations in response to selective pressures. In this study, we moni...

Microbial communities are known to influence mosquito lifestyles by modifying essential metabolic and behavioral processes that affect reproduction, development, immunity, digestion, egg survival, and the ability to transmit pathogens. Many studies have used 16S rRNA gene amplicons to characterize mosquito microbiota and investigate factors that in...

Wolbachia endosymbionts commonly induce cytoplasmic incompatibility, making infected males’ sperm lethal to the embryos unless these are rescued by the same bacterium, inherited from their mother. Causal genes were recently identified but two families of mechanistic models are still opposed. In the toxin-antidote model, interaction between the toxi...

Microbial communities are known to influence mosquito lifestyles by modifying essential metabolic and behavioral processes that affect reproduction, development, immunity, digestion, egg survival, and ability to transmit pathogens. Many studies have used 16S rRNA gene amplicons to characterize mosquito microbiota and investigate factors that influe...

Wolbachia endosymbionts commonly induce cytoplasmic incompatibility, making infected males’ sperm lethal to the embryos unless these are rescued by the same bacterium, inherited from their mother. Causal genes were recently identified but two families of mechanistic models are still opposed. In the toxin-antidote model, interaction between the toxi...

In arthropods, Wolbachia endosymbionts induce conditional sterility, called cytoplasmic incompatibility (CI), resulting from embryonic lethality. CI penetrance (i.e., embryonic death rate) varies depending on host species and Wolbachia strains involved. All Culex pipiens mosquitoes are infected by the endosymbiotic alphaproteobacteria Wolbachia wPi...

BACKGROUND Mosquitoes of the Culex pipiens complex are the vectors of several arboviruses and are thus subjected to insecticide control worldwide. However, overuse of insecticides selects for resistance. While assessing the resistance status of the vectors is required for effective and sustainable disease control, resistance has so far only been sp...

The inadequacy of standard mosquito control strategies calls for ecologically safe novel approaches, for example the use of biological agents such as the endosymbiotic α‐proteobacteria Wolbachia or insect‐specific viruses (ISVs). Understanding the ecological interactions between these “biocontrol endosymbionts” is thus a fundamental step. Wolbachia...

Background Diflubenzuron (DFB) is one of the most used insecticides in mosquito larval control including that of Culex pipiens, the proven vector of the recent West Nile Virus epidemics in Europe. Two mutations (I1043L and I1043M) in the chitin synthase (CHS) putative binding site of DFB have been previously reported in Cx. pipiens from Italy and a...

Background: Insecticide resistance is a growing concern for malaria control and vector control effectiveness relies on assessing it distribution and understanding its evolution. Methods: We assessed resistance levels and the frequencies of two major target‑site mutations, L1014F‑VGSC and G119S‑ace-1, conferring resistance to pyrethroids (PYRs) and...

Although the diversity of bacterial endosymbionts in arthropods is well documented, whether and how such diversity is maintained remains an open question. We investigated the temporal changes occurring in the prevalence and composition of endosymbionts after transferring natural populations of Tetranychus spider mites from the field to the laborato...

Viruses of the Parvoviridae family infect a wide range of animals including vertebrates and invertebrates. So far, our understanding of parvovirus diversity is biased towards medically or economically important viruses mainly infecting vertebrate hosts, while invertebrate infecting parvoviruses-namely densoviruses-have been largely neglected. Here,...

Endosymbiotic Wolbachia bacteria are, to date, considered the most widespread symbionts in arthropods and are the cornerstone of major biological control strategies. Such a high prevalence is based on the ability of Wolbachia to manipulate their hosts' reproduction. One manipulation called cytoplasmic incompatibility (CI) is based on the death of t...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Wolbachia is a genus of obligate intracellular bacteria found in nematodes and arthropods worldwide, including insect vectors that transmit dengue, West Nile, and Zika viruses. Wolbachia's unique ability to alter host reproductive behavior through its temperate bacteriophage WO has enabled the development of new vector control strategies. However,...

Wolbachia bacteria inhabit the cells of about half of all arthropod species, an unparalleled success stemming in large part from selfish invasive strategies. Cytoplasmic incompatibility (CI), whereby the symbiont makes itself essential to embryo viability, is the most common of these and constitutes a promising weapon against vector-borne diseases....

To protect humans and domestic animals from mosquito borne diseases, alternative methods to chemical insecticides have to be found. Pilot studies using the vertically transmitted bacterial endosymbiont Wolbachia were already launched in different parts of the world. Wolbachia can be used either in Incompatible Insect Technique (IIT), to decrease mo...

Les enzymes accélèrent les réactions chimiques en dimi­ nuant, par stabilisation de l'état de transition du substrat, la barrière énergétique d'une réaction chimique. Un anti­ corps développé contre cet état de transition a un pou­ voir catalytique. De nombreuses autres stratégies ont été développées pour obtenir des anticorps doués de proprié­ tés...

Insecticide resistance is a major threat for vector control and prevention of mosquito borne diseases. In the Culex pipiens mosquitoes, resistance against diflubenzuron (DFB) was firstly detected in Ravenna (Emilia-Romagna region, Northern Italy), in 2015. The resistant phenotypes were associated with two mutations, I1043 M and I1043 L, at the amin...

Insecticide resistance has been reported to impact the interactions between mosquitoes and the pathogens they transmit. However, the effect on vector competence for arboviruses still remained to be investigated. We examined the influence of two insecticide resistance mechanisms on vector competence of the mosquito Culex quinquefasciatus for two arb...

The original version of this Article contained an error in Fig. 1a, in which the sequences of the reverse and forward primers were swapped

Culex pipiens densovirus (CpDV), a single stranded DNA virus, has been isolated from Culex pipiens mosquitoes but differs from other mosquito densoviruses in terms of genome structure and sequence identity. Its transmission from host to host, the nature of its interactions with both its host and host's endosymbiotic bacteria Wolbachia are not known...

Culex pipiens densovirus (CpDV), a single stranded DNA virus, has been isolated from Culex pipiens mosquitoes but differs from other mosquito densoviruses in terms of genome structure and sequence identity. Its transmission from host to host, the nature of its interactions with both its host and host′s endosymbiotic bacteria Wolbachia are not known...

Background Until very recently, Anopheles were considered naturally unable to host Wolbachia, an intracellular bacterium regarded as a potential biological control tool. Their detection in field populations of Anopheles gambiae sensu lato, suggests that they may also be present in many more anopheline species than previously thought. Results Here,...

West Nile Virus (WNV) is a flavivirus involved in many human infections worldwide. This arthropod-borne virus is directly co-inoculated with mosquito saliva through the epidermis and the dermis during blood meal. WNV starts replicating in the skin before migrating to the draining lymph node, leading to widespread viremia and in some cases to neurol...

Wolbachia are maternally inherited endosymbiotic bacteria, widespread among arthropods thanks to host reproductive manipulations that increase their prevalence into host populations. The most commonly observed manipulation is cytoplasmic incompatibility (CI). CI leads to embryonic death in crosses between i) infected males and uninfected females an...

Presentation of the ten C. pipiens lines used in this study. (DOCX)

The different crosses from which the CI cellular phenotype in C. pipiens was studied. Three different types of crosses were performed to study the cellular phenotype responsible for embryonic death in sterile crosses: i) sterile crosses between males and females infected with different Wolbachia strains, ii) sterile crosses between infected males a...

mod and resc profiles of the lines used in crosses experiments. mod profiles were determined by crossing males from the four Mal lines with the females of the 4 ref-cytotypes lines Atyame et al. (2014). resc profiles were determine by crossing females of the five Fem lines with males of the 4 ref-cytotypes lines. Mal lines harbored wPip strains wit...

cidA copy number in the wPip strains infecting the four Mal lines. cidA copy number was measured by quantitative PCR as the ratio between the number of copies of the Wolbachia cidA gene and the Wolbachia wsp gene. The colored dots represent the cidA copy number per wPip genome in a male and the red strips represent the average cidA copy number per...

Wolbachia cidA and cidB expression of the four Mal lines estimated with Real Time Quantitative PCR. (CSV)

Proportion of unhatched developed embryos from CI crosses involving either infected or uninfected (TC) females. Proportion of unhatched developed embryos are given as the mean proportion measured on fifty eggs for 10 rafts per cross (500 eggs observed per cross) ± standard deviation. No unhatched developed embryos were found in any of the seven dif...

Accession numbers. Accession numbers for cidA cidB variants analyzed in S2 and S3 Figs. (DOCX)

Unhatched developed embryos are haploid. Restriction profile of kdr PCR products by RsaI enzyme from single mosquito extracted DNA. M: molecular weight marker. 1 wPipIII-Slab line; 2/3: wPipIV-Ichkeul 13 line; 4/5: eggs-raft containing non-viable developed embryos from a CI cross between ♂ Slab x ♀ Ichkeul 13 (embryos display only maternal markers)...

Repertoires of CidA protein variants in the four Mal line wPip strains. Protein sequences alignment of the CidA variants found in the four Wolbachia strains wPipI-Tunis, wPipI-Utique, wPipII-Lavar and wPipIII-Slab (Mal lines). The first sequence is used as a reference to determine the polymorphic region. For more clarity, only polymorphic positions...

cidB expression level in the wPip strains infecting the four Mal lines. cidB expression was measured by quantitative PCR as the ratio between the Wolbachia cidB gene expression and the Wolbachia wsp gene expression. The colored dots represent the cidB expression level per wPip genome in a male and the red strips represent the average cidB expressio...

cidA/cidB expression level in the wPip strains infecting the four Mal lines. cidA/cidB expression levels was measured by quantitative PCR as the ratio between the number of copies of the Wolbachia cidA gene and the Wolbachia cidB gene. The colored dots represent the cidA/cidB expression level per wPip genome in a male and the red strips represent t...

Wolbachia testes density of the four Mal lines estimated with Real Time Quantitative PCR. (CSV)

Wolbachia cidA and cidB copy number of the four Mal lines estimated with Real Time Quantitative PCR. (CSV)

Explanation of the nomenclature used in this paper. (DOCX)

cidA/cidB copy number in the wPip strains infecting the four Mal lines. cidA/cidB copy number was measured by quantitative PCR as the ratio between the number of copies of the Wolbachia cidA gene and the Wolbachia cidB gene. The colored dots represent the cidA/cidB copy number per wPip genome in a male and the red strips represent the average cidA/...

cidA expression level in the wPip strains infecting the four Mal lines. cidA expression was measured by quantitative PCR as the ratio between the Wolbachia cidA gene expression and the Wolbachia wsp gene expression. The colored dots represent the cidA expression level per wPip genome in a male and the red strips represent the average cidA expressio...

Proportion of unhatched developed haploid embryos of performed CI crosses. (CSV)

The repertoire of CidB protein variants in the four Mal line wPip strains. Protein sequences alignment of the CidB variants found in the four Wolbachia strains wPipI-Tunis, wPipI-Utique, wPipII-Lavar and wPipIII-Slab (Mal lines). The first sequence is used as a reference to determine the polymorphic region. For more clarity, only polymorphic positi...

Correlation between cidB variants diversity in wPip genomes and CI cellular intensity. Lighter gray bar plot accounts for the 10 crosses involving males from Lavar and Utique lines hosting wPip, which harbor 2 different variants of cidB in their genomes, while darker gray bar plot accounts for the 10 crosses involving males from Tunis and Slab line...

cidB copy number in the wPip strains infecting the four Mal lines. cidB copy number was measured by quantitative PCR as the ratio between the number of copies of the Wolbachia cidB gene and the Wolbachia wsp gene. The colored dots represent the cidB copy number per wPip genome in a male and the red strips represent the average cidB copy number per...

In the originally published HTML and PDF versions of this Article, gel images in Figures 7c and 8c were not prepared as per the Nature journal policy. These figure panels have now been corrected in both the PDF and HTML versions of the Article. In Fig. 7c, the lane labelled ‘Ha’ was inappropriately duplicated to represent the lane labelled ‘Ich13’....

Background Wolbachia are maternally transmitted bacteria that can manipulate their hosts’ reproduction causing cytoplasmic incompatibility (CI). CI is a sperm-egg incompatibility resulting in embryonic death. Due to this sterilising effect on mosquitoes, Wolbachia are considered for vector control strategies. Important vectors for arboviruses, fila...

While gene copy-number variations play major roles in long-term evolution, their early dynamics remains largely unknown. However examples of their role in short-term adaptation are accumulating: identical repetitions of a locus (homogeneous duplications) can provide a quantitative advantage, while the association of differing alleles (heterogeneous...

Spider mites of the genus Tetranychidae are severe crop pests. In the Mediterranean a few species coexist, but they are difficult to identify based on morphological characters. Additionally, spider mites often harbour several species of endosymbiotic bacteria, which may affect the biology of their hosts. Here, we propose novel, cost-effective, mult...

Bacterial endosymbionts are known as important players of the evolutionary ecology of their hosts. However, their distribution, prevalence and diversity are still largely unexplored. To this aim, we investigated infections by the most common bacterial reproductive manipulators in herbivorous spider mites of South-Western Europe. Across 16 populatio...

Culex pipiens mosquitoes are infected with Wolbachia (wPip) that cause an important diversity of cytoplasmic incompatibilities (CIs). Functional transgenic studies have implicated the cidA-cidB operon from wPip and its homolog in wMel in CI between infected Drosophila males and uninfected females. However, the genetic basis of the CI diversity indu...

In the global context of arboviral emergence, deep sequencing unlocks the discovery of new mosquito-borne viruses. Mosquitoes of the species Culex pipiens, C. torrentium, and C. hortensis were sampled from 22 locations worldwide for tran-scriptomic analyses. A virus discovery pipeline was used to analyze the dataset of 0.7 billion reads comprising...

Control of infectious diseases is a major challenge of the century. Arthropod vectors are proliferating, leading to increasing prevalence of deadly diseases (e.g., malaria, dengue, and yellow fever). In several countries, particularly the poorest ones, vector control using insecticides is the only affordable way to fight these diseases. Unfortunate...

Gene duplications occur at a high rate. Although most appear detrimental, some homogeneous duplications (identical gene copies) can be selected for beneficial increase in produced proteins. Heterogeneous duplications, which combine divergent alleles of a single locus, are seldom studied due to the paucity of empirical data. We investigated their ro...

Gene duplications are widespread in genomes, but their role in contemporary adaptation is not fully understood. Although mostly deleterious, homogeneous duplications that associate identical repeats of a locus often increase the quantity of protein produced, which can be selected in certain environments. However, another type exists: heterogeneous...

Background Aedes albopictus is one of the most invasive human disease vectors. Its control has been largely based on insecticides, such as the larvicide temephos. Temephos resistance has been associated with the up-regulation, through gene amplification, of two carboxylesterase (CCE) genes closely linked on the genome, capable of sequestering and m...

Primers used for quantitative real time PCR. (XLSX)

All variable sites in the amplified part of CCEae3a esterase. (XLSX)

Country-location, number of Aedes albopictus individuals used in the study and haplotypes identified. (DOCX)

qPCR results for gene copy number variation of CCEs in all tested individuals. (XLSX)