Les enjeux territoriaux associés à la réforme municipale au Québec. Le cas de Saguenay

Depuis une décennie, les réorganisations politico-administratives locales et régionales sont fréquentes en Occident. Le Québec n’échappe pas à la tendance avec la réforme municipale en cours. Les regroupements de municipalités de 2001 ont ainsi affecté les six régions métropolitaines de la province et plusieurs agglomérations de plus petite taille. Cet article a pour objectif de faire ressortir les enjeux territoriaux de l’intégration socio-économique et fonctionnelle de ces nouveaux espaces politiques. À cette fin, nous regarderons la situation de Saguenay au Québec. Cette ville moyenne en région périphérique se distingue à divers égards. Elle est une agglomération possédant plusieurs centres d’affaires ayant des caractéristiques propres. Ceux-ci correspondent aux secteurs centraux des anciennes villes de Chicoutimi, Jonquière et La Baie. Par ailleurs, Saguenay est le coeur d’un espace rural agro-forestier qui possède maintenant une autonomie administrative compte tenu de la création d’une nouvelle municipalité régionale de comté (MRC). Comment seront gérées les dynamiques intra-urbaines et régionales dans le contexte de cette réorganisation administrative?Local government reforms are popular in Western societies these days. The province of Québec (Canada) is not different in this regard. The 2001 municipal reform has resulted in major changes, namely the amalgamation of numerous towns and cities in and around six key metropolitan areas (Montréal, Québec City, Gatineau, Saguenay, Sherbrooke and Trois-Rivières). This article attempts to explore the land use planning and local democracy issues that face newly elected bodies. The case of Saguenay is used as an example of an average city based in a resource-economy region. Saguenay was created through the merger of Chicoutimi, Jonquière, La Baie and four other municipalities. The merger has been difficult to implement in a multi-centred urban region with strong local identities

The ribosomal protein RACK1 is required for microRNA function in both C. elegans and humans

Despite the importance of microRNAs (miRNAs) in gene regulation, it is unclear how the miRNA-Argonaute complex-or miRNA-induced silencing complex (miRISC)-can regulate the translation of their targets in such diverse ways. We demonstrate here a direct interaction between the miRISC and the ribosome by showing that a constituent of the eukaryotic 40S subunit, receptor for activated C-kinase (RACK1), is important for miRNA-mediated gene regulation in animals. In vivo studies demonstrate that RACK1 interacts with components of the miRISC in nematodes and mammals. In both systems, the alteration of RACK1 expression alters miRNA function and impairs the association of the miRNA complex with the translating ribosomes. Our data indicate that RACK1 can contribute to the recruitment of miRISC to the site of translation, and support a post-initiation mode of miRNA-mediated gene repression. © 2011 European Molecular Biology Organization

Human let-7a mirna blocks protein production on actively translating polyribosomes

MicroRNAs (miRNAs) regulate gene expression at a post-transcriptional level through base-pairing to 3¢ untranslated regions (UTRs) of messenger RNAs. The mechanism by which human let-7a miRNA regulates mRNA translation was examined in HeLa cells expressing reporter mRNAs containing the Caenorhabditis elegans lin-41 3¢ UTR. let-7a miRNA strongly repressed translation, yet the majority of control and lin-41-bearing RNAs sedimented with polyribosomes in sucrose gradients; these polyribosomes, together with let-7a miRNA and the miRISC protein AGO, were released from those structures by puromycin. RNA containing the lin-41 3¢ UTR and an iron response element in the 5¢ UTR sedimented with polysomes when cells were incubated with iron, but showed ribosome run-off when the iron was chelated. These data indicate that let-7a miRNA inhibits actively translating polyribosomes. Nascent polypeptide coimmunoprecipitation experiments further suggest that let-7a miRNA interferes with the accumulation of growing polypeptides. miRNAs are evolutionarily conserved noncoding RNAs B21 nucleotides (nt) in length that regulate gene expression at the posttranscriptional level by base-pairing to partially complementary sequences in 3¢ UTRs of target mRNAs 1 . miRNAs control several biological processes in worms, flies, zebrafish and mammals, including developmental timing, cell differentiation, cell proliferation, apoptosis and patterning of the nervous system 2,3 . In addition, the mutation or misexpression of miRNAs correlates with various human cancers, indicating that they might act as tumor suppressors or oncogenes 4 . let-7a miRNA regulates developmental timing in the nematode C. elegans and controls the expression of several transcription factors, including the 'RING, B-box, coiled-coil' (RBCC) protein LIN-41, which functions as a translational repressor of the transcription factor LIN-29 during the larval-to-adult transition In C. elegans, the lin-4 miRNA target mRNAs lin-14 and lin-28 sediment with polyribosomes, although little LIN-14 or LIN-28 protein has been detected, indicating that mRNA expression is inhibited after translation initiation 10,11 . This post-initiation repression is also suggested by the observation that miRNAs sediment with polyribosomes in mammalian cells and in worms These experiments suggest that miRNAs might function at multiple levels, which prompted us to examine the mechanism by which the C. elegans lin-41 3¢ UTR, containing two phylogenetically conserved let-7a miRNA sites RESULTS Human let-7a miRNA represses translation in HeLa cells To investigate the mechanism by which miRNAs repress mRNA translation in human cells, we transfected HeLa cells with plasmid

Association Mapping of Insecticide Resistance in Wild Anopheles gambiae Populations: Major Variants Identified in a Low-Linkage Disequilbrium Genome

Background: Association studies are a promising way to uncover the genetic basis of complex traits in wild populations. Data on population stratification, linkage disequilibrium and distribution of variant effect-sizes for different trait-types are required to predict study success but are lacking for most taxa. We quantified and investigated the impacts of these key variables in a large-scale association study of a strongly selected trait of medical importance: pyrethroid resistance in the African malaria vector Anopheles gambiae. Methodology/Principal Findings: We genotyped <1500 resistance-phenotyped wild mosquitoes from Ghana and Cameroon using a 1536-SNP array enriched for candidate insecticide resistance gene SNPs. Three factors greatly impacted study power. (1) Population stratification, which was attributable to co-occurrence of molecular forms (M and S), and cryptic within-form stratification necessitating both a partitioned analysis and genomic control. (2) All SNPs of substantial effect (odds ratio, OR.2) were rare (minor allele frequency, MAF,0.05). (3) Linkage disequilibrium (LD) was very low throughout most of the genome. Nevertheless, locally high LD, consistent with a recent selective sweep, and uniformly high ORs in each subsample facilitated significant direct and indirect detection of the known insecticide target site mutation kdr L1014F (OR<6; P,1026), but with resistance level modified by local haplotypic background. Conclusion: Primarily as a result of very low LD in wild A. Gambiae, LD-based association mapping is challenging, but is feasible at least for major effect variants, especially where LD is enhanced by selective sweeps. Such variants will be of greatest importance for predictive diagnostic screening

Structural and Mechanistic Analysis of Sialic Acid Synthase NeuB from Neisseria meningitidis in Complex with Mn2+, Phosphoenolpyruvate, and N-Acetylmannosaminitol *

In Neisseria meningitidis and related bacterial pathogens, sialic acids play critical roles in mammalian cell immunity evasion and are synthesized by a conserved enzymatic pathway that includes sialic acid synthase (NeuB, SiaC, or SynC). NeuB catalyzes the condensation of phosphoenolpyruvate (PEP) and N-acetylmannosamine, directly forming N-acetylneuraminic acid (or sialic acid). In this paper we report the development of a coupled assay to monitor NeuB reaction kinetics and an 18O-labeling study that demonstrates the synthase operates via a C-O bond cleavage mechanism. We also report the first structure of a sialic acid synthase, that of NeuB, revealing a unique domain-swapped homodimer architecture consisting of a (beta/alpha)8 barrel (TIM barrel)-type fold at the N-terminal end and a domain with high sequence identity and structural similarity to the ice binding type III antifreeze proteins at the C-terminal end of the enzyme. We have determined the structures of NeuB in the malate-bound form and with bound PEP and the substrate analog N-acetylmannosaminitol to 1.9 and 2.2 A resolution, respectively. Typical of other TIM barrel proteins, the active site of NeuB is located in a cavity at the C-terminal end of the barrel; however, the positioning of the swapped antifreeze-like domain from the adjacent monomer provides key residues for hydrogen bonding with substrates in the active site of NeuB, a structural feature that leads to distinct modes of substrate binding from other PEP-utilizing enzymes that lack an analogous antifreeze-like domain. Our observation of a direct interaction between a highly ordered manganese and the N-acetylmannosaminitol in the NeuB active site also suggests an essential role for the ion as an electrophilic catalyst that activates the N-acetylmannosamine carbonyl to the addition of PEP

Exploring the origin and degree of genetic isolation of Anopheles gambiae from the islands of São Tomé and Príncipe, potential sites for testing transgenic-based vector control

The evolutionary processes at play between island and mainland populations of the malaria mosquito vector Anopheles gambiae sensu stricto are of great interest as islands may be suitable sites for preliminary application of transgenic-based vector control strategies. São Tomé and Príncipe, located off the West African coast, have received such attention in recent years. This study investigates the degree of isolation of An. gambiae s.s. populations between these islands and the mainland based on mitochondrial and ribosomal DNA molecular data. We identify possible continental localities from which these island populations derived. For these purposes, we used FST values, haplotype networks, and nested clade analysis to estimate migration rates and patterns. Haplotypes from both markers are geographically widespread across the African continent. Results indicate that the populations from São Tomé and Príncipe are relatively isolated from continental African populations, suggesting they are promising sites for test releases of transgenic individuals. These island populations are possibly derived from two separate continental migrations. This result is discussed in the context of the history of the African slave trade with respect to São Tomé and Príncipe

Developmental characterization of the microRNA-specific C. elegans Argonautes alg-1 and alg-2.

The genes alg-1 and alg-2 (referred to as "alg-1/2") encode the Argonaute proteins affiliated to the microRNA (miRNA) pathway in C. elegans. Bound to miRNAs they form the effector complex that effects post-transcriptional gene silencing. In order to define biological features important to understand the mode of action of these Argonautes, we characterize aspects of these genes during development. We establish that alg-1/2 display an overlapping spatio-temporal expression profile and shared association to a miRNAs set, but with gene-specific predominant expression in various cells and increased relative association to defined miRNAs. Congruent with their spatio-temporal coincidence and regardless of alg-1/2 drastic post-embryonic differences, only loss of both genes leads to embryonic lethality. Embryos without zygotic alg-1/2 predominantly arrest during the morphogenetic process of elongation with defects in the epidermal-muscle attachment structures. Altogether our results highlight similarities and specificities of the alg-1/2 likely to be explained at different cellular and molecular levels

GW182-Free microRNA Silencing Complex Controls Post-transcriptional Gene Expression during Caenorhabditis elegans Embryogenesis

MicroRNAs and Argonaute form the microRNA induced silencing complex or miRISC that recruits GW182, causing mRNA degradation and/or translational repression. Despite the clear conservation and molecular significance, it is unknown if miRISC-GW182 interaction is essential for gene silencing during animal development. Using Caenorhabditis elegans to explore this question, we examined the relationship and effect on gene silencing between the GW182 orthologs, AIN-1 and AIN-2, and the microRNA-specific Argonaute, ALG-1. Homology modeling based on human Argonaute structures indicated that ALG-1 possesses conserved Tryptophan-binding Pockets required for GW182 binding. We show in vitro and in vivo that their mutations severely altered the association with AIN-1 and AIN-2. ALG-1 tryptophan-binding pockets mutant animals retained microRNA-binding and processing ability, but were deficient in reporter silencing activity. Interestingly, the ALG-1 tryptophan-binding pockets mutant phenocopied the loss of alg-1 in worms during larval stages, yet was sufficient to rescue embryonic lethality, indicating the dispensability of AINs association with the miRISC at this developmental stage. The dispensability of AINs in miRNA regulation is further demonstrated by the capacity of ALG-1 tryptophan-binding pockets mutant to regulate a target of the embryonic mir-35 microRNA family. Thus, our results demonstrate that the microRNA pathway can act independently of GW182 proteins during C. elegans embryogenesis

Trends in Insecticide Resistance in Natural Populations of Malaria Vectors in Burkina Faso, West Africa: 10 Years’ Surveys

International audienc

Distribution of knock-down resistance mutations in Anopheles gambiae molecular forms in west and west-central Africa

<p>Abstract</p> <p>Background</p> <p><it>Knock-down </it>resistance (<it>kdr</it>) to DDT and pyrethroids in the major Afrotropical vector species, <it>Anopheles gambiae </it>sensu stricto, is associated with two alternative point mutations at amino acid position 1014 of the voltage-gated sodium channel gene, resulting in either a leucine-phenylalanine (L1014F), or a leucine-serine (L1014S) substitution. In <it>An. gambiae </it>S-form populations, the former mutation appears to be widespread in west Africa and has been recently reported from Uganda, while the latter, originally recorded in Kenya, has been recently found in Gabon, Cameroon and Equatorial Guinea. In M-form populations surveyed to date, only the L1014F mutation has been found, although less widespread and at lower frequencies than in sympatric S-form populations.</p> <p>Methods</p> <p><it>Anopheles gambiae </it>M- and S-form specimens from 19 sites from 11 west and west-central African countries were identified to molecular form and genotyped at the <it>kdr </it>locus either by Hot Oligonucleotide Ligation Assay (HOLA) or allele-specific PCR (AS-PCR).</p> <p>Results</p> <p>The <it>kdr </it>genotype was determined for about 1,000 <it>An. gambiae </it>specimens. The L1014F allele was found at frequencies ranging from 6% to 100% in all S-form samples (N = 628), with the exception of two samples from Angola, where it was absent, and coexisted with the L1014S allele in samples from Cameroon, Gabon and north-western Angola. The L1014F allele was present in M-form samples (N = 354) from Benin, Nigeria, and Cameroon, where both M- and S-forms were sympatric.</p> <p>Conclusion</p> <p>The results represent the most comprehensive effort to analyse the overall distribution of the L1014F and L1014S mutations in <it>An. gambiae </it>molecular forms, and will serve as baseline data for resistance monitoring. The overall picture shows that the emergence and spread of <it>kdr </it>alleles in <it>An. gambiae </it>is a dynamic process and that there is marked intra- and inter-form heterogeneity in resistance allele frequencies. Further studies are needed to determine: i) the importance of selection pressure exerted by both agricultural and public health use of pyrethroid insecticides, ii) the phenotypic effects, particularly when the two mutations co-occur; and iii) the epidemiological importance of <it>kdr </it>for both pyrethroid- and DDT-based malaria control operations, particularly if/when the two insecticides are to be used in concert.</p