A Novel Function for Fragile X Mental Retardation Protein in Translational Activation

Fragile X syndrome, the most frequent form of inherited mental retardation, is due to the absence of Fragile X Mental Retardation Protein (FMRP), an RNA-binding protein involved in several steps of RNA metabolism. To date, two RNA motifs have been found to mediate FMRP/RNA interaction, the G-quartet and the “kissing complex,” which both induce translational repression in the presence of FMRP. We show here a new role for FMRP as a positive modulator of translation. FMRP specifically binds Superoxide Dismutase 1 (Sod1) mRNA with high affinity through a novel RNA motif, SoSLIP (Sod1 mRNA Stem Loops Interacting with FMRP), which is folded as three independent stem-loop structures. FMRP induces a structural modification of the SoSLIP motif upon its interaction with it. SoSLIP also behaves as a translational activator whose action is potentiated by the interaction with FMRP. The absence of FMRP results in decreased expression of Sod1. Because it has been observed that brain metabolism of FMR1 null mice is more sensitive to oxidative stress, we propose that the deregulation of Sod1 expression may be at the basis of several traits of the physiopathology of the Fragile X syndrome, such as anxiety, sleep troubles, and autism

Highly plastic genome of Microcystis aeruginosa PCC 7806, a ubiquitous toxic freshwater cyanobacterium

Background The colonial cyanobacterium Microcystis proliferates in a wide range of freshwater ecosystems and is exposed to changing environmental factors during its life cycle. Microcystis blooms are often toxic, potentially fatal to animals and humans, and may cause environmental problems. There has been little investigation of the genomics of these cyanobacteria. Results Deciphering the 5,172,804 bp sequence of Microcystis aeruginosa PCC 7806 has revealed the high plasticity of its genome: 11.7% DNA repeats containing more than 1,000 bases, 6.8% putative transposases and 21 putative restriction enzymes. Compared to the genomes of other cyanobacterial lineages, strain PCC 7806 contains a large number of atypical genes that may have been acquired by lateral transfers. Metabolic pathways, such as fermentation and a methionine salvage pathway, have been identified, Conclusion Microcystis aeruginosa PCC 7806 appears to have adopted an evolutionary strategy relying on unusual genome plasticity to adapt to eutrophic freshwater ecosystems, a property shared by another strain of M. aeruginosa (NIES-843). Comparisons of the genomes of PCC 7806 and other cyanobacterial strains indicate that a similar strategy may have also been used by the marine strain Crocosphaera watsonii WH8501 to adapt to other ecological niches, such as oligotrophic open oceans.

The G-quartet containing FMRP binding site in FMR1 mRNA is a potent exonic splicing enhancer

The fragile X mental retardation protein (FMRP) is a RNA-binding protein proposed to post-transcriptionally regulate the expression of genes important for neuronal development and synaptic plasticity. We previously demonstrated that FMRP binds to its own FMR1 mRNA via a guanine-quartet (G-quartet) RNA motif. However, the functional effect of this binding on FMR1 expression was not established. In this work, we characterized the FMRP binding site (FBS) within the FMR1 mRNA by a site directed mutagenesis approach and we investigated its importance for FMR1 expression. We show that the FBS in the FMR1 mRNA adopts two alternative G-quartet structures to which FMRP can equally bind. While FMRP binding to mRNAs is generally proposed to induce translational regulation, we found that mutations in the FMR1 mRNA suppressing binding to FMRP do not affect its translation in cellular models. We show instead that the FBS is a potent exonic splicing enhancer in a minigene system. Furthermore, FMR1 alternative splicing is affected by the intracellular level of FMRP. These data suggest that the G-quartet motif present in the FMR1 mRNA can act as a control element of its alternative splicing in a negative autoregulatory loop

Molecular mechanisms of cell death: recommendations of the Nomenclature Committee on Cell Death 2018.

Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field

Molecular bases of Fragile X syndrome,from identification of some FMRP interacting proteins to the establishment of a connexion with Rac1 signalling pathway

Le syndrome de l'X fragile résulte de l'absence de la protéine FMRP. Afin de préciser le rôle de FMRP, un criblage double hybride a été entrepris au sein du laboratoire. Ce criblage a permis d'identifier une protéine de fonction inconnue, 82-FIP. Nous avons montré que 82-FIP fait partie de complexes ribonucléoprotéiques associés aux polyribosomes et que, contrairement à FMRP, sa localisation subcellulaire change au cours du cycle cellulaire. Ces données permettent de penser que l'interaction entre FMRP et 82-FIP soit transitoire. L'étude de CYFIP1, également identifiée par criblage double hybride, avait permis d'établir un lien entre FMRP et la Rho GTPase Rac1 chez la drosophile. Nous avons confirmé l'existence d'une connexion entre FMRP et Rac1 dans des fibroblastes murins. Nous proposons un modèle dans lequel FMRP module la voie de signalisation Rac1 en inhibant la traduction d'une phosphatase, la PP2A, impliquée dans la déphosphorylation d'un effecteur de la voie Rac1, la Cofiline.Fragile X syndrome results from the absence of a protein called FMRP. In order to precise FMRP function, a yeast two-hybrid screening has been carried out in our laboratory. This screening has allowed the identification of 82-FIP, a protein of unknown function. We have shown that 82-FIP is part of ribonucleoproteic complex associated to polyribosomes. Contrary to FMRP, 82-FIP subcellular localization changes through cell cycle. Thus, we propose that interaction between FMRP and 82-FIP could be transient. Characterization of CYFIP1, another protein identified in the yeast two-hybrid screening, had led to the establishment of a link between FMRP and the Rho GTPase Rac1 in Drosophila. We have shown that such a connexion is conserved in murine fibroblasts. We propose that FMRP could interfere with Rac1 signalling pathway by inhibiting the translation of PP2A, a phosphatase involved in dephosphorylation of Cofilin, a Rac1 effector that enhances actin depolymerization

Molecular bases of Fragile X syndrome,from identification of some FMRP interacting proteins to the establishment of a connexion with Rac1 signalling pathway

Le syndrome de l'X fragile résulte de l'absence de la protéine FMRP. Afin de préciser le rôle de FMRP, un criblage double hybride a été entrepris au sein du laboratoire. Ce criblage a permis d'identifier une protéine de fonction inconnue, 82-FIP. Nous avoFragile X syndrome results from the absence of a protein called FMRP. In order to precise FMRP function, a yeast two-hybrid screening has been carried out in our laboratory. This screening has allowed the identification of 82-FIP, a protein of unknown fu

Bases moléculaires du syndrome de l’X Fragile : de l’identification d’interacteurs de FMRP à l’établissement d’une connexion avec la voie de signalisation Rac1

Le syndrome de l’X fragile résulte de l’absence de la protéine FMRP. Afin de préciser le rôle de FMRP, un criblage double hybride a été entrepris au sein du laboratoire. Ce criblage a permis d’identifier une protéine de fonction inconnue, 82-FIP. Nous avons montré que 82-FIP fait partie de complexes ribonucléoprotéiques associés aux polyribosomes et que, contrairement à FMRP, sa localisation subcellulaire change au cours du cycle cellulaire. Ces données permettent de penser que l’interaction entre FMRP et 82-FIP soit transitoire. L’étude de CYFIP1, également identifiée par criblage double hybride, avait permis d’établir un lien entre FMRP et la Rho GTPase Rac1 chez la drosophile. Nous avons confirmé l’existence d’une connexion entre FMRP et Rac1 dans des fibroblastes murins. Nous proposons un modèle dans lequel FMRP module la voie de signalisation Rac1 en inhibant la traduction d’une phosphatase, la PP2A, impliquée dans la déphosphorylation d’un effecteur de la voie Rac1, la Cofiline.Fragile X syndrome results from the absence of a protein called FMRP. In order to precise FMRP function, a yeast two-hybrid screening has been carried out in our laboratory. This screening has allowed the identification of 82-FIP, a protein of unknown function. We have shown that 82-FIP is part of ribonucleoproteic complex associated to polyribosomes. Contrary to FMRP, 82-FIP subcellular localization changes through cell cycle. Thus, we propose that interaction between FMRP and 82-FIP could be transient. Characterization of CYFIP1, another protein identified in the yeast two-hybrid screening, had led to the establishment of a link between FMRP and the Rho GTPase Rac1 in Drosophila. We have shown that such a connexion is conserved in murine fibroblasts. We propose that FMRP could interfere with Rac1 signalling pathway by inhibiting the translation of PP2A, a phosphatase involved in dephosphorylation of Cofilin, a Rac1 effector that enhances actin depolymerization

Reproductive function and control of the quality of Eurasian perch, Perca fluviatilis

L’amélioration des performances de reproduction des poissons d’élevage nécessite de déterminer les facteurs intrinsèques et extrinsèques influençant la qualité des gamètes d’une part, et de définir des paramètres fiables permettant de prédire les performances de reproduction d’autre part. Notre objectif est donc de comprendre le déterminisme multifactoriel de la reproduction chez la perche commune, Perca fluviatilis. Quatre facteurs nutritionnels (type d’aliment et taux de rationnement distribués lors des phases d’induction et de vernalisation) et 3 facteurs populationnels (poids initial, origine géographique, niveau de domestication) ont été testés. Une différence de réponse entre les sexes a été observée. Le type d’aliment distribué en vernalisation et le poids initial ont modifié l’état général des femelles. Les mâles ont plutôt été sensibles aux taux de rationnement et à l’origine géographique. L’étude des performances de reproduction a montré que le taux de ponte était sous l’influence de l’interaction entre le type d’aliment distribué en induction et en vernalisation, tandis que l’origine géographique a modulé la date de ponte. La régulation des performances de reproduction est donc un mécanisme complexe sous l’influence simultanée de plusieurs facteurs. La seconde partie de ce travail concerne la recherche de marqueurs prédictifs de la qualité des ovules. Nous avons d’abord montré que peu de paramètres morpho-anatomiques des pontes ou ovules sont des prédicateurs fiables. Cependant, l’analyse protéomique a permis de mettre en évidence plusieurs protéines exprimées différemment selon la qualité des pontes, pouvant jouer le rôle de biomarqueurs de qualité des ovulesImproving fish reproduction in breeding conditions implies to understand intrinsic and extrinsic factors influencing gametes quality on the one hand and to define relevant parameters allowing the prediction of fish reproductive performance on the other hand. Our goal was thus to understand the multifactorial determinism of the common perch (Perca fluviatilis) reproduction. Four nutritional factors (type of food and rate of rationing used either during the induction or vernalization phases) and 3 populational factors (initial weight, geographic origin and domestication level of breeders) have been tested. Data show different responses between females and males. type of food during wintering phase and initial broodstock weigh modified female condition. Males have been sensitive to rationing during wintering phase as well as geographical origin. Data show also that spawning rate was under the influence of interaction between kind of food during wintering phase and induction whereas geographical origin modulated the spawning date. The regulation of the performance reproduction is also a complex mechanism influenced by several factors. The second part of this work consisted on the research of parameters potentially predictive of ova quality. Firstly, our work shows that morphometric parameters measured before the fertilization are poorly relevant to predict reproductive performance. However, the proteomic analysis of several spawn allowed us to highlight proteins differently expressed according to the spawn quality, such proteins could be ova quality biomarker

Fonction de reproduction et régulation de la qualité chez la perche commune, Perca fluviatilis

Improving fish reproduction in breeding conditions implies to understand intrinsic and extrinsic factors influencing gametes quality on the one hand and to define relevant parameters allowing the prediction of fish reproductive performance on the other hand. Our goal was thus to understand the multifactorial determinism of the common perch (Perca fluviatilis) reproduction. Four nutritional factors (type of food and rate of rationing used either during the induction or vernalization phases) and 3 populational factors (initial weight, geographic origin and domestication level of breeders) have been tested. Data show different responses between females and males. type of food during wintering phase and initial broodstock weigh modified female condition. Males have been sensitive to rationing during wintering phase as well as geographical origin. Data show also that spawning rate was under the influence of interaction between kind of food during wintering phase and induction whereas geographical origin modulated the spawning date. The regulation of the performance reproduction is also a complex mechanism influenced by several factors. The second part of this work consisted on the research of parameters potentially predictive of ova quality. Firstly, our work shows that morphometric parameters measured before the fertilization are poorly relevant to predict reproductive performance. However, the proteomic analysis of several spawn allowed us to highlight proteins differently expressed according to the spawn quality, such proteins could be ova quality biomarkers.L'amélioration des performances de reproduction des poissons d'élevage nécessite de déterminer les facteurs intrinsèques et extrinsèques influençant la qualité des gamètes d'une part, et de définir des paramètres fiables permettant de prédire les performances de reproduction d'autre part. Notre objectif est donc de comprendre le déterminisme multifactoriel de la reproduction chez la perche commune, Perca fluviatilis. Quatre facteurs nutritionnels (type d'aliment et taux de rationnement distribués lors des phases d'induction et de vernalisation) et 3 facteurs populationnels (poids initial, origine géographique, niveau de domestication) ont été testés. Une différence de réponse entre les sexes a été observée. Le type d'aliment distribué en vernalisation et le poids initial ont modifié l'état général des femelles. Les mâles ont plutôt été sensibles aux taux de rationnement et à l'origine géographique. L'étude des performances de reproduction a montré que le taux de ponte était sous l'influence de l'interaction entre le type d'aliment distribué en induction et en vernalisation, tandis que l'origine géographique a modulé la date de ponte. La régulation des performances de reproduction est donc un mécanisme complexe sous l'influence simultanée de plusieurs facteurs. La seconde partie de ce travail concerne la recherche de marqueurs prédictifs de la qualité des ovules. Nous avons d'abord montré que peu de paramètres morpho-anatomiques des pontes ou ovules sont des prédicateurs fiables. Cependant, l'analyse protéomique a permis de mettre en évidence plusieurs protéines exprimées différemment selon la qualité des pontes, pouvant jouer le rôle de biomarqueurs de qualité des ovules