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Two patients with Ph-positive chronic myelocytic leukemia in erythroblastic transformation and rearrangement of the short arm of chromosome 18 are reported. Fluorescence in situ hybridization studies showed that the 18p rearrangement resulted from translocation of the main part of chromosome 22 long arm to 18p, including BCR-ABL1 fusion. The 18p abnormality resulted, thus, in loss of 18p and duplication of BCR-ABL1 in both patients. The possible relation to the erythroblastic type of blastic phase is briefly discussed. In addition an apparently intact germline ABL1 gene was duplicated and inserted into chromosome 6 at band p21 in one of these patients.

The safety of space flight is challenged by a severe loss of skeletal muscle mass, strength and endurance that may compromise the health and performance of astronauts. The molecular mechanisms underpinning muscle atrophy and decreased performance have been studied mostly after short duration flights, and are still not ful ly elucidated. By deciphering the muscle proteome changes elicited in mice after a full month aboard the BION-M1 biosatellite, we observed that the antigravity soleus incurred the greatest changes compared to locomotor muscles. Proteomics data notably suggested mitochondrial dysfunction, metabolic and fiber type switching toward glycolytic type II fibers, structural alterations, and calcium signaling-related defects to be the main causes for decreased muscle performance in flown mice. Alterations of the protein balance, mTOR pathway, myogenesis and apoptosis were expected to contribute to muscle atrophy. Moreover, several signs reflecting alteration of telomere maintenance, oxidative stress and insulin resistance were found as possible additional deleterious effects. Finally, eight days of recovery post flight were not sufficient to restore completely flight-induced changes. Thus, in-depth proteomics analysis unraveled the complex and multifactorial remodeling of skeletal muscle structure and function during long-term space flight, which should help defining combined sets of countermeasures before, during and after the flight.

Without effective countermeasures, the musculoskeletal system is altered by the microgravity environment of long-duration spaceflight, resulting in atrophy of bone and muscle tissue, as well as in deficits in the function of cartilage, tendons, and vertebral disks. While inflight countermeasures implemented on the International Space Station have evidenced reduction of bone and muscle loss on low-Earth orbit missions of several months in length, important knowledge gaps must be addressed in order to develop effective strategies for managing human musculoskeletal health on exploration class missions well beyond Earth orbit. Analog environments, such as bed rest and/or isolation environments, may be employed in conjunction with large sample sizes to understand sex differences in countermeasure effectiveness, as well as interaction of exercise with pharmacologic, nutritional, immune system, sleep and psychological countermeasures. Studies of musculoskeletal biomechanics, involving both human subject and computer simulation studies, are essential to developing strategies to avoid bone fractures or other injuries to connective tissue during exercise and extravehicular activities. Animal models may be employed to understand effects of the space environment that cannot be modeled using human analog studies. These include studies of radiation effects on bone and muscle, unraveling the effects of genetics on bone and muscle loss, and characterizing the process of fracture healing in the mechanically unloaded and immuno-compromised spaceflight environment. In addition to setting the stage for evidence-based management of musculoskeletal health in long-duration space missions, the body of knowledge acquired in the process of addressing this array of scientific problems will lend insight into the understanding of terrestrial health conditions such as age-related osteoporosis and sarcopenia.

Oculopharyngeal muscular dystrophy (OPMD), a late-onset disorder characterized by progressive degeneration of specific muscles, results from the extension of a polyalanine tract in poly(A) binding protein nuclear 1 (PABPN1). While the roles of PABPN1 in nuclear polyadenylation and regulation of alternative poly(A) site choice are established, the molecular mechanisms behind OPMD remain undetermined. Here, we show, using Drosophila and mouse models, that OPMD pathogenesis depends on affected poly(A) tail lengths of specific mRNAs. We identify a set of mRNAs encoding mitochondrial proteins that are down-regulated starting at the earliest stages of OPMD progression. The down-regulation of these mRNAs correlates with their shortened poly(A) tails and partial rescue of their levels when deadenylation is genetically reduced improves muscle function. Genetic analysis of candidate genes encoding RNA binding proteins using the Drosophila OPMD model uncovers a potential role of a number of them. We focus on the deadenylation regulator Smaug and show that it is expressed in adult muscles and specifically binds to the down-regulated mRNAs. In addition, the first step of the cleavage and polyadenylation reaction, mRNA cleavage, is affected in muscles expressing alanine-expanded PABPN1. We propose that impaired cleavage during nuclear cleavage/polyadenylation is an early defect in OPMD. This defect followed by active deadenylation of specific mRNAs, involving Smaug and the CCR4-NOT deadenylation complex, leads to their destabilization and mitochondrial dysfunction. These results broaden our understanding of the role of mRNA regulation in pathologies and might help to understand the molecular mechanisms underlying neurodegenerative disorders that involve mitochondrial dysfunction., Author Summary Oculopharyngeal muscular dystrophy is a genetic disease characterized by progressive degeneration of specific muscles, leading to ptosis (eyelid drooping), dysphagia (swallowing difficulties) and proximal limb weakness. The disease results from mutations in a nuclear protein called poly(A) binding protein nuclear 1 that is involved in polyadenylation of messenger RNAs (mRNAs) and poly(A) site selection. To address the molecular mechanisms involved in the disease, we have used two animal models (Drosophila and mouse) that recapitulate the features of this disorder. We show that oculopharyngeal muscular dystrophy pathogenesis depends on defects in poly(A) tail length regulation of specific mRNAs. Because poly(A) tails play an essential role in mRNA stability, these defects result in accelerated decay of these mRNAs. The affected mRNAs encode mitochondrial proteins, and mitochondrial activity is impaired in diseased muscles. These findings have important implications for the development of potential therapies for oculopharyngeal muscular dystrophy, and might be relevant to decipher the molecular mechanisms underlying other disorders that involve mitochondrial dysfunction.

The aim of the present study was to test whether systems models of training effects on performance in athletes can be used to explore the responses to resistance training in rats. 11 Wistar Han rats (277 ± 15 g) underwent 4 weeks of resistance training consisting in climbing a ladder with progressive loads. Training amount and performance were computed from total work and mean power during each training session. Three systems models relating performance to cumulated training bouts have been tested: (i) with a single component for adaptation to training, (ii) with two components to distinguish the adaptation and fatigue produced by exercise bouts, and (iii) with an additional component to account for training-related changes in exercise-induced fatigue. Model parameters were fitted using a mixed-effects modeling approach. The model with two components was found to be the most suitable to analyze the training responses (R2=0.53;P<0.001). In conclusion, the accuracy in quantifying training loads and performance in a rodent experiment makes it possible to model the responses to resistance training. This modeling in rodents could be used in future studies in combination with biological tools for enhancing our understanding of the adaptive processes that occur during physical training.

Myostatin, a member of the transforming growth factor-β superfamily, is a potent negative regulator of skeletal muscle growth and is conserved in many species, from rodents to humans. Myostatin inactivation can induce skeletal muscle hypertrophy, while its overexpression or systemic administration causes muscle atrophy. As it represents a potential target for stimulating muscle growth and/or preventing muscle wasting, myostatin regulation and functions in the control of muscle mass have been extensively studied. A wealth of data strongly suggests that alterations in skeletal muscle mass are associated with dysregulation in myostatin expression. Moreover, myostatin plays a central role in integrating/mediating anabolic and catabolic responses. Myostatin negatively regulates the activity of the Akt pathway, which promotes protein synthesis, and increases the activity of the ubiquitin-proteasome system to induce atrophy. Several new studies have brought new information on how myostatin may affect both ribosomal biogenesis and translation efficiency of specific mRNA subclasses. In addition, although myostatin has been identified as a modulator of the major catabolic pathways, including the ubiquitin-proteasome and the autophagy-lysosome systems, the underlying mechanisms are only partially understood. The goal of this review is to highlight outstanding questions about myostatin-mediated regulation of the anabolic and catabolic signaling pathways in skeletal muscle. Particular emphasis has been placed on (1) the cross-regulation between myostatin, the growth-promoting pathways and the proteolytic systems; (2) how myostatin inhibition leads to muscle hypertrophy; and (3) the regulation of translation by myostatin.

Background/Aims: Overexpression of Gasp-1, an inhibitor of myostatin, leads to a hypermuscular phenotype due to hypertrophy rather than hyperplasia in mice. However to date, the cellular and molecular mechanisms underlying this phenotype are not investigated. Methods: Skeletal muscles of overexpressing Gasp-1 mice, called Tg(Gasp-1) mice, were analyzed by histological methods. Satellite cell-derived myoblasts from these mice were used to investigate the molecular mechanisms. Results: We demonstrated that hypertrophy in Tg(Gasp-1) mice was related to a myonuclear accretion during the first 3 postnatal weeks and an activation of the pro-hypertrophic Akt/mTORC/p70S6K signaling. In accordance with these results, we showed that overexpressing Gasp-1 primary myoblasts proliferated faster and myonuclei average per myotube was increased during differentiation. Molecular analysis revealed that Gasp-1 overexpression resulted in increased myostatin expression related to its auto-regulation. Despite its inhibition, myostatin led to Pax7 deregulation through its non-canonical Erk1/2 signaling pathway. Consistent with this, inhibition of Erk1/2 signaling pathway as well as neutralization of secreted myostatin rescue the Pax7 expression in overexpressing Gasp-1 myoblasts. Conclusion: Our study shows that myostatin is able to act independently of its canonical pathway to regulate the Pax7 expression. Altogether, our results indicate that myostatin could regulate muscle development despite its protein inhibition.

14. International Symposium on Cholinergic Mechanisms (ISCM), Hangzhou, 2013/05/05-9; A cholinesterase activity can be found in all kingdoms of living organism, yet cholinesterases involved in cholinergic transmission appeared only recently in the animal phylum. Among various proteins homologous to cholinesterases, one finds neuroligins. These proteins, with an altered catalytic triad and no known hydrolytic activity, display well-identified cell adhesion properties. The availability of complete genomes of a few metazoans provides opportunities to evaluate when these two protein families emerged during evolution. In bilaterian animals, acetylcholinesterase co-localizes with proteins of cholinergic synapses while neuroligins co-localize and may interact with proteins of excitatory glutamatergic or inhibitory GABAergic/glycinergic synapses. To compare evolution of the cholinesterases and neuroligins with other proteins involved in the architecture and functioning of synapses, we devised a method to search for orthologs of these partners in genomes of model organisms representing distinct stages of metazoan evolution. Our data point to a progressive recruitment of synaptic components during evolution. This finding may shed light on the common or divergent developmental regulation events involved into the setting and maintenance of the cholinergic versus glutamatergic and GABAergic/glycinergic synapses.

L'acetylcholinesterase (AChE, EC 3.1.1.7) est une enzyme indispensable de la transmission synaptique cholinergique. Son inhibition par les organophosphores et les carbamates est a la base de certains traitements insecticides et nematicides utilises en agriculture. Les faunes sauvage (en particulier les poissons) et domestique sont exposees aux residus des traitements anticholinesterasiques. La mesure de l'inhibition de l'activite AChE chez ces especes est un marqueur fiable de l'exposition. Ceci est montre ici pour l'AChE de carpes exposees experimentalement au carbofuran (carbamate). Nous presentons parallelement des donnees sur le gene de l'AChE chez Danio rerio et sur les formes moleculaires de l'enzyme chez Danio, Cyprinus carpio et Oncorhynchus mykiss. Contrairement a ce qui est observe chez d'autres vertebres, le gene d'AChE de Danio ne possede pas d'exon H et seules les sous-unites de type T ont pu etre identifiees chez ces trois especes. Des resultats preliminaires d'hybridation in situ sur les embryons sont presentes et nous discutons l'interet des experiences de transgenese dans l'oeuf de Danio pour etudier d'eventuelles fonctions morphogenetiques de l'AChE au debut du developpement.

Among T3 receptors, TRα1 is ubiquitous and its deletion or a specific expression of a dominant-negative TRα1 isoform in Sertoli cell leads to an increase in testis weight and sperm production. The identification of a 43-kDa truncated form of the nuclear receptor TRα1 (p43) in the mitochondrial matrix led us to test the hypothesis that this mitochondrial transcription factor could regulate Sertoli cell proliferation. Here we report that p43 depletion in mice increases testis weight and sperm reserve. In addition, we found that p43 deletion increases Sertoli cell proliferation in postnatal testis at 3 days of development. Electron microscopy studies evidence an alteration of mitochondrial morphology observed specifically in Sertoli cells of p43-/- mice. Moreover, gene expression studies indicate that the lack of p43 in testis induced an alteration of the mitochondrial-nuclear cross-talk. In particular, the up-regulation of Cdk4 and c-myc pathway in p43-/- probably explain the extended proliferation recorded in Sertoli cells of these mice. Our finding suggests that T3 limits post-natal Sertoli cell proliferation mainly through its mitochondrial T3 receptor p43.

The ESTHER database, which is freely available via a web server (http://bioweb.ensam.inra.fr/esther) and is widely used, is dedicated to proteins with an α/β-hydrolase fold, and it currently contains >30 000 manually curated proteins. Herein, we report those substantial changes towards improvement that we have made to improve ESTHER during the past 8 years since our 2004 update. In particular, we generated 87 new families and increased the coverage of the UniProt Knowledgebase (UniProtKB). We also renewed the ESTHER website and added new visualization tools, such as the Overall Table and the Family Tree. We also address two topics of particular interest to the ESTHER users. First, we explain how the different enzyme classifications (bacterial lipases, peptidases, carboxylesterases) used by different communities of users are combined in ESTHER. Second, we discuss how variations of core architecture or in predicted active site residues result in a more precise clustering of families, and whether this strategy provides trustable hints to identify enzyme-like proteins with no catalytic activity.

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Background Local anesthetics offer the benefits of extended analgesia with greater patient satisfaction and faster rehabilitation compared with intravenous morphine. These benefits, however, can be offset by adverse iatrogenic muscle pain. Here, the authors investigate the mechanisms of local anesthetic-induced myotoxicity and assess the protective effect of N-acetylcysteine. Methods The authors used primary cell cultures of human skeletal muscle myoblasts to study local anesthetic adverse effects. Production of reactive oxygen species was investigated in human skeletal myotubes by fluorescence microscopy. Expression of sarcoplasmic/endoplasmic reticulum stress markers and induction of apoptosis were followed by immunofluorescence and Western blot analysis. Finally, the effect of N-acetylcysteine on bupivacaine-induced myotoxicity was investigated in vitro. Results Bupivacaine sequentially induced reactive oxygen species production, oxidative stress, sarcoplasmic/endoplasmic reticulum stress, and activation of caspases 9 and 7 in human differentiated myoblasts. These iatrogenic effects were prevented by N-acetylcysteine. Conclusions The authors demonstrated a protective effect of N-acetylcysteine against bupivacaine-induced sarcoplasmic/endoplasmic reticulum stress and apoptosis in primary human skeletal muscle cell.

International audience; Although it is well established that chronic hypoxia leads to an inexorable loss of skeletal muscle mass in healthy subjects, the underlying molecular mechanisms involved in this process are currently unknown. Skeletal muscle atrophy is also an important systemic consequence of chronic obstructive pulmonary disease (COPD), but the role of hypoxemia in this regulation is still debated. Our general aim was to determine the molecular mechanisms involved in the regulation of skeletal muscle mass after exposure to chronic hypoxia and to test the biological relevance of our findings into the clinical context of COPD. Expression of positive and negative regulators of skeletal muscle mass were explored 1) in the soleus muscle of rats exposed to severe hypoxia (6,300 m) for 3 wk and 2) in vastus lateralis muscle of nonhypoxemic and hypoxemic COPD patients. In rodents, we observed a marked inhibition of the mammalian target of rapamycin (mTOR) pathway together with a strong increase in regulated in development and DNA damage response 1 (REDD1) expression and in its association with 14-3-3, a mechanism known to downregulate the mTOR pathway. Importantly, REDD1 overexpression in vivo was sufficient to cause skeletal muscle fiber atrophy in normoxia. Finally, the comparative analysis of skeletal muscle in hypoxemic vs. nonhypoxemic COPD patients confirms that hypoxia causes an inhibition of the mTOR signaling pathway. We thus identify REDD1 as a negative regulator of skeletal muscle mass during chronic hypoxia. Translation of this fundamental knowledge into the clinical investigation of COPD shows the interest to develop therapeutic strategies aimed at inhibiting REDD1.

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International audience; Calpain 3 is a calcium-dependent cysteine protease that is primarily expressed in skeletal muscle and is implicated in limb girdle muscular dystrophy type 2A. To date, its best characterized function is located within the sarcomere, but this protease is found in other cellular compartments, which suggests that it exerts multiple roles. Here, we present evidence that calpain 3 is involved in the myogenic differentiation process. In the course of in vitro culture of myoblasts to fully differentiated myotubes, a population of quiescent undifferentiated "reserve cells" are maintained. These reserve cells are closely related to satellite cells responsible for adult muscle regeneration. In the present work, we observe that reserve cells express higher levels of endogenous Capn3 mRNA than proliferating myoblasts. We show that calpain 3 participates in the establishment of the pool of reserve cells by decreasing the transcriptional activity of the key myogenic regulator MyoD via proteolysis independently of the ubiquitin-proteasome degradation pathway. Our results identify calpain 3 as a potential new player in the muscular regeneration process by promoting renewal of the satellite cell compartment.

At the mouse neuromuscular junction (NMJ), there are two distinct cholines-terases (ChE): acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Until now, it has been difficult to determine the precise localization of BChE at the NMJ. In this study, we use a modification of Koelle's method to stain AChE and BChE activity. This method does not interfere with fluorescent co-staining, which allows precise co-localization of ChE and other synaptic molecules at the NMJ. We demonstrate that AChE and BChE exhibit different localization patterns at the mouse NMJ. AChE activity is present both in the primary cleft and in the secondary folds, whereas BChE activity appears to be almost absent in the primary cleft and to be concentrated in subsynaptic folds. The same localization for BChE is observed in the AChE-knockout (KO) mouse NMJ. Collagenase treatment removed AChE from the primary cleft, but not from secondary folds in the wild-type mouse, whereas in the AChE-KO mouse, BChE remains in the secondary folds. After peripheral nerve injury and regeneration, BChE localization is not modified in either normal or KO mice. In conclusion, specific localization of BChE in the secondary folds of the NMJ suggests that this enzyme is not a strict surrogate of AChE and that the two enzymes have two different roles. (J Histochem Cytochem 58:1075–1082, 2010)

The nutritional regulation of skeletal muscle growth is very little documented in fish. The aim of the study presented here was to determine how changes in dietary plant protein sources and amino acid profiles affect the muscle growth processes of fish. Juvenile rainbow trout (Oncorhynchys mykiss) were fed two diets containing fish meal and a mixture of plant protein sources either low (control diet) or rich in soybean meal (diet S). Both diets were supplemented with crystalline indispensable amino acids (IAA) to match the rainbow trout muscle IAA profile. Diet S was also supplemented with glutamic acid, an AA present in high quantities in trout muscle. Rainbow trout fed diets C and S were not significantly different in terms of overall somatic growth or daily nitrogen gain, although their parameters of dietary protein utilisation differed. Distribution of skeletal white muscle fibre diameter and expression of certain selected muscle genes were also affected by dietary changes. In the white muscle, diet S led to a significant decrease (x0.9) in the mean and median diameters of muscle fibres, to a significant decrease (x0.6) in the expression of MyoD and to a significant increase (x1.7) in the expression of fast-MHC, with no significant changes in myogenin expression. There was no change in the expression of the genes analysed in lateral red muscle (MyoD, MyoD2, myogenin and slow-MHC). These results demonstrated that changes occurred in skeletal white muscle cellularity and expression of MyoD and fast-MHC, although overall growth and protein accretion were not modified, when a diet rich in soybean meal and glutamic acid was ingested. Present findings also indicated that the white and red muscles of rainbow trout are differently affected by nutritional changes.

Resistance of arthropods to organophosphates and carbamates used as insecticides is mainly due to mutations in genes encoding carboxylesterase or acetylcholinesterase members of the alpha/beta-hydrolase fold superfamily of proteins. Mutations that have been described at the molecular level concern 24 species, 31 genes and 32 identical positions in the aligned aminoacid sequences. Seven of these positions are found in more than four species and can be considered as hot spots for mutations. Mutations in one single gene also result in cross resistance to pyrethroids. These figures along with all pieces of information related to these mutations can be recovered from the ESTHER database, dedicated to the alpha/beta-hydrolase fold superfamily (http://bioweb.ensam.inra.fr/ esther), through built-in or custom made queries. A sequence alignment of enzymes involved in resistance with highlighted mutated amino acid residues is provided. Selecting one amino acid residue leads to all information about mutations analyzed at this position. Links to the related literature are also available. © Pesticide Science Society of Japan

Corresponding author: Dr Christine Feillet-Coudray, fax : + 33 4 67 54 56 94, email : cfeillet@supagro.inra.fr; International audience; High-fat or high-fat–high-sucrose diets are known to induce non-alcoholic fatty liver disease and this is emerging as one of the most common liver diseases worldwide. Some polyphenols have been reported to decrease rat hepatic lipid accumulation, in particular those extracted from red grapes such as resveratrol. The present study was designed to determine whether a polyphenol extract (PPE), from red grapes, modulates liver fatty acid composition and desaturase activity indexes in rats fed a high-fat–high-sucrose (HFHS) diet, and to explore whether sirtuin-1 deacetylase activation was implicated in the effect of the PPE against liver steatosis. The effect of this PPE on mitochondriogenesis and mitochondrial activity was also explored. The PPE decreased liver TAG content in HFHS þ PPE diet-fed rats in comparison with HFHS diet-fed rats. The PPE had no effect on liver fatty acid composition, desaturase activity indexes and stearoyl-CoA desaturase 1 (SCD1) gene expression. Sirtuin-1 deacetylase protein expression was significantly increased with the PPE; AMP kinase protein expression was higher with the PPE in comparison with the HFHS rats, but no modification of phosphorylated AMP kinase was observed. Protein expression of phospho-acetyl-CoA carboxylase was decreased in HFHS rats and returned to basal values with the PPE. Finally, the PPE modulated PPARg coactivator-1a (PGC-1a) but did not modify mitochondriogenesis and mitochondrial activity. In conclusion, the PPE partially prevented the accumulation of TAG in the liver by regulating acetyl-CoA carboxylase phosphorylation, a key enzyme in lipid metabolism, probably via sirtuin-1 deacetylase activation. However, the PPE had no effect on the qualitative composition of liver fatty acids.

International audience; Avian uncoupling protein (avUCP) is orthologous to UCP3, which is suggested to be involved in fatty acid metabolism and to limit the mitochondrial production of reactive oxygen species in mammals. In the chicken, the role and regulation of avUCP remain to be clarified. The aim of this study was to explore the control of avUCP expression by the beta-adrenergic system, known to be involved in avian thermoregulation and lipid utilization, and in UCP expression in mammals. Therefore, we measured the expression of avUCP mRNA and protein in the Pectoralis major muscle of chickens injected with the beta(2) agonist isoproterenol, and we investigated the potential pathways involved in the regulation of avUCP mRNA expression. Avian UCP mRNA expression was increased 7-fold 4 h after isoproterenol injection, leading to a tendency to a 40% increase in avUCP protein 24 h post-injection. This increase was preceded, 30 min after isoproterenol injection, by changes in the chicken thyroid status and in the muscular expression of PPAR alpha, PPAR beta/delta, and PPAR gamma coactivator-1 alpha (PGC-1 alpha). Moreover, the analysis of the avUCP promoter sequence suggested potential binding sites for PPARs and for thyroid hormone receptors. We also detected the activation of AMP-activated protein kinase, which has recently been reported to be involved in UCP3 regulation in mammals. This study presents for the first time evidence of beta-adrenergic control on avUCP messenger expression in chicken muscle and suggests the potential involvement of AMPK and several transcription factors in this regulation. (C) 2010 Elsevier Inc. All rights reserved.

International audience; The proliferation of the malaria-causing parasite Plasmodium falciparum within the erythrocyte is concomitant with massive phosphatidylcholine and phosphatidylethanolamine biosynthesis. Based on pharmacological and genetic data, de novo biosynthesis pathways of both phospholipids appear to be essential for parasite survival. The present study characterizes PfCK (P. falciparum choline kinase) and PfEK (P. falciparum ethanolamine kinase), which catalyse the first enzymatic steps of these essential metabolic pathways. Recombinant PfCK and PfEK were expressed as His6-tagged fusion proteins from overexpressing Escherichia coli strains, then purified to homogeneity and characterized. Using murine polyclonal antibodies against recombinant kinases, PfCK and PfEK were shown to be localized within the parasite cytoplasm. Protein expression levels increased during erythrocytic development. PfCK and PfEK appeared to be specific to their respective substrates and followed Michaelis-Menten kinetics. The Km value of PfCK for choline was 135.3+/-15.5 microM. PfCK was also able to phosphorylate ethanolamine with a very low affinity. PfEK was found to be an ethanolamine-specific kinase (Km=475.7+/-80.2 microM for ethanolamine). The quaternary ammonium compound hemicholinium-3 and an ethanolamine analogue, 2-amino-1-butanol, selectively inhibited PfCK or PfEK. In contrast, the bis-thiazolium compound T3, which was designed as a choline analogue and is currently in clinical trials for antimalarial treatment, affected PfCK and PfEK activities similarly. Inhibition exerted by T3 was competitive for both PfCK and PfEK and correlated with the impairment of cellular phosphatidylcholine biosynthesis. Comparative analyses of sequences and structures for both kinase types gave insights into their specific inhibition profiles and into the dual capacity of T3 to inhibit both PfCK and PfEK.

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International audience; Cholinesterases emerged from a family of enzymes and proteins with adhesion properties. This family is absent in plants and expanded in multicellular animals. True cholinesterases appeared in triploblastic animals together with the cholinergic system. Lineage specific duplications resulted in two acetylcholinesterases in most hexapods and in up to four genes in nematodes. In vertebrates the duplication leading to acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) is now considered to be an ancient event which occurred before the split of osteichthyes. The product of one or the other of the paralogues is responsible for the physiological hydrolysis of acetylcholine, depending on the species lineage and tissue considered. The BChE gene seems to have been lost in some fish lineages. The complete genome of amphioxus (Branchiostoma floridae: cephalochordate) contains a large number of duplicated genes or pseudogenes of cholinesterases. Sequence comparison and tree constructions raise the question of considering the atypical ChE studied in this organism as a representative of ancient BChE. Thus nematodes, arthropods, annelids, molluscs, and vertebrates typically possess two paralogous genes coding for cholinesterases. The origin of the duplication(s) is discussed. The mode of attachment through alternative C-terminal coding exons seems to have evolved independently from the catalytic part of the gene.

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International audience; Studies showed that dietary antioxidants could be a therapy against obesity that is associated with a state of oxidative stress. Thus, this paper investigates whether a dietary ingredient, a melon juice extract rich in superoxide dismutase, would prevent the development of such obesity in hamsters. Five groups received a standard diet or a high-fat diet (HF) plus a daily gavage with water (control) or extract at 0.7, 2.8, or 5.6 mg/day. After 84 days, the higher dose lowered triglyceridemia (68%), production of liver superoxide anion (12%), mitochondrial cytochrome c oxidase activity (40%), lipid and protein oxidation products (35 and 35%, respectively), and leptinemia (99%) and increased adiponectinemia (29%), leading to a concomitant reduction in insulinemia (39%), insulin resistance (41%), and abdominal lipids (25%). The extract triggered a remarkable decrease of liver lipids (73%) and fully prevented the steatohepatitis induced by the HF diet. Chronic consumption of this melon extract may represent a new alternative to reduce obesity induced by a high-fat diet.

International audience; Antioxidants could be a therapy against obesity. We investigated whether a melon juice extract rich in superoxide dismutase activity would prevent its development in hamsters. Three groups received either a standard diet or a high fat diet (HF) plus a daily gavage with water (Control) or extract. After 12 weeks, the extract lowered triglyceridemia (67 percent), liver superoxide anion production (11 percent), lipid and protein oxidation products (35 and 35.7 percent), leptinemia (29 percent) and increased adiponectinemia (22 percent), leading to a concomitant reduction in insulinemia (39 percent), insulin resistance (41 percent) and abdominal lipids (28 percent). It decreased liver lipids (71 percent) and fully prevented the steatohepatitis induced by HF diet. Functional foods containing this melon extract could be an important new therapy to prevent obesity.

to the editor: Zoladz et al. ([6][1]) present a reanalysis of data taken from their previous study ([3][2]) and they evaluated the oxygen uptake (Vo2) response in isolated dog gastrocnemius in situ during 4-min of contractions at ∼60–70% of peak Vo2. In their preparation, all muscle fibers

International audience; Ubiquitin ligase Atrogin1/Muscle Atrophy F-box (MAFbx) up-regulation is required for skeletal muscle atrophy but substrates and function during the atrophic process are poorly known. The transcription factor MyoD controls myogenic stem cell function and differentiation, and seems necessary to maintain the differentiated phenotype of adult fast skeletal muscle fibres. We previously showed that MAFbx mediates MyoD proteolysis in vitro. Here we present evidence that MAFbx targets MyoD for degradation in several models of skeletal muscle atrophy. In cultured myotubes undergoing atrophy, MAFbx expression increases, leading to a cytoplasmic-nuclear shuttling of MAFbx and a selective suppression of MyoD. Conversely, transfection of myotubes with sh-RNA-mediated MAFbx gene silencing (shRNAi) inhibited MyoD proteolysis linked to atrophy. Furthermore, overexpression of a mutant MyoDK133R lacking MAFbx-mediated ubiquitination prevents atrophy of mouse primary myotubes and skeletal muscle fibres in vivo. Regarding the complex role of MyoD in adult skeletal muscle plasticity and homeostasis, its rapid suppression by MAFbx seems to be a major event leading to skeletal muscle wasting. Our results point out MyoD as the second MAFbx skeletal muscle target by which powerful therapies could be developed

International audience; In previous studies, we characterized a new hormonal pathway involving a mitochondrial T3 receptor (p43) acting as a mitochondrial transcription factor. In in vitro and in vivo studies, we have shown that p43 increases mitochondrial transcription and mitochondrial biogenesis. In addition, p43 overexpression in skeletal muscle stimulates mitochondrial respiration and induces a shift in metabolic and contractile features of muscle fibers which became more oxidative. Here we have studied the influence of p43 overexpression in skeletal muscle of mice during aging. We report that p43 overexpression initially increased mitochondrial mass. However, after the early rise in mitochondrial DNA occurring at 2 months of age in transgenic mice, we observed a progressive decrease of mitochondrial DNA content which became 2-fold lower at 23 months of age relatively to control animals. Moreover, p43 overexpression induced an oxidative stress characterized by a strong increase of lipid peroxidation and protein oxidation in quadriceps muscle, although antioxidant enzyme activities (catalase and superoxide dismutase) were stimulated. In addition, muscle atrophy became detectable at 6 months of age, probably through a stimulation of the ubiquitin proteasome pathway via two muscle-specific ubiquitin ligases E3, Atrogin-1/MAFbx and MuRF1. Taken together, these results demonstrate that a prolonged stimulation of mitochondrial activity induces muscle atrophy. In addition, these data underline the importance of a tight control of p43 expression and suggest that a deregulation of the direct T3 mitochondrial pathway could be one of the parameters involved in the occurrence of sarcopenia.

To further characterize the molecular events supporting the tumor suppressor activity of Scrib in mammals, we aim to identify new binding partners. We isolated MCC, a recently identified binding partner for β-catenin, as a new interacting protein for Scrib. MCC interacts with both Scrib and the NHERF1/NHERF2/Ezrin complex in a PDZ-dependent manner. In T47D cells, MCC and Scrib proteins colocalize at the cell membrane and reduced expression of MCC results in impaired cell migration. By contrast to Scrib, MCC inhibits cell directed migration independently of Rac1, Cdc42 and PAK activation. Altogether, these results identify MCC as a potential scaffold protein regulating cell movement and able to bind Scrib, β-catenin and NHERF1/2.Structured summaryMINT-7211022: SCRIB (uniprotkb:Q14160) and MCC (uniprotkb:P23508) colocalize (MI:0403) by fluorescence microscopy (MI:0416)MINT-7210609: SCRIB (uniprotkb:Q14160) physically interacts (MI:0915) with MCC (uniprotkb:P23508) by two hybrid (MI:0018)MINT-7210759, MINT-7210792: SCRIB (uniprotkb:Q14160) physically interacts (MI:0914) with PIX beta (uniprotkb:Q14155) by pull down (MI:0096)MINT-7210883, MINT-7210820: SCRIB (uniprotkb:Q14160) physically interacts (MI:0914) with MCC (uniprotkb:P23508) by anti bait coimmunoprecipitation (MI:0006)MINT-7210634, MINT-7210690, MINT-7210731: SCRIB (uniprotkb:Q14160) physically interacts (MI:0914) with MCC (uniprotkb:P23508) by pull down (MI:0096)MINT-7211267: E6 (uniprotkb:P06463) physically interacts (MI:0915) with SCRIB (uniprotkb:Q14160), SNX27 (uniprotkb:Q96L92), UTRN (uniprotkb:P46939), CASK (uniprotkb:O14936), DMD (uniprotkb:P11532) and Dlg (uniprotkb:Q12959) by pull down (MI:0096)MINT-7211237: MCC (uniprotkb:P23508) physically interacts (MI:0915) with SCRIB (uniprotkb:Q14160), EZR (uniprotkb:P15311), SNX27 (uniprotkb:Q96L92), NHERF1 (uniprotkb:O14745) and NHERF2 (uniprotkb:Q15599) by pull down (MI:0096)

National audience; The molecular signals that regulate satellite cell function remain largely obscure. However, it was recently demonstrated that Wnts participate in the temporal control of satellite cell expansion versus differentiation during adult muscle regeneration (Brack et al, 2008). Thus, differentiation of myoblasts in vitro and in vivo is correlated with an upregulation of canonical Wnt signaling. Furthermore, ectopic Wnt induces premature muscle differentiation whereas inhibition of Wnt signaling interferes with muscle differentiation. In this context, the fact that myostatin -a member of the TGF-β superfamily that specifically regulates muscle mass- was shown to implicate Wnt4 signaling in postnatal skeletal muscle hypertrophy is of the upmost importance (Steelman et al, 2006). This was corroborated by Takata et al, (2007) showing the involvement of Wnt4 signaling during myogenic proliferation and dfferentiation of skeletal muscle. In this context, we first established by SQ-PCR that a limited number of Wnts was expressed during proliferation and differentiation of C2C12 myoblasts and satellite cells (SC). Amongst the 19 Wnts examined, we noticed that only the expression of Wnt4 was lacking during proliferation and was highly induced during differentiation of both cell types. The aim of this study was thus to characterize the role of Wnt4 protein in muscle homeostasis. The effects of Wnt4 on myogenic differentiation were examined by modulating the expression level of this factor. We showed that over-expression of Wnt4 in proliferative state by transient or stable transfection was responsible for spontaneous differentiation (C2C12) or an important myotube hypertrophy (SC). Conversely, inhibition of Wnt4 expression by siRNA silencing on SC leaded to an atrophy of differentiated myotubes (myotube areas correspond to 40% of siRNA luciferase controls) and a decrease in fusion index (24%). Treatment of C2C12 myoblasts by Wnt4 siRNA induced a strong inhibition of differentiation associated with a decrease in the expression of Myf5.

International audience; The control of muscle cell size is a physiological process balanced by a fine tuning between protein synthesis and protein degradation. MAFbx/Atrogin-1 is a muscle specific E3 ubiquitin ligase up regulated during disuse, immobilization and fasting or systemic diseases such as diabetes, cancer, SIDA and renal failure. This response is necessary to induce a rapid and functional atrophy. To date, the targets of MAFbx/Atrogin-1 in skeletal muscle remain to be identified. We have recently presented evidence that eIF3-f, a regulatory subunit of the eukaryotic translation factor eIF3 is a key target that accounts for MAFbx/Atrogin-1 function in muscle atrophy. More importantly, we showed that eIF3-f act as a “translational enhancer” that increases the efficiency of the structural muscle proteins synthesis leading to both in vitro and in vivo muscle hypertrophy. We propose that eIF3-f subunit, a mTOR/ S6K1 scaffolding protein in the IGF-1/Akt/mTOR dependant control of protein translation, is a positive actor essential to the translation of specific mRNAs probably implicated in the muscle hypertrophy. The central role of eIF3-f in both the atrophic and hypertrophic pathways will be discussed in the light of its promising potential in muscle wasting therapy.

International audience; During aging, skeletal muscle undergoes sarcopenia, a condition characterized by a loss of muscle cell mass and alterations in contractile function. The origin of these decrements is unknown, but evidence suggests that they can be partly attributed to mitochondrial dysfunction. To characterize the nature of this dysfunction, we investigated skeletal muscle contractile properties, subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondrial biogenesis and function, as well as apoptotic susceptibility in young (6 months old) and senescent (36 months old) Fischer 344 Brown Norway rats. Muscle mass and maximal force production were significantly lower in the 36-month group, which is indicative of a sarcopenic phenotype. Furthermore, contractile activity in situ revealed greater fatigability in the 36-month compared to the 6-month animals. This decrement could be partially accounted for by a 30% lower mitochondrial content in fast-twitch muscle from 36-month animals, as well as lower protein levels of the transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator-1 alpha. Enzyme activities and glutamate-induced oxygen consumption rates in isolated SS and IMF mitochondria were similar between age groups. However, mitochondrial reactive oxygen species (ROS) production during state 3 respiration was similar to 1.7-fold greater in mitochondria isolated from 36-month compared to 6-month animals, and was accompanied by a 1.8-fold increase in the DNA repair enzyme 8-oxoguanine glycosylase 1 in fast-twitch muscle. Basal rates of release of cytochrome c and endonuclease G in SS mitochondria were 3.5- to 7-fold higher from senescent animals. These data suggest that the age-related sarcopenia and muscle fatigability are associated with enhanced ROS production, increased mitochondrial apoptotic susceptibility and reduced transcriptional drive for mitochondrial biogenesis.

In previous studies, we have characterized a new hormonal pathway involving a mitochondrial T3 receptor (p43) acting as a mitochondrial transcription factor and consequently stimulating mitochondrial activity and mitochondrial biogenesis. We have established the involvement of this T3 pathway in the regulation of in vitro myoblast differentiation. We have generated mice overexpressing p43 under control of the human alpha-skeletal actin promoter. In agreement with the previous characterization of this promoter, northern-blot and western-blot experiments confirmed that after birth p43 was specifically overexpressed in skeletal muscle. As expected from in vitro studies, in 2-month old mice, p43 overexpression increased mitochondrial genes expression and mitochondrial biogenesis as attested by the increase of mitochondrial mass and mt-DNA copy number. In addition, transgenic mice had a body temperature 0.8 degrees C higher than control ones and displayed lower plasma triiodothyronine levels. Skeletal muscles of transgenic mice were redder than wild-type animals suggesting an increased oxidative metabolism. In line with this observation, in gastrocnemius, we recorded a strong increase in cytochrome oxidase activity and in mitochondrial respiration. Moreover, we observed that p43 drives the formation of oxidative fibers: in soleus muscle, where MyHC IIa fibers were partly replaced by type I fibers; in gastrocnemius muscle, we found an increase in MyHC IIa and IIx expression associated with a reduction in the number of glycolytic fibers type IIb. In addition, we found that PGC-1alpha and PPARdelta, two major regulators of muscle phenotype were up regulated in p43 transgenic mice suggesting that these proteins could be downstream targets of mitochondrial activity. These data indicate that the direct mitochondrial T3 pathway is deeply involved in the acquisition of contractile and metabolic features of muscle fibers in particular by regulating PGC-1alpha and PPARdelta.

International audience; To learn more about the evolution of the cholinesterases (ChEs), acetylcholinesterase (AChE) and butyrylcholinesterase in the vertebrates, we investigated the AChE activity of a deuterostome invertebrate, the urochordate Ciona intestinalis, by expressing in vitro a synthetic recombinant cDNA for the enzyme in COS-7 cells. Evidence from kinetics, pharmacology, molecular biology, and molecular modeling confirms that the enzyme is AChE. Sequence analysis and molecular modeling also indicate that the cDNA codes for the AChE(T) subunit, which should be able to produce all three globular forms of AChE: monomers (G(1)), dimers (G(2)), and tetramers (G(4)), and assemble into asymmetric forms in association with the collagenic subunit collagen Q. Using velocity sedimentation on sucrose gradients, we found that all three of the globular forms are either expressed in cells or secreted into the medium. In cell extracts, amphiphilic monomers (G(1)(a)) and non-amphiphilic tetramers (G(4)(na)) are found. Amphiphilic dimers (G(2)(a)) and non-amphiphilic tetramers (G(4)(na)) are secreted into the medium. Co-expression of the catalytic subunit with Rattus norvegicus collagen Q produces the asymmetric A(12) form of the enzyme. Collagenase digestion of the A(12) AChE produces a lytic G(4) form. Notably, only globular forms are present in vivo. This is the first demonstration that an invertebrate AChE is capable of assembling into asymmetric forms. We also performed a phylogenetic analysis of the sequence. We discuss the relevance of our results with respect to the evolution of the ChEs in general, in deuterostome invertebrates, and in chordates including vertebrates.

International audience; Nucleotide oligomerisation domain 2 (NOD2) is a component of the innate immunity known to be involved in the homeostasis of Peyer patches (PPs) in mice. However, little is known about its role during gut infection in vivo. Yersinia pseudotuberculosis is an enteropathogen causing gastroenteritis, adenolymphitis and septicaemia which is able to invade its host through PPs. We investigated the role of Nod2 during Y. pseudotuberculosis infection. Death was delayed in Nod2 deleted and Crohn’s disease associated Nod2 mutated mice orogastrically inoculated with Y. pseudotuberculosis. In PPs, the local immune response was characterized by a higher KC level and a more intense infiltration by neutrophils and macrophages. The apoptotic and bacterial cell counts were decreased. Finally, Nod2 deleted mice had a lower systemic bacterial dissemination and less damage of the haematopoeitic organs. This resistance phenotype was lost in case of intraperitoneal infection. We concluded that Nod2 contributes to the susceptibility to Y. pseudotuberculosis in mice.

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International audience; Bit-error-rate assessment of a multi-rate all-optical clock recovery (OCR) based on a narrow linewidth mode-locked quantum-dot (QD) Fabry-PÉrot laser is presented in this letter. OCR has been achieved without external feedback. We use a QD Fabry-PÉrot semiconductor laser designed for 40-GHz clock extraction. We then present OCR performance with 40-, 80-, and 160 Gb/s input data signal and demonstrate that clock recovery has been obtained thanks to subharmonic locking process. Results are presented through penalty measurement using an original characterization based on recovered clock remodulation with electrical data from the transmitter. This technique allows us to evaluate the quality of the recovered clock.

International audience; To learn more about the evolution of the cholinesterases, acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) in the vertebrates, we investigated the AChE activity of a deuterostome invertebrate, the urochordate Ciona intestinalis, by expressing in vitro a synthetic recombinant cDNA for the enzyme in COS-7 cells. On the basis of evidence from kinetics, pharmacology, molecular biology and molecular modeling, we confirm that the enzyme is AChE. Sequence analysis also suggests that the cDNA is AChET and should be able to code for all three globular forms of AChE: monomers (G1), dimers (G2), and tetramers (G4); and, assemble into asymmetric forms in association with the collagenic subunit colQ. Using velocity sedimentation on sucrose gradients, we found that all three of the globular forms are either expressed in cells or secreted into the medium. In cells, amphiphilic G1a and non-amphiphilic G4na forms are found. Amphiphilic G2a and non-amphiphilic G4na forms are secreted into the medium. When the catalytic subunit is co-expressed with rat colQ the A12 form of the enzyme is expressed. Collagenase digestion of the A12 AChE at 37°C produces a lytic G4 form; only globular forms are present in vivo. This is the first demonstration that an invertebrate AChE is capable of assembling into asymmetric forms. We also performed a phylogenetic analysis of the sequence. We will discuss the relevance of our results to the evolution of the cholinesterases in general, in deuterostome invertebrates, and in chordates including vertebrates.

International audience; Acetylcholinesterase (AChE) is the main catabolic enzyme of acetylcholine, responsible for the synaptic clearance of the neurotransmitter from the synaptic cleft. Decrease in AChE expression, or activity, results in increased cholinergic tonus in the brain or periphery, with concomittant regulations of nicotinic and muscarinic receptors expression. We generated AChE knockout mice and characterized the behavioral phenotype of heterozygous animals, particularly focusing on learning and memory functions. Male and female, AChE+/- and AChE+/+ littermate controls (129sv strain), tested at 5-9 weeks of age, failed to show any difference in terms of locomotion, exploration and anxiety parameters in the open-field test. Animals were then tested for place learning in the water-maze. They were trained using a 'sustained acquisition' protocol (3 swims/day during 5 days) or a 'mild acquisition' protocol (2 swims/day during 9 days) to locate an invisible platform in fixed position (reference memory procedure). Then, during 3 days, they were trained to locate the platform in a variable position (working memory procedure). Learning profiles and probe test performances were unchanged in AChE+/- mice as compared with AChE+/+. Mice were then treated with the muscarinic M1 antagonist scopolamine (0.5, 5 mg/kg sc) 20 min before each training session (3 swims/day during 5 days). Scopolamine impaired learning at both doses in AChE+/+ mice, but only at the highest dose in AChE+/- mice. Moreover, the central injection of amyloid beta25-35 peptide (9 nmol) failed to induce learning deficits in AChE+/- mice, contrarily to AChE+/+ controls. These behavioral study shows that the increase in cholinergic tonus did not result in increased memory abilities in these heterozygous AChE+/- mice, but allowed a significant prevention of the deleterious effects of muscarinic blockade or amyloid toxicity.

International audience; The commonly used live attenuated vaccine in ovine brucellosis prophylaxis is Brucella melitensis Rev. 1. This vaccine is known to induce antibody responses in vaccinated animals indistinguishable by the current conventional serological tests from those observed in challenged animals. Brucella BP26 and Omp31 proteins have shown an interesting potential as diagnostic antigens for ovine brucellosis. Accordingly, the bp26 gene and both bp26 and omp31 genes have been deleted from the vaccine strain Rev. 1. Immunogenicity and vaccine efficacy of the parental Rev. 1 strain and of both mutants in protecting sheep against B. inelitensis strain H38 challenge was evaluated by clinical and bacteriological examination of ewes. They were conjunctivally or subcutaneously vaccinated when 4 months old and then challenged with B. melitensis H38 at the middle of the first pregnancy following vaccination. Deletion of bp26 and omp31 genes did not significantly affect the well recognised capacity of Rev. 1 to protect sheep against B. melitensis challenge. However, the protection conferred by the CGV2631 mutant was significantly lower than that conferred by the CGV26 mutant or the Rev. I strain. Vaccinated and challenged animals were detected positive in classical serological tests and in the IFN-gamma assay. A BP26-based ELISA was investigated to discriminate between ewes vaccinated by the mutants and ewes challenged with B. inelitensis H38. The cut-off which was chosen in order to have 100% specificity resulted in a moderate sensitivy for the detection of challenged ewes. The use in the field of one of the mutants as vaccine against a B. inelitensis infection, combined with classic diagnostic tests and a BP26 ELISA, could thus give an improvement in the differentiation between vaccinated and infected animals and contribute to the objective of eradication of brucellosis in small ruminants. (c) 2006 Elsevier Ltd. All rights reserved.

International audience; Myostatin is a member of the TGF beta family which plays a major role in negative regulation of muscle development. Not only do mstn-/-mice display a dramatic increase in skeletal muscle mass, cattle harboring loss of function mutations in the myostatin gene also exhibit muscle overdevelopment associated to a shift in the contractile and metabolic features of muscles fibers. The occurrence of such mutations associated to increased muscle mass in humans has also been reported. Recent data clearly suggest that myostatin is also involved in muscle tissue maintenance in adults, in particular by activating pathways leading to proteolysis and satellite cell activity. As myostatin expression generally increases during muscle atrophy, some promising attempts have been made to improve the behavior of some muscle pathologies, such as myopathies, by targeting myostatin activity. These attempts have opened the way for novel pharmacological strategies focused on skeletal muscle diseases. Here we review the physiopathological consequences of changes in myostatin expression and their clinical interest. We also briefly address the myostatin molecular pathway by describing the knowledge which makes it possible to test the efficiency of pharmacological inhibition of this growth factor activity in muscle pathologies.

International audience; Heat shock protein (HSP)-70 is expressed in normal and stressed cells but is highly stress-inducible. Although leptin has long been suggested to be involved in the regulation of stress response, its interaction with the HSP-70 gene is still unknown, under both unstressed and stressed conditions. The present study has aimed to investigate the effect of leptin on HSP-70 gene expression in normal chicken liver, hypothalamus, and muscle. Continuous infusion of recombinant chicken leptin (8 mu g/kg per hour) at a constant rate of 3 ml/h for 6 h in 3-week-old broiler chickens significantly (P < 0.05) decreased food intake and HSP-70 mRNA levels in liver and hypothalamus, but not in muscle. In an attempt to discriminate between the effect of leptin and of leptin-reduced food intake on HSP-70 gene expression, we also evaluated the effect of food deprivation on the same cellular responses in two broiler chicken lines genetically selected for low (LL) or high (FL) abdominal fat pad size. Food deprivation for 16 h did not affect HSP-70 gene expression in any of the studied tissues indicating that the effect of leptin was independent of the inhibition of food intake. Regardless of the nutritional status, HSP-70 mRNA levels were significantly (P < 0.05) higher in the hypothalamus of FL compared with LL chickens consistent with higher mRNA levels for hypothalamic corticotropin-releasing factor. To assess, whether the effects of leptin were direct or indirect, we carried out in vitro studies. Leptin treatments did not affect HSP-70 mRNA levels in a leghorn male hepatoma cell line or quail myoblast cell line suggesting that the effect of leptin on HSP-70 gene expression is mediated through the central nervous system. Furthermore, HSP-70 gene expression was gender-dependent with significantly (P < 0.05) higher levels in male than in female chickens.

International audience; Myostatin, which was cloned in 1997, is a potent inhibitor of skeletal muscle growth and member of the tumour growth factor-beta family. Disruption of the myostatin gene in mice induces a dramatic increase in muscle mass, caused by a combination of hypertrophy and hyperplasia. Natural mutations occurring in cattle were also associated with a significant increase in muscle mass and, recently, an inactivating myostatin mutation associated with the same phenotype was identified in humans. Studies into the molecular basis of this antimyogenic influence led to the conclusion that myostatin inhibits myoblast proliferation and differentiation through a classical tumour growth factor-beta pathway involving the activin receptor ActRIIB and Smads 2 and 3. Approaches that induce myostatin depletion or inactivation have led to a significant improvement in muscle regeneration processes, especially in degenerative diseases, through stimulation of satellite cell proliferation and differentiation. These promising data open the way to new therapeutic approaches in muscle diseases through targeting of the myostatin pathway.