RÉSUMÉ
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the loss of motoneurons (MNs), and despite progress, there is no effective treatment. A large body of evidence shows that astrocytes expressing ALS-linked mutant proteins cause non-cell autonomous toxicity of MNs. Although MNs innervate muscle fibers and ALS is characterized by the early disruption of the neuromuscular junction (NMJ) and axon degeneration, there are controversies about whether muscle contributes to non-cell-autonomous toxicity to MNs. In this study, we generated primary skeletal myotubes from myoblasts derived from ALS mice expressing human mutant SOD1 G93A (termed hereafter mutSOD1). Characterization revealed that mutSOD1 skeletal myotubes display intrinsic phenotypic and functional differences compared to control myotubes generated from non-transgenic (NTg) littermates. Next, we analyzed whether ALS myotubes exert non-cell-autonomous toxicity to MNs. We report that conditioned media from mutSOD1 myotubes (mutSOD1-MCM), but not from control myotubes (NTg-MCM), induced robust death of primary MNs in mixed spinal cord cultures and compartmentalized microfluidic chambers. Our study further revealed that applying mutSOD1-MCM to the MN axonal side in microfluidic devices rapidly reduces mitochondrial axonal transport while increasing Ca2+ transients and reactive oxygen species (i.e., H 2 O 2 ). These results indicate that soluble factor(s) released by mutSOD1 myotubes cause MN axonopathy that leads to lethal pathogenic changes.
RÉSUMÉ
Non-cell-autonomous mechanisms contribute to neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), in which astrocytes release unidentified factors that are toxic to motoneurons (MNs). We report here that mouse and patient iPSC-derived astrocytes with diverse ALS/FTD-linked mutations (SOD1, TARDBP, and C9ORF72) display elevated levels of intracellular inorganic polyphosphate (polyP), a ubiquitous, negatively charged biopolymer. PolyP levels are also increased in astrocyte-conditioned media (ACM) from ALS/FTD astrocytes. ACM-mediated MN death is prevented by degrading or neutralizing polyP in ALS/FTD astrocytes or ACM. Studies further reveal that postmortem familial and sporadic ALS spinal cord sections display enriched polyP staining signals and that ALS cerebrospinal fluid (CSF) exhibits increased polyP concentrations. Our in vitro results establish excessive astrocyte-derived polyP as a critical factor in non-cell-autonomous MN degeneration and a potential therapeutic target for ALS/FTD. The CSF data indicate that polyP might serve as a new biomarker for ALS/FTD.
Sujet(s)
Sclérose latérale amyotrophique , Démence frontotemporale , Sclérose latérale amyotrophique/génétique , Animaux , Astrocytes , Protéine C9orf72/génétique , Milieux de culture conditionnés/pharmacologie , Démence frontotemporale/génétique , Humains , Souris , Motoneurones , PolyphosphatesRÉSUMÉ
A growing body of evidence indicates that dietary polyphenols could be used as an early intervention to treat glucose-insulin (G-I) dysregulation. However, studies report heterogeneous information, and the targets of the intervention remain largely elusive. In this work, we provide a general methodology to quantify the effects of any given polyphenol-rich food or formulae over glycemic regulation in a patient-wise manner using an Oral Glucose Tolerance Test (OGTT). We use a mathematical model to represent individual OGTT curves as the coordinated action of subsystems, each one described by a parameter with physiological interpretation. Using the parameter values calculated for a cohort of 1198 individuals, we propose a statistical model to calculate the risk of dysglycemia and the coordination among subsystems for each subject, thus providing a continuous and individual health assessment. This method allows identifying individuals at high risk of dysglycemia-which would have been missed with traditional binary diagnostic methods-enabling early nutritional intervention with a polyphenol-supplemented diet where it is most effective and desirable. Besides, the proposed methodology assesses the effectiveness of interventions over time when applied to the OGTT curves of a treated individual. We illustrate the use of this method in a case study to assess the dose-dependent effects of Delphinol® on reducing dysglycemia risk and improving the coordination between subsystems. Finally, this strategy enables, on the one hand, the use of low-cost, non-invasive methods in population-scale nutritional studies. On the other hand, it will help practitioners assess the effectiveness of an intervention based on individual vulnerabilities and adapt the treatment to manage dysglycemia and avoid its progression into disease.
RÉSUMÉ
In several fields of research, molecular dynamics simulation techniques are exploited to evaluate the temporal motion of particles constituting water, ions, small molecules, macromolecules, or more complex systems over time. These techniques are considered difficult to setup, computationally demanding and require high specialization and scientific skills. Moreover, they need specialized computing infrastructures to run faster and make the simulation of big systems feasible. Here, we have simulated 3 systems of increasing sizes on scientific- and gaming-enabled graphic processing unit (GPU) cards with Amber, GROMACS, and NAMD and measured their performance accounting also for the market prices of the GPU cards where they were run on.
RÉSUMÉ
Sarcopenia is the degenerative loss of muscle mass and strength with aging. Although a role of mitochondrial metabolism in muscle function and in the development of many diseases has been described, the role of mitochondrial topology and dynamics in the process of muscle aging is not fully understood. This work shows a time line of changes in both mitochondrial distribution and skeletal muscle function during mice lifespan. We isolated muscle fibers from flexor digitorum brevis of mice of different ages. A fusion-like phenotype of mitochondria, together with a change in orientation perpendicular to the fiber axis was evident in the Adult group compared to Juvenile and Older groups. Moreover, an increase in the contact area between sarcoplasmic reticulum and mitochondria was evident in the same group. Together with the morphological changes, mitochondrial Ca2+ resting levels were reduced at age 10-14 months and significantly increased in the Older group. This was consistent with a reduced number of mitochondria-to-jSR pairs in the Older group compared to the Juvenile. Our results support the idea of several age-dependent changes in mitochondria that are accentuated in midlife prior to a complete sarcopenic phenotype.
Sujet(s)
Vieillissement/métabolisme , Mitochondries du muscle/métabolisme , Sarcopénie/métabolisme , Réticulum sarcoplasmique/métabolisme , Tissu adipeux/anatomopathologie , Animaux , Calcium/métabolisme , Évolution de la maladie , Souris , Mitochondries du muscle/anatomopathologie , Mitochondries du muscle/ultrastructure , ARN messager/métabolisme , Répartition aléatoire , Réticulum sarcoplasmique/anatomopathologie , Réticulum sarcoplasmique/ultrastructureRÉSUMÉ
Parkinson's disease (PD) is a degenerative disorder characterized by several motor symptoms including shaking, rigidity, slow movement and difficult walking, which has been associated to the death of nigro-striatal dopaminergic neurons. >90% of PD patients also present olfactory dysfunction. Although the molecular mechanisms responsible for this disease are not clear, hereditary PD is linked to mutations in specific genes, including the PTEN-induced putative kinase 1 (PINK1). In this work we provide for the first time a thorough temporal description of the behavioral effects induced by a mutation in the PINK1 gene in adult Drosophila, a previously described animal model for PD. Our data suggests that the motor deficits associated to PD are fully revealed only by the third week of age. However, olfactory dysfunction is detected as early as the first week of age. We also provide immunofluorescence and neurochemical data that let us propose for the first time the idea that compensatory changes occur in this Drosophila model for PD. These compensatory changes are associated to specific components of the dopaminergic system: the biosynthetic enzymes, Tyrosine hydroxylase and Dopa decarboxylase, and the Dopamine transporter, a plasma membrane protein involved in maintaining dopamine extracellular levels at physiologically relevant levels. Thus, our behavioral, immunofluorescence and neurochemical data help define for the first time presymptomatic and symptomatic phases in this PD animal model, and that compensatory changes occur in the dopaminergic neurons in the presymptomatic stage.
Sujet(s)
Comportement animal , Dopamine/métabolisme , Neurones dopaminergiques/métabolisme , Maladie de Parkinson/métabolisme , Animaux , Modèles animaux de maladie humaine , Neurones dopaminergiques/anatomopathologie , Protéines de Drosophila/génétique , Protéines de Drosophila/métabolisme , Drosophila melanogaster , Maladie de Parkinson/génétique , Maladie de Parkinson/anatomopathologie , Maladie de Parkinson/physiopathologie , Protein-Serine-Threonine Kinases/génétique , Protein-Serine-Threonine Kinases/métabolismeRÉSUMÉ
Dendrite arbor growth, or dendritogenesis, is choreographed by a diverse set of cues, including the NMDA receptor (NMDAR) subunits NR2A and NR2B. While NR1NR2B receptors are predominantly expressed in immature neurons and promote plasticity, NR1NR2A receptors are mainly expressed in mature neurons and induce circuit stability. How the different subunits regulate these processes is unclear, but this is likely related to the presence of their distinct C-terminal sequences that couple different signaling proteins. Calcium-calmodulin-dependent protein kinase II (CaMKII) is an interesting candidate as this protein can be activated by calcium influx through NMDARs. CaMKII triggers a series of biochemical signaling cascades, involving the phosphorylation of diverse targets. Among them, the activation of cAMP response element-binding protein (CREB-P) pathway triggers a plasticity-specific transcriptional program through unknown epigenetic mechanisms. Here, we found that dendritogenesis in hippocampal neurons is impaired by several well-characterized constructs (i.e., NR2B-RS/QD) and peptides (i.e., tatCN21) that specifically interfere with the recruitment and interaction of CaMKII with the NR2B C-terminal domain. Interestingly, we found that transduction of NR2AΔIN, a mutant NR2A construct with increased interaction to CaMKII, reactivates dendritogenesis in mature hippocampal neurons in vitro and in vivo. To gain insights into the signaling and epigenetic mechanisms underlying NMDAR-mediated dendritogenesis, we used immunofluorescence staining to detect CREB-P and acetylated lysine 27 of histone H3 (H3K27ac), an activation-associated histone tail mark. In contrast to control mature neurons, our data shows that activation of the NMDAR/CaMKII/ERK-P/CREB-P signaling axis in neurons expressing NR2AΔIN is not correlated with increased nuclear H3K27ac levels.
Sujet(s)
Calcium-Calmodulin-Dependent Protein Kinase Type 2/métabolisme , Protéine de liaison à l'élément de réponse à l'AMP cyclique/métabolisme , Dendrites/enzymologie , Hippocampe/enzymologie , Histone/métabolisme , Neurogenèse , Plasticité neuronale , Récepteurs du N-méthyl-D-aspartate/métabolisme , Acétylation , Animaux , Calcium-Calmodulin-Dependent Protein Kinase Type 2/antagonistes et inhibiteurs , Calcium-Calmodulin-Dependent Protein Kinase Type 2/génétique , Cellules cultivées , Dendrites/effets des médicaments et des substances chimiques , Âge gestationnel , Hippocampe/effets des médicaments et des substances chimiques , Hippocampe/embryologie , Mutation , Neurogenèse/effets des médicaments et des substances chimiques , Plasticité neuronale/effets des médicaments et des substances chimiques , Peptides/pharmacologie , Phénotype , Liaison aux protéines , Motifs et domaines d'intéraction protéique , Inhibiteurs de protéines kinases/pharmacologie , Maturation post-traductionnelle des protéines , Interférence par ARN , Rat Sprague-Dawley , Récepteurs du N-méthyl-D-aspartate/génétique , Transduction du signal , TransfectionRÉSUMÉ
Sarcopenia is the loss of muscle mass accompanied by a decrease in muscle strength and resistance and is the main cause of disability among the elderly. Muscle loss begins long before there is any clear physical impact in the senior adult. Despite all this, the molecular mechanisms underlying muscle aging are far from being understood. Recent studies have identified that not only mitochondrial metabolic dysfunction but also mitochondrial dynamics and mitochondrial calcium uptake could be involved in the degeneration of skeletal muscle mass. Mitochondrial homeostasis influences muscle quality which, in turn, could play a triggering role in signaling of systemic aging. Thus, it has become apparent that mitochondrial status in muscle cells could be a driver of whole body physiology and organismal aging. In the present review, we discuss the existing evidence for the mitochondria related mechanisms underlying the appearance of muscle aging and sarcopenia in flies and mice.
Sujet(s)
Vieillissement , Mitochondries/métabolisme , Muscles squelettiques/métabolisme , Animaux , Calcium/métabolisme , Dynamique mitochondriale , Mitophagie , Force musculaire , Stress oxydatif , Espèces réactives de l'oxygène/métabolismeRÉSUMÉ
The construction and prediction of cell fate maps at the whole embryo level require the establishment of an accurate atlas of gene expression patterns throughout development and the identification of the corresponding cis-regulatory sequences. However, while the expression and regulation of genes encoding upstream developmental regulators such as transcription factors or signaling pathway components have been analyzed in detail, up to date the number of cis-regulatory sequences identified for downstream effector genes, like ion channels, pumps and exchangers, is very low. The control and regulation of ion homeostasis in each cell, including at blastoderm stages, are essential for normal embryonic development. In this study, we analyzed in detail the embryonic expression pattern and cis-regulatory modules of the Drosophila Na+-driven anion exchanger 1 (Ndae1) gene, involved in the regulation of pH homeostasis. We show that Ndae1 is expressed in a tight and complex spatial-temporal pattern. In particular, we report that this downstream effector gene is under the control of the canonical dorsal-ventral patterning cascade through dorsal, Toll, twist and snail at early embryogenesis. Moreover, we identify several cis-regulatory modules, some of which control discrete and non-overlapping aspects of endogenous gene expression throughout development.
Sujet(s)
Antiports/génétique , Protéines de Drosophila/génétique , Drosophila/embryologie , Drosophila/génétique , Embryon non mammalien , Régulation de l'expression des gènes au cours du développement , Animaux , Antiports/métabolisme , Protéines de Drosophila/métabolisme , Développement embryonnaire/génétique , Expression des gènes , Ordre des gènes , Gènes rapporteurs , Locus génétiques , Introns , Mutation , Séquences d'acides nucléiques régulatricesRÉSUMÉ
Rhythmic variations with 24-h periodicity hallmark homeostatic regulation, metabolic processes and organ systems function, driven by a circadian timing system composed of central and peripheral oscillators. Recent reports suggest that disrupted circadian rhythmicity of physiology and behavior severely alters body homeostasis. Nuclear receptors and transcriptional regulators sense hormonal and metabolic cues and manage the rhythmic patterns of chromatin remodelling and gene expression, playing a key role in the cross talk between the circadian clock circuitry, the metabolic pathways and the organ systems. The alteration of this cross talk contributes to the pathophysiology of metabolic, degenerative, immune-related and neoplastic diseases.
Sujet(s)
Horloges circadiennes , Maladie , Santé , Voies et réseaux métaboliques , Animaux , HumainsRÉSUMÉ
Adult tissue stem cells have the ability to adjust to environmental changes and affect also the proliferation of neighboring cells, with important consequences on tissue maintenance and regeneration. Stem cell renewal and proliferation is strongly regulated during aging of the organism. Caloric restriction is the most powerful anti-aging strategy conserved throughout evolution in the animal kingdom. Recent studies relate the properties of caloric restriction to its ability in reprogramming stem-like cell states and in prolonging the capacity of stem cells to self-renew, proliferate, differentiate, and replace cells in several adult tissues. However this general paradigm presents with exceptions. The scope of this review is to highlight how caloric restriction impacts on diverse stem cell compartments and, by doing so, might differentially delay aging in the tissues of lower and higher organisms.
Sujet(s)
Cellules souches adultes/physiologie , Restriction calorique , Vieillissement de la cellule/physiologie , Autophagie/physiologie , Cellules souches hématopoïétiques/physiologie , Humains , Régénération/physiologie , Sirtuine-1/physiologieRÉSUMÉ
The circadian clock machinery orchestrates organism metabolism to ensure that development, survival, and reproduction are attuned to diurnal environmental variations. For unknown reasons, there is a decline in circadian rhythms with age, concomitant with declines in the overall metabolic tissue homeostasis and changes in the feeding behavior of aged organisms. This disruption of the relationship between the clock and the nutrient-sensing networks might underlie age-related diseases; overall, greater knowledge of the molecular mediators of and variations in clock networks during lifespan may shed light on the aging process and how it may be delayed. In this review we address the complex links between the circadian clock, metabolic (dys)functions, and aging in different model organisms.
Sujet(s)
Vieillissement , Horloges circadiennes , Modèles animaux de maladie humaine , Maladies métaboliques/métabolisme , Transduction du signal , Animaux , Restriction calorique , Régime alimentaire/effets indésirables , Métabolisme énergétique , Comportement alimentaire , Humains , Longévité , Maladies métaboliques/prévention et contrôle , Spécificité d'espèceRÉSUMÉ
Under physiological conditions, most neurons keep glycogen synthase (GS) in an inactive form and do not show detectable levels of glycogen. Nevertheless, aberrant glycogen accumulation in neurons is a hallmark of patients suffering from Lafora disease or other polyglucosan disorders. Although these diseases are associated with mutations in genes involved in glycogen metabolism, the role of glycogen accumulation remains elusive. Here, we generated mouse and fly models expressing an active form of GS to force neuronal accumulation of glycogen. We present evidence that the progressive accumulation of glycogen in mouse and Drosophila neurons leads to neuronal loss, locomotion defects and reduced lifespan. Our results highlight glycogen accumulation in neurons as a direct cause of neurodegeneration.
Sujet(s)
Glycogénose/génétique , Glycogen synthase/métabolisme , Glycogène/métabolisme , Maladies neurodégénératives/étiologie , Neurones/enzymologie , Neurones/anatomopathologie , Animaux , Modèles animaux de maladie humaine , Drosophila , Glycogénose/anatomopathologie , Glycogénose/physiopathologie , Glycogen synthase/génétique , Locomotion , Longévité , Souris , Maladies neurodégénératives/génétique , Maladies neurodégénératives/anatomopathologie , Maladies neurodégénératives/physiopathologieRÉSUMÉ
BACKGROUND: The human transcription factors (TFs) GATA4, NKX2.5 and TBX5 form part of the core network necessary to build a human heart and are involved in Congenital Heart Diseases (CHDs). The human natriuretic peptide precursor A (NPPA) and α-myosin heavy chain 6 (MYH6) genes are downstream effectors involved in cardiogenesis that have been demonstrated to be in vitro targets of such TFs. RESULTS: To study the interactions between these human TFs and their target enhancers in vivo, we overexpressed them in the whole Drosophila cardiac tube using the UAS/GAL4 system. We observed that all three TFs up-regulate their natural target enhancers in Drosophila and cause developmental defects when overexpressed in eyes and wings. CONCLUSIONS: A strong potential of the present model might be the development of combinatorial and mutational assays to study the interactions between human TFs and their natural target promoters, which are not easily undertaken in tissue culture cells because of the variability in transfection efficiency, especially when multiple constructs are used. Thus, this novel system could be used to determine in vivo the genetic nature of the human mutant forms of these TFs, setting up a powerful tool to unravel the molecular genetic mechanisms that lead to CHDs.
Sujet(s)
Drosophila melanogaster/génétique , Éléments activateurs (génétique)/génétique , Cardiopathies congénitales/génétique , Facteurs de transcription/métabolisme , Activation de la transcription , Animaux , Animal génétiquement modifié , Drosophila melanogaster/métabolisme , Régulation de l'expression des gènes au cours du développement , Coeur/embryologie , Humains , Organogenèse/physiologie , Protéines de fusion recombinantes/génétique , Protéines de fusion recombinantes/métabolisme , Facteurs de transcription/génétiqueRÉSUMÉ
A functional organ is constituted of diverse cell types. Each one occupies a distinct position and is associated to specific morphological and physiological functions. The identification of the genetic programs controlling these elaborated and highly precise features of organogenesis is crucial to understand how a mature organ works under normal conditions, and how pathologies can develop. Recently, a number of studies have reported a critical role for Hox genes in one example of organogenesis: cardiogenesis in Drosophila. Beyond the interest in understanding the molecular basis of functional cardiogenesis, this system might provide a model for proposing new paradigms of how Hox genes achieve their action throughout development.