75 research outputs found
Three-Dimensional Reconstruction of Foot in the Weightbearing Position From Biplanar Radiographs: Evaluation of Accuracy and Reliability
The initial assessment and postoperative monitoring of patients with various abnormalities of the foot in clinical routine practice is primarily based on the analysis of radiographs taken in the weightbearing position. Conventional x-ray imaging, however, only provides a 2-dimensional projection of 3-dimensional (3D) bony structures, and the clinical parameters assessed from these images can be affected by projection biases. In the present work, we addressed this issue by proposing an accurate 3D reconstruction method of the foot in the weightbearing position from low-dose biplanar radiographs with clinical index measurement assessment for clinical routine practice. The accuracy of the proposed reconstruction method was evaluated for both shape and clinical indexes by comparing 3D reconstructions of 6 cadaveric adult feet from computed tomographic images and from biplanar radiographs. For the reproducibility study, 3D reconstructions from the biplanar radiographs of the foot of 6 able-bodied subjects were considered, with 2 observers repeating each measurement of anatomic landmarks 3 times. Baseline assessment of important 3D clinical parameters was performed on 17 subjects (34 feet; mean age 27.7, range 20 to 52 years). The average point to surface distance between the 3D stereoradiographic reconstruction and the computed tomographic scan-based reconstruction was 1âmm (range 0mm to 6mm). The selected radiographic landmarks were highly reproducible (95% confidence intervalâ<2.0âmm). The greatest interindividual variability for the clinical parameters was observed for the twisting angle (mean 87°, range 73° to 100°). Such an approach opens the way for routine 3D quantitative analysis of the foot in the weightbearing position.The authors thank the ParisTech BiomecAM chair program on subject-specific musculoskeletal modeling, and in particular COVEA and SociĂ©tĂ© GĂ©nĂ©rale. The authors also thank Audrey Arts, Roxane Huet, and Thomas Joubert for their kind technical assistance
Abnormal splicing switch of DMD's penultimate exon compromises muscle fibre maintenance in myotonic dystrophy
International audienceMyotonic Dystrophy type 1 (DM1) is a dominant neuromuscular disease caused by nuclear-retained RNAs containing expanded CUG repeats. These toxic RNAs alter the activities of RNA splicing factors resulting in alternative splicing misregulation and muscular dysfunction. Here we show that the abnormal splicing of DMD exon 78 found in dystrophic muscles of DM1 patients is due to the functional loss of MBNL1 and leads to the re-expression of an embryonic dystrophin in place of the adult isoform. Forced expression of embryonic dystrophin in zebrafish using an exon-skipping approach severely impairs the mobility and muscle architecture. Moreover, reproducing Dmd exon 78 missplicing switch in mice induces muscle fibre remodelling and ultrastructural abnormalities including ringed fibres, sarcoplasmic masses or Z-band disorganization, which are characteristic features of dystrophic DM1 skeletal muscles. Thus, we propose that splicing misregulation of DMD exon 78 compromises muscle fibre maintenance and contributes to the progressive dystrophic process in DM
Study of collagen VI during the zebrafish muscle development : implications for COLVI-related myopathies
Les muscles sont des structures trĂšs organisĂ©es qui nous permettent dâeffectuer un grand nombre de fonctions. Ils sont constituĂ©s de cellules musculaires mais aussi de tissus conjonctifs qui comprennent Ă la fois des cellules et la matrice extracellulaire. Les interactions entre les cellules musculaires et le tissu conjonctif sont cruciales pour la physiologie du muscle. Le collagĂšne VI (COLVI) est une molĂ©cule hĂ©tĂ©rotrimĂ©rique ubiquitaire situĂ©e dans les tissus conjonctifs, qui est impliquĂ©e dans un grand nombre de processus biologiques. Les trimĂšres de COLVI sont composĂ©s de 2 chaines dites âcourtesâ et dâune chaine âlongueâ. Chez les mammifĂšres, il existe Ă ce jour, 6 chaines COLVI (deux courtes (α1-2(VI) et 4 chaines longues (α3-6(VI)). Peu de choses sont encore connues Ă propos de lâassemblage des chaines les plus rĂ©cemment dĂ©crites α4-6(VI) avec les chaines courtes ainsi quâune la potentielle compensation entre les diffĂ©rentes chaines longues. De plus, chez lâhomme, un dĂ©ficit en α1-3(VI) du fait de mutations dans les gĂšnes correspondants COL6A1-3 conduit Ă un spectre de maladies neuromusculaires appelĂ©es myopathies liĂ©es au COLVI. Pendant ma thĂšse, je me suis intĂ©ressĂ©e au COLVI durant le dĂ©veloppement du poisson-zĂšbre, un modĂšle pertinent pour lâĂ©tude de maladies neuromusculaires. Dans la premiĂšre partie de mon travail, jâai identifiĂ© 2 orthologues des chaines α4-6(VI) chez le poisson-zĂšbre grĂące Ă des Ă©tudes bio-informatiques. Du fait de leur plus grande homologie avec la chaine α4(VI) murine, nous les avons nommĂ©s col6a4a et col6a4b. Pour mieux comprendre les rĂŽles des protĂ©ines correspondantes, jâai crĂ©Ă© des embryons de poissons-zĂšbres dĂ©ficients en COLVI en utilisant lâapproche transitoire par oligo morpholino antisens (MOs). Nous avons dessinĂ© des MOs ciblant des sites dâĂ©pissage des prĂ©-messagers col6a2, col6a4a et col6a4b, provoquant un saut dâexon et conduisant Ă un stop prĂ©maturĂ© (PTC). Jâai observĂ© une forte diminution des transcrits ciblĂ©s. Tous les embryons injectĂ©s (morphants) ont prĂ©sentĂ© des phĂ©notypes morphologiques macroscopiques qui ont conduit Ă des dĂ©fauts fonctionnels. Ces phĂ©notypes ont Ă©tĂ© confirmĂ©s au niveau ultra-structural par microscopie Ă©lectronique. Toutefois, lâanalyse de la croissance des motoneurones a permis de mettre en Ă©vidence des diffĂ©rences entre ces morphants. Par la suite, jâai voulu crĂ©er deux types de lignĂ©es transgĂ©niques, pour pouvoir Ă la fois Ă©tudier le dĂ©ficit en COLVI Ă plus long terme (grĂące Ă lâutilisation de Zinc Finger Nucleases) et tester des approches de cribles pharmacologiques (lignĂ©e transgĂ©nique col6a2 contenant un PTC, fusionnĂ© Ă la GFP). Jâai effectuĂ© les clonages nĂ©cessaires Ă lâobtention des diffĂ©rentes constructions, et ces derniĂšres ont Ă©tĂ© testĂ©es in vitro pour validation, lorsque cela Ă©tait possible. Malheureusement, du fait des forts taux de mortalitĂ© in vivo dans les deux cas, nous avons dĂ» nous rĂ©soudre Ă arrĂȘter ces projets. En parallĂšle, ma connaissance du modĂšle poisson-zĂšbre mâa donnĂ© lâopportunitĂ©, dans le cadre dâune collaboration avec lâĂ©quipe de Denis Furling, dâaborder une autre problĂ©matique. Ce groupe, qui travaille sur la Dystrophie Myotonique de type 1 (DM1), sâest intĂ©ressĂ© Ă la rĂ©expression dâune isoforme fĆtale de la dystrophine retrouvĂ©e chez les patients DM1 et Ă sa possible implication dans la pathologie. Lâisoforme fĆtale diffĂšre de la forme adulte notamment par lâexclusion de lâexon 78, conduisant Ă un changement de cadre de lecture et un changement dans la partie 3â de lâARN de la dystrophine. Nous avons montrĂ© que le maintien de lâisoforme fĆtale de la dystrophine Ă©tait dĂ©lĂ©tĂšre pendant le dĂ©veloppement du poisson-zĂšbre, puisque ces embryons ont prĂ©sentĂ© un phĂ©notype macroscopique dĂ©pendant de la dose de MO injectĂ©e ainsi que des troubles de la mobilitĂ©.Muscles are highly organized structures that allow us to perform many functions. They are made from muscular cells but also surrounding tissues that comprise both cells and extracellular matrix. The interactions between them are crucial for the muscle physiology. Collagen VI (COLVI) is a heterotrimeric protein, ubiquitously expressed in connective tissues. It plays multiple biological roles in the maintenance of structural integrity, cellular adhesion, migration and survival. COLVI trimers are formed by the assembly of 2 âshortâ chains and 1 âlongâ chain. To date, six COLVI chains are recognized in mammalians with 2 short (α1-2(VI)) and 3 long (α3-6(VI)) chains. Little is known regarding the possible assembly of the newly characterized α4-6(VI) polypeptides with the short chains, and a putative functional compensation between the different long chains. Furthermore, in humans, deficiency in α1-3(VI) due to mutations in the COL6A1-3 genes causes a heterogeneous group of neuromuscular disorders collectively termed COLVI-myopathies. During my Ph.D, I got interested in COLVI during the development of zebrafish, a relevant model of neuromuscular disorders. In the first part of my work, I identified 2 orthologs of the α4-6(VI) chains in zebrafish thanks to bio-informatics studies. In light of their stronger homology with the mammalian α4(VI) chain, we named the genes encoding the novel chains col6a4a and col6a4b. To further unveil the roles of the corresponding proteins, we created COLVI deficient zebrafish embryos using a morpholino antisense oligonucleotides approach (MO) . We chose to design MOs that block splicing of col6a2, col6a4a and col6a4b, thereby creating premature termination codons. As expected, the targeted transcripts levels were drastically reduced, likely due to degradation by the nonsense mediated RNA decay. All morphant embryos presented macroscopic and morphologic phenotypes that overall resulted in functional muscle defects: altered muscle structure detected by birefringence analysis and impaired motility upon touch-evoked escape test. These alterations were confirmed at the ultra-structural level by electron microscopy. Nevertheless, some phenotypical specificities were uncovered between the different col6a2, col6a4a and col6a4b morphants, with the discovery of axon outgrowth defects. In a second part, we wanted to create stable zebrafish lines to study COLVI deficiency at later stages using Zinc Finger Nucleases (ZFN) and to be able to carry out pharmacological screenings with a transgenic line containing col6a2 with a premature codon (PTC) fused to the GFP. I performed clonings to obtain the different constructs. When possible, constructs were tested in vitro. Unfortunately, due to high mortality in vivo in both cases, we had to interrupt these projects. In parallel, my knowledge of the zebrafish model gave me the opportunity to be part of another project, in collaboration with the team of Denis Furling..
Synthesis of novel fluorocarbon-therapeutic peptide conjugates to increase the metabolic stability of GPCRs ligands : application to apeline and spexin, mechanism study and biological evaluation
Les peptides prĂ©sentent un fort potentiel thĂ©rapeutique. En revanche, leur faible stabilitĂ© dans lâorganismerend leur Ă©tude et leu r dĂ©veloppement difficiles. Afin dâamĂ©liorer la stabilitĂ© plasmatique de peptides, il aĂ©tĂ© dĂ©veloppĂ© au laboratoire une nouvelle stratĂ©gie qui consiste en lâintroduction dâune chainefluorocarbonĂ©e dans la sĂ©quence dâun peptide. Au cours de ce travail de thĂšse, nous avons Ă©tudiĂ© lesmĂ©canismes conduisant Ă cette augmentation de stabilitĂ© dans le cas de lâapeline, un peptide possĂ©dant unintĂ©rĂȘt potentiel pour le traitement des maladies cardiovasculaires. Cette stratĂ©gie de stabilisation aĂ©galement Ă©tĂ© appliquĂ©e Ă la spexine, peptide ayant des propriĂ©tĂ©s analgĂ©siques intĂ©ressantes. Ainsi, desĂ©tudes de relations structure-activitĂ© autour de ces peptides ont permis de montrer lâimportance de lalongueur et de la nature de la chaine fluorocarbonĂ©e. Ce travail a Ă©galement permis de concevoir de nouveauxdĂ©rivĂ©s biocompatibles Ă fort potentiel thĂ©rapeutique. Nous avons Ă©galement dĂ©veloppĂ© une stratĂ©gieoriginale de synthĂšse des fluoro-peptides en solution par une rĂ©action de bioconjugaison.Peptide are macromolecules presenting a high therapeutic potential. The main limitation for their study anddevelopment as therapeutics is their low plasma stability. In order to increase therapeutic peptidesâ stability,a novel strategy based on the incorporation of a fluorocarbon chain into the peptideâs sequence has beendeveloped in the laboratory. During this thesis, we studied the mechanism leading to this stability on a modelpeptide involved in cardiovascular diseases: apeline-17. This method has also been applied to spexine, apromising peptide in pain regulation. Structure-activity relationship studies on those two peptides showed theimportance of the fluorocarbon chain length and its nature. These studies allowed the development of newbiocompatible fluoro-peptides showing a high therapeutic potential. We also developed an original solutionphase fluoro-peptide synthesis strategy using a bioconjugation reaction fluoro-peptide synthesis strategy
Synthesis of novel fluorocarbon-therapeutic peptide conjugates to increase the metabolic stability of GPCRs ligands : application to apeline and spexin, mechanism study and biological evaluation
Les peptides prĂ©sentent un fort potentiel thĂ©rapeutique. En revanche, leur faible stabilitĂ© dans lâorganismerend leur Ă©tude et leu r dĂ©veloppement difficiles. Afin dâamĂ©liorer la stabilitĂ© plasmatique de peptides, il aĂ©tĂ© dĂ©veloppĂ© au laboratoire une nouvelle stratĂ©gie qui consiste en lâintroduction dâune chainefluorocarbonĂ©e dans la sĂ©quence dâun peptide. Au cours de ce travail de thĂšse, nous avons Ă©tudiĂ© lesmĂ©canismes conduisant Ă cette augmentation de stabilitĂ© dans le cas de lâapeline, un peptide possĂ©dant unintĂ©rĂȘt potentiel pour le traitement des maladies cardiovasculaires. Cette stratĂ©gie de stabilisation aĂ©galement Ă©tĂ© appliquĂ©e Ă la spexine, peptide ayant des propriĂ©tĂ©s analgĂ©siques intĂ©ressantes. Ainsi, desĂ©tudes de relations structure-activitĂ© autour de ces peptides ont permis de montrer lâimportance de lalongueur et de la nature de la chaine fluorocarbonĂ©e. Ce travail a Ă©galement permis de concevoir de nouveauxdĂ©rivĂ©s biocompatibles Ă fort potentiel thĂ©rapeutique. Nous avons Ă©galement dĂ©veloppĂ© une stratĂ©gieoriginale de synthĂšse des fluoro-peptides en solution par une rĂ©action de bioconjugaison.Peptide are macromolecules presenting a high therapeutic potential. The main limitation for their study anddevelopment as therapeutics is their low plasma stability. In order to increase therapeutic peptidesâ stability,a novel strategy based on the incorporation of a fluorocarbon chain into the peptideâs sequence has beendeveloped in the laboratory. During this thesis, we studied the mechanism leading to this stability on a modelpeptide involved in cardiovascular diseases: apeline-17. This method has also been applied to spexine, apromising peptide in pain regulation. Structure-activity relationship studies on those two peptides showed theimportance of the fluorocarbon chain length and its nature. These studies allowed the development of newbiocompatible fluoro-peptides showing a high therapeutic potential. We also developed an original solutionphase fluoro-peptide synthesis strategy using a bioconjugation reaction fluoro-peptide synthesis strategy
HRP-labeled debris are presynaptically derived.
<p>Composite confocal images correspond to 6 h APF pupae. <b>A-C</b>, The anti-HRP labeled puncta (grey, blue in the merge) colocalized with anti-FASII (red) (arrowheads). <b>D-F</b>, <i>UAS-mCD8-GFP</i> (green) was driven in motor neurons with <i>OK6-GAL4</i>. Most of the anti-HRP labeled debris (red) were GFP-positive (arrowheads). <b>G-I</b>, The anti-HRP labeled puncta (grey, blue in the merge) colocalized with CSP (red) (arrowheads). Note the pink color in the merge marked by arrowheads in C and I. <b>J-L</b>, The HRP-positive puncta (grey, blue in the merge) did not co-localize with D-GluRIIC (red), (arrow in J and L). The inset in L shows a high magnification (2Ă). Bars, 20 ”m. Genotypes: (A-C, G-L) <i>MHC-mGFP-Shaker</i>, (D-F) <i>OK6-GAL4/2ĂUAS-mGFP.</i></p
<em>Drosophila</em> Motor Neuron Retraction during Metamorphosis Is Mediated by Inputs from TGF-ÎČ/BMP Signaling and Orphan Nuclear Receptors
<div><p>Larval motor neurons remodel during <em>Drosophila</em> neuro-muscular junction dismantling at metamorphosis. In this study, we describe the motor neuron retraction as opposed to degeneration based on the early disappearance of ÎČ-Spectrin and the continuing presence of Tubulin. By blocking cell dynamics with a dominant-negative form of Dynamin, we show that phagocytes have a key role in this process. Importantly, we show the presence of peripheral glial cells close to the neuro-muscular junction that retracts before the motor neuron. We show also that in muscle, expression of <em>EcR-B1</em> encoding the steroid hormone receptor required for postsynaptic dismantling, is under the control of the <em>ftz-f1/Hr39</em> orphan nuclear receptor pathway but not the TGF-ÎČ signaling pathway. In the motor neuron, activation of <em>EcR-B1</em> expression by the two parallel pathways (TGF-ÎČ signaling and nuclear receptor) triggers axon retraction. We propose that a signal from a TGF-ÎČ family ligand is produced by the dismantling muscle (postsynapse compartment) and received by the motor neuron (presynaptic compartment) resulting in motor neuron retraction. The requirement of the two pathways in the motor neuron provides a molecular explanation for the instructive role of the postsynapse degradation on motor neuron retraction. This mechanism insures the temporality of the two processes and prevents motor neuron pruning before postsynaptic degradation.</p> </div
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