Articles

The tetraspanin CD9 controls migration and proliferation of parietal epithelial cells and glomerular disease progression
- Lazareth Hélène
- Henique Carole
- Lenoir Olivia
- Puelles Victor
- Flamant Martin
- Bollée Guillaume
- Fligny Cécile
- Camus Marine
- Guyonnet Léa
- Millien Corinne
- Gaillard François
- Chipont Anna
- Robin Blaise
- Fabrega Sylvie
- Dhaun Neeraj
- Camerer Eric
- Kretz Oliver
- Grahammer Florian F.
- Braun Fabian
- Huber Tobias
- Nochy Dominique
- Mandet Chantal
- Bruneval Patrick
- Mesnard Laurent
- Thervet Eric
- Karras Alexandre
- Le Naour François
- Rubinstein Eric
- Boucheix Claude
- Alexandrou Antigoni
- Moeller Marcus
- Bouzigues Cedric
- Tharaux Pierre-Louis
Nature Communications, Nature Publishing Group , 2019, 10 (1), pp.3303 . The mechanisms driving the development of extracapillary lesions in focal segmental glomerulosclerosis (FSGS) and crescentic glomerulonephritis (CGN) remain poorly understood. A key question is how parietal epithelial cells (PECs) invade glomerular capillaries, thereby promoting injury and kidney failure. Here we show that expression of the tetraspanin CD9 increases markedly in PECs in mouse models of CGN and FSGS, and in kidneys from individuals diagnosed with these diseases. Cd9 gene targeting in PECs prevents glomerular damage in CGN and FSGS mouse models. Mechanistically, CD9 deficiency prevents the oriented migration of PECs into the glomerular tuft and their acquisition of CD44 and β1 integrin expression. These findings highlight a critical role for de novo expression of CD9 as a common pathogenic switch driving the PEC phenotype in CGN and FSGS, while offering a potential therapeutic avenue to treat these conditions. (10.1038/s41467-019-11013-2)
DOI : 10.1038/s41467-019-11013-2
Maturation of the Meniscal Collagen Structure Revealed by Polarization-Resolved and Directional Second Harmonic Generation Microscopy
- Pinsard Maxime
- Laverty Sheila
- Richard Hélène
- Dubuc Julia
- Schanne-Klein Marie-Claire
- Légaré François
Scientific Reports, Nature Publishing Group , 2019, 9 . We report polarization-resolved Second Harmonic Generation (p-SHG) and directional SHG (forward and backward, F/B) measurements of equine foetal and adult collagen in meniscus, over large field-of-views using sample-scanning. Large differences of collagen structure and fibril orientation with maturation are revealed, validating the potential for this novel methodology to track such changes in meniscal structure. The foetal menisci had a non-organized and more random collagen fibrillar structure when compared with adult using P-SHG. For the latter, clusters of homogeneous fibril orientation (inter-fibrillar areas) were revealed, separated by thick fibers. F/B SHG showed numerous different features in adults notably, in thick fibers compared to interfibrillar areas, unlike foetal menisci that showed similar patterns for both directions. This work confirms previous studies and improves the understanding of meniscal collagen structure and its maturation, and makes f/B and p-SHG good candidates for future studies aiming at revealing structural modifications to meniscus due to pathologies. The meniscus is a semilunar fibrocartilaginous structure interposed between the femoral condyle and the tibial plateau in the knee joint. The meniscus is essential for load transmission across the articular surfaces, for femo-rotibial joint stability and for long-term joint health 1. Degradation of the meniscal tissue can increase articular cartilage strain 2 , and may lead to cartilage degeneration and osteoarthritis 3. Knowledge of the complex structure of the meniscal extracellular matrix (ECM) has increased thanks to emerging technologies for in situ imaging of intact specimens, such as Optical Projection Tomography (OPT) 4. In particular the arrangement of meniscal fascicles 4 , its tie-fiber organization 5 , and the menisco-tibial ligament insertion transition have all recently been revealed by investigation of bovine samples 6. SHG microscopy is a recent and powerful technique to image the structure of biological specimens as it provides submicron spatial resolution, has low phototoxicity and a high depth selectivity and penetration. In this respect, SHG imaging is similar to multiphoton-excited fluorescence microscopy 7. However, important differences exist: it is a coherent process sensitive to the phase-matching conditions where the measured signal arises from constructive/destructive interferences, it is also instantaneous and free from photobleaching as the signal conversion is due to a structural arrangement and does not involve electronic transition 8. SHG micros-copy has been used to image fibrillar collagen in specimens including type II collagen in articular cartilage 9-16. Furthermore, because of its coherent nature, the detection of the signal in the direction of propagation (forward-F) provides different imaging features compared to the backward (B) direction 17. The F/B ratio increases with the level of homogeneity of noncentrosymmetric structures within the focal volume and has been related to the size of the collagen fibrils for collagen rich tissues 18,19 . (10.1038/s41598-019-54942-0)
DOI : 10.1038/s41598-019-54942-0
T-jump and circular dichroism: folding dynamics in proteins and DNA
- Changenet Pascale
- Hache François
Molecular Crystals and Liquid Crystals, Taylor & Francis , 2019, 693 (1), pp.49-56 . We review recent experimental work combining circular dichroism spectroscopy and T-jump experiment to investigate elementary dynamics in the folding/unfolding of biomolecules. A nanosecond setup is presented for poly(Glutamic acid) studies whereas a millisecond one is developed for investigation of DNA G-quadruplex dynamics. (10.1080/15421406.2020.1723918)
DOI : 10.1080/15421406.2020.1723918
Comprehensive Study of Guanine Excited State Relaxation and Photoreactivity in G-quadruplexes
- Martinez-Fernandez Lara
- Changenet Pascale
- Banyasz Akos
- Gustavsson Thomas
- Markovitsi Dimitra
- Improta Roberto
Journal of Physical Chemistry Letters, American Chemical Society , 2019, 10 (21), pp.6873-6877 . G-quadruplexes (G4) are four-stranded DNA/RNA structures playing a key role in many biological functions and promising for nanotechnology applications. Here, combining theoretical calculations and multiscale time-resolved fluorescence, we describe, for the first time, an ensemble of photoactivated processes involving the guanines of the G4 core. We use as showcase the G4 formed by the human telomeric sequence GGG(TTAGGG)3 in the presence of Na+ ions. According to quantum mechanical/molecular mechanics calculations, the hyperchromism at the red part of the absorption spectrum, typical of G4 structures, arises mainly from the inner Na+ ions. Various relaxation pathways, leading to excited states localized on individual bases, neutral excimers, and excited charge transfer states between two guanines or a guanine and a thymine in the loop, are mapped. Their fingerprints are detected in the fluorescence anisotropies and the fluorescence decays, spanning five decades of time. Finally, a reaction funnel leading to guanine dimerization is identified. (10.1021/acs.jpclett.9b02740)
DOI : 10.1021/acs.jpclett.9b02740
Raman Tweezers Microspectroscopy of Functionalized 4.2 nm Diameter CdSe Nanocrystals in Water Reveals Changed Ligand Vibrational Modes by a Metal Cation
- Mrad Randa
- Kruglik Sergei G
- Ben Brahim Nassim
- Ben Chaâbane Rafik
- Négrerie Michel
Journal of Physical Chemistry C, American Chemical Society , 2019, 123 (40), pp.24912 - 24918 . We demonstrated the possibility of acquiring Raman spectra of colloidal quantum dots (QDs) at low concentration in water with a size as small as 2.5 nm in diameter using Raman tweezers microspectroscopy. We measured the spectra of CdSe QDs capped with thioglycerol and with L-cysteine. This technique was applied to probe the interaction between Co 2+ and Cys-CdSe QDs whose fluorescence emission is quenched in the presence of this metal cation. The quenching mechanism was so far hypothetical. The Raman spectra of Cys-CdSe QDs recorded in the absence and in the presence of Co 2+ demonstrated the binding of Co 2+ cations to the carboxylate groups of the L-cysteine ligand grafted on the surface of the 4.2 nm CdSe QDs. The frequency of modes for the grafted ligand is changed with respect to the free ligand in solution. Considering the vibrational coupling between the excitonic state and the ligand, we inferred that the binding of a metal cation to the grafted ligand modifies this coupling, so that exciton relaxation through crystal defects is favored. This result rationalizes the fluorescence quenching observed during the metal cation-QD interaction. (10.1021/acs.jpcc.9b06756)
DOI : 10.1021/acs.jpcc.9b06756
Interaction of the Full-Length Heme-Based CO Sensor Protein RcoM-2 with Ligands
- Salman Mayla
- Villamil Franco Carolina
- Ramodiharilafy Rivo
- Liebl Ursula
- Vos Marten H.
Biochemistry, American Chemical Society , 2019, 58 (39), pp.4028-4034 . (10.1021/acs.biochem.9b00623)
DOI : 10.1021/acs.biochem.9b00623
Diversity of circular RNAs and RNA ligases in archaeal cells
- Becker Hubert F
- L'Hermitte-Stead Caroline
- Myllykallio Hannu
Biochimie, Elsevier , 2019, 164, pp.37-44 . (10.1016/j.biochi.2019.06.011)
DOI : 10.1016/j.biochi.2019.06.011
Quantitative measures of corneal transparency, derived from objective analysis of depth-resolved corneal images, demonstrated with full-field optical coherence tomographic microscopy
- Bocheux Romain
- Pernot Pascal
- Borderie Vincent
- Plamann Karsten
- Irsch Kristina
PLoS ONE, Public Library of Science , 2019, 14 (8), pp.e0221707 . Loss of corneal transparency, as occurs with various pathologies, infections, immune reactions, trauma, aging, and surgery, is a major cause of visual handicap worldwide. However, current means to assess corneal transparency are extremely limited and clinical and eye-bank practice usually involve a subjective and qualitative observation of opacities, sometimes with comparison against an arbitrary grading scale, by means of slit-lamp biomicroscopy. Here, we describe a novel objective optical data analysis-based method that enables quantifiable and standardized characterization of corneal transparency from depth-resolved corneal images, addressing the demand for such a means in both the laboratory and clinical ophthalmology setting. Our approach is based on a mathematical analysis of the acquired optical data with respect to the light attenuation from scattering processes in the corneal stroma. Applicable to any depth-resolved corneal imaging modality, it has been validated by means of full-field optical coherence tomographic microscopy (FF-OCT or FF-OCM). Specifically, our results on ex-vivo corneal specimens illustrate that 1) in homogeneous tissues, characterized by an exponential light attenuation with stromal depth (z), the computation of the scattering mean-free path (ls) from the rate of exponential decay allows quantification of the degree of transparency; 2) in heterogeneous tissues, identified by significant deviations from the normal exponential z -profile, a measure of exponential-decay model inadequacy (e.g., by computation of the Birge ratio) allows the estimation of severity of stromal heterogeneity, and the associated depth-dependent variations around the average ls enables precise localization of the pathology. (10.1371/journal.pone.0221707)
DOI : 10.1371/journal.pone.0221707
Elimination of imaging artifacts in second harmonic generation microscopy using interferometry
- Pinsard Maxime
- Schmeltz Margaux
- van Der Kolk Jarno
- Patten Shunmoogum A.
- Ibrahim Heide
- Ramunno Lora
- Schanne-Klein Marie-Claire
- Légaré François
Biomedical optics express, Optical Society of America - OSA Publishing , 2019, 10 (8), pp.3938-3952 . Conventional second harmonic generation (SHG) microscopy might not clearly reveal the structure of complex samples if the interference between all scatterers in the focal volume results in artefactual patterns. We report here the use of interferometric second harmonic generation (I-SHG) microscopy to efficiently remove these artifacts from SHG images. Interfaces between two regions of opposite polarity are considered because they are known to produce imaging artifacts in muscle for instance. As a model system, such interfaces are first studied in periodically-poled lithium niobate (PPLN), where an artefactual incoherent SH signal is obtained because of irregularities at the interfaces, that overshadow the sought-after coherent contribution. Using I-SHG allows to remove the incoherent part completely without any spatial filtering. Second, I-SHG is also proven to resolve the doubleband pattern expected in muscle where standard SHG exhibits in some regions artefactual single-band patterns. In addition to removing the artifacts at the interfaces between antiparallel domains in both structures (PPLN and muscle), I-SHG also increases their visibility by up to a factor of 5. This demonstrates that I-SHG is a powerful technique to image biological samples at enhanced contrast while suppressing artifacts. (10.1364/BOE.10.003938)
DOI : 10.1364/BOE.10.003938
From observing to predicting single-cell structure and function with high-throughput/high-content microscopy
- Chessel Anatole
- Carazo Salas Rafael
Essays in Biochemistry, Portland Press , 2019, 63 (2), pp.197-208 . Abstract In the past 15 years, cell-based microscopy has evolved its focus from observing cell function to aiming to predict it. In particular—powered by breakthroughs in computer vision, large-scale image analysis and machine learning—high-throughput and high-content microscopy imaging have enabled to uniquely harness single-cell information to systematically discover and annotate genes and regulatory pathways, uncover systems-level interactions and causal links between cellular processes, and begin to clarify and predict causal cellular behaviour and decision making. Here we review these developments, discuss emerging trends in the field, and describe how single-cell ‘omics and single-cell microscopy are imminently in an intersecting trajectory. The marriage of these two fields will make possible an unprecedented understanding of cell and tissue behaviour and function. (10.1042/EBC20180044)
DOI : 10.1042/EBC20180044
Short‐Lived Radical Intermediates in the Photochemistry of Glucose Oxidase
- Nag Lipsa
- Lukacs Andras
- Vos Marten H.
ChemPhysChem, Wiley-VCH Verlag , 2019, 20 (14), pp.1793-1798 . Glucose oxidase is a flavoprotein that is relatively wellstudied as a physico-chemical model system. The flavin cofactor is surrounded by several aromatic acid residues that can act as direct and indirect electron donors to photoexcited flavin. Yet, the identity of the photochemical product states is not well established. We present a detailed full spectral reinvestigation of this issue using femtosecond fluorescence and absorption spectroscopy. Based on a recent characterization of the unstable tyrosine cation radical TyrOH •+ , we now propose that the primary photoproduct involves this species, which was previously not considered. Formation of this product is followed by competing charge recombination and radical pair stabilization reactions that involve proton transfer and radical transfer to tryptophan. A minimal kinetic model is proposed, including a fraction of TyrOH •+ that is stabilized up to the tens of picoseconds timescale, suggesting a potential role of this species as intermediate in biochemical electron transfer reactions. (10.1002/cphc.201900329)
DOI : 10.1002/cphc.201900329
Unveiling excited-state chirality of ninaphthols by femtosecond circular dichroism and quantum chemical calculations
- Schmid Marco
- Martinez-Fernandez Lara
- Markovitsi Dimitra
- Santoro Fabrizio
- Hache François
- Improta Roberto
- Changenet Pascale
Journal of Physical Chemistry Letters, American Chemical Society , 2019, 10 (14), pp.4089-4094 . Time-resolved circular dichroism (TR-CD) is a powerful tool for probing conformational dynamics of biomolecules over large time scales that are crucial for establishing their structure−function relationship. However, such experiments, notably in the femtosecond regime, remain challenging due to their extremely weak signals, prone to polarization artifacts. By using binol and two bridged derivatives (PL1 and PL2) as chiral prototypes, we present here the first comprehensive study of this type in the middle UV, combining femtosecond TR-CD and quantum mechanical calculations (TD-DFT). We show that excitation of the three compounds induces large variations of their transient CD signals, in sharp contrast to those of their achiral transient absorption. We demonstrate that these variations arise from both the alteration of the electronic distribution and the dihedral angle in the excited state. These results highlight the great sensitivity of TR-CD detection to signals hardly accessible to achiral transient absorption. (10.1021/acs.jpclett.9b00948)
DOI : 10.1021/acs.jpclett.9b00948
Publisher correction: Multicolor multiscale brain imaging with chromatic multiphoton serial microscopy
- Abdeladim Lamiae
- Matho Katherine S
- Clavreul Solène
- Mahou Pierre
- Sintes Jean-Marc
- Solinas Xavier
- Arganda-Carreras Ignacio
- Turney Stephen G
- Lichtman Jeff W
- Chessel Anatole
- Bemelmans Alexis-Pierre
- Loulier Karine
- Supatto Willy
- Livet Jean
- Beaurepaire Emmanuel
Nature Communications, Nature Publishing Group , 2019, 10, pp.2160 . Affiliation 4 incorrectly read 'University of the Basque Country (Ikerbasque), University of the Basque Country and Donostia International Physics Center, San Sebastian 20018, Spain.'Also, the affiliations of Ignacio Arganda-Carreras with 'IKERBASQUE, Basque Foundation for Science, Bilbao, 48013, Spain' and 'Donostia International Physics Center (DIPC), San Sebastian, 20018, Spain' were inadvertently omitted.Additionally, the third sentence of the first paragraph of the Results section entitled 'Multicontrast organ-scale imaging with ChroMS microscopy' incorrectly read 'For example, one can choose lambda1 = 850 and lambda2 = 110 nm for optimal two-photon excitation of blue and red chromophores.'. The correct version reads 'lambda2 = 1100 nm' instead of 'lambda2 = 110 nm'. These errors have now been corrected in the PDF and HTML versions of the Article. (10.1038/s41467-019-10225-w)
DOI : 10.1038/s41467-019-10225-w
Iron transitions during activation of allosteric heme proteins in cell signaling
- Négrerie Michel
Metallomics, Royal Society of Chemistry , 2019, 11, pp.868 - 893 . Allosteric heme proteins can fulfill a very large number of different functions thanks to the remarkable chemical versatility of heme through the entire living kingdom. Their efficacy resides in the ability of heme to transmit both iron coordination changes and iron redox state changes to the protein structure. Besides the properties of iron, proteins may impose a particular heme geometry leading to distortion, which allows selection or modulation of the electronic properties of heme. This review focusses on the mechanisms of allosteric protein activation triggered by heme coordination changes following diatomic binding to proteins as diverse as the human NO-receptor, cytochromes, NO-transporters and sensors, and a heme-activated potassium channel. It describes at the molecular level the chemical capabilities of heme to achieve very different tasks and emphasizes how the properties of heme are determined by the protein structure. Particularly, this reviews aims at giving an overview of the exquisite adaptability of heme, from bacteria to mammals. (10.1039/c8mt00337h)
DOI : 10.1039/c8mt00337h
High-speed polarization-resolved third-harmonic microscopy
- Morizet Joséphine
- Ducourthial Guillaume
- Supatto Willy
- Boutillon Arthur
- Legouis Renaud
- Schanne-Klein Marie-Claire
- Stringari Chiara
- Beaurepaire Emmanuel
Optica, Optical Society of America - OSA Publishing , 2019, 6 (3), pp.385-388 . Polarization-resolved third-harmonic generation (P-THG) is a sensitive probe of material anisotropy and molecular ordering. Despite its promises, this property has little been used in biological tissues due to the lack of measurement schemes compatible with dynamic samples. We report here on the development of a fast P-THG microscope where excitation polarization is switched between line scans using an electro-optic modulator, providing temporal resolution in the 10 ms range for the polarimetric measurement. We demonstrate novel applications enabled by this approach, associated with Fourier-based analysis: probing molecular order in deforming lipid structures undergoing phase transition; revealing crystallinity of flowing particles in the zebrafish embryo’s inner ear; and detecting birefringence in vivo. These results establish that P-THG is ideally suited for probing lipid organization and mineralization in dynamic biological environments. (10.1364/OPTICA.6.000385)
DOI : 10.1364/OPTICA.6.000385
Tailoring the photophysical properties and excitonic radiative decay of soluble CdSe quantum dots by controlling the ratio of capping thiol ligand
- Mrad Randa
- Poggi Mélanie
- Brahim Nassim Ben
- Chaâbane Rafik Ben
- Négrerie Michel
Acta Materialia, Elsevier , 2019, 5, pp.100191 . We report the physical and photophysical properties of CdSe quantum dots capped with three different thiol compounds (thioglycolic acid, 3-mercaptopropionic acid, mercaptosuccinic acid) synthesized through a hydrothermal protocol. We calculated the true molecular weight and molar absorption coefficient of QDs from their diameter (not from any empirical relation) which are in the range 3.5 – 5.9 nm. The aqueous synthesis method ensures the insertion of the sulfur atoms of thiol ligands in the crystal CdSe cubic lattice, producing hexagonal crystal unit defects at the surface of the QDs. The QDs steady-state emission spectra were analyzed in terms of Gaussian components, in correlation with the time-resolved emission. We have elaborated MSA-CdSe QDs capped with mercaptosuccinic acid using various stoichiometric Cd/MSA ratios during the aqueous synthesis. Modulating the Cd/MSA ratio directly affects the size and photophysics of the QDs, in particular the fluorescence emission spectrum and decay. We rationalized the effect on QDs size by a change of the CdSe formation rate during synthesis. Acting on the Cd/MSA ratio appears a mean of modulating the emission spectrum and understanding the photophysical processes involved with respect to the QD structure. (10.1016/j.mtla.2018.100191)
DOI : 10.1016/j.mtla.2018.100191
Synthesis and Structure–Activity Relationship Studies of Benzo[ b ][1,4]oxazin‐3(4 H )‐one Analogues as Inhibitors of Mycobacterial Thymidylate Synthase X
- Modranka Jakub
- Li Jiahong
- Parchina Anastasia
- Vanmeert Michiel
- Dumbre Shrinivas
- Salman Mayla
- Myllykallio Hannu
- Becker Hubert
- Vanhoutte Roeland
- Margamuljana Lia
- Nguyen Hoai Viet
- Abu el‐asrar Rania
- Rozenski Jef
- Herdewijn Piet
- De jonghe Steven
- Lescrinier Eveline
ChemMedChem, Wiley-VCH Verlag , 2019, 14 (6), pp.645-662 . (10.1002/cmdc.201800739)
DOI : 10.1002/cmdc.201800739
Frequency-Domain Two-Dimensional Infrared Spectroscopy using an Acousto-Optic Programmable Dispersive Filter
- Alberto de La Paz José
- Bonvalet Adeline
- Joffre Manuel
Optics Express, Optical Society of America - OSA Publishing , 2019, 27 (4), pp.4140-4146 . We report on multidimensional spectroscopy in the mid-infrared performed using a calomel-based acousto-optic programmable dispersive filter. Although the associated spectral resolution is currently not as good as what has been previously reported using time-domain interferometers or other pulse-shaping technologies, the extreme compactness of the calomel crystal allows a straightforward implementation in a pre-existing pump-probe setup. Furthermore, the frequency-domain approach allows easy measurement of 2D slices of the multidimensional spectrum associated with a given pump frequency. We demonstrate our method with the measurement of the mid-infrared spectrum of carboxy-hemoglobin in three spectro-temporal dimensions. (10.1364/OE.27.004140)
DOI : 10.1364/OE.27.004140
Third harmonic generation imaging and analysis of the effect of low gravity on the lacuno-canalicular network of mouse bone
- Genthial Rachel
- Gerbaix Maude
- Farlay Delphine
- Vico Laurence
- Beaurepaire Emmanuel
- Débarre Delphine
- Gourrier Aurélien
PLoS ONE, Public Library of Science , 2019, 14 (1), pp.e0209079 . The lacuno-canalicular network (LCN) hosting the osteocytes in bone tissue represents a biological signature of the mechanotransduction activity in response to external biomechanical loading. Using third-harmonic generation (THG) microscopy with sub-micrometer resolution, we investigate the impact of microgravity on the 3D LCN structure in mice following space flight. A specific analytical procedure to extract the LCN characteristics from THG images is described for ex vivo studies of bone sections. The analysis conducted in different anatomical quadrants of femoral cortical bone didn't reveal any statistical differences between the control, habitat control and flight groups, suggesting that the LCN connectivity is not affected by one month space flight. However, significant variations are systematically observed within each sample. We show that our current lack of understanding of the extent of the LCN heterogeneity at the organ level hinders the interpretation of such investigations based on a limited number of samples and we discuss the implications for future biomedical studies. (10.1371/journal.pone.0209079)
DOI : 10.1371/journal.pone.0209079
Monitoring dynamic collagen reorganization during skin stretching with fast polarization‐resolved second harmonic generation imaging
- Ducourthial Guillaume
- Affagard Jean‐sébastien
- Schmeltz Margaux
- Solinas Xavier
- Lopez‐poncelas Maeva
- Bonod‐bidaud Christelle
- Rubio‐amador Ruth
- Ruggiero Florence
- Allain Jean-Marc
- Beaurepaire Emmanuel
- Schanne-Klein Marie-Claire
Journal of Biophotonics, Wiley , 2019, 12 (5), pp.e201800336 . The mechanical properties of biological tissues are strongly correlated to the specific distribution of their collagen fibers. Monitoring the dynamic reorganization of the collagen network during mechanical stretching is however a technical challenge because it requires mapping orientation of collagen fibers in a thick and deforming sample. In this work, a fast polarization-resolved SHG microscope is implemented to map collagen orientation during mechanical assays. This system is based on line-to-line switching of polarization using an electro-optical modulator and works in epidetection geometry. After proper calibration, it successfully highlights the collagen dynamic alignment along the traction direction in ex vivo murine skin dermis. This microstructure reorganization is quantified by the entropy of the collagen orientation distribution as a function of the stretch ratio. It exhibits a linear behavior, whose slope is measured with a good accuracy. This approach can be generalized to probe a variety of dynamic processes in thick tissues. (10.1002/jbio.201800336)
DOI : 10.1002/jbio.201800336
Ces manuscrits que l’on croyait perdus – La renaissance des manuscrits de Chartres
- Robinet Laurianne
- Pottier Fabien
- Schmeltz Margaux
- Heu-Thao Sylvie
- Poirel Dominique
- Rabel Claudia
- Schanne-Klein Marie-Claire
- Latour Gaël
- Michelin Anne
Support Tracé, Association pour la Recherche Scientifique sur les Arts Graphiques (ARSAG) , 2019, 18, pp.12-21 .
Generalized time delay, velocity, and absorption in dispersive and absorbing media
- Gallot Guilhem
Physical Review A, American Physical Society , 2019, 99 (1) . (10.1103/PhysRevA.99.013829)
DOI : 10.1103/PhysRevA.99.013829
Size-Exclusion Mechanism Driving Host-Guest Interactions between Octahedral Rhenium Clusters and Cyclodextrins
- Ivanov Anton A
- Falaise Clement
- Laouer Kevin
- Hache François
- Changenet Pascale
- Mironov Yuri V
- Landy David
- Molard Yann
- Cordier Stéphane
- Shestopalov Michael A
- Haouas Mohamed
- Cadot Emmanuel
Inorganic Chemistry, American Chemical Society , 2019, 58 (19), pp.13184-13194 . In aqueous solution, cyclodextrins (CDs) are able to bind strongly either hydrophobic species or also hydrophilic molecules such as octahedral hexametallic cluster. Systematic investigation of the reactivity between native CDs (α- or β-CD) and water-soluble rhenium clusters [ReQ(CN)] with Q = S, Se, and Te were performed, leading to six new crystal structures revealing different types of supramolecular arrangements. Encapsulation of [ReQ(CN)] (Q = S, Se, or Te) within two β-CDs is observed regardless of the cluster size. Interestingly, different assembling scenarios are pointed out depending on the host-guest matching featured by no, partial, or deep inclusion complexes that involved either primary or secondary rim of the CD tori. In the specific case of α-CD, only the smaller cluster [ReS(CN)] is able to form inclusion complex with the tori host. Solution investigations, using a set of complementary techniques including isothermal titration calorimetry, multinuclear NMR methods, cyclic voltammetry, and electrospray ionization mass spectrometry, corroborate nicely conclusions of the solid-state studies. It appears clearly that size-matching supported by solvent effects play key roles in the stability of the host-guest complexes. At last, circular dichroism studies underline that the chirality induction from cyclodextrins to the rhenium cluster depends strongly on the strength of host-guest interactions. (10.1021/acs.inorgchem.9b02048)
DOI : 10.1021/acs.inorgchem.9b02048
An actin-based viscoplastic lock ensures progressive body-axis elongation
- Lardennois Alicia
- Ferraro Teresa
- Llense Flora
- Labouesse Michel
- Pásti Gabriella
- Pontabry Julien
- Rodriguez David
- Kim Samantha
- Gally Christelle
- Mahou Pierre
- Beaurepaire Emmanuel
- Ono Shoichiro
Nature, Nature Publishing Group , 2019, 573 (7773), pp.266-270 . Body-axis elongation constitutes a key step in animal development, laying out the final form of the entire animal. It relies on the interplay between intrinsic forces generated by molecular motors1,2,3, extrinsic forces exerted by adjacent cells4,5,6,7 and mechanical resistance forces due to tissue elasticity or friction8,9,10. Understanding how mechanical forces influence morphogenesis at the cellular and molecular level remains a challenge1. Recent work has outlined how small incremental steps power cell-autonomous epithelial shape changes1,2,3, which suggests the existence of specific mechanisms that stabilize cell shapes and counteract cell elasticity. Beyond the twofold stage, embryonic elongation in Caenorhabditis elegans is dependent on both muscle activity7 and the epidermis; the tension generated by muscle activity triggers a mechanotransduction pathway in the epidermis that promotes axis elongation7. Here we identify a network that stabilizes cell shapes in C. elegans embryos at a stage that involves non-autonomous mechanical interactions between epithelia and contractile cells. We searched for factors genetically or molecularly interacting with the p21-activating kinase homologue PAK-1 and acting in this pathway, thereby identifying the α-spectrin SPC-1. Combined absence of PAK-1 and SPC-1 induced complete axis retraction, owing to defective epidermal actin stress fibre. Modelling predicts that a mechanical viscoplastic deformation process can account for embryo shape stabilization. Molecular analysis suggests that the cellular basis for viscoplasticity originates from progressive shortening of epidermal microfilaments that are induced by muscle contractions relayed by actin-severing proteins and from formin homology 2 domain-containing protein 1 (FHOD-1) formin bundling. Our work thus identifies an essential molecular lock acting in a developmental ratchet-like process. (10.1038/s41586-019-1509-4)
DOI : 10.1038/s41586-019-1509-4
Implementation of artifact-free circular dichroism SHG imaging of collagen
- Schmeltz Margaux
- Teulon Claire
- Latour Gaël
- Ghoubay Djida
- Borderie Vincent
- Aimé Carole
- Schanne-Klein Marie-Claire
Optics Express, Optical Society of America - OSA Publishing , 2019, 27 (16), pp.22685 . Second harmonic generation (SHG) enables in situ imaging of fibrillar collagen architecture in connective tissues. Recently, Circular Dichroism SHG (CD-SHG) microscopy has been implemented to take advantage of collagen chirality to improve 3D visualization. It measures the normalized difference in the SHG signal obtained upon excitation by left versus right circular polarizations. However, CD-SHG signal is not well characterized yet, and quite different CD-SHG values are reported in the literature. Here, we identify two major artifacts that may occur in CD-SHG experiments and we demonstrate that thorough optimization and calibration of the experimental setup are required for CD-SHG imaging. Notably it requires a careful calibration of the incident circular polarizations and a perfect mechanical stabilization of the microscope stage. Finally, we successfully record CD-SHG images in human cornea sections and confirm that this technique efficiently reveals collagen fibrils oriented out of the focal plane. (10.1364/OE.27.022685)
DOI : 10.1364/OE.27.022685