Figure 4. CNE1 mediates direct autoregulation and positive feedback via a paired domain binding site. (A) CNE1-Motif1 is homologous to the 59 region of defined PD binding sites, however the alignment diverges in the 39 region. (B) EMSA performed using Motif1 DNA and in-vitro synthesised Pax3 and Pax7 proteins, both of which can bind the sequence. (C) EMSA using Motif1 DNA and chick spinal cord nuclear extract, addition of antibodies against Pax3 or Pax7 to the reaction decreases the mobility of the DNA/protein complex. Addition of Pax6 or Pax2 antibodies does not alter the distribution of complexes within the EMSA. (D) Schematic illustrating the mutations targeted within CNE1-Motif1. (E, E9) M1PAIMut transgenic zebrafish exhibit a marked reduction in CNE1 activity in spinal cord progenitors, compared to the wildtype enhancer (n = 2/38, p,0.001). (F) Mutation of the PAI domain binding site precludes CNE1 activity in the chick neuraltube (n = 0/8, p = 0.0007). (G, G9) Mutation of the RED domain binding site phenocopies Motif1 deletion in zebrafish embryos (n = 0/19, p,0.001) and chick embryos (H) (n = 1/5, p = 0.0128). (I) EMSAs performed using in vitro synthesised Pax3 protein and Motif1 DNA harboring either PAI or RED mutations. Mutation of either PAI or RED region precludes complex formation. (J) Competition EMSA performed using in vitro synthesised Pax7 protein, radiolabelled wildtype Motif1 DNA and non-labeled competitor probes. Non-labeled wildtype DNA effectively competes with radiolabelled probe for Pax7 binding, whereas DNA harboring the RED mutation cannot. (K) Electroporation of PAX3FOXO1A-RCAS induces ectopic CNE1 activity and Pax3 protein expression in the ventral neuraltube (n = 9). (L) Pax7-RCAS electroporation also induces CNE1 activity and Pax3 expression (n = 7). Electroporation of dominant negative forms of Pax3 (M) (n = 7) or Pax7 (N) (n = 6) represses Pax3 protein expression within its endogenous domain.
The most extensively studied mouse model is the curly tail (ct) model , initially described in 1954 by Hans Grunberg. Curly tail provides a useful mouse model for comparison with humans due to common features including partial penetrance with a major influence of genetic modifiers and environmental factors . These mice have a high incidence of spina bifida and distinct morphological abnormalities including kinked and curled tails, which are attributed to homozygous loss of function of a recessive gene (ct)  and shown in Figure 1. The ct genetic defect has been mapped by linkage studies using microsatellite markers to chromosome 4 to the region containing grainyhead-like-3 (Grhl3) (reviewed in ). A mutation in the upstream enhancer element of Grhl3 has been shown to be responsible for the development of spina bifida in ct/ct embryos . Grhl3 is a transcription factor essential for neuraltube closure as Grhl3 knockout mice (Grhl3-/-) develop NTD with a 100% penetrance and mice with hypomorphic expression of Grhl3 do not survive [39–41]. Grhl3 belongs to the Grh/CP2 family of proteins which are involved in transcription regulation due to their multidomain protein structure which includes dedicated regions for DNA binding and protein dimerization. Grhl3 regulates expression of proteins involved in neuraltube closure and is involved in other crucial biological processes such as epidermis development and wound healing .
Neuraltube defects (NTDs) are among the most common congenital defects with a high incidence of 1-2 per 1000 births, causing a heavy burden to both the families and society. Various types of NTDs result from defects happening in the neurulation process during vertebrate embryonic development. In order to prevent the occurrence of NTDs, understanding the underlying mechanism is a prerequisite. The etiology of NTDs is complex involving environmental and genetic factors. Folic acid supplementation was proven to efficiently decrease the frequency of NTDs by 50-70% depending on the time point of this supplementation and demographic background. Gene identification studies in NTDs have adopted mainly a candidate gene approach investigating folate-related genes and genes derived from animal models. In particular, studies in mouse models have demonstrated a strong association between the non canonical Wnt/Planar Cell Polarity (PCP) pathway and NTDs. Protein Tyrosine Kinase 7 (PTK7) is a member of the PCP pathway and was shown to cause a very severe form of NTDs called craniorachischisis in a mouse model. Ptk7 genetically interacts with a core PCP member Vangl2 where double heterozygotes suffer from spina bifida. These data make PTK7 a strong candidate for NTDs in humans. We sequenced the coding region and the exon-intron junctions of PTK7 in a cohort of 473 patients affected with various forms of open and closed NTDs. Novel and rare variants (<1%) were genotyped in a cohort of 473 individuals. Their pathogenic effect was predicted in silico and functionally in an overexpression assay in a well established zebrafish model. We identified in our cohort 6 novel rare mutations, 3 of which are absent in all public databases, in 1.1% of our NTD cohort. One variant, p.Gly348Ser, acted as a hypermorph when overexpressed in the zebrafish model. Our findings implicate mutation of PTK7 as a risk factor for NTDs and provide additional evidence for a pathogenic role of PCP signaling in these malformations.
III. Mindbomb is required for planar cell polarity
Midline crossing C-divisions are one of the key features of zebrafish neurulation. The C- divisions that take place during neural keel and neural rod stages, generate two daughter cells with mirror symmetric apico-basal polarity. The apical polarity protein Pard3 accumulates at the cleavage furrow and is inherited by the two daughters equally at the abscission plane that coincides with the forming neuraltube midline. After the division, the two daughter cells stretch themselves along the prospective apico-basal extent of the neuro-epithelium and form projections that reach the basal membrane, and remain connected at the apical tip, where Pard3 localizes (Tawk et al., 2007). Therefore, C-divisions were considered as the driving force for establishing apico-basal polarity in the zebrafish neuroepithelium. However, more recently other studies have presented evidence against the obligatory role of C-divisions for apico-basal polarity establishment (Buckley et al., 2013; Žigman et al., 2011), but still considered that C- division provide a morphogenetic advantage to the embryo (Buckley et al., 2013).
Distance from centre
A straight line was drawn in the centre of the neuraltube by following the lumen in all movie time points. membrane-GFP+, sh-SMAD3 Sox2p:GFP + or pSUPER control Sox2p:GFP + mitosis were spotted and tracked back until the beginning of the movie. The distance from the drawn midline to the analysed cell and their daughter cells was measured in each time point with the ImageJ straight-line tool. Results along time are presented in GraphPad Prism 6 linear regression graphs.
Besides mediating morphogenic responses, the hh signalling pathway has been shown to govern the size of different structures in the embryo by acting on cell growth (Duman-Scheel et al., 2002; Gritli- Linde et al., 2002), cell survival and/or cell proliferation (Ahlgren and Bronner-Fraser, 1999; Charrier et al., 2001; Jeong et al., 2004; Machold et al., 2003; Thibert et al., 2003), the latter being particularly well documented for the central nervous system (reviewed in (Ruiz i Altaba et al., 2002)). During embryonic development, Shh acts as a mitogen in the primordia of ventral and dorsal regions of the diencephalon and midbrain in early somite-stage mouse embryos (Britto et al., 2002; Ishibashi and McMahon, 2002). The spinal cord of mouse embryos misexpressing Shh displays overgrowth due to an overproliferation (Rowitch et al., 1999). Mice lacking negative feedback of hh signalling have a larger neuraltube, possibly due to small increase in proliferation or survival rates that have cumulative effects over time (Jeong and McMahon, 2005). During mid-embryogenesis, the dorsal aspect of the brain, including the neocortex and cerebellum, undergoes rapid extension and Shh has been shown to promote proliferation of cerebellar granule cells and neocortical precursors ((Dahmane and Ruiz i Altaba, 1999; Dahmane et al., 2001; Wallace, 1999; Wechsler-Reya and Scott, 1999) reviewed by (Ruiz i Altaba et al., 2002)). In the adult brain, neurogenesis occurs in the subventricular zone of the lateral ventricular walls of the forebrain and in the subgranular layer of the dentate gyrus of the hippocampus and Shh is required for neural progenitor proliferation in both areas (Lai et al., 2003; Machold et al., 2003; Palma et al., 2005; Palma and Ruiz i Altaba, 2004). Thus, accumulated evidence reveals that Shh is extensively involved in the control of cell proliferation. As a corollary, deregulation of this pathway have been associated with the initiation and growth of several cancers (Ruiz i Altaba et al., 2004).
Neuraltube defects are the most common and severe malformations of the central nervous system, affecting 1-2/1000 live births. They result from failure of neuraltube closure early during embryogenesis, which could occur at any level along the rostrocaudal axis. The two most common NTDs are anencephaly and myelomeningocele (spina bifida) that affect the cranial and spinal region of the neuraltube respectively (Bassuk and Kibar, 2009). Anencephaly is characterized by complete absence of the skull and is invariably lethal. Myelomeningocele (MMC), which is most commonly lumbosacral, involves the protrusion of the spinal cord through a bony defect within a sac-like membrane that contains cerebrospinal fluid. MMC is compatible with life buts leads to severe and life-long physical and developmental disabilities. Anencephaly and MMC are referred to as “open” NTDs where the nervous system and/or meninges are exposed to the environment without normal skin covering. A heterogeneous group of “closed” NTDs involves no exposed neural tissue or visible cystic mass and is categorized clinically depending on the presence (lipomyeloschisis, lipomyelomeningocele, meningocele, and myelocystocele) or absence of a subcutaneous mass (split cord malformations, dermal sinus, and intradural lipoma). Although periconceptional folic acid supplementation has significantly reduced the frequency of NTDs, roughly 30% of NTDs appear resistant to folic acid and these devastating conditions still affect thousands of families each year (Bassuk and Kibar, 2009). Caudal agenesis is a heterogeneous constellation of anomalies comprising total or partial agenesis of the spinal column, anal imperforation, genital anomalies, bilateral renal dysplasia or aplasia, pulmonary hypoplasia, and lower limb abnormalities (Rossi et al., 2004). Caudal regression is thought to arise from a defect in gastrulation leading to a deficiency of caudal mesoderm (Aslan et al., 2001). It has been suggested that there is an etiological relationship between NTDs and caudal agenesis and they have been considered together in some clinical reviews (Tortori-Donati et al., 2000).
Neuraltube defects (NTDs), including anencephaly and spina bifida, represent a group of very common birth defects in humans. These anomalies are caused by a partial or complete failure of neuraltube closure during embryogenesis. NTDs have a multifactorial etiology involving environmental and genetic factors. The non-canonical signaling pathway Frizzled (Fz) / Dishevelled (Dvl) controls the planar cell polarity (PCP) and the morphogenetic process called convergent extension (CE) which is essential for gastrulation and neuraltube closure. Importantly, mutations in genes of this pathway were strongly associated with NTDs in mice and humans. Scribble is a PCP gene that causes a severe NTD mouse Circletail. Scribble binds to another PCP protein, Stbm / Vang, and they cooperate together for the stability of the PCP pathway. Our study aims at investigating the role of SCRIBBLE1 in human NTDs by sequence analyses of its open reading frame and exon-intron junctions. The cohort included in this study consisted of 396 patients recruited at the Spina Bifida Centre of Gaslini Hospital in Genoa, Italy, and 83 patients recruited at the Spina Bifida Center of the Sainte Justine Hospital, Montreal, Canada. Patients were affected by several forms of NTDs. We identified nine non-synonymous and rare mutations in 10 patients: p.Asp93Ala (c. 435G>A), p.Gly145Arg (c. 278A>C), p.Gly263Ser (c. 786C>A), p.Gly469Ser (c. 1405G>A), p.Pro649His (c. 1946C>A), p.Gln808His (c. 2424G>T), p.Val1066Met (c. 3196G>A), p.Arg1150Gln (c. 3480G>A) and p.Thr1422Met (c. 4266C>T). Five of those mutations, p.Gly263Ser, p.Pro649His, p.Gln808His, p.Arg1150Gln, p.Thr1422Met, were absent in all controls analyzed and were predicted to be pathogenic using bioinformatics. Our study demonstrates that rare mutations in SCRIB1 could predispose to NTDs in a fraction of patients. The identification of genes that predispose to ATN will help us better understand the pathogenic mechanisms involved in these diseases.
transcriptional activity of this gene during neuraltube formation. This important genotype-phenotype correlation needs to be confirmed in a larger cohort of patients.
Transcriptional properties of GRHL3 can also be finely tuned by the different roles of the various isoforms as previously reported for other transcription factors including Pax genes [Monsoro-Burq 2015]. Different isoforms of Grhl3 were previously shown to have different and even opposing functions in cell migration, apoptotic activity and nitric oxide synthase in endothelial cells as well as in their abilities to induce severe malformations in zebrafish embryos [Haendeler et al. 2013]. Microarray analyses revealed different target genes between the two Grhl3 isoforms, and it was proposed that this could explain the opposite effects of these proteins in endothelial cells. In our study, we demonstrated that while isoform 2 could activate the reporter gene in HEK293 cells, isoform 3 failed to do so. This was not due to lack of expression of isoform 3 since it was proven by western blot that both proteins were expressed. Further investigations through combined transfections of multiple isoforms affected by various variants or deletion constructs are needed to better understand the seemingly complex interactions affecting this gene function. Identification of key target genes of all GRHL3 isoforms would be crucial for a better understanding of their versatile roles in multiple developmental processes including neurulation and in human diseases.
O. García -Valladares  a réalisé une simulation numérique unidimensionnelle
transitoire détaillée du comportement thermique et dynamique des échangeurs de chaleur à triple tube concentrique. Les équations gouvernantes (continuité, mouvement et énergie) sont déterminées à l'intérieur de tube central et de passage annulaire (intérieur et extérieur), ainsi que les équations d'énergie dans les parois et l'isolation extérieure de tube. Ces équations sont résolues itérativement. Les équations gouvernantes sont discrétisées dans les zones avec les flux de fluide couplés en utilisant la méthode étape-par-étape implicite. Cette formulation exige l'utilisation des corrélations empiriques pour l'évaluation du coefficient de transfert de chaleur par convection, de l'effort de cisaillement. Un schéma numérique de différence centrale implicite et un solutionneur ligne par ligne ont été employés dans les parois des tubes intérieurs, intermédiaire extérieure avec l'isolation thermique. Toutes les grandeurs de l'écoulement (enthalpies, températures, pressions, fractions massiques, vitesses, etc.) ainsi que les propriétés thermophysiques sont évaluées à chaque point de maillage dans lequel le domaine est discrétisé.
continuum damage tool to predict formability is enlightened.
KEYWORDS: Hydroforming, Thick T-shaped tubes, Computation, Elastoplasticity.
T-shaped tube hydroforming has been studied for a long time and the major part of the study available are related to the formability of thin metallic tubes. Numerous methods like FLD or localisation crite- rion are widely use to predict formability. During T- shaped and Y-shaped tube hydroforming stress state is no more plan and standard localisation criterion are shown to be conservative ().
Free-end hydroforming, in which no end feeding is applied but the tube ends can move freely during the process, was simulated to find the minimum end feeding that occurs during THF. That is, by increasing the internal pressure, as the tube expands, the material is pulled into the die cavity from both ends of the tube. Figure 3 illustrates the load path in the free-end hydroforming process for the 0.9 mm and 1.2 mm thick tubes obtained from the FEM. This curve can be used to identify the minimum input values for optimization, which was performed in this work using a single stroke load path approach. It is noteworthy that an end feed value higher than the free-end condition is needed to maintain the seal during the process. Hence, the minimal values (lower band) for the internal pressure and end feeding were selected as 20 MPa and 1.2 mm, respectively. The upper band for the internal pressure was considered to be 100 MPa, which was sufficient for the full expansion of the tube in the THF process. By performing a few simulations of the FEMs, the upper band of end feeding was selected as 20 mm to avoid wrinkling in the tube.
Forced convective boiling experiments of HFE-7000 are conducted in earth gravity and under microgravity conditions. The experiment mainly consists in the study of a two-phase flow through a 6 mm diameter sapphire tube uniformly heated by an ITO coating. The parameters of the hydraulic system are set by the conditioning system and measurements of pressure drops, void fraction and wall and fluid temperatures are provided. High-speed movies of the flow are also taken. The data are collected in normal gravity and during a series of parabolic trajectories flown onboard an airplane. Flow visualizations, temperature, void fraction and pressure drop measurements are analyzed to obtain flow pattern, liquid film thickness in annular flow, wall and interfacial shear stresses and heat transfer coefficient.
d ), and empirical Bayes is
the machinery to denoise in a least-squares sense, which we express as X ) Y . A learning objective is derived by combining these two, symbolically captured by X Y . Crucially, instead of using the original nonparametric estimators, we parametrize the energy function with a neural network denoted by φ; at optimality, ∇φ ≈ −∇ log f where f is the density of Y . The optimization problem is abstracted as interactions of high-dimensional spheres which emerge due to the concentration of isotropic Gaussians. We introduce two algorithmic frameworks based on this machinery: (i) a “walk-jump” sampling scheme that combines Langevin MCMC (walks) and empirical Bayes (jumps), and (ii) a probabilistic framework for associative memory, called NEBULA, defined ` a la Hopfield by the gradient flow of the learned energy to a set of attractors. We finish the paper by reporting the emergence of very rich “creative memories” as attractors of NEBULA for highly-overlapping spheres.
The fretting wear of steam generator tubes due to vibration remains an important problem in the nuclear industry. The friction models used to model the tube-support interaction cited by (M. Hassan & Rogers, 2005) are special cases of static friction models. The velocity limited friction model (VLFM) (Rogers & Pick, 1977) is a continuous Coulomb model without Stribeck effects. However, the other two models, the force balance friction model (FBFM) (Xi & Rogers, 1996) and the spring damper friction model (SDFM) (Antunes et al., 1988) are based on the modeling of friction by springs and dampers. The principle of Karnopp friction model (Karnopp, 1985) is used in the FBFM model. The newest model of friction designed to model the tube-support interaction is the hybrid friction model (Azizian, 2012; Azizian & Mureithi, 2013), the authors used the dynamics of Dahl model (Dahl, 1976), the principle of LuGre model (Canudas et al., 1995) with consideration of stress distributions in the contact area in accordance with the principle of Cattaneo-Mindlin (Kenneth Langstreth Johnson, 1985).
In the field of plant biology, sexual reproduction through pollination is a topic of interest since it affects human life and economic issues. The pollen tube is a plant cell that is indispensable for the pollinisation of flowers. Plant cell growth occurs by a deformation of the surrounding wall under the effect of an internal hydrostatic pressure, the turgor pressure. At the same time, new material has to be delivered to the wall in order to prevent bursting caused by the thinning of the wall that in turn is a result of the turgor induced stretching. In the pollen tube, surface growth is located at the apex of the cell and it leads to the formation of a cylindrical protuberance. This type of growth, combined to the particular biological system of the pollen tube, provides an excellent model for mechanical studies of growing plant cells. Numerous models for apical growth have been used to study the parameters and processes involved. These models present different methods to approach the problem whether it is geometrical, mathematical or mechanical. However, most of these models depend on the axisymmetry of the tubular structure. The finite element method allows one to represent complex shapes or to easily change the mathematical models used for calculation. This potential is particularly suited for the study of biological structures that are able to change shape or to manipulate their mechanical properties. The finite element modeling approach has been adopted in this project.
2.3 Conclusion intermédiaire
Le dispositif expérimental mis en place a permis de générer un phénomène ayant les caractéristiques d’un broutement régénératif pour une pièce cylindrique à paroi mince. La mesure de déplacement en extrémité de tube est exploitable et son spectrogramme montre clairement l’apparition de vibrations en accord avec les défauts observés sur la pièce. Les fréquences observées évoluent avec l’avancement de l’outil. En fin de dernière passe, cette évolution se fait par paliers. Ces paliers correspondent aux bandes de défauts observés sur la surface de la pièce usinée. Nous avons constaté que les fréquences composant le spectre de vibrations observées de la pièce sont similaires aux pulsations naturelles de la pièce. La fréquence principale à laquelle apparaissent les vibrations auto- entretenues est la fréquence comprise dans la plage de 2100 à 1670 Hz. Cette fréquence correspond à l'une des fréquences naturelles de la coque. Cette fréquence évolue suite à l’enlèvement de la matière au cours de la passe (perte de masse et de raideur). L’enlèvement de matière a donc, pour cet exemple, un effet significatif. Par ailleurs, une expérience a été menée pour élaborer un modèle pour la détermination des forces de coupe au voisinage des conditions nominales. Nous avons ainsi déterminé les coefficients de la loi de coupe linéarisée en fonction de la profondeur et de l'avancement de la coupe correspondant à la 16 ème passe (dernière passe), durant laquelle ont été observées les vibrations.
optimized single-tree networks than from jointly training one large network for all trees. This means that ensemble averaging (Method 1) is more ad- vantageous for the NRF model than the co-adaptation of parameters across trees (Method 2). We conjecture that by separating the optimization process for the individual networks, some implicit regularization occurs that reduces the vulnerability to overfitting when using Method 1. Additionally, it is im- portant to note the excellent performance of BART, which is ranked first in 6 out of the 7 experiments. Although in this context BART should be seen as a benchmark, it remains that a good idea for future research is to use BART to design neural networks, and extend the approach presented in this article.