In this dissertation we investigate the behavior of radially symmetric non-Euclidean plates of thickness t with constant negative Gaussian curvature. We present a complete study of these plates using the Föppl-von Kármán and Kirchhoff reduced theories of elasticity. Motivated by experimental results, we focus on deformations with a periodic profile. For the Föppl-von Kármán model, we prove rigorously that minimizers of the elastic energy converge to saddle shaped isometric immersions. In studying this convergence, we prove rigorous upper and lower bounds for the energy that scale like the thickness t squared. Furthermore, for deformation with n-waves we prove that the lower bound scales like nt² while the upper bound scales like n²t². We also investigate the scaling with thickness of boundary layers where the stretching energy is concentrated with decreasing thickness. For the Kichhoff model, we investigate isometric immersions of disks with constant negative curvature into R³, and the minimizers for the bending energy, i.e. the L² norm of the principal curvatures over the class of W^2,2 isometric immersions. We show the existence of smooth immersions of arbitrarily large geodesic balls in H² into R³. In elucidating the connection between these immersions and the nonexistence/ singularity results of Hilbert and Amsler, we obtain a lower bound for the L^∞ norm of the principal curvatures for such smooth isometric immersions. We also construct piecewise smooth isometric immersions that have a periodic profile, are globally W^2,2, and numerically have lower bending energy than their smooth counterparts. The number of periods in these configurations is set by the condition that the principal curvatures of the surface remain finite and grow approximately exponentially with the radius of the disc.

Research objective. Investigation of consistent patterns of the induction of flax morphogenesis process, assessment of genetic and physiological aspects of this process and optimization methodologies. Proposition: 1. MOrphogenesis capacity of flax isolated explants depends on a genotype only, but on a composition of a medium and the cultivar type (fibre flax or linseed)also. 2. Cells of different organs of the same genotype have different morphogenic capacity. 3. Combining hormonal ratio with the affect on explats by exogenic factors enables targeted control of the morphogenesis process in vitro. / Darbo tikslas - ištirti linų morfogenezės proceso indukcijos dėsningumus, įvertinti šio proceso genetinius ir fiziologinius aspektus bei optimizuoti regeneravimo metodikas. Ginamieji disertacijos teiginiai: 1. Linų izoliuotų eksplantų morfogeninė galia priklauso ne tik nuo genotipo, maitinamosios terpės sudėties, bet ir nuo veislės tipo (pluoštiniai ar sėmeniniai). 2.To paties genotipo skirtingų organų ląstelės turi skirtingą morfogeninę galią. 3.Derinant hormoninį balansą su eksplantų paveikimu egzogeniniais veiksniais galima kryptingai valdyti morfogenezės procesą in vitro.

Magistrantūros studijų baigiamajame darbe pateikiami lelijos (Lilium L.) morfogenezės indukcijos in vitro tyrimų duomenys. Darbo objektas: lelijų (Lilium L.) veislės ˈRed Beautyˈ, ˈWiener Blutˈ, ˈSėkmėˈ, ˈNoLimitˈ. Darbo metodai: lelijų (Lilium L.) izoliuoti eksplantai – svogūnėlių žvyneliai – auginti modifikuotoje MS maitinamojoje terpėje, kurios makro druskų koncentracija sumažinta iki 0,5 pradinio koncentracijos lygio, su skirtingais augimo reguliatorių deriniais. Vertintas mikrosvogūnėlių ir šaknų susiformavimo dažnis (%) bei mikrosvogūnėlių kiekis iš eksplanto (vnt.). Darbo rezultatai. Lelijų mikrosvogūnėlių formavimosi dažnį in vitro lemia augimo reguliatorių ir genotipo sąveika. Tos pačios lelijų veislės pasižymi skirtinga regeneracine galia, priklausomai nuo maitinamosios terpės sudėties. Iš tirtų veislių didžiausia regeneracine galia pasižymėjo veislės ˈRed Beautyˈizoliuoti eksplantai. Veislių ˈWiener Blutˈ ir ˈNo Limitˈ mikrosvogūnėlių regeneracijai in vitro maitinamąją terpę tikslinga papildyti 1,0 mg l-1 BAP + 0,3 mg l-1 2,4-D deriniu. Augimo reguliatorių derinys 2,0 mg l-1 BAP + 0,3 mg l-1 2,4-D labiausiai skatino veislės ˈRed Beautyˈ mikrosvogūnėlių susiformavimą. Veislės ˈSėkmėˈ izoliuoti eksplantai mikrosvogūnėlius formavo intensyviau augimo reguliatorių derinio 3,0 mg l-1 BAP + 0,3 mg l-1 2,4-D poveikyje. Intensyviausiai šaknis in vitro formavo veislių ˈRed Beautyˈ ir ˈWiener Blutˈ mikrosvogūnėliai. / The master work presents the results of increasing of lilies induction of morphogenesis in vitro studies. Object of the work: lilies (Lilium L.) cultivars of ˈRed Beautyˈ, ˈWiener Blutˈ, ˈSėkmėˈ, ˈNo Limitˈ. Methods of the work: Explants were cultured on the MS regeneration medium supplemented with macro salt concentration which is reduced to 0.5 of the initial concentration level, with different combinations of growth regulators. Evaluated for micro bulbs and root formation rate (%) and micro bulbs quantity of explant (units). The results of work. Lilies microbulbs formation in vitro is determined by the frequency of growth regulators and genotype interactions. The same varieties of lilies are characterized by different regenerative capacity, depending on the composition of the nutrient medium. Among investigated cultivars the highest morphogenic potention distinguished isolated explants of ˈRed Beautyˈ. For micropropagation of cultivars ˈWiener Blutˈ and ˈNo Limitˈ most suitable is medium supplement by 1,0 mg l-1 BAP + 0,3 mg l-1 2,4-D combination. Growth regulators combination 2,0 mg l-1 BAP + 0,3 mg l-1 2,4-D influenced cultivar ˈRed Beautyˈ. All isolated explants of cultivar ˈSėkmėˈ formed microbulbs on medium with 3,0 mg l-1 BAP + 0,3 mg l-1 2,4-D. The most intensive roots in vitro formed microbulbs varieties of ˈRed Beautyˈ and ˈWiener Blutˈ.

<p>Bud formation by Saccharomyces cerevisiae is a fundamental process for yeast proliferation. Bud emergence is initiated by the polarization of the cytoskeleton, leading to local secretory vesicle delivery and gulcan synthase activity. The master regulator of polarity establishment is a small Rho-family GTPase – Cdc42. Cdc42 forms a clustered patch at the incipient budding site in late G1 and mediates downstream events which lead to bud emergence. Cdc42 promotes morphogenesis via its various effectors. PAKs (p21-activated kinases) are important Cdc42 effectors which mediate actin cytoskeleton polarization and septin filament assembly. The PAKs Cla4 and Ste20 share common binding domains for GTP-Cdc42 and they are partially redundant in function. However, we found that Cla4 and Ste20 behaved differently during the polarization and this depended on their different membrane interaction domains. Also, Cla4 and Ste20 compete for a limited number of binding sites at the polarity patch during bud emergence. These results suggest that PAKs may be differentially regulated during polarity establishment.</p><p>Morphogenesis of yeast must be coordinated with the nuclear cycle to enable successful proliferation. Many environmental stresses temporarily disrupt bud formation, and in such circumstances, the morphogenesis checkpoint halts nuclear division until bud formation can resume. Bud emergence is essential for degradation of the mitotic inhibitor, Swe1. Swe1 is localized to the septin cytoskeleton at the bud neck by the Swe1-binding protein Hsl7. Neck localization of Swe1 is required for Swe1 degradation. Although septins form a ring at the presumptive bud site prior to bud emergence, Hsl7 is not recruited to the septins until after bud emergence, suggesting that septins and/or Hsl7 respond to a “bud sensor”. Here we show that recruitment of Hsl7 to the septin ring depends on a combination of two septin-binding kinases: Hsl1 and Elm1. We elucidate which domains of these kinases are needed, and show that artificial targeting of those domains suffices to recruit Hsl7 to septin rings even in unbudded cells. Moreover, recruitment of Elm1 is responsive to bud emergence. Our findings suggest that Elm1 plays a key role in sensing bud emergence.</p> / Dissertation

The development of organs such as the lung and kidney occurs by branching morphogenesis. Changes in the cytoskeletal architecture, cell-cell adhesion and cell polarity are necessary for the formation of new branches. Interactions and reciprocal signalling between epithelial and mesenchymal cells mediate these organised cell movements that give rise to a complex system of tubes suitable for the transport of gas or fluids. Mutations that disrupt formation of either the correct number, or shape of epithelial branches, affect lung function. This, in turn, can lead to congenital abnormalities such as cystadenomatoid malformations, pulmonary hypertension or lung hypoplasia. Defects in lung architecture are also associated with adult lung disease, particularly in cases of idiopathic lung fibrosis. Identifying the signaling pathways that drive epithelial tube formation will likely shed light on both congenital and adult lung disease. This study shows that mutations in the planar cell polarity (PCP) genes: Celsr1; Vangl2 and Scribble, lead to disrupted lung development and defects in lung architecture. Examination of Vangl2 mutant kidneys reveals similar impairment of branching morphogenesis. Detailed histological and immunocytochemical analysis reveals that lungs from Celsr1Crsh/Crsh, Vangl2Lp/Lp and ScribbleCrc/Crc mice are small and misshapen with fewer branches, and by late gestation exhibit thickened interstitial mesenchyme and defective saccular formation. Moreover, epithelial integrity is disrupted, cytoskeletal remodeling perturbed and mutant endoderm does not branch normally in response to the chemoattractant FGF10. In ex-vivo culture, inhibition of Rho kinase, an important downstream effector of the PCP signaling pathway, can mimic the branching defects observed in these three mouse mutants. Furthermore, all three proteins are present in restricted spatial domains within lung epithelium. ScribbleCrc/Crc lungs, the most severely affected line, exhibit additional defects in components of the tight and adherens junctions; this in turn affects lumen diameter. These findings show that components of the PCP pathway: Celsr1; Vangl2 and Scribble are required for normal foetal lung development, thereby revealing a novel signalling pathway critical for this process. Examination of postnatal mice was not possible as homozygous mutations result in embryonic lethality. However, an assessment of Vangl2Lp/+ mice reveals that loss of a single copy of Vangl2 is enough to cause defects in embryonic lung development that persist into adult life, affecting lung function. Similarly, Vangl2Lp/+ mice show a small but significant reduction in kidney glomeruli.

Les mitochondries sont des organelles de quelques micromètres qui proviendraient de l'incorporation d'une alpha-protéobactérie dans le cytoplasme des cellules eucaryotes par endosymbiose. Dans les cellules eucaryotes, la mitochondrie joue un rôle central dans la production d'ATP, mais aussi dans la mort cellulaire programmée par apoptose ainsi que dans la biosynthèse de nombreuses molécules. Les mitochondries sont très polymorphes, leurs taille, forme et organisation varient considérablement selon le type cellulaire ou l'état physiologique ou pathologique de la cellule. Depuis une vingtaine d'année, l'étude des mécanismes qui contrôlent la morphogenèse, la dynamique de fission et de fusion mitochondriale et leurs rôles physiologiques est devenue un domaine majeur dans la recherche sur la mitochondrie. De plus, avec les progrès de la vidéo-microscopie, il est devenu possible de filmer des mitochondries dans le cytoplasme de cellules vivantes. Durant ma thèse, j'ai participé à la caractérisation de la fonction du gène Pantagruelian Mitochondria I (PMI), un nouveau déterminant de la morphologie des mitochondries que nous avons découvert chez la drosophile. PMI est une protéine de la membrane interne qui, en intervenant dans l'organisation de cette membrane, est indispensable à la formation de mitochondries de forme tubulaire. J'ai également contribué au développement d'outils et de méthodologies permettant la visualisation et l'étude de la dynamique mitochondriale dans des embryons de drosophiles vivants. / Mitochondria are organelles which are a few micrometers long and are originated from the incorporation of an alpha-proteobacteria in the cytoplasm of eukaryotic cells through endosymbiosis. In eukaryotic cells, mitochondria play a central role in ATP production as well as in programmed cell death and in the biosynthesis of many molecules. Mitochondria are highly polymorphic in size and form. Their organization also varies considerably according to the cell type or physiological or pathological state of the cell. In the last two decades, the study of the mechanisms controlling morphogenesis, dynamic of mitochondrial fission and fusion and their physiological roles has become a major research field of mitochondria. In addition, the progress in video-microscopy enable to record mitochondrial dynamics in the cytoplasm of living cells. I participated in the research on the characterization of gene function called Pantagruelian Mitochondria I (PMI), a novel determinant of the mitochondrial morphology that we discovered in Drosophila. PMI, a protein of the inner membrane, is involved in its membrane organization and essential to form tubular mitochondria. I also contributed to the development of experimental tools and protocols to visualize and study the mitochondrial dynamics in living Drosophila embryos. Interestingly, a stereotyped process of mitochondrial remodeling during Drosophila embryogenesis has been found and it raised a question about its role in developmental processes through my work.

Des pathologies lourdes, telles que les dystrophies de la rétine et certains cancers, impliquent une désorganisation de l'épithélium et la famille Crb, dont la protéine apicale Crumbs3 (isoformes Crb3A et Crb3B) fait partie. Les protéines transmembranaires Crb possèdent un domaine intracellulaire fortement conservé et des partenaires communs. Il est donc essentiel de comprendre comment ces protéines Crb sont régulées afin de mieux appréhender ces pathologies. Pour cela, j'ai étudié le complexe de polarité apical Crb3A (Crb3A, Pals1, PATJ) impliqué dans l'établissement et le maintien de la polarité apico-basale. Je me suis, tout d'abord, intéressée à la régulation des isoformes de Crb3 par leurs partenaires (Pals1 et PATJ), puis, à la régulation des protéines de la membrane apicale, dont Crb3A, par la Drebrine E2, un nouveau partenaire de Crb3A impliqué dans l'organisation du cytosquelette d'actine et la morphogenèse apicale. Mon travail a permis de mettre en évidence: 1) la régulation de la dynamique membranaire des isoformes de Crb3 par PATJ dans les cellules Caco-2/TC7, une lignée épithéliale intestinale humaine, mais aussi, 2) d'identifier une nouvelle fonction de la Drebrine E2 dans la régulation du trafic de plusieurs protéines de la membrane apicale dans ces cellules, dont, par exemple, la DPPIV (DiPeptidyl Peptidase IV). Dans les cellules déplétées en Drebrine E2, l'expression des protéines apicales est diminuée et leur endocytose est augmentée, puis, elles sont relocalisées dans le compartiment majeur de dégradation, le lysosome. / Some serious diseases like retinal dystrophies and some cancers involve epithelial cells disorganization and the Crumbs (Crb) proteins family. The apical Crb3 (Crb3A and Cr3B isoforms) protein belongs to Crb family. The transmembrane proteins Crb have a conserved intracellular domain with common partners. It is unclear how Crb proteins are regulated by their partners and this information is required to better understand these pathologies. Here, we decided to study the apical polarity Crb3A complex (Crb3A, Pals1, PATJ) which is involved in apico-basal polarity establishment and maintenance. First, I investigated Crb3 isoforms regulation by their partners (Pals1 and PATJ). Then, I studied the regulation of apical membrane proteins, such as Crb3A, by Drebrin E2, a new partner of Crb3A which is involved in actin cytoskeleton remodeling and apical morphogenesis. During my thesis, I demonstrated: 1) the regulation of Crb3 isoforms dynamics by PATJ in Caco-2/TC7 human intestinal epithelial cells, but also, 2) a new function for Drebrin E2 in regulating the trafficking of apical membrane proteins, like DPPIV (DiPeptidyl Peptidase IV). In Drebrin E2 KD cells, apical membrane proteins expression is decreased and we observe an increased endocytosis. This leads to relocalization of the apical membrane proteins to the main degradative compartment, the lysosome. These new datas suggest a role for Drebrin E2 in the regulation of apical membrane proteins recycling pathway. The Drebrin E2 KD cells phenotype is reminiscent of the microvillar inclusions disease (MVID). Now, I am trying to investigate the link between theses pathways.

4 Neural crest-derived cellular cartilage is one of the defining characteristics of vertebrates. Elaboration of this tissue and its patterning allowed the evolution of jaws in the gnathostome lineage. Together these hallmarks helped jawed vertebrates become one of the dominant taxons in the animal kingdom. Lampreys, as basal jawless vertebrates, lie at a unique phylogenetic position that makes them ideal organisms for the study of evolution of vertebrate/gnathostome novelties. Larval lampreys possess a special oral skeleton composed of a tissue related to cartilage, termed mucocartilage. Despite considerable attention that has been paid to the evolutionary significance of mucocartilage, it is not yet clear, how this unique feature arises in development and to what extent it is homologous to gnathostome jaws. In this study, the development of oro-pharyngeal region was analyzed in the sea lamprey Petromyzon marinus. SEM imaging revealed shaping and topographic relationships of embryonic tissues, detailed plastic histology coupled with expression analyses of several molecular markers were used to describe origin, histogenesis and morphogenesis of mucocartilage. Furthermore, genetic regulation of the tissue was investigated in order to identify its unique or shared features. Mucocartilage is seen to...

La protéine de fonction inconnue, YvcK, est vitale chez Staphylococcus aureus mais non essentielle chez les bactéries modèles Bacillus subtilis ou Escherichia coli. Chez B. subtilis, les bactéries délétées du gène yvcK, sont sérieusement affectées dans leur croissance et leur morphologie dans des conditions de croissance gluconéogéniques. Les défauts observés peuvent être compensés par l’ajout de fortes concentrations de magnésium ou par l’inactivation de gènes impliqués dans le métabolisme. Ceci suggère que, les mutants yvcK présentent des altérations au niveau de la paroi bactérienne qui sont probablement dues à un désordre du métabolisme. Le phénotype lié à l’absence d’YvcK est similaire à celui observé chez des souches mutées au niveau de gènes impliqués dans la synthèse du peptidoglycane ou constituant le cytosquelette. La protéine MreB, composant majeur du cytosquelette bactérien, forme une structure hélicoïdale sous la membrane cytoplasmique pour positionner les enzymes de synthèse et la maturation du peptidoglycane. In vivo, la protéine YvcK est également localisée sous la forme d’une hélice. Par ailleurs, la surexpression de YvcK supprime le défaut de morphologie du mutant mreB et vice versa. Il a été montré que, chez B. subtilis, la localisation de la protéine membranaire PBP1 était dépendante de MreB. Une délétion de ponA, gène codant pour PBP1, rétablit la viabilité d’un mutant mreB et celle du mutant yvcK dans des conditions de croissance gluconéogéniques. La protéine de fusion GFP-PBP1 dans une souche délétée du gène yvcK, cultivée en milieu liquide CE-gluconate est délocalisée expliquant le gonflement des cellules. Ce résultat suggère que la localisation normale de PBP1 au septum due à la surproduction de YvcK dans un mutant mreB (et réciproquement) permet la restauration de la croissance et de la morphologie. De plus, nous avons montré que, comme son homologue présent chez Mycobacterium tuberculosis, YvcK est phosphorylée in vitro. Nous avons caractérisé la phosphorylation d’YvcK par la protéine kinase PrkC et nous avons identifié la Thr 304 comme site unique de phosphorylation. Cette phosphorylation semblerait jouer un rôle important dans la complémentation du mutant mreB et du repositionnement de la PBP1. / The YvcK protein is a bacterial conserved protein of unknown function. It is essential in Staphylococcus aureus but not essential in both Bacillus subtilis and Escherichia coli. In B. subtilis, inactivation of the yvcK gene seriously affects growth and morphology on neoglucogenic carbon sources. The defects observed in a yvcK mutant can be offset by the addition of high concentrations of magnesium or by inactivation of genes involved in metabolism. This suggests that, when grown on some carbon sources, yvcK mutants display alterations in their cell wall probably due to a disorder in this metabolism. The phenotype associated with the absence of YvcK is similar to that observed with strains mutated in genes involved in peptidoglycan synthesis or encoding proteins of the cytoskeleton. The major component of cytoskeleton, MreB, an actin-like protein, together with other proteins, forms a helical structure at the cell membrane that participates in the organization and positioning of the enzymes of peptidoglycan synthesis and maturation. We showed that YvcK is organized as a helical like pattern localized near the inner surface of the membrane, independently of the presence of MreB. Surprisingly and despite that these two proteins do not harbour any similarity of sequence or structure, an overproduction of YvcK restored a normal morphology in an mreB mutant strain and vice versa. Furthermore, as already observed for the mreB mutant, in a yvcK mutant strain, the penicillin-binding protein PBP1 is delocalized and deletion of its gene restores growth of a yvcK mutant on gluconate medium. All these results suggest that YvcK is not only involved in the synthesis of cell wall from gluconeogenic carbon sources but also plays a role in cell morphogenesis. In addition, we have shown that similarily to its Mycobacterium tuberculosis homolog, YvcK is phosphorylated in vitro. We have characterized the phosphorylation of YvcK by the protein kinase PrkC and we identified the Thr 304 as the single phosphorylation site. Furthermore, this phosphorylation appears to play an important role in the complementation of the mreB mutant and repositioning of PBP1.

Le gène Spatial est exprimé par des cellules hautement polarisées : les cellules épithéliales du thymus, neuronales du système nerveux central et germinales du testicule. La différenciation de ces cellules est accompagnée d'une polarisation de la distribution de Spatial, dans des structures microtubulaires hautement organisées telles que la manchette, le flagelle et la dendrite.Mon projet a porté sur l’identification de la fonction du gène Spatial au niveau du thymus et du cerveau murins. De plus, j’ai été impliquée dans la caractérisation du gène Spatial chez l’homme et l’évaluation de son impact sur la spermatogenèse et l’infertilité humaine.Nos résultats montrent qu’au niveau du thymus, Spatial est détecté tout au long de l’organogenèse thymique jusqu’aux stades adultes. Son profil d’expression correspond à un « promiscuous gene » impliqué dans l’acquisition de la tolérance des lymphocytes T. Au niveau du système nerveux central, Spatial présente une distribution somatodendritique dans les cultures de neurones hippocampiques et son expression est fortement détectée lors de la poussée dendritique. Nous avons montré que le transport de Spatial du corps cellulaire vers les dendrites est dépendant de la kinésine Kif17. De plus, Spatial semble être impliqué dans la formation des dendrites via la voie de signalisation stimulée par le Nerve Growth Factor.Chez l’homme, le gène H-Spatial est fortement exprimé au niveau du testicule et son expression est spécifique de la spermiogenèse, étape de différenciation des spermatides rondes en spermatozoïdes. Chez les patients infertiles asthéno- et/ou tératozoospermiques, présentant des anomalies de mobilité et de forme des spermatozoïdes, le niveau d’ARNm d’H-Spatial est fortement réduit. Ces résultats suggèrent qu’H-Spatial est un marqueur potentiel de l’infertilité masculine.J’ai également participé à la validation des dendrimères PAMAM (poly-amidoamine) comme vecteurs efficaces pour le transfert de siRNA et d’ADN in vitro sur différents lignées cellulaires et in vivo sur des thymus murins. Ce système pourrait être un moyen thérapeutique pour traiter des immunodéficiences liées aux lymphocytes T. / Spatial gene is expressed in highly polarized cells such as, thymic epithelial cells, testicular germ cells and neuronal cells of the central nervous system. The differentiation of these cells is accompanied by the polarized distribution of Spatial in highly organized microtubule structures such as the manchette, the flagellum and dendrites. This project aims to identify the function of Spatial gene in the thymus and in the brain. Moreover, we characterize Spatial gene in humans and evaluate its impact on spermatogenesis and human infertility.Our results showed that, in the thymus, Spatial is detected throughout the thymic development, until adulthood. Its expression profile corresponds to a ‘promiscuous gene’, implicated in the acquisition of T lymphocyte tolerance.At the level of the central nervous system, Spatial showed a somatodendritic distribution in hippocampal neuron cultures. Moreover, its expression was highly detected during dendritic growth. We have also shown that the transport of Spatial from the cell body to the dendrites is dependent on the kinesin Kif17. In addition, our results suggest that Spatial seems to be implemented in dendrite formation by the Nerve Growth Factor mediated signaling pathway.In the humans, H-Spatial is highly expressed in the testis and its expression is specific to spermiogenesis: the phase of differentiation of round spermatids to spermatozoids. In infertile astheno and/or teratozoospermic patients with sperm shape and mobility anomalies, H-Spatial levels were drastically reduced. These results propose H-Spatial as a potential marker for human male infertility.Finally, we have equally participated in the validation of PAMAM (poly-amidoamine) dendrimers as efficient vectors for the transfer of DNA and siRNA in vitro, in different cell lines; and in vivo, in murine thymi. This system could serve as a new therapeutic model for treating diseases linked to T lymphocytes.