Academic literature on the topic 'Lin-3'

In this thesis, we mainly consider two problems. First, we study the SU(3) Toda system. Let (M,g) be a compact Riemann surface with volume 1, h₁ and h₂ be a C¹ positive function on M and p1; p2 ∈ ℝ⁺. The SU(3) Toda system is the following one on the compact surface M [Formula and equation omitted] where ∆ is the Beltrami-Laplace operator, αq ≥ 0 for every q ∈ S₁, S₁ ⊂ M, Bq ≥ 0 for every q ∈ S₂,S₂ ⊂ M and q is the Dirac measure at q ∈ M. We initiate the program for computing the Leray-Schauder topological degree of SU(3) Toda system and succeed in obtaining the degree formula for p1 ∈ (0,4π)(4π,8π), p2 ∉ 4πℕ when S₁ = S₂ = 0. Second, we consider the following nonlinear elliptic Neumann problem {∆u-μu +uq =0 in Ω,u > 0 in Ω,au/av=0 on aΩ. where q=n+2/n-2, μ > 0 and Ω is a smooth and bounded domain in ℝn. Lin and Ni (1986) conjectured that for μ small, all solutions are constants. In the second part of this thesis, we will show that this conjecture is false for a general domain in n = 4, 6 by constructing a nonconstant solution.<br>Science, Faculty of<br>Mathematics, Department of<br>Graduate

Caenorhabditis elegans est un organisme modèle couramment utilisé pour étudier les processus de développement tels que la formation de la vulve. Ce processus repose sur l'induction précise des cellules qui donnent naissance à la vulve. Les destins cellulaires résultants sont organisés en un motif caractéristique, qui est conservé tout au long du Caenorhabditis et des nématodes rhabditides. En contraste avec cette conservation des cellules vulvaires, ma thèse présente deux axes d'étude qui ont révélé des signatures d'évolution des voies de développement contrôlant l'induction vulvaire. Dans le premier, je présente un changement des motifs cis-régulateurs nécessaires à l'expression cellulaire spécifique de lin-3 (EGF), un gène codant pour la molécule de signalisation qui induit le destin des cellules de la vulve. Les trois sites de liaison aux facteurs de transcription requis pour l'expression de lin-3 chez C. elegans ne sont observés que chez les espèces du groupe Elegans. En utilisant des techniques de FISH à molécule unique et d'édition de génome, je montre que le remplacement des sites endogènes de C. elegans par un fragment de 58 pb contenant un seul site (provenant de C. angaria) produit des niveaux d'ARNm de type sauvage de type lin-3. Je conclus que l'évolution compensatoire pour l'exigence de sites de liaison de C. elegans s'est produite en cis. Dans la deuxième partie de mon étude, j'ai utilisé une approche de cartographie par séquençage et une collection de mutants de la vulve chez Oscheius tipulae, voisin de C. elegans dans le clade rhabditid, afin d'identifier les mutations dans les gènes agissant sur la spécification du modèle de destin des cellules de la vulve. La seule mutation collectée pour rendre les animaux sans vulve correspond à une délétion de la région cis-régulatrice contrôlant l'expression de O. tipulae lin-3, ce que j'ai confirmé par l'édition du génome de CRISPR / Cas9. Les mutants présentant un excès d'induction de la vulve portent des lésions moléculaires dans la voie plexin / semaphorin, un système de signalisation cellulaire qui, selon moi, agit dans le positionnement antéropostérieur des cellules donnant lieu à la vulve par analyse microscopique. Enfin, d’autres animaux d’O. tipulae dont le destin de cellules vulvaires est perturbé présentent des mutations dans des composants de la voie Wnt; pour cette raison, j'ai étudié les profils d'expression des ligands Wnt d'O. tipulae et révélé leur conservation avec C. elegans. Ces deux études mettent en évidence le processus de dérèglement du système de développement (DSD) en tant que processus évolutif qui se produit lors de la formation de la vulve sur des nématodes rhabditides<br>Caenorhabditis elegans is a model organism commonly used to study developmental processes such as vulva formation. This process relies on the precise fate induction of the cells that give rise to the vulva. The resultant cellular fates are arranged into a characteristic pattern, which is conserved across the vulva development of Caenorhabditis and rhabditid nematodes. In contrast to this extensive conservation of the vulval cell fate pattern, my thesis presents two lines of study that revealed signatures of evolution in developmental pathways controlling vulval induction. In the first one, I present a turnover of cis-regulatory motifs required for the cell-specific expression of lin- 3 (EGF), a gene coding for the signalling molecule which induces vulva cell fates. The three transcription factor binding sites required for lin-3 expression in C. elegans are observed only in species of the Elegans group. Using single-molecule FISH and genome editing techniques, I show that the replacement of the endogenous C. elegans binding sites by a 58 bp fragment containing a single site (coming from C. angaria), produces wild-type mRNA levels of lin-3. I conclude that compensatory evolution for the requirement of C. elegans binding sites occurred in cis. In the second line of study, I used a mapping-bysequencing approach and a collection of vulva mutants in Oscheius tipulae, a neighbour of C. elegans in the rhabditid clade, to identify mutations in genes acting on vulva cell fate pattern specification. The only collected mutation to render animals vulvaless corresponds to a deletion of the cis-regulatory region controlling the expression of O. tipulae lin-3, which I confirmed by CRISPR/Cas9 genome editing. Mutants with an excess of vulva induction carry molecular lesions in the plexin/semaphorin pathway, a cell signalling system which I show to act in the antero-posterior positioning of the cells giving rise to the vulva by microscopic analysis. Finally, other O. tipulae animals with disrupted vulval cell fate pattern hold mutations in components of the Wnt pathway; for this reason, I investigated the expression profiles of Wnt ligands of O. tipulae and revealed their conservation with C. elegans. Both of these studies highlight the process of Developmental System Drift (DSD) as an evolutionary process occurring on vulva formation of rhabditid nematodes

Connues pour leur forte teneur en huile, oméga 3, antioxydants et fibres, les graines de lin sont de plus en plus demandées par les industries. D’où l’importance de contrôler leurs productions. Le but de ce travail est d’étudier l’effet des paramètres environnementaux et de la variété sur la composition de la graine de lin et sur le procédé ultérieur de pressage. Pour cela dix variétés de lin oléagineux ont été cultivées sur deux sites différents (Picardie et centre de la France) au cours des années 2011, 2012 et 2013. L’étude a révélé un fort effet variétal sur les teneurs en huile, C18:3, amidon et le PMG tandis que le lieu de culture n’a affecté que la teneur en lipides et amidon. L’effet année a quant à lui été marqué pour le PMG, les teneurs en protéines, lipides et C18:3. Le pressage des graines précédemment caractérisées a montré une forte corrélation entre teneur protéines et rendement. Afin d’améliorer le processus d'expression, le dépelliculage des graines de lin avant le pressage a été envisagé. Ainsi, l’étude du pressage des graines de lin sur presse hydraulique et presses continue montre la possibilité du pressage des graines dépelliculées. Une concordance entre les performances de pressage à l’échelle laboratoire et à l’échelle pilote a été obtenue pour les graines entières et dépelliculées ce qui laisse présager une transposition possible vers l’échelle industrielle<br>Flaxseed is known for their high oil content, omega 3, antioxidants and fiber. To meet growing demand, this requires controlling their production. The aim of this work is to study the effect of environmental factors and cultivar on linseed composition and subsequent pressing process. Ten linseed cultivars were grown in two different locations (north and south of France) during years 2011, 2012 and 2013. Every year have been characterized in terms of pluviometry, sunshine hours and degree days, each climatic factor has been cumulated from flowering to harvest. A strong impact of cultivar on oil, C18:3 and starch content has been noticed whereas the growing location has only affected the starch and lipid contents. Year effect has been recorded on thousand kernel weight, proteins, oil, C18:3 and starch content. Oil expression using the seeds previously characterized has exhibited a strong correlation between protein content and oil yield. To improve the pressing process, dehulling flax seeds before pressing was considered. The study of the pressing flax seeds on hydraulic and continuous press shows the possibility of pressing the dehulling flaxseeds. The concordance between the pressing performance at the laboratory scale and pilot scale was highlighted for the whole and dehulled seeds. This could be suggests a possible transposition to the industrial scale

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2011.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (p. 236-259).<br>The class A and B synthetic multivulva (synMuv) genes of C. elegans redundantly antagonize an EGF/Ras pathway to prevent ectopic vulval induction. The class B synMuv genes encode many proteins known to remodel chromatin and repress transcription. The class A synMuv genes likely also function in transcription, although their specific molecular functions are unknown. We have identified a class A synMuv mutation in the promoter of lin-3 EGF, revealing that lin-3 is the key biological target of the class A synMuv genes in vulval development. Using FISH with single mRNA molecule resolution, we found that class AB synMuv double mutants exhibit widespread ectopic lin-3 expression. Our results show that lin-3 EGF is normally expressed in the germline, and many class B synMuv genes have previously been implicated in inhibiting germline fates in somatic cells. We propose that the class A synMuv genes specifically repress ectopic lin-3 EGF expression through a site in the lin-3 promoter and the class B synMuv genes either directly or indirectly repress lin-3 as a consequence of their role in regulating the germline/soma distinction. The class A and B synMuv genes had previously been thought of as two parallel pathways, but we have found that each of those pathways is actually composed of multiple parallel pathways. While class AB synMuv double mutants have a strong Muv phenotype, most class AA synMuv double mutants exhibit a weak Muv phenotype, and most pairs of class B synMuv mutants can enhance each other in sensitized backgrounds, indicating that most genes within a class can function in parallel. We also found that some pairs of synMuv genes cannot act in parallel, indicating that they function together to repress ectopic lin-3 expression. We also report the molecular characterization of the class A synMuv gene lin-38 and the identification of mcd-1 as a class A synMuv gene. lin-38 and mcd-1 encode paralogous zinc-finger proteins. Unlike previously studied class A synMuv genes that function specifically in vulval development by repressing lin-3, both lin-38 and mcd-1 control multiple aspects of development by regulating target genes other than lin-3.<br>by Adam M. Saffer.<br>Ph.D.