DaPKC-dependent phosphorylation of Crumbs is required for epithelial cell polarity in Drosophila

Both in Drosophila and vertebrate epithelial cells, the establishment of apicobasal polarity requires the apically localized, membrane-associated Par-3–Par-6–aPKC protein complex. In Drosophila, this complex colocalizes with the Crumbs–Stardust (Sdt)–Pals1-associated TJ protein (Patj) complex. Genetic and molecular analyses suggest a functional relationship between them. We show, by overexpression of a kinase-dead Drosophila atypical PKC (DaPKC), the requirement for the kinase activity of DaPKC to maintain the position of apical determinants and to restrict the localization of basolateral ones. We demonstrate a novel physical interaction between the apical complexes, via direct binding of DaPKC to both Crb and Patj, and identify Crumbs as a phosphorylation target of DaPKC. This phosphorylation of Crumbs is functionally significant. Thus, a nonphosphorylatable Crumbs protein behaves in vivo as a dominant negative. Moreover, the phenotypic effect of overexpressing wild-type Crumbs is suppressed by reducing DaPKC activity. These results provide a mechanistic framework for the functional interaction between the Par-3–Par-6–aPKC and Crumbs–Sdt–Patj complexes based in the posttranslational modification of Crb by DaPKC

Drosophila Araucan and Caupolican Integrate Intrinsic and Signalling Inputs for the Acquisition by Muscle Progenitors of the Lateral Transverse Fate

A central issue of myogenesis is the acquisition of identity by individual muscles. In Drosophila, at the time muscle progenitors are singled out, they already express unique combinations of muscle identity genes. This muscle code results from the integration of positional and temporal signalling inputs. Here we identify, by means of loss-of-function and ectopic expression approaches, the Iroquois Complex homeobox genes araucan and caupolican as novel muscle identity genes that confer lateral transverse muscle identity. The acquisition of this fate requires that Araucan/Caupolican repress other muscle identity genes such as slouch and vestigial. In addition, we show that Caupolican-dependent slouch expression depends on the activation state of the Ras/Mitogen Activated Protein Kinase cascade. This provides a comprehensive insight into the way Iroquois genes integrate in muscle progenitors, signalling inputs that modulate gene expression and protein activity

Interacción de los factores de elongación un aminoacil-tRNA erronéamente codificado y antibioticos amonoglicosidicos con el Ribosoma de Escherichia Coli

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid. Facultad de Ciencias. Departamento de Biología Molecular. Fecha de lectura: 5 de Marzo 198

Cell cycling and patterned cell proliferation in the wing primordium of Drosophila.

The pattern of cell proliferation in the Drosophila imaginal wing primordium is spatially and temporally heterogeneous. Direct visualization of cells in S, G2, and mitosis phases of the cell cycle reveals several features invariant throughout development. The fraction of cells in the disc in the different cell cycle stages is constant, the majority remaining in G1. Cells in the different phases of the cell cycle mainly appear in small synchronic clusters that are nonclonally derived but result from changing local cell-cell interactions. Cluster synchronization occurs before S and in the G2/M phases. Rates of cell division are neither constant nor clonal features. Cell cycle progression is linear rather than concentric. Clusters appear throughout the disc but with symmetries related to presumptive wing patterns, compartment boundaries, and vein clonal restrictions.Peer reviewe

Cell cycling and patterned cell proliferation in the Drosophila wing during metamorphosis.

In metamorphosing wing discs, progression through the cell cycle takes place, as in larval discs, in nonclonally derived clusters of cells synchronized in the same cell cycle stage. Contrary to early discs, there are temporal and spatial heterogeneities in cell proliferation associated with wing margin, vein, intervein, and middle intervein territories. Within these territories, there are no indications of a wave progression of the cell cycle. Mitotic orientations are, as in early discs, at random but there is a preferential allocation of postmitotic cells along the proximodistal axis, thus explaining the elongated shape of the resulting clones along this axis. Shapes of clones in mature discs and in evaginated wings are similar, thus excluding major morphogenetic movements during evagination. After the proliferative period, all the cells are arrested in G1 phase. The final number of cells of the wing is fixed independently of experimental perturbations that alter the cell division schedule. These results are discussed in the context of a model of wing morphogenesis.Peer reviewe

Regulated Crb accumulation controls apical constriction and invagination in Drosophila tracheal cells

Many epithelial tissues undergo extensive remodelling during morphogenesis. How their epithelial features, such as apicobasal polarity or adhesion, are maintained and remodelled and how adhesion and polarity proteins contribute to morphogenesis are two important questions in development. Here, we approach these issues by investigating the role of the apical determinant protein Crumbs (Crb) during the morphogenesis of the embryonic Drosophila tracheal system. Crb accumulates differentially throughout tracheal development and is required for different tracheal events. The earliest requirement for Crb is for tracheal invagination, which is preceded by an enhanced accumulation of Crb in the invagination domain. There, Crb, acting in parallel with the epidermal growth factor receptor (Egfr) pathway, is required for tracheal cell apical constriction and for organising an actomyosin complex, which we propose is mediated by Crb recruitment of moesin (Moe). The ability of a Crb isoform unable to rescue polarity in crb mutants to otherwise rescue their invagination phenotype, and the converse inability of a FERM-binding domain mutant Crb to rescue faulty invagination, support our hypothesis that it is the absence of Crb-dependent Moe enrichment, and not the polarity defect, that mainly underlies the crb invagination phenotype. This hypothesis is supported by the phenotype of lethal giant larvae (lgl); crb double mutants. These results unveil a link between Crb and the organisation of the actin cytoskeleton during morphogenesis.A.L. acknowledges a contract from the ‘Juan de la Cierva’ programme and S.S. a contract from the ‘Ramón y Cajal’ programme. This work was supported by funds from the Ministerio de Educación y Ciencia to M.L. (BFU2006-09515/BMC, PIE200720I019) and to S.C. (BFU2008-03762) and from the Programme Consolider 2007 (CSD2007-00008) project. An institutional grant from Fundación Ramón Areces to the CBMSO is acknowledged.Peer Reviewe

Half a century of neural prepatterning: the story of a few bristles and many genes

12 páginas, 6 figuras.In 1954, Curt Stern proposed the concept of the neural prepattern, meaning the underlying positional information in an undifferentiated epithelium that determined where neural differentiation could take place. Subsequent work gave a molecular basis to this concept, which was equated to a combination of transcription factors deployed in partially overlapping spatial domains that regulated proneural genes and, thereby, neural differentiation. Here, we review the work that, in the past few years, has identified many prepattern genes and has disclosed that their function is not limited to the regulation of proneural genes.Grants from Dirección General de Investigación Científica y Técnica, Comunidad Autónoma de Madrid, and an institutional grant from Fundación Ramón Areces to the Centro de Biología Molecular Severo Ochoa are acknowledged.Peer reviewe

An integrated system for the development of Latvian Treebank

Darbā aplūkota sintaktiski anotētu korpusu (treebank) izstrādes problemātika ar mērķi radīt stabilu tehnoloģisko pamatu sintaktiski anotēta latviešu valodas korpusa izstrādei. Darbā apskatīti klasiskie sintaktiskās analīzes (reprezentācijas) modeļi — vārdkopu struktūru un atkarību gramatikas — un SemTi-Kamola hibrīdais gramatikas modelis valodām ar relatīvi brīvu vārdu secību. Darbā analizēta pasaulē lielāko sintaktiski anotēto korpusu pieredze un formāti, īpašu uzmanību pievēršot vadošā atkarību pieejā balstītā korpusa — Prāgas atkarību korpusa (Prague Dependency Treebank — PDT) — vairāklīmeņu anotāciju struktūrai. Darbā izstrādāts SemTi-Kamola gramatikas modeļa paplašinājums, kas nodrošina sintaktiski neierobežotu teikumu anotēšanu. Izveidots PML (Prague Markup Language) profils SemTi-Kamols datu aprakstīšanai starptautiski atzītā mašīnlasāmā formā. Izstrādātais XML balstītais datu formāts ir integrēts ar SemTi-Kamola automātiskās sintaktiskās analīzes rīkiem un vizuālo kokveida datu struktūru redaktoru TrEd, kas ir izmantots PDT izveidē. Tādejādi ir radīts tehnoloģiskais un metodoloģiskais pamats latviešu valodas sintaktiski anotēta korpusa radīšanai — vide (integrētu rīku un formātu kopums), kas ļauj tekstus formāli anotēt atbilstoši SemTi-Kamols modelim, bet neprasa specifiskas tehnoloģiju zināšanas no lietotāja (valodnieka). Izstrādātā vide tiek sekmīgi pielietota praksē — izveidotas anotācijas apmēram 200 teikumiem.The problem of developing syntactically annotated text corpus (treebank) is considered in this work. The aim of this work is to develop a sound technological base for developing Latvian Treebank. General approaches of the syntactic analysis are described — the phrase structure approach and the dependency approach. The SemTi-Kamols hybrid dependency based grammar for languages with rather free word order is also described. The experience of world’s largest treebanks, particularly Prague Dependency Treebank (PDT) and its multi-level annotation structure, is analysed as well. An extension of the SemTi-Kamols model has been developed to cover syntactically unrestricted sentences of Latvian language. A PML (Prague Markup Language) profile for displaying SemTi-Kamols data in the internationally acknowledged machine-readable form has been developed. This XML based format is integrated with SemTi-Kamols parser and visual tree editor TrEd originally developed for PDT. The main result of this work is the technological and methodological base for creating Latvian Treebank — a framework consisting of integrated tools and formats that allows to annotate treebank data accordingly to the SemTi-Kamols model without requiring deep technological knowledge from the end-user (linguist). Approximately 200 sentences have been annotated using the developed framework