| 1. |
- Adolfsson, Karl, et al.
(författare)
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Ingestion of gallium phosphide nanowires has no adverse effect on Drosophila tissue function.
- 2013
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 24:28
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Tidskriftsartikel (refereegranskat)abstract
- Engineered nanoparticles have been under increasing scrutiny in recent years. High aspect ratio nanoparticles such as carbon nanotubes and nanowires have raised safety concerns due to their geometrical similarity to asbestos fibers. III-V epitaxial semiconductor nanowires are expected to be utilized in devices such as LEDs and solar cells and will thus be available to the public. In addition, clean-room staff fabricating and characterizing the nanowires are at risk of exposure, emphasizing the importance of investigating their possible toxicity. Here we investigated the effects of gallium phosphide nanowires on the fruit fly Drosophila melanogaster. Drosophila larvae and/or adults were exposed to gallium phosphide nanowires by ingestion with food. The toxicity and tissue interaction of the nanowires was evaluated by investigating tissue distribution, activation of immune response, genome-wide gene expression, life span, fecundity and somatic mutation rates. Our results show that gallium phosphide nanowires applied through the diet are not taken up into Drosophila tissues, do not elicit a measurable immune response or changes in genome-wide gene expression and do not significantly affect life span or somatic mutation rate.
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| 2. |
- Azevedo, Dulce, et al.
(författare)
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DRhoGEF2 Regulates Cellular Tension and Cell Pulsations in the Amnioserosa during Drosophila Dorsal Closure
- 2011
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:9
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Tidskriftsartikel (refereegranskat)abstract
- Coordination of apical constriction in epithelial sheets is a fundamental process during embryogenesis. Here, we show that DRhoGEF2 is a key regulator of apical pulsation and constriction of amnioserosal cells during Drosophila dorsal closure. Amnioserosal cells mutant for DRhoGEF2 exhibit a consistent decrease in amnioserosa pulsations whereas overexpression of DRhoGEF2 in this tissue leads to an increase in the contraction time of pulsations. We probed the physical properties of the amnioserosa to show that the average tension in DRhoGEF2 mutant cells is lower than wild-type and that overexpression of DRhoGEF2 results in a tissue that is more solid-like than wild-type. We also observe that in the DRhoGEF2 overexpressing cells there is a dramatic increase of apical actomyosin coalescence that can contribute to the generation of more contractile forces, leading to amnioserosal cells with smaller apical surface than wild-type. Conversely, in DRhoGEF2 mutants, the apical actomyosin coalescence is impaired. These results identify DRhoGEF2 as an upstream regulator of the actomyosin contractile machinery that drives amnioserosa cells pulsations and apical constriction.
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| 3. |
- Castillejo-Lopez, Casimiro, et al.
(författare)
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The serine protease Sp7 is expressed in blood cells and regulates the melanization reaction in Drosophila.
- 2005
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Ingår i: Biochemical and Biophysical Research Communications. - : Elsevier BV. - 1090-2104 .- 0006-291X. ; 338:2, s. 1075-1082
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Tidskriftsartikel (refereegranskat)abstract
- Serine proteases play a central role in defense against pathogens by regulating processes such as blood clotting, melanization of injured surfaces, and proteolytic activation of signaling pathways involved in innate immunity. Here, we present the functional characterization of the Drosophila serine protease Sp7 (CG3006) by inducible RNA interference. We show that Sp7 is constitutively expressed in blood cells during embryonic and larval stages. Silencing of the gene impairs the melanization reaction upon injury. Our data demonstrate that Sp7 is required for phenoloxidase activation and its activity is restricted to a subclass of blood cells, the crystal cells. Transcriptional up-regulation of Sp7 was observed after clean, septic injury and in flies expressing an activated form of Toll; however, mutations in the Toll or the IMD pathway did not abolish expression of Sp7, indicating the existence of other regulatory pathways and/or independent basal transcription.
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| 4. |
- Fischer, MG, et al.
(författare)
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The mitotic arrest in response to hypoxia and of polar bodies during early embryogenesis requires Drosophila Mps1
- 2004
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Ingår i: Current Biology. - : Elsevier BV. - 1879-0445 .- 0960-9822. ; 14:22, s. 2019-2024
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Tidskriftsartikel (refereegranskat)abstract
- Mps1 kinase plays an evolutionary conserved role in the mitotic spindle checkpoint [1-8]. This system precludes anaphase onset until all chromosomes have successfully attached to spindle microtubules via their kinetochores [9]. Mps1 overexpression in budding yeast is sufficient to trigger a mitotic arrest, which is dependent on the other mitotic. checkpoint components, Bub1, Bub3, Mad1, Mad2, and Mad3 [3]. Therefore, Mps1 might act at the top of the mitotic checkpoint cascade. Moreover, in contrast to the other mitotic checkpoint components, Mps1 is essential for spindle pole body duplication in budding yeast [10]. Centrosome duplication in mammalian cells might also be controlled by Mps1 [6,11], but the fission yeast homolog is not required for spindle pole body duplication [4]. Our phenotypic characterizations of Mps1 mutant embryos in Drosophila do not reveal an involvement in centrosome duplication, while the mitotic spindle checkpoint is defective in these mutants. In addition, our analyses reveal novel functions. We demonstrate that Mps1 is also required for the arrest of cell cycle progression in response to hypoxia. Finally, we show that Mps1 and the mitotic spindle checkpoint are responsible for the developmental cell cycle arrest of the three haploid products of female meiosis that are not used as the female pronucleus.
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| 5. |
- Gunnar, Erika, 1985-
(författare)
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Regulatory programs controlling profileration during Drosophila nervous system development
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The central nervous system (CNS) is the most complex organ in the body, responsible for complex functions, including thinking, reasoning and memory. The CNS contains cells of many different types, often generated in vast numbers. Hence, CNS development requires precise genetic control of both cell fate and of cell proliferation, to generate the right number of cells, with the proper identity, and in the proper location. The cells also need to make connections with each other for correct signaling and function. This complexity evokes the question of how this is regulated. How does the stem cells, responsible for building the CNS, know how many times to divide, and how does the daughters know which identity to acquire and in which location they shall end up? During Drosophila melanogaster development, the neuroblasts (NBs) are responsible for generating the CNS. In each hemisegment, every NB is unique in identity, and generates a predetermined number of daughters with specific identities. The lineages of different NBs vary in size, but are always the same for each specific NB, and the division modes of each NBs is hence stereotyped. Most NBs start dividing by renewing themselves while generating daughters that will in turn divide once to generate two neurons and/or glia (denoted type I mode). Many, maybe all, NBs later switch to generating daughters that will differentiate directly into a neuron or glia (denoted type 0 mode). This type I>0 switch occurs at different time-points during lineage progression, and influences the total numbers of cells generated from a single NB.The work presented in this thesis aimed at investigating the genetic regulation of proliferation, with particular focus on the type I>0 switch. In the first project, the implication of the Notch pathway on the type I>0 switch was studied. Mutants of the Notch pathway do not switch, and the results show that the Notch pathway regulates the switch by activation of several target genes, both regulators and cell cycle genes. One of the target genes, the E(spl)-C genes, have been difficult to study due to functional redundancy. This study reveals that even though they can functionally compensate for each other, they have individual functions in different lineages. Regarding cell cycle genes, both Notch and E(spl)-C regulate several key cell cycle genes, and molecular analysis indicated that this regulation is direct. In the second project we studied the seq gene, previously identified in a genetic screen. We found that seq controls the type I>0 switch by regulating the key cell cycle genes, but also through interplay with the Notch pathway. Notch and seq stop proliferation, and in the third project we wanted to identify genes that drive proliferation. We found that there is battery of early NB genes, socalled early factors, which activate the cell cycle, and drive NB and daughter proliferation. These are gradually replaced by late regulators, and the interplay between early and late factors acts to achieve precise control of lineage progression.The work presented here increases our understanding of how regulatory programs act to control the development of the CNS; to generate the right number of cells of different identities. These results demonstrate the importance of correct regulation of proliferation in both stem cells and daughters. Problems in this control can result in either an underdeveloped CNS or loss of control such as in cancer. Knowledge about these regulatory programs can contribute to the development of therapeutics against these diseases.
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| 6. |
- Horn, C, et al.
(författare)
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piggyBac-based insertional mutagenesis and enhancer detection as a tool for functional insect genomics
- 2003
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Ingår i: Genetics. - 0016-6731. ; 163:2, s. 647-661
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Tidskriftsartikel (refereegranskat)abstract
- Transposon mutagenesis provides a fundamental tool for functional genomics. Here we present a non-species-specific, combined enhancer detection and binary expression system based on the transposable element piggyBac: For the different components of this insertional mutagenesis system, we used widely applicable transposons and distinguishable broad-range transformation markers, which should enable this system to be operational in nonmodel arthropods. In a pilot screen in Drosophila melanogaster, piggyBac mutator elements on the X chromosome were mobilized in males by a Hennes-based jumpstarter element providing pigpBac transposase activity under control of the alpha1-tubulin promoter. As primary reporters in the pigoBac mutator elements, we employed the heterologous transactivators GAL4Delta or tTA. To identify larval and adult enhancer detectors, strains carrying UASp-EYFP or TRE-EYFP as secondary reporter elements were used. Tissue-specific enhancer activities were readily observed in the GAL4Delta/UASp-based systems, but only rarely in the tTA/TRE system. Novel autosomal insertions were recovered with an average jumping rate of 80%. Of these novel insertions, 3.8% showed homozygous lethality, which was reversible by pigoBac excision. Insertions were found in both coding and noncoding regions of characterized genes and also in noncharacterized and non-P-targeted CG-number genes. This indicates that piggyBac will greatly facilitate the intended saturation mutagenesis in Drosophila.
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| 7. |
- Häcker, Udo, et al.
(författare)
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Heparan sulphate proteoglycans: the sweet side of development.
- 2005
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Ingår i: Nature Reviews. Molecular Cell Biology. - : Springer Science and Business Media LLC. - 1471-0072 .- 1471-0080. ; 6:7, s. 530-541
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Forskningsöversikt (refereegranskat)abstract
- Pattern formation during development is controlled to a great extent by a small number of conserved signal transduction pathways that are activated by extracellular ligands such as Hedgehog, Wingless or Decapentaplegic. Genetic experiments have identified heparan sulphate proteoglycans (HSPGs) as important regulators of the tissue distribution of these extracellular signalling molecules. Several recent reports provide important new insights into the mechanisms by which HSPGs function during development.
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| 8. |
- Häcker, Udo, et al.
(författare)
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piggyBac-based insertional mutagenesis in the presence of stably integrated P elements in Drosophila
- 2003
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Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 100:13, s. 7720-7725
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Tidskriftsartikel (refereegranskat)abstract
- P element-mediated mutagenesis has been used to disrupt an estimated 25% of genes essential for Drosophila adult viability. Mutation of all genes in the fly genome, however, poses a problem, because P elements show significant hotspots of integration. In addition, advanced screening scenarios often require the use of P element-based tools like the generation of germ-line mosaics using FLP recombinase-mediated recombination or gene misexpression using the UAS/Gal4 system. These techniques are P element-based and can therefore not be combined with the use of P elements as mutagenic agents. To circumvent these limitations, we have developed an insertional mutagenesis system using non-P element transposons. An enhanced yellow fluorescent protein-marked piggyBac-based mutator element was mobilized by a piggyBac specific transposase source expressed from a Hermes-based jumpstarter transposon marked with enhanced cyan fluorescent protein. In a pilot screen, we have generated 798 piggyBac insertions on FRT bearing third chromosomes of which 9% have sustained a putatively piggyBac-related lethal hit. The FRTs present on the target chromosome remained stably integrated during the screen and could subsequently be used to generate germ-line clones associated with maternal and zygotic phenotypes. PCR-based analysis of insertion loci shows that 57% of the insertions are in genes for which no P element insertions have been reported. Our data demonstrate the potential of this technique to facilitate the quest for saturation mutagenesis of the Drosophila genome. The system is Drosophila nonspecific and potentially applicable in a broad spectrum of nonmodel organisms.
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| 9. |
- Lueders, Florian, et al.
(författare)
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Slalom encodes an adenosine 3'-phosphate 5'-phosphosulfate transporter essential for development in Drosophila.
- 2003
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Ingår i: EMBO Journal. - : Wiley. - 1460-2075. ; 22:14, s. 3635-3644
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Tidskriftsartikel (refereegranskat)abstract
- Sulfation of all macromolecules entering the secretory pathway in higher organisms occurs in the Golgi and requires the high-energy sulfate donor adenosine 3'-phosphate 5'-phosphosulfate. Here we report the first molecular identification of a gene that encodes a transmembrane protein required to transport adenosine 3'-phosphate 5'-phosphosulfate from the cytosol into the Golgi lumen. Mutations in this gene, which we call slalom, display defects in Wg and Hh signaling, which are likely due to the lack of sulfation of glycos aminoglycans by the sulfotransferase sulfateless. Analysis of mosaic mutant ovaries shows that sll function is also essential for dorsal–ventral axis determination, suggesting that sll transports the sulfate donor required for sulfotransferase activity of the dorsal–ventral determinant pipe.
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| 10. |
- Mulinari, Shai, et al.
(författare)
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DRhoGEF2 and Diaphanous Regulate Contractile Force during Segmental Groove Morphogenesis in the Drosophila Embryo.
- 2008
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Ingår i: Molecular Biology of the Cell. - 1939-4586. ; 19, s. 1883-1892
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Tidskriftsartikel (refereegranskat)abstract
- Monitoring Editor: Marianne Bronner-Fraser Morphogenesis of the Drosophila embryo is associated with dynamic rearrangement of the Actin cytoskeleton mediated by small GTPases of the Rho family. These GTPases act as molecular switches that are activated by guanine nucleotide exchange factors. One of these factors, DRhoGEF2, plays an important role in the constriction of Actin filaments during pole cell formation, blastoderm cellularization and invagination of the germlayers. Here we show that DRhoGEF2 is equally important during morphogenesis of segmental grooves, which become apparent as tissue infoldings during midembryogenesis. Examination of DRhoGEF2-mutant embryos indicates a role for DRhoGEF2 in the control of cell shape changes during segmental groove morphogenesis. Overexpression of DRhoGEF2 in the ectoderm recruits Myosin II to the cell cortex and induces cell contraction. At groove regression DRhoGEF2 is enriched in cells posterior to the groove that undergo apical constriction indicating that groove regression is an active process. We further show that the Formin Diaphanous is required for groove formation and strengthens cell junctions in the epidermis. Morphological analysis suggests that Dia regulates cell shape in a way distinct from DRhoGEF2. We propose that DRhoGEF2 acts through Rho1 to regulate acto-myosin constriction but not Diaphanous-mediated F-Actin nucleation during segmental groove morphogenesis.
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