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157 Publications

Showing 51-60 of 157 results
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    08/13/09 | Too fat to fly? New brain circuits regulate obesity in Drosophila.
    Kaun KR, Heberlein U
    Neuron. 2009 Aug 13;63(3):279-81. doi: 10.1016/j.neuron.2009.07.023

    In mammals, fat store levels are regulated by brain centers that control food intake and metabolism. A new study by Al-Anzi and colleagues in this issue of Neuron identifies neurons with similar functions in Drosophila, further establishing the fly as a legitimate model to study obesity.

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    Kainmueller Lab
    08/07/09 | Automatic Extraction of Anatomical Landmarks From Medical Image Data: An Evaluation of Different Methods
    Kainmueller D, Hans-Christian Hege , Heiko Seim , Markus Heller , Stefan Zachow

    This work presents three different methods for automatic detection of anatomical landmarks in CT data, namely for the left and right anterior superior iliac spines and the pubic symphysis. The methods exhibit different degrees of generality in terms of portability to other anatomical landmarks and require a different amount of training data. The ſrst method is problem-speciſc and is based on the convex hull of the pelvis. Method two is a more generic approach based on a statistical shape model including the landmarks of interest for every training shape. With our third method we present the most generic approach, where only a small set of training landmarks is required. Those landmarks are transferred to the patient speciſc geometry based on Mean Value Coordinates (MVCs). The methods work on surfaces of the pelvis that need to be extracted beforehand. We perform this geometry reconstruction with our previously introduced fully automatic segmentation framework for the pelvic bones. With a focus on the accuracy of our novel MVC-based approach, we evaluate and compare our methods on 100 clinical CT datasets, for which gold standard landmarks were deſned manually by multiple observers.

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    08/04/09 | Rapid evolution of sex pheromone-producing enzyme expression in Drosophila.
    Shirangi TR, Dufour HD, Williams TM, Carroll SB
    PLoS Biology. 2009 Aug 4;7(8):e1000168. doi: 10.1371/journal.pbio.1000168

    A wide range of organisms use sex pheromones to communicate with each other and to identify appropriate mating partners. While the evolution of chemical communication has been suggested to cause sexual isolation and speciation, the mechanisms that govern evolutionary transitions in sex pheromone production are poorly understood. Here, we decipher the molecular mechanisms underlying the rapid evolution in the expression of a gene involved in sex pheromone production in Drosophilid flies. Long-chain cuticular hydrocarbons (e.g., dienes) are produced female-specifically, notably via the activity of the desaturase DESAT-F, and are potent pheromones for male courtship behavior in Drosophila melanogaster. We show that across the genus Drosophila, the expression of this enzyme is correlated with long-chain diene production and has undergone an extraordinary number of evolutionary transitions, including six independent gene inactivations, three losses of expression without gene loss, and two transitions in sex-specificity. Furthermore, we show that evolutionary transitions from monomorphism to dimorphism (and its reversion) in desatF expression involved the gain (and the inactivation) of a binding-site for the sex-determination transcription factor, DOUBLESEX. In addition, we documented a surprising example of the gain of particular cis-regulatory motifs of the desatF locus via a set of small deletions. Together, our results suggest that frequent changes in the expression of pheromone-producing enzymes underlie evolutionary transitions in chemical communication, and reflect changing regimes of sexual selection, which may have contributed to speciation among Drosophila.

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    08/01/09 | A Drosophila resource of transgenic RNAi lines for neurogenetics.
    Ni J, Liu L, Binari R, Hardy R, Shim H, Cavallaro A, Booker M, Pfeiffer BD, Markstein M, Wang H, Villalta C, Laverty TR, Perkins LA, Perrimon N
    Genetics. 2009 Aug;182(4):1089-100. doi: 10.1534/genetics.109.103630

    Conditional expression of hairpin constructs in Drosophila is a powerful method to disrupt the activity of single genes with a spatial and temporal resolution that is impossible, or exceedingly difficult, using classical genetic methods. We previously described a method (Ni et al. 2008) whereby RNAi constructs are targeted into the genome by the phiC31-mediated integration approach using Vermilion-AttB-Loxp-Intron-UAS-MCS (VALIUM), a vector that contains vermilion as a selectable marker, an attB sequence to allow for phiC31-targeted integration at genomic attP landing sites, two pentamers of UAS, the hsp70 core promoter, a multiple cloning site, and two introns. As the level of gene activity knockdown associated with transgenic RNAi depends on the level of expression of the hairpin constructs, we generated a number of derivatives of our initial vector, called the "VALIUM" series, to improve the efficiency of the method. Here, we report the results from the systematic analysis of these derivatives and characterize VALIUM10 as the most optimal vector of this series. A critical feature of VALIUM10 is the presence of gypsy insulator sequences that boost dramatically the level of knockdown. We document the efficacy of VALIUM as a vector to analyze the phenotype of genes expressed in the nervous system and have generated a library of 2282 constructs targeting 2043 genes that will be particularly useful for studies of the nervous system as they target, in particular, transcription factors, ion channels, and transporters.

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    Cardona LabSaalfeld Lab
    08/01/09 | CATMAID: collaborative annotation toolkit for massive amounts of image data.
    Saalfeld S, Cardona A, Hartenstein V, Tomancak P
    Bioinformatics. 2009 Aug 1;25(15):1984-6. doi: 10.1093/bioinformatics/btp266

    SUMMARY: High-resolution, three-dimensional (3D) imaging of large biological specimens generates massive image datasets that are difficult to navigate, annotate and share effectively. Inspired by online mapping applications like GoogleMaps, we developed a decentralized web interface that allows seamless navigation of arbitrarily large image stacks. Our interface provides means for online, collaborative annotation of the biological image data and seamless sharing of regions of interest by bookmarking. The CATMAID interface enables synchronized navigation through multiple registered datasets even at vastly different scales such as in comparisons between optical and electron microscopy. AVAILABILITY: http://fly.mpi-cbg.de/catmaid.

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    Riddiford Lab
    08/01/09 | Elucidation of the regulation of an adult cuticle gene Acp65A by the transcription factor Broad.
    Cui H, Lestradet M, Bruey-Sedano N, Charles J, Riddiford LM
    Insect Molecular Biology. 2009 Aug;18(4):421-9. doi: 10.1111/j.1365-2583.2009.00889.x

    Broad (BR), an ecdysone-inducible transcription factor, is a major determinant of the pupal stage. The misexpression of BR-Z1 isoform (BR-Z1) during adult development of Drosophila melanogaster prevents the expression of the adult cuticle protein 65A gene (Acp65A). We found that the proximal 237 bp of the 5’ flanking region of Acp65A were sufficient to mediate this suppression. A targeted point mutation of a putative BR-Z1 response element (BRE) within this region showed that it was not involved. Drosophila hormone receptor-like 38 (DHR38) is required for Acp65A expression. We found that BR-Z1 repressed DHR38 expression and that BR’s inhibition of Acp65A expression was rescued by exogenous expression of DHR38. Thus, BR-Z1 suppresses Acp65A expression by preventing the normal up-regulation of DHR38 at the time of adult cuticle formation.

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    Cardona Lab
    08/01/09 | Neuronal fiber tracts connecting the brain and ventral nerve cord of the early Drosophila larva.
    Cardona A, Larsen C, Hartenstein V
    The Journal of Comparative Neurology. 2009 Aug 1;515(4):427-40. doi: 10.1002/cne.22086

    By using a combination of dye injections, clonal labeling, and molecular markers, we have reconstructed the axonal connections between brain and ventral nerve cord of the first-instar Drosophila larva. Out of the approximately 1,400 neurons that form the early larval brain hemisphere, less than 50 cells have axons descending into the ventral nerve cord. Descending neurons fall into four topologically defined clusters located in the anteromedial, anterolateral, dorsal, and basoposterior brain, respectively. The anterolateral cluster represents a lineage derived from a single neuroblast. Terminations of descending neurons are almost exclusively found in the anterior part of the ventral nerve cord, represented by the gnathal and thoracic neuromeres. This region also contains small numbers of neurons with axons ascending into the brain. Terminals of the ascending axons are found in the same basal brain regions that also contain descending neurons. We have mapped ascending and descending axons to the previously described scaffold of longitudinal fiber tracts that interconnect different neuromeres of the ventral nerve cord and the brain. This work provides a structural framework for functional and genetic studies addressing the control of Drosophila larval behavior by brain circuits.

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    08/01/09 | New genetic tools for cell lineage analysis in Drosophila.
    Lee T
    Nature Methods. 2009 Aug;6(8):566-8. doi: 10.1038/nmeth0809-566

    Real-time lineage tracing in flies gets a boost with three techniques to specifically label a progenitor’s daughter cells.

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    Spruston LabMenon Lab
    07/30/09 | Synapse distribution suggests a two-stage model of dendritic integration in CA1 pyramidal neurons.
    Katz Y, Menon V, Nicholson DA, Geinisman Y, Kath WL, Spruston N
    Neuron. 2009 Jul 30;63(2):171-7. doi: 10.1016/j.neuron.2009.06.023

    Competing models have been proposed to explain how neurons integrate the thousands of inputs distributed throughout their dendritic trees. In a simple global integration model, inputs from all locations sum in the axon. In a two-stage integration model, inputs contribute directly to dendritic spikes, and outputs from multiple branches sum in the axon. These two models yield opposite predictions of how synapses at different dendritic locations should be scaled if they are to contribute equally to neuronal output. We used serial-section electron microscopy to reconstruct individual apical oblique dendritic branches of CA1 pyramidal neurons and observe a synapse distribution consistent with the two-stage integration model. Computational modeling suggests that the observed synapse distribution enhances the contribution of each dendritic branch to neuronal output.

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    07/30/09 | Tweek, an evolutionarily conserved protein, is required for synaptic vesicle recycling.
    Verstreken P, Ohyama T, Haueter C, Habets RL, Lin YQ, Swan LE, Ly CV, Venken KJ, De Camilli P, Bellen HJ
    Neuron. 2009 Jul 30;63(2):203-15. doi: 10.1016/j.neuron.2009.06.017

    Synaptic vesicle endocytosis is critical for maintaining synaptic communication during intense stimulation. Here we describe Tweek, a conserved protein that is required for synaptic vesicle recycling. tweek mutants show reduced FM1-43 uptake, cannot maintain release during intense stimulation, and harbor larger than normal synaptic vesicles, implicating it in vesicle recycling at the synapse. Interestingly, the levels of a fluorescent PI(4,5)P(2) reporter are reduced at tweek mutant synapses, and the probe is aberrantly localized during stimulation. In addition, various endocytic adaptors known to bind PI(4,5)P(2) are mislocalized and the defects in FM1-43 dye uptake and adaptor localization are partially suppressed by removing one copy of the phosphoinositide phosphatase synaptojanin, suggesting a role for Tweek in maintaining proper phosphoinositide levels at synapses. Our data implicate Tweek in regulating synaptic vesicle recycling via an action mediated at least in part by the regulation of PI(4,5)P(2) levels or availability at the synapse.

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