Main Menu (Mobile)- Block

Main Menu - Block

janelia7_blocks-janelia7_fake_breadcrumb | block
Lee Tzumin Lab / Publications
general_search_page-panel_pane_1 | views_panes

8 Publications

Showing 1-8 of 8 results
Your Criteria:
    07/22/10 | Phenotypic robustness conferred by apparently redundant transcriptional enhancers.
    Frankel N, Davis GK, Vargas D, Wang S, Payre F, Stern DL
    Nature. 2010 Jul 22;466(7305):490-3. doi: 10.1038/nature09158

    Genes include cis-regulatory regions that contain transcriptional enhancers. Recent reports have shown that developmental genes often possess multiple discrete enhancer modules that drive transcription in similar spatio-temporal patterns: primary enhancers located near the basal promoter and secondary, or ’shadow’, enhancers located at more remote positions. It has been proposed that the seemingly redundant activity of primary and secondary enhancers contributes to phenotypic robustness. We tested this hypothesis by generating a deficiency that removes two newly discovered enhancers of shavenbaby (svb, a transcript of the ovo locus), a gene encoding a transcription factor that directs development of Drosophila larval trichomes. At optimal temperatures for embryonic development, this deficiency causes minor defects in trichome patterning. In embryos that develop at both low and high extreme temperatures, however, absence of these secondary enhancers leads to extensive loss of trichomes. These temperature-dependent defects can be rescued by a transgene carrying a secondary enhancer driving transcription of the svb cDNA. Finally, removal of one copy of wingless, a gene required for normal trichome patterning, causes a similar loss of trichomes only in flies lacking the secondary enhancers. These results support the hypothesis that secondary enhancers contribute to phenotypic robustness in the face of environmental and genetic variability.

    View Publication Page
    07/22/10 | Segregation of yeast nuclear pores.
    Khmelinskii A, Keller PJ, Lorenz H, Schiebel E, Knop M
    Nature. 2010 Jul 22;466:E1. doi: 10.1038/nature09255

    During mitosis in Saccharomyces cerevisiae, senescence factors such as extrachromosomal ribosomal DNA circles (ERCs) are retained in the mother cell and excluded from the bud/daughter cell. Shcheprova et al. proposed a model suggesting segregation of ERCs through their association with nuclear pore complexes (NPCs) and retention of preexisting NPCs in the mother cell during mitosis. However, this model is inconsistent with previous data and we demonstrate here that NPCs do efficiently migrate from the mother into the bud. Therefore, binding to NPCs does not seem to explain the retention of ERCs in the mother cell.

    View Publication Page
    07/15/10 | Single-molecule discrimination of discrete perisynaptic and distributed sites of actin filament assembly within dendritic spines. (With commentary)
    Frost NA, Shroff H, Kong H, Betzig E, Blanpied TA
    Neuron. 2010 Jul 15;67(1):86-99. doi: 10.1016/j.neuron.2010.05.026

    Within dendritic spines, actin is presumed to anchor receptors in the postsynaptic density and play numerous roles regulating synaptic transmission. However, the submicron dimensions of spines have hindered examination of actin dynamics within them and prevented live-cell discrimination of perisynaptic actin filaments. Using photoactivated localization microscopy, we measured movement of individual actin molecules within living spines. Velocity of single actin molecules along filaments, an index of filament polymerization rate, was highly heterogeneous within individual spines. Most strikingly, molecular velocity was elevated in discrete, well-separated foci occurring not principally at the spine tip, but in subdomains throughout the spine, including the neck. Whereas actin velocity on filaments at the synapse was substantially elevated, at the endocytic zone there was no enhanced polymerization activity. We conclude that actin subserves spatially diverse, independently regulated processes throughout spines. Perisynaptic actin forms a uniquely dynamic structure well suited for direct, active regulation of the synapse.

    Commentary: A nice application of single particle tracking PALM (sptPALM), showing the flow of actin in the spines of live cultured neurons. Since 2008, the PALM in our lab has largely become a user facility, available to outside users as well as Janelians. Grad student Nick Frost in Tom Blanpied’s group at the U. of Maryland Med School visited on a number of occasions to use the PALM, with training and assistance from Hari.

    View Publication Page
    07/05/10 | Snapshot Image Mapping Spectrometer (IMS) with high sampling density for hyperspectral microscopy.
    Gao L, Kester RT, Hagen N, Tkaczyk TS
    Optics Express. 2010 Jul 5;18(14):14330-44. doi: 10.1364/AO.50.001792

    A snapshot Image Mapping Spectrometer (IMS) with high sampling density is developed for hyperspectral microscopy, measuring a datacube of dimensions 285 x 285 x 60 (x, y, lambda). The spatial resolution is approximately 0.45 microm with a FOV of 100 x 100 microm(2). The measured spectrum is from 450 nm to 650 nm and is sampled by 60 spectral channels with average sampling interval approximately 3.3 nm. The channel’s spectral resolution is approximately 8nm. The spectral imaging results demonstrate the potential of the IMS for real-time cellular fluorescence imaging.

    View Publication Page
    07/01/10 | Addiction-like behavior in Drosophila.
    Devineni AV, Heberlein U
    Communicative & Integrative Biology. 2010 Jul;3(4):357-9

    Alcohol abuse is a pervasive problem known to be influenced by genetic factors, yet our understanding of the mechanisms underlying alcohol addiction is far from complete. Drosophila melanogaster has been established as a model for studying the molecular mechanisms that mediate the acute and chronic effects of alcohol. However, the Drosophila model has not yet been extended to include more complex alcohol-related behaviors such as self-administration. We recently established a paradigm to characterize ethanol consumption and preference in flies. We demonstrated that flies prefer to consume ethanol-containing food over regular food, and this preference exhibits several features of alcohol addiction: flies increase ethanol consumption over time, they consume ethanol to pharmacologically relevant concentrations, they will overcome an aversive stimulus in order to consume ethanol, and they exhibit relapse after a period of ethanol deprivation. Thus, ethanol preference in flies provides a new model for studying important aspects of addiction and their underlying mechanisms. One mutant that displayed decreased ethanol preference, krasavietz, may represent a first step toward uncovering those mechanisms.

    View Publication Page
    07/01/10 | Proneural gene-linked neurogenesis in zebrafish cerebellum
    Shuichi Kani , Young-Ki Bae , Takashi Shimizu , Koji Tanabe , Chie Satou , Michael J. Parsons , Ethan Scott , Shin-ichi Higashijima , Masahiko Hibi
    Developmental Biology. 07/2010;343:1-17. doi: https://doi.org/10.1016/j.ydbio.2010.03.024

    In mammals, cerebellar neurons are categorized as glutamatergic or GABAergic, and are derived from progenitors that express the proneural genes atoh1 or ptf1a, respectively. In zebrafish, three atoh1 genes, atoh1a, atoh1b, and atoh1c, are expressed in overlapping but distinct expression domains in the upper rhombic lip (URL): ptf1a is expressed exclusively in the ventricular zone (VZ). Using transgenic lines expressing fluorescent proteins under the control of the regulatory elements of atoh1a and ptf1a, we traced the lineages of the cerebellar neurons. The atoh1+ progenitors gave rise not only to granule cells but also to neurons of the anteroventral rhombencephalon. The ptf1a+ progenitors generated Purkinje cells. The olig2+ eurydendroid cells, which are glutamatergic, were derived mostly from ptf1a+ progenitors in the VZ but some originated from the atoh1+ progenitors in the URL. In the adult cerebellum, atoh1a, atoh1b, and atoh1c are expressed in the molecular layer of the valvula cerebelli and of the medial corpus cerebelli, and ptf1a was detected in the VZ. The proneural gene expression patterns coincided with the sites of proliferating neuronal progenitors in the adult cerebellum. Our data indicate that proneural gene-linked neurogenesis is evolutionarily conserved in the cerebellum among vertebrates, and that the continuously generated neurons help remodel neural circuits in the adult zebrafish cerebellum.

    View Publication Page
    07/01/10 | The heparin-binding domain of HB-EGF mediates localization to sites of cell-cell contact and prevents HB-EGF proteolytic release.
    Prince RN, Schreiter ER, Zou P, Wiley HS, Ting AY, Lee RT, Lauffenburger DA
    Journal of Cell Science. 2010 Jul 1;123(Pt 13):2308-18. doi: 10.1242/jcs.058321

    Heparin-binding EGF-like growth factor (HB-EGF) is a ligand for EGF receptor (EGFR) and possesses the ability to signal in juxtacrine, autocrine and/or paracrine mode, with these alternatives being governed by the degree of proteolytic release of the ligand. Although the spatial range of diffusion of released HB-EGF is restricted by binding heparan-sulfate proteoglycans (HSPGs) in the extracellular matrix and/or cellular glycocalyx, ascertaining mechanisms governing non-released HB-EGF localization is also important for understanding its effects. We have employed a new method for independently tracking the localization of the extracellular EGF-like domain of HB-EGF and the cytoplasmic C-terminus. A striking observation was the absence of the HB-EGF transmembrane pro-form from the leading edge of COS-7 cells in a wound-closure assay; instead, this protein localized in regions of cell-cell contact. A battery of detailed experiments found that this localization derives from a trans interaction between extracellular HSPGs and the HB-EGF heparin-binding domain, and that disruption of this interaction leads to increased release of soluble ligand and a switch in cell phenotype from juxtacrine-induced growth inhibition to autocrine-induced proliferation. Our results indicate that extracellular HSPGs serve to sequester the transmembrane pro-form of HB-EGF at the point of cell-cell contact, and that this plays a role in governing the balance between juxtacrine versus autocrine and paracrine signaling.

    View Publication Page
    07/01/10 | Two-photon calcium imaging from head-fixed Drosophila during optomotor walking behavior.
    Seelig JD, Chiappe ME, Lott GK, Dutta A, Osborne JE, Reiser MB, Jayaraman V
    Nature Methods. 2010 Jul;7:535-40. doi: 10.1038/nmeth.1468

    Drosophila melanogaster is a model organism rich in genetic tools to manipulate and identify neural circuits involved in specific behaviors. Here we present a technique for two-photon calcium imaging in the central brain of head-fixed Drosophila walking on an air-supported ball. The ball’s motion is tracked at high resolution and can be treated as a proxy for the fly’s own movements. We used the genetically encoded calcium sensor, GCaMP3.0, to record from important elements of the motion-processing pathway, the horizontal-system lobula plate tangential cells (LPTCs) in the fly optic lobe. We presented motion stimuli to the tethered fly and found that calcium transients in horizontal-system neurons correlated with robust optomotor behavior during walking. Our technique allows both behavior and physiology in identified neurons to be monitored in a genetic model organism with an extensive repertoire of walking behaviors.

    View Publication Page