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Volume 14 Issue 10, October 2012

Auxin modulates aquaporin for lateral root emergence.p991

Editorial

  • As children return to school at the end of the summer in the UK, planned reforms aim to increase their science and maths literacy. A comprehensive foundation in these essential subjects is necessary to ensure that the UK remains at the forefront of science and technology for decades to come.

    Editorial

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Turning Points

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News & Views

  • After food consumption, insulin-secreting pancreatic β-cells detect increased glucose and incretin hormones, and respond by releasing insulin. Wolfram syndrome 1, a protein that mitigates endoplasmic reticulum (ER) stress, is now shown to regulate insulin synthesis and release — revealing a molecular point of convergence between the ER stress and insulin release pathways.

    • Katleen Lemaire
    • Frans Schuit
    News & Views
  • Focal adhesions are large structures through which integrins and scaffold proteins link the actin cytoskeleton to the extracellular matrix. A detailed analysis of integrin dynamics now indicates that focal-adhesion-associated integrins constantly switch between active and immobilized, and unbound and free-diffusing states, with different fibronectin-binding integrin heterodimers showing distinct focal-adhesion dynamics.

    • Johanna Ivaska
    News & Views
  • The ESCRT (endosomal sorting complex required for transport) machinery is responsible for scission of the cytokinetic bridge that connects daughter cells at the end of mitosis. Specific endosomes are now found to mediate local bridge constriction and actin clearance in human cells, which contribute to the recruitment of ESCRT components at the abscission site.

    • Arnaud Echard
    News & Views
  • Vascular endothelial growth factor (VEGF) signalling induces embryonic vascular development and angiogenesis in adult tissues. Direct phosphorylation of the actin-binding protein profilin by VEGF receptors is now shown to increase its affinity for actin, and to be essential for adult but not embryonic arteriogenesis.

    • Michael Simons
    • Martin A. Schwartz
    News & Views
  • Given the important role of the hypothalamus in regulating feeding and metabolism, there has been considerable interest in a possible function for hypothalamic stem cells in modulating body weight in health and disease. Mice given a high-fat diet develop inflammation in the hypothalamus and lose key types of neurons. It now appears that another effect of a high-fat diet is to reduce neural stem cell numbers, as well as their ability to make new neurons — effects that are associated with activation of the IKKβ/NF-κB pathway — thereby exacerbating the primary loss of neurons and resulting in altered feeding behaviour and obesity.

    • Frederick J. Livesey
    News & Views
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Research Highlights

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Article

  • Bennett and colleagues find that auxin modulates water uptake in Arabidopsis roots by negatively regulating the expression of water channel aquaporins to allow lateral root emergence. The functional importance of aquaporins is supported by a mathematical model that shows delayed lateral root emergence when aquaporin levels are perturbed, as well as by the effects observed after aquaporin overexpression or mutation.

    • Benjamin Péret
    • Guowei Li
    • Malcolm J. Bennett
    Article
  • Cai and colleagues show that the function of adult hypothalamic neural stem cells in mice is impaired following NF-κB activation associated with a chronic high-fat diet, resulting in development of obesity and neurodegenerative features. Mechanistically, NF-κB affects both Notch signalling and apoptosis in these cells.

    • Juxue Li
    • Yizhe Tang
    • Dongsheng Cai
    Article
  • Goldman and colleagues report that the transcriptional repressor Insm1a is essential for retinal regeneration following injury in fish. Insm1a suppresses the expression of Ascl1a to promote Müller glial cells’ dedifferentiation at early stages of regeneration, and defines the regeneration zone by negatively regulating the expression of the heparin-binding EGF. It also halts the proliferation of retinal progenitors in the late stages of the process.

    • Rajesh Ramachandran
    • Xiao-Feng Zhao
    • Daniel Goldman
    Article
  • Tumbarello, Buss and colleagues report that the motor protein myosin VI has an important role in autophagosome maturation. They show that myosin VI binds to autophagy adaptors to mediate delivery of endocytic cargo and endosomal membrane to autophagosomes, and promote autophagosome–lysosome fusion.

    • David A. Tumbarello
    • Bennett J. Waxse
    • Folma Buss
    Article
  • The mechanisms that control intracellular Wnt trafficking and secretion are beginning to be unravelled. However, little is known about how Wnt proteins are transported once they reach extracellular space. Boutros and colleagues show that active Wnt proteins are secreted on exosomes from Drosophila and human cells, and provide insight into the cellular machinery that regulates their transport and release.

    • Julia Christina Gross
    • Varun Chaudhary
    • Michael Boutros
    Article
  • Fox and colleagues report that VEGF-A stimulation of endothelial cells induces the phosphorylation of profilin by VEGFR2 and Src. This regulation promotes endothelial cell migration and angiogenesis in mice facing pathological conditions such as tissue wounding and ischaemic injury.

    • Yi Fan
    • Abul Arif
    • Paul L. Fox
    Article
  • During cytokinesis, the intercellular bridge connecting the mother and daughter cell is thinned by a process called secondary ingression before it is eventually severed in an ESCRT-III-dependent manner. Prekeris and colleagues report that FIP3-positive endosomes deliver p50RhoGAP and SCAMP2/3 proteins to the intercellular bridge, which promote actin depolymerization to decrease the bridge diameter and allow ESCRT-III binding.

    • John A. Schiel
    • Glenn C. Simon
    • Rytis Prekeris
    Article
  • In plants, the heterotrimeric G-protein α subunit is kept inactive by binding to the regulator of G protein signalling 1 (RGS1) protein. Jones and colleagues show that G-protein β and γ subunits recruit the WNK8 kinase to the plasma membrane, where WNK8 phosphorylates RGS1 and facilitates its internalization. This effect de-represses Gα signalling and is required for sugar signalling and cell proliferation.

    • Daisuke Urano
    • Nguyen Phan
    • Alan M. Jones
    Article
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Letter

  • Notch signalling in the intestinal crypt is modulated to drive commitment to the secretory fate. Clevers and colleagues find that cells expressing the Notch ligand DLL1 are intermediate secretory cells that can revert to Lgr5+ stem cells upon damage.

    • Johan H. van Es
    • Toshiro Sato
    • Hans Clevers
    Letter
  • Persistent ER stress in pancreatic β-cells contributes to the pathogenesis of type 2 diabetes. Fonseca and colleagues show that the ER membrane glycoprotein WFS1, which is mutated in people with Wolfram syndrome, has a known role in the ER stress response. It regulates insulin production and secretion in β-cells by associating with adenylyl cyclase 8 at the plasma membrane and generating cAMP. ER stress prevents WFS1 plasma membrane localization, attenuating cAMP production and insulin secretion.

    • Sonya G. Fonseca
    • Fumihiko Urano
    • Mark Burcin
    Letter
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