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Journal of Cell Science

Jamal Wakim, David Goudenege, Rodolphe Perrot, Naig Gueguen, Valerie Desquiret-Dumas, Juan Manuel Chao de la Barca, Ilaria Dalla Rosa, Florence Manero, Morgane Le Mao, Stephanie Chupin, Arnaud Chevrollier, Vincent Procaccio, Dominique Bonneau, David C Logan, Pascal Reynier, Guy Lenaers, Salim Khiati
Mitochondrial dynamics and distribution are critical in supplying ATP in response to energy demand. CLUH is a protein involved in mitochondrial distribution, whose dysfunction leads to mitochondrial clustering, the metabolic consequences of which remain unknown. To gain insight into the role of CLUH on mitochondrial energy production and cellular metabolism, we have generated CLUH knockout cells using CRISPR/Cas9. Mitochondrial clustering was associated with a smaller cell size, and with decreased abundance of respiratory complexes, resulting in OXPHOS defects...
April 19, 2017: Journal of Cell Science
Ji-Hyun Lee, Chan-Wool Lee, Si-Hyoung Park, Kwang-Min Choe
Cell-cell fusion is widely observed during development and disease and imposes a dramatic change on participating cells. Cell fusion should be tightly controlled, but the underlying mechanism is poorly understood. Here, we found that the JAK/STAT pathway suppressed cell fusion during wound healing and delimited the event to the vicinity of the wound in the Drosophila larval epidermis. In the absence of JAK/STAT signaling, a large syncytium containing 3-fold the number of nuclei observed in wild-type tissue formed in wounded epidermis...
April 19, 2017: Journal of Cell Science
Peter A Thomason, Jason S King, Robert H Insall
The steps leading to constitutive exocytosis are poorly understood. In Dictyostelium WASH complex mutants, exocytosis is blocked, so cells that take up fluorescent dextran from the medium retain it and remain fluorescent. Here we establish a FACS-based method to select cells that retain fluorescent dextran, allowing identification of mutants with disrupted exocytosis. Screening a pool of random mutants identified the WASH complex, as expected, and multiple mutants in the conserved HEAT-repeat containing protein Mroh1...
April 19, 2017: Journal of Cell Science
Ione Verdeny-Vilanova, Fabian Wehnekamp, Nitin Mohan, Ángel Sandoval Álvarez, Joseph Steven Borbely, Jason John Otterstrom, Don C Lamb, Melike Lakadamyali
Vesicle transport is regulated at multiple levels including regulation by scaffolding proteins and the cytoskeleton. This tight regulation is essential since slowing or stoppage of transport can cause accumulation of obstacles and has been linked to diseases. Understanding the mechanisms by which transport is regulated as well as how motor proteins overcome obstacles can give important clues as to how these mechanisms break down in disease states. Here, we describe that the cytoskeleton architecture impacts transport in a vesicle-size dependent manner, leading to pausing of vesicles larger than the separation of the microtubules...
April 18, 2017: Journal of Cell Science
Hanna Berger, Marlen Breuer, Hanna Peradziryi, Martina Podleschny, Ralf Jacob, Annette Borchers
PTK7 (protein tyrosine kinase 7) is an evolutionarily conserved transmembrane receptor with important roles in embryonic development and disease. Originally identified as a gene upregulated in colon cancer it was later shown to regulate planar cell polarity (PCP) and directional cell movement. PTK7 is a Wnt co-receptor, however its role in Wnt signaling remains controversial. Here, we find evidence that place PTK7 at the intersection of canonical and non-canonical Wnt signaling pathways. In presence of canonical Wnt ligands PTK7 is subject to caveolin-mediated endocytosis, while it is unaffected by non-canonical Wnt ligands...
April 18, 2017: Journal of Cell Science
Sun Joo Lee, Veronica Rodriguez-Bravo, Hyunjung Kim, Sutirtha Datta, Emily A Foley
PP2A(B56) is a serine/threonine phosphatase essential for mitosis. At the kinetochore, PP2A(B56) both stabilizes microtubule binding and promotes silencing of the spindle assembly checkpoint (SAC) through its association with the SAC protein BubR1. Cells depleted of the B56 regulatory subunits of PP2A are delayed in APC/C(Cdc20) activation, an essential step for mitotic exit. It has been hypothesized that this delay arises from increased production of the mitotic checkpoint complex (MCC), an APC/C(Cdc20) inhibitor formed at unattached kinetochores through SAC signaling...
April 12, 2017: Journal of Cell Science
Swati Arora, Ingrid Saarloos, Robbelien Kooistra, Rhea van de Bospoort, Matthijs Verhage, Ruud F Toonen
Neuronal dense-core vesicles (DCVs) transport and secrete neuropeptides necessary for development, plasticity and survival, but little is known about their fusion mechanism. We show that Snap-25 null mutant (SNAP-25 KO) neurons, previously shown to degenerate after 4 days in vitro (DIV), contain fewer DCVs and have reduced DCV fusion probability in surviving neurons at DIV14. At DIV3, before degeneration, SNAP-25 KO neurons show normal DCV fusion, but one day later fusion is significantly reduced. To test if other SNAP homologs support DCV fusion, we expressed SNAP-23, -29 or -47 in SNAP-25 KO neurons...
April 12, 2017: Journal of Cell Science
Umberto De Marchi, Aurelie Hermant, Jonathan Thevenet, Yann Ratinaud, Jaime Santo-Domingo, Denis Barron, Andreas Wiederkehr
Pancreatic beta-cells sense glucose promoting insulin secretion. Glucose sensing requires the sequential stimulation of glycolysis, mitochondrial metabolism and Ca(2+) entry. To elucidate how mitochondrial activation in beta-cells contributes to insulin secretion, we have compared the effects of glucose and the mitochondrial substrate methylsuccinate in INS-1E insulin secreting cells, at the respective concentrations they maximally activate mitochondrial respiration. Both substrates induced insulin secretion with distinct respiratory profiles, mitochondrial hyperpolarization, NADH production and ATP/ADP ratios...
April 12, 2017: Journal of Cell Science
Sigal Shachar, Tom Misteli
The eukaryotic genome is organized in a manner that allows folding of the genetic material in the confined space of the cell nucleus, while at the same time enabling its physiological function. A major principle of spatial genome organization is the non-random position of genomic loci relative to other loci and to nuclear bodies. The mechanisms that determine the spatial position of a locus, and how position affects function, are just beginning to be characterized. Initial results suggest that there are multiple, gene-specific mechanisms and the involvement of a wide range of cellular machineries...
April 12, 2017: Journal of Cell Science
Kula N Jha, Swamy K Tripurani, Gibbes R Johnson
Spermiogenesis includes transcriptional silencing, chromatin condensation and extensive morphological changes as spermatids transform into sperm. Chromatin condensation involves histone hyperacetylation, transitory DNA breaks, histone H2AX Ser139 phosphorylation (γH2AX), and replacement of histones by protamines. Previously, we reported that the spermatid protein kinase TSSK6 is essential for fertility in mice, but its specific role in spermiogenesis is unknown. Here, we show that TSSK6 expression is spatiotemporally coincident with γH2AX formation in nuclei of developing mouse spermatids...
April 7, 2017: Journal of Cell Science
Elaina B Breznau, Megan Murt, T Lynne Blasius, Kristen J Verhey, Ann L Miller
Centralspindlin, a complex of the kinesin-6 MKLP1 and MgcRacGAP, is required for cytokinesis and cell-cell junctions. During anaphase, Centralspindlin accumulates at overlapping central spindle microtubules and directs contractile ring formation by recruiting the GEF Ect2 to the cell equator to activate RhoA. We found that MgcRacGAP localized to plus ends of equatorial astral microtubules during cytokinesis in Xenopus laevis embryos. How MgcRacGAP is stabilized at microtubule plus ends is unknown. We identified an SxIP motif in X...
April 7, 2017: Journal of Cell Science
Faye M Nixon, Thomas R Honnor, Nicholas I Clarke, Georgina P Starling, Alison J Beckett, Adam M Johansen, Julia A Brettschneider, Ian A Prior, Stephen J Royle
Serial block face scanning electron microscopy (SBF-SEM) is a powerful method to analyze cells in 3D. Here, working at the resolution limit of the method, we describe a correlative light-SBF-SEM workflow to resolve microtubules of the mitotic spindle in human cells. We present four examples of uses for this workflow which are not practical by light microscopy and/or transmission electron microscopy. First, distinguishing closely associated microtubules within K-fibers; second, resolving bridging fibers in the mitotic spindle; third, visualizing membranes in mitotic cells, relative to the spindle apparatus; fourth, volumetric analysis of kinetochores...
April 7, 2017: Journal of Cell Science
Frédéric Saltel, Alban Giese, Lamia Azzi, Habiba Elatmani, Pierre Costet, Zakaria Ezzoukhry, Nathalie Dugot-Senant, Lucile Miquerol, Oréda Boussadia, Harald Wodrich, Pierre Dubus, Hélène Jacquemin-Sablon
Unr is a cytoplasmic RNA-binding protein with roles in the regulation of mRNA stability and translation. In this study, we have identified a novel function for Unr, which acts as a positive regulator of placental development. Unr expression studies in the developing placenta revealed the presence of Unr-rich foci apparently localized in the nuclei of trophoblast giant cells (TGCs). We determined that these foci are actually cross sections of a network of double-wall nuclear membranes invaginations containing a cytoplasmic core, related to the nucleoplasmic reticulum (NR), and accordingly named Unr-NRs...
April 6, 2017: Journal of Cell Science
Jacob A Ross, Richard G Webster, Tanguy Lechertier, Louise E Reynolds, Mark Turmaine, Maximilien Bencze, Yalda Jamshidi, Hakan Cetin, Francesco Muntoni, David Beeson, Kairbaan Hodilvala-Dilke, Francesco J Conti
The neuromuscular junction (NMJ) is the synapse between motoneuron and skeletal muscle, and is responsible for eliciting muscle contraction. Neurotransmission at synapses depends on the release of synaptic vesicles at sites called active zones (AZs). Various proteins of the extracellular matrix are crucial for NMJ development; however little is known about the identity and functions of the receptors that mediate their effects. Using genetically modified mice, we find that integrin-α3, an adhesion receptor at the presynaptic membrane, is involved in the localisation of AZ components and efficient synaptic vesicle release...
April 6, 2017: Journal of Cell Science
Congcong Dong, Honglin Xu, Rui Zhang, Nobutoshi Tanaka, Masatoshi Takeichi, Wenxiang Meng
The epithelium has apico-basal axis polarity that plays an important role in absorption, excretion and other physiological functions. In epithelial cells, a substantial number of noncentrosomal microtubules (MTs) are scattered in the cytoplasm with an apico-basal polarity to adapt to these complex functions. Several previous studies have found that noncentrosomal MTs are nucleated at the centrosome, and then released and translocated elsewhere. However, the detailed process and molecular mechanism remains largely unknown...
April 6, 2017: Journal of Cell Science
Masaaki Iwamoto, Hiroko Osakada, Chie Mori, Yasuhiro Fukuda, Koji Nagao, Chikashi Obuse, Yasushi Hiraoka, Tokuko Haraguchi
The nuclear pore complex (NPC), a gateway for nucleocytoplasmic trafficking, is composed of about 30 different proteins called nucleoporins. It remains unknown whether the NPCs within a species are homogeneous or vary depending on the cell type, or physiological condition. Here, we present evidence for compositionally distinct NPCs that form within a single cell in a binucleated ciliate. In Tetrahymena thermophila, each cell contains both a transcriptionally-active macronucleus (MAC) and a germline micronucleus (MIC)...
April 6, 2017: Journal of Cell Science
Stéphane Frémont, Guillaume Romet-Lemonne, Anne Houdusse, Arnaud Echard
Cytokinetic abscission is the terminal step of cell division, leading to the physical separation of the two daughter cells. The exact mechanism mediating the final scission of the intercellular bridge connecting the dividing cells is not fully understood, but requires the local constriction of endosomal sorting complex required for transport (ESCRT)-III-dependent helices, as well as remodelling of lipids and the cytoskeleton at the site of abscission. In particular, microtubules and actin filaments must be locally disassembled for successful abscission...
April 3, 2017: Journal of Cell Science
Mohamed Aittaleb, Isabel Martinez-Pena Y Valenzuela, Mohammed Akaaboune
Bimolecular fluorescence complementation (BiFC) approach was used to study the molecular interactions between different components of the postsynaptic protein complex at the neuromuscular junction of living mice. Here, we showed that rapsyn forms complex with both α-dystrobrevin and α-syntrophin at the crests of junctional folds. The linkage of rapsyn to α-syntrophin and/or α-dystrobrevin is mediated by utrophin, a protein localized at AChR-rich domain. In mice deficient in α-syntrophin, in which utrophin is no longer present at the synapse, rapsyn interaction with α- dystrobrevin was completely abolished...
March 31, 2017: Journal of Cell Science
Gulsan Ara Sathi, Mahmoud Farahat, Emilio Satoshi Hara, Hiroaki Taketa, Hitoshi Nagatsuka, Takuo Kuboki, Takuya Matsumoto
The importance of macrophages in tissue development and regeneration have been strongly emphasized. However, the specific roles of macrophage colony-stimulating factor (MCSF), the key regulator of macrophage differentiation, in glandular tissue development have been unexplored. Here, we disclose new macrophage-independent roles of MCSF in tissue development. We initially found that MCSF is markedly upregulated at embryonic day E13.5, at a stage preceding the colonization of macrophages (at E15.5) in mouse submandibular gland (SMG) tissue...
March 27, 2017: Journal of Cell Science
Kezhen Yao, Qi Chen, Yongyan Wu, Fayang Liu, Xin Chen, Yong Zhang
In murine macrophages infected with Mycobacterium tuberculosis (Mtb), the level of phosphorylated STAT1 (PSTAT1) driving the expression of many pro-apoptosis genes, increases quickly but then declines over a period of hours. On the contrary, there is a continued increase of unphosphorylated STAT1 (USTAT1) that persists for several days. Similar trend is discovered between USTAT1 level and the intracellular bacterial burden during late infection. To investigate the significance of high level of USTAT1, we increased its concentration exogenously, and the apoptosis rate induced by Mtb is sufficiently decreased...
March 27, 2017: Journal of Cell Science
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