DB Letters - Dynamin-mediated endocytosis is required for tube closure, cell intercalation, and biased apical expansion during epithelial tubulogenesis in the Drosophila ovary
Contributors: Nathaniel C. Peters, Celeste A. Berg
... Most metazoans are able to grow beyond a few hundred cells and to support differentiated tissues because they elaborate multicellular, epithelial tubes that are indispensable for nutrient and gas exchange. To identify and characterize the cellular behaviors and molecular mechanisms required for the morphogenesis of epithelial tubes (i.e., tubulogenesis), we have turned to the D. melanogaster ovary. Here, epithelia surrounding the developing egg chambers first pattern, then form and extend a set of simple, paired, epithelial tubes, the dorsal appendage (DA) tubes, and they create these structures in the absence of cell division or cell death. This genetically tractable system lets us assess the relative contributions that coordinated changes in cell shape, adhesion, orientation, and migration make to basic epithelial tubulogenesis. We find that Dynamin, a conserved regulator of endocytosis and the cytoskeleton, serves a key role in DA tubulogenesis. We demonstrate that Dynamin is required for distinct aspects of DA tubulogenesis: DA-tube closure, DA-tube-cell intercalation, and biased apical-luminal cell expansion. We provide evidence that Dynamin promotes these processes by facilitating endocytosis of cell–cell and cell–matrix adhesion complexes, and we find that precise levels and sub-cellular distribution of E-Cadherin and specific Integrin subunits impact DA tubulogenesis. Thus, our studies identify novel morphogenetic roles (i.e., tube closure and biased apical expansion), and expand upon established roles (i.e., cell intercalation and adhesion remodeling), for Dynamin in tubulogenesis.
Contributors: Kelsey Branchfield, Rongbo Li, Vlasta Lungova, Jamie M. Verheyden, David McCulley, Xin Sun
... Alveologenesis is the final step of lung maturation, which subdivides the alveolar region of the lung into smaller units called alveoli. Each of the nascent dividers serves as a new gas-exchange surface, and collectively they drastically increase the surface area for breathing. Disruption of alveologenesis results in simplification of alveoli, as is seen in premature infants diagnosed with bronchopulmonary dysplasia (BPD), a prevalent lung disease that is often associated with lifelong breathing deficiencies. To date, a majority of studies of alveologenesis rely on two-dimensional (2D) analysis of tissue sections. Given that an overarching theme of alveologenesis is thinning and extension of the epithelium and mesenchyme to facilitate gas exchange, often only a small portion of a cell or a cellular structure is represented in a single 2D plane. Here, we use a three-dimensional (3D) approach to examine the structural architecture and cellular composition of myofibroblasts, alveolar type 2 cells, elastin and lipid droplets in normal as well as BPD-like mouse lung. We found that 2D finger-like septal crests, commonly used to depict growing alveolar septae, are often artifacts of sectioning through fully established alveolar walls. Instead, a more accurate representation of growing septae are 3D ridges that are lined by platelet-derived growth factor receptor alpha (PDGFRA) and alpha smooth muscle actin (α-SMA)-expressing myofibroblasts, as well as the elastin fibers that they produce. Accordingly in 3D, both α-SMA and elastin were each found in connected networks underlying the 3D septal ridges rather than as isolated dots at the tip of 2D septal crests. Analysis through representative stages of alveologenesis revealed unappreciated dynamic changes in these patterns. PDGFRA-expressing cells are only α-SMA-positive during the first phase of alveologenesis, but not in the second phase, suggesting that the two phases of septae formation may be driven by distinct mechanisms. Thin elastin fibers are already present in the alveolar region prior to alveologenesis, suggesting that during alveologenesis, there is not only new elastin deposition, but also extensive remodeling to transform thin and uniformly distributed fibers into thick cables that rim the nascent septae. Analysis of several genetic as well as hyperoxia-induced models of BPD revealed that the myofibroblast organization is perturbed in all, regardless of whether the origin of defect is epithelial, mesenchymal, endothelial or environmental. Finally, analysis of relative position of PDGFRA-positive cells and alveolar type 2 cells reveal that during alveologenesis, these two cell types are not always adjacent to one another. This result suggests that the niche and progenitor relationship afforded by their close juxtaposition in the adult lung may be a later acquired property. These insights revealed by 3D reconstruction of the septae set the foundation for future investigations of the mechanisms driving normal alveologenesis, as well as causes of alveolar simplification in BPD.
Contributors: Zhilin Xie, Richard G. Blair, Nina Orlovskaya, David A. Cullen, Saul H. Lapidus, Dariusz Kata, Paweł Rutkowski, Jerzy Lis
... The previously unknown hexagonal ReB2-type IrB2 diboride and orthorhombic IrB monoboride phases were produced by mechanochemical syntheses. High energy ball milling of elemental Ir and B powder for 30h, followed by annealing of the powder at 1050°C for 48h, resulted in the formation of the desired phases. Both traditional laboratory and high resolution synchrotron X-ray diffraction (XRD) analyses were used for phase identification of the synthesized powder. In addition to XRD, scanning electron microscopy and transmission electron microscopy were employed to further characterize the microstructure of the phases produced.
Contributors: Erick I. Pérez-García, Karla F. Meza-Sosa, Yaxem López-Sevilla, Nohemi Camacho-Concha, Nilda C. Sánchez, Leonor Pérez-Martínez, Gustavo Pedraza-Alva
... Inactivation of the tumor suppressor Merlin, by deleterious mutations or by protein degradation via sustained growth factor receptor signaling-mediated mechanisms, results in cell transformation and tumor development. In addition to these mechanisms, here we show that, miRNA-dependent negative regulation of Merlin protein levels also promotes cell transformation. We provide experimental evidences showing that miR-146a negatively regulates Merlin protein levels through its interaction with an evolutionary conserved sequence in the 3´ untranslated region of the NF2 mRNA. Merlin downregulation by miR-146a in A549 lung epithelial cells resulted in enhanced cell proliferation, migration and tissue invasion. Accordingly, stable miR-146a-transfectant cells formed tumors with metastatic capacity in vivo. Together our results uncover miRNAs as yet another negative mechanism controlling Merlin tumor suppressor functions.
ATP4a is required for development and function of the Xenopus mucociliary epidermis – a potential model to study proton pump inhibitor-associated pneumonia
Contributors: Peter Walentek, Tina Beyer, Cathrin Hagenlocher, Christina Müller, Kerstin Feistel, Axel Schweickert, Richard M. Harland, Martin Blum
... Proton pump inhibitors (PPIs), which target gastric H+/K+ATPase (ATP4), are among the most commonly prescribed drugs. PPIs are used to treat ulcers and as a preventative measure against gastroesophageal reflux disease in hospitalized patients. PPI treatment correlates with an increased risk for airway infections, i.e. community- and hospital-acquired pneumonia. The cause for this correlation, however, remains elusive. The Xenopus embryonic epidermis is increasingly being used as a model to study airway-like mucociliary epithelia. Here we use this model to address how ATP4 inhibition may affect epithelial function in human airways. We demonstrate that atp4a knockdown interfered with the generation of cilia-driven extracellular fluid flow. ATP4a and canonical Wnt signaling were required in the epidermis for expression of foxj1, a transcriptional regulator of motile ciliogenesis. The ATP4/Wnt module activated foxj1 downstream of ciliated cell fate specification. In multiciliated cells (MCCs) of the epidermis, ATP4a was also necessary for normal myb expression, apical actin formation, basal body docking and alignment of basal bodies. Furthermore, ATP4-dependent Wnt/β-catenin signaling in the epidermis was a prerequisite for foxa1-mediated specification of small secretory cells (SSCs). SSCs release serotonin and other substances into the medium, and thereby regulate ciliary beating in MCCs and protect the epithelium against infection. Pharmacological inhibition of ATP4 in the mature mucociliary epithelium also caused a loss of MCCs and led to impaired mucociliary clearance. These data strongly suggest that PPI-associated pneumonia in human patients might, at least in part, be linked to dysfunction of mucociliary epithelia of the airways.
Contributors: P. Felfer, T. Li, K. Eder, H. Galinski, A.P. Magyar, D.C. Bell, G.D.W. Smith, N. Kruse, S.P. Ringer, J.M. Cairney
... Due to their unique properties, nano-sized materials such as nanoparticles and nanowires are receiving considerable attention. However, little data is available about their chemical makeup at the atomic scale, especially in three dimensions (3D). Atom probe tomography is able to answer many important questions about these materials if the challenge of producing a suitable sample can be overcome.
Data Article - Living cell imaging and Rac1-GTP levels of CXCL12-treated migrating neural progenitor cells in stripe assay
Contributors: Min Zhang, Aihong Song, Siqiang Lai, Lisha Qiu, Yunlong Huang, Qiang Chen, Bing Zhu, Dongsheng Xu, Jialin C. Zheng
... This data article contains three figures and three videos related to the research article entitled “Applications of Stripe Assay in the Study of CXCL12-mediated Neural Progenitor Cell Migration and Polarization” Zhang et al. (2015) , which uses stripe assay to study mouse neural progenitor cell (NPC) migration and polarization. The current article describes the neurosphere method used to culture NPCs. NPCs in neurospheres and monolayer were characterized using immunocytochemistry method with antibodies against two classic NPC markers: nestin and SOX2. The article also describes method to obtain sufficient protein lysates from NPCs in the stripe assay. When protein lysates were subjected to Rac1 affinity precipitation, Rac1-GTP was detected in the pull-down samples. In addition, the articles provides live cell imaging data to better understand CXCL12-mediated cellular migration and polarization.
Data Article - Data characterizing flexural properties of Al/Al2O3 syntactic foam core metal matrix sandwich
Contributors: Mohammed Yaseer Omar, Chongchen Xiang, Nikhil Gupta, Oliver M. Strbik III, Kyu Cho
... Microstructural observations and flexural property datasets are provided for aluminum alloy matrix syntactic foam core sandwich composites. The tests are conducted in three-point bending configuration. The data supplied includes methods used for conducting microscopy and mechanical testing. Raw load–displacement data, which is used to plot stress–strain graphs, obtained during the flexural test is also included. Images from a DSLR camera are stitched together to form a detailed failure sequencing video. Failure of specimens is captured in sequential images using a digital camera. These images are stitched together to develop a video for visualization of failure mechanisms. Calculations are also included for a theoretical model that is used to estimate the flexural properties of the syntactic foam core sandwich.
Report - Crystal Structures of SecYEG in Lipidic Cubic Phase Elucidate a Precise Resting and a Peptide-Bound State
Contributors: Yoshiki Tanaka, Yasunori Sugano, Mizuki Takemoto, Takaharu Mori, Arata Furukawa, Tsukasa Kusakizako, Kaoru Kumazaki, Ayako Kashima, Ryuichiro Ishitani, Yuji Sugita
... The bacterial SecYEG translocon functions as a conserved protein-conducting channel. Conformational transitions of SecYEG allow protein translocation across the membrane without perturbation of membrane permeability. Here, we report the crystal structures of intact SecYEG at 2.7-Å resolution and of peptide-bound SecYEG at 3.6-Å resolution. The higher-resolution structure revealed that the cytoplasmic loop of SecG covers the hourglass-shaped channel, which was confirmed to also occur in the membrane by disulfide bond formation analysis and molecular dynamics simulation. The cytoplasmic loop may be involved in protein translocation. In addition, the previously unknown peptide-bound crystal structure of SecYEG implies that interactions between the cytoplasmic side of SecY and signal peptides are related to lateral gate opening at the first step of protein translocation. These SecYEG structures therefore provide a number of structural insights into the Sec machinery for further study.
Sulphur-cycling bacteria and ciliated protozoans in a Beggiatoaceae mat covering organically enriched sediments beneath a salmon farm in a southern Chilean fjord
Contributors: Carlos P. Aranda, Cristian Valenzuela, Yessica Matamala, Félix A. Godoy, Nicol Aranda
... The colourless mat covering organically enriched sediments underlying an intensive salmon farm in Estero Pichicolo, southern Chile, was surveyed by combined 454 PyroTag and conventional Sanger sequencing of 16S/18S ribosomal RNA genes for Bacteria and Eukarya. The mat was dominated by the sulphide-oxidizing bacteria (SOB) Candidatus Isobeggiatoa, Candidatus Parabeggiatoa and Arcobacter. By order of their abundances, sulphate-reducing bacteria (SRB) were represented by diverse deltaproteobacterial Desulfobacteraceae, but also within Desulfobulbaceae, Desulfuromonadaceae and Desulfovibrionaceae. The eukaryotic PyroTags were dominated by polychaetes, copepods and nematodes, however, ciliated protozoans were highly abundant in microscopy observations, and were represented by the genera Condylostoma, Loxophyllum and Peritromus. Finally, the abundant Sulfurimonas/Sulfurovum also suggest the occurrence of zero-valence sulphur oxidation, probably derived from Beggiatoaceae as a result of bacteriovorus infaunal activity or generated as free S0 by the Arcobacter bacteria. The survey suggests an intense and complex sulphur cycle within the surface of salmon-farm impacted sediments.