DOCSLIB.ORG

Constricting Membranes at the Nano and Micro Scale

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Constricting Membranes at the Nano and Micro Scale COMMENTARY Constricting membranes at the nano and micro scale Olivia L. Moorena and Dorothy A. Schaferb,1 aDepartment of Cell Biology, Washington University School of Medicine, St. Louis, MO 63110; and bDepartments of Biology and Cell Biology, University of Virginia, Charlottesville, VA 22904 ynamin GTPases regulate membrane traffic, in part, by constricting nanometer-sized membrane tubes to form vesi- Dcles by fission. In this issue of PNAS, Chua et al. (1) report that dynamin2 remodels membranes on a much grander scale by influencing the con- tractile activity of actomyosin encircling epithelial cells at their apical cell–cell junctions. Using a simple epithelial cell system, Madin-Darby canine kidney (MDCK) epithelial cells, Chua et al. Fig. 1. Dynamin GTPase constricts membranes during endocytosis and at epithelial cell apical junctions. found that apical junctional complexes Dynamins promote fission of Ϸ50-nm-diameter membrane tubes to form clathrin-coated vesicles (on that contain the cytoskeletal linker pro- right). As described by Chua et al. (1), epithelial cells expressing the mutant dynamin2 protein, dynamin2- tein, ZO-1, and elements of the basolat- K44A (blue cell), become highly constricted, suggesting a new role for dynamin2 in regulating the eral F-actin cytoskeleton, were missing actomyosin cytoskeleton. or poorly organized in cells depleted of dynamin2. Notably, in MDCK cells ex- pressing the GTP-binding-defective mu- portantly, apical constrictions induced tions of cortactin with actin filaments tant protein, dynamin2-K44A, polarized by dynamin2-K44A required dynamic were required for robust constriction, membrane domains defined by ZO-1- actin filaments and active myosin II, be- but binding to Arp2/3 complex was not. containing apical junctions formed, but cause constriction was inhibited by Because dynamin2 is a tetramer and oli- the circumferential actomyosin network agents that perturb filament assembly gomerizes (10, 11), complexes of dy- associated with junctional complexes and turnover or block myosin II ATPase namin2-K44A and cortactin could form was constricted Ͼ2-fold over that in activity. a multivalent scaffold capable of inter- cells expressing wild-type dynamin2 Contractile actomyosin networks at acting with multiple actin filaments. (Fig. 1). Together, these finding sug- epithelial apical junctional boundaries Both dynamin2-K44A and cortactin are gested that dynamin2 provides cues that maintain a dynamic, yet invincible, epi- enriched at apical junctions (1) where establish and maintain the polarized epi- thelial sheet. These networks drive mor- cortactin could interact with the junc- thelial phenotype. Moreover, they sug- phogenesis of sheets, heal their wounds, tional proteins, ZO-1 or p120-catenin gested that dynamin2 influences the orchestrate cell divisions, and extrude (12, 13). Thus, cortactin could bridge contractile activity of apical junctional apoptotic cells, while at the same time, actin filaments of actomyosin and actomyosin networks. preserving a cellular barrier that is the membrane-associated proteins enriched Because dynamins are well-known hallmark of epithelial tissues (6). Con- at apical junctions. Cortactin’s capacity regulators of endocytosis and membrane traction by these networks depends on to respond to and integrate a variety of recycling pathways (2), and establishing myosin motors that slide actin filaments cellular signals might further enhance and maintaining polarized membrane and actin polymers organized into ap- the actions of such a dynamin2– domains and apical junctions requires an propriate networks by filament cross- cortactin–F-actin scaffold (14). intricate balance of endocytosis and in- linking proteins (7, 8). Connections of A growing body of evidence impli- tracellular membrane traffic (3–5), it is the actin network to the plasma mem- cates dynamins as actin filament regula- not surprising that dynamin2 would be brane are also required to effect changes tors. At the biochemical level, dynamin involved in orchestrating epithelial cell in cell shape. In many systems, Rho- family proteins share many binding part- polarity. However, Chua et al. (1) focus family GTPases and their effectors regu- ners that associate either directly, like on the unexpected participation of dy- late assembly and activity of actomyosin cortactin, or indirectly with actin fila- namin2 in regulating contractility of the networks. ments via their regulators (15). Many apical junctional actomyosin network. The intriguing findings by Chua et al. dynamin-associated proteins intersect Extreme apical constriction was only (1) prompt several questions about pathways that promote de novo filament induced in MDCK cells when mutant mechanisms by which the large GTPase assembly via the Arp2/3 complex. At the dynamin2 proteins having low GTP- dynamin2 influences actomyosin con- cellular level, the functions of a variety binding affinity were expressed. Treat- tractility. Some insight comes from the of cellular structures that depend on ment with the dynamin inhibitor dyna- finding that the F-actin binding protein dynamic actin filaments are perturbed in sore or expressing mutant proteins that cortactin is involved in promoting in- cells expressing mutant dynamin pro- stabilize the GTP-bound form of dy- tense apical constrictions in partnership teins, most often dynamin2-K44A (15). namin2 did not promote apical constric- with dynamin2-K44A. Cortactin associ- tions. Although these reagents inhibit ates with dynamin2 via interactions of endocytic pathways, Chua et al. showed the cortactin Src homology 3 domain Author contributions: O.L.M. and D.A.S. wrote the paper. that excessive apical constriction did not and dynamin2’s proline-rich domain (9). The authors declare no conflict of interest. result when either clathrin-mediated or Apical constriction did not occur in cells See companion article on page 20770. caveolae-dependent endocytosis was expressing a mutant form of cortactin 1To whom correspondence should be addressed. E-mail: blocked using different strategies. Im- that does not bind dynamin2. Interac- [email protected]. www.pnas.org͞cgi͞doi͞10.1073͞pnas.0911630106 PNAS ͉ December 8, 2009 ͉ vol. 106 ͉ no. 49 ͉ 20559–20560 Downloaded by guest on September 29, 2021 Interestingly, a role for dynamin2 in reg- sient needs to shape cellular structures modeling complexes and activities. ulating microtubule dynamics was re- or pull them together. Tension gener- Alternatively, or in addition, local re- cently reported (16), suggesting that ated by actomyosin networks may be modeling of membranes in response to dynamin’s influence on cytoskeletal pro- transient or temporally regulated to ef- dynamin2 GTPase-dependent lipid in- cesses may be more wide-ranging than fect local changes in cell shape or me- teractions could indirectly influence ac- the actin filament cytoskeleton. chanics. For example, pulsed cycles of tomyosin networks via effects on actin In the end, Chua et al. (1) propose contraction and retraction within indi- regulators whose activities are modu- that a complex of GTP-depleted dy- vidual cells of epithelial sheets were lated directly by lipids (23, 24). namin2 and cortactin act together to recently implicated in driving morphoge- Mature epithelial apical junctions are promote formation of robust actomyosin netic movements in Drosophila embryos highly dynamic structures, in part, be- networks that tightly constrict epithelial (19, 20). Could cycles of GTP hydrolysis cause intense vesicle traffic maintains cell–cell junctions. Complementary bio- junctional integrity and the polarized chemical studies of dynamin2, cortactin, epithelial state. If dynamin2 influences and actin filaments in vitro show that both endocytic traffic and actomyosin, complexes of nucleotide-free dynamin2 dynamin2 influences the then these dual roles must be coordi- and cortactin cross-link actin filaments contractile activity of nated in space and time. Chua et al. (1) in tight bundles (17). Because efficient propose that coordinating the endocytic contractility depends on both myosin II apical junctional and cytoskeletal activities of dynamin2 motor activity and the extent of filament might depend on dynamin2’s bound cross-linking within the actin network, actomyosin networks. guanine nucleotide. They suggest that one hypothesis to explain how dynamin2 nucleotide-specific interactions of dy- promotes apical constriction is that namin2 and either endocytic or cy- dynamin2-K44A and cortactin cross-link by dynamin2 temporally regulate acto- toskeletal effectors tips dynamin2 junctional actin filaments and, thereby, myosin networks? Consistent with its function toward either endocytosis or tune the actomyosin machinery in favor ability to couple GTP hydrolysis with actomyosin-based contractility. However, of a highly constricted state. Prominent constriction and fission of lipid tubules mechanisms by which dynamin2 juggles actomyosin-containing stress fibers were in vitro (21, 22), GTP hydrolysis by dy- its membrane remodeling and cytoskel- also assembled in fibroblasts expressing namin2 actively remodeled cross-linked etal activities are likely more complex. dynamin1-K44A (18), consistent with actin filaments in vitro (17). Filament Membrane remodeling by dynamins may this hypothesis. In contrast, actomyosin remodeling by dynamin2 GTPase activ- be intricately coordinated with its activi- arrays were poorly organized in osteo- ity changed the spatial organization of ties that influence actin filaments.
Load more

Recommended publications
  • Drosophila Ric-8 Interacts with the Gα12/13 Subunit, Concertina, During Activation of the Folded Gastrulation Pathway
    M BoC | ARTICLE Drosophila Ric-8 interacts with the Gα12/13 subunit, Concertina, during activation of the Folded gastrulation pathway Kimberly A. Petersa and Stephen L. Rogersa,b,c aDepartment of Biology and bCarolina Center for Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599; cLineberger Comprehensive Cancer Center, Chapel Hill, NC 27514 ABSTRACT Heterotrimeric G proteins, composed of α, β, and γ subunits, are activated by Monitoring Editor exchange of GDP for GTP on the Gα subunit. Canonically, Gα is stimulated by the guanine- Denise Montell nucleotide exchange factor (GEF) activity of ligand-bound G protein–coupled receptors. University of California, Santa Barbara However, Gα subunits may also be activated in a noncanonical manner by members of the Ric-8 family, cytoplasmic proteins that also act as GEFs for Gα subunits. We used a signaling Received: Nov 15, 2012 pathway active during Drosophila gastrulation as a model system to study Ric-8/Gα interac- Revised: Jul 18, 2013 Accepted: Aug 28, 2013 tions. A component of this pathway, the Drosophila Gα12/13 subunit, Concertina (Cta), is necessary to trigger actomyosin contractility during gastrulation events. Ric-8 mutants ex- hibit similar gastrulation defects to Cta mutants. Here we use a novel tissue culture system to study a signaling pathway that controls cytoskeletal rearrangements necessary for cellular morphogenesis. We show that Ric-8 regulates this pathway through physical interaction with Cta and preferentially interacts with inactive Cta and directs its localization within the cell. We also use this system to conduct a structure–function analysis of Ric-8 and identify key residues required for both Cta interaction and cellular contractility.
    [Show full text]
  • The Physical Mechanisms of Drosophila Gastrulation: Mesoderm and Endoderm Invagination
    | FLYBOOK DEVELOPMENT AND GROWTH The Physical Mechanisms of Drosophila Gastrulation: Mesoderm and Endoderm Invagination Adam C. Martin1 Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142 ORCID ID: 0000-0001-8060-2607 (A.C.M.) ABSTRACT A critical juncture in early development is the partitioning of cells that will adopt different fates into three germ layers: the ectoderm, the mesoderm, and the endoderm. This step is achieved through the internalization of specified cells from the outermost surface layer, through a process called gastrulation. In Drosophila, gastrulation is achieved through cell shape changes (i.e., apical constriction) that change tissue curvature and lead to the folding of a surface epithelium. Folding of embryonic tissue results in mesoderm and endoderm invagination, not as individual cells, but as collective tissue units. The tractability of Drosophila as a model system is best exemplified by how much we know about Drosophila gastrulation, from the signals that pattern the embryo to the molecular components that generate force, and how these components are organized to promote cell and tissue shape changes. For mesoderm invagination, graded signaling by the morphogen, Spätzle, sets up a gradient in transcriptional activity that leads to the expression of a secreted ligand (Folded gastrulation) and a transmembrane protein (T48). Together with the GPCR Mist, which is expressed in the mesoderm, and the GPCR Smog, which is expressed uniformly, these signals activate heterotrimeric G-protein and small Rho-family G-protein signaling to promote apical contractility and changes in cell and tissue shape. A notable feature of this signaling pathway is its intricate organization in both space and time.
    [Show full text]
  • Apical Sarcomere-Like Actomyosin Contracts Nonmuscle Drosophila Epithelial Cells
    Apical Sarcomere-like Actomyosin Contracts Nonmuscle Drosophila Epithelial Cells The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation Coravos, Jonathan S., and Adam C. Martin. “Apical Sarcomere- Like Actomyosin Contracts Nonmuscle Drosophila Epithelial Cells.” Developmental Cell 39, no. 3 (November 2016): 346–358. As Published http://dx.doi.org/10.1016/J.DEVCEL.2016.09.023 Publisher Elsevier BV Version Author's final manuscript Citable link http://hdl.handle.net/1721.1/116723 Terms of Use Creative Commons Attribution-NonCommercial-NoDerivs License Detailed Terms http://creativecommons.org/licenses/by-nc-nd/4.0/ HHS Public Access Author manuscript Author ManuscriptAuthor Manuscript Author Dev Cell Manuscript Author . Author manuscript; Manuscript Author available in PMC 2017 November 07. Published in final edited form as: Dev Cell. 2016 November 7; 39(3): 346–358. doi:10.1016/j.devcel.2016.09.023. Apical sarcomere-like actomyosin contracts nonmuscle Drosophila epithelial cells Jonathan S. Coravos1 and Adam C. Martin1 1 Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA Summary Actomyosin networks generate contractile force that changes cell and tissue shape. In muscle cells, actin filaments and myosin II appear in a polarized structure called a sarcomere, where myosin II is localized in the center. Nonmuscle cortical actomyosin networks are thought to contract when nonmuscle myosin II (myosin) is activated throughout a mixed-polarity actin network. Here, we identified a mutant version of the myosin-activating kinase, ROCK, that localizes diffusely, rather than centrally, in epithelial cell apices. Surprisingly, this mutant inhibits constriction, suggesting that centrally localized apical ROCK/myosin activity promotes contraction.
    [Show full text]
  • Volume Conservation Principle Involved in Cell Lengthening and Nucleus Movement During Tissue Morphogenesis
    Volume conservation principle involved in cell lengthening and nucleus movement during tissue morphogenesis Michael A. Gelbarta,b, Bing Hec, Adam C. Martinc,d, Stephan Y. Thibergea, Eric F. Wieschausc, and Matthias Kaschubea,e,1 aLewis-Sigler Institute for Integrative Genomics, Carl Icahn Laboratory, Princeton University, Princeton, NJ 08544; bGraduate Program in Biophysics, Harvard University, Boston, MA 02115; cDepartment of Molecular Biology, The Howard Hughes Medical Institute, Moffett Laboratory 435, Princeton University, Princeton, NJ 08544; dDepartment of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139; and eFrankfurt Institute for Advanced Studies, Faculty of Computer Science and Mathematics, Goethe University, D-60438 Frankfurt am Main, Germany Edited by Thomas D. Pollard, Yale University, New Haven, CT, and approved October 8, 2012 (received for review March 30, 2012) Tissue morphogenesis is the process in which coordinated move- the basal end, resulting in cells of stereotypical columnar shape ments and shape changes of large numbers of cells form tissues, (Fig. 1B, Left). When gastrulation starts, individual cells constrict organs, and the internal body structure. Understanding morphoge- at their apical end and undergo elongation. Cells then shorten and netic movements requires precise measurements of whole-cell shape widen their basal ends, transforming shapes from columnar to changes over time. Tissue folding and invagination are thought to be wedge-like (6, 10–12) (Fig. 1B, Right). Cell nuclei are initially close facilitated by apical constriction, but the mechanism by which to the apical surface but move basally during the early phase of changes near the apical cell surface affect changes along the entire furrow formation (6, 13).
    [Show full text]
  • GEF-H1 Functions in Apical Constriction and Cell Intercalations
    ß 2014. Published by The Company of Biologists Ltd | Journal of Cell Science (2014) 127, 2542–2553 doi:10.1242/jcs.146811 RESEARCH ARTICLE GEF-H1 functions in apical constriction and cell intercalations and is essential for vertebrate neural tube closure Keiji Itoh*, Olga Ossipova* and Sergei Y. Sokol` ABSTRACT 2013). Taken together, these cell behaviors are the main contributors to morphogenetic movements underlying vertebrate Rho family GTPases regulate many morphogenetic processes neurulation. during vertebrate development including neural tube closure. Here One of the crucial regulators of neural tube closure is non- we report a function for GEF-H1/Lfc/ArhGEF2, a RhoA-specific muscle myosin II (Rolo et al., 2009; Tullio et al., 2001). guanine nucleotide exchange factor that functions in neurulation Both intercalatory and constricting cell behaviors require in Xenopus embryos. Morpholino-mediated depletion of GEF-H1 reorganization of many cytoskeletal components and involve resulted in severe neural tube defects, which were rescued by dynamic changes in myosin II localization and activity (Lecuit GEF-H1 RNA. Lineage tracing of GEF-H1 morphants at different et al., 2011; Rauzi et al., 2010; Vicente-Manzanares et al., 2009). developmental stages revealed abnormal cell intercalation and Myosin II controls the contractile force by binding to, and sliding apical constriction, suggesting that GEF-H1 regulates these cell along, actin filaments. Myosin II has also been implicated in behaviors. Molecular marker analysis documented defects in a variety of cellular processes – such as cell junction stability, myosin II light chain (MLC) phosphorylation, Rab11 and F-actin nuclear movement, apical–basal protein targeting – yet there is accumulation in GEF-H1-depleted cells.
    [Show full text]
  • Cell Non-Autonomy Amplifies Disruption of Neurulation by Mosaic
    ARTICLE https://doi.org/10.1038/s41467-021-21372-4 OPEN Cell non-autonomy amplifies disruption of neurulation by mosaic Vangl2 deletion in mice ✉ Gabriel L. Galea 1,2 , Eirini Maniou 1, Timothy J. Edwards1, Abigail R. Marshall1, Ioakeim Ampartzidis 1, Nicholas D. E. Greene 1 & Andrew J. Copp 1 Post-zygotic mutations that generate tissue mosaicism are increasingly associated with severe congenital defects, including those arising from failed neural tube closure. Here we 1234567890():,; report that neural fold elevation during mouse spinal neurulation is vulnerable to deletion of the VANGL planar cell polarity protein 2 (Vangl2) gene in as few as 16% of neuroepithelial cells. Vangl2-deleted cells are typically dispersed throughout the neuroepithelium, and each non-autonomously prevents apical constriction by an average of five Vangl2-replete neigh- bours. This inhibition of apical constriction involves diminished myosin-II localisation on neighbour cell borders and shortening of basally-extending microtubule tails, which are known to facilitate apical constriction. Vangl2-deleted neuroepithelial cells themselves con- tinue to apically constrict and preferentially recruit myosin-II to their apical cell cortex rather than to apical cap localisations. Such non-autonomous effects can explain how post-zygotic mutations affecting a minority of cells can cause catastrophic failure of morphogenesis leading to clinically important birth defects. 1 Developmental Biology and Cancer, UCL GOS Institute of Child Health, London, UK. 2 Comparative Bioveterinary Sciences, Royal Veterinary College, ✉ London, UK. email: [email protected] NATURE COMMUNICATIONS | (2021) 12:1159 | https://doi.org/10.1038/s41467-021-21372-4 | www.nature.com/naturecommunications 1 ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-21372-4 eural tube (NT) defects such as spina bifida continue to as Xenopus neuroepithelium23–26.
    [Show full text]
  • Pax6-Dependent Shroom3 Expression Regulates Apical Constriction During Lens Placode Invagination Timothy F
    RESEARCH ARTICLE 405 Development 137, 405-415 (2010) doi:10.1242/dev.045369 © 2010. Published by The Company of Biologists Ltd Pax6-dependent Shroom3 expression regulates apical constriction during lens placode invagination Timothy F. Plageman, Jr1,2, Mei-I Chung3, Ming Lou4, April N. Smith1,2, Jeffrey D. Hildebrand5, John B. Wallingford3,6 and Richard A. Lang1,2,7,8,* SUMMARY Embryonic development requires a complex series of relative cellular movements and shape changes that are generally referred to as morphogenesis. Although some of the mechanisms underlying morphogenesis have been identified, the process is still poorly understood. Here, we address mechanisms of epithelial morphogenesis using the vertebrate lens as a model system. We show that the apical constriction of lens epithelial cells that accompanies invagination of the lens placode is dependent on Shroom3, a molecule previously associated with apical constriction during morphogenesis of the neural plate. We show that Shroom3 is required for the apical localization of F-actin and myosin II, both crucial components of the contractile complexes required for apical constriction, and for the apical localization of Vasp, a Mena family protein with F-actin anti-capping function that is also required for morphogenesis. Finally, we show that the expression of Shroom3 is dependent on the crucial lens-induction transcription factor Pax6. This provides a previously missing link between lens-induction pathways and the morphogenesis machinery and partly explains the absence of lens morphogenesis in Pax6-deficient mutants. KEY WORDS: Mena (Enah), Pax6, Shroom3, Vasp, Lens, Morphogenesis, Mouse, Chicken, Xenopus INTRODUCTION that contrasts, for example, with lens placode conditional deletion Embryonic development requires complex events in morphogenesis of Sox2, in which invagination is still initiated (Smith et al., 2009).
    [Show full text]
  • Gastrulation: Partaking of the Bottle Dispatch
    Current Biology, Vol. 13, R223–R225, March 18, 2003, ©2003 Elsevier Science Ltd. All rights reserved. DOI 10.1016/S0960-9822(03)00155-6 Gastrulation: PARtaking of the Bottle Dispatch Aaron P. Putzke and Joel H. Rothman constriction of their apical ends, resulting in bending of the sheet and their inward movement toward the opposite (basal) surface. The mechanics of such apical Gastrulation in C. elegans embryos involves constriction was modeled over 55 years ago [8] with ingression of individual cells, but is driven by apical brass bars and rubber bands representing a layer of constriction of the kind that promotes migration of epithelial cells: by changing the tension on one side of epithelial cell sheets. Recent work shows that PAR the layer, the sheet would buckle inward, thus mimick- proteins, known for their role in polarization and ing ingression. unequal cell division, are also associated with the Ingression by apical constriction may be energeti- polarization that establishes this apical constriction. cally more favorable than other means of gap closure, such as the purse-string model. A study using com- puter algorithms to mimic gastrulating embryos showed How poor are they who have not gastrulation! that, when a cell constricts apically, it propagates a What wound did ever heal but by ingression? wave through the surrounding sheet of cells, causing (apologies to William Shakespeare) an inward buckling [9]. Morphological support for apical constriction in a developing organism came from the observation of bottle cells, for example during We all begin as a cluster of rather featureless cells; our primary invagination of epithelial cells in sea urchins final forms are sculpted into specialized tissue layers [1], in which bottle cells have been shown to be essen- which achieve their final state by the concerted move- tial for gastrulation [2].
    [Show full text]
  • Endocytosis Is Required for Efficient Apical Constriction During Xenopus
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Current Biology 20, 253–258, February 9, 2010 ª2010 Elsevier Ltd All rights reserved DOI 10.1016/j.cub.2009.12.021 Report Endocytosis Is Required for Efficient Apical Constriction during Xenopus Gastrulation Jen-Yi Lee1,* and Richard M. Harland1,* To determine where endosomes traffic in bottle cells, we 1Department of Molecular and Cell Biology, labeled stage 9 embryos with biotin, quenched the reaction, University of California, Berkeley, Berkeley, CA 94720, USA and fixed the embryos at 30 min intervals (‘‘chase’’). As cells underwent AC, the number of endosomes also increased, strengthening the correlation between endocytosis and AC. Summary Endosomes trafficked away from the apical membrane, and some vesicles colocalized with the basolateral membrane Coordinated apical constriction (AC) in epithelial sheets (Figure 1D). drives tissue invagination [1, 2] and is required for diverse Previously, we showed that intact but not dynamic microtu- morphogenetic movements such as gastrulation [3], neuru- bules were required for AC [7]. If intact microtubules function as lation [4, 5], and organogenesis [6]. We showed previously tracks for endosomes, then nocodazole treatment should that actomyosin contractility drives AC in Xenopus laevis prevent endocytosis, whereas taxol treatment should not. bottle cells [7]; however, it remained unclear whether it Indeed, in nocodazole-treated embryos, endosomes remained does so in concert with other processes. Here we report at the apical membrane (see Figure S1 available online). In that endocytosis-driven membrane remodeling is required contrast, taxol-treated embryos exhibited internalized vesicles for efficient AC.
    [Show full text]
  • Sonic Hedgehog Signaling Directs Patterned Cell Remodeling During
    RESEARCH ARTICLE Sonic hedgehog signaling directs patterned cell remodeling during cranial neural tube closure Eric R Brooks1, Mohammed Tarek Islam1, Kathryn V Anderson2, Jennifer A Zallen1* 1Howard Hughes Medical Institute and Developmental Biology Program, Sloan Kettering Institute, New York, United States; 2Developmental Biology Program, Sloan Kettering Institute, New York, United States Abstract Neural tube closure defects are a major cause of infant mortality, with exencephaly accounting for nearly one-third of cases. However, the mechanisms of cranial neural tube closure are not well understood. Here, we show that this process involves a tissue-wide pattern of apical constriction controlled by Sonic hedgehog (Shh) signaling. Midline cells in the mouse midbrain neuroepithelium are flat with large apical surfaces, whereas lateral cells are taller and undergo synchronous apical constriction, driving neural fold elevation. Embryos lacking the Shh effector Gli2 fail to produce appropriate midline cell architecture, whereas embryos with expanded Shh signaling, including the IFT-A complex mutants Ift122 and Ttc21b and embryos expressing activated Smoothened, display apical constriction defects in lateral cells. Disruption of lateral, but not midline, cell remodeling results in exencephaly. These results reveal a morphogenetic program of patterned apical constriction governed by Shh signaling that generates structural changes in the developing mammalian brain. *For correspondence: Introduction [email protected] Neural tube closure defects are among the most common structural birth defects, occurring in 1 in 1000 pregnancies worldwide (Wallingford et al., 2013; Zaganjor et al., 2016). During develop- Competing interests: The ment, neuroepithelial cells undergo extensive remodeling to transform a flat sheet into a fully closed authors declare that no tube that gives rise to the brain and spinal cord of the animal.
    [Show full text]
  • Rho Signaling Pathway and Apical Constriction in the Early Lens Placode
    ' 2011 Wiley-Liss, Inc. genesis 00:1–12 (2011) ARTICLE Rho Signaling Pathway and Apical Constriction in the Early Lens Placode Ricardo Moraes Borges,1 Marcelo Lazzaron Lamers,2 Fabio Luis Forti,3 Marinilce Fagundes dos Santos,1 and Chao Yun Irene Yan1* 1Department of Cell and Developmental Biology, Institute of Biomedical Sciences, University of Sa˜ o Paulo, Sa˜ o Paulo, SP, Brazil 2Departamento de Cieˆ ncias Morfolo´ gicas do Instituto de Cieˆ ncias Ba´ sicas da Sau´ de, Universidade Federal do Rio Grande do Sul, Brazil 3Departamento de Bioquimica, Instituto de Quimica, Universidade de Sao Paulo, Sao Paulo, Brazil Received 18 October 2010; Revised 5 January 2011; Accepted 16 January 2011 Summary: Epithelial invagination in many model sys- a classical experimental paradigm in developmental tems is driven by apical cell constriction, mediated by biology. The study of its development has contributed actin and myosin II contraction regulated by GTPase to our understanding of various issues pertinent to the activity. Here we investigate apical constriction during field. In particular, the various morphological changes chick lens placode invagination. Inhibition of actin poly- that the lens placode undergoes at different stages of de- merization and myosin II activity by cytochalasin D or blebbistatin prevents lens invagination. To further verify velopment illustrate its usefulness as a model system for if lens placode invaginate through apical constriction, embryonic morphogenesis. we analyzed the role of Rho-ROCK pathway. Rho In brief, prior to the appearance of the placodes, GTPases expression at the apical portion of the lens the cells of the head ectoderm are cuboidal.
    [Show full text]
  • Wnt Ligand/Frizzled 2 Receptor Signaling Regulates Tube Shape and Branch-Point Formation in the Lung Through Control of Epithelial Cell Shape
    Wnt ligand/Frizzled 2 receptor signaling regulates tube shape and branch-point formation in the lung through control of epithelial cell shape Rachel S. Kadzika, Ethan David Cohenb, Michael P. Morleyc, Kathleen M. Stewartc,d, Min Min Luc, and Edward E. Morriseya,c,d,e,1 Departments of aCell and Developmental Biology and cMedicine, dCardiovascular Institute, and eInstitute for Regenerative Medicine, University of Pennsylvania, Philadelphia, PA 19104; and bDivision of Endocrinology, Department of Medicine, University of Rochester, Rochester, NY 14642 Edited* by Brigid L. M. Hogan, Duke University Medical Center, Durham, NC, and approved July 16, 2014 (received for review April 11, 2014) Changing the morphology of a simple epithelial tube to form a apical expression of phospho-myosin light chain 2 (pMLC2) in- highly ramified branching network requires changes in cell behavior dicative of the decreased Rho signaling that is required for that lead to tissue-wide changes in organ shape. How epithelial cells thickening of the lung epithelium before new branch formation. in branched organs modulate their shape and behavior to promote Importantly, activation of Rho signaling can rescue the loss of bending and sculpting of the epithelial sheet is not well understood, Fzd2 signaling during lung branching morphogenesis. Together, and the mechanisms underlying this process remain obscure. We our data highlight a previously unappreciated mechanism in the show that the Wnt receptor Frizzled 2 (Fzd2) is required for domain formation of branched networks by the control of epithelial cell branch formation during the initial establishment of the respiratory shape through Wnt signaling. tree. Live imaging and transcriptome analysis of lung-branching morphogenesis demonstrate that Fzd2 promotes changes in epi- Results thelial cell length and shape.
    [Show full text]