@article{tyree_bellingham-johnstun_martinez-baird_laplante_2024, title={The Myosin-V Myo51 and Alpha-Actinin Ain1p Cooperate during Contractile Ring Assembly and Disassembly in Fission Yeast Cytokinesis}, volume={10}, ISSN={["2309-608X"]}, DOI={10.3390/jof10090647}, abstractNote={Cytokinesis is driven in part by the constriction of a ring of actin filaments, myosin motors and other proteins. In fission yeast, three myosins contribute to cytokinesis including a Myosin-V Myo51. As Myosin-Vs typically carry cargo along actin filaments, the role of Myo51 in cytokinesis remains unclear. The previous work suggests that Myo51 may crosslink actin filaments. We hypothesized that if Myo51 crosslinks actin filaments, cells carrying double deletions of}, number={9}, journal={JOURNAL OF FUNGI}, author={Tyree, Zoe L. and Bellingham-Johnstun, Kimberly and Martinez-Baird, Jessica and Laplante, Caroline}, year={2024}, month={Sep} }
 @article{bellingham-johnstun_tyree_martinez-baird_thorn_laplante_2023, title={Actin-Microtubule Crosstalk Imparts Stiffness to the Contractile Ring in Fission Yeast}, volume={12}, ISSN={["2073-4409"]}, DOI={10.3390/cells12060917}, abstractNote={Actin–microtubule interactions are critical for cell division, yet how these networks of polymers mutually influence their mechanical properties and functions in live cells remains unknown. In fission yeast, the post-anaphase array (PAA) of microtubules assembles in the plane of the contractile ring, and its assembly relies on the Myp2p-dependent recruitment of Mto1p, a component of equatorial microtubule organizing centers (eMTOCs). The general organization of this array of microtubules and the impact on their physical attachment to the contractile ring remain unclear. We found that Myp2p facilitates the recruitment of Mto1p to the inner face of the contractile ring, where the eMTOCs polymerize microtubules without their direct interaction. The PAA microtubules form a dynamic polygon of Ase1p crosslinked microtubules inside the contractile ring. The specific loss of PAA microtubules affects the mechanical properties of the contractile ring of actin by lowering its stiffness. This change in the mechanical properties of the ring has no measurable impact on cytokinesis or on the anchoring of the ring. Our work proposes that the PAA microtubules exploit the contractile ring for their assembly and function during cell division, while the contractile ring may receive no benefit from these interactions.}, number={6}, journal={CELLS}, author={Bellingham-Johnstun, Kimberly and Tyree, Zoe L. and Martinez-Baird, Jessica and Thorn, Annelise and Laplante, Caroline}, year={2023}, month={Mar} }
 @article{bellingham-johnstun_thorn_belmonte_laplante_2023, title={Microtubule competition and cell growth recenter the nucleus after anaphase in fission yeast}, volume={34}, ISSN={["1939-4586"]}, DOI={10.1091/mbc.E23-01-0034}, abstractNote={ Active centering of the nucleus by microtubules is critical for symmetrical cell division in fission yeast. We determined that microtubule competition and cell growth influence this mechanism, resulting in the slow recentering of the nucleus after anaphase. }, number={8}, journal={MOLECULAR BIOLOGY OF THE CELL}, author={Bellingham-Johnstun, Kimberly and Thorn, Annelise and Belmonte, Julio M. and Laplante, Caroline}, year={2023}, month={Jul} }
 @article{bellingham-johnstun_commer_levesque_tyree_laplante_2022, title={Imp2p forms actin-dependent clusters and imparts stiffness to the contractile ring}, volume={33}, ISSN={["1939-4586"]}, DOI={10.1091/mbc.E22-06-0221}, abstractNote={ The contractile ring must anchor to the plasma membrane and cell wall to transmit its tension. We combine single molecule localization microscopy and laser ablation to reveal the molecular organization of Imp2p, a putative protein anchor, and its role in the mechanical properties of the contractile ring. }, number={14}, journal={MOLECULAR BIOLOGY OF THE CELL}, author={Bellingham-Johnstun, Kimberly and Commer, Blake and Levesque, Brie and Tyree, Zoe L. and Laplante, Caroline}, year={2022}, month={Dec} }
 @article{moshtohry_bellingham-johnstun_elting_laplante_2022, title={Laser ablation reveals the impact of Cdc15p on the stiffness of the contractile ring}, volume={33}, ISSN={["1939-4586"]}, DOI={10.1091/mbc.E21-10-0515}, abstractNote={ We use laser ablation to sever the constricting contractile ring of fission yeast cells and reveal the impact of Cdc15p, a putative anchoring protein, on its mechanical properties. Our work suggests that Cdc15p, and thus the anchoring mechanism, impacts the stiffness of the contractile ring more than the viscous drag. }, number={6}, journal={MOLECULAR BIOLOGY OF THE CELL}, author={Moshtohry, Mohamed and Bellingham-Johnstun, Kimberly and Elting, Mary Williard and Laplante, Caroline}, year={2022}, month={May} }
 @article{amaral_mcqueen_bellingham-johnstun_poston_darville_nagarajan_laplante_kaser_2021, title={Host-Pathogen Interactions of Chlamydia trachomatis in Porcine Oviduct Epithelial Cells}, volume={10}, ISSN={["2076-0817"]}, url={https://www.mdpi.com/2076-0817/10/10/1270}, DOI={10.3390/pathogens10101270}, abstractNote={Chlamydia trachomatis (Ct) causes the most prevalent bacterial sexually transmitted disease leading to ectopic pregnancy and infertility. Swine not only have many similarities to humans, but they are also susceptible to Ct. Despite these benefits and the ease of access to primary tissue from this food animal, in vitro research in swine has been underutilized. This study will provide basic understanding of the Ct host–pathogen interactions in porcine oviduct epithelial cells (pOECs)—the counterparts of human Fallopian tube epithelial cells. Using NanoString technology, flow cytometry, and confocal and transmission-electron microscopy, we studied the Ct developmental cycle in pOECs, the cellular immune response, and the expression and location of the tight junction protein claudin-4. We show that Ct productively completes its developmental cycle in pOECs and induces an immune response to Ct similar to human cells: Ct mainly induced the upregulation of interferon regulated genes and T-cell attracting chemokines. Furthermore, Ct infection induced an accumulation of claudin-4 in the Ct inclusion with a coinciding reduction of membrane-bound claudin-4. Downstream effects of the reduced membrane-bound claudin-4 expression could potentially include a reduction in tight-junction expression, impaired epithelial barrier function as well as increased susceptibility to co-infections. Thereby, this study justifies the investigation of the effect of Ct on tight junctions and the mucosal epithelial barrier function. Taken together, this study demonstrates that primary pOECs represent an excellent in vitro model for research into Ct pathogenesis, cell biology and immunity.}, number={10}, journal={PATHOGENS}, publisher={MDPI AG}, author={Amaral, Amanda F. and McQueen, Bryan E. and Bellingham-Johnstun, Kimberly and Poston, Taylor B. and Darville, Toni and Nagarajan, Uma M. and Laplante, Caroline and Kaser, Tobias}, year={2021}, month={Oct} }
 @article{bellingham-johnstun_anders_ravi_bruinsma_laplante_2021, title={Molecular organization of cytokinesis node predicts the constriction rate of the contractile ring}, volume={220}, ISSN={["1540-8140"]}, DOI={10.1083/jcb.202008032}, abstractNote={The molecular organization of cytokinesis proteins governs contractile ring function. We used single molecule localization microscopy in live cells to elucidate the molecular organization of cytokinesis proteins and relate it to the constriction rate of the contractile ring. Wild-type fission yeast cells assemble contractile rings by the coalescence of cortical proteins complexes called nodes whereas cells without Anillin/Mid1p (Δmid1) lack visible nodes yet assemble contractile rings competent for constriction from the looping of strands. We leveraged the Δmid1 contractile ring assembly mechanism to determine how two distinct molecular organizations, nodes versus strands, can yield functional contractile rings. Contrary to previous interpretations, nodes assemble in Δmid1 cells. Our results suggest that Myo2p heads condense upon interaction with actin filaments and an excess number of Myo2p heads bound to actin filaments hinders constriction thus reducing the constriction rate. Our work establishes a predictive correlation between the molecular organization of nodes and the behavior of the contractile ring.}, number={3}, journal={JOURNAL OF CELL BIOLOGY}, author={Bellingham-Johnstun, Kimberly and Anders, Erica Casey and Ravi, John and Bruinsma, Christina and Laplante, Caroline}, year={2021}, month={Mar} }
 @article{laplante_2018, title={Building the contractile ring from the ground up: a lesson in perseverance and scientific creativity}, volume={10}, ISSN={1867-2450 1867-2469}, url={http://dx.doi.org/10.1007/S12551-018-0482-8}, DOI={10.1007/S12551-018-0482-8}, abstractNote={This contribution to the Festschrift for Professor Thomas (Tom) D. Pollard focuses on his work on the elucidation of the protein organization within the cytokinetic nodes, protein assemblies, precursors to the contractile ring. In particular, this work highlights recent discoveries in the molecular organization of the proteins that make the contractile machine in fission yeast using advanced microscopy techniques. One of the main aspects of Tom's research philosophy that marked my career as one of his trainees is his embrace of interdisciplinary approaches to research. The cost of interdisciplinary research is to be willing to step out of our technical comfort zone to learn a new set of tools. The payoff of interdisciplinary research is the expansion our realm of possibilities by bringing new creative tools and ideas to push our research program forward. The rewarding outcomes of this work under Tom's mentorship were the molecular model of the cytokinetic node and the development of new techniques to unravel the structure of multi-protein complexes in live cells. Together, these findings open a new set of questions about the mechanism of cytokinesis and provide creative tools to address them.}, number={6}, journal={Biophysical Reviews}, publisher={Springer Science and Business Media LLC}, author={Laplante, Caroline}, year={2018}, month={Nov}, pages={1491–1497} }
 @article{laplante_2018, title={Resolving single-actin filaments within the contractile ring of fission yeast}, volume={115}, ISSN={["0027-8424"]}, DOI={10.1073/pnas.1722624115}, abstractNote={Cell division is an essential step in the life of all cells. Fungi, amoeboid, and mammalian cells divide by the assembly and constriction of a contractile ring of actin, myosin, and other highly conserved proteins (1). The mechanism of cytokinesis is best understood in the fission yeast Schizosaccharomyces pombe . Combined years of research have identified more than 100 genes involved in building and constricting the contractile ring (1). Quantitative fluorescence imaging techniques have been developed to calculate the local and global concentration of endogenously tagged proteins involved in cytokinesis (2, 3). Mathematical models were built using these quantitative data to explain the principles that govern the mechanisms of contractile ring assembly (4) and constriction (5). These mathematical models were limited by the lack of information about the organization of proteins within the contractile ring.

How the proteins involved in building and constricting the contractile ring organize to generate tension force is still vastly unknown. Recently, superresolution imaging has enabled us to capture the molecular organization of proteins within the constricting contractile ring in fixed cells (6), and high-speed superresolution imaging combined with quantitative analyses has provided molecular organization of protein complexes within the assembling and constricting contractile ring in live cells (7). Even with this combined knowledge, there are still many aspects of the general mechanisms of contractile ring assembly, constriction, and disassembly that we do not understand (8). One remaining enigma about cytokinesis is the how the network of actin filaments, the most abundant protein of the contractile ring, is structured during constriction. Actin filaments within the contractile ring are polymerized, severed, depolymerized, and pulled upon by the action of many other actin-binding proteins present in the cytokinetic machinery. Together, these modifications to the actin network generate tension force that is transmitted to the ingressing plasma membrane … 

[↵][1]1Email: claplan{at}ncsu.edu.

 [1]: #xref-corresp-1-1}, number={7}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Laplante, Caroline}, year={2018}, month={Feb}, pages={1403–1405} }
 @article{laplante_pollard_2017, title={Response to Zambon et al.}, volume={27}, ISSN={0960-9822}, url={http://dx.doi.org/10.1016/J.CUB.2016.12.025}, DOI={10.1016/J.CUB.2016.12.025}, abstractNote={Stimulated by our 2015 Current Biology paper [1Laplante C. Berro J. Karatekin E. Hernandez-Leyva A. Lee R. Pollard T.D. Three myosins contribute uniquely to the assembly and constriction of the fission yeast cytokinetic contractile ring.Curr. Biol. 2015; 25: 1955-1965Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar], Zambon et al. reinvestigated how three myosin isoforms participate in the formation and constriction of the contractile ring in fission yeast. Our paper presented evidence that these myosin isoforms have distinct roles: “Conventional myosin-II Myo2 is crucial to ring assembly, unconventional myosin-II Myp2 is most important for ring constriction, and type V myosin Myo51 aids the other two myosins.” Zambon et al. used different markers to reexamine the contributions of the three myosins to cytokinesis and concluded “that Myo2p is the major motor involved in ring contraction in S. pombe.” Here, we show that most of the differences observed by Zambon et al. can be attributed to their use of the Rlc1p-3GFP marker, which genetically interacts with myo2-E1.}, number={3}, journal={Current Biology}, publisher={Elsevier BV}, author={Laplante, Caroline and Pollard, Thomas D.}, year={2017}, month={Feb}, pages={R101–R102} }
 @article{laplante_huang_tebbs_bewersdorf_pollard_2016, title={Molecular organization of cytokinesis nodes and contractile rings by super-resolution fluorescence microscopy of live fission yeast}, volume={113}, ISSN={0027-8424 1091-6490}, url={http://dx.doi.org/10.1073/PNAS.1608252113}, DOI={10.1073/PNAS.1608252113}, abstractNote={Significance
          Cell division occurs by the assembly and constriction of a ring of actin and myosin; however, the organization of proteins within cytokinetic apparatus is still unknown. Without better information about the organization of contractile rings, we cannot understand how they assemble or constrict. In fission yeast, cytokinetic proteins are first recruited around the equator as cortical spots, called nodes, that coalesce into a ring. Here we used high-speed quantitative fluorescence photoactivation localization microscopy to obtain a molecular model of this basic cytokinetic unit. Nodes are discrete structures with distinct distributions of six different proteins. Nodes persist in contractile rings and move around the circumference as the ring constricts.}, number={40}, journal={Proceedings of the National Academy of Sciences}, publisher={Proceedings of the National Academy of Sciences}, author={Laplante, Caroline and Huang, Fang and Tebbs, Irene R. and Bewersdorf, Joerg and Pollard, Thomas D.}, year={2016}, month={Sep}, pages={E5876–E5885} }
 @article{laplante_berro_karatekin_hernandez-leyva_lee_pollard_2015, title={Three Myosins Contribute Uniquely to the Assembly and Constriction of the Fission Yeast Cytokinetic Contractile Ring}, volume={25}, ISSN={0960-9822}, url={http://dx.doi.org/10.1016/J.CUB.2015.06.018}, DOI={10.1016/J.CUB.2015.06.018}, abstractNote={Cytokinesis in fission yeast cells depends on conventional myosin-II (Myo2) to assemble and constrict a contractile ring of actin filaments. Less is known about the functions of an unconventional myosin-II (Myp2) and a myosin-V (Myo51) that are also present in the contractile ring. Myo2 appears in cytokinetic nodes around the equator 10 min before spindle pole body separation (cell-cycle time, −10 min) independent of actin filaments, followed by Myo51 at time zero and Myp2 at time +20 min, both located between nodes and dependent on actin filaments. We investigated the contributions of these three myosins to cytokinesis using a severely disabled mutation of the essential myosin-II heavy-chain gene (myo2-E1) and deletion mutations of the other myosin heavy-chain genes. Cells with only Myo2 assemble contractile rings normally. Cells with either Myp2 or Myo51 alone can assemble nodes and actin filaments into contractile rings but complete assembly later than normal. Both Myp2 and Myo2 contribute to constriction of fully assembled rings at rates 55% that of normal in cells relying on Myp2 alone and 25% that of normal in cells with Myo2 alone. Myo51 alone cannot constrict rings but increases the constriction rate by Myo2 in Δmyp2 cells or Myp2 in myo2-E1 cells. Three myosins function in a hierarchal, complementary manner to accomplish cytokinesis, with Myo2 and Myo51 taking the lead during contractile ring assembly and Myp2 making the greatest contribution to constriction.}, number={15}, journal={Current Biology}, publisher={Elsevier BV}, author={Laplante, Caroline and Berro, Julien and Karatekin, Erdem and Hernandez-Leyva, Ariel and Lee, Rachel and Pollard, Thomas D.}, year={2015}, month={Aug}, pages={1955–1965} }
 @article{huang_laplante_lin_pollard_bewersdorf_2015, title={Video-Rate Super Resolution Microscopy in Living Cells}, volume={108}, ISSN={0006-3495}, url={http://dx.doi.org/10.1016/J.BPJ.2014.11.2599}, DOI={10.1016/J.BPJ.2014.11.2599}, abstractNote={Super resolution microscopy based on single-molecule localization relies on precise and accurate localization of large numbers of single-molecules. However, the necessity of accumulating large numbers of localization estimates limits the time resolution typically to seconds to minutes1,2. Two major limitations are the acquisition speed and the photon budget. Replacing the usually used EMCCD with a recently introduced sCMOS camera results in leaps in both acquisition speed and effective quantum efficiency. However, the intrinsic pixel-dependent Gaussian noise of the sCMOS cameras introduces localization artifacts and greatly reduces the reliability of the results. Here, we present a set of specially designed methods that characterize an sCMOS camera for the first time and allow for unbiased and precise localization analysis. Using this method we demonstrate Cramer-Rao lower bound-limited single-molecule localization with an sCMOS camera. Combining the novel algorithm with a recently developed multi-emitter fitting algorithm3, We shortens the typical acquisition time for fixed samples by up to two orders of magnitude without compromising the field of view. Furthermore, we demonstrate localization-based super-resolution microscopy in live cells by monitoring dynamics of protein clusters, vesicles and organelles at a temporal resolution from 2 to 30 frames per second4. These methods allowed us to investigate cytokinetic apparatus in live fission yeast at 20-30 nm resolution. In general, the significantly improved temporal resolution allows super resolution imaging of a large range of dynamic events in living cells. 1. Patterson, G., Davidson, M., Manley, S. & Lippincott-Schwartz, J. Annu. Rev. Phys. Chem.61, 345-67 (2010). 2. Gould, T. J., Hess, S. T. & Bewersdorf, J. Annu. Rev. Biomed. Eng.14, 231-54 (2012). 3. Huang, F., Schwartz, S. L., Byars, J. M. & Lidke, K. A. Biomed. Opt. Express 2, 1377-93 (2011). 4. Huang, F. et al.Nat. Methods 10, 653-8 (2013).}, number={2}, journal={Biophysical Journal}, publisher={Elsevier BV}, author={Huang, Fang and Laplante, Caroline E. and Lin, Yu and Pollard, Thomas D. and Bewersdorf, Joerg}, year={2015}, month={Jan}, pages={475a} }
 @article{chin_stachowiak_laplante_karatekin_pollard_o'shaughnessy_2014, title={Experimental Measurement and Simulations of the Cytokinetic Ring Tension in Fission Yeast}, volume={106}, ISSN={0006-3495}, url={http://dx.doi.org/10.1016/J.BPJ.2013.11.1003}, DOI={10.1016/J.BPJ.2013.11.1003}, abstractNote={Cytokinesis in animals and fungi requires the assembly and constriction of an actomyosin contractile ring at the site of cell division, but the ring tension, the ring's principal mechanical property, has rarely been measured. Thus it has not been possible to relate the organization of the ring to its principal function, and the mechanism of ring constriction remains poorly understood. Here we combined experimental measurement and mathematical modeling to characterize the tension of the cytokinetic contractile ring and its relation to organization. We used Schizosaccharomyces pombe protoplasts, whose cell walls have been enzymatically digested, to measure the tension. Based on extensive biochemical and genetic characterization of the components of the S. pombe ring, we developed a detailed computer simulation incorporating the key components. The simulation calculated the tension and organization of the ring for direct comparison with our experiments. We report the first measurements of contractile ring tension in fission yeast, using micropipette aspiration of protoplast cell membranes and optical microscopy analysis of membrane deformation by the tense ring as it constricts. The measured values are in close agreement with our ring simulations. The simulations show that the ring components undergo a remarkable process of continuous self-organization into a tight tension-generating bundle. The bundle produces high tension by orienting actin filaments parallel to the ring, and by concentrating actin filaments and myosin-II clusters to enhance the number of force-producing interactions. The self-organization naturally provides the mechanism to continuously remodel the ring as it constricts without loss of tension, a long-standing puzzle concerning the mechanism of ring constriction.}, number={2}, journal={Biophysical Journal}, publisher={Elsevier BV}, author={Chin, Harvey F. and Stachowiak, Matthew R. and Laplante, Caroline and Karatekin, Erdem and Pollard, Thomas D. and O'Shaughnessy, Ben}, year={2014}, month={Jan}, pages={177a} }
 @article{stachowiak_laplante_chin_guirao_karatekin_pollard_o’shaughnessy_2014, title={Mechanism of Cytokinetic Contractile Ring Constriction in Fission Yeast}, volume={29}, ISSN={1534-5807}, url={http://dx.doi.org/10.1016/J.DEVCEL.2014.04.021}, DOI={10.1016/J.DEVCEL.2014.04.021}, abstractNote={Cytokinesis involves constriction of a contractile actomyosin ring. The mechanisms generating ring tension and setting the constriction rate remain unknown because the organization of the ring is poorly characterized, its tension was rarely measured, and constriction is coupled to other processes. To isolate ring mechanisms, we studied fission yeast protoplasts, in which constriction occurs without the cell wall. Exploiting the absence of cell wall and actin cortex, we measured ring tension and imaged ring organization, which was dynamic and disordered. Computer simulations based on the amounts and biochemical properties of the key proteins showed that they spontaneously self-organize into a tension-generating bundle. Together with rapid component turnover, the self-organization mechanism continuously reassembles and remodels the constricting ring. Ring constriction depended on cell shape, revealing that the ring operates close to conditions of isometric tension. Thus, the fission yeast ring sets its own tension, but other processes set the constriction rate.}, number={5}, journal={Developmental Cell}, publisher={Elsevier BV}, author={Stachowiak, Matthew R. and Laplante, Caroline and Chin, Harvey F. and Guirao, Boris and Karatekin, Erdem and Pollard, Thomas D. and O’Shaughnessy, Ben}, year={2014}, month={Jun}, pages={547–561} }
 @article{stachowiak_laplante_pollard_o'shaughnessy_2012, title={The Role of the Contractile Ring during Cytokinesis}, volume={102}, ISSN={0006-3495}, url={http://dx.doi.org/10.1016/j.bpj.2011.11.1202}, DOI={10.1016/j.bpj.2011.11.1202}, abstractNote={Cytokinesis in animals and fungi involves constriction of an actomyosin contractile ring, but the constriction mechanisms and the role of the ring are not established. The constriction rate could be determined only by the properties and internal dynamics of the ring itself (a "dynamically autonomous" mechanism) as suggested by recent experiments on C. elegans embryos. Alternatively, the ring constriction rate could be set by coupled processes that occur simultaneously with constriction (a "dynamically coupled" mechanism). In fission yeast constriction occurs simultaneously with septation, the poorly understood process of cell wall growth in the wake of the constricting ring. To isolate the ring constriction mechanism, we combined mathematical modeling with experiments on fission yeast protoplasts which lack cell wall and adopt a rounded shape. Protoplasts assembled functional contractile rings that constricted without septation by sliding along the plasma membrane without dividing the cell. Because we could manipulate the shapes of protoplast cells, we could test the influence of cell shape on ring constriction dynamics and distinguish between dynamically autonomous and dynamically coupled constriction dynamics. In compressed protoplasts that had a partially flattened shape, contractile rings adopted characteristic bent shapes during constriction that were in remarkably close quantitative and parameter-free agreement with a mathematical model that assumed the ring produces tension but its constriction rate is set by the sliding of ring anchors in the membrane. Thus, ring constriction in fission yeast protoplasts is dynamically coupled: the ring does not set its own constriction rate. Dynamically autonomous models could not reproduce our experimental observations. Our results suggest that in normal yeast cells the constriction rate is determined by the septum growth rate or other coupled process and the role of the ring could be to exert tension on the septum to regulate its growth.}, number={3}, journal={Biophysical Journal}, publisher={Elsevier BV}, author={Stachowiak, Matthew R. and Laplante, Caroline and Pollard, Thomas D. and O'Shaughnessy, Ben}, year={2012}, month={Jan}, pages={219a} }
 @article{laplante_nilson_2011, title={Asymmetric distribution of Echinoid defines the epidermal leading edge during Drosophila dorsal closure}, volume={192}, ISSN={1540-8140 0021-9525}, url={http://dx.doi.org/10.1083/jcb.201009022}, DOI={10.1083/jcb.201009022}, abstractNote={During Drosophila melanogaster dorsal closure, lateral sheets of embryonic epidermis assemble an actomyosin cable at their leading edge and migrate dorsally over the amnioserosa, converging at the dorsal midline. We show that disappearance of the homophilic cell adhesion molecule Echinoid (Ed) from the amnioserosa just before dorsal closure eliminates homophilic interactions with the adjacent dorsal-most epidermal (DME) cells, which comprise the leading edge. The resulting planar polarized distribution of Ed in the DME cells is essential for the localized accumulation of actin regulators and for actomyosin cable formation at the leading edge and for the polarized localization of the scaffolding protein Bazooka/PAR-3. DME cells with uniform Ed fail to assemble a cable and protrude dorsally, suggesting that the cable restricts dorsal migration. The planar polarized distribution of Ed in the DME cells thus provides a spatial cue that polarizes the DME cell actin cytoskeleton, defining the epidermal leading edge and establishing its contractile properties.}, number={2}, journal={The Journal of Cell Biology}, publisher={Rockefeller University Press}, author={Laplante, Caroline and Nilson, Laura A.}, year={2011}, month={Jan}, pages={335–348} }
 @article{stachowiak_laplante_guirao_garcia_pollard_o'shaughnessy_2011, title={Mechanisms of Cytokinetic Ring Constriction in Fission Yeast}, volume={100}, ISSN={0006-3495}, url={http://dx.doi.org/10.1016/j.bpj.2010.12.2612}, DOI={10.1016/j.bpj.2010.12.2612}, abstractNote={Cytokinesis, the physical process of cell division, is accomplished by constriction of an actomyosin ring in eukaryotic cells. Here we combined mathematical modeling and experiment to study ring constriction in fission yeast, a model organism as many ring components have been identified and their concentrations measured. The ring model implemented random actomyosin organization, consistent with experiment, and actin turnover mediated by formin and cofilin severing proteins with parameters determined by experimental measurements of turnover rates. An obstacle to quantitative modeling is that ring constriction is tightly coupled to the poorly understood process of septation, the deposition of new cell wall in the wake of the constricting ring. Thus we studied yeast protoplasts whose cell walls have been enzymatically digested. We found that protoplasts contain ring precursor nodes similar to normal cells and assemble functional contractile rings that constrict without septation by sliding along the plasma membrane. Thus we could directly compare model predicted ring constriction profiles to experiment. Using this approach we found constriction is driven by tensions ∼14-25 pN, far less than those measured in animal cells, and the strength of ring-membrane anchoring during constriction is ∼9 times the value of all the precursor nodes combined. The model showed ring tension requires actin anchoring and is maximized when the barbed ends are anchored. The tension magnitude is determined by a measurable statistical characteristic of the actomyosin spatial organization which quantifies actin-myosin correlations and describes the degree to which the organization possesses the optimal tension-generating sarcomeric architecture of muscle. Consistent with experiment, suppression of the actin polymerization rate increased the ring constriction time because actin filaments are shorter and hence actin-myosin coupling and tension are diminished. Thus, the model articulates a mechanistic relationship between organization, turnover kinetics and tension.}, number={3}, journal={Biophysical Journal}, publisher={Elsevier BV}, author={Stachowiak, Matthew R. and Laplante, Caroline and Guirao, Boris and Garcia, Patricia and Pollard, Thomas D. and O'Shaughnessy, Ben}, year={2011}, month={Feb}, pages={443a} }
 @article{laplante_paul_beitel_nilson_2010, title={Echinoid regulates tracheal morphology and fusion cell fate in Drosophila}, volume={239}, ISSN={1058-8388}, url={http://dx.doi.org/10.1002/dvdy.22386}, DOI={10.1002/dvdy.22386}, abstractNote={AbstractMorphogenesis of the Drosophila embryonic trachea involves a stereotyped pattern of epithelial tube branching and fusion. Here, we report unexpected phenotypes resulting from maternal and zygotic (M/Z) loss of the homophilic cell adhesion molecule Echinoid (Ed), as well as the subcellular localization of Ed in the trachea. edM/Z embryos have convoluted trachea reminiscent of septate junction (SJ) and luminal matrix mutants. However, Ed does not localize to SJs, and edM/Z embryos have intact SJs and show normal luminal accumulation of the matrix‐modifying protein Vermiform. Surprisingly, tracheal length is not increased in edM/Z mutants, but a previously undescribed combination of reduced intersegmental spacing and deep epidermal grooves produces a convoluted tracheal phenotype. In addition, edM/Z mutants have unique fusion defects involving supernumerary fusion cells, ectopic fusion events and atypical branch breaks. Tracheal‐specific expression of Ed rescues these fusion defects, indicating that Ed acts in trachea to control fusion cell fate. Developmental Dynamics 239:2509–2519, 2010. © 2010 Wiley‐Liss, Inc.}, number={9}, journal={Developmental Dynamics}, publisher={Wiley}, author={Laplante, Caroline and Paul, Sarah M. and Beitel, Greg J. and Nilson, Laura A.}, year={2010}, month={Aug}, pages={2509–2519} }