851
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Lapraz F, Rawlinson KA, Girstmair J, Tomiczek B, Berger J, Jékely G, Telford MJ, Egger B. Put a tiger in your tank: the polyclad flatworm Maritigrella crozieri as a proposed model for evo-devo. EvoDevo 2013; 4:29. [PMID: 24107307 PMCID: PMC4124852 DOI: 10.1186/2041-9139-4-29] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 08/14/2013] [Indexed: 12/02/2022] Open
Abstract
Polyclad flatworms are an early branching clade within the rhabditophoran Platyhelminthes. They provide an interesting system with which to explore the evolution of development within Platyhelminthes and amongst Spiralia (Lophotrochozoa). Unlike most other flatworms, polyclads undergo spiral cleavage (similar to that seen in some other spiralian taxa), they are the only free-living flatworms where development via a larval stage occurs, and they are the only flatworms in which embryos can be reared outside of their protective egg case, enabling embryonic manipulations. Past work has focused on comparing early cleavage patterns and larval anatomy between polyclads and other spiralians. We have selected Maritigrella crozieri, the tiger flatworm, as a suitable polyclad species for developmental studies, because it is abundant and large in size compared to other species. These characteristics have facilitated the generation of a transcriptome from embryonic and larval material and are enabling us to develop methods for gene expression analysis and immunofluorescence techniques. Here we give an overview of M. crozieri and its development, we highlight the advantages and current limitations of this animal as a potential evo-devo model and discuss current lines of research.
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Affiliation(s)
- François Lapraz
- Department of Genetics, Evolution and Environment, University College London, London, UK.
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852
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BMP-mediated specification of the erythroid lineage suppresses endothelial development in blood island precursors. Blood 2013; 122:3929-39. [PMID: 24100450 DOI: 10.1182/blood-2013-03-490045] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The developmental relationship between the blood and endothelial cell (EC) lineages remains unclear. In the extra-embryonic blood islands of birds and mammals, ECs and blood cells are closely intermixed, and blood island precursor cells in the primitive streak express many of the same molecular markers, leading to the suggestion that both lineages arise from a common precursor, called the hemangioblast. Cells within the blood island of Xenopus also coexpress predifferentiation markers of the blood and EC lineages. However, using multiple assays, we find that precursor cells in the Xenopus blood island do not normally differentiate into ECs, suggesting that classic hemangioblasts are rare or nonexistent in Xenopus. What prevents these precursor cells from developing into mature ECs? We have found that bone morphogenetic protein (BMP) signaling is essential for erythroid differentiation, and in the absence of BMP signaling, precursor cells adopt an EC fate. Furthermore, inhibition of the erythroid transcription pathway leads to endothelial differentiation. Our results indicate that bipotential endothelial/erythroid precursor cells do indeed exist in the Xenopus blood island, but BMP signaling normally acts to constrain EC fate. More generally, these results provide evidence that commitment to the erythroid lineage limits development of bipotential precursors toward an endothelial fate.
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853
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Azuma Y, Onami S. Evaluation of the effectiveness of simple nuclei-segmentation methods on Caenorhabditis elegans embryogenesis images. BMC Bioinformatics 2013; 14:295. [PMID: 24090283 PMCID: PMC4077036 DOI: 10.1186/1471-2105-14-295] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Accepted: 07/15/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND For the analysis of spatio-temporal dynamics, various automated processing methods have been developed for nuclei segmentation. These methods tend to be complex for segmentation of images with crowded nuclei, preventing the simple reapplication of the methods to other problems. Thus, it is useful to evaluate the ability of simple methods to segment images with various degrees of crowded nuclei. RESULTS Here, we selected six simple methods from various watershed based and local maxima detection based methods that are frequently used for nuclei segmentation, and evaluated their segmentation accuracy for each developmental stage of the Caenorhabditis elegans. We included a 4D noise filter, in addition to 2D and 3D noise filters, as a pre-processing step to evaluate the potential of simple methods as widely as possible. By applying the methods to image data between the 50- to 500-cell developmental stages at 50-cell intervals, the error rate for nuclei detection could be reduced to ≤ 2.1% at every stage until the 350-cell stage. The fractions of total errors throughout the stages could be reduced to ≤ 2.4%. The error rates improved at most of the stages and the total errors improved when a 4D noise filter was used. The methods with the least errors were two watershed-based methods with 4D noise filters. For all the other methods, the error rate and the fraction of errors could be reduced to ≤ 4.2% and ≤ 4.1%, respectively. The minimum error rate for each stage between the 400- to 500-cell stages ranged from 6.0% to 8.4%. However, similarities between the computational and manual segmentations measured by volume overlap and Hausdorff distance were not good. The methods were also applied to Drosophila and zebrafish embryos and found to be effective. CONCLUSIONS The simple segmentation methods were found to be useful for detecting nuclei until the 350-cell stage, but not very useful after the 400-cell stage. The incorporation of a 4D noise filter to the simple methods could improve their performances. Error types and the temporal biases of errors were dependent on the methods used. Combining multiple simple methods could also give good segmentations.
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Affiliation(s)
- Yusuke Azuma
- Laboratory for Developmental Dynamics, RIKEN Quantitative Biology Center, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan.
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854
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van der Vaart B, van Riel W, Doodhi H, Kevenaar J, Katrukha E, Gumy L, Bouchet B, Grigoriev I, Spangler S, Yu K, Wulf P, Wu J, Lansbergen G, van Battum E, Pasterkamp R, Mimori-Kiyosue Y, Demmers J, Olieric N, Maly I, Hoogenraad C, Akhmanova A. CFEOM1-Associated Kinesin KIF21A Is a Cortical Microtubule Growth Inhibitor. Dev Cell 2013; 27:145-160. [DOI: 10.1016/j.devcel.2013.09.010] [Citation(s) in RCA: 134] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Revised: 05/21/2013] [Accepted: 09/12/2013] [Indexed: 12/20/2022]
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855
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Abstract
Progression of meiosis has been traditionally reconstructed from microscopic images collected from fixed cells. However, studies conducted in a number of species, including plants, indicate that this approach has clear shortcomings in accurately portraying the dynamic nature of meiotic processes. Here, we describe two methods to study chromosome dynamics in live meiocytes in maize, a protocol to observe chromosomes during meiotic prophase I and a technique to monitor chromosome segregation in anaphase I and anaphase II. The first method relies on culturing intact maize anthers and observing meiocytes embedded in the anthers with multiphoton excitation (MPE) microscopy. This approach circumvents difficulties in culturing isolated prophase I meiocytes in plants. The second technique uses culturing isolated meiocytes, which is possible with anaphase cells. Both methods can be fairly easily adapted for use in other plant species. We also detail the kinds of time-lapse movies that can be captured and analyzed using this technique, and describe software that can be utilized for analysis of movies chromosome dynamic in live meiocytes.
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856
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Benton MA, Akam M, Pavlopoulos A. Cell and tissue dynamics during Tribolium embryogenesis revealed by versatile fluorescence labeling approaches. Development 2013; 140:3210-20. [PMID: 23861059 PMCID: PMC3930475 DOI: 10.1242/dev.096271] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Studies on new arthropod models such as the beetle Tribolium castaneum are shifting our knowledge of embryonic patterning and morphogenesis beyond the Drosophila paradigm. In contrast to Drosophila, Tribolium embryos exhibit the short-germ type of development and become enveloped by extensive extra-embryonic membranes, the amnion and serosa. The genetic basis of these processes has been the focus of active research. Here, we complement genetic approaches with live fluorescence imaging of Tribolium embryos to make the link between gene function and morphogenetic cell behaviors during blastoderm formation and differentiation, germband condensation and elongation, and extra-embryonic development. We first show that transient labeling methods result in strong, homogeneous and persistent expression of fluorescent markers in Tribolium embryos, labeling the chromatin, membrane, cytoskeleton or combinations thereof. We then use co-injection of fluorescent markers with dsRNA for live imaging of embryos with disrupted caudal gene function caused by RNA interference. Using these approaches, we describe and compare cell and tissue dynamics in Tribolium embryos with wild-type and altered fate maps. We find that Tribolium germband condensation is effected by cell contraction and intercalation, with the latter being dependent on the anterior-posterior patterning system. We propose that germband condensation drives initiation of amnion folding, whereas expansion of the amniotic fold and closure of the amniotic cavity are likely driven by contraction of an actomyosin cable at the boundary between the amnion and serosa. Our methodology provides a comprehensive framework for testing quantitative models of patterning, growth and morphogenetic mechanisms in Tribolium and other arthropod species.
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Affiliation(s)
- Matthew A Benton
- Laboratory for Development and Evolution, Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK.
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857
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Schoborg T, Rickels R, Barrios J, Labrador M. Chromatin insulator bodies are nuclear structures that form in response to osmotic stress and cell death. ACTA ACUST UNITED AC 2013; 202:261-76. [PMID: 23878275 PMCID: PMC3718971 DOI: 10.1083/jcb.201304181] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Insulator bodies are novel nuclear stress foci that can be used as a proxy to monitor the chromatin-bound state of insulator proteins. Chromatin insulators assist in the formation of higher-order chromatin structures by mediating long-range contacts between distant genomic sites. It has been suggested that insulators accomplish this task by forming dense nuclear foci termed insulator bodies that result from the coalescence of multiple protein-bound insulators. However, these structures remain poorly understood, particularly the mechanisms triggering body formation and their role in nuclear function. In this paper, we show that insulator proteins undergo a dramatic and dynamic spatial reorganization into insulator bodies during osmostress and cell death in a high osmolarity glycerol–p38 mitogen-activated protein kinase–independent manner, leading to a large reduction in DNA-bound insulator proteins that rapidly repopulate chromatin as the bodies disassemble upon return to isotonicity. These bodies occupy distinct nuclear territories and contain a defined structural arrangement of insulator proteins. Our findings suggest insulator bodies are novel nuclear stress foci that can be used as a proxy to monitor the chromatin-bound state of insulator proteins and provide new insights into the effects of osmostress on nuclear and genome organization.
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Affiliation(s)
- Todd Schoborg
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
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858
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Rizzi B, Peyrieras N. Towards 3D in silico modeling of the sea urchin embryonic development. J Chem Biol 2013; 7:17-28. [PMID: 24386014 PMCID: PMC3877407 DOI: 10.1007/s12154-013-0101-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Accepted: 07/22/2013] [Indexed: 11/29/2022] Open
Abstract
Embryogenesis is a dynamic process with an intrinsic variability whose understanding requires the integration of molecular, genetic, and cellular dynamics. Biological circuits function over time at the level of single cells and require a precise analysis of the topology, temporality, and probability of events. Integrative developmental biology is currently looking for the appropriate strategies to capture the intrinsic properties of biological systems. The "-omic" approaches require disruption of the function of the biological circuit; they provide static information, with low temporal resolution and usually with population averaging that masks fast or variable features at the cellular scale and in a single individual. This data should be correlated with cell behavior as cells are the integrators of biological activity. Cellular dynamics are captured by the in vivo microscopy observation of live organisms. This can be used to reconstruct the 3D + time cell lineage tree to serve as the basis for modeling the organism's multiscale dynamics. We discuss here the progress that has been made in this direction, starting with the reconstruction over time of three-dimensional digital embryos from in toto time-lapse imaging. Digital specimens provide the means for a quantitative description of the development of model organisms that can be stored, shared, and compared. They open the way to in silico experimentation and to a more theoretical approach to biological processes. We show, with some unpublished results, how the proposed methodology can be applied to sea urchin species that have been model organisms in the field of classical embryology and modern developmental biology for over a century.
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Affiliation(s)
- Barbara Rizzi
- CNRS-MDAM, UPR 3294 and BioEmergences-IBiSA, Institut de Neurobiologie Alfred Fessard, CNRS, Gif-sur-Yvette, France
- Institut des Systèmes Complexes, 57-59 rue Lhomond, Paris, France
| | - Nadine Peyrieras
- CNRS-MDAM, UPR 3294 and BioEmergences-IBiSA, Institut de Neurobiologie Alfred Fessard, CNRS, Gif-sur-Yvette, France
- Institut des Systèmes Complexes, 57-59 rue Lhomond, Paris, France
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859
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Panfilio KA, Oberhofer G, Roth S. High plasticity in epithelial morphogenesis during insect dorsal closure. Biol Open 2013; 2:1108-18. [PMID: 24244847 PMCID: PMC3828757 DOI: 10.1242/bio.20136072] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Accepted: 08/05/2013] [Indexed: 01/11/2023] Open
Abstract
Insect embryos complete the outer form of the body via dorsal closure (DC) of the epidermal flanks, replacing the transient extraembryonic (EE) tissue. Cell shape changes and morphogenetic behavior are well characterized for DC in Drosophila, but these data represent a single species with a secondarily reduced EE component (the amnioserosa) that is not representative across the insects. Here, we examine DC in the red flour beetle, Tribolium castaneum, providing the first detailed, functional analysis of DC in an insect with complete EE tissues (distinct amnion and serosa). Surprisingly, we find that differences between Drosophila and Tribolium DC are not restricted to the EE tissue, but also encompass the dorsal epidermis, which differs in cellular architecture and method of final closure (zippering). We then experimentally manipulated EE tissue complement via RNAi for Tc-zen1, allowing us to eliminate the serosa and still examine viable DC in a system with a single EE tissue (the amnion). We find that the EE domain is particularly plastic in morphogenetic behavior and tissue structure. In contrast, embryonic features and overall kinetics are robust to Tc-zen1(RNAi) manipulation in Tribolium and conserved with a more distantly related insect, but remain substantially different from Drosophila. Although correct DC is essential, plasticity and regulative, compensatory capacity have permitted DC to evolve within the insects. Thus, DC does not represent a strong developmental constraint on the nature of EE development, a property that may have contributed to the reduction of the EE component in the fly lineage.
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Affiliation(s)
- Kristen A. Panfilio
- Institute for Developmental Biology, University of Cologne, Zülpicher Strasse 47b, 50674 Cologne, Germany
| | - Georg Oberhofer
- J. F. Blumenbach Institute of Zoology and Anthropology, Department of Developmental Biology, Georg-August-University Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
| | - Siegfried Roth
- Institute for Developmental Biology, University of Cologne, Zülpicher Strasse 47b, 50674 Cologne, Germany
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860
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Mikut R, Dickmeis T, Driever W, Geurts P, Hamprecht FA, Kausler BX, Ledesma-Carbayo MJ, Marée R, Mikula K, Pantazis P, Ronneberger O, Santos A, Stotzka R, Strähle U, Peyriéras N. Automated processing of zebrafish imaging data: a survey. Zebrafish 2013; 10:401-21. [PMID: 23758125 PMCID: PMC3760023 DOI: 10.1089/zeb.2013.0886] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Due to the relative transparency of its embryos and larvae, the zebrafish is an ideal model organism for bioimaging approaches in vertebrates. Novel microscope technologies allow the imaging of developmental processes in unprecedented detail, and they enable the use of complex image-based read-outs for high-throughput/high-content screening. Such applications can easily generate Terabytes of image data, the handling and analysis of which becomes a major bottleneck in extracting the targeted information. Here, we describe the current state of the art in computational image analysis in the zebrafish system. We discuss the challenges encountered when handling high-content image data, especially with regard to data quality, annotation, and storage. We survey methods for preprocessing image data for further analysis, and describe selected examples of automated image analysis, including the tracking of cells during embryogenesis, heartbeat detection, identification of dead embryos, recognition of tissues and anatomical landmarks, and quantification of behavioral patterns of adult fish. We review recent examples for applications using such methods, such as the comprehensive analysis of cell lineages during early development, the generation of a three-dimensional brain atlas of zebrafish larvae, and high-throughput drug screens based on movement patterns. Finally, we identify future challenges for the zebrafish image analysis community, notably those concerning the compatibility of algorithms and data formats for the assembly of modular analysis pipelines.
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Affiliation(s)
- Ralf Mikut
- Karlsruhe Institute of Technology, Karlsruhe, Germany.
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861
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Henry KM, Pase L, Ramos-Lopez CF, Lieschke GJ, Renshaw SA, Reyes-Aldasoro CC. PhagoSight: an open-source MATLAB® package for the analysis of fluorescent neutrophil and macrophage migration in a zebrafish model. PLoS One 2013; 8:e72636. [PMID: 24023630 PMCID: PMC3758287 DOI: 10.1371/journal.pone.0072636] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 07/11/2013] [Indexed: 11/19/2022] Open
Abstract
Neutrophil migration in zebrafish larvae is increasingly used as a model to study the response of these leukocytes to different determinants of the cellular inflammatory response. However, it remains challenging to extract comprehensive information describing the behaviour of neutrophils from the multi-dimensional data sets acquired with widefield or confocal microscopes. Here, we describe PhagoSight, an open-source software package for the segmentation, tracking and visualisation of migrating phagocytes in three dimensions. The algorithms in PhagoSight extract a large number of measurements that summarise the behaviour of neutrophils, but that could potentially be applied to any moving fluorescent cells. To derive a useful panel of variables quantifying aspects of neutrophil migratory behaviour, and to demonstrate the utility of PhagoSight, we evaluated changes in the volume of migrating neutrophils. Cell volume increased as neutrophils migrated towards the wound region of injured zebrafish. PhagoSight is openly available as MATLAB® m-files under the GNU General Public License. Synthetic data sets and a comprehensive user manual are available from http://www.phagosight.org.
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Affiliation(s)
- Katherine M. Henry
- MRC Centre for Developmental and Biomedical Genetics, University of Sheffield, Sheffield, United Kingdom
| | - Luke Pase
- Cancer and Haematology Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Institute of Toxicology and Genetics, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany
| | | | - Graham J. Lieschke
- Cancer and Haematology Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Australia
- Australian Regenerative Medicine Institute, Monash University, Clayton, Australia
| | - Stephen A. Renshaw
- MRC Centre for Developmental and Biomedical Genetics, University of Sheffield, Sheffield, United Kingdom
| | - Constantino Carlos Reyes-Aldasoro
- Biomedical Engineering Research Group, University of Sussex, Falmer, United Kingdom
- Information Engineering and Medical Imaging Group, City University London, London, United Kingdom
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862
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αV-integrins are required for mechanotransduction in MDCK epithelial cells. PLoS One 2013; 8:e71485. [PMID: 23977051 PMCID: PMC3747215 DOI: 10.1371/journal.pone.0071485] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Accepted: 06/29/2013] [Indexed: 01/12/2023] Open
Abstract
The properties of epithelial cells within tissues are regulated by their immediate microenvironment, which consists of neighboring cells and the extracellular matrix (ECM). Integrin heterodimers orchestrate dynamic assembly and disassembly of cell-ECM connections and thereby convey biochemical and mechanical information from the ECM into cells. However, the specific contributions and functional hierarchy between different integrin heterodimers in the regulation of focal adhesion dynamics in epithelial cells are incompletely understood. Here, we have studied the functions of RGD-binding αV-integrins in a Madin Darby Canine Kidney (MDCK) cell model and found that αV-integrins regulate the maturation of focal adhesions (FAs) and cell spreading. αV-integrin-deficient MDCK cells bound collagen I (Col I) substrate via α2β1-integrins but failed to efficiently recruit FA components such as talin, focal adhesion kinase (FAK), vinculin and integrin-linked kinase (ILK). The apparent inability to mature α2β1-integrin-mediated FAs and link them to cellular actin cytoskeleton led to disrupted mechanotransduction in αV-integrin deficient cells seeded onto Col I substrate.
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863
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Glycine receptor α2 subunit activation promotes cortical interneuron migration. Cell Rep 2013; 4:738-50. [PMID: 23954789 PMCID: PMC3763372 DOI: 10.1016/j.celrep.2013.07.016] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Revised: 06/17/2013] [Accepted: 07/12/2013] [Indexed: 12/11/2022] Open
Abstract
Glycine receptors (GlyRs) are detected in the developing CNS before synaptogenesis, but their function remains elusive. This study demonstrates that functional GlyRs are expressed by embryonic cortical interneurons in vivo. Furthermore, genetic disruption of these receptors leads to interneuron migration defects. We discovered that extrasynaptic activation of GlyRs containing the α2 subunit in cortical interneurons by endogenous glycine activates voltage-gated calcium channels and promotes calcium influx, which further modulates actomyosin contractility to fine-tune nuclear translocation during migration. Taken together, our data highlight the molecular events triggered by GlyR α2 activation that control cortical tangential migration during embryogenesis.
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864
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Francis R, Lo C. Ex vivo method for high resolution imaging of cilia motility in rodent airway epithelia. J Vis Exp 2013. [PMID: 23963287 DOI: 10.3791/50343] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
An ex vivo technique for imaging mouse airway epithelia for quantitative analysis of motile cilia function important for insight into mucociliary clearance function has been established. Freshly harvested mouse trachea is cut longitudinally through the trachealis muscle and mounted in a shallow walled chamber on a glass-bottomed dish. The trachea sample is positioned along its long axis to take advantage of the trachealis muscle to curl longitudinally. This allows imaging of ciliary motion in the profile view along the entire tracheal length. Videos at 200 frames/sec are obtained using differential interference contrast microscopy and a high speed digital camera to allow quantitative analysis of cilia beat frequency and ciliary waveform. With the addition of fluorescent beads during imaging, cilia generated fluid flow also can be determined. The protocol time spans approximately 30 min, with 5 min for chamber preparation, 5-10 min for sample mounting, and 10-15 min for videomicroscopy.
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Affiliation(s)
- Richard Francis
- Department of Developmental Biology, University of Pittsburgh, USA
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865
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866
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Schäfer S, Dekiff M, Plate U, Szuwart T, Denz C, Dirksen D. Quantitative analysis of dynamic behavior of osteoblasts during in vitro formation of micro-mass cell cultures. JOURNAL OF BIOPHOTONICS 2013; 6:637-644. [PMID: 23125153 DOI: 10.1002/jbio.201200169] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Revised: 09/21/2012] [Accepted: 09/22/2012] [Indexed: 06/01/2023]
Abstract
Improvements in bone tissue engineering require an understanding of cellular and tissue level behavior of osteoblast-like cells. Experiments indicate that in the absence of an anchoring material, intercellular adhesion may be based on signals that promote cell activity resulting in the formation of a spheroid cell-matrix. The aim of the present study is to investigate the formation of scaffold-free three-dimensional micro-mass cell spheroids in vitro, and to characterize quantitatively the cell movement. A new correlation based automated tracking method is evaluated in order to optimize the processing parameters and to identify statistical parameters that characterize the cell behavior. Results suggest that the temporal development of the mean distance of the cells to the center of gravity may be described by an exponential function, thus providing a characteristic time constant as a quantitative measure of cell dynamics. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).
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Affiliation(s)
- Susanne Schäfer
- University of Münster, Dept. of Maxillofacial Surgery, Germany
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867
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Karpel-Massler G, Westhoff MA, Zhou S, Nonnenmacher L, Dwucet A, Kast RE, Bachem MG, Wirtz CR, Debatin KM, Halatsch ME. Combined Inhibition of HER1/EGFR and RAC1 Results in a Synergistic Antiproliferative Effect on Established and Primary Cultured Human Glioblastoma Cells. Mol Cancer Ther 2013; 12:1783-95. [DOI: 10.1158/1535-7163.mct-13-0052] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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868
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Single-molecule reconstitution of mRNA transport by a class V myosin. Nat Struct Mol Biol 2013; 20:952-7. [PMID: 23812374 PMCID: PMC3735863 DOI: 10.1038/nsmb.2614] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Accepted: 05/14/2013] [Indexed: 12/27/2022]
Abstract
Molecular motors are instrumental in mRNA localization, which provides spatial and temporal control of protein expression and function. To obtain mechanistic insight into how a class V myosin transports mRNA, we performed single-molecule in vitro assays on messenger ribonucleoprotein (mRNP) complexes reconstituted from purified proteins and a localizing mRNA found in budding yeast. mRNA is required to form a stable, processive transport complex on actin--an elegant mechanism to ensure that only cargo-bound motors are motile. Increasing the number of localizing elements ('zip codes') on the mRNA, or configuring the track to resemble actin cables, enhanced run length and event frequency. In multi-zip-code mRNPs, motor separation distance varied during a run, thus showing the dynamic nature of the transport complex. Building the complexity of single-molecule in vitro assays is necessary to understand how these complexes function within cells.
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869
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Trivedi DV, Muretta JM, Swenson AM, Thomas DD, Yengo CM. Magnesium impacts myosin V motor activity by altering key conformational changes in the mechanochemical cycle. Biochemistry 2013; 52:4710-22. [PMID: 23725637 DOI: 10.1021/bi4004364] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We investigated how magnesium (Mg) impacts key conformational changes during the ADP binding/release steps in myosin V and how these alterations impact the actomyosin mechanochemical cycle. The conformation of the nucleotide binding pocket was examined with our established FRET system in which myosin V labeled with FlAsH in the upper 50 kDa domain participates in energy transfer with mant labeled nucleotides. We examined the maximum actin-activated ATPase activity of MV FlAsH at a range of free Mg concentrations (0.1-9 mM) and found that the highest activity occurs at low Mg (0.1-0.3 mM), while there is a 50-60% reduction in activity at high Mg (3-9 mM). The motor activity examined with the in vitro motility assay followed a similar Mg-dependence, and the trend was similar with dimeric myosin V. Transient kinetic FRET studies of mantdADP binding/release from actomyosin V FlAsH demonstrate that the transition between the weak and strong actomyosin.ADP states is coupled to movement of the upper 50 kDa domain and is dependent on Mg with the strong state stabilized by Mg. We find that the kinetics of the upper 50 kDa conformational change monitored by FRET correlates well with the ATPase and motility results over a wide range of Mg concentrations. Our results suggest the conformation of the upper 50 kDa domain is highly dynamic in the Mg free actomyosin.ADP state, which is in agreement with ADP binding being entropy driven in the absence of Mg. Overall, our results demonstrate that Mg is a key factor in coupling the nucleotide- and actin-binding regions. In addition, Mg concentrations in the physiological range can alter the structural transition that limits ADP dissociation from actomyosin V, which explains the impact of Mg on actin-activated ATPase activity and in vitro motility.
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Affiliation(s)
- Darshan V Trivedi
- Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University , Hershey, Pennsylvania 17033, United States
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870
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Granstedt AE, Brunton BW, Enquist LW. Imaging the transport dynamics of single alphaherpesvirus particles in intact peripheral nervous system explants from infected mice. mBio 2013; 4:e00358-13. [PMID: 23736287 PMCID: PMC3685211 DOI: 10.1128/mbio.00358-13] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 05/14/2013] [Indexed: 01/13/2023] Open
Abstract
ABSTRACT Alphaherpesvirus particles travel long distances in the axons of neurons using host microtubule molecular motors. The transport dynamics of individual virions in neurons have been assessed in cultured neurons, but imaging studies of single particles in tissue from infected mice have not been reported. We developed a protocol to image explanted, infected peripheral nervous system (PNS) ganglia and associated innervated tissue from mice infected with pseudorabies virus (PRV). This ex vivo preparation allowed us to visualize and track individual virions over time as they moved from the salivary gland into submandibular ganglion neurons of the PNS. We imaged and tracked hundreds of virions from multiple mice at different time points. We quantitated the transport velocity, particle stalling, duty cycle, and directionality at various times after infection. Using a PRV recombinant that expressed monomeric red fluorescent protein (mRFP)-VP26 (red capsid) and green fluorescent protein (GFP)-Us9 (green membrane protein), we corroborated that anterograde transport in axons occurs after capsids are enveloped. We addressed the question of whether replication occurs initially in the salivary gland at the site of inoculation or subsequently in the neurons of peripheral innervating ganglia. Our data indicate that significant amplification of infection occurs in the peripheral ganglia after transport from the site of infection and that these newly made particles are transported back to the salivary gland. It is likely that this reseeding of the infected gland contributes to massive invasion of the innervating PNS ganglia. We suggest that this "round-trip" infection process contributes to the characteristic peripheral neuropathy of PRV infection. IMPORTANCE Much of our understanding of molecular mechanisms of alphaherpesvirus infection and spread in neurons comes from studying cultured primary neurons. These techniques enabled significant advances in our understanding of the viral and neuronal components needed for efficient replication and directional spread between cells. However, in vitro systems cannot recapitulate the environment of innervated tissue in vivo with associated defensive properties, such as innate immunity. Therefore, in this report, we describe a system to image the progression of infection by single virus particles in tissue harvested from infected animals. We explanted intact innervated tissue from infected mice and imaged fluorescent virus particles in infected axons of the specific ganglionic neurons. Our measurements of virion transport dynamics are consistent with published in vitro results. Importantly, this system enabled us to address a fundamental biological question about the amplification of a herpesvirus infection in a peripheral nervous system circuit.
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Affiliation(s)
- Andrea E Granstedt
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
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871
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Kurz V, Nelson EM, Shim J, Timp G. Direct visualization of single-molecule translocations through synthetic nanopores comparable in size to a molecule. ACS NANO 2013; 7:4057-69. [PMID: 23607372 DOI: 10.1021/nn400182s] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A nanopore is the ultimate analytical tool. It can be used to detect DNA, RNA, oligonucleotides, and proteins with submolecular sensitivity. This extreme sensitivity is derived from the electric signal associated with the occlusion that develops during the translocation of the analyte across a membrane through a pore immersed in electrolyte. A larger occluded volume results in an improvement in the signal-to-noise ratio, and so the pore geometry should be made comparable to the size of the target molecule. However, the pore geometry also affects the electric field, the charge density, the electro-osmotic flow, the capture volume, and the response time. Seeking an optimal pore geometry, we tracked the molecular motion in three dimensions with high resolution, visualizing with confocal microscopy the fluorescence associated with DNA translocating through nanopores with diameters comparable to the double helix, while simultaneously measuring the pore current. Measurements reveal single molecules translocating across the membrane through the pore commensurate with the observation of a current blockade. To explain the motion of the molecule near the pore, finite-element simulations were employed that account for diffusion, electrophoresis, and the electro-osmotic flow. According to this analysis, detection using a nanopore comparable in diameter to the double helix represents a compromise between sensitivity, capture volume, the minimum detectable concentration, and response time.
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Affiliation(s)
- Volker Kurz
- Departments of Electrical Engineering and Biological Science, University of Notre Dame, Notre Dame, Indiana 46556, United States
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872
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White EA, Raghuraman H, Perozo E, Glotzer M. Binding of the CYK-4 subunit of the centralspindlin complex induces a large scale conformational change in the kinesin subunit. J Biol Chem 2013; 288:19785-95. [PMID: 23720745 DOI: 10.1074/jbc.m113.463695] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Centralspindlin is a critical regulator of cytokinesis in animal cells. It is a tetramer consisting of ZEN-4/MKLP1, a kinesin-6 motor, and CYK-4/MgcRacGAP, a Rho GTPase-activating protein. At anaphase, centralspindlin localizes to a narrow region of antiparallel microtubule overlap and initiates central spindle assembly. Central spindle assembly requires complex formation between ZEN-4 and CYK-4. However, the structural consequences of CYK-4 binding to ZEN-4 are unclear as are the mechanisms of microtubule bundling. Here we investigate whether CYK-4 binding induces a conformational change in ZEN-4. Characterization of the structure and conformational dynamics of the minimal interacting regions between ZEN-4 and CYK-4 by continuous wave EPR and double electron-electron resonance (DEER) spectroscopy reveals that CYK-4 binding dramatically stabilizes the relative positions of the neck linker regions of ZEN-4. Additionally, our data indicate that each neck linker is similarly structured in the bound and unbound states. CYK-4 binding decreases the rate of ZEN-4-mediated microtubule gliding. These results constrain models for the molecular organization of centralspindlin.
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Affiliation(s)
- Erin A White
- Departments of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois 60637, USA
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873
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Adikes RC, Unrath WC, Yengo CM, Quintero OA. Biochemical and bioinformatic analysis of the myosin-XIX motor domain. Cytoskeleton (Hoboken) 2013; 70:281-95. [PMID: 23568824 DOI: 10.1002/cm.21110] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Revised: 03/25/2013] [Accepted: 04/02/2013] [Indexed: 12/14/2022]
Abstract
Mitochondrial dynamics are dependent on both the microtubule and actin cytoskeletal systems. Evidence for the involvement of myosin motors has been described in many systems, and until recently a candidate mitochondrial myosin transport motor had not been described in vertebrates. Myosin-XIX (MYO19) was predicted to represent a novel class of myosin and had previously been shown to bind to mitochondria and increase mitochondrial network dynamics when ectopically expressed. Our analyses comparing ∼40 MYO19 orthologs to ∼2000 other myosin motor domain sequences identified instances of homology well-conserved within class XIX myosins that were not found in other myosin classes, suggesting MYO19-specific mechanochemistry. Steady-state biochemical analyses of the MYO19 motor domain indicate that Homo sapiens MYO19 is a functional motor. Insect cell-expressed constructs bound calmodulin as a light chain at the predicted stoichiometry and displayed actin-activated ATPase activity. MYO19 constructs demonstrated high actin affinity in the presence of ATP in actin-co-sedimentation assays, and translocated actin filaments in gliding assays. Expression of GFP-MYO19 containing a mutation impairing ATPase activity did not enhance mitochondrial network dynamics, as occurs with wild-type MYO19, indicating that myosin motor activity is required for mitochondrial motility. The measured biochemical properties of MYO19 suggest it is a high-duty ratio motor that could serve to transport mitochondria or anchor mitochondria, depending upon the cellular microenvironment.
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Affiliation(s)
- Rebecca C Adikes
- Program in Biochemistry, Mount Holyoke College, South Hadley, Massachusetts, USA
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874
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Amat F, Keller PJ. Towards comprehensive cell lineage reconstructions in complex organisms using light-sheet microscopy. Dev Growth Differ 2013; 55:563-78. [PMID: 23621671 DOI: 10.1111/dgd.12063] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 03/05/2013] [Accepted: 03/21/2013] [Indexed: 01/23/2023]
Abstract
Understanding the development of complex multicellular organisms as a function of the underlying cell behavior is one of the most fundamental goals of developmental biology. The ability to quantitatively follow cell dynamics in entire developing embryos is an indispensable step towards such a system-level understanding. In recent years, light-sheet fluorescence microscopy has emerged as a particularly promising strategy for recording the in vivo data required to realize this goal. Using light-sheet fluorescence microscopy, entire complex organisms can be rapidly imaged in three dimensions at sub-cellular resolution, achieving high temporal sampling and excellent signal-to-noise ratio without damaging the living specimen or bleaching fluorescent markers. The resulting datasets allow following individual cells in vertebrate and higher invertebrate embryos over up to several days of development. However, the complexity and size of these multi-terabyte recordings typically preclude comprehensive manual analyses. Thus, new computational approaches are required to automatically segment cell morphologies, accurately track cell identities and systematically analyze cell behavior throughout embryonic development. We review current efforts in light-sheet microscopy and bioimage informatics towards this goal, and argue that comprehensive cell lineage reconstructions are finally within reach for many key model organisms, including fruit fly, zebrafish and mouse.
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Affiliation(s)
- Fernando Amat
- Janelia Farm Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA.
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875
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Schmitter D, Wachowicz P, Sage D, Chasapi A, Xenarios I, Simanis, Unser M. A 2D/3D image analysis system to track fluorescently labeled structures in rod-shaped cells: application to measure spindle pole asymmetry during mitosis. Cell Div 2013; 8:6. [PMID: 23622681 PMCID: PMC3693874 DOI: 10.1186/1747-1028-8-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Accepted: 04/05/2013] [Indexed: 02/04/2023] Open
Abstract
Background The yeast Schizosaccharomyces pombe is frequently used as a model for studying the cell cycle. The cells are rod-shaped and divide by medial fission. The process of cell division, or cytokinesis, is controlled by a network of signaling proteins called the Septation Initiation Network (SIN); SIN proteins associate with the SPBs during nuclear division (mitosis). Some SIN proteins associate with both SPBs early in mitosis, and then display strongly asymmetric signal intensity at the SPBs in late mitosis, just before cytokinesis. This asymmetry is thought to be important for correct regulation of SIN signaling, and coordination of cytokinesis and mitosis. In order to study the dynamics of organelles or large protein complexes such as the spindle pole body (SPB), which have been labeled with a fluorescent protein tag in living cells, a number of the image analysis problems must be solved; the cell outline must be detected automatically, and the position and signal intensity associated with the structures of interest within the cell must be determined. Results We present a new 2D and 3D image analysis system that permits versatile and robust analysis of motile, fluorescently labeled structures in rod-shaped cells. We have designed an image analysis system that we have implemented as a user-friendly software package allowing the fast and robust image-analysis of large numbers of rod-shaped cells. We have developed new robust algorithms, which we combined with existing methodologies to facilitate fast and accurate analysis. Our software permits the detection and segmentation of rod-shaped cells in either static or dynamic (i.e. time lapse) multi-channel images. It enables tracking of two structures (for example SPBs) in two different image channels. For 2D or 3D static images, the locations of the structures are identified, and then intensity values are extracted together with several quantitative parameters, such as length, width, cell orientation, background fluorescence and the distance between the structures of interest. Furthermore, two kinds of kymographs of the tracked structures can be established, one representing the migration with respect to their relative position, the other representing their individual trajectories inside the cell. This software package, called “RodCellJ”, allowed us to analyze a large number of S. pombe cells to understand the rules that govern SIN protein asymmetry. (Continued on next page) (Continued from previous page) Conclusions “RodCellJ” is freely available to the community as a package of several ImageJ plugins to simultaneously analyze the behavior of a large number of rod-shaped cells in an extensive manner. The integration of different image-processing techniques in a single package, as well as the development of novel algorithms does not only allow to speed up the analysis with respect to the usage of existing tools, but also accounts for higher accuracy. Its utility was demonstrated on both 2D and 3D static and dynamic images to study the septation initiation network of the yeast Schizosaccharomyces pombe. More generally, it can be used in any kind of biological context where fluorescent-protein labeled structures need to be analyzed in rod-shaped cells. Availability RodCellJ is freely available under http://bigwww.epfl.ch/algorithms.html.
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Affiliation(s)
- Daniel Schmitter
- Biomedical Imaging Group, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Paulina Wachowicz
- Cell Cycle Control Laboratory, Swiss Institute for Experimental Cancer Research (ISREC), Ecole Polytechnique Fédérale de Lausanne(EPFL), Lausanne, Switzerland
| | - Daniel Sage
- Biomedical Imaging Group, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Anastasia Chasapi
- Swiss-Prot Group & Vital-IT Group, Swiss Institute of Bioinformatics (SIB) Lausanne, Switzerland
| | - Ioannis Xenarios
- Swiss-Prot Group & Vital-IT Group, Swiss Institute of Bioinformatics (SIB) Lausanne, Switzerland
| | - Simanis
- Cell Cycle Control Laboratory, Swiss Institute for Experimental Cancer Research (ISREC), Ecole Polytechnique Fédérale de Lausanne(EPFL), Lausanne, Switzerland
| | - Michael Unser
- Biomedical Imaging Group, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
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876
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Saphirstein RJ, Gao YZ, Jensen MH, Gallant CM, Vetterkind S, Moore JR, Morgan KG. The focal adhesion: a regulated component of aortic stiffness. PLoS One 2013; 8:e62461. [PMID: 23626821 PMCID: PMC3633884 DOI: 10.1371/journal.pone.0062461] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 03/21/2013] [Indexed: 01/16/2023] Open
Abstract
Increased aortic stiffness is an acknowledged predictor and cause of cardiovascular disease. The sources and mechanisms of vascular stiffness are not well understood, although the extracellular matrix (ECM) has been assumed to be a major component. We tested here the hypothesis that the focal adhesions (FAs) connecting the cortical cytoskeleton of vascular smooth muscle cells (VSMCs) to the matrix in the aortic wall are a component of aortic stiffness and that this component is dynamically regulated. First, we examined a model system in which magnetic tweezers could be used to monitor cellular cortical stiffness, serum-starved A7r5 aortic smooth muscle cells. Lysophosphatidic acid (LPA), an activator of myosin that increases cell contractility, increased cortical stiffness. A small molecule inhibitor of Src-dependent FA recycling, PP2, was found to significantly inhibit LPA-induced increases in cortical stiffness, as well as tension-induced increases in FA size. To directly test the applicability of these results to force and stiffness development at the level of vascular tissue, we monitored mouse aorta ring stiffness with small sinusoidal length oscillations during agonist-induced contraction. The alpha-agonist phenylephrine, which also increases myosin activation and contractility, increased tissue stress and stiffness in a PP2- and FAK inhibitor 14-attenuated manner. Subsequent phosphotyrosine screening and follow-up with phosphosite-specific antibodies confirmed that the effects of PP2 and FAK inhibitor 14 in vascular tissue involve FA proteins, including FAK, CAS, and paxillin. Thus, in the present study we identify, for the first time, the FA of the VSMC, in particular the FAK-Src signaling complex, as a significant subcellular regulator of aortic stiffness and stress.
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Affiliation(s)
- Robert J. Saphirstein
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts, United States of America
- Department of Health Sciences, Boston University, Boston, Massachusetts, United States of America
| | - Yuan Z. Gao
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts, United States of America
- Department of Health Sciences, Boston University, Boston, Massachusetts, United States of America
| | - Mikkel H. Jensen
- Department of Physics, Boston University, Boston, Massachusetts, United States of America
- Department of Physiology and Biophysics, Boston University Medical School, Boston, Massachusetts, United States of America
| | - Cynthia M. Gallant
- Department of Health Sciences, Boston University, Boston, Massachusetts, United States of America
| | - Susanne Vetterkind
- Department of Health Sciences, Boston University, Boston, Massachusetts, United States of America
| | - Jeffrey R. Moore
- Department of Physiology and Biophysics, Boston University Medical School, Boston, Massachusetts, United States of America
| | - Kathleen G. Morgan
- Department of Health Sciences, Boston University, Boston, Massachusetts, United States of America
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877
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Mossadegh-Keller N, Sarrazin S, Kandalla PK, Espinosa L, Stanley ER, Nutt SL, Moore J, Sieweke MH. M-CSF instructs myeloid lineage fate in single haematopoietic stem cells. Nature 2013; 497:239-43. [PMID: 23575636 DOI: 10.1038/nature12026] [Citation(s) in RCA: 270] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 02/20/2013] [Indexed: 02/08/2023]
Abstract
Under stress conditions such as infection or inflammation the body rapidly needs to generate new blood cells that are adapted to the challenge. Haematopoietic cytokines are known to increase output of specific mature cells by affecting survival, expansion and differentiation of lineage-committed progenitors, but it has been debated whether long-term haematopoietic stem cells (HSCs) are susceptible to direct lineage-specifying effects of cytokines. Although genetic changes in transcription factor balance can sensitize HSCs to cytokine instruction, the initiation of HSC commitment is generally thought to be triggered by stochastic fluctuation in cell-intrinsic regulators such as lineage-specific transcription factors, leaving cytokines to ensure survival and proliferation of the progeny cells. Here we show that macrophage colony-stimulating factor (M-CSF, also called CSF1), a myeloid cytokine released during infection and inflammation, can directly induce the myeloid master regulator PU.1 and instruct myeloid cell-fate change in mouse HSCs, independently of selective survival or proliferation. Video imaging and single-cell gene expression analysis revealed that stimulation of highly purified HSCs with M-CSF in culture resulted in activation of the PU.1 promoter and an increased number of PU.1(+) cells with myeloid gene signature and differentiation potential. In vivo, high systemic levels of M-CSF directly stimulated M-CSF-receptor-dependent activation of endogenous PU.1 protein in single HSCs and induced a PU.1-dependent myeloid differentiation preference. Our data demonstrate that lineage-specific cytokines can act directly on HSCs in vitro and in vivo to instruct a change of cell identity. This fundamentally changes the current view of how HSCs respond to environmental challenge and implicates stress-induced cytokines as direct instructors of HSC fate.
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Affiliation(s)
- Noushine Mossadegh-Keller
- Centre d'Immunologie de Marseille-Luminy, Aix-Marseille Université, UM2, Campus de Luminy, Case 906, 13288 Marseille Cedex 09, France
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878
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Rohrschneider MR, Nance J. The union of somatic gonad precursors and primordial germ cells during Caenorhabditis elegans embryogenesis. Dev Biol 2013; 379:139-51. [PMID: 23562590 DOI: 10.1016/j.ydbio.2013.03.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 03/12/2013] [Accepted: 03/26/2013] [Indexed: 11/17/2022]
Abstract
Somatic gonadal niche cells control the survival, differentiation, and proliferation of germline stem cells. The establishment of this niche-stem cell relationship is critical, and yet the precursors to these two cell types are often born at a distance from one another. The simple Caenorhabditis elegans gonadal primordium, which contains two somatic gonad precursors (SGPs) and two primordial germ cells (PGCs), provides an accessible model for determining how stem cell and niche cell precursors first assemble during development. To visualize the morphogenetic events that lead to formation of the gonadal primordium, we generated transgenic strains to label the cell membranes of the SGPs and PGCs and captured time-lapse movies as the gonadal primordium formed. We identify three distinct phases of SGP behavior: posterior migration along the endoderm towards the PGCs, extension of a single long projection around the adjacent PGC, and a dramatic wrapping over the PGC surfaces. We show that the endoderm and PGCs are dispensable for SGP posterior migration and initiation of projections. However, both tissues are required for the final positioning of the SGPs and the morphology of their projections, and PGCs are absolutely required for SGP wrapping behaviors. Finally, we demonstrate that the basement membrane component laminin, which localizes adjacent to the developing gonadal primordium, is required to prevent the SGPs from over-extending past the PGCs. Our findings provide a foundation for understanding the cellular and molecular regulation of the establishment of a niche-stem cell relationship.
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Affiliation(s)
- Monica R Rohrschneider
- Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, New York, NY 10016, USA
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879
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Bignami S, Sponaugle S, Cowen RK. Response to ocean acidification in larvae of a large tropical marine fish, Rachycentron canadum. GLOBAL CHANGE BIOLOGY 2013; 19:996-1006. [PMID: 23504878 DOI: 10.1111/gcb.12133] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Revised: 12/15/2012] [Accepted: 12/19/2012] [Indexed: 05/28/2023]
Abstract
Currently, ocean acidification is occurring at a faster rate than at any time in the last 300 million years, posing an ecological challenge to marine organisms globally. There is a critical need to understand the effects of acidification on the vulnerable larval stages of marine fishes, as there is potential for large ecological and economic impacts on fish populations and the human economies that rely on them. We expand upon the narrow taxonomic scope found in the literature today, which overlooks many life history characteristics of harvested species, by reporting on the larvae of Rachycentron canadum (cobia), a large, highly mobile, pelagic-spawning, widely distributed species with a life history and fishery value contrasting other species studied to date. We raised larval cobia through the first 3 weeks of ontogeny under conditions of predicted future ocean acidification to determine effects on somatic growth, development, otolith formation, swimming ability, and swimming activity. Cobia exhibited resistance to treatment effects on growth, development, swimming ability, and swimming activity at 800 and 2100 μatm pCO2 . However, these scenarios resulted in a significant increase in otolith size (up to 25% larger area) at the lowest pCO2 levels reported to date, as well as the first report of significantly wider daily otolith growth increments. When raised under more extreme scenarios of 3500 and 5400 μatm pCO2 , cobia exhibited significantly reduced size-at-age (up to 25% smaller) and a 2-3 days developmental delay. The robust nature of cobia may be due to the naturally variable environmental conditions this species currently encounters throughout ontogeny in coastal environments, which may lead to an increased acclimatization ability even during long-term exposure to stressors.
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Affiliation(s)
- Sean Bignami
- Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, Miami, FL 33149, USA.
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880
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Deng Q, Sarris M, Bennin DA, Green JM, Herbomel P, Huttenlocher A. Localized bacterial infection induces systemic activation of neutrophils through Cxcr2 signaling in zebrafish. J Leukoc Biol 2013; 93:761-9. [PMID: 23475575 DOI: 10.1189/jlb.1012534] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Neutrophils are the first line of defense against tissue damage and are rapidly mobilized to sites of bacterial infection. However, the signals that regulate neutrophil recruitment are not well defined. Here, using photolabel-enabled fate mapping in zebrafish larvae, we show that localized otic infection with Pseudomonas aeruginosa induces systemic activation and mobilization of neutrophils from the CHT through Cxcr2 signaling. We have cloned the zebrafish Cxcr1 and Cxcr2 receptors and show that Cxcr2 functions as a Cxcl8 receptor in live zebrafish. With the use of morpholino-mediated depletion, we show that infection-induced neutrophil mobilization from the CHT is mediated by Cxcr2 but not Cxcr1. By contrast, Cxcr2 depletion does not affect neutrophil recruitment to the chemoattractant LTB4. Taken together, our findings identify Cxcl8-Cxcr2 signaling as an infection-induced long-range cue that mediates neutrophil motility and mobilization from hematopoietic tissues, positioning Cxcr2 as a critical pathway that mediates infection-induced systemic activation of neutrophils.
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Affiliation(s)
- Qing Deng
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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881
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Wang Y, Ajtai K, Burghardt TP. The Qdot-labeled actin super-resolution motility assay measures low-duty cycle muscle myosin step size. Biochemistry 2013; 52:1611-21. [PMID: 23383646 DOI: 10.1021/bi301702p] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Myosin powers contraction in heart and skeletal muscle and is a leading target for mutations implicated in inheritable muscle diseases. During contraction, myosin transduces ATP free energy into the work of muscle shortening against resisting force. Muscle shortening involves relative sliding of myosin and actin filaments. Skeletal actin filaments were fluorescently labeled with a streptavidin conjugate quantum dot (Qdot) binding biotin-phalloidin on actin. Single Qdots were imaged in time with total internal reflection fluorescence microscopy and then spatially localized to 1-3 nm using a super-resolution algorithm as they translated with actin over a surface coated with skeletal heavy meromyosin (sHMM) or full-length β-cardiac myosin (MYH7). The average Qdot-actin velocity matches measurements with rhodamine-phalloidin-labeled actin. The sHMM Qdot-actin velocity histogram contains low-velocity events corresponding to actin translation in quantized steps of ~5 nm. The MYH7 velocity histogram has quantized steps at 3 and 8 nm in addition to 5 nm and larger compliance compared to that of sHMM depending on the MYH7 surface concentration. Low-duty cycle skeletal and cardiac myosin present challenges for a single-molecule assay because actomyosin dissociates quickly and the freely moving element diffuses away. The in vitro motility assay has modestly more actomyosin interactions, and methylcellulose inhibited diffusion to sustain the complex while preserving a subset of encounters that do not overlap in time on a single actin filament. A single myosin step is isolated in time and space and then characterized using super-resolution. The approach provides a quick, quantitative, and inexpensive step size measurement for low-duty cycle muscle myosin.
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Affiliation(s)
- Yihua Wang
- Department of Biochemistry and Molecular Biology, Mayo Clinic Rochester, Rochester, Minnesota 55905, USA
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882
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Yang G. Bioimage informatics for understanding spatiotemporal dynamics of cellular processes. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2013; 5:367-80. [PMID: 23408597 DOI: 10.1002/wsbm.1214] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The inner environment of the cell is highly dynamic and heterogeneous yet exquisitely organized. Successful completion of cellular processes within this environment depends on the right molecules or molecular complexes to function at the right place at the right time. Understanding spatiotemporal behaviors of cellular processes is therefore essential to understanding their molecular mechanisms at the systems level. These behaviors are usually visualized and recorded using imaging techniques. However, to infer from them systems-level molecular mechanisms, computational analysis and understanding of recorded image data is crucial, not only for acquiring quantitative behavior measurements but also for comprehending complex interactions among the molecules or molecular complexes involved. The technology of computational analysis and understanding of biological images is often referred to simply as bioimage informatics. This article introduces fundamentals of bioimage informatics for understanding spatiotemporal dynamics of cellular processes and reviews recent advances on this topic. Basic bioimage informatics concepts and techniques for characterizing spatiotemporal cell dynamics are introduced first. Studies on specific cellular processes such as cell migration and signal transduction are then used as examples to analyze and summarize recent advances, with the focus on transforming quantitative measurements of spatiotemporal cellular behaviors into knowledge of underlying molecular mechanisms. Despite the advances made, substantial technological challenges remain, especially in representation of spatiotemporal cellular behaviors and inference of systems-level molecular mechanisms. These challenges are briefly discussed. Overall, understanding spatiotemporal cell dynamics will provide critical insights into how specific cellular processes as well as the entire inner cellular environment are dynamically organized and regulated.
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Affiliation(s)
- Ge Yang
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA.
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883
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Sugita S, Matsumoto T. Novel biaxial tensile test for studying aortic failure phenomena at a microscopic level. Biomed Eng Online 2013; 12:3. [PMID: 23305508 PMCID: PMC3560224 DOI: 10.1186/1475-925x-12-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Accepted: 12/26/2012] [Indexed: 11/29/2022] Open
Abstract
Background An aortic aneurysm is a local dilation of the aorta, which tends to expand and often results in a fatal rupture. Although larger aneurysms have a greater risk of rupture, some small aneurysms also rupture. Since the mechanism of aortic rupture is not well understood, clarification of the microstructure influencing the failure to rupture is important. Since aortic tissues are stretched biaxially in vivo, we developed a technique to microscopically observe the failure of an aortic rupture during biaxial stretch. Methods A thinly sliced porcine thoracic aortic specimen was adhered to a circular frame and pushed onto a cylinder with a smaller diameter to stretch the specimen biaxially. To induce failure to rupture at the center, the specimen was thinned at the center of the hole as follows: the specimen was frozen while being compressed with metal plates having holes, which were 3 mm in diameter at their centers; the specimen was then sliced at 50-μm intervals and thawed. Results The ratio of the thickness at the center to the peripheral area was 99.5% for uncompressed specimens. The ratio decreased with an increase in the compression ratio εc and was 47.3% for specimens with εc = 40%. All specimens could be stretched until failure to rupture. The probability for crack initiation within the cylinder was <30% and 100% for specimens with εc <10% and εc >30%, respectively. Among specimens ruptured within the cylinder, 93% of those obtained from the mid-media showed crack initiation at the thin center area. Conclusions Aortic tissues were successfully stretched biaxially until failure, and their crack initiation points were successfully observed under a microscope. This could be a very useful and powerful method for clarifying the mechanism of aortic rupture. We are planning to use this technique for a detailed investigation of events occurring at the point of failure when the crack initiates in the aortic aneurysm wall.
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Affiliation(s)
- Shukei Sugita
- Department of Mechanical Engineering, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan
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884
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Kisler K, Chow RH, Dominguez R. Fluorescently-Labeled Estradiol Internalization and Membrane Trafficking in Live N-38 Neuronal Cells Visualized with Total Internal Reflection Fluorescence Microscopy. ACTA ACUST UNITED AC 2013; Suppl 12. [PMID: 24353903 DOI: 10.4172/2157-7536.s12-002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Estradiol is a steroid hormone that binds and activates estradiol receptors. Activation of these receptors is known to modulate neuronal physiology and provide neuroprotection, but it is not completely understood how estradiol mediates these actions on the nervous system. Activation of a sub-population of estradiol receptor-α (ERα), originally identified as a nuclear protein, localizes to the plasma membrane and appears to be a critical step in neuroprotection against brain injury and disease. Previously we showed that estradiol stimulates the rapid and transient trafficking of plasma membrane ERα in primary hypothalamic neurons, and internalization of membrane-impermeant estradiol (E6BSA-FITC) into cortical neuron endosomes in vitro. These findings support the concept that estradiol activates and down-regulates plasma membrane ERα by triggering endocytosis. Here, we use TIRFM (total internal reflection fluorescence microscopy) to image the trafficking of E6BSA-FITC, and GFP-labeled ERα, in live cells in real time. We show that activation of plasma membrane ERs by E6BSA-FITC result in internalization of the fluorescent ligand in live N-38 neurons, an immortalized hypothalamic cell line. Pretreatment with ER antagonist ICI 182,780 decreased the number of E6BSA-FITC labeled puncta observed. We also observed in live N-38 neurons that E6BSA-FITC co-localized with FM4-64 and LysoTracker fluorescent dyes that label endosomes and lysosomes. Our results provide further evidence that plasma membrane ERα activation results in endocytosis of the receptor.
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Affiliation(s)
- Kassandra Kisler
- Zilkha Neurogenetic Institute, Department of Physiology and Biophysics, Keck School of Medicine of University of Southern California, USA
| | - Robert H Chow
- Zilkha Neurogenetic Institute, Department of Physiology and Biophysics, Keck School of Medicine of University of Southern California, USA
| | - Reymundo Dominguez
- Zilkha Neurogenetic Institute, Department of Physiology and Biophysics, Keck School of Medicine of University of Southern California, USA
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885
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Roche DG, Taylor MK, Binning SA, Johansen JL, Domenici P, Steffensen JF. Unsteady flow affects swimming energetics in a labriform fish (Cymatogaster aggregata). J Exp Biol 2013; 217:414-22. [DOI: 10.1242/jeb.085811] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Summary
Unsteady water flows are common in nature, yet the swimming performance of fishes is typically evaluated at constant, steady speeds in the laboratory. We examined how cyclic changes in water flow velocity affect the swimming performance and energetics of a labriform swimmer, the shiner surfperch, Cymatogaster aggregata. Using intermittent-flow respirometry, we measured critical swimming speed (Ucrit), oxygen consumption rate (ṀO2) and pectoral fin use in steady flow versus unsteady flows with either low (0.5 body lengths per second; BLs-1) or high amplitude (1.0 BLs-1) velocity fluctuations, with a 5 s period. Individuals in low amplitude unsteady flow performed as well as fish in steady flow. However, swimming costs in high amplitude unsteady flow were on average 25.3 % higher than in steady flow and 14.2% higher than estimated values obtained from simulations based on the non-linear relationship between swimming speed and oxygen consumption rate in steady flow. Time-averaged pectoral fin use (fin beat frequency measured over 300 s) was similar among treatments. However, measures of instantaneous fin use (fin beat period) and body movement in high amplitude unsteady flow indicate that individuals with greater variation in the duration of their fin beats were better at holding station and consumed less oxygen than fish with low variation in fin beat period. These results suggest that the costs of swimming in unsteady flows are context dependent in labriform swimmers, and may be influenced by individual differences in the ability of fishes to adjust their fin beats to the flow environment.
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886
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Sandbaumhüter M, Döhner K, Schipke J, Binz A, Pohlmann A, Sodeik B, Bauerfeind R. Cytosolic herpes simplex virus capsids not only require binding inner tegument protein pUL36 but also pUL37 for active transport prior to secondary envelopment. Cell Microbiol 2012. [PMID: 23186167 DOI: 10.1111/cmi.12075] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
As the inner tegument proteins pUL36 and pUL37 of alphaherpesviruses may contribute to efficient intracellular transport of viral particles, we investigated their role in cytosolic capsid motility during assembly of herpes simplex virus type 1 (HSV1). As reported previously for pUL36, untagged pUL37 and UL37GFP bound to cytosolic capsids before these acquired outer tegument and envelope proteins. Capsids tagged with CheVP26 analysed by live cell imaging were capable of directed long-distance cytoplasmic transport during the assembly of wild-type virions, while capsids of the HSV1-ΔUL37 or HSV1-ΔUL36 deletion mutants showed only random, undirected motion. The HSV1-ΔUL37 phenotype was restored when UL37GFP had been overexpressed prior to infection. Quantitative immunoelectron microscopy revealed that capsids of HSV1-ΔUL37 still recruited pUL36, whereas pUL37 did not colocalize with capsids of HSV1-ΔUL36. Nevertheless, the cytosolic capsids of neither mutant could undergo secondary envelopment. Our data suggest that pUL36 and pUL37 are important prior to their functions in linking the inner to the outer tegument. Efficient capsid transport to the organelle of secondary envelopment requires recruitment ofpUL37 onto capsids, most likely via its interaction with pUL36, while capsid-associated pUL36 alone is insufficient.
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Affiliation(s)
- Malte Sandbaumhüter
- Institute of Virology, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany
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887
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Tran LD, Hino H, Quach H, Lim S, Shindo A, Mimori-Kiyosue Y, Mione M, Ueno N, Winkler C, Hibi M, Sampath K. Dynamic microtubules at the vegetal cortex predict the embryonic axis in zebrafish. Development 2012; 139:3644-52. [PMID: 22949618 DOI: 10.1242/dev.082362] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In zebrafish, as in many animals, maternal dorsal determinants are vegetally localized in the egg and are transported after fertilization in a microtubule-dependent manner. However, the organization of early microtubules, their dynamics and their contribution to axis formation are not fully understood. Using live imaging, we identified two populations of microtubules, perpendicular bundles and parallel arrays, which are directionally oriented and detected exclusively at the vegetal cortex before the first cell division. Perpendicular bundles emanate from the vegetal cortex, extend towards the blastoderm, and orient along the animal-vegetal axis. Parallel arrays become asymmetric on the vegetal cortex, and orient towards dorsal. We show that the orientation of microtubules at 20 minutes post-fertilization can predict where the embryonic dorsal structures in zebrafish will form. Furthermore, we find that parallel microtubule arrays colocalize with wnt8a RNA, the candidate maternal dorsal factor. Vegetal cytoplasmic granules are displaced with parallel arrays by ~20°, providing in vivo evidence of a cortical rotation-like process in zebrafish. Cortical displacement requires parallel microtubule arrays, and probably contributes to asymmetric transport of maternal determinants. Formation of parallel arrays depends on Ca(2+) signaling. Thus, microtubule polarity and organization predicts the zebrafish embryonic axis. In addition, our results suggest that cortical rotation-like processes might be more common in early development than previously thought.
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Affiliation(s)
- Long Duc Tran
- Temasek Life Sciences Laboratory, 1 Research Link, 117604 Singapore
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888
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Zimmer C. From microbes to numbers: extracting meaningful quantities from images. Cell Microbiol 2012; 14:1828-35. [DOI: 10.1111/cmi.12032] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Revised: 08/29/2012] [Accepted: 08/30/2012] [Indexed: 11/26/2022]
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889
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El-Sherif E, Averof M, Brown SJ. A segmentation clock operating in blastoderm and germband stages of Tribolium development. Development 2012; 139:4341-6. [PMID: 23095886 DOI: 10.1242/dev.085126] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In Drosophila, all segments form in the blastoderm where morphogen gradients spanning the entire anterior-posterior axis of the embryo provide positional information. However, in the beetle Tribolium castaneum and most other arthropods, a number of anterior segments form in the blastoderm, and the remaining segments form sequentially from a posterior growth zone during germband elongation. Recently, the cyclic nature of the pair-rule gene Tc-odd-skipped was demonstrated in the growth zone of Tribolium, indicating that a vertebrate-like segmentation clock is employed in the germband stage of its development. This suggests that two mechanisms might function in the same organism: a Drosophila-like mechanism in the blastoderm, and a vertebrate-like mechanism in the germband. Here, we show that segmentation at both blastoderm and germband stages of Tribolium is based on a segmentation clock. Specifically, we show that the Tribolium primary pair-rule gene, Tc-even-skipped (Tc-eve), is expressed in waves propagating from the posterior pole and progressively slowing until they freeze into stripes; such dynamics are a hallmark of clock-based segmentation. Phase shifts between Tc-eve transcripts and protein confirm that these waves are due to expression dynamics. Moreover, by tracking cells in live embryos and by analyzing mitotic profiles, we found that neither cell movement nor oriented cell division could explain the observed wave dynamics of Tc-eve. These results pose intriguing evolutionary questions, as Drosophila and Tribolium segment their blastoderms using the same genes but different mechanisms.
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Affiliation(s)
- Ezzat El-Sherif
- Genetics Program, Kansas State University, Manhattan, KS 66506, USA
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890
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Swinnen N, Smolders S, Avila A, Notelaers K, Paesen R, Ameloot M, Brône B, Legendre P, Rigo JM. Complex invasion pattern of the cerebral cortex bymicroglial cells during development of the mouse embryo. Glia 2012; 61:150-63. [PMID: 23001583 DOI: 10.1002/glia.22421] [Citation(s) in RCA: 147] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Accepted: 08/28/2012] [Indexed: 12/12/2022]
Abstract
Microglia are the immune cells of the central nervous system. They are suspected to play important roles in adult synaptogenesis and in the development of the neuronal network. Microglial cells originate from progenitors in the yolk sac. Although it was suggested that they invade the cortex at early developmental stages in the embryo, their invasion pattern remains largely unknown. To address this issue we analyzed the pattern of cortical invasion by microglial cells in mouse embryos at the onset of neuronal cell migration using in vivo immunohistochemistry and ex vivo time-lapse analysis of microglial cells. Microglial cells begin to invade the cortex at 11.5 days of embryonic age (E11.5). They first accumulate at the pial surface and within the lateral ventricles, after which they spread throughout the cortical wall, avoiding the cortical plate region in later embryonic ages. The invasion of the cortical parenchyma occurs in different phases. First, there is a gradual increase of microglial cells between E10.5 and E14.5. From E14.5 to E15.5 there is a rapid phase with a massive increase in microglia, followed by a slow phase again from E15.5 until E17.5. At early stages, many peripheral microglia are actively proliferating before entering the parenchyma. Remarkably, activated microglia accumulate in the choroid plexus primordium, where they are in the proximity of dying cells. Time-lapse analysis shows that embryonic microglia are highly dynamic cells.
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Affiliation(s)
- Nina Swinnen
- Hasselt University, BIOMED, Agoralaan (Gebouw C), Diepenbeek B-3590, Belgium
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891
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Temperature dependent measurements reveal similarities between muscle and non-muscle myosin motility. J Muscle Res Cell Motil 2012; 33:385-94. [PMID: 22930330 DOI: 10.1007/s10974-012-9316-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Accepted: 08/06/2012] [Indexed: 10/28/2022]
Abstract
We examined the temperature dependence of muscle and non-muscle myosin (heavy meromyosin, HMM) with in vitro motility and actin-activated ATPase assays. Our results indicate that myosin V (MV) has a temperature dependence that is similar in both ATPase and motility assays. We demonstrate that skeletal muscle myosin (SK), smooth muscle myosin (SM), and non-muscle myosin IIA (NM) have different temperature dependence in ATPase compared to in vitro motility assays. In the class II myosins we examined (SK, SM, and NM) the rate-limiting step in ATPase assays is thought to be attachment to actin or phosphate release, while for in vitro motility assays it is controversial. In MV the rate-limiting step for both in vitro motility and ATPase assays is known to be ADP release. Consequently, in MV the temperature dependence of the ADP release rate constant is similar to the temperature dependence of in vitro motility. Interestingly, the temperature dependence of the ADP release rate constant of SM and NM was shifted toward the in vitro motility temperature dependence. Our results suggest that the rate-limiting step in SK, SM, and NM may shift from attachment-limited in solution to detachment limited in the in vitro motility assay. Internal strain within the myosin molecule or by neighboring myosin motors may slow ADP release which becomes rate-limiting in the in vitro motility assay. Within this small subset of myosins examined, the in vitro sliding velocity correlates reasonably well with actin-activated ATPase activity, which was suggested by the original study by Barany (J Gen Physiol 50:197-218, 1967).
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892
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Mechanical and kinetic properties of β-cardiac/slow skeletal muscle myosin. J Muscle Res Cell Motil 2012; 33:403-17. [DOI: 10.1007/s10974-012-9315-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Accepted: 07/06/2012] [Indexed: 11/26/2022]
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893
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Virtakoivu R, Pellinen T, Rantala JK, Perälä M, Ivaska J. Distinct roles of AKT isoforms in regulating β1-integrin activity, migration, and invasion in prostate cancer. Mol Biol Cell 2012; 23:3357-69. [PMID: 22809628 PMCID: PMC3431929 DOI: 10.1091/mbc.e12-03-0213] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
On the basis of an RNA interference screen, we identify AKT1 and AKT2 as inhibitors of β1-integrin activity and invasion in prostate cancer. AKT1 siRNA induces β-integrin activity and up-regulation of RTKs known to function in cooperation with integrins. In contrast, AKT2 siRNA up-regulates microRNA-200, which increases integrin activity. AKT1 and AKT2 kinases have been shown to play opposite roles in breast cancer migration and invasion. In this study, an RNA interference screen for integrin activity inhibitors identified AKT1 as an inhibitor of β1-integrin activity in prostate cancer. Validation experiments investigating all three AKT isoforms demonstrated that, unlike in breast cancer, both AKT1 and AKT2 function as negative regulators of cell migration and invasion in PC3 prostate cancer cells. Down-regulation of AKT1 and AKT2, but not AKT3, induced activation of cell surface β1-integrins and enhanced adhesion, migration, and invasion. Silencing of AKT1 and AKT2 also resulted in increased focal adhesion size. Importantly, the mechanisms involved in integrin activity regulation were distinct for the two AKT isoforms. Silencing of AKT1 relieved feedback suppression of the expression and activity of several receptor tyrosine kinases, including EGFR and MET, with established cross-talk with β1-integrins. Silencing of AKT2, on the other hand, induced up-regulation of the microRNA-200 (miR-200) family, and overexpression of miR-200 was sufficient to induce integrin activity and cell migration in PC3 cells. Taken together, these data define an inhibitory role for both AKT1 and AKT2 in prostate cancer migration and invasion and highlight the cell type–specific actions of AKT kinases in the regulation of cell motility.
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894
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Nikolic-Jaric M, Romanuik SF, Ferrier GA, Cabel T, Salimi E, Levin DB, Bridges GE, Thomson DJ. Electronic detection of dielectrophoretic forces exerted on particles flowing over interdigitated electrodes. BIOMICROFLUIDICS 2012; 6:24117-2411715. [PMID: 22655025 PMCID: PMC3360729 DOI: 10.1063/1.4709387] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2012] [Accepted: 04/13/2012] [Indexed: 05/16/2023]
Abstract
Dielectric particles flowing through a microfluidic channel over a set of coplanar electrodes can be simultaneously capacitively detected and dielectrophoretically (DEP) actuated when the high (1.45 GHz) and low (100 kHz-20 MHz) frequency electromagnetic fields are concurrently applied through the same set of electrodes. Assuming a simple model in which the only forces acting upon the particles are apparent gravity, hydrodynamic lift, DEP force, and fluid drag, actuated particle trajectories can be obtained as numerical solutions of the equations of motion. Numerically calculated changes of particle elevations resulting from the actuation simulated in this way agree with the corresponding elevation changes estimated from the electronic signatures generated by the experimentally actuated particles. This verifies the model and confirms the correlation between the DEP force and the electronic signature profile. It follows that the electronic signatures can be used to quantify the actuation that the dielectric particle experiences as it traverses the electrode region. Using this principle, particles with different dielectric properties can be effectively identified based exclusively on their signature profile. This approach was used to differentiate viable from non-viable yeast cells (Saccharomyces cerevisiae).
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895
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A MatP-divisome interaction coordinates chromosome segregation with cell division in E. coli. EMBO J 2012; 31:3198-211. [PMID: 22580828 DOI: 10.1038/emboj.2012.128] [Citation(s) in RCA: 142] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Accepted: 04/12/2012] [Indexed: 11/09/2022] Open
Abstract
Initiation of chromosome segregation in bacteria is achieved by proteins acting near the origin of replication. Here, we report that the precise choreography of the terminus region of the Escherichia coli chromosome is also tightly controlled. The segregation of the terminus (Ter) macrodomain (MD) involves the structuring factor MatP. We characterized that migration of the Ter MD from the new pole to mid-cell and its subsequent persistent localization at mid-cell relies on several processes. First, the replication of the Ter DNA is concomitant with its recruitment from the new pole to mid-cell in a sequential order correlated with the position on the genetic map. Second, using a strain carrying a linear chromosome with the Ter MD split in two parts, we show that replisomes are repositioned at mid-cell when replication of the Ter occurs. Third, we demonstrate that anchoring the Ter MD at mid-cell depends on the specific interaction of MatP with the division apparatus-associated protein ZapB. Our results reveal how segregation of the Ter MD is integrated in the cell-cycle control.
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896
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Regulation of PP2A activity by Mid1 controls cranial neural crest speed and gangliogenesis. Mech Dev 2012; 128:560-76. [DOI: 10.1016/j.mod.2012.01.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Revised: 01/05/2012] [Accepted: 01/11/2012] [Indexed: 12/22/2022]
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