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Past Issue in 2016
Volume: 6, Issue: 23
Cancer Biology
DNA Damage Induction by Laser Microirradiation
Genome instability can lead to cell death, senescence and cancerous transformation. Specific repair pathways have evolved to prevent accumulation of DNA lesions. Studying these highly dynamic and specific repair pathways requires precise spatial and temporal resolution, which can be achieved through a combination of laser microirradiaiton and live cell microscopy. DNA lesions are introduced at pre-determined sub-nuclear sites and repair can be analyzed in real time in living cells when using fluorescently tagged repair proteins (Mortusewicz et al., 2008). Alternatively, laser microirradiation can be combined with immunofluorescence analysis to study recruitment of endogenous proteins to laser-induced DNA damage tracks that can be visualized by positive controls like, e.g., γH2AX that mark sites of DNA breaks.
Lentiviral shRNA Screen to Identify Epithelial Integrity Regulating Genes in MCF10A 3D Culture
MCF10A 3D culture system provides a reductionist model of glandular mammary epithelium which is widely used to study development of glandular architecture, the role of cell polarity and epithelial integrity in control of epithelial cell functions, and mechanisms of breast cancer. Here we describe how to use shRNA screening approach to identify critical cell pathways that couple epithelial structure to individual cell based responses such as cell cycle exit and apoptosis. These studies will help to interrogate genetic changes critical for early breast tumorigenesis. The protocol describes a library of lentiviral shRNA constructs designed to target epithelial integrity and a highly efficient method for lentiviral transduction of suspension MCF10A cultures. Furthermore, protocols are provided for setting up MCF10A 3D cultures in Matrigel for morphometric and cellular response studies via structured illumination and confocal microscopy analysis of immunostained 3D structures.
Cell Biology
Lymphocyte Isolation, Th17 Cell Differentiation, Activation, and Staining
In vitro Th17 (α, β T helper cell which produce IL-17A, IL-17F and IL-22) differentiation has been routinely used for functional T cells studies. Here we describe a method for Th17 cell differentiation.
Isolation of Latex Bead Phagosomes from Dictyostelium for in vitro Functional Assays
We describe a protocol to purify latex bead phagosomes (LBPs) from Dictyostelium cells. These can be later used for various in vitro functional assays. For instance, we use these LBPs to understand the microtubule motor-driven transport on in vitro polymerized microtubules. Phagosomes are allowed to mature for defined periods inside cells before extraction for in vitro motility. These assays allow us to probe how lipids on the phagosome membrane recruit and organize motors, and also measure the motion and force generation resulting from underlying lipid-motor interactions. This provides a unique opportunity to interrogate native-like organelles using biophysical and biochemical assays, and understand the role of motor proteins in phagosome maturation and pathogen clearance.
Analysis of Myosin II Minifilament Orientation at Epithelial Zonula Adherens
Non-muscle myosin II (NMII) form bipolar filaments, which bind F-actin to exert cellular contractility during physiological processes (Vicente-Manzanares et al., 2009). Using a combinatorial approach to fluorescently label both N- and C-termini of the NMII heavy chain, recent works have demonstrated the ability to visualize NMII bipolar filaments at various subcellular localizations (Ebrahim et al., 2013; Beach et al., 2014). At the zonula adherens (ZA) of epithelia, NMII minifilaments bind the circumferential actin bundles in a pseudo-sarcomeric manner (Ebrahim et al., 2013), a conformation required to maintain junctional tension and tissue integrity (Ratheesh et al., 2012). By expressing green fluorescent protein (GFP)-NMIIA heavy chain and immunolabel it using a NMIIA C-terminus specific antibody, we were able to visualize the NMII minifilaments bound to F-actin bundles in Caco-2 cells (Michael et al., 2016), as previously reported (Ebrahim et al., 2013; Beach et al., 2014). In addition, we designed an FIJI/MATLAB analysis module to quantify the size, distance and alignment of these minifilaments with respect to junctional F-actin at the ZA. Measurements of the dispersion of minifilaments angles were proven to be a useful parameter that closely correlated to the extent of contractility at junctions (Michael et al., 2016).
Developmental Biology
Vascular Smooth Muscle Cell Isolation and Culture from Mouse Aorta
Vascular smooth muscle cells (SMC) in the ascending thoracic aorta arise from neural crest cells, whereas SMCs in the descending aorta are derived from the presomitic mesoderm. SMCs play important roles in cardiovascular development and aortic aneurysm formation. This protocol describes the detailed process for explanting ascending and descending SMCs from mouse aortic tissue. Conditions for maintenance and subculture of isolated SMCs and characterization of the vascular SMC phenotype are also described.
Intracellular Assessment of ATP Levels in Caenorhabditis elegans
Eukaryotic cells heavily depend on adenosine triphosphate (ATP) generated by oxidative phosphorylation (OXPHOS) within mitochondria. ATP is the major energy currency molecule, which fuels cell to carry out numerous processes, including growth, differentiation, transportation and cell death among others (Khakh and Burnstock, 2009). Therefore, ATP levels can serve as a metabolic gauge for cellular homeostasis and survival (Artal-Sanz and Tavernarakis, 2009; Gomes et al., 2011; Palikaras et al., 2015). In this protocol, we describe a method for the determination of intracellular ATP levels using a bioluminescence approach in the nematode Caenorhabditis elegans.
Measuring Oxygen Consumption Rate in Caenorhabditis elegans
The rate of oxygen consumption is a vital marker indicating cellular function during lifetime under normal or metabolically challenged conditions. It is used broadly to study mitochondrial function (Artal-Sanz and Tavernarakis, 2009; Palikaras et al., 2015; Ryu et al., 2016) or investigate factors mediating the switch from oxidative phosphorylation to aerobic glycolysis (Chen et al., 2015; Vander Heiden et al., 2009). In this protocol, we describe a method for the determination of oxygen consumption rates in the nematode Caenorhabditis elegans.
Microbiology
Pyocyanin Extraction and Quantitative Analysis in Swarming Pseudomonas aeruginosa
This protocol describes the quantification of pyocyanin extracted from swarming colonies of Pseudomonas aeruginosa. Pyocyanin is a secondary metabolite and a major virulence factor, whose production is inducible and varies highly under different growth conditions. The protocol is based on the earlier developed chloroform/HCl extraction of pyocyanin from liquid cultures (Frank and Demoss, 1959). Swarming colonies together with the agar they occupy are split into two halves. Pyocyanin is extracted from one of them. Cells are collected from the other half and used to quantify total protein yield and normalize the estimated corresponding pyocyanin quantities.
Murine Leukemia Virus (MLV)-based Coronavirus Spike-pseudotyped Particle Production and Infection
Viral pseudotyped particles (pp) are enveloped virus particles, typically derived from retroviruses or rhabdoviruses, that harbor heterologous envelope glycoproteins on their surface and a genome lacking essential genes. These synthetic viral particles are safer surrogates of native viruses and acquire the tropism and host entry pathway characteristics governed by the heterologous envelope glycoprotein used. They have proven to be very useful tools used in research with many applications, such as enabling the study of entry pathways of enveloped viruses and to generate effective gene-delivery vectors. The basis for their generation lies in the capacity of some viruses, such as murine leukemia virus (MLV), to incorporate envelope glycoproteins of other viruses into a pseudotyped virus particle. These can be engineered to contain reporter genes such as luciferase, enabling quantification of virus entry events upon pseudotyped particle infection with susceptible cells. Here, we detail a protocol enabling generation of MLV-based pseudotyped particles, using the Middle East respiratory syndrome coronavirus (MERS-CoV) spike (S) as an example of a heterologous envelope glycoprotein to be incorporated. We also describe how these particles are used to infect susceptible cells and to perform a quantitative infectivity readout by a luciferase assay.
Single Cell Flow Cytometry Assay for Peptide Uptake by Bacteria
Antimicrobial peptides (AMPs) can target the bacterial envelope or alternatively have intracellular targets. The latter requires uptake of the peptide by the bacterial cells. The bacterial internalization of an AMP can be evaluated by a fluorescence-based method that couples the use of the fluorescently labelled AMP to the fluorescence quencher trypan blue. Trypan blue is excluded from the interior of intact cells and the fluorescence of the extracellular peptide or of the peptide bound on the bacterial surface can be quenched by it, while the fluorescence of the internalized peptide is not affected. The uptake of the peptide by the bacteria is determined by measuring the fluorescence in individual cells by flow cytometry.
In vitro Autophosphorylation and Phosphotransfer Assay of Cyanobacterial Histidine Kinase 2
This is a detailed protocol of an autophosphorylation and phosphotransfer activities of Synechocystis sp. PCC 6803 full-length Histidine Kinase 2 (Hik2) protein described by Ibrahim et al., 2016. In this protocol, radioactively labelled ATP was used to study an autophosphorylation and phosphotransfer activity of the full-length Hik2 protein.
Preparation of Purified Gram-positive Bacterial Cell Wall and Detection in Placenta and Fetal Tissues
Cell wall is a complex biopolymer on the surface of all Gram-positive bacteria. During infection, cell wall is recognized by the innate immune receptor Toll-like receptor 2 causing intense inflammation and tissue damage. In animal models, cell wall traffics from the blood stream to many organs in the body, including brain, heart, placenta and fetus. This protocol describes how to prepare purified cell wall from Streptococcus pneumoniae, detect its distribution in animal tissues, and study the tissue response using the placenta and fetal brain as examples.
Mouse Model of Dengue Virus Infection with Serotypes 1 and 2 Clinical Isolates
Dengue is a global public health threat caused by infection with any of the 4 related dengue virus serotypes (DENV1-4). Clinical manifestations range from self-limiting febrile illness, known as dengue fever (DF), to life-threatening severe diseases, such as dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS). Most cases of DHF/DSS are associated with secondary heterotypic infections through a phenomenon that is described as antibody-dependent enhancement of infection (ADE). There are an estimated 400 million human infections and several hundred thousand cases of severe dengue occurring yearly. At present, however, there are no approved antiviral drugs against DENV infection. The lack of a suitable animal model has hampered the evaluation of novel antiviral candidates for DENV infection. Since DENV poorly establishes infection in immunocompetent mice, AG129 mice (lacking type I and II IFN [interferon] receptors) and mouse-adapted DENV2 strains have been applied to dengue animal models that enable to reproduce several of the major pathologies of human infection. Recently, we developed new mouse models with clinical isolates DENV1 and DENV2 that would be useful for drug testing and dengue pathogenesis studies (Watanabe et al., 2016). Here we describe the details to establish dengue mouse models of clinical isolates; from in vitro preparation of the materials to in vivo virus infection. Of note, since infectivity of DENV in mice differs among virus strains, not all clinical isolates can induce severe dengue.
Measurement of Intracellular Calcium Concentration in Pseudomonas aeruginosa
Characterization of the molecular mechanisms of calcium (Ca2+) regulation of bacterial physiology and virulence requires tools enabling measuring and monitoring the intracellular levels of free calcium (Ca2+in). Here, we describe a protocol optimized to use a recombinantly expressed Ca2+-binding protein, aequorin, for detecting Ca2+in in Pseudomonas aeruginosa. Upon binding to free Ca2+, aequorin undergoes chromophore oxidation and emits light, the log of which intensity linearly correlates with the amount of bound Ca2+, and therefore, can be used to measure the concentration of free Ca2+ available for binding. This protocol involves the introduction of the aequorin gene into P. aeruginosa, induction of apoaequorin production, reconstitution of the holoenzyme with its chromophore, and monitoring its luminescence. This protocol allows continuous measuring of Ca2+in concentration in vivo in response to various stimuli.
Neuroscience
Delayed Spatial Win-shift Test on Radial Arm Maze
The radial arm maze (RAM) is used to assess reference and working memory in rodents. This task relies on the rodent’s ability to orientate itself in the maze using extra-maze visual cues. This test can be used to investigate whether a rodent’s cognition is improved or impaired under a variety of experimental conditions. Here, we describe one way to test spatial working and reference memory. This delayed spatial win-shift (DSWS) procedure on the RAM was adapted from Packard and White (1990). The win-shift component of the test refers to the alternation of baiting, or rewarding, arms during the trial and test phase. The rodent is required to hold spatial information both within the task and across a delay to obtain the food-pellet reward (Taylor et al., 2003b). This task measures the incidence and type of memory errors made by the rodent both in the training and test phases of the learning task. A working memory error (re-entry of an arm that has been baited) can occur in both phases of the task, whilst a reference memory error (entry into an arm that has been baited during the training phase and is no longer baited) can only occur during the test phase.
Various Modes of Spinal Cord Injury to Study Regeneration in Adult Zebrafish
Spinal cord injury (SCI) in mammals leads to failure of both sensory and motor functions, due to lack of axonal regrowth below the level of injury as well as inability to replace lost neural cells and to stimulate neurogenesis. In contrast, fish and amphibians are capable of regenerating a variety of their organs like limb/fin, jaw, heart and various parts of the central nervous system (CNS). Zebrafish embryo and adult has become a very popular model to study developmental biology, cell biology and regeneration for various reasons. Adult zebrafish, one of the most important vertebrate models to study regeneration, can regenerate many of their body parts like fin, jaw, heart and CNS. In the present article we provide information on how to inflict different injury modalities in adult fish spinal cord. Presently, the significant focus of mammalian SCI is to use crush and contusion injury. To generate an entity comparable to the mammalian mode of injury, we have introduced the crush model in adult zebrafish along with complete transection injury, which is also known to be a valuable model to study axonal regeneration. Here we provide full description of the highly reproducible surgical procedures including some representative results. This protocol has been adapted from our previous publications, viz. Hui et al., 2010 and Hui et al., 2014. Briefly, we have described the two different injury modalities, crush and complete transection, and demonstrated the outcome of inflicting these injuries in the adult zebrafish cord by histological analysis of the tissues.
MPM-2 Mediated Immunoprecipitation of Proteins Undergoing Proline-directed Phosphorylation
Immunoprecipitation (IP) represents a widely utilized biochemical method to isolate a specific protein from a complex mixture taking advantage of an antibody that specifically recognizes that particular target molecule. This procedure is extremely versatile and can be applied to concentrate a specific protein, to identify interacting partners in complex with it or to detect post-translational modifications. The mitotic protein monoclonal 2 (MPM-2) is an antibody originally raised against extracts of synchronized mitotic HeLa cells to identify proteins selectively present in mitotic, and not in interphase-cells (Davis et al., 1983). MPM-2 recognizes phosphorylated serine or threonine residues followed by proline (pS/T-P), consensus epitopes generated by the concerted action of proline-directed protein kinases and phosphatases (Lu et al., 2002). These reversible phosphorylation events have emerged to control various cellular processes by promoting conformational changes on the target that are not simply due to the phosphorylation event per se. These motifs, once phosphorylated, are able to recruit Pin1 (Peptidyl-prolyl Isomerase NIMA interacting protein 1) (Lu et al., 1996; Lu and Zhou, 2007), a chaperone which drives the cis/trans isomerization reaction on the peptide bond, switching the substrate between functionally diverse conformations (Lu, 2004; Wulf et al., 2005). This protocol describes a general MPM-2 based immunoprecipitation strategy using the scaffolding molecule postsynaptic density protein-95 (PSD-95) (Chen et al., 2005), a neuronal Pin1 target (Antonelli et al., 2016), as an example to illustrate the detailed procedure.
Plant Science
A Golden Gate-based Protocol for Assembly of Multiplexed gRNA Expression Arrays for CRISPR/Cas9
The CRISPR (clustered regularly interspaced short palindromic repeats)-associated protein 9 (Cas9) has become the most broadly used and powerful tool for genome editing. Many applications of CRISPR-Cas9 require the delivery of multiple small guide RNAs (gRNAs) into the same cell in order to achieve multiplexed gene editing or regulation. Using traditional co-transfection of single gRNA expression vectors, the likelihood of delivering several gRNAs into the same cell decreases in accordance with the number of gRNAs. Thus, we have developed a method to efficiently assemble gRNA expression cassettes (2-30 gRNAs) into one single vector using a Golden-Gate assembly method (Vad-Nielsen et al., 2016). In this protocol, we describe the detailed step-by-step instructions for assembly of the multiplexed gRNA expression array. The gRNA scaffold used in our expression array is the gRNA 1.0 system for the Cas9 protein from Streptococcus pyogenes driven by the human U6 promoter.
Tandem Purification of His6-3x FLAG Tagged Proteins for Mass Spectrometry from Arabidopsis
Tandem affinity purification is a powerful method to identify protein complexes that function in association with a known gene of interest. This protocol describes a methodology to capture proteins tagged with His6-3x FLAG explicitly for the purpose of on-bead digestion and identification by mass spectrometry. The high sensitivity and specificity of our methods allow for purification of proteins expressed at native levels from endogenous promoters to enable uncovering the functional roles of plant protein complexes.
Fusarium graminearum Maize Stalk Infection Assay and Associated Microscopic Observation Protocol
The ascomycete fungus Fusarium graminearum (previously also called Gibberella zeae) causes Gibberella stalk rot in maize (Zea mays) and results in lodging and serious yield reduction. To develop methods to assess the fungal growth and symptom development in maize stalks, we present here a protocol of maize stalk inoculation with conidiospores of fluorescent protein-tagged F. graminearumand microscopic observation of the stalk infection process. The inoculation protocol provides repeatable results in stalk rot symptom development, and allows tracking of fungal hyphal growth inside maize stalks at cellular scale.
Extraction and Measurement of Abscisic Acid in a Unicellular Red Alga Cyanidioschyzon merolae
Abscisic acid (ABA) has been known as a phytohormone of land plants, which is synthesized in response to abiotic stresses and induces various physiological responses, but is also found from eukaryotic algae. Recently, we reported that a unicellular red alga Cyanidioschyzon merolae produced ABA, which prevented cell growth and enhanced salt stress tolerance (Kobayashi et al., 2016). This report describes the detailed method for the extraction and quantification of ABA in the model red alga C. merolae.
Microplate Assay to Study Carboxypeptidase A Inhibition in Andean Potatoes
Metallocarboxypeptidases (MCP) are zinc-dependent exopeptidases that catalyze the hydrolysis of C-terminal amide bonds in proteins and peptides. They are involved in a wide range of physiological processes and have recently emerged as relevant drug targets in biomedicine (Arolas et al., 2007). In this context, the study and discovery of new MCP inhibitors from plants constitute a valuable approach for the development of new therapeutic strategies. Herein we describe a simple and accessible microplate method for the study of the specific and dose-response carboxypeptidase A inhibitory activities present in Andean potato tubers. Our protocol combines an extraction method optimized for small protein inhibitors in plant tissues, with the measurement of enzyme kinetics using a microplate reader. These instruments are capable of reading small sample volumes, for many samples in a very short time-frame, therefore reducing the time and costs of high-throughput screening experiments. Although this protocol describes the study of Andean potatoes, our approach is also applicable to the analysis other plant samples.
Shoot Apical Meristem Size Measurement
The shoot apical meristem (SAM) is a collection of cells that continuously renew themselves by cell division and also provide cells to newly developing organs. It has been known that CLAVATA (CLV) 3 peptide regulates a transcription factor WUSCHEL (WUS) to keep numbers of undifferentiated cells constant and maintain the size of the SAM. The interactive feedback control of CLV3 and WUS in a non-cell autonomous signaling cascade determines stem cell fate (maintenance of pluripotency or, alternatively, differentiation into daughter cells) in the SAM. Ca2+ is a secondary messenger that plays a significant role in numerous signaling pathways. The signaling system connecting CLV3 binding to its receptor and WUS expression is not well delineated. We showed that Ca2+ is involved in CLV3 regulation of the SAM size. One of the approaches we used was measuring the size of the SAM. Here we provide a detailed protocol on how to measure Arabidopsis SAM size with Nomarski microscopy. The area of the two-dimensional dome representing the maximal ‘face’ of the SAM was used as a proxy for SAM size. Studies were done on wild type (WT) Arabidopsis in the presence and absence of a Ca2+ channel blocker Gd3+ and the CLV3 peptide, as well on genotypes that lack functional CLV3 (clv3) or a gene encoding a Ca2+-conducting ion channel (‘dnd1’).
Measurement of ATP Hydrolytic Activity of Plasma Membrane H+-ATPase from Arabidopsis thaliana Leaves
Plant plasma membrane H+-ATPase, which is a P-type ATPase, couples ATP hydrolysis to H+ extrusion and thereby generates an electrochemical gradient across the plasma membrane. The proton gradient is necessary for secondary transport, cell elongation, and membrane potential maintenance. Here we describe a protocol for measurement of the ATP hydrolytic activity of the plasma membrane H+-ATPase from Arabidopsis thaliana leaves.
Isolating and Measuring the Growth and Morphology of Pro-embryogenic Masses in Araucaria angustifolia (Bertol.) Kuntze (Araucariaceae)
Embryogenic suspension cultures of Araucaria angustifolia (Bertol.) Kuntze (Araucariaceae) can be used as a model to test the effects of compounds added to the culture medium on the cellular growth and morphology of Pro-Embryogenic Masses (PEMs). PEMs are formed by embryogenic and suspensor-type cells. To measure changes in the cellular growth of embryogenic cultures, we performed sedimented cell volume (SCV) quantification, which is a non-destructive method. Morphological analysis by microscopy allowed for the observation of growth and development of PEMs and the alterations in embryogenic and suspensor-type cells. The methods used here provide an efficient means for monitoring the cellular growth of PEMs and identifying morphological changes during the development of embryogenic cultures. These studies can also be combined with biochemical and molecular analyses, such as proteomics, to further investigate embryo growth and morphology.
Stem Cell
In vitro Chondrogenic Hypertrophy Induction of Mesenchymal Stem Cells
To investigate underlying mechanism of chondrogenic hypertrophy, we need proper in vitro hypertrophic model of mesenchymal stem cells (MSCs). This protocol describes our defined method for induction of in vitro chondrogenic hypertrophy of human umbilical cord blood-derived MSCs (hUCB-MSCs). By adding thyroid hormone (T3; triiodothyronine) and minimum osteogenic-inducing factors to culture medium, we could induce hypertrophy of hUCB-MSCs in vitro. Hypertrophic induction was validated using immunohistochemical analysis, Western blotting and reverse transcriptase polymerase chain reaction.
Systems Biology
Protocol for Molecular Dynamics Simulations of Proteins
Molecular dynamics (MD) simulations have become one of the most important tools in understanding the behavior of bio-molecules on nanosecond to microsecond time scales. In this protocol, we provide a general approach and standard setup protocol for MD simulations by using the Gromacs MD suite.