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Past Issue in 2017
Volume: 7, Issue: 5
Cancer Biology
Liposome Flotation Assays for Phosphoinositide-protein Interaction
Phosphoinositides are rare membrane lipids involved in the control of the major cellular functions and signaling pathways. They are able to recruit specific effector proteins to the cytosolic face of plasma membrane and organelles to coordinate a vast variety of signaling and trafficking processes, as well to maintain specific identity of the different subcellular compartments (Di Paolo and De Camilli, 2006; Lemmon, 2003). Therefore, analysis of these effectors’ binding properties and specificity towards different phosphoinositides is crucial for the understanding of their cellular functions. This protocol describes a method to characterize the binding of proteins to different phosphoinositide-containing vesicles.
Ca2+ Measurements in Mammalian Cells with Aequorin-based Probes
Aequorin is a Ca2+ sensitive photoprotein suitable to measure intracellular Ca2+ transients in mammalian cells. Thanks to recombinant cDNAs expression, aequorin can be specifically targeted to various subcellular compartments, thus allowing an accurate measurement of Ca2+ uptake and release of different intracellular organelles. Here, we describe how to use this probe to measure cytosolic Ca2+ levels and mitochondrial Ca2+ uptake in mammalian cells.
Developmental Biology
Protein Synthesis Rate Assessment by Fluorescence Recovery after Photobleaching (FRAP)
Currently available biochemical methods cannot be applied to monitor protein synthesis in specific cells or tissues, in live specimens. Here, we describe a non-invasive method for monitoring protein synthesis in single cells or tissues with intrinsically different translation rates, in live Caenorhabditis elegans animals.
Microbiology
Isolation of Outer Membrane Vesicles from Phytopathogenic Xanthomonas campestris pv. campestris
Gram-negative bacteria naturally release outer membrane vesicles (OMVs) to the surrounding environment. OMVs contribute to multiple processes, such as cell-cell communication, delivery of enzymes and toxins, resistance to environmental stresses and pathogenesis. Little is known about OMVs produced by plant-pathogenic bacteria, and their interactions with host plants. The protocol described below discusses the isolation process of OMVs from Xanthomonas campestris pv. campestris strain 33913, a bacterial pathogen of Crucifiers. Nevertheless, this protocol can be used and/or adapted for isolation of OMVs from other phytopathogenic bacteria to promote the study of OMVs in the context of plant-microbe interactions.
Transient Transfection-based Fusion Assay for Viral Proteins
Membrane fusion is vital for entry of enveloped viruses into host cells as well as for direct viral cell-to-cell spread. To understand the fusion mechanism in more detail, we use an infection free system whereby fusion can be induced by a minimal set of the alphaherpesvirus pseudorabies virus (PrV) glycoproteins gB, gH and gL. Here, we describe an optimized protocol of a transient transfection based fusion assay to quantify cell-cell fusion induced by the PrV glycoproteins.
Determination of Elemental Concentrations in Lichens Using ICP-AES/MS
Lichens are good biomonitors for air pollution because of their high enrichment capability of atmospheric chemical elements. To monitor atmospheric element deposition using lichens, it is important to obtain information on the multi-element concentrations in lichen thalli. Because of serious air pollution, elemental concentrations in thalli of lichens from North China (especially Inner Mongolia, Hebei, Shanxi and Henan province) are often higher than those from other regions, therefore highlighting the necessity to optimize ICP-AES/MS (Inductively coupled plasma-atomic emission spectroscopy/mass spectrometry) for analyzing lichen element content. Based on the high elemental concentrations in the lichen samples, and the differences in the sensitivity and detection limits between ICP-MS and ICP-AES, we propose a protocol for analyzing 31 elements in lichens using ICP-AES/MS. Twenty-two elements (Cd, Ce, Co, Cr, Cs, Cu, K, La, Mo, Na, Ni, Pb, Rb, Sb, Sc, Sm, Sr, Tb, Th, Tl, V and Zn) can be identified by using microwave digestion- ICP-MS, and 9 elements (Al, Ba, Ca, Fe, Mg, Mn, P, S and Ti) by using ashing-alkali fusion digestion- ICP-AES.
Next-generation Sequencing of the DNA Virome from Fecal Samples
Herein we describe a detailed protocol for DNA virome analysis of low input human stool samples (Monaco et al., 2016). This protocol is divided into four main steps: 1) stool samples are pulverized to evenly distribute microbial matter; 2) stool is enriched for virus-like particles and DNA is extracted by phenol-chloroform; 3) purified DNA is multiple-strand displacement amplified (MDA) and fragmented; and 4) libraries are constructed and sequenced using Illumina Miseq. Subsequent sequence analysis for viral sequence identification should be sensitive but stringent.
Polyethylene Glycol-mediated Transformation of Drechmeria coniospora
Drechmeria coniospora is a nematophagous fungus and potential biocontrol agent. It belongs to the Ascomycota. It is related to Hirsutella minnesotensis, another nematophagous fungus but, phylogenetically, it is currently closest to the truffle parasite Tolypocladium ophioglossoides. Together with its natural host, Caenorhabditis elegans, it is used to study host-pathogen interactions. Here, we report a polyethylene glycol-mediated transformation method (Turgeon et al., 2010; Ochman et al., 1988) for this fungus. The protocol can be used to generate both knock-in or knock-out strains (Lebrigand et al., 2016).
An HPLC-based Method to Quantify Coronatine Production by Bacteria
Coronatine is a polyketide phytotoxin produced by several pathovars of the plant pathogenic bacterium Pseudomonas syringae. It is one of the most important virulence factors determining the success of bacterial pathogenesis in the plant at both epiphytic and endophytic stages of the disease cycle. This protocol describes an optimized procedure to culture bacterial cells for coronatine production and to quantify the amount of coronatine secreted in the culture medium using an HPLC-based method.
Chitin Extraction and Content Measurement in Magnaporthe oryzae
Chitin is a linear polysaccharide composed of β (1→4)-linked N-acetylglucosamine (GlcNAc) residues. In fungi, chitin is an important component of the cell wall. Here, we provide a protocol to measure the chitin content of fungal cells using Magnaporthe oryzae as an example.
Neuroscience
Extracellular Axon Stimulation
This is a detailed protocol explaining how to perform extracellular axon stimulations as described in Städele and Stein, 2016. The ability to stimulate and record action potentials is essential to electrophysiological examinations of neuronal function. Extracellular stimulation of axons traveling in fiber bundles (nerves) is a classical technique in brain research and a fundamental tool in neurophysiology (Abbas and Miller, 2004; Barry, 2015; Basser and Roth, 2000; Cogan, 2008). It allows for activating action potentials in individual or multiple axons, controlling their firing frequency, provides information about the speed of neuronal communication, and neuron health and function.
Axonal Conduction Velocity Measurement
Action potential conduction velocity is the speed at which an action potential (AP) propagates along an axon. Measuring AP conduction velocity is instrumental in determining neuron health, function, and computational capability, as well as in determining short-term dynamics of neuronal communication and AP initiation (Ballo and Bucher, 2009; Bullock, 1951; Meeks and Mennerick, 2007; Rosenthal and Bezanilla, 2000; Städele and Stein, 2016; Swadlow and Waxman, 1976). Conduction velocity can be measured using extracellular recordings along the nerve through which the axon projects. Depending on the number of axons in the nerve, AP velocities of individual or many axons can be detected. This protocol outlines how to measure AP conduction velocity of (A) stimulated APs and (B) spontaneously generated APs by using two spatially distant extracellular electrodes. Although an invertebrate nervous system is used here, the principles of this technique are universal and can be easily adjusted to other nervous system preparations (including vertebrates).
Olfactory Habituation-dishabituation Test (Mouse)
Olfaction plays a fundamental role in the various behaviors such as feeding, mating, nursing, and avoidance in mice. Behavioral tests that characterize abilities of odor detection and recognition using genetically modified mice reveal the contribution of target genes to the olfactory processing. Here, we describe the olfactory habituation-dishabituation test for investigating the odor detection threshold in mice.
Olfactory Avoidance Test (Mouse)
In mice, olfaction plays a pivotal role for the various behaviors, such as feeding, mating, nursing and avoidance. Behavioral tests that analyze abilities of odor detection and recognition using genetically modified mice reveal the contribution of target genes to the olfactory processing. Here, we describe the olfactory avoidance test to investigate the odor detection ability in mice.
Thinned-skulled Cranial Window Preparation (Mice)
Imaging structural plasticity or activity of neurons in the brain circuit will facilitate understanding the neural mechanisms underlying animal behavior. Here we describe a modified procedure, the polished and reinforced thinned-skull cranial window preparation, by which we can image dendrites and spines in mouse layer I cortex for weeks (Zhang et al., 2016). By this method, we also imaged the glioma initiation in the mouse cortex for two weeks in previous work (Zhang et al., 2012), which included the photographs and video for reference.
Plant Science
Acetyl Bromide Soluble Lignin (ABSL) Assay for Total Lignin Quantification from Plant Biomass
Lignin is the second most abundant biopolymer on Earth, providing plants with mechanical support in secondary cell walls and defense against abiotic and biotic stresses. However, lignin also acts as a barrier to biomass saccharification for biofuel generation (Carroll and Somerville, 2009; Zhao and Dixon, 2011; Wang et al., 2013). For these reasons, studying the properties of lignin is of great interest to researchers in agriculture and bioenergy fields. This protocol describes the acetyl bromide method of total lignin extraction and quantification, which is favored among other methods for its high recovery, consistency, and insensitivity to different tissue types (Johnson et al., 1961; Chang et al., 2008; Moreira-Vilar et al., 2014; Kapp et al., 2015). In brief, acetyl bromide digestion causes the formation of acetyl derivatives on free hydroxyl groups and bromide substitution of α-carbon hydroxyl groups on the lignin backbone to cause a complete solubilization of lignin, which can be quantified using known extinction coefficients and absorbance at 280 nm (Moreira-Vilar et al., 2014).
In Gel Kinase Assay
Proper spatiotemporal regulation of protein phosphorylation in cells and tissues is required for normal development and homeostasis. We present the protocol ‘In Gel Kinase Assay’, which is useful for protein kinase activity measurements from crude protein extracts. We have successfully used ‘In Gel Kinase Assay’ protocol to show that the Arabidopsis thaliana sextuple mutant in the PYRABACTIN RESISTANCE1/PYR1-LIKE/REGULATORY COMPONENTS OF ABA RECEPTORS (PYR/PYL/RCAR-ABA receptors; line pyr/pyl112458) is impaired in ABA-mediated activation of SnRK2.2, SnRK2.3 and OST1/SnRK2.6, as much as the triple mutant snrk2.2/2.3/2.6 (Gonzalez-Guzman et al., 2012).
Laser Scanning Confocal Microcopy for Arabidopsis Epidermal, Mesophyll, and Vascular Parenchyma Cells
Investigation of protein targeting to plastids in plants by confocal laser scanning microscopy (CLSM) can be complicated by numerous sources of artifact, ranging from misinterpretations from in vivo protein over-expression, false fluorescence in cells under stress, and organellar mis-identification. Our studies have focused on the plant-specific gene MSH1, which encodes a dual targeting protein that is regulated in its expression and resides within the nucleoid of a specialized plastid type (Virdi et al., 2016). Therefore, our methods have been optimized to study protein dual targeting to mitochondria and plastids, spatial and temporal regulation of protein expression, and sub-organellar localization, producing a protocol and set of experimental standards that others may find useful for such studies.
Surface Inoculation and Quantification of Pseudomonas syringae Population in the Arabidopsis Leaf Apoplast
Bacterial pathogens must enter the plant tissue in order to cause a successful infection. Foliar bacterial pathogens that are not able to directly penetrate the plant epidermis rely on wounds or natural openings to internalize leaves. This protocol describes a procedure to estimate the population size of Pseudomonas syringae in the leaf apoplast after surface inoculation of Arabidopsis rosettes.
Multiplexed GuideRNA-expression to Efficiently Mutagenize Multiple Loci in Arabidopsis by CRISPR-Cas9
Since the discovery of the CRISPR (clustered regularly interspaced short palindromic repeats)-associated protein (Cas) as an efficient tool for genome editing in plants (Li et al., 2013; Shan et al., 2013; Nekrasov et al., 2013), a large variety of applications, such as gene knock-out, knock-in or transcriptional regulation, has been published. So far, the generation of multiple mutants in plants involved tedious crossing or mutagenesis followed by time-consuming screening of huge populations and the use of the Cas9-system appeared a promising method to overcome these issues. We designed a binary vector that combines both the coding sequence of the codon optimized Streptococcus pyogenes Cas9 nuclease under the control of the Arabidopsis thaliana UBIQUITIN10 (UBQ10)-promoter and guide RNA (gRNA) expression cassettes driven by the A. thaliana U6-promoter for efficient multiplex editing in Arabidopsis (Yan et al., 2016). Here, we describe a step-by-step protocol to cost-efficiently generate the binary vector containing multiple gRNAs and the Cas9 nuclease based on classic cloning procedure.
Knock-in Blunt Ligation Utilizing CRISPR/Cas9
The incorporation of the CRISPR/Cas9 bacterial immune system into the genetic engineering toolbox has led to the development of several new methods for genome manipulation (Auer et al., 2014; Byrne et al., 2015). We took advantage of the ability of Cas9 to generate blunt-ended double-strand breaks (Jinek et al., 2012) to introduce exogenous DNA in a highly precise manner through the exploitation of non-homologous end-joining DNA repair machinery (Geisinger et al., 2016). This protocol has been successfully applied to traditional immortalized cell lines and human induced pluripotent stem cells. Here we present a generalized protocol for knock-in blunt ligation, using HEK293 cells as an example.
Direct Visualization and Quantification of the Actin Nucleation and Elongation Events in vitro by TIRF Microscopy
Total internal reflection fluorescence (TIRF) microscopy is a powerful tool for visualizing the dynamics of actin filaments at single-filament resolution in vitro. Thanks to the development of various fluorescent probes, we can easily monitor all kinds of events associated with actin dynamics, including nucleation, elongation, bundling, fragmentation and monomer dissociation. Here we present a detailed protocol regarding the visualization and quantification of actin nucleation and filament elongation events by TIRF microscopy in vitro, which is based on the methods previously reported (Liu et al., 2015; Yang et al., 2011).
Stem Cell
Isolation and Primary Culture of Adult Human Adipose-derived Stromal/Stem Cells
Adipose-derived stromal/stem cells (ASCs) are multipotent cells that can be isolated from adipose tissue. Studies have shown that cells have the capacity to self-renew and differentiate into adipocyte, chondrocyte, myocyte, and osteoblast lineages. Thus, significant interest regarding their use for regenerative purposes to restore aging or damaged tissue has grown in recent decades. These cells have also been shown to immunomodulate the microenvironment and secrete abundant growth factors, which minimize inflammation and aid repair and regeneration. ASCs can be readily isolated from the stromal vascular fraction (SVF) of lipoaspirates. Given their ease of accessibility, bountiful source, and potential application in regenerative medicine and tissue engineering, there is growing interest in the characterization and utilization of ASCs. This protocol describes the isolation of ASCs from adult human adipose tissue as well as methods for culture maintenance including expansion and cryopreservation.
Reprogram Murine Epiblast Stem Cells by Epigenetic Inhibitors
Pluripotent stem cells in the naïve state are highly useful in regenerative medicine and tissue engineering. A robust reprogramming of the primed murine Epiblast Stem Cells (EpiSCs) to naïve pluripotency is feasible via chemical-only approach. This protocol described a method to reprogram murine EpiSCs by MM-401 treatment, which blocks histone H3K4 methylation by MLL1/KMT2A.