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Past Issue in 2016
Volume: 6, Issue: 12
Biochemistry
Extraction and Profiling of Plant Polar Glycerol Lipids
This protocol describes a method to extract total polar glycerol lipids from plant materials, followed by mass spectrometry profiling. Different glycerol lipid classes can be distinguished by their head-groups, which can be profiled automatically and quantitatively by a triple quadrupole mass spectrometry in multiple reaction monitoring (MRM) mode with an autosampler. Comparing with other established methods, such as thin layer chromatography (TLC) separation followed by Gas spectrometry (GC) analysis, this method requires little effort in sample preparation and separation, while the resolution is not limited to general lipid classes but at side chain level. This method was described and used successfully to profile plant lipids changes under freezing stress in Welti et al. (2002).
Positional Analysis of Fatty Acids in Phospholipids by PLA2 Treatment
Plant phospholipids can be produced in the endoplasmic reticulum or plastids. Lipids from different sources can be distinguished by the fatty acid profile, in terms of the preferred fatty acid species esterified to the sn-1 or sn-2 position of the glycerol backbone (Ohlrogge and Browse, 1995). This protocol is used to determine the fatty acid profile in total plant phospholipids by the treatment of sn-2 specific phospholipase A2 (PLA2).
Cell Biology
Protocol for Microfluidic System to Automate the Preparation and Fractionation of the Nucleic Acids in the Cytoplasm Versus Nuclei of Single Cells
This protocol describes the extraction, fractionation, and recovery of cytoplasmic nucleic acids (e.g., cytoplasmic RNA) versus nucleic acids in the cell nucleus (including genomic DNA, gDNA) from single cells with a microfluidic system. The method enables independent, sequence-specific analyses of these critical markers (Kuriyama et al., 2015). The system uses a microfluidic chip with a simple geometry and four end-channel electrodes, and completes the entire process in less than 5 min, including lysis, purification, fractionation, and delivery to two output reservoirs: One for the nucleus (including gDNA and nuclear RNA) and one for cytoplasmic RNA. Each reservoir then contains high quality and purity aliquots with no measurable cross-contamination of cytoplasmic RNA versus nucleic acids in nucleus. As described here, our protocol focuses on the analysis of cytoplasmic RNA versus gDNA from the nucleus. We have tested this protocol with mouse and human cells but not with walled cells such as plant cells.
Immunology
Isolation and Culture of the Islets of Langerhans from Mouse Pancreas
The islets of Langerhans are clusters of endocrine cells located within the pancreas. Insulin-producing beta cells are the major cell type within islets, with glucagon-producing alpha cells and somatostatin-producing delta cells the other major cell types. The beta cells are the target of immune-mediated destruction in type 1 diabetes (Graham et al., 2012). Failure of beta cell function accompanied by loss of beta cell mass is also a feature of type 2 diabetes (Wali et al., 2013). Therefore studying the biology of pancreatic islets is important to understand the pathogenesis of diabetes and to develop new therapies. Here we describe the isolation of mouse islets. This requires gentle enzymatic and mechanical digestion of the exocrine tissue and density gradient separation (Chong et al., 2004; Liu and Shapiro, 1995; Thomas et al., 1998). We then describe how islets can be cultured whole or dispersed into single cells for use in a variety of in vitro and in vivo analyses. Using this protocol reliably results in the isolation of 200-400 islets, depending on the strain of mouse.
In vivo OVA-specific Cytotoxic CD8+ T Cell Killing Assay
Cytotoxic CD8+ T cells are responsible for the lysis of cells expressing peptides associated with MHC class I molecules and derived from infection with a pathogen or from mutated antigens. In order to quantify in vivo this antigen-specific CD8+ T cell killing activity, we use the in vivo killing assay (IVK). Here we describe the protocol for the lysis of cells expressing a CD8+ T cell epitope of the OVA protein (SIINFEKL). Mice are previously immunized with the OVA protein and 7 days after immunization, they receive a mix of target cells, prepared from naive C57BL/6 spleen cells pulsed with the SIINFEKL peptide and labeled with high level of CFSE and of non-pulsed control cells labeled with low level of CFSE. One day later, the spleen cells of recipient mice are isolated and analyzed by FACS to measure the amount of CFSEhigh cells and CFSElow cells. The percentage of lysis is calculated by the difference between CFSE high versus low in immunized vs non-immunized mice.Measuring the ability of antigen-specific CD8+ T cell to lyse their antigen in vivo is very important to evaluate the adaptive cytotoxic response induced against a pathogen or a tumor antigen.
Measurement of Mitochondrial DNA Release in Response to ER Stress
Mitochondria house the metabolic machinery for cellular ATP production. The mitochondrial network is sensitive to perturbations (e.g., oxidative stress and pathogen invasion) that can alter membrane potential, thereby compromising function. Healthy mitochondria maintain high membrane potential due to oxidative phosphorylation (Ly et al., 2003). Changes in mitochondrial function or calcium levels can cause depolarization, or a sharp decrease in mitochondrial membrane potential (Bernardi, 2013). Mitochondrial depolarization induces opening of the mitochondrial permeability transition pore (MPTP), which allows release of mitochondrial components like reactive oxygen species (mtROS), mitochondrial DNA (mtDNA) or intermembrane space proteins into the cytosol (Martinou and Green, 2001; Tait and Green, 2010; Bronner and O'Riordan, 2014). These contents trigger inflammation, and can lead to cell death (West et al., 2011). Both mtROS and cytosolic mtDNA contribute to the activation of inflammasomes, multiprotein complexes that process the proinflammatory cytokines, IL-18 and IL-1β. Studies indicate that cytosolic mtDNA in particular can bind two different inflammasome sensors, AIM2 and NLRP3, leading to inflammasome activation (Burckstummer et al., 2009; Hornung and Latz, 2010). In this protocol, you will be able to specifically extract cytosolic mtDNA and quantify the amount using a qPCR assay. Figure 1. Flowchart for extracting, purifying, and amplifying cytosolic mtDNA
Whole-mount Enteroid Proliferation Staining
Small intestinal organoids, otherwise known as enteroids, have become an increasingly utilized model for intestinal biology in vitro as they recapitulate the various epithelial cells within the intestinal crypt (Mahe et al., 2013; Sato et al., 2009). Assessment of growth dynamics within these cultures is an important step to understanding how alterations in gene expression, treatment with protective and toxic agents, and genetic mutations alter properties essential for crypt growth and survival as well as the stem cell properties of the individual cells within the crypt. This protocol describes a method of visualization of proliferating cells within the crypt in three dimensions (Barrett et al., 2015). Whole-mount proliferation staining of enteroids using EdU incorporation enables the researcher to view all proliferating cells within the enteroid as opposed to obtaining growth information in thin slices as would be seen with embedding and sectioning, ensuring a true representation of proliferation from the stem cell compartment to the terminally differentiated cells of the crypt.
Efficient Isolation of Influenza Specific CTLs
Human antigen-specific CD8+ T-cell clones are valuable tools for dissecting CD8+ T-cell responses against antigens derived from infectious agents, cancer and self antigens. Here we describe a protocol for isolating human antigen-specific CD8+ T cells. This protocol uses surface capture of IFNγ to identify antigen responsive cells that are then cloned by single-cell sorting. Here we use CD8+ T-cell responses to influenza matrix protein (MP) as an example, but this approach can be applied to any antigen specificity.
Microbiology
Aspergillus terreus Infection of Fruits and Terrein Quantification by HPLC Analysis
The opportunistic fungal human and plant pathogen Aspergillus terreus (A. terreus) can be isolated from sea water, soil or decaying organic matter such as rotting leaves and fruits. While growing on fruits A. terreus produces secondary metabolites such as terrein, which may ease its penetration into plant tissues. In addition, biological activities of terrein may support competition against other microorganisms. In summary, terrein is a small polyketide that reduces germination of seedlings, induces lesions on fruit surfaces but also shows moderate antifungal activity. With this manuscript we provide a fruit infection protocol with Aspergillus terreus with subsequent determination of terrein production rates on infected fruits using an HPLC-based quantification approach.
Molecular Biology
Micro-chromatin Immunoprecipitation (μChIP) Protocol for Real-time PCR Analysis of a Limited Amount of Cells
Chromatin immunoprecipitation followed by deep sequencing (ChIP-Seq) is an important strategy to study gene regulation. When availability of cells is limited, however, it can be useful to focus on specific genes to investigate in depth the role of transcription factors or histone marks. Unfortunately, performing ChIP experiments to study transcription factors’ binding to DNA can be difficult when biological material is restricted. This protocol describes a robust method to perform μChIP for over-expressed or endogenous transcription factors using ~100,000 cells per ChIP experiment (Masserdotti et al., 2015). We also describe optimization steps, which we think are critical for this protocol to work and which can be used to further reduce the number of cells.
Plant Science
Root-knot Nematode Penetration and Sclareol Nematicidal Activity Assays
Plant parasitic nematodes parasitize roots and/or stems of various plants thereby inhibiting absorption of nutrients and moisture. In particular, root-knot nematodes (RKN) are a group of the most devastating pests. Various techniques, such as soil sterilization, cultivation of resistant crops, and chemical application, have been developed to control damage caused by RKN. Among these techniques, diminish by chemicals that induce or activate host defense to RKN is an attractive method because of its potential to reduce the environmental burden caused by crop protection. Sclareol, a diterpene, was identified as a chemical that induces resistance to RKN (Fujimoto et al., 2015). Here we provide a protocol for assessing the impact of sclareol on the penetration of RKNs into tomato and Arabidopsis roots and the direct nematicidal impact of the chemical on nematodes. This protocol can be used for other nematode resistance-inducing chemicals.
Quantifying Auxin Metabolites in Young Root Tissue of Medicago truncatula by Liquid Chromatography Electrospray-ionisation Quadrupole Time-of-flight (LC-ESI-QTOF) Tandem Mass Spectrometry
Auxins represent a major group of phytohormones controlling plant development. The spatio-temporal regulation of auxin gradients is essential for the initiation, growth and correct development of plant organs. Because auxins and their metabolites occur at trace levels in plant tissue, experiments requiring identification plus their selective and specific quantification can be most conveniently achieved using mass spectrometry (MS) and the associated chromatographic methods. With the advent of appropriate liquid-based ionisation techniques, emphasis has moved from the use of gas chromatography as the sample interface to the MS (GC/MS), with its concomitant need for derivatisation, to the more sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS). We describe an optimized liquid chromatography electrospray-ionisation quadrupole time-of-flight (LC-ESI-QTOF) methodology for the quantification of auxins. While the solvent extraction of young Medicago truncatula (M. truncatula) roots, as described herein, is relatively straightforward, older, woody or oily plant tissues may also be analyzed with appropriate modification to remove interferences and/or enhance extraction efficiency. In our hands, the analytical assay has proved sufficiently sensitive for the quantification of auxins to investigate their roles in various organogenic events, such as root nodulation in M. truncatula. Further increases in sensitivity can be expected with the use of the latest generation of instruments.
Measuring Auxin Transport Capacity in Seedling Roots of Medicago truncatula
Measurement of auxin transport capacity provides quantitative data on the physiological machinery involved in auxin transport within plants. This technique is easy to perform and gives quick results. Radiolabelled auxin (indole-3-acetic-acid) is fed into the roots of Medicago truncatula via an agar block. The resulting radioactivity from radiolabelled auxin uptake in the roots is measured with a liquid scintillation counter. Here, we describe the measurement of auxin transport capacity around the nodulation susceptible zone in young seedling roots of M. truncatula in response to rhizobia inoculation. Similar assays could be adapted in other plant species and to answer other biological questions.
Cytology and Microscopy: Immunolocalization of Covalently Modified Histone Marks on Barley Mitotic Chromosomes
Barley is a diploid inbreeding crop with a genome of 5 GB organized into seven chromosomes. The relatively low chromosome number and their large size make barley an excellent model for chromosome cytogenetic studies of large genome cereal crops. Chromatin can be defined as euchromatin or heterochromatin. Euchromatin is gene-rich, less condensed, and transcriptionally active while the heterochromatin is gene-poor, remains highly condensed and has low transcriptional activity (Bartova et al., 2008; Sharakhov and Sharakhova, 2015). However, the mapping of nine Histone modifications has shown that this simple description is not accurate in barley. Instead, it has been shown that combinations of histones carrying different covalent modifications reveal 10 chromatin states partitioning barley chromosomes into three global environments (Baker et al., 2015). Briefly, in this protocol, barley roots (cv Morex) were collected, fixed in paraformaldehyde and squashed onto slides. Chromosome spreads were immunostained using antibodies against specific histone modifications, in particular H3K27me3, K3K27me1 and H3K9me2. We used confocal imaging to acquire stacked images and confirm the locations of these histone modifications on barley chromosomes.
Stem Cell
Pit Assay to Measure the Bone Resorptive Activity of Bone Marrow-derived Osteoclasts
Although it is possible to use a tartrate-resistant acid phosphatase (TRAP) stain to assist in identifying osteoclasts, a separate method is needed to determine the bone resorption activity of osteoclasts. Since osteoclasts leave “pits” after bone matrix resorption (Charles et al., 2014), it is possible to stain pits as a method of measuring osteoclast bone resorption activity. The pit assay protocol enables researchers to stain bony slices that were co-cultured with osteoclasts with toluidine blue in order to allow the visualization, capture, and analysis of osteoclast resorptive activity based on the number, size and depth of pits (Zhou et al., 2015). The pit assay protocol is separated into three sequential stages: Preparation of bone slices (1); preparation of osteoclast precursors (Ross et al., 2006; Teitelbaum et al., 2000) (2), and bone resorption pit assay (3).