Reviewer
Laura Molina-García
  • Research Associate, University College London
Research fields
  • Microbiology
Protocol to Induce Follicular T Helper Cells, Germinal Centers, and Skin Lesions in Mouse Models for Skin Blistering Diseases

Autoreactive T cells in autoantibody-mediated autoimmune diseases can be divided into two major subsets: (i) follicular T helper cells (Tfh) that provide T cell help in germinal centers (GC) and (ii) effector T (Teff) cells that immigrate into peripheral tissue sites such as the skin and mediate local inflammation. To study the sequence of events leading to the loss of tolerance in autoantibody-mediated autoimmune diseases it is required to investigate both T cell subsets simultaneously. This approach is hampered mainly because the appearance of skin inflammation in mouse models is a random process, which makes it difficult to define the location of inflammation at the right time point. To overcome this problem, we developed a scratching technique for ear skins that leads to the establishment of chronic autoimmune wounds in the mouse model for the pemphigoid-like disease epidermolysis bullosa acquisita. By defining the exact place where the skin wounds should form, this protocol enables a detailed analysis of skin-immigrating Teff cells. Of note, this protocol induces GC in draining lymph nodes in parallel so that Tfh cells in GC can be investigated concurrently. This protocol is not restricted to T cells and can be used for any other skin-immigrating inflammatory cells.

A Gel-Based Assay for Probing Protein Translocation on dsDNA
Authors:  Christiane Brugger and Alexandra M. Deaconescu, date: 07/20/2021, view: 2855, Q&A: 0

Protein translocation on DNA represents the key biochemical activity of ssDNA translocases (aka helicases) and dsDNA translocases such as chromatin remodelers. Translocation depends on DNA binding but is a distinct process as it typically involves multiple DNA binding states, which are usually dependent on nucleotide binding/hydrolysis and are characterized by different affinities for the DNA. Several translocation assays have been described to distinguish between these two modes of action, simple binding as opposed to directional movement on dsDNA. Perhaps the most widely used is the triplex-forming oligonucleotide displacement assay. Traditionally, this assay relies on the formation of a DNA triplex from a dsDNA segment and a short radioactively labeled oligonucleotide. Upon translocation of the protein of interest along the DNA substrate, the third DNA strand is destabilized and eventually released off the DNA duplex. This process can be visualized and quantitated by polyacrylamide electrophoresis. Here, we present an effective, sensitive, and convenient variation of this assay that utilizes a fluorescently labeled oligonucleotide, eliminating the need to radioactively label DNA. In short, our protocol provides a safe and user-friendly alternative.


Graphical abstract:



Figure 1. Schematic of the triplex-forming oligonucleotide displacement assay.


Preparation of Doublet Microtubule Fraction for Single Particle Cryo-electron Microscopy
Authors:  Corbin Black, Daniel Chen Dai, Katya Peri, Muneyoshi Ichikawa and Khanh Huy Bui, date: 06/05/2021, view: 3226, Q&A: 0

Over the years, studying the ultrastructure of the eukaryotic cilia/flagella using electron microscopy (EM) has contributed significantly toward our understanding of ciliary function. Major complexes in the cilia, such as inner and outer dynein arms, radial spokes, and dynein regulatory complexes, were originally discovered by EM. Classical resin-embedding EM or cryo-electron tomography can be performed directly on the isolated cilia or in some cases, cilia directly attached to the cell body. Recently, single particle cryo-EM has emerged as a powerful structural technique to elucidate high-resolution structures of macromolecular complexes; however, single particle cryo-EM requires non-overlapping complexes, i.e., the doublet microtubule of the cilia. Here, we present a protocol to separate the doublet microtubule from the isolated cilia bundle of two species, Tetrahymena thermophila and Chlamydomonas reinhardtii, using ATP reactivation and sonication. Our approach produces good distribution and random orientation of the doublet microtubule fragments, which is suitable for single particle cryo-EM analysis.

Antibiotic Disc Assay for Synechocystis sp. PCC6803
Authors:  Otilia Cheregi and Christiane Funk, date: 12/20/2016, view: 10173, Q&A: 0
This protocol describes how to investigate the integrity of the outer cell wall in the cyanobacterium Synechocystis sp. PCC6803 using antibiotics. It is adapted to the agar diffusion test (Bauer et al., 1966), in which filter paper discs impregnated with specified concentrations of antibiotics were placed on agar plates inoculated with bacteria. The antibiotics we tested, interfering with the biosynthesis/function of bacterial cell walls, will diffuse into the agar and produce a zone of cyanobacterial growth inhibition around the disc(s). The size of the inhibition zone reflects the sensitivity of the strain to the action of antibiotics, e.g., a mutation in a protein functioning within the cell wall or its construction would render the mutant strain more sensitive to the respective antibiotic. The method has proven to be useful for phenotyping a mutant of Synechocystis sp. PCC6803 lacking all three genes encoding Deg proteases. Deletion of these ATP-independent serine proteases was shown to have impact on the outer cell layers of Synechocystis cells (Cheregi et al., 2015).
Methods for Detecting Microbial Methane Production and Consumption by Gas Chromatography
Authors:  Jared T. Aldridge, Jennie L. Catlett, Megan L. Smith and Nicole R. Buan, date: 04/05/2016, view: 10260, Q&A: 0
Methane is an energy-dense fuel but is also a greenhouse gas 25 times more detrimental to the environment than CO2. Methane can be produced abiotically by serpentinization, chemically by Sabatier or Fisher-Tropsh chemistry, or biotically by microbes (Berndt et al., 1996; Horita and Berndt, 1999; Dry, 2002; Wolfe, 1982; Thauer, 1998; Metcalf et al., 2002). Methanogens are anaerobic archaea that grow by producing methane gas as a metabolic byproduct (Wolfe, 1982; Thauer, 1998). Our lab has developed and optimized three different gas chromatograph-utilizing assays to characterize methanogen metabolism (Catlett et al., 2015). Here we describe the end point and kinetic assays that can be used to measure methane production by methanogens or methane consumption by methanotrophic microbes. The protocols can be used for measuring methane production or consumption by microbial pure cultures or by enrichment cultures.
Product Analysis of Starch Active Enzymes by TLC
Authors:  Darrell Cockburn and Nicole Koropatkin, date: 10/20/2015, view: 12902, Q&A: 1
Thin layer chromatography (TLC) is a useful technique for detecting the presence of monosaccharides through to oligosaccharides, though it needs to be optimized for the specific sugars that are analyzed. Here we present a method for visualizing the reaction product(s) of starch active enzymes, which can contain α-1, 4 linked and α-1, 6 linked glucose. This was first published in Molecular Microbiology (Cockburn et al., 2015). The TLC protocol is an adapted version of that published by Robyt and Mukerjea (Robyt and Mukerjea, 1994). For a summary of the products generated by starch active enzymes see the review by Hii et al. (2012).
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