Name: Author Spotlight: Comprehensive Epigenetic Analysis for Investigating Human Cellular Plasticity and Environmental Adaptation Using Immunofluorescence Assays
Uploaded: 2024-06-28T14:25:00
Description: Various nuclear processes, such as transcriptional control, occur within discrete structures known as foci that are discernable through the ...

We acknowledge the scientific and technical assistance of the INGM Imaging Facility, in particular, C. Cordiglieri and A. Fasciani, and the INGM FACS sorting facility in particular M.C Crosti (Istituto Nazionale di Genetica Molecolare &#39;Romeo ed Enrica Invernizzi&#39; (INGM), Milan, Italy). We acknowledge M. Giannaccari for his technical informatic support. This work was funded by the following grants: Fondazione Cariplo (Bando Giovani, grant nr 2018-0321) and Fondazione AIRC (grant nr MFAG 29165) to F.M. Ricerca Finalizzata, (grant nr GR-2018-12365280), Fondazione AIRC (grant nr 2022 27066), Fondazione Cariplo (grant nr 2019-3416), Fondazione Regionale per la Ricerca Biomedica (FRRB CP2_12/2018,) Piano Nazionale di Ripresa e Resilienza (PNRR) (grant nr G43C22002620007) and Progetti di Rilevante Interesse Nazionale (PRIN) (grant nr 2022PKF9S) to B.B.

The use of human samples for research purposes was approved by the Ethics Committees of the Fondazione Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) C&#224; Granda Ospedale Maggiore Policlinico (Milan), and informed consent was obtained from all subjects (authorization numbers: 708_2020). The protocol is organized into three primary sections: immunofluorescence execution, image acquisition, and image analysis. On average, it necessitates 4 working days to be completed (Figure 1...

Analysis Workflow of Nuclear Protein Staining in Human Primary Cells

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In this study, we present a method for performing immunofluorescence experiments on nuclear proteins in human T lymphocytes. This method offers flexibility for use with various cell types through minor modifications in fixation and permeabilization steps, as described previously30,31. 
Our imaging workflow builds upon established techniques outlined in the literature, specifically FindFoci and 3D Suite22,</...

The organization of the eukaryotic genome is governed by multiple layers of epigenetic modifications1, coordinating several nuclear functions that can occur within specialized compartments called nuclear bodies or condensates2. Within these structures, processes such as transcription initiation3, RNA processing4,5,6, DNA repair7,8, ribosome biogenesis9,10,11, and heterochromatin regulation12,13 take place. The regulation of nuclear bodies adjusts over both spatial and temporal dimensions to accommodate cellular requirements, guided by principles of phase separation14,15. Consequently, these bodies function as transient factories where functional components assemble and disassemble, undergoing changes in size and spatial distribution. Hence, understanding the characteristics of nuclear proteins by microscopy, including their propensity to form bodies and their spatial arrangement in different cellular conditions, offers valuable insights into their functional roles. Fluorescence microscopy is a widely used method for studying nuclear proteins, allowing their detection through fluorescent antibodies or directly expressing targets with a fluorescent protein reporter16,17.
In this context, nuclear bodies appear as bright foci or puncta, with a notable degree of sphericity, making them easily distinguishable from the surrounding environment16,18. Super-resolution techniques like STORM and PALM, by providing improved resolution (up to 10 nm)19, enable more precise characterization of the structure and composition of specific condensates20. However, their accessibility is limited by equipment expenses and the specialized skills needed for data analysis. Therefore, confocal microscopy remains popular due to its favorable balance between resolution and wider usage. Such popularity is facilitated by the inherent removal of out-of-focus light, which diminishes the requirement for extensive post-processing procedures for accurate segmentation, its widespread availability in research institutes, its effective acquisition time, and sample preparation that is typically efficient. However, accurately measuring protein distribution, assembly, or diffusion using immunofluorescence assays across diverse cellular conditions poses challenges, as many existing methods lack guidance on selecting suitable parameters for proteins with varying distribution patterns21. Moreover, handling the resulting large data volume can be daunting for users with limited experience in data analysis, potentially compromising the biological significance of the results.
To address these challenges, we introduce a detailed step-by-step protocol for immunofluorescence preparation and data analysis, aiming to provide an unbiased method for quantifying protein staining with various organization patterns (Figure 1). This semi-automated pipeline is designed for users with limited expertise in computational and imaging analysis. It combines the functionalities of two established Fiji plugins: FindFoci22 and 3D suite23. By integrating the precise foci identification capability of FindFoci with the object identification and segmentation features in 3D space offered by 3D suite, our approach generates two CSV files per channel for each field of acquisition. These files contain complementary information that facilitates the calculation of metrics suitable for various types of signal distribution, such as the count of foci per cell, the distance of foci from the nuclear centroid, and the inhomogeneity coefficient (IC), which we have introduced for diffuse protein staining. In addition, we acknowledge that data extrapolation can be time-consuming for users with limited data handling skills. To streamline this process, we provide a Python script that automatically compiles all collected measurements into a single file for each experiment. Users can execute this script without the need to install any programming language software. We provide an executable code on Google Colab, a cloud-based platform that allows the writing of Python scripts directly in the browser. This ensures that our method is intuitive and readily accessible for immediate use.
We demonstrate the effectiveness of our protocol in analyzing and quantifying alterations in signal distribution of two nuclear proteins: Bromodomain-containing protein 4 (BRD4) and Suppressor of zeste-12 (SUZ12). BRD4 is a well-documented coactivator protein within the Mediator complex known to form condensates associated with polymerase II-dependent transcriptional initiation24,25. SUZ12 is a protein component of the Polycomb Repressive Complex 2 (PRC2) responsible for regulating the deposition of H3K27me3 histone modification26,27. These proteins exhibit different patterns within two distinct cell types: freshly isolated human CD4+ na&#239;ve T cells, which are quiescent and exhibit slow rates of transcriptional activity, and in vitro differentiated TH1 CD4+ cells, which are specialized, proliferating effector cells showing increased transcription28.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1.5 mL Safe-Lock Tubes</td>
			<td>Eppendord</td>
			<td>#0030121503</td>
			<td>Protocol section 1</td>
		</tr>
		<tr>
			<td>10 mL Serological pipettes</td>
			<td>VWR</td>
			<td>#612-3700</td>
			<td>Protocol section 1</td>
		</tr>
		<tr>
			<td>20 &#181;L barrier pipette tip</td>
			<td>Thermo Scientific</td>
			<td>#2149P-HR</td>
			<td>Protocol section 1</td>
		</tr>
		<tr>
			<td>50 mL Polypropylene Conical Tube</td>
			<td>Falcon</td>
			<td>#352070</td>
			<td>Protocol section 1</td>
		</tr>
		<tr>
			<td>200 &#181;L barrier pipette tip</td>
			<td>Thermo Scientific</td>
			<td>#2069-HR</td>
			<td>Protocol section 1</td>
		</tr>
		<tr>
			<td>antifade solution - ProlongGlass - mountingmedia</td>
			<td>Invitrogen</td>
			<td>#P36984</td>
			<td>Step 1.3.12</td>
		</tr>
		<tr>
			<td>BSA (Bovine Serum Albumin)</td>
			<td>Sigma</td>
			<td>#A7030</td>
			<td>Step 1.3.6., 1.3.8.</td>
		</tr>
		<tr>
			<td>CD4+ T Cell Isolation Kit</td>
			<td>Miltenyi Biotec</td>
			<td>#130-096-533</td>
			<td>Step 1.1.2.</td>
		</tr>
		<tr>
			<td>DAPI (4,6-diamidino-2-phenylindole)</td>
			<td>Invitrogen</td>
			<td>Cat#D1306</td>
			<td>Step 1.3.10.</td>
		</tr>
		<tr>
			<td>Dry ice</td>
			<td></td>
			<td></td>
			<td>Step 1.3.1.</td>
		</tr>
		<tr>
			<td>Dynabeads Human T-activator anti-CD3/anti-CD28 bead</td>
			<td>Life Technologies</td>
			<td>#1131D</td>
			<td>magnetic beads step 1.1.4.</td>
		</tr>
		<tr>
			<td>EtOH</td>
			<td>Carlo Erba</td>
			<td>#4146320</td>
			<td>Step 1.2.1.1.</td>
		</tr>
		<tr>
			<td>FACSAria SORP</td>
			<td>BD Bioscences</td>
			<td></td>
			<td>Step 1.1.3. Equipped with BD FACSDiva Software version 8.0.3</td>
		</tr>
		<tr>
			<td>FBS (Fetal Bovine Serum)</td>
			<td>Life Technologies</td>
			<td>#10270106</td>
			<td>Step 1.1.4</td>
		</tr>
		<tr>
			<td>FICOLL PAQUE PLUS</td>
			<td>Euroclone</td>
			<td>GEH17144003F32</td>
			<td>Step 1.1.1.</td>
		</tr>
		<tr>
			<td>FIJI Version 2.14.0</td>
			<td>-</td>
			<td>-</td>
			<td>Protocol section 3</td>
		</tr>
		<tr>
			<td>Glass coverslip (10 mm, thickness 1.5 H)</td>
			<td>Electron Microscopy Sciences</td>
			<td>#72298-13</td>
			<td>Step 1.2.1.</td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Sigma</td>
			<td>#G5516</td>
			<td>Step 1.2.7-1.3.1.</td>
		</tr>
		<tr>
			<td>Goat anti-Rabbit AF568 secondary antibody</td>
			<td>Invitrogen</td>
			<td>A11036</td>
			<td>Step 1.3.8.</td>
		</tr>
		<tr>
			<td>HCl</td>
			<td>Sigma</td>
			<td>#320331</td>
			<td>Step 1.3.4.</td>
		</tr>
		<tr>
			<td>human neutralizing anti-IL-4</td>
			<td>Miltenyi Biotec</td>
			<td>Cat#130-095-753</td>
			<td>Step 1.1.4.</td>
		</tr>
		<tr>
			<td>human recombinant IL-12</td>
			<td>Miltenyi Biotec</td>
			<td>Cat#130-096-704</td>
			<td>Step 1.1.4.</td>
		</tr>
		<tr>
			<td>human recombinant IL-2</td>
			<td>Miltenyi Biotec</td>
			<td>Cat#130-097-744</td>
			<td>Step 1.1.4.</td>
		</tr>
		<tr>
			<td>Leica TCS SP5 Confocal microscope</td>
			<td>Leica Microsystems</td>
			<td>-</td>
			<td>Protocol section 2, Equipped with HCX PL APO 63x, 1.40 NA oil immersion objective, with an additional 3x zoom. Pinhole size : 0.8 AU. Line average 2&#215;. Frame size 1024&#215;1024 pixel.</td>
		</tr>
		<tr>
			<td>MEM Non-Essential Amino Acids Solution</td>
			<td>Life Technologies</td>
			<td>#11140035</td>
			<td>Step 1.1.4.</td>
		</tr>
		<tr>
			<td>Microscope Slides</td>
			<td>VWR</td>
			<td>#631-1552</td>
			<td>Step 1.3.12.</td>
		</tr>
		<tr>
			<td>Mouse monoclonal anti-Human CD4 APC-Cy7 (RPA-T4 clone)</td>
			<td>BD Bioscience</td>
			<td>#557871</td>
			<td>Step 1.1.3.</td>
		</tr>
		<tr>
			<td>Mouse monoclonal anti-Human CD45RA PECy5 (5H9 clone)</td>
			<td>BD Bioscience</td>
			<td>#552888</td>
			<td>Step 1.1.3.</td>
		</tr>
		<tr>
			<td>Mouse monoclonal anti-Human CD45RO APC (UCHL1 clone)</td>
			<td>Miltenyi Biotec</td>
			<td>#130-113-546</td>
			<td>Step 1.1.3.</td>
		</tr>
		<tr>
			<td>Multiwell 24 well</td>
			<td>Falcon</td>
			<td>#353047</td>
			<td>Protocol section 1</td>
		</tr>
		<tr>
			<td>Normal Goat Serum</td>
			<td>Invitrogen</td>
			<td>PCN5000</td>
			<td>Step 1.3.6., 1.3.8.</td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Life Technologies</td>
			<td>#14190094</td>
			<td>Protocol section 1</td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin solution</td>
			<td>Life Technologies</td>
			<td>#15070063</td>
			<td>Step 1.1.4.</td>
		</tr>
		<tr>
			<td>PFA</td>
			<td>Sigma</td>
			<td>#P6148</td>
			<td>Step 1.2.4.</td>
		</tr>
		<tr>
			<td>poly-L-lysine</td>
			<td>Sigma</td>
			<td>#P8920</td>
			<td>1.2.1.</td>
		</tr>
		<tr>
			<td>Primary antibody - BRD4</td>
			<td>Abcam</td>
			<td>#ab128874</td>
			<td>Step 1.3.6.</td>
		</tr>
		<tr>
			<td>Primary antibody - SUZ12</td>
			<td>Cel Signalling</td>
			<td>mAb #3737</td>
			<td>Step 1.3.6.</td>
		</tr>
		<tr>
			<td>RPMI 1640 W/GLUTAMAX-I</td>
			<td>Life Technologies</td>
			<td>#61870010</td>
			<td>Step 1.1.4.</td>
		</tr>
		<tr>
			<td>Sodium Pyruvate</td>
			<td>Life Technologies</td>
			<td>#11360039</td>
			<td>Step 1.1.4.</td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Sigma</td>
			<td>#T8787</td>
			<td>Step 1.2., 1.3.</td>
		</tr>
		<tr>
			<td>TWEEN 20</td>
			<td>Sigma</td>
			<td>#P9416</td>
			<td>Step 1.3.</td>
		</tr>
		<tr>
			<td>Tweezers</td>
			<td>-</td>
			<td>-</td>
			<td>Protocol section 1</td>
		</tr>
	</tbody>
</table>

a versatile pipeline for analyzing dynamic changes in nuclear bodies in a variety of cell types

Various nuclear processes, such as transcriptional control, occur within discrete structures known as foci that are discernable through the immunofluorescence technique. Investigating the dynamics of these foci under diverse cellular conditions via microscopy yields valuable insights into the molecular mechanisms governing cellular identity and functions. However, performing immunofluorescence assays across different cell types and assessing alterations in the assembly, diffusion, and distribution of these foci present numerous challenges. These challenges encompass complexities in sample preparation, determination of parameters for analyzing imaging data, and management of substantial data volumes. Moreover, existing imaging workflows are often tailored for proficient users, thereby limiting accessibility to a broader audience.
In this study, we introduce an optimized immunofluorescence protocol tailored for investigating nuclear proteins in different human primary T cell types that can be customized for any protein of interest and cell type. Furthermore, we present a method for unbiasedly quantifying protein staining, whether they form distinct foci or exhibit a diffuse nuclear distribution.
Our proposed method offers a comprehensive guide, from cellular staining to analysis, leveraging a semi-automated pipeline developed in Jython and executable in Fiji. Furthermore, we provide a user-friendly Python script to streamline data management, publicly accessible on a Google Colab notebook. Our approach has demonstrated efficacy in yielding highly informative immunofluorescence analyses for proteins with diverse patterns of nuclear organization across different&#160;contexts.

Author Spotlight: Comprehensive Epigenetic Analysis for Investigating Human Cellular Plasticity and Environmental Adaptation Using Immunofluorescence Assays

A Versatile Pipeline for Analyzing Dynamic Changes in Nuclear Bodies in a Variety of Cell Types

Our main research interest is an epigenetic mechanism that regulates human cellular elasticity and environmental adaptation. I am currently focusing on studying how changes in chromatization within a nuclear condensate three pathological cellular conditions. I believe that studying the biophysical properties of chromatization opens a new field and offers unique opportunities for developing novel therapeutic approaches.Immunofluorescence assays are valuable for screening protein organization in nuclear condensates. However, human genetics can be challenging due to parameter selection issues and large data volume when studying multiple conditions. We offer a comprehensive with guidance on how to use the right parameters and automated analysis pipeline to streamline the process.Our protocol guides user from sample preparation to the analysis. We provided a simulated pipeline design through Doza with limited computation and image analysis expertise. The workflow is accessible to everyone at no cost, and leveraging widely adoptable software like Imogene and Python and the free cloud based service Google Colab.

The outlined protocol in this method facilitates the visualization and quantification of alterations in nuclear protein staining within human primary T cells, and it can be customized for diverse cell types and protein targets. As case studies, we conducted and analyzed the staining of BRD4 and SUZ12 in na&#239;ve and TH1 CD4+ cells.
BRD4 displays a well-dotted staining pattern in both quiescent na&#239;ve and differentiated TH1 CD4+...

This method describes an immunofluorescence protocol and quantification pipeline for evaluating protein distribution with varied nuclear organization patterns in human T lymphocytes. This protocol provides step-by-step guidance, starting from sample preparation and continuing through the execution of semi-automated analysis in Fiji, concluding with data handling by a Google Colab notebook.

Various nuclear processes, such as transcriptional control, occur within discrete structures known as foci that are discernable through the ...

a-versatile-pipeline-for-analyzing-dynamic-changes-nuclear-bodies

Research

JoVE Journal

Genetics

Quantification Pipeline for Evaluating Protein Distribution with Varied Nuclear Organization Patterns in Human T Lymphocytes

To begin, download and install the latest version of Fiji on a computer. After downloading the convert_to_TIFF. py script, drag and drop the script on Fiji and run the code.Browse to the path where the experiment is stored. The converted TIFF files are created within the same experimental folder. Click on plugins, then 3D Suite, and open the 3D manager options.Within the 3D manager window, select the check boxes corresponding to the volume in unit, mean gray value, bounding box in pixel, standard deviation gray value, centroid in pixel, and centroid in unit. Tick the exclude objects on edges XY, and exclude objects on edges Z.Then, click okay. Open the fluorescent image of human T-lymphocytes.Click Control Shift D to duplicate the protein channel, including the stack. Check the hyper stack checkbox. Specify the appropriate channel number within the channels box and rename it accordingly.To launch the Fiji macro recorder, navigate to the plugins, then macros, and select record. Then, to open the FindFoci plugin, sequentially click on plugins GDSC, FindFoci, and FindFoci GUI. From the image dropdown menu, select the image to be analyzed.Set the Gaussian blur to 1.5, background method to standard deviation above mean, background parameter to nine, search method to fraction of peak background, search parameter to 0.7, peak method to relative above background, peak parameter to 0.2, and minimum size to five. Set the max peaks to high numbers to include all foci in the image. To enhance foci identification, adjust the Gaussian blur close to the foci diameter, and increase the values of the background parameter to impose more stringent thresholds.Then, decrease the values of the search parameter to include areas farther away from the fluorescence peak and decrease the values of the peak parameter for the separation of peaks. Run FindFoci and copy the string that appears in the recorder window. The string contains the selected parameters, excluding the quotation marks.After downloading the nuclear_prod_q. py script, drag and drop the script on Fiji, and click run to execute the code. In the nucleus channel, enter the number corresponding to the channel of DAPI.For nucleus Gaussian blur, enter the value of sigma needed to blur the image for segmentation. Then, enter the number corresponding to the channel of the staining of interest for the protein channel. In the FindFoci parameter, paste the string representing the macro recording of the selected parameters.Tick the visual check box and click browse to select the directory where the images are stored. Once all boxes are compiled, click okay to continue the execution. From the ROI list in the ROI manager 3D window, select the nuclei channel, and click live ROI to on.Select the ROI belonging to the same nucleus and press merge. And for undesired nuclei, press delete. Again, click live ROI to on, select all, and confirm that all nuclei are correctly segmented.From the quantification folder, open the TXT file with records of the parameters used for the analysis. Open Google Colab in a browser. Then, from the file, select open notebook, and upload the final nuclear protein metrics.ipynb script. Upload all the folders containing the CSV files of each image field into a folder of preference in Google Drive. In the notebook, indicate the path of the folder where the results sub-folders are stored and run all cells.When the code has finished compiling, open the final spreadsheet file containing all the compiled data.