This work was supported by Czech Science Foundation (GACR) (project number 16-07425S), by Charles University Grant Agency (GAUK) (project number 923116) and by institutional funding from the Institute of Molecular Genetics, Academy of Sciences of the Czech Republic (RVO 68378050).

All methods described here have been approved by the Expert Committee on the Welfare of Experimental Animals of the Institute of Molecular Genetics and by the Academy of Sciences of the Czech Republic.
1. Reagent Preparation
<ol>
	<li>Prepare the ammonium-chloride-potassium (ACK) buffer. Add 4.145 g of NH4Cl and 0.5 g of KHCO3 to 500 mL of ddH2O, then add 100 &#181;L of 0.5 M ethylenediaminetetraacetic acid (EDTA) and filter-sterilize.</li>
	<li>Prepare polye...

<ol>
	<li>Moghaddam, A. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Macrophage+plasticity,+polarization+and+function+in+health+and+disease.">Macrophage plasticity, polarization and function in health and disease.</a> Journal of Cellular Physiology. , (2018).</li><li>Qian, C., Cao, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dendritic+cells+in+the+regulation+of+immunity+and+inflammation.">Dendritic cells in the regulation of immunity and inflammation.</a> Seminars in Immunology. 35, 3-11 (2018).</li><li>Amulic, B., Cazalet, C., Hayes, G. L., Metzler, K. D., Zychlinsky, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophil+function:+from+mechanisms+to+disease.">Neutrophil function: from mechanisms to disease.</a> Annual Review of Immunology. 30, 459-489 (2012).</li><li>Kondo, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lymphoid+and+myeloid+lineage+commitment+in+multipotent+hematopoietic+progenitors.">Lymphoid and myeloid lineage commitment in multipotent hematopoietic progenitors.</a> Immunological Reviews. 238 (1), 37-46 (2010).</li><li>Andrews, T., Sullivan, K. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Infections+in+patients+with+inherited+defects+in+phagocytic+function.">Infections in patients with inherited defects in phagocytic function.</a> Clinical Microbiology Reviews. 16 (4), 597-621 (2003).</li><li>Wynn, T. A., Chawla, A., Pollard, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Macrophage+biology+in+development,+homeostasis+and+disease.">Macrophage biology in development, homeostasis and disease.</a> Nature. 496 (7446), 445-455 (2013).</li><li>Austin, P. E., McCulloch, E. A., Till, J. 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B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+advanced+culture+method+for+generating+large+quantities+of+highly+pure+dendritic+cells+from+mouse+bone+marrow.">An advanced culture method for generating large quantities of highly pure dendritic cells from mouse bone marrow.</a> Journal of Immunological Methods. 223 (1), 77-92 (1999).</li><li>Inaba, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generation+of+large+numbers+of+dendritic+cells+from+mouse+bone+marrow+cultures+supplemented+with+granulocyte/macrophage+colony-stimulating+factor.">Generation of large numbers of dendritic cells from mouse bone marrow cultures supplemented with granulocyte/macrophage colony-stimulating factor.</a> Journal of Experimental Medicine. 176 (6), 1693-1702 (1992).</li><li>Chamberlain, L. 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K., Costanzi, E., Haas, M., Verma, I. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+pCL+vector+system:+rapid+production+of+helper-free,+high-titer,+recombinant+retroviruses.">The pCL vector system: rapid production of helper-free, high-titer, recombinant retroviruses.</a> Journal of Virology. 70 (8), 5701-5705 (1996).</li><li>Janssen, E., Zhang, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adaptor+proteins+in+lymphocyte+activation.">Adaptor proteins in lymphocyte activation.</a> Current Opinion in Immunology. 15 (3), 269-276 (2003).</li><li>Ferguson, P. J., Laxer, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+discoveries+in+CRMO:+IL-1beta,+the+neutrophil,+and+the+microbiome+implicated+in+disease+pathogenesis+in+Pstpip2-deficient+mice.">New discoveries in CRMO: IL-1beta, the neutrophil, and the microbiome implicated in disease pathogenesis in Pstpip2-deficient mice.</a> Seminars in Immunopathology. 37 (4), 407-412 (2015).</li><li>Holleman, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+of+the+outcome+predictor+in+acute+leukemia+1+(OPAL1)+gene+is+not+an+independent+prognostic+factor+in+patients+treated+according+to+COALL+or+St+Jude+protocols.">Expression of the outcome predictor in acute leukemia 1 (OPAL1) gene is not an independent prognostic factor in patients treated according to COALL or St Jude protocols.</a> Blood. 108 (6), 1984-1990 (1984).</li><li>Zjablovskaja, P., Danek, P., Kardosova, M., Alberich-Jorda, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proliferation+and+Differentiation+of+Murine+Myeloid+Precursor+32D/G-CSF-R+Cells.">Proliferation and Differentiation of Murine Myeloid Precursor 32D/G-CSF-R Cells.</a> Journal of Visualized Experiments: JoVE. 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The authors have nothing to disclose.

The expression of protein of interest in target cells is a key step in many types of biological studies. Differentiated macrophages and dendritic cells are difficult to transfect by standard transfection and retroviral transduction techniques. Bypassing the transfection of these differentiated cells with retroviral transduction of bone marrow progenitors, followed by differentiation when they already carry the desired construct, is a critical step allowing the expression of ectopic cDNAs in these cell types. An example o...

Myeloid cells represent an indispensable part of our defense mechanisms against pathogens. They are able to rapidly eliminate microbes, as well as dying cells. In addition, they are also involved in regulating tissue development and repair and in maintaining homeostasis1,2,3. All myeloid cells differentiate from common myeloid progenitors in the bone marrow. Their differentiation into many functionally and morphologically distinct subsets is to a large extent controlled by cytokines and their various combinations4. The most intensively studied myeloid cell subsets include neutrophilic granulocytes, macrophages and dendritic cells. Defects in any of these populations lead to potentially life-threatening consequences and cause severe dysfunctions of the immune system in humans and mice1,2,3,5,6.
Unlike neutrophilic granulocytes, dendritic cells and macrophages are tissue resident cells and their abundance in immune organs is relatively low. As a result, the isolation and purification of primary dendritic cells and macrophages for experiments requiring a large number of these cells is expensive and often impossible. To solve this problem, protocols have been developed to obtain large amounts of homogenous macrophages or dendritic cells in vitro. These approaches are based on the differentiation of murine bone marrow cells in the presence of cytokines: macrophage colony-stimulating factor (M-CSF) for macrophages and granulocyte-macrophage colony-stimulating factor (GM-CSF) or Flt3 ligand for dendritic cells7,8,9,10,11,12. Cells generated by this method are commonly described in the literature as bone marrow derived macrophages (BMDMs) and bone marrow derived dendritic cells (BMDCs). They have more physiological properties in common with primary macrophages or dendritic cells than with corresponding cell lines. Another major advantage is the possibility of obtaining these cells form genetically modified mice13. Comparative studies between wild-type cells and cells derived from genetically modified mice are often critical for uncovering novel functions of genes or proteins of interest.
Analysis of subcellular localization of proteins in living cells requires the coupling of a fluorescent label to the protein of interest in vivo. This is most commonly achieved by expressing genetically encoded fusion construct composed of an analyzed protein coupled (often via a short linker) to a fluorescent protein (e.g., green fluorescent protein (GFP))14,15,16. The expression of fluorescently tagged proteins in dendritic cells or macrophages is challenging. These cells are generally difficult to transfect by standard transfection procedures and the efficiencies tend to be very low. Moreover, the transfection is transient, it generates cellular stress and achieved intensity of fluorescence might not be sufficient for microscopy17. In order to obtain a reasonable fraction of these cells with a sufficient level of transgene expression, the infection of bone marrow progenitor cells with retroviral vectors and their subsequent differentiation into BMDMs or BMDCs has become a very efficient approach. It has allowed for the analysis of the proteins of myeloid origin in their native cellular environment, both in a steady state or during processes that are critical for immune response such as phagocytosis, immunological synapse formation or migration. Here, we describe a protocol that allows stable expression of fluorescently tagged proteins of interest in murine bone marrow derived macrophages and dendritic cells.

<table>
	<tbody>
		<tr>
			<td>DMEM</td>
			<td>Thermo Fisher Scientific, Waltham, MA, USA</td>
			<td>15028</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal bovine serum (FBS)</td>
			<td>Thermo Fisher Scientific, Waltham, MA, USA</td>
			<td>10270</td>
			<td>For media suplementation</td>
		</tr>
		<tr>
			<td>KHCO3</td>
			<td>Lachema, Brno, Czech Republic</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>NH4Cl</td>
			<td>Sigma-Aldrich (Merck, Kenilworth, NJ, USA)</td>
			<td>A9434</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin</td>
			<td>BB Pharma AS, Prague, Czech Republic</td>
			<td>N/A</td>
			<td>PENICILIN G 1,0 DRASELN&#193; SOL&#39; BIOTIKA</td>
		</tr>
		<tr>
			<td>Streptomycin</td>
			<td>Sigma-Aldrich (Merck, Kenilworth, NJ, USA)</td>
			<td>S9137</td>
			<td>Streptomycin sulfate salt powder</td>
		</tr>
		<tr>
			<td>Gentamicin</td>
			<td>Dr. Kulich Pharma, Hradec Kr&#225;lov&#233;, Czech Republic</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyethylenimine, linear, MW 25,000</td>
			<td>Polyscience, Warrington, PA, USA</td>
			<td>23966</td>
			<td></td>
		</tr>
		<tr>
			<td>Polybrene</td>
			<td>Sigma-Aldrich (Merck, Kenilworth, NJ, USA)</td>
			<td>H9268</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>Sigma-Aldrich (Merck, Kenilworth, NJ, USA)</td>
			<td>E5134</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Prepared in-house by media facility of IMG ASCR, Prague, Czech Republic</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>APC anti-mouse/human CD11b Antibody, clone M1/70</td>
			<td>BioLegend (San Diego, CA, USA)</td>
			<td>101212</td>
			<td>flow cytometry analysis</td>
		</tr>
		<tr>
			<td>PE anti-mouse F4/80 Antibody, clone BM8</td>
			<td>BioLegend (San Diego, CA, USA)</td>
			<td>123110</td>
			<td>flow cytometry analysis</td>
		</tr>
		<tr>
			<td>APC anti-mouse CD11c Antibody, clone N418</td>
			<td>BioLegend (San Diego, CA, USA)</td>
			<td>117310</td>
			<td>flow cytometry analysis</td>
		</tr>
		<tr>
			<td>M-CSF</td>
			<td>PeproTech (Rocky Hill, NJ, USA)</td>
			<td>315-02</td>
			<td></td>
		</tr>
		<tr>
			<td>GM-CSF</td>
			<td>PeproTech (Rocky Hill, NJ, USA)</td>
			<td>315-03</td>
			<td></td>
		</tr>
		<tr>
			<td>Hoechst 33258</td>
			<td>Thermo Fisher Scientific, Waltham, MA, USA</td>
			<td>H1398</td>
			<td>flow cytometry analysis use at 1-2 &#181;g/ml</td>
		</tr>
	</tbody>
</table>

expression of fluorescent fusion proteins in murine bone marrow-derived dendritic cells and macrophages

Dendritic cells and macrophages are crucial cells that form the first line of defense against pathogens. They also play important roles in the initiation of an adaptive immune response. Experimental work with these cells is rather challenging. Their abundance in organs and tissues is relatively low. As a result, they cannot be isolated in large numbers. They are also difficult to transfect with cDNA constructs. In the murine model, these problems can be partially overcome by in vitro differentiation from bone marrow progenitors in the presence of M-CSF for macrophages or GM-CSF for dendritic cells. In this way, it is possible to obtain large amounts of these cells from very few animals. Moreover, bone marrow progenitors can be transduced with retroviral vectors carrying cDNA constructs during early stages of cultivation prior to their differentiation into bone marrow derived dendritic cells and macrophages. Thus, retroviral transduction followed by differentiation in vitro can be used to express various cDNA constructs in these cells. The ability to express ectopic proteins substantially extends the range of experiments that can be performed on these cells, including live cell imaging of fluorescent proteins, tandem purifications for interactome analyses, structure-function analyses, monitoring of cellular functions with biosensors and many others. In this article, we describe a detailed protocol for retroviral transduction of murine bone marrow derived dendritic cells and macrophages with vectors coding for fluorescently-tagged proteins. On the example of two adaptor proteins, OPAL1 and PSTPIP2, we demonstrate its practical application in flow cytometry and microscopy. We also discuss the advantages and limitations of this approach.

Signaling adaptor proteins are usually small proteins without any enzymatic activity. They possess various interaction domains or motifs, which mediate binding to other proteins involved in signal transduction, including tyrosine kinases, phosphatases, ubiquitin ligases and others21. For the demonstration of the functionality of this protocol myeloid cell adaptors PSTPIP2 and OPAL1 were selected. PSTPIP2 is a well characterized protein involved in the regulation of...

Watch this Scientific Journal Video about Expression of Fluorescent Fusion Proteins in Murine Bone Marrow-derived Dendritic Cells and Macrophages at JoVE.com

Expression of Fluorescent Fusion Proteins in Murine Bone Marrow-derived Dendritic Cells and Macrophages

In this article, we provide a detailed protocol for the expression of fluorescent fusion proteins in murine bone marrow derived dendritic cells and macrophages. The method is based on the transduction of bone marrow progenitors with retroviral constructs followed by differentiation into macrophages and dendritic cells in vitro.

Dendritic cells and macrophages are crucial cells that form the first line of defense against pathogens. They also play important roles in the initiation ...

This method can help answer key questions in the fields of macrophage and dendritic cell biology about the sub-cellular localization and dynamics of various proteins in these cell types. The main advantages of this technique are that it is relatively simple, inexpensive, and demonstrates a better efficiency and stability of expression than the majority of other available methods. Demonstrating the procedure will be Jarmila Kralova, a grad student from my laboratory.To produce the retrovirus, plate a single-cell suspension of Platinum Eco-packaging cells in a 10 centimeter petri dish and cultivate the cells in 15 milliliters of DMEM, supplemented with 10%fetal bovine serum, or FBS, until the culture is 50 to 60%confluent. The next day, add 20 micrograms of the retroviral construct of interest and 10 micrograms of PCL eco-packaging vector to 1 milliliter of DMEM without serum, with gentle mixing. Add 75 microliters of PEI in 1 milliliter of DMEM without serum and antibiotics to a second tube for a five minute incubation at room temperature, and mix the contents of both tubes together for an additional 10 minute incubation at room temperature.Next, carefully replace the medium on the Platinum Eco cells with 8 milliliters of fresh 37 degree Celsius DMEM supplemented with 2%FBS and carefully add the transfection mixture in drops to the plate. After a 4 hour incubation at 37 degrees Celsius, replace the supernatent with 10 milliliters of 37 degree Celsius DMEM, supplemented with 10%FBS for a 24 hour incubation at 37 degrees Celsius. The next day, use a 5 milliliter pipette to transfer the ecotropic retroviral particle-containing supernatent to a 15 milliliter centrifuge tube and remove the debris and containing cells by centrifugation.Meanwhile, add 10 milliliters of 37 degrees Celsius DMEM plus 10%FBS to the culture dish for another 24 hour incubation at 37 degrees Celsius and collect a second round of viral particles as just demonstrated. To harvest the bone marrow, in a tissue culture hood, use tweezers and scissors to remove the skin and part of the muscles from the hind limbs and carefully dislodge the acetabulum from the hip joint without breaking the femur. Cut the paws at the ankle joints and spray the bones with 70%ethanol.Then remove the rest of the muscle with a paper towel and place the bones in a 5 centimeter petri dish of PBS supplemented with 2%FBS. Next, bend the knee joint of each bone set and carefully separate the bones with scissors. Use the scissors to remove about one to two millimeters of each epiphysis of one bone and use a two or five milliliter syringe equipped with a 30 gauge needle loaded with fresh PBS plus FBS to flush the bone marrow from both ends of the bone into a 15 milliliters centrifuge tube.When the marrow has been collected from each of the bones, pellet the bone cells by centrifugation and re-suspend the pellet in 2.5 milliliters of red blood cell lysis buffer for two to three minutes at room temperature. After lysing, filter the cells through a 100 micrometer cell strainer into a new 15 milliliter centrifuge tube and restore the tenacity with 12 milliliters of PBS plus FBS. Re-suspend the pellet in DMEM, supplemented with 10%FBS and antibiotics for counting and plate five to 10 times 10 to the sixth bone marrow cells in a 10 centimeter, non-tissue culture treated petri dish in 10 milliliters of DMEM supplemented with serum and macrophage colony stimulating factor, or MCSF.On day five of culture, carefully tilt the cell culture dish and remove all but approximately 5 milliliters of medium from the surface near the edge of the dish. Then add 20 milliliters of fresh 37 degree Celsius medium supplemented with FBS and MCSF to the dish and return the cells to the cell culture incubator. To harvest the cells, on day six to seven, remove all of the medium and floating cells and wash the culture with 37 degree Celsius PBS.Detach the adherent cells with five milliliters of 0.02%EDTA and PBS for three to five minutes at 37 degrees Celsius in the tissue culture incubator and use a five milliliter pipette to gently flush the dissociated cells from the plate bottom. Then transfer the cells to a 50 milliliter centrifuge tube containing 25 milliliters of fresh PBS. To induce EGFP tagged protein expression in bone marrow derived antigen presenting cells, at the beginning of the cell differentiation protocol, dilute the bone marrow cells to a two to five times 10 to the sixth cells per milliliters of DMEM plus FBS and antibiotics conentration and plate the cells of one milliliter of medium per well, supplemented with the appropriate differentiation cytokine.After four to six hours in the cell culture incubator, add two milliliters of the first round of collected virus supplemented with polybrene and transduce the cell cultures by centrifugation and a four hour incubation in the cell culture incubator. At the end of the transduction period, transfer the nonadherent cells from each well into individual 15 milliliter centrifuge tubes and collect the cells by centrifugation. If larger amount of cells is needed, the cells can be infected with the same constract in multiple wells and pooled before differentiation.Then re-suspend the pellets in 10 milliliters of culture medium supplemented with the appropriate differentiation cytokine and plate the cells onto one 10 centimeter non tissue culture treated petri dish per tube, for their six to eight day culture, as just demonstrated. Evaluation of the efficacy of Platinum Eco transfection by flow cytometry after the collection of the second virus containing supernatent reveals a mean transfection efficiency of 62%for PSTPIP2-EGFP and 53%for OPAL1-EGFP. Retroviral transduction does not affect the differentiation status of the bone marrow derived cells with more than 90%of the cells in both cultures demonstrating positivity for their respective markers after transduction with either virus.And with the appropriate, characteristic morphological changes observed for both types of differentiated cell. Of note, the overall expression of EGFP was lower in bone marrow derived dendritic cell cultures compared to bone marrow derived macrophage EGFP expression, regardless of type of retrovirus. While attempting this procedure, it is important to remember to use non tissue, culture treated plastic dishes that are typically used for cultivating bacteria if you plan to remove cells from the dish for experiment.Following this procedure, other methods live cell imaging, super resolution microscopy or other types of microscopy can be employed to answer additional questions about the sub-cellular localization and dynamics of dendritic cell and macrophage proteins of interest. This technique paved the way for researchers in the immunology field in exploring the distribution and spacial relationships of proteins expressed by macrophages and dendritic cells and in furthering our understanding of the function of these protein during immune responses. Don't forget that working with viral particles can be extremely hazardous and that precautions, such as minimalizing aerosol generation, wearing protective equipment, and using a laminar flow hood, should always be taken while performing this procedure.

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JoVE Journal

Biology

10.1K visualizações.  Institute of Molecular Genetics of the ASCR. Este método pode ajudar a responder a perguntas-chave nos campos da biologia celular macrófago e dendrítica sobre a localização subcelular e dinâmica de várias proteínas nesses tipos de células. As principais vantagens dessa técnica são que ela é relativamente simples, barata e demonstra uma melhor eficiência e estabilidade de expressão do que a maioria dos outros métodos disponíveis. Demonstrando o procedimento será Jarmila Kralova, uma estudante de pós-graduação do meu l...