Name: an ectopic chemokine expression model for testing macrophage recruitment in vivo
Uploaded: 2019-09-25T14:30:00
Description: Watch this Scientific Journal Video about An Ectopic Chemokine Expression Model for Testing Macrophage Recruitment In Vivo at JoVE.com

We thank Dr. Jingrong Peng for sharing the Tg (fabp10a: DsRed) transgenic line; Dr. Zilong Wen for sharing the Tg (mpeg1: GFP) transgenic lines; Dr. Koichi Kawakami for providing the pTol2 vector. This work was supported by the National Natural Science Foundation of China (31771594), Guangdong Science and Technology Plan projects (2019A030317001) and the Fundamental Research Funds for the Central Universities (D2191450).

NOTE: All the samples were treated by phenylthiourea(PTU) egg water to inhibit pigment.
1. Generation of Tg (fabp10a:il34) Transgenic Constructs and Fish Injection
<ol>
	<li>Clone the 2.8 kb fabp10a promoter8 and the IL-34 coding regions (ENSDART00000126460.3) of zebrafish into the pTol2 vector to generate the fabp10a-il34 construct. Inject the constructs into one-cell stage Tg (mpeg1: GFP) and WT fish embr...

<ol>
	<li>Howe, 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=The+zebrafish+reference+genome+sequence+and+its+relationship+to+the+human+genome.">The zebrafish reference genome sequence and its relationship to the human genome.</a> Nature. 496 (7446), 498-503 (2013).</li><li>Wang, Y., 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=IL-34+is+a+tissue-restricted+ligand+of+CSF1R+required+for+the+development+of+Langerhans+cells+and+microglia.">IL-34 is a tissue-restricted ligand of CSF1R required for the development of Langerhans cells and microglia.</a> Nature Immunology. 13 (8), 753-760 (2012).</li><li>Lin, H., 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=Discovery+of+a+cytokine+and+its+receptor+by+functional+screening+of+the+extracellular+proteome.">Discovery of a cytokine and its receptor by functional screening of the extracellular proteome.</a> Science. 320 (5877), 807-811 (2008).</li><li>Wei, 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=Functional+overlap+but+differential+expression+of+CSF-1+and+IL-34+in+their+CSF-1+receptor-mediated+regulation+of+myeloid+cells.">Functional overlap but differential expression of CSF-1 and IL-34 in their CSF-1 receptor-mediated regulation of myeloid cells.</a> Journal of leukocyte biology. 88 (3), 495-505 (2010).</li><li>Etienne, D., Foucher, S. B. L. P., Norbert Ifrah, P. G. Y. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=IL-34+Induces+the+Differentiation+of+Human+Monocytes+into+Immunosuppressive+Macrophages.+Antagonistic+Effects+of+GM-CSF+and+IFNc.">IL-34 Induces the Differentiation of Human Monocytes into Immunosuppressive Macrophages. Antagonistic Effects of GM-CSF and IFNc.</a> PLoS One. 8 (2), e56045 (2013).</li><li>Segaliny, A. I., 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=Syndecan-1+regulates+the+biological+activities+of+interleukin-34.">Syndecan-1 regulates the biological activities of interleukin-34.</a> Biochimica et Biophysica Acta. 1853 (5), 1010-1021 (2015).</li><li>Zhou, S. L., 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=miR-28-5p-IL-34-macrophage+feedback+loop+modulates+hepatocellular+carcinoma+metastasis.">miR-28-5p-IL-34-macrophage feedback loop modulates hepatocellular carcinoma metastasis.</a> Hepatology. 63 (5), 1560-1575 (2016).</li><li>Gordon, J. I., 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=Tissue+specific+expression+and+developmental+regulation+of+two+genes+coding+for+rat+fatty+acid+binding+proteins.">Tissue specific expression and developmental regulation of two genes coding for rat fatty acid binding proteins.</a> Journal of Biological Chemistry. 260 (4), 1995-1998 (1985).</li><li>Westerfield, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Zebrafish Book: A Guide for the Laboratory Use of Zebrafish (Danio rerio). , (2000).</li><li>N&#252;sslein-Volhard, C., Dahm, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Zebrafish: a practical approach. , (2002).</li><li>Jiang, Y., Chen, J., Yen, K., Xu, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ectopically+Expressed+IL-34+Can+Efficiently+Induce+Macrophage+Migration+to+the+Liver+in+Zebrafish.">Ectopically Expressed IL-34 Can Efficiently Induce Macrophage Migration to the Liver in Zebrafish.</a> Zebrafish. 16 (2), 165-170 (2019).</li></ol>

The protocol described here allows us to investigate the function of a chemokine on the behavior of macrophagein vivo and the procedure requires some technical expertise. In summary, there are several critical steps to avoid complications in the protocol: 1) select a suitable transgenic line which shows specific and strong transgenic signal to label the cell of interest; 2) select an appropriate tissue which is accessible for imaging and transgenic gene overexpression; 3) make a sensitive and specific RNA probe; 4) selec...

Zebrafish is a small tropical hard-bones freshwater fish originated in India. Regarding the gene conservation, zebrafish have a similarity of 87% to the human1. It can provide us insights on related subjects of human by studying the gene regulation, protein function and cell behavior such as migration, proliferation et.al in zebrafish. Zebrafish embryo can be used to observe the development of early embryos at different stages after inhibiting pigment. Meanwhile, it takes only three months for zebrafish to develop into sexual maturity, then the zebrafish can produce hundreds of eggs every 4 days. Mini-size, simple breeding, strong reproductive capacity, these advantages make zebrafish culture very space-saving, conducive to large-scale culture. The traditional mammalian model mouse has a higher maintenance costs than zebrafish, therefore limiting the scale of mouse raising. In the aspect of early embryo development, mouse embryo is difficult to observe in live condition due to the characteristics of mouse embryo development in the mother womb. On the contrary, zebrafish embryos develop externally and are transparent, therefore they are easy to observe under a microscope. Furthermore, zebrafish is very easy to construct a variety of transgenic lines for related gene function research. Currently, various zebrafish transgenic lines are available to label different types of cells. It is very convenient now to construct transgenic lines to overexpress chemokines in specific locations and study the chemokines function on cell behavior in zebrafish.
Here, we provided a workflow to use zebrafish transgenic line to investigate the function of IL-34 on macrophage behavior in vivo2,3,4,5,6,7. Firstly, we constructed a liver-specific overexpression plasmid of the gene il34 and injected the plasmid into one-cell stage Tg (mpeg1: GFP) fish embryos which specifically labeled the macrophages by fluorescent protein GFP. Then, we used whole mount fluorescent in situ hybridization and immunostaining to detect the pattern of the il34 expression and the number or location of macrophages. The injected WT embryos were raised to generate a stable transgenic line. In these steps, we established and validated the cytokine-producing line and visually assessed the effects that can be seen on macrophage distribution. Finally, to investigate macrophage behavior in response to the cytokine, we used confocal live imaging to directly observe the macrophage migration to confirm the function of il34 on the macrophage migration in vivo.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Antibody</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Alexa 488-Anti-Goat antibody</td>
			<td>Invitrogen</td>
			<td>A11055</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-Digoxigenin-HRP&#160;</td>
			<td>perkinelmer</td>
			<td>NEF832001EA</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat-Anti-GFP antibody</td>
			<td>Abcam</td>
			<td>ab6658</td>
			<td></td>
		</tr>
		<tr>
			<td>Reagent</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>CaCl2&#183; 2H2O</td>
			<td>Sigma</td>
			<td>21097</td>
			<td></td>
		</tr>
		<tr>
			<td>Cyanine 3 Plus Amplification Reagent</td>
			<td>perkinelmer</td>
			<td>NEL745001KT</td>
			<td></td>
		</tr>
		<tr>
			<td>E2 solution</td>
			<td></td>
			<td></td>
			<td>15 mM&#160; NaCl +0.5 mM KCl +1.0 mM MgSO4+150 &#181;M&#160; KH2PO4 + 50 &#181;M&#160; Na2HPO4 +1.0 mM CaCl2 + 0.7 mM NaHCO3&#160;</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum(FBS)</td>
			<td>Life</td>
			<td>10099-133</td>
			<td></td>
		</tr>
		<tr>
			<td>formamide</td>
			<td>Diamond</td>
			<td>A100314</td>
			<td></td>
		</tr>
		<tr>
			<td>glycerol&#160;</td>
			<td>Sigma</td>
			<td>V900860</td>
			<td></td>
		</tr>
		<tr>
			<td>heparin sodium</td>
			<td>Sigma</td>
			<td>H3149</td>
			<td></td>
		</tr>
		<tr>
			<td>hybridization buffer(HB)</td>
			<td></td>
			<td></td>
			<td>50% formamide+ 5&#215;SSC+9 mM sodium citrate+50 &#956;g/ml heparin sodium+ 500 &#956;g/ml tRNA+ 0.1% Tween20</td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sigma</td>
			<td>P5405</td>
			<td></td>
		</tr>
		<tr>
			<td>KH2PO4</td>
			<td>Sigma</td>
			<td>P5655</td>
			<td></td>
		</tr>
		<tr>
			<td>low melting agarose</td>
			<td>Sigma</td>
			<td>A9414</td>
			<td></td>
		</tr>
		<tr>
			<td>methanol</td>
			<td>GHTECH</td>
			<td>1.17112.023</td>
			<td></td>
		</tr>
		<tr>
			<td>methylene blue&#160;</td>
			<td>Sigma</td>
			<td>M9140</td>
			<td></td>
		</tr>
		<tr>
			<td>MgSO4</td>
			<td>Sigma</td>
			<td>M2643</td>
			<td></td>
		</tr>
		<tr>
			<td>Na2HPO4</td>
			<td>Sigma</td>
			<td>S5136</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma</td>
			<td>S5886</td>
			<td></td>
		</tr>
		<tr>
			<td>NaHCO3&#160;</td>
			<td>Sigma</td>
			<td>S5761</td>
			<td></td>
		</tr>
		<tr>
			<td>paraformaldehyde(PFA)</td>
			<td>Sigma</td>
			<td>158127</td>
			<td>Suspend 16 g of PFA in 400 ml of 1x PBS, heat at 60 &#176;C&#160; to dissolve about 30 min. This solution can be prepared in advance and stored at -4 &#176;C. Caution. Manipulate with mask.</td>
		</tr>
		<tr>
			<td>10&#215;PBS</td>
			<td></td>
			<td></td>
			<td>14.2 g Na2HPO4+80 g NaCl+2 g KCl+ 2.4 g KH2PO4 in 1L ddH2O</td>
		</tr>
		<tr>
			<td>phenylthiourea(PTU)</td>
			<td>Sigma</td>
			<td>P7629</td>
			<td></td>
		</tr>
		<tr>
			<td>1&#215;Plus Amplification Diluent</td>
			<td>perkinelmer</td>
			<td>NEL745001KT</td>
			<td></td>
		</tr>
		<tr>
			<td>Proteinase K&#160;</td>
			<td>Fermentas</td>
			<td>E00492</td>
			<td></td>
		</tr>
		<tr>
			<td>20&#215;Saline sodium citrate(SSC)</td>
			<td></td>
			<td></td>
			<td>175.3 g NaCl+ 88.2 g sodium citrate in 1 L ddH2O, PH 7.0</td>
		</tr>
		<tr>
			<td>sodium citrate</td>
			<td>Sigma</td>
			<td>A5040</td>
			<td></td>
		</tr>
		<tr>
			<td>tricaine</td>
			<td>Sigma</td>
			<td>E10521</td>
			<td></td>
		</tr>
		<tr>
			<td>tRNA&#160;</td>
			<td>Sigma</td>
			<td>R6625</td>
			<td></td>
		</tr>
		<tr>
			<td>Tween20</td>
			<td>Sigma</td>
			<td>P2287</td>
			<td></td>
		</tr>
		<tr>
			<td>Plasmid</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>pBLK-fabp10a-il34-sv40</td>
			<td></td>
			<td></td>
			<td>For Tg (fab10a:il34) transgenic line generation</td>
		</tr>
		<tr>
			<td>pBSK-il34</td>
			<td></td>
			<td></td>
			<td>For il34 probe preparation</td>
		</tr>
		<tr>
			<td>Fish</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Tg (mpeg1: GFP)</td>
			<td></td>
			<td></td>
			<td>Label macrophages with GFP</td>
		</tr>
		<tr>
			<td>Tg (fabp10a: DsRed)</td>
			<td></td>
			<td></td>
			<td>Label liver cells with DsRed</td>
		</tr>
		<tr>
			<td>Tg (fab10a:il34)</td>
			<td></td>
			<td></td>
			<td>Over-expression IL-34 in liver cells</td>
		</tr>
	</tbody>
</table>

an ectopic chemokine expression model for testing macrophage recruitment in vivo

Zebrafish are widely used in basic and biomedical research. Many zebrafish transgenic lines are currently available to label various types of cells. Owing to the transparent embryonic body of zebrafish, it is convenient for us to study the effect of one chemokine on the behavior of a certain type of cells in vivo. Here we provided a workflow to investigate the function of a chemokine on macrophage migration in vivo. We constructed a tissue-specific overexpression plasmid to overexpress IL-34 and injected the plasmid into one-cell stage transgenic fish embryos whose macrophages were specifically labeled by a fluorescent protein. We then used whole mount fluorescent in situ hybridization and immunostaining to detect the pattern of the chemokine expression and the number or location of macrophages. The injected WT embryos were raised to generate a stable transgenic line. Finally, we used confocal live imaging to directly observe macrophage behavior in the stable transgenic fish to study the function of IL-34 on macrophages in vivo.

The steps involved in the protocol of zebrafish are illustrated in Figure 2. First, we generated the pBLK-fabp10a-il34-sv40 construct in which il34 was driven by the fabp10a promoter (Figure 2). The construct was microinjected into one-cell stage Tg (mpeg1: GFP) zebrafish embryos which can label macrophages with GFP and WT embryos which were raised to adults to generate transgenic stable line (...

Watch this Scientific Journal Video about An Ectopic Chemokine Expression Model for Testing Macrophage Recruitment In Vivo at JoVE.com

An Ectopic Chemokine Expression Model for Testing Macrophage Recruitment In Vivo

To test the effect of a chemokine on macrophage recruitment in vivo, the whole mount in situ hybridization was used to detect the ectopic expression of the chemokine, and immunostaining was used to label macrophages. Live imaging was used for real-time observation of macrophage migration.

Zebrafish are widely used in basic and biomedical research. Many zebrafish transgenic lines are currently available to label various types of cells. Owing ...

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