Name: exploiting live imaging to track nuclei during myoblast differentiation and fusion
Uploaded: 2019-04-13T14:00:00
Description: Watch this Scientific Journal Video about Exploiting Live Imaging to Track Nuclei During Myoblast Differentiation and Fusion at JoVE.com

This work was supported by the AFM-Telethon to E.V. (#21545) and by the Ospedale San Raffaele (OSR) Seed Grant to S.Z. (ZAMBRA5X1000). Dr. Jean-Yves Tinevez from the Image Analysis Hub of the Institut Pasteur is acknowledged for publicly sharing his &#34;Simple Tracker&#34; MATLAB routines.

All procedures involving animal subjects were approved by the San Raffaele Institutional Animal Care and Use Committee.
1. Dissection of mouse hindlimb muscles
<ol>
	<li>Sterilize tweezers and scissors (both straight and curved) by autoclaving.</li>
	<li>Prepare and filter (0.22 &#181;m) all the media (blocking medium, digestion medium, proliferating medium, and differentiating medium) before starting the experiment (see Table of Materials).</li>
	<li>Put 5 mL of phosphate-b...

<ol>
	<li>Janssen, I., Heymsfield, S. B., Wang, Z. M., Ross, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Skeletal+muscle+mass+and+distribution+in+468+men+and+women+aged+18-88+yr.">Skeletal muscle mass and distribution in 468 men and women aged 18-88 yr.</a> Journal of Applied physiology. 89 (1), 81-88 (2000).</li><li>Ten Broek, R. W., Grefte, S., Von den Hoff, 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=Regulatory+factors+and+cell+populations+involved+in+skeletal+muscle+regeneration.">Regulatory factors and cell populations involved in skeletal muscle regeneration.</a> Journal of Cellular Physiology. 224 (1), 7-16 (2010).</li><li>Bentzinger, C. F., Wang, Y. X., Dumont, N. A., Rudnicki, M. 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(120), e55047 (2017).</li><li>Roman, W., Gomes, E. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nuclear+positioning+in+skeletal+muscle.">Nuclear positioning in skeletal muscle.</a> Seminars in Cell &amp; Developmental Biology. , (2017).</li><li>Pimentel, M. R., Falcone, S., Cadot, B., Gomes, E. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+Vitro+Differentiation+of+Mature+Myofibers+for+Live+Imaging.">In Vitro Differentiation of Mature Myofibers for Live Imaging.</a> Journal of Visualized Experiments. (119), e55141 (2017).</li><li>Foudi, 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=Analysis+of+histone+2B-GFP+retention+reveals+slowly+cycling+hematopoietic+stem+cells.">Analysis of histone 2B-GFP retention reveals slowly cycling hematopoietic stem cells.</a> Nature Biotechnology. 27 (1), 84-90 (2009).</li><li>Tirone, M., 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=High+mobility+group+box+1+orchestrates+tissue+regeneration+via+CXCR4.">High mobility group box 1 orchestrates tissue regeneration via CXCR4.</a> The Journal of Experimental Medicine. 215 (1), 303-318 (2018).</li><li>Zambrano, S., De Toma, I., Piffer, A., Bianchi, M. E., Agresti, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NF-kappaB+oscillations+translate+into+functionally+related+patterns+of+gene+expression.">NF-kappaB oscillations translate into functionally related patterns of gene expression.</a> eLife. 5, e09100 (2016).</li><li>Adamski, D., 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=Effects+of+Hoechst+33342+on+C2C12+and+PC12+cell+differentiation.">Effects of Hoechst 33342 on C2C12 and PC12 cell differentiation.</a> FEBS Letters. 581 (16), 3076-3080 (2007).</li><li>Otsu, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Threshold+Selection+Method+from+Gray-Level+Histograms.">A Threshold Selection Method from Gray-Level Histograms.</a> IEEE Transactions on Systems, Man, and Cybernetics. 9 (1), 62-66 (1979).</li><li>. Simpel Tracker - File Exchange - MATLAB Central Available from: <a target="_blank" href="https://it.mathworks.com/matlabcentral/fileexchange/34040-simple-tracker">https://it.mathworks.com/matlabcentral/fileexchange/34040-simple-tracker</a> (2016)</li><li>Burkard, R., Dell'Amico, M., Martello, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Assignment Problems, Revised Reprint. , (2009).</li><li>Falcone, 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=N-WASP+is+required+for+Amphiphysin-2/BIN1-dependent+nuclear+positioning+and+triad+organization+in+skeletal+muscle+and+is+involved+in+the+pathophysiology+of+centronuclear+myopathy.">N-WASP is required for Amphiphysin-2/BIN1-dependent nuclear positioning and triad organization in skeletal muscle and is involved in the pathophysiology of centronuclear myopathy.</a> EMBO Molecular Medicine. 6 (11), 1455-1475 (2014).</li><li>Syverud, B. C., Lee, J. D., VanDusen, K. W., Larkin, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+Purification+of+Satellite+Cells+for+Skeletal+Muscle+Tissue+Engineering.">Isolation and Purification of Satellite Cells for Skeletal Muscle Tissue Engineering.</a> Journal of Regenerative Medicine. 3 (2), (2014).</li><li>Liu, L., Cheung, T. H., Charville, G. W., Rando, T. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+of+skeletal+muscle+stem+cells+by+fluorescence-activated+cell+sorting.">Isolation of skeletal muscle stem cells by fluorescence-activated cell sorting.</a> Nature Protocols. 10 (10), 1612-1624 (2015).</li></ol>

Muscle fibers (myofibers) are multinucleated cells that are formed by the fusion of muscle precursors cells (myoblasts) derived from muscle stem cells (satellite cells) that undergo proliferation and differentiation2,3,4. To assess myoblast differentiation, the common procedure consists of culturing myoblasts in differentiating medium and fixing the cells at different time points to perform immunofluorescence staining for MyHC, ...

Skeletal muscle is the largest tissue in the human body, totaling 35%-40% of body mass1. Satellite cells are muscle stem cells, anatomically characterized by their position (juxtaposed to the plasma membrane, underneath the basal lamina of muscle fibers), that give rise to proliferating myoblasts (myogenic progenitor cells), which eventually differentiate and integrate into existing myofibers and/or fuse to form new myofibers2,3,4. Their discovery and the progress in the study of their biology has led to significant insights into muscle development and regeneration.
Protocols to isolate and differentiate myoblasts into myotubes have been developed many years ago and are still widely used to study skeletal muscle differentiation5,6,7. However, most of these methods represent static procedures that rely on the analysis of fixed cells and, consequently, do not allow scientists to fully explore highly dynamic processes, such as myoblast fusion and myofiber maturation. The most striking example is nuclear positioning, which is tightly regulated, with nuclei initially in the center of the myofiber and, then, located at the periphery after myofiber maturation8,9. Live imaging is the most appropriate technique to obtain further insights into such a peculiar phenomenon.
Here, we describe a method that enables scientists to record myoblast differentiation and myotube formation by time-lapse microscopy and to perform quantitative analyses from the automatic tracking of myoblast nuclei. This method provides a high-throughput quantitative characterization of nuclear dynamics and myoblast behavior during differentiation and fusion. The protocol is divided into four different parts, namely (1) the collection of muscles from the hindlimbs of mice, (2) the isolation of primary myoblasts that consists in mechanical and enzymatic digestion, (3) myoblast proliferation and differentiation, and (4) live imaging to track nuclei within the first 16 h of myoblast differentiation.
In the following procedure, myoblasts are isolated from H2B-GFP mice and treated with 1 &#181;g/mL of doxycycline to induce H2B-GFP expression, as previously described10. Alternatively, it is possible to isolate the myoblasts from other transgenic mice that express a fluorescent protein in the nucleus or to transfect the cells isolated from wild-type mice to express a fluorescent protein in the nucleus, as described by Pimentel et al.9.

<table>
	<tbody>
		<tr>
			<td>chicken embryos extract</td>
			<td>Seralab</td>
			<td>CE-650-J</td>
			<td></td>
		</tr>
		<tr>
			<td>collagenase</td>
			<td>Sigma</td>
			<td>C9263-1G</td>
			<td>125units/mg</td>
		</tr>
		<tr>
			<td>collagen from calf skin</td>
			<td>Sigma</td>
			<td>C8919</td>
			<td></td>
		</tr>
		<tr>
			<td>dispase</td>
			<td>Gibco</td>
			<td>17105-041</td>
			<td>1.78 units/mg</td>
		</tr>
		<tr>
			<td>doxyciclin</td>
			<td>Sigma</td>
			<td>D1515</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Sigma</td>
			<td>D5671</td>
			<td></td>
		</tr>
		<tr>
			<td>fetal bovine serum</td>
			<td>Life technologies</td>
			<td>10270106</td>
			<td></td>
		</tr>
		<tr>
			<td>gentamicin</td>
			<td>Sigma</td>
			<td>G1397</td>
			<td></td>
		</tr>
		<tr>
			<td>Horse serum</td>
			<td>Invitrogen</td>
			<td>16050-098</td>
			<td></td>
		</tr>
		<tr>
			<td>Hoechst</td>
			<td>life technologies</td>
			<td>33342</td>
			<td></td>
		</tr>
		<tr>
			<td>IMDM</td>
			<td>Sigma</td>
			<td>I3390</td>
			<td></td>
		</tr>
		<tr>
			<td>L-glutamine</td>
			<td>Sigma</td>
			<td>G7513</td>
			<td></td>
		</tr>
		<tr>
			<td>Matrigel</td>
			<td>Corning</td>
			<td>356231</td>
			<td></td>
		</tr>
		<tr>
			<td>penicillin-streptomycin</td>
			<td>Sigma</td>
			<td>P0781</td>
			<td></td>
		</tr>
		<tr>
			<td>red blood cells lysis medium</td>
			<td>Biolegend</td>
			<td>420301</td>
			<td></td>
		</tr>
		<tr>
			<td>Digestion medium</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>collagenase</td>
			<td>40 mg</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>dispase</td>
			<td>70 mg</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>20 ml</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>filtered 0.22um</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Blocking medium</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal bovine serum</td>
			<td>10%</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>L-glutammine</td>
			<td>1%</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>penicillin-streptomycin</td>
			<td>1%</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>gentamicin</td>
			<td>1 &#8240;</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>filtered 0.22um</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>proliferation medium</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>IMDM</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal bovine serum</td>
			<td>20%</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>L-glutammine</td>
			<td>1%</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>penicillin-streptomycin</td>
			<td>1%</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>gentamicin</td>
			<td>1 &#8240;</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>chichen embryo extract</td>
			<td>3%</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>filtered 0.22um</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>differentiation medium</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>IMDM</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Horse serum</td>
			<td>2%</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>L-glutammine</td>
			<td>1%</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>penicillin-streptomycin</td>
			<td>1%</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>gentamicin</td>
			<td>1 &#8240;</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>chichen embryo extract</td>
			<td>1%</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>filtered 0.22um</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

exploiting live imaging to track nuclei during myoblast differentiation and fusion

Nuclear positioning within cells is important for multiple cellular processes in development and regeneration. The most intriguing example of nuclear positioning occurs during skeletal muscle differentiation. Muscle fibers (myofibers) are multinucleated cells formed by the fusion of muscle precursor cells (myoblasts) derived from muscle stem cells (satellite cells) that undergo proliferation and differentiation. Correct nuclear positioning within myofibers is required for the proper muscle regeneration and function. The common procedure to assess myoblast differentiation and myofiber formation relies on fixed cells analyzed by immunofluorescence, which impedes the study of nuclear movement and cell behavior over time. Here, we describe a method for the analysis of myoblast differentiation and myofiber formation by live cell imaging. We provide a software for automated nuclear tracking to obtain a high-throughput quantitative characterization of nuclear dynamics and myoblast behavior (i.e., the trajectory) during differentiation and fusion.

To automatically follow nuclear movement during myoblast differentiation in live imaging, the nuclei should preferentially be fluorescently labeled. It is important to note that using DNA-intercalating molecules is not feasible because these molecules interfere with the proliferation and differentiation of primary myoblasts13. As an example, proliferation and differentiation have been analyzed in primary myoblasts cultured with or without Hoechst (<strong class="xf...

Watch this Scientific Journal Video about Exploiting Live Imaging to Track Nuclei During Myoblast Differentiation and Fusion at JoVE.com

Exploiting Live Imaging to Track Nuclei During Myoblast Differentiation and Fusion

Skeletal muscle differentiation is a highly dynamic process, which particularly relies on nuclear positioning. Here, we describe a method to track nuclei movements by live cell imaging during myoblast differentiation and myotube formation and to perform a quantitative characterization of nuclei dynamics by extracting information from automatic tracking.

Nuclear positioning within cells is important for multiple cellular processes in development and regeneration. The most intriguing example of nuclear ...

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