Name: live cell imaging to assess the dynamics of metaphase timing and cell fate following mitotic spindle perturbations
Uploaded: 2019-09-20T15:00:00
Description: Watch this Scientific Journal Video about Live Cell Imaging to Assess the Dynamics of Metaphase Timing and Cell Fate Following Mitotic Spindle Perturbations at JoVE.com

DLM is supported by an NSF GRFP. ALM is supported by funding from the Smith Family Award for Excellence in Biomedical Research.

1. Generation of hTERT-RPE-1 cells stably expressing RFP-Histone 2B (RFP-H2B) and &#945;-tubulin-EGFP (tub-EGFP)
NOTE: All steps follow aseptic techniques and take place in a biosafety level II+ (BSL2+) safety cabinet.
<ol>
	<li>Generate retrovirus carrying the genes of interest (&#945;-tubulin-EGFP and RFP-H2B) by the transfection of 293T cells with the appropriate lentiviral plasmids according to the manufacturer&#39;s instructions of the lipid-based transfection delivery system.
	<ol>
		<...

<ol>
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Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitosis-targeted+anti-cancer+therapies:+where+they+stand.">Mitosis-targeted anti-cancer therapies: where they stand.</a> Cell Death and Diseases. 3, 411 (2012).</li><li>Martin, M., Akhmanova, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coming+into+Focus:+Mechanisms+of+Microtubule+Minus-End+Organization.">Coming into Focus: Mechanisms of Microtubule Minus-End Organization.</a> Trends in Cell Biology. 28, 574-588 (2018).</li><li>Maiato, H., Logarinho, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitotic+spindle+multipolarity+without+centrosome+amplification.">Mitotic spindle multipolarity without centrosome amplification.</a> Nature Cell Biology. 16, 386-394 (2014).</li><li>Vitre, B. D., Cleveland, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Centrosomes,+chromosome+instability+(CIN)+and+aneuploidy.">Centrosomes, chromosome instability (CIN) and aneuploidy.</a> Current Opinion in Cell Biology. 24, 809-815 (2012).</li><li>Godinho, S. A., Pellman, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Causes+and+consequences+of+centrosome+abnormalities+in+cancer.">Causes and consequences of centrosome abnormalities in cancer.</a> Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 369, (2014).</li><li>Navarro-Serer, B., Childers, E. P., Hermance, N. M., Mercadante, D., Manning, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aurora+A+inhibition+limits+centrosome+clustering+and+promotes+mitotic+catastrophe+in+cells+with+supernumerary+centrosomes.">Aurora A inhibition limits centrosome clustering and promotes mitotic catastrophe in cells with supernumerary centrosomes.</a> Oncotarget. 10, 1649-1659 (2019).</li><li>Conte, N., 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=TACC1-chTOG-Aurora+A+protein+complex+in+breast+cancer.">TACC1-chTOG-Aurora A protein complex in breast cancer.</a> Oncogene. 22, 8102-8116 (2003).</li><li>Schumacher, J. M., Ashcroft, N., Donovan, P. J., Golden, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+highly+conserved+centrosomal+kinase,+AIR-1,+is+required+for+accurate+cell+cycle+progression+and+segregation+of+developmental+factors+in+Caenorhabditis+elegans+embryos.">A highly conserved centrosomal kinase, AIR-1, is required for accurate cell cycle progression and segregation of developmental factors in Caenorhabditis elegans embryos.</a> Development. 125, 4391-4402 (1998).</li><li>Asteriti, I. A., Giubettini, M., Lavia, P., Guarguaglini, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aurora-A+inactivation+causes+mitotic+spindle+pole+fragmentation+by+unbalancing+microtubule-generated+forces.">Aurora-A inactivation causes mitotic spindle pole fragmentation by unbalancing microtubule-generated forces.</a> Molecular Cancer. 10, 131 (2011).</li><li>Chan, J. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+clinical+overview+of+centrosome+amplification+in+human+cancers.">A clinical overview of centrosome amplification in human cancers.</a> International Journal of Biological Sciences. 7, 1122-1144 (2011).</li><li>Kramer, A., Maier, B., Bartek, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Centrosome+clustering+and+chromosomal+(in)stability:+a+matter+of+life+and+death.">Centrosome clustering and chromosomal (in)stability: a matter of life and death.</a> Molecular Oncology. 5, 324-335 (2011).</li><li>Ganem, N. J., Godinho, S. A., Pellman, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+mechanism+linking+extra+centrosomes+to+chromosomal+instability.">A mechanism linking extra centrosomes to chromosomal instability.</a> Nature. 460, 278-282 (2009).</li><li>Silkworth, W. T., Nardi, I. K., Scholl, L. M., Cimini, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multipolar+spindle+pole+coalescence+is+a+major+source+of+kinetochore+mis-attachment+and+chromosome+mis-segregation+in+cancer+cells.">Multipolar spindle pole coalescence is a major source of kinetochore mis-attachment and chromosome mis-segregation in cancer cells.</a> PLoS One. 4, e6564 (2009).</li><li>Nigg, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Centrosome+aberrations:+cause+or+consequence+of+cancer+progression?.">Centrosome aberrations: cause or consequence of cancer progression?.</a> Nature reviews, Cancer. 2, 815-825 (2002).</li><li>Godinho, S. A., Kwon, M., Pellman, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Centrosomes+and+cancer:+how+cancer+cells+divide+with+too+many+centrosomes.">Centrosomes and cancer: how cancer cells divide with too many centrosomes.</a> Cancer Metastasis Reviews. 28, 85-98 (2009).</li><li>Quintyne, N. J., Reing, J. E., Hoffelder, D. R., Gollin, S. M., Saunders, W. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spindle+multipolarity+is+prevented+by+centrosomal+clustering.">Spindle multipolarity is prevented by centrosomal clustering.</a> Science. 307, 127-129 (2005).</li><li>Magidson, V., Khodjakov, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Circumventing+photodamage+in+live-cell+microscopy.">Circumventing photodamage in live-cell microscopy.</a> Methods in Cell Biology. 114, 545-560 (2013).</li></ol>

The temporal resolution provided by the time-lapse imaging allows for the visualization and assessment of sequential cellular events within single cells. Approaches that make use of cellular synchronization followed by the collection and fixation of cells at sequential time points are limited in that comparisons are ultimately made between populations of cells. In contexts where the cellular response to perturbations may be non-uniform, or where the process being visualized is dynamic, live cell time-lapse imaging is bet...

Image-based analysis of fixed cells is commonly used to assess the cell population level changes in response to various perturbations. When combined with cell synchronization, followed by the collection and imaging of serial time points, such approaches can be used to suggest a cellular sequence of events. Nevertheless, fixed cell imaging is limited in that temporal relationships are implied for a population and not demonstrated at the level of individual cells. In this way, while fixed cell imaging and analysis is sufficient to observe robust phenotypes and steady-state changes, the ability to detect transient changes over time and changes that impact only a subpopulation of the cells is imperfect. In contrast, live cell imaging is an eloquent tool that can be used to observe cellular and subcellular processes within a single cell, or cellular population, over time and without the aid of synchronization approaches that may themselves impact cellular behavior1,2,3,4,5,6.
The formation of a bipolar mitotic spindle is essential for the proper chromosome segregation during cell division, resulting in two genetically identical daughter cells. Defects in mitotic spindle structure that corrupt mitotic progression and compromise the fidelity of chromosome segregation can result in catastrophic cell divisions and reduced cell viability. For this reason, mitotic poisons that alter spindle formation are promising therapeutics to limit the rapid proliferation of cancer cells7,8,9. Nevertheless, fixed cell analysis of spindle structure following the addition of mitotic poisons is limited in its ability to assess the dynamic process of spindle formation and may not indicate whether observed changes in spindle structure are permanent or are instead transient and may be overcome to permit successful cell division.
In this protocol, we describe an approach to assess the dynamics of mitosis following spindle perturbations by live cell imaging. Using the hTERT immortalized RPE-1 cell line engineered to express an RFP-tagged Histone 2B to visualize chromatin, together with an EGFP-tagged &#945;-tubulin to visualize microtubules, the timing of metaphase chromosome alignment, anaphase onset, and ultimately mitotic cell fate are assessed using visual cues of chromosome movement, compaction, and nuclear morphology.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.05% Trypsin</td>
			<td>Gibo-Life sciences</td>
			<td>25-510</td>
			<td>A serine protease used to release adherent cells from culture dishes</td>
		</tr>
		<tr>
			<td>15ml centrifuge tubes</td>
			<td>Olympus Plastics</td>
			<td>28-101</td>
			<td></td>
		</tr>
		<tr>
			<td>20x CFI Plan Fluor objective&#160;</td>
			<td>Nikon</td>
			<td></td>
			<td>For use in Live-cell imaging to visualize both bright field and fluorescence</td>
		</tr>
		<tr>
			<td>293T Cells</td>
			<td>ATCC</td>
			<td>CRL-3216</td>
			<td>For use in retroviral transfection; used in step 1.1</td>
		</tr>
		<tr>
			<td>a-tubulin-EGFP&#160;</td>
			<td>Addgene</td>
			<td>various numbers</td>
			<td>Expression vector for alpha tubulin fused to a green fluorescent protein tag; for use in the visualization of tubulin in live-cell imaging: commercially available through addgene and other vendors</td>
		</tr>
		<tr>
			<td>Alisertib</td>
			<td>Selleckchem</td>
			<td>S1133</td>
			<td>Small molecule inhibitor of the mitotic kinase Aurora A. Stock concentration is prepared at 10mM in DMSO, and used at a final concentration of 100nM.</td>
		</tr>
		<tr>
			<td>Blasticidin</td>
			<td>Invitrogen</td>
			<td>A11139-03</td>
			<td>Antibiotic selection agent; used to select for a-tub-EGFP expressing cells</td>
		</tr>
		<tr>
			<td>C02</td>
			<td>Airgas</td>
			<td></td>
			<td>For use in cell culture and live cell imaging</td>
		</tr>
		<tr>
			<td>Chroma ET-DS Red (TRITC/Cy3)</td>
			<td>Chroma</td>
			<td>49005</td>
			<td>Single band filter set; excitation wavelength 545nm with 25nm bandwidth and emission at 605nm wavelength with 70nm bandwidth; for visualization of H2B-RFP</td>
		</tr>
		<tr>
			<td>Chroma ET-EGFP (FITC/Cy2)</td>
			<td>Chroma</td>
			<td>49002</td>
			<td>Single band filter set; excitation wavelength 470nm with 40nm bandwidth and emission at 525nm wavelength with 50nm bandwidth; for visualization of GFP-tubulin</td>
		</tr>
		<tr>
			<td>disposable glass Pastuer pipets, sterilized&#160;</td>
			<td>Fisher Scientific</td>
			<td>13-678-6A</td>
			<td>For use in aspirating cells&#160;</td>
		</tr>
		<tr>
			<td>Dulbecco&#8217;s Modified Eagle Medium (DMEM)</td>
			<td>Gibo-Life sciences</td>
			<td>11965-084</td>
			<td>Cell culture medium for growth of RPE-1 and 293T cells</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum (FBS)</td>
			<td>Gibo-Life sciences</td>
			<td>10438-026</td>
			<td>Cell culture medium supplement</td>
		</tr>
		<tr>
			<td>Lipofectamine 3000 and p3000</td>
			<td>Invitrogen</td>
			<td>L3000-015</td>
			<td>Lipid based transfection reagent for transfection of plasmids; used in 1.1.4</td>
		</tr>
		<tr>
			<td>Multi well Tissue Culture dishes</td>
			<td>Corning</td>
			<td>various</td>
			<td>for use in cell culture, transfection/infection, and live cell imaging</td>
		</tr>
		<tr>
			<td>Nikon Ti-E microscope</td>
			<td>Nikon</td>
			<td></td>
			<td>Inverted epifluorescence microscope for use in live-cell imaging</td>
		</tr>
		<tr>
			<td>NIS Elements HC&#160;</td>
			<td>Nikon</td>
			<td>Version 4.51</td>
			<td>Image acquisition and analysis software; used in sections 3 &#38; 4</td>
		</tr>
		<tr>
			<td>OPTI-MEM</td>
			<td>Gibo-Life sciences</td>
			<td>31985-070</td>
			<td>Reduced serum medium for cell transfection; used in step 1.1.3</td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin&#160;</td>
			<td>Gibo-Life sciences</td>
			<td>15140-122</td>
			<td>antibiotic used in cell culture medium</td>
		</tr>
		<tr>
			<td>phosphate bufferred saline (PBS)</td>
			<td>Caisson labs</td>
			<td>PBP06-10X1LT</td>
			<td>sterile saline solution for use with cell culture</td>
		</tr>
		<tr>
			<td>pMD2.G</td>
			<td>Addgene</td>
			<td>12259</td>
			<td>Lentiviral VSV-G envelope expression construct; used in step 1.1.4</td>
		</tr>
		<tr>
			<td>Polybrene</td>
			<td>Sigma-Aldrich</td>
			<td>H9268</td>
			<td>Cationic polymer used to enhane viral infection efficiency; used in step 1.1.10</td>
		</tr>
		<tr>
			<td>psPAX</td>
			<td>Addgene</td>
			<td>12260</td>
			<td>2nd generation lentiviral packaging plasmid; used in step 1.1.4</td>
		</tr>
		<tr>
			<td>Puromycin</td>
			<td>Invitrogen</td>
			<td>ant-pr-1</td>
			<td>Antibiotic selection agent; used to select for RFP-H2B expressing cells</td>
		</tr>
		<tr>
			<td>RFP- Histone 2B (H2B)</td>
			<td>Addgene</td>
			<td>various numbers</td>
			<td>Expression vector for red fluorescent protein-tagged histone 2B; for use in the visualization of chromatin in live-cell imaging: commercially available through Addgene and other vendors</td>
		</tr>
		<tr>
			<td>RNAi Max</td>
			<td>Invitrogen</td>
			<td>13778-150</td>
			<td>Lipid based transfection reagent for transfection of siRNA constructs</td>
		</tr>
		<tr>
			<td>RPE-1 cells</td>
			<td>ATCC</td>
			<td>CRL-4000</td>
			<td>Human retinal pigment epithelial cell line</td>
		</tr>
		<tr>
			<td>Tissue culture dish 100x20mm</td>
			<td>Corning&#160;</td>
			<td>353003</td>
			<td>for use in culturing adherent cells</td>
		</tr>
		<tr>
			<td>Zyla sCMOS camera&#160;</td>
			<td>Nikon</td>
			<td></td>
			<td>Camera attached to the micrscope, used for capturing images of cells</td>
		</tr>
	</tbody>
</table>

live cell imaging to assess the dynamics of metaphase timing and cell fate following mitotic spindle perturbations

Live cell time-lapse imaging is an important tool in cell biology that provides insight into cellular processes that might otherwise be overlooked, misunderstood, or misinterpreted by the fixed-cell analysis. While the fixed cell imaging and analysis is robust and sufficient to observe cellular steady-state, it can be limited in defining a temporal order of events at the cellular level and is ill-equipped to assess the transient nature of dynamic processes including mitotic progression. In contrast, live cell imaging is an eloquent tool that can be used to observe cellular processes at the single-cell level over time and has the capacity to capture the dynamics of processes that would otherwise be poorly represented in fixed cell imaging. Here we describe an approach to generate cells carrying fluorescently labeled markers of chromatin and microtubules and their use in live cell imaging approaches to monitor metaphase chromosome alignment and mitotic exit. We describe imaging-based techniques to assess the dynamics of spindle formation and mitotic progression, including the identification of cells at various stages in mitosis, identification&#160;and tracking of mitotic defects, and analysis of spindle dynamics and mitotic cell fate following the treatment with mitotic inhibitors.

Assessment of mitotic progression in the presence of spindle perturbations 
The regulation of spindle pole focusing is an essential step in proper bipolar spindle formation. Disruption in this process through protein depletions, drug inhibition, or alterations in centrosome number corrupt spindle structure and delay or halt mitotic progression10,11,12,<sup class="...

Watch this Scientific Journal Video about Live Cell Imaging to Assess the Dynamics of Metaphase Timing and Cell Fate Following Mitotic Spindle Perturbations at JoVE.com

Live Cell Imaging to Assess the Dynamics of Metaphase Timing and Cell Fate Following Mitotic Spindle Perturbations

Here we present a protocol to assess the dynamics of spindle formation and mitotic progression. Our application of time-lapse imaging enables the user to identify cells at various stages of mitosis, track and identify mitotic defects, and analyze spindle dynamics and mitotic cell fate upon exposure to anti-mitotic drugs.

Live cell time-lapse imaging is an important tool in cell biology that provides insight into cellular processes that might otherwise be overlooked, ...

Live cell imaging enables the observation of dynamic cellular processes over time within a single cell. These approaches are powerful for assessing the conditions that impact the dynamic process of cell division and revealing the impacts that defects in mitosis have on daughter cell proliferation and viability. Phototoxicity that results from light exposure during imaging represents a significant challenge associated with this protocol.Therefore, exposure times and the imaging interval and duration should be optimized. Using aseptic technique and a biosafety level two safety cabinet, use a sterile disposable glass Pasteur pipette to aspirate the medium from the culture plate containing the cell line carrying the expression construct of interest. Briefly wash the cells with 10 milliliters of sterile PBS with swirling and treat the cells with two milliliters of 0.05%trypsin.After two to five minutes at 37 degrees Celsius, add eight milliliters of fresh medium to the plate to stop the reaction and resuspend the detached cells with gentle pipetting. Transfer the cell solution to a sterile 15 milliliter tube and collect the cells by centrifugation. Resuspend the pellet in 10 milliliters of PBS and centrifuge the cells again.Resuspend the pellet in 10 milliliters of medium for counting and dilute the cells to a one to two times 10 to the 5th cells per milliliter of cell culture medium concentration. Then seed 500 microliters of cells into each well of a sterile 12-well imaging bottom plate and place the plate in the cell culture incubator to allow the cells to adhere to the plate's surface. No more than 30 minutes prior to imaging, add a relevant concentration of a mitotic drug to one or more of the wells and add an equal volume of the inhibitor diluent to the same number of wells as the controls.To prepare the microscope for imaging, place the plate onto the stage of an inverted epifluorescence microscope equipped with a high resolution camera, an environmental chamber preheated to 37 degrees Celsius and a delivery system for humidified 5%carbon dioxide. Select a 20 times air objective with a numerical aperture of 0.5 and equipped for the high contrast fluorescence and phase contrast, or bright field imaging and view the cells to adjust the course and find focus to bring cells into focus. To set the optimal exposure times for bright field, GFP, and RFP image acquisition, select the respective filter cubes with the appropriate excitation and emission for the fluorophores that will be imaged and click Play.If the signal is not sufficiently intense, adjust the auto exposure and in each fluorophore channel select the appropriate binning from the Format dropdown menu. Select and calibrate the microscope stage to the multi-well dish according to the manufacturer's instructions and use the image acquisition software to highlight or otherwise select the wells that will be imaged. Open the generated points control panel and under Working Area select Restricted and Border to restrict the coordinate selection area to exclude the boundaries of the well.In the Area Restriction dropdown menu, select Whole Area and select a random point placement. Set the count to six and click Randomize to select the number and distribution of the points to be captured per well, respectively. Then click on and enter the values in the time sequence control panel to select and input the time interval and the duration for collecting the images.To visualize the RFP-H2B labeled chromatin, select the images captured with the RFP filter cube in place and identify a cell entering mitosis as indicated by the initial chromatin compaction and nuclear envelope breakdown to determine the mitotic timing of the metaphase alignment and anaphase onset in individual cells. Track the cell of interest through consecutive time points in the acquired movie to determine the number of time points or minutes from mitotic entry until RFP-H2B labeled chromatin completes the alignment at the cell equator during metaphase. To monitor the mitotic timing, mitotic fidelity, and cell fate, continue to track the cell through consecutive time points to identify the time coordinate at which anaphase chromosome segregation is apparent and/or when chromatin decompaction and nuclear envelope reformation has occurred.Then visualize RFP-H2B to identify cells in each population that exhibit mitotic defects, including lagging chromosomes and chromatin bridges during anaphase chromosome segregation. By visualizing alpha tubulin-EGFP, it can be observed that cells that experience spindle disruption undergo dynamic changes as spindle pull focusing is achieved and a bipolar mitotic spindle is formed in preparation for cell division. Concurrent with spindle assembly, chromosome movement can be visualized with RFP-H2B to assess the chromosome alignment and segregation fidelity.Using live cell imaging approaches, these representative results show that cells with a normal centrosome content are able to proceed from nuclear envelope breakdown through metaphase alignment and anaphase onset to achieve a bipolar division in under 30 minutes. In the presence of extra centrosomes, nearly 50%of the cells are able to overcome a transient multipolar mitotic spindle and to form a bipolar spindle in complete cell division. The remaining cells are unable to achieve a bipolar spindle and as a result, exit mitosis through a multipolar division.Regardless of whether spindle bipolarity is achieved, cells with extra centrosomes exhibit a significantly increased duration of mitosis compared to cells with two centrosomes. Indicating that the dynamics of mitotic progression may be altered even when changes in mitotic outcome are not apparent. When defining exposure times for fluorescent channels, optimize the exposure times to limit phototoxicity.Also camera pixel binning can be selected to allow lower exposure times to be used. This procedure has applications in pharmacological screenings, invasion, and migration analysis. These approaches can also be employed to examine the efficacy of drug treatments or the dynamics of cellular motility.

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Unit 2

Cell Proliferation

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Live Cell Imaging of F-actin Dynamics via Fluorescent Speckle Microscopy (FSM)

In this protocol we describe the use of Fluorescent Speckle Microscopy (FSM) to capture high-resolution images of actin dynamics in PtK1 cells. A unique advantage of FSM is its ability to capture the movement and turnover kinetics (assembly/disassembly) of the F-actin network within living cells. This technique is particularly useful in deriving quantitative measurements of F-actin dynamics when paired with computer vision software (qFSM).  We describe  the selection, microinjection and visualization of fluorescent actin probes in living cells. Importantly, similar procedures are applicable to visualizing other macomolecular assemblies. FSM has been demonstrated for microtubules, intermediate filaments, and adhesion complexes.  

Live Cell Imaging of F-actin Dynamics via Fluorescent Speckle Microscopy FSM

Selection, microinjection, and imaging of fluorescently-labeled F-actin via fluorescent speckle microscopy (FSM).

In this protocol we describe the use of Fluorescent Speckle Microscopy (FSM) to capture high-resolution images of actin dynamics in PtK1 cells. A unique ...

Assembly, Loading, and Alignment of an Analytical Ultracentrifuge Sample Cell

The analytical ultracentrifuge (AUC) is a powerful biophysical tool that allows us to record macromolecular sedimentation profiles during high speed centrifugation. When properly planned and executed, an AUC sedimentation velocity or sedimentation equilibrium experiment can reveal a great deal about a protein in regards to size and shape, sample purity, sedimentation coefficient, oligomerization states and protein-protein interactions.
This technique, however, requires a rigorous level of technical attention. Sample cells hold a sectored center piece sandwiched between two window assemblies. They are sealed with a torque pressure of around 120-140 in/lbs. Reference buffer and sample are loaded into the centerpiece sectors and then after sealing, the cells are precisely aligned into a titanium rotor so that the optical detection systems scan both sample and reference buffer in the same radial path midline through each centerpiece sector while rotating at speeds of up to 60, 000 rpm and under very high vacuum
Not only is proper sample cell assembly critical, sample cell components are very expensive and must be properly cared for to ensure they are in optimum working condition in order to avoid leaks and breakage during experiments. Handle windows carefully, for even the slightest crack or scratch can lead to breakage in the centrifuge. The contact between centerpiece and windows must be as tight as possible; i.e. no Newton s rings should be visible after torque pressure is applied. Dust, lint, scratches and oils on either the windows or the centerpiece all compromise this contact and can very easily lead to leaking of solutions from one sector to another or leaking out of the centerpiece all together. Not only are precious samples lost, leaking of solutions during an experiment will cause an imbalance of pressure in the cell that often leads to broken windows and centerpieces. In addition, plug gaskets and housing plugs must be securely in place to avoid solutions being pulled out of the centerpiece sector through the loading holes by the high vacuum in the centrifuge chamber. Window liners and gaskets must be free of breaks and cracks that could cause movement resulting in broken windows.
This video will demonstrate our procedures of sample cell assembly, torque, loading and rotor alignment to help minimize component damage, solution leaking and breakage during the perfect AUC experiment.

The analytical ultracentrifuge (AUC) sample cell holds sample and reference buffer and during experiments and is exposed to high vacuum and rotor speeds up to 60,000 rpm. This video will demonstrate the rigorous attention to detail necessary for assembly, loading and alignment of this very important component of an AUC experiment.

The analytical ultracentrifuge (AUC) is a powerful biophysical tool that allows us to record macromolecular sedimentation profiles during high speed ...

Single Cell Fate Mapping in Zebrafish

The ability to differentially label single cells has important implications in developmental biology. For instance, determining how hematopoietic, lymphatic, and blood vessel lineages arise in developing embryos requires fate mapping and lineage tracing of undifferentiated precursor cells. Recently, photoactivatable proteins which include: Eos1, 2, PAmCherry3, Kaede4-7, pKindling8, and KikGR9, 10 have received wide interest as cell tracing probes. The fluorescence spectrum of these photosensitive proteins can be easily converted with UV excitation, allowing a population of cells to be distinguished from adjacent ones. However, the photoefficiency of the activated protein may limit long-term cell tracking11. As an alternative to photoactivatable proteins, caged fluorescein-dextran has been widely used in embryo model systems7, 12-14. Traditionally, to uncage fluorescein-dextran, UV excitation from a fluorescence lamp house or a single photon UV laser has been used; however, such sources limit the spatial resolution of photoactivation. Here we report a protocol to fate map, lineage trace, and detect single labeled cells. Single cells in embryos injected with caged fluorescein-dextran are photoactivated with near-infrared laser pulses produced from a titanium sapphire femtosecond laser. This laser is customary in all two-photon confocal microscopes such as the LSM 510 META NLO microscope used in this paper. Since biological tissue is transparent to near-infrared irradiation15, the laser pulses can be focused deep within the embryo without uncaging cells above or below the selected focal plane. Therefore, non-linear two-photon absorption is induced only at the geometric focus to uncage fluorescein-dextran in a single cell. To detect the cell containing uncaged fluorescein-dextran, we describe a simple immunohistochemistry protocol16 to rapidly visualize the activated cell. The activation and detection protocol presented in this paper is versatile and can be applied to any model system. 
Note: The reagents used in this protocol can be found in the table appended at the end of the article.

A method is described to photoactivate single cells containing a caged fluorescent protein using two-photon absorption from a Ti:Sapphire femtosecond laser oscillator. To fate map the photoactivated cell, immunohistochemistry is used. This technique can be applied to any cell type.

The ability to differentially label single cells has important implications in developmental biology. For instance, determining how hematopoietic, ...

Blastomere Explants to Test for Cell Fate Commitment During Embryonic Development

Fate maps, constructed from lineage tracing all of the cells of an embryo, reveal which tissues descend from each cell of the embryo. Although fate maps are very useful for identifying the precursors of an organ and for elucidating the developmental path by which the descendant cells populate that organ in the normal embryo, they do not illustrate the full developmental potential of a precursor cell or identify the mechanisms by which its fate is determined. To test for cell fate commitment, one compares a cell's normal repertoire of descendants in the intact embryo (the fate map) with those expressed after an experimental manipulation. Is the cell's fate fixed (committed) regardless of the surrounding cellular environment, or is it influenced by external factors provided by its neighbors? Using the comprehensive fate maps of the Xenopus embryo, we describe how to identify, isolate and culture single cleavage stage precursors, called blastomeres. This approach allows one to assess whether these early cells are committed to the fate they acquire in their normal environment in the intact embryo, require interactions with their neighboring cells, or can be influenced to express alternate fates if exposed to other types of signals.

The fate of an individual embryonic cell can be influenced by inherited molecules and/or by signals from neighboring cells. Utilizing fate maps of the cleavage stage Xenopus embryo, single blastomeres can be identified for culture in isolation to assess the contributions of inherited molecules versus cell-cell interactions.

Fate maps, constructed from lineage tracing all of the cells of an embryo, reveal  which tissues descend from each cell of the embryo.  Although fate maps ...

Live Imaging of Apoptotic Cell Clearance during Drosophila Embryogenesis

The proper elimination of unwanted or aberrant cells through apoptosis and subsequent phagocytosis (apoptotic cell clearance) is crucial for normal development in all metazoan organisms. Apoptotic cell clearance is a highly dynamic process intimately associated with cell death; unengulfed apoptotic cells are barely seen in vivo under normal conditions. In order to understand the different steps of apoptotic cell clearance and to compare 'professional' phagocytes - macrophages and dendritic cells to 'non-professional' - tissue-resident neighboring cells, in vivo live imaging of the process is extremely valuable. Here we describe a protocol for studying apoptotic cell clearance in live Drosophila embryos. To follow the dynamics of different steps in phagocytosis we use specific markers for apoptotic cells and phagocytes. In addition, we can monitor two phagocyte systems in parallel: 'professional' macrophages and 'semi-professional' glia in the developing central nervous system (CNS). The method described here employs the Drosophila embryo as an excellent model for real time studies of apoptotic cell clearance.

Live Imaging of Apoptotic Cell Clearance during Drosophila Embryogenesis

Here we describe an effective method for studying dynamics of apoptotic cell clearance in vivo. This method employs live Drosophila embryos as a powerful model for monitoring phagocytosis of apoptotic cells using specific labeling of apoptotic cells and phagocytes.

The  proper elimination of unwanted or aberrant cells through apoptosis and  subsequent phagocytosis (apoptotic cell clearance) is crucial for normal  ...

Live Cell Imaging of Early Autophagy Events: Omegasomes and Beyond

Autophagy is a cellular response triggered by the lack of nutrients, especially the absence of amino acids. Autophagy is defined by the formation of double membrane structures, called autophagosomes, that sequester cytoplasm, long-lived proteins and protein aggregates, defective organelles, and even viruses or bacteria. Autophagosomes eventually fuse with lysosomes leading to bulk degradation of their content, with the produced nutrients being recycled back to the cytoplasm. Therefore, autophagy is crucial for cell homeostasis, and dysregulation of autophagy can lead to disease, most notably neurodegeneration, ageing and cancer.	
	Autophagosome formation is a very elaborate process, for which cells have allocated a specific group of proteins, called the core autophagy machinery. The core autophagy machinery is functionally complemented by additional proteins involved in diverse cellular processes, e.g. in membrane trafficking, in mitochondrial and lysosomal biology. Coordination of these proteins for the formation and degradation of autophagosomes constitutes the highly dynamic and sophisticated response of autophagy. Live cell imaging allows one to follow the molecular contribution of each autophagy-related protein down to the level of a single autophagosome formation event and in real time, therefore this technique offers a high temporal and spatial resolution.	
	Here we use a cell line stably expressing GFP-DFCP1, to establish a spatial and temporal context for our analysis. DFCP1 marks omegasomes, which are precursor structures leading to autophagosomes formation. A protein of interest (POI) can be marked with either a red or cyan fluorescent tag. Different organelles, like the ER, mitochondria and lysosomes, are all involved in different steps of autophagosome formation, and can be marked using a specific tracker dye. Time-lapse microscopy of autophagy in this experimental set up, allows information to be extracted about the fourth dimension, i.e. time. Hence we can follow the contribution of the POI to autophagy in space and time.

Time-lapse microscopy of fluorescently labeled autophagy markers allows monitoring of the dynamic autophagy response with high temporal resolution. Using specific autophagy and organelle markers in a combination of 3 different colors, we can follow the contribution of a protein to autophagosome formation in a robust spatial and temporal context.

Autophagy is a  cellular response triggered by the lack of nutrients, especially the absence of  amino acids. Autophagy is defined by the formation of ...

Live Cell Imaging of Primary Rat Neonatal Cardiomyocytes Following Adenoviral and Lentiviral Transduction Using Confocal Spinning Disk Microscopy

Primary rat neonatal cardiomyocytes are useful in basic in vitro cardiovascular research because they can be easily isolated in large numbers in a single procedure. Due to advances in microscope technology it is relatively easy to capture live cell images for the purpose of investigating cellular events in real time with minimal concern regarding phototoxicity to the cells. This protocol describes how to take live cell timelapse images of primary rat neonatal cardiomyocytes using a confocal spinning disk microscope following lentiviral and adenoviral transduction to modulate properties of the cell. The application of two different types of viruses makes it easier to achieve an appropriate transduction rate and expression levels for two different genes. Well focused live cell images can be obtained using the microscope&#8217;s autofocus system, which maintains stable focus for long time periods. Applying this method, the functions of exogenously engineered proteins expressed in cultured primary cells can be analyzed. Additionally, this system can be used to examine the functions of genes through the use of siRNAs as well as of chemical modulators.

This protocol describes a method of live cell imaging using primary rat neonatal cardiomyocytes following lentiviral and adenoviral transduction using confocal spinning disk microscopy. This enables detailed observations of cellular processes in living cardiomyocytes.

Primary rat neonatal cardiomyocytes are useful in basic in vitro cardiovascular research because they can be easily isolated in large numbers in a single ...

Studying the Protein Quality Control System of D. discoideum Using Temperature-controlled Live Cell Imaging

The complex lifestyle of the social amoebae Dictyostelium discoideum makes it a valuable model for the study of various biological processes. Recently, we showed that D. discoideum is remarkably resilient to protein aggregation and can be used to gain insights into the cellular protein quality control system. However, the use of D. discoideum as a model system poses several challenges to microscopy-based experimental approaches, such as the high motility of the cells and their susceptibility to photo-toxicity. The latter proves to be especially challenging when studying protein homeostasis, as the phototoxic effects can induce a cellular stress response and thus alter to behavior of the protein quality control system. 
Temperature increase is a commonly used way to induce cellular stress. Here, we describe a temperature-controllable imaging protocol, which allows observing temperature-induced perturbations in D. discoideum. Moreover, when applied at normal growth temperature, this imaging protocol can also noticeably reduce photo-toxicity, thus allowing imaging with higher intensities. This can be particularly useful when imaging proteins with very low expression levels. Moreover, the high mobility of the cells often requires the acquisition of multiple fields of view to follow individual cells, and the number of fields needs to be balanced against the desired time interval and exposure time.

Studying the Protein Quality Control System of D. discoideum Using Temperature-controlled Live Cell Imaging

The social amoebae Dictyostelium discoideum has recently been established as a system to study protein misfolding and proteostasis. Here, we describe a new imaging-based methodology to study temperature-induced protein aggregation and the cellular stress response in D. discoideum.

The complex lifestyle of the social amoebae Dictyostelium discoideum makes it a valuable model for the study of various biological processes. Recently, we ...

Examination of Mitotic and Meiotic Fission Yeast Nuclear Dynamics by Fluorescence Live-cell Microscopy

Live-cell imaging is a microscopy technique used to examine cell and protein dynamics in living cells. This imaging method is not toxic, generally does not interfere with cell physiology, and requires minimal experimental handling. The low levels of technical interference enable researchers to study cells across multiple cycles of mitosis and to observe meiosis from beginning to end. Using fluorescent tags such as Green Fluorescent Protein (GFP) and Red Fluorescent Protein (RFP), researchers can analyze different factors whose functions are important for processes like transcription, DNA replication, cohesion, and segregation. Coupled with data analysis using Fiji (a free, optimized ImageJ version), live-cell imaging offers various ways of assessing protein movement, localization, stability, and timing, as well as nuclear dynamics and chromosome segregation. However, as is the case with other microscopy methods, live-cell imaging is limited by the intrinsic properties of light, which put a limit to the resolution power at high magnifications, and is also sensitive to photobleaching or phototoxicity at high wavelength frequencies. However, with some care, investigators can bypass these physical limitations by carefully choosing the right conditions, strains, and fluorescent markers to allow for the appropriate visualization of mitotic and meiotic events.

Here, we present live-cell imaging which is a non-toxic microscopy method that allows researchers to study protein behavior and nuclear dynamics in living fission yeast cells during mitosis and meiosis.

Live-cell imaging is a microscopy technique used to examine cell and protein dynamics in living cells. This imaging method is not toxic, generally does ...

Super-Resolution Live Cell Imaging of Subcellular Structures

There has long been a crucial tradeoff between spatial and temporal resolution in imaging. Imaging beyond the diffraction limit of light has traditionally been restricted to be used only on fixed samples or live cells outside of tissue labeled with strong fluorescent signal. Current super-resolution live cell imaging techniques require the use of special fluorescence probes, high illumination, multiple image acquisitions with post-acquisition processing, or often a combination of these processes. These prerequisites significantly limit the biological samples and contexts that this technique can be applied to.
Here we describe a method to perform super-resolution (~140 nm XY-resolution) time-lapse fluorescence live cell imaging in situ. This technique is also compatible with low fluorescent intensity, for example, EGFP or mCherry endogenously tagged at lowly expressed genes. As a proof-of-principle, we have used this method to visualize multiple subcellular structures in the Drosophila testis. During tissue preparation, both the cellular structure and tissue morphology are maintained within the dissected testis. Here, we use this technique to image microtubule dynamics, the interactions between microtubules and the nuclear membrane, as well as the attachment of microtubules to centromeres.
This technique requires special procedures in sample preparation, sample mounting and immobilizing of specimens. Additionally, the specimens must be maintained for several hours after dissection without compromising cellular function and activity. While we have optimized the conditions for live super-resolution imaging specifically in Drosophila male germline stem cells (GSCs) and progenitor germ cells in dissected testis tissue, this technique is broadly applicable to a variety of different cell types. The ability to observe cells under their physiological conditions without sacrificing either spatial or temporal resolution will serve as an invaluable tool to researchers seeking to address crucial questions in cell biology.

Presented here is a protocol for super-resolution live-cell imaging in intact tissue. We have standardized the conditions for imaging a highly sensitive adult stem cell population in its native tissue environment. This technique involves balancing temporal and spatial resolution to allow for the direct observation of biological phenomena in live tissue.

There has long been a crucial tradeoff between spatial and temporal resolution in imaging. Imaging beyond the diffraction limit of light has traditionally ...