Name: imaging intermediate filaments and microtubules with 2-dimensional direct stochastic optical reconstruction microscopy
Uploaded: 2018-03-06T13:30:00
Description: Watch this Scientific Journal Video about Imaging Intermediate Filaments and Microtubules with 2-dimensional Direct Stochastic Optical Reconstruction Microscopy at JoVE.com

We thank Mickael Lelek, Orestis Faklaris and Nicolas Bourg for fruitful discussion, Andrey Aristov and Elena Rensen for help with the super-resolution technique and Shailaja Seetharaman for careful reading of the manuscript. We gratefully acknowledge the UtechS Photonic BioImaging (Imagopole) Citech of Institut Pasteur (Paris, France) as well as the France-BioImaging infrastructure network supported by the French National Research Agency (ANR-10-INSB-04; Investments for the Future), and the R&#233;gion Ile-de-France (program Domaine d'Int&#233;r&#234;t Majeur-Malinf) for the use of the Elyra microscope. This work was supported by the the Ligue Contre le Cancer and the French National Research Agency (ANR-16-CE13-0019).

1. Coverslips preparation (Day 1, 30 min)
<ol>
	<li>Place the 18-mm n&#186;1.5H (170 &#181;m +/- 5&#181;m) glass coverslips on a plastic rack.</li>
	<li>Put the rack in a 100-mL beaker filled with acetone and soak for 5 min.</li>
	<li>Transfer the rack to a 100-mL beaker filled with absolute ethanol and soak for 5 min.</li>
	<li>Transfer the rack to a new 100 mL beaker filled with absolute ethanol and place the beaker in an ultrasonic cleaner device (see Table of materials) at room temperature. Press &#34;on&#34; and w...

<ol>
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T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+user's+guide+to+localization-based+super-resolution+fluorescence+imaging.">A user's guide to localization-based super-resolution fluorescence imaging.</a> Methods Cell Biol. 114, 561-592 (2013).</li><li>van de Linde, 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=Direct+stochastic+optical+reconstruction+microscopy+with+standard+fluorescent+probes.">Direct stochastic optical reconstruction microscopy with standard fluorescent probes.</a> Nat Protoc. 6 (7), 991-1009 (2011).</li><li>Chazeau, A., Katrukha, E. A., Hoogenraad, C. C., Kapitein, L. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Studying+neuronal+microtubule+organization+and+microtubule-associated+proteins+using+single+molecule+localization+microscopy.">Studying neuronal microtubule organization and microtubule-associated proteins using single molecule localization microscopy.</a> Methods Cell Biol. 131, 127-149 (2016).</li><li>Olivier, N., Keller, D., Rajan, V. S., Gonczy, P., Manley, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simple+buffers+for+3D+STORM+microscopy.">Simple buffers for 3D STORM microscopy.</a> Biomed Opt Express. 4 (6), 885-899 (2013).</li><li>Eliasson, C., 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=Intermediate+filament+protein+partnership+in+astrocytes.">Intermediate filament protein partnership in astrocytes.</a> J Biol Chem. 274 (34), 23996-24006 (1999).</li><li>Leduc, C., Etienne-Manneville, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+microtubule-associated+motors+drives+intermediate+filament+network+polarization.">Regulation of microtubule-associated motors drives intermediate filament network polarization.</a> J Cell Biol. 216 (6), 1689-1703 (2017).</li><li>Gan, Z., 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=Vimentin+Intermediate+Filaments+Template+Microtubule+Networks+to+Enhance+Persistence+in+Cell+Polarity+and+Directed+Migration.">Vimentin Intermediate Filaments Template Microtubule Networks to Enhance Persistence in Cell Polarity and Directed Migration.</a> Cell Syst. 3 (5), 500-501 (2016).</li><li>Nieuwenhuizen, R. 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K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glial+fibrillary+acidic+protein:+from+intermediate+filament+assembly+and+gliosis+to+neurobiomarker.">Glial fibrillary acidic protein: from intermediate filament assembly and gliosis to neurobiomarker.</a> Trends Neurosci. 38 (6), 364-374 (2015).</li><li>Maslehaty, H., Cordovi, S., Hefti, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Symptomatic+spinal+metastases+of+intracranial+glioblastoma:+clinical+characteristics+and+pathomechanism+relating+to+GFAP+expression.">Symptomatic spinal metastases of intracranial glioblastoma: clinical characteristics and pathomechanism relating to GFAP expression.</a> J Neurooncol. 101 (2), 329-333 (2011).</li><li>Hol, E. M., Pekny, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glial+fibrillary+acidic+protein+(GFAP)+and+the+astrocyte+intermediate+filament+system+in+diseases+of+the+central+nervous+system.">Glial fibrillary acidic protein (GFAP) and the astrocyte intermediate filament system in diseases of the central nervous system.</a> Curr Opin Cell Biol. 32, 121-130 (2015).</li><li>Skalli, O., 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=Astrocytoma+grade+IV+(glioblastoma+multiforme)+displays+3+subtypes+with+unique+expression+profiles+of+intermediate+filament+proteins.">Astrocytoma grade IV (glioblastoma multiforme) displays 3 subtypes with unique expression profiles of intermediate filament proteins.</a> Hum Pathol. 44 (10), 2081-2088 (2013).</li><li>Endesfelder, U., Malkusch, S., Fricke, F., Heilemann, 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+simple+method+to+estimate+the+average+localization+precision+of+a+single-molecule+localization+microscopy+experiment.">A simple method to estimate the average localization precision of a single-molecule localization microscopy experiment.</a> Histochem Cell Biol. 141 (6), 629-638 (2014).</li><li>Whelan, D. R., Bell, T. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Image+artifacts+in+single+molecule+localization+microscopy:+why+optimization+of+sample+preparation+protocols+matters.">Image artifacts in single molecule localization microscopy: why optimization of sample preparation protocols matters.</a> Sci Rep. 5, 7924 (2015).</li><li>Ovesny, M., Krizek, P., Borkovec, J., Svindrych, Z., Hagen, G. 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Critical steps in the protocol
We present here a protocol which minimizes artifacts in the dSTORM images of microtubules and IFs in glial cells. Artifacts can be created at every step of the sample preparation and imaging: fixation, blocking, immunolabeling, drift during acquisition, non-optimal blinking conditions23. We list below the most critical steps.
Cleaning the coverslips is an important step to limit the non-specific...

Cytoplasmic intermediate filaments (IFs) are 10 nm-diameter homo- or heteropolymers of a cell type specific subset of IF proteins. IFs participate in a large range of cellular functions such as cell motility, proliferation and stress responses. Their key role is highlighted by the fact that more than 90 human diseases are directly caused by mutations in IF proteins; for instance, changes in IF composition accompanies tumour growth and spreading1,2,3. There is growing evidence that the three cytoskeleton systems work in collaboration to control cellular functions such as cell polarization, division and migration2,3. Since there is a tight coupling between spatial architecture and functions, it is crucial to get insights into the structural organization of the IF with the other filaments and better understand the cytoskeletal cross-talk. this article provides a protocol to perform the super-resolution technique dual-color dSTORM (direct STochastic Optical Reconstruction Microscopy)4 and how it is used to investigate the interaction between IF and microtubules in fixed, cultured cells in 2 dimensions (2D).
Several super-resolution techniques have been developed over the past decade, and there discoveries were at the origin of the Nobel Prize in Chemistry in 20145. Among all these techniques lies the single molecule localization-based methods like PALM6 (Photo-Activated Localization Microscopy) which uses photoswitchable fluorescent proteins, STORM7 with pairs of fluorophores or dSTORM4 with conventional fluorophores. All these methods are based on the same principle which consists of (i) the switch of most of the fluorescent reporters into an &#34;off&#34; state&#34; (non-fluorescent), (ii) the stochastic activation of a subset of them into a fluorescent state in order to localize their spatial position with nanometer accuracy, and (iii) the repetition of this process in order to activate as many subsets of fluorophores as possible. A final image is reconstructed using all the localizations of the activated molecules, providing a lateral resolution down to ~20-40 nm. Several commercialized optical systems allowing PALM/STORM are now available for biologists for routine experiments. Here, one such system was used to study the structural association of microtubules and IFs. Among all the single-molecule localization-based methods, the dual-color dSTORM technique was selected, because it is well suited to observe very thin lamellar regions (&#60;1 &#181;m) of adherent cells and can provide significant improvement of image resolution with minimal time and money investment. Indeed, dSTORM is a very convenient and versatile technique that is compatible with the standard organic dyes routinely used for cellular staining and immunofluorescence.
While one color dSTORM images are relatively simple to obtain using the fluorophore Alexa6478, dual color dSTORM requires to optimize the experimental conditions so that two dyes can blink properly in the chosen buffer, especially when there is limited laser power. Excellent papers are already available on the methods to set up multi-color imaging with dSTORM9,10,11,12,13, and these papers explain in detail the possible sources of artifacts and degraded image resolution as well as how to overcome them. In this article, the optimal experimental conditions in terms of cells fixation, immunostaining, sample preparation, imaging acquisition and image reconstruction are described in order to acquire images of dense cytoplasmic IF networks and microtubules in glial cells with dual-color dSTORM. Briefly, the extraction/fixation method described in Chazeau et al12 was adapted to glial cells and used with a post-fixation step, optimized antibodies concentration, a STORM buffer with 10 mM MEA described in Dempsey9 et al. which was found to be optimal for the experimental set up and sample type.
Glial cells mainly express three types of IF proteins: vimentin, nestin and GFAP (glial acidic fibrillary protein). These three proteins were shown to co-polymerize in astrocytes14. We previously showed using super-resolution structured illumination microscopy (SR SIM) that these three IF proteins can be found in the same single IF filament and that they display similar distribution and dynamics in glial cells 15. Due to the similarities between the three IF proteins, vimentin staining was used as a reporter for the whole IF network. Using dSTORM, we managed to resolve how IF form bundles along microtubules, which was not possible with diffraction limited microscopy techniques15. These observations may help to understand how vimentin IFs can template microtubules and regulate their growth trajectory, promoting the maintenance of a polarity axis during cell migration16. Super-resolution images provided key information on the mutual interaction of the two cytoskeletal subsystems, and brought insight into the link between spatial association and local function which could be cell-type specific17. In general, dual-color dSTORM can be used to study the crosstalk between cytoskeletal elements or other types of organelles, provided that good immunostaining conditions are reached in terms of density and specificity. This technique will be useful to better characterize the cytoskeleton changes observed during astrogliosis and in glioblastoma, the most common and most malignant tumor of the central nervous system, where the expression of IF proteins is altered 18,19,20,21.

<table>
	<tbody>
		<tr>
			<td>Minimum Essential Media (MEM)</td>
			<td>Gibco</td>
			<td>41090-028</td>
			<td>cell culture</td>
		</tr>
		<tr>
			<td>non essential amino acid</td>
			<td>Gibco</td>
			<td>1140-050</td>
			<td>cell culture 1/100e</td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin</td>
			<td>Gibco</td>
			<td>15140-122</td>
			<td>cell culture 1/100e</td>
		</tr>
		<tr>
			<td>F&#339;tal Bovine Serum</td>
			<td>Gibco</td>
			<td>10270-106</td>
			<td>cell culture 1/10e</td>
		</tr>
		<tr>
			<td>0,05 % Trypsin-EDTA (1X)</td>
			<td>Gibco</td>
			<td>25300-054</td>
			<td>cell culture</td>
		</tr>
		<tr>
			<td>PBS 10x</td>
			<td>fischer scientific</td>
			<td>11540486</td>
			<td>cell culture</td>
		</tr>
		<tr>
			<td>coverslip 18 mm n&#176;1,5H</td>
			<td>Marienfield/Dominic dutsher</td>
			<td>900556</td>
			<td>coverslips</td>
		</tr>
		<tr>
			<td>paraformaldehyde (PFA) solution</td>
			<td>Sigma</td>
			<td>F8775</td>
			<td>cell fixation</td>
		</tr>
		<tr>
			<td>glutaraldehyde</td>
			<td>Sigma</td>
			<td>G5882</td>
			<td>cell fixation</td>
		</tr>
		<tr>
			<td>triton X100</td>
			<td>Sigma</td>
			<td>T9284</td>
			<td>non ionic surfactant. Used for cell fixation</td>
		</tr>
		<tr>
			<td>sodium borohydride (NaBH4)</td>
			<td>Sigma</td>
			<td>452904-25ML</td>
			<td>cell fixation</td>
		</tr>
		<tr>
			<td>BSA</td>
			<td>Sigma</td>
			<td>A7906</td>
			<td>sample passivation 3% in PBS</td>
		</tr>
		<tr>
			<td>Monoclonal Anti-Vimentin (V9) antibody produced in mouse</td>
			<td>Sigma</td>
			<td>V6630</td>
			<td>primary antibodies</td>
		</tr>
		<tr>
			<td>Rat anti alpha tubulin</td>
			<td>Biorad</td>
			<td>MCA77G</td>
			<td>primary antibodies</td>
		</tr>
		<tr>
			<td>Goat anti-Rat IgG (H+L) Secondary Antibody, Alexa Fluor 555</td>
			<td>Fisher scientific</td>
			<td>10635923</td>
			<td>secondary antibodies</td>
		</tr>
		<tr>
			<td>Donkey anti-Mouse IgG (H+L) Secondary Antibody, Alexa Fluor 647</td>
			<td>Fisher scientific</td>
			<td>10226162</td>
			<td>secondary antibodies</td>
		</tr>
		<tr>
			<td>TetraSpeck Microspheres, 0.1 &#181;m, fluorescent blue/green/orange/dark red</td>
			<td>Fisher scientific</td>
			<td>T7279</td>
			<td>fluorescent beads</td>
		</tr>
		<tr>
			<td>Chamlide magnetic chamber</td>
			<td>Live Cell Instrument</td>
			<td>CM-B18-1</td>
			<td>magnetic sample holder, maximum volume 1,2 mL</td>
		</tr>
		<tr>
			<td>Cysteamine (MEA)</td>
			<td>Sigma</td>
			<td>30070</td>
			<td>for the blinking buffer</td>
		</tr>
		<tr>
			<td>glucose oxidase from Aspergillus niger</td>
			<td>Sigma</td>
			<td>G0543</td>
			<td>for the blinking buffer</td>
		</tr>
		<tr>
			<td>glucose</td>
			<td>sigma</td>
			<td></td>
			<td>for the blinking buffer</td>
		</tr>
		<tr>
			<td>catalase from bovine liver</td>
			<td>Sigma</td>
			<td>C9322</td>
			<td>for the blinking buffer</td>
		</tr>
		<tr>
			<td>Tris (trizma)</td>
			<td>Sigma</td>
			<td>T1503</td>
			<td>for the blinking buffer</td>
		</tr>
		<tr>
			<td>Wash-N-Dry&#160;coverslip rack</td>
			<td>Sigma</td>
			<td>Z688568</td>
			<td></td>
		</tr>
		<tr>
			<td>Parafilm</td>
			<td>Sigma</td>
			<td>P7793-1EA</td>
			<td>paraffin film</td>
		</tr>
		<tr>
			<td>ultrasonic cleaner</td>
			<td>Fisher scientific</td>
			<td>15-335-6</td>
			<td></td>
		</tr>
		<tr>
			<td>plasma cleaner</td>
			<td>Harrick plasma</td>
			<td>PDC-32G-2</td>
			<td></td>
		</tr>
	</tbody>
</table>

imaging intermediate filaments and microtubules with 2-dimensional direct stochastic optical reconstruction microscopy

The cytoskeleton, composed of actin microfilaments, microtubules, and intermediate filaments (IF), plays a key role in the control of cell shape, polarity, and motility. The organization of the actin and microtubule networks has been extensively studied but that of IFs is not yet fully characterized. IFs have an average diameter of 10 nm and form a network extending throughout the cell cytoplasm. They are physically associated with actin and microtubules through molecular motors and cytoskeletal linkers. This tight association is at the heart of the regulatory mechanisms that ensure the coordinated regulation of the three cytoskeletal networks required for most cell functions. It is therefore crucial to visualize IFs alone and also together with each of the other cytoskeletal networks. However, IF networks are extremely dense in most cell types, especially in glial cells, which makes its resolution very difficult to achieve with standard fluorescence microscopy (lateral resolution of ~250 nm). Direct STochastic Optical Reconstruction Microscopy (dSTORM) is a technique allowing a gain in lateral resolution of one order of magnitude. Here, we show that lateral dSTORM resolution is sufficient to resolve the dense organization of the IF networks and, in particular, of IF bundles surrounding microtubules. Such tight association is likely to participate in the coordinated regulation of these two networks and may, explain how vimentin IFs template and stabilize microtubule organization as well as could influence microtubule dependent vesicular trafficking. More generally, we show how the observation of two cytoskeletal components with dual-color dSTORM technique brings new insight into their mutual interaction.

A microscope equipped with 50 mW 405 nm and 100 mW 488, 561 and 642 nm solid-state lasers, an EMCCD 512x512 camera, an alpha Plan Apo 100X/1.46 objective and Band Pass 570-650 / Long Pass 655 emission filters was used for the representative results presented below.
Figure 1A gives an example of molecule density and signal to noise ratio that should be used during raw image acquisition. Good quality ...

Watch this Scientific Journal Video about Imaging Intermediate Filaments and Microtubules with 2-dimensional Direct Stochastic Optical Reconstruction Microscopy at JoVE.com

Imaging Intermediate Filaments and Microtubules with 2-dimensional Direct Stochastic Optical Reconstruction Microscopy

The overall goal of this methodology is to give the optimal experimental conditions from sample preparation to image acquisition and reconstruction in order to perform 2D dual color dSTORM images of microtubules and intermediate filaments in fixed cells

The cytoskeleton, composed of actin microfilaments, microtubules, and intermediate filaments (IF), plays a key role in the control of cell shape, ...

The overall goal of this methodology is to create the optimal experimental conditions from sample preparation to image acquisition and reconstruction in order to perform 2D dual-colored D-STORM imaging of microtubules and intermediate filaments in fixed cells. This method can help characterize the physical interactions between dense and complex cytoskeletal networks such as intermediate filaments and microtubules. The main advantage of this technique is that it allows the observation of cellular structures, which are not resolved with conventional fluorescence microscopy.Visual demonstration of this method is critical as the control of sample preparation and acquisition of robe-linking data is crucial in order to limit the generation of artifacts. After growing U373 cells according to the text protocol, fix the cells by first using PBS to wash them once. Then, remove the PBS and add one milliliter per well of preheated extraction fixation solution.Incubate the cells at room temperature for 60 seconds. Then remove the solution and add one milliliter per well of freshly prepared and preheated 4%PFA diluted in cytoskeleton buffer. Place the 12-well plate back into the incubator at 37 degrees Celsius for 10 minutes.Then remove the PFA and add three milliliters of PBS per well. Use PBS to wash the cells twice. Then remove the PBS and add freshly prepared 10 millimolars sodium borohydride diluted in PBS in order to quench the autofluorescence from the glutaraldehyde.Incubate the cells at room temperature for seven minutes and transfer the recycled sodium borohydride into a specific bin. Use PBS to wash the wells three times for five minutes each. Then remove the PSB and add 5%BSA in PBS as a blocking solution.After immunostaining samples and preparing solutions in buffers according to the text protocol, mount the coverslip containing the labeled cells on a magnetic sample holder. And add the imaging buffer to completely fill the chamber. Apply the lid and make sure that there are no air bubbles between the imaging buffer and the lid.Using absolute ethanol, clean the bottom of the sample and verify that there are no leaks. Then if necessary, use grease to properly seal the sample hold. To carry out imaging, switch on the microscope and the acquisition software.Set up the acquisition parameters according to the text protocol, using the 100-fold NA 1.46 objective, the 1.6-fold Optivar lens, and the TIRF UHP mode. Create a 647 track to image the vimentin filaments labeled with Alexa Fluor 647. Select the 405 and 642 nanometer laser lines and the LP 655 emission filter.Then, create a 555 track to image the microtubules labeled with Alexa Fluor 555. Select the 561, 488, and 405 nanometer laser lines to image the fluorophores and the BP 570 to 650 emission filter. Next, add oil to the objective and place the sample on the lens.Then, select the locate tab and open the shutter of the fluorescence lamp. Find the focus and use the eyepiece to look for the cells to image. Then use the joystick to position the cells in the center of the field.Click on the acquisition tab to return to acquisition mode. Then select the 647 track and set the 642 laser power to 0.2%and the 405 laser power to its minimal value. Set the exposure time to 50 milliseconds and the gain to 50.Then choose continuous acquisition mode to observe the cell on the screen. Make sure that there is at least one fluorescent bead in the field of view. Use an autoscale mode for the display and adjust the focus.Next, take a wide field epifluorescence image of the vimentin network by clicking on snap and save the image. To check TIRF illumination, click on TIRF, press continuous, adjust the acquisition parameters in order to have a homogenous field of illumination. Then press snap and save the image.Check the 555 track. Uncheck the 647 track, and select the 555 track. Take an epifluorescence image of the microtubule network and save it.Then take a TIRF image and save it. Now, check the 647 track. Uncheck the 555 track, and select the 647 track.Set the gain to zero and the exposure time to 10 milliseconds. Then press continuous. Set the 642 nanometer laser power to 100%in order to pump most of the Alexa 647 dyes to the dark state.Once the fluorophores start blinking, increase the exposure to 15 milliseconds and the gain to 300. Use the range indicator mode to verify that single molecule signals do not saturate the camera as indicated by the red color. In that case, decrease the gain until the saturation disappears.The beads will remain saturated at the beginning of the acquisition. Press stop to discontinue observation of the cell. Expand the online processing tool and click online processing PALM to visualize the STORM image during acquisition.Use nine for the peak mask size and six for the peak intensity to noise. Now, press start acquisition. During acquisition, refocus on the cell if necessary.Adjust the exposure time and eventually switch on the 405 nanometer laser line starting at the 0.001%to keep a medium density of fluorophores with a minimum distance of one micrometer between single molecules. Make sure that the peak of localization precision on the histogram below the reconstructed image is centered around or below 10 nanometers. Press stop to end the movie when more than one million localizations have been reached.Save the raw data from the STORM acquisition with the CZI format. Then in the channels tool, check track 555, uncheck track 647, and select track 555. Next, press the continuous button.Set the exposure time to 30 milliseconds and the gain to zero. Then set both 488 and 561 lasers to 100%to pump Alexa 555 dyes to the dark state. Use the HILO mode of illumination.Once the fluorophores are depleted, press stop. Set the gain to 250 and decrease the 488 laser to 50%Use the range indicator to check that single molecules do not saturate the camera. If that is the case, decrease the gain.Now, press start acquisition. During acquisition, increase the gain gradually to reach the limit of saturation. Increase step-by-step the 405 nanometer laser power to activate the molecules and reach a medium density in the field of view.Decrease the 488 nanometer laser power to 30%when the 405 laser is about 15%Then decrease gradually the 488 while increasing the 405 laser power in order to keep the blinking of the molecules as fast as possible and with a medium density. The 488 laser line coupled with the 561 excitation laser at maximal intensity increases both the on and off rates of the fluorophores, whereas the 405 laser line only increases the on rate. Stop the acquisition when 500, 000 localizations or more have been reached or when no more molecules are blinking.Then save the raw data from the STORM acquisition with the CZI format. To carry out image reconstruction using the PAL-Drift tool, choose the model-based correction type with automatic segments with a maximum size of eight. Press apply multiple times in a row until the drift is corrected.This model-based correction applies an algorithm based on cross-correlation analysis, which corrects the drift. Using the PAL filter tools, improve the appearance of the STORM image by selecting only the molecules which were best localized. For example, limit the localization precision to 30 nanometers and the PSF to 120 to 180 nanometers.With the PAL-Render tool, use a pixel resolution of five or 10 nanometers and parameters according to the text protocol. Select render auto dynamic range HR with a 95%value and render auto dynamic range SWF with a 90%value. Then select render best quality.In the PALM menu of the processing tab, select PALM convert. Press select and then apply. Finally, save the created image with the format LSM and not CZI.This figure shows a typical example of a D-STORM image of vimentin filaments immuno-labeled with Alexa 647. The increase in resolution can clearly be observed upon comparison with the image acquired with a standard, wide-field microscope. The fluorescence intensity profiles presented in this graph show that super resolution microscopy imaging allows the resolution of vimentin bundles.The D-STORM resolution is sufficient to count the number of filaments present in the bundles. Shown here is a typical example of the dual-colored D-STORM imaging of vimentin and microtubule networks immuno-labeled with Alexa 647 and Alexa 555, respectively. Good vimentin images should have at least 5, 000 localizations per micrometer squared and 2, 500 per micrometer squared for microtubules.Once mastered, this technique can be done in three days if it performed properly. While attempting this procedure, it is important to adapt the methods of fixation and parametrization to the protein that would be imaged. For example, fixation with only glutaraldehyde gives poor results for intermediate filaments, but is best for microtubule fixation.It is important to remember to use freshly prepared samples and solutions, especially MEA, whose pH has to be carefully adjusted. After its development, this technique paved the way for researchers in the field of cell biology to explore the morphology of nanoscopic cellular structures. After watching this video, you should have a good understanding of how to perform sample preparation, image acquisition, and reconstruction of 2D dual-colored D-STORM images of intermediate filaments and microtubules.Don't forget that working with some solutions, especially PFA, NABH4 can be extremely hazardous and precautions such as wearing gloves, working under the chemical hood, and using specific bins should always been taken while performing this procedure.

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Research

JoVE Journal

Biology

Labeling Stem Cells with Fluorescent Dyes for non-invasive Detection with Optical Imaging

Optical imaging (OI) is an easy, fast and inexpensive tool for in vivo monitoring of new stem cell based therapies. The technique is based on ex vivo labeling of stem cells with a fluorescent dye, subsequent intravenous injection of the labeled cells and visualization of their accumulation in specific target organs or pathologies. The presented technique demonstrates how we label human mesenchymal stem cells (hMSC) by simple incubation with the lipophilic fluorescent dye DiD (C67H103CIN2O3S) and how we label human embryonic stem cells (hESC) with the FDA approved fluorescent dye Indocyanine Green (ICG). The uptake mechanism is via adherence and diffusion of the lypophilic dye across the phospholipid cell membrane bilayer. The labeling efficiency is usually improved if the cells are incubated with the dye in serum-free media as opposed to incubation in serum-containing media. Furthermore, the addition of the transfection agent Protamine Sulfate significantly improves contrast agent uptake.

This video shows techniques for labeling of human embryonic stem cells and mesenchymal stem cells with fluorescent dyes. This technique can be used for an in vivo tracking of transplanted stem cells with optical imaging and for histopathological correlations with fluorescence microscopy.

Optical imaging (OI) is an easy, fast and inexpensive tool for in vivo monitoring of new stem cell based therapies. The technique is based on ex vivo ...

Proper Care and Cleaning of the Microscope

Keeping the microscope optics clean is important for high-quality imaging. Dust, fingerprints, excess immersion oil, or mounting medium on or in a microscope causes reduction in contrast and resolution. DIC is especially sensitive to contamination and scratches on the lens surfaces. This protocol details the procedure for keeping the microscope clean.

Keeping the microscope optics clean is important for high-quality imaging. Dust, fingerprints, excess immersion oil, or mounting medium on or in a microscope causes reduction in contrast and resolution. DIC is especially sensitive to contamination and scratches on the lens surfaces. This protocol details the procedure for keeping the microscope clean.

Keeping the microscope optics clean is important for high-quality imaging. Dust, fingerprints, excess immersion oil, or mounting medium on or in a ...

Major Components of the Light Microscope

The light microscope is a basic tool for the cell biologist, who should have a thorough understanding of how it works, how it should be aligned for different applications, and how it should be maintained as required to obtain maximum image-forming capacity and resolution. The components of the microscope are described in detail here.

The light microscope is a basic tool for the cell biologist, who should have a thorough understanding of how it works, how it should be aligned for different applications, and how it should be maintained as required to obtain maximum image-forming capacity and resolution. The components of the microscope are described in detail here.

The light microscope is a basic tool for the cell biologist, who should have a thorough understanding of how it works, how it should be aligned for ...

Phase Contrast and Differential Interference Contrast (DIC) Microscopy

Phase-contrast microscopy is often used to produce contrast for transparent, non light-absorbing, biological specimens. The technique was discovered by Zernike, in 1942, who received the Nobel prize for his achievement. DIC microscopy, introduced in the late 1960s, has been popular in biomedical research because it highlights edges of specimen structural detail, provides high-resolution optical sections of thick specimens including tissue cells, eggs, and embryos and does not suffer from the  phase halos  typical of phase-contrast images. This protocol highlights the principles and practical applications of these microscopy techniques.

Phase Contrast and Differential Interference Contrast DIC Microscopy

This protocol highlights the principles and practical applications of Phase and Differential Interference Contrast (DIC) Microscopy

Phase-contrast microscopy is often used to produce contrast for transparent, non light-absorbing, biological specimens. The technique was discovered by ...

Imaging Exocytosis in Retinal Bipolar Cells with TIRF Microscopy

Total internal reflectance fluorescence (TIRF) microscopy is a technique that allows the study of events happening at the cell membrane, by selective imaging of fluorescent molecules that are closest to a high refractive index substance such as glass1. In this article, we apply this technique to image exocytosis of synaptic vesicles in retinal bipolar cells isolated from the goldfish retina. These neurons are very suitable for this kind of study due to their large axon terminals. By simultaneously patch clamping the bipolar cells, it is possible to investigate the relationship between pre-synaptic voltage and synaptic release2,3. Synaptic vesicles inside the bipolar cell terminals are loaded with a fluorescent dye (FM 1-43&reg;) by co-puffing the dye and a ringer solution containing a high K+ concentration onto the synaptic terminals. This depolarizes the cells and stimulates endocytosis and consequent dye uptake into the glutamatergic vesicles. After washing the excess dye away for around 30 minutes, cells are ready for being patch clamped and imaged simultaneously with a 488 nm laser. The patch pipette solution contains a rhodamine-based peptide that binds selectively to the synaptic ribbon protein RIBEYE4, thereby labeling ribbons specifically when terminals are imaged with a 561 nm laser. This allows the precise localization of active zones and the separation of synaptic from extra-synaptic events.

In this video, we demonstrate how to label and visualize single synaptic vesicle exocytosis and trafficking in goldfish retinal bipolar cells using total internal reflectance fluorescence (TIRF) microscopy.

Total internal reflectance fluorescence (TIRF) microscopy is a technique that allows the study of events happening at the cell membrane, by selective ...

Direct Imaging of ER Calcium with Targeted-Esterase Induced Dye Loading (TED)

Visualization of calcium dynamics is important to understand the role of calcium in cell physiology. To examine calcium dynamics, synthetic fluorescent Ca2+ indictors have become popular. Here we demonstrate TED (= targeted-esterase induced dye loading), a method to improve the release of Ca2+ indicator dyes in the ER lumen of different cell types. To date, TED was used in cell lines, glial cells, and neurons in vitro. TED bases on efficient, recombinant targeting of a high carboxylesterase activity to the ER lumen using vector-constructs that express Carboxylesterases (CES). The latest TED vectors contain a core element of CES2 fused to a red fluorescent protein, thus enabling simultaneous two-color imaging. The dynamics of free calcium in the ER are imaged in one color, while the corresponding ER structure appears in red. At the beginning of the procedure, cells are transduced with a lentivirus. Subsequently, the infected cells are seeded on coverslips to finally enable live cell imaging. Then, living cells are incubated with the acetoxymethyl ester (AM-ester) form of low-affinity Ca2+ indicators, for instance Fluo5N-AM, Mag-Fluo4-AM, or Mag-Fura2-AM. The esterase activity in the ER cleaves off hydrophobic side chains from the AM form of the Ca2+ indicator and a hydrophilic fluorescent dye/Ca2+ complex is formed and trapped in the ER lumen. After dye loading, the cells are analyzed at an inverted confocal laser scanning microscope. Cells are continuously perfused with Ringer-like solutions and the ER calcium dynamics are directly visualized by time-lapse imaging. Calcium release from the ER is identified by a decrease in fluorescence intensity in regions of interest, whereas the refilling of the ER calcium store produces an increase in fluorescence intensity. Finally, the change in fluorescent intensity over time is determined by calculation of &Delta;F/F0.

Direct Imaging of ER Calcium with Targeted-Esterase Induced Dye Loading TED

Targeted-esterase induced dye loading (TED) supports the analysis of intracellular calcium store dynamics by fluorescence imaging. The method bases on targeting of a recombinant Carboxylesterase to the endoplasmic reticulum (ER), where it improves the local unmasking of synthetic low-affinity Ca2+ indicator dyes in the ER lumen.

Visualization of calcium dynamics is important to understand the role of calcium in cell physiology. To examine calcium dynamics, synthetic fluorescent ...

Imaging and 3D Reconstruction of Cerebrovascular Structures in Embryonic Zebrafish

Zebrafish are a powerful tool to study developmental biology and pathology in vivo. The small size and relative transparency of zebrafish embryos make them particularly useful for the visual examination of processes such as heart and vascular development. In several recent studies transgenic zebrafish that express EGFP in vascular endothelial cells were used to image and analyze complex vascular networks in the brain and retina, using confocal microscopy. Descriptions are provided to prepare, treat and image zebrafish embryos that express enhanced green fluorescent protein (EGFP), and then generate comprehensive 3D renderings of the cerebrovascular system. Protocols include the treatment of embryos, confocal imaging, and fixation protocols that preserve EGFP fluorescence. Further, useful tips on obtaining high-quality images of cerebrovascular structures, such as removal the eye without damaging nearby neural tissue are provided. Potential pitfalls with confocal imaging are discussed, along with the steps necessary to generate 3D reconstructions from confocal image stacks using freely available open source software.

Imaging of cerebrovascular development in larval zebrafish is described. Techniques to facilitate 3D imaging and modify cerebrovascular development using chemical treatments are also provided.

Zebrafish are a powerful tool to study developmental biology and pathology in vivo.  The small size and relative transparency of zebrafish embryos make ...

Simultaneous Multicolor Imaging of Biological Structures with Fluorescence Photoactivation Localization Microscopy

Localization-based super resolution microscopy can be applied to obtain a spatial map (image) of the distribution of individual fluorescently labeled single molecules within a sample with a spatial resolution of tens of nanometers. Using either photoactivatable (PAFP) or&#160;photoswitchable (PSFP) fluorescent proteins fused to proteins of interest, or organic dyes conjugated to antibodies or other molecules of interest, fluorescence photoactivation localization microscopy (FPALM) can simultaneously image multiple species of molecules within single cells. By using the following approach, populations of large numbers (thousands to hundreds of thousands) of individual molecules are imaged in single cells and localized with a precision of ~10-30 nm. Data obtained can be applied to understanding the nanoscale spatial distributions of multiple protein types within a cell. One primary advantage of this technique is the dramatic increase in spatial resolution: while diffraction limits resolution to ~200-250 nm in conventional light microscopy, FPALM can image length scales more than an order of magnitude smaller. As many biological hypotheses concern the spatial relationships among different biomolecules, the improved resolution of FPALM can provide insight into questions of cellular organization which have previously been inaccessible to conventional fluorescence microscopy. In addition to detailing the methods for sample preparation and data acquisition, we here describe the optical setup for FPALM. One additional consideration for researchers wishing to do super-resolution microscopy is cost: in-house setups are significantly cheaper than most commercially available imaging machines. Limitations of this technique include the need for optimizing the labeling of molecules of interest within cell samples, and the need for post-processing software to visualize results. We here describe the use of PAFP and PSFP expression to image two protein species in fixed cells. Extension of the technique to living cells is also described.

We demonstrate the use of fluorescence photo activation localization microscopy (FPALM) to simultaneously image multiple types of fluorescently labeled molecules&#160;within cells. The techniques described yield the localization of thousands to hundreds of thousands of individual fluorescent labeled proteins, with a precision of tens of nanometers&#160;within single cells.

Localization-based super resolution microscopy can be applied to obtain a spatial map (image) of the distribution of individual fluorescently labeled ...

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) maintain the turnover of all mature blood cell lineages. The coordination of the complex signals leading to specific HSC fates relies upon the interaction between HSCs and the intricate bone marrow microenvironment, which is still poorly understood[1-2].
We describe how by combining a newly developed specimen holder for stable animal positioning with multi-step confocal and two-photon in vivo imaging techniques, it is possible to obtain high-resolution 3D stacks containing HSPCs and their surrounding niches and to monitor them over time through multi-point time-lapse imaging. High definition imaging allows detecting ex vivo labeled hematopoietic stem and progenitor cells (HSPCs) residing within the bone marrow. Moreover, multi-point time-lapse 3D imaging, obtained with faster acquisition settings, provides accurate information about HSPC movement and the reciprocal interactions between HSPCs and stroma cells.
Tracking of HSPCs in relation to GFP positive osteoblastic cells is shown as an exemplary application of this method. This technique can be utilized to track any appropriately labeled hematopoietic or stromal cell of interest within the mouse calvarium bone marrow space.

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

The nature of the interactions between hematopoietic stem and progenitor cells (HSPCs) and bone marrow niches is poorly understood. Custom hardware modifications and a multi-step acquisition protocol allow the use of two-photon and confocal microscopy to image ex vivo labeled HSPCs homed within bone marrow areas, tracking interactions and movement.

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) ...

Three-dimensional Super Resolution Microscopy of F-actin Filaments by Interferometric PhotoActivated Localization Microscopy (iPALM)

Fluorescence microscopy enables direct visualization of specific biomolecules within cells. However, for conventional fluorescence microscopy, the spatial resolution is restricted by diffraction to ~ 200 nm within the image plane and &#62; 500 nm along the optical axis. As a result, fluorescence microscopy has long been severely limited in the observation of ultrastructural features within cells. The recent development of super resolution microscopy methods has overcome this limitation. In particular, the advent of photoswitchable fluorophores enables localization-based super resolution microscopy, which provides resolving power approaching the molecular-length scale. Here, we describe the application of a three-dimensional super resolution microscopy method based on single-molecule localization microscopy and multiphase interferometry, called interferometric PhotoActivated Localization Microscopy (iPALM). This method provides nearly isotropic resolution on the order of 20 nm in all three dimensions. Protocols for visualizing the filamentous actin cytoskeleton, including specimen preparation and operation of the iPALM instrument, are described here. These protocols are also readily adaptable and instructive for the study of other ultrastructural features in cells.

Three-dimensional Super Resolution Microscopy of F-actin Filaments by Interferometric PhotoActivated Localization Microscopy iPALM

We present a protocol for the application of interferometric PhotoActivated Localization Microscopy (iPALM), a 3-dimensional single-molecule localization super resolution microscopy method, to the imaging of the actin cytoskeleton in adherent mammalian cells. This approach allows light-based visualization of nanoscale structural features that would otherwise remain unresolved by conventional diffraction-limited optical microscopy.

Fluorescence microscopy enables direct visualization of specific biomolecules within cells. However, for conventional fluorescence microscopy, the spatial ...