The authors thank the Research Flow Cytometry Core at Cincinnati Children&#8217;s Hospital Research Foundation and Richard Demarco, Sherree Friend, and Scott Mordecai from the Amnis Corporation (part of EMD Milllipore) for expert technical support. This work was supported by the National Institutes of Health grants K08HL088126 and R01HL116352 (T.A.K.) and P30 DK090971 (Y.Z.).

1. Long-term In vitro Erythropoiesis Culture (Ex vivo Erythroid Differentiation Culture Protocol by Giarratana et al.8, Modified and Adapted for Mouse Cells)
This is a 3-step long-term in vitro erythropoiesis protocol. In the first step (days 0-4) 2 x 105 cells/ml are placed in erythroblast growth medium supplemented with stem cell factor (SCF), interleukin-3 (IL-3), and erythropoietin (Epo). In the second step (days 5-6), cells are resuspended at 2 x 105 cells/ml and co-cultured on adherent stroma cells (MS5) in fresh erythroblast growth medium supplemented only with Epo. In the third step (days 7-9), cells are cultured on a layer of MS-5 cells in fresh erythroblast growth medium without cytokines up to enucleation (Figure 1A).
All animal protocols were approved by the Institutional Animal Care and Use Committee (IACUC) of Cincinnati Children&#8217;s Hospital Medical Center.
<ol>
	<li>Harvest of bones and isolation of low-density bone marrow cells
	<ol>
		<li>Add 2 ml sterile IMDM containing 2% fetal bovine serum (FBS) in a 15-ml conical tube and keep on ice.</li>
		<li>Euthanize a 2-6 month old wild type C57/BL6 mouse (along with or without genetically-targeted mouse of interest) following institution-approved protocol (e.g. CO2 inhalation, followed by cervical dislocation).</li>
		<li>Isolate pelvic bones, femurs, and tibiae of both legs using forceps and scalpel, add them to the tube containing IMDM+2% FBS and keep on ice.</li>
		<li>Add 1 ml IMDM+2% FBS in a sterile flow-cytometry tube and flush bones using forceps and a tuberculin syringe with a 25-G&#160;x 5/8&#34; needle. Flush IMDM+2% FBS through the bones a few times gently (by aspirating ~500 &#181;l from the cell suspension and flushing it again through the bone), and collect the bone marrow cells into the flow-cytometry tube. Flushing is complete when bones appear white.</li>
		<li>Filter cell-suspension through a 40-&#956;m cell strainer set on top of a 50-ml conical tube. Wash cell strainer with IMDM+2% FBS and using the same medium adjust final volume of cell suspension to 5&#160;ml.</li>
		<li>Prepare low-density bone marrow cells (LDBM) by density gradient centrifugation: carefully layer the 5&#160;ml of&#160;cell-suspension on 5 ml of density gradient cell separation medium 1.083 g/ml in a 15-ml tube and spin at 750 x g for&#160;25 min at room temperature (RT) with no brake/low acceleration.</li>
		<li>Transfer supernatant (everything up to about the 2-ml mark of the 15-ml tube in order to acquire buffy coat) to a new 15-ml tube and perform one more wash with IMDM+2% FBS at 525 x g for&#160;5 min at&#160;RT.</li>
		<li>Aspirate supernatant and lyse any remaining red blood cells (RBC) by suspending the pellet in 3 ml RBC lysis buffer for 5 min at&#160;RT. If a greater purity of erythroblasts is required at the final step (e.g. for biochemical studies), purify LDBM cells further at this step to Linneg cells by magnetic separation.</li>
	</ol>
	</li>
	<li>Ex vivo erythroid differentiation culture protocol starting from LDBM or Linneg cells (Figure 1A)
	<ol>
		<li>Add 7 ml IMDM+2% FBS, spin at 525 x g for&#160;5 min at&#160;RT and resuspend the pelleted cells in 2 ml erythroblast growth medium (EGM), consisting of: 
		a. StemPro-34 medium, containing 
		b. 2.6% StemPro-34 medium supplement, 
		c. 20% BIT-9500, 
		d. 900 ng/ml ferrous sulfate, 
		e. 90 ng/ml ferric nitrate, 
		f. 100 units/ml penicillin/streptomycin, 2 mM L-glutamine 
		g. 10-6 M hydrocortisone 
		h. and freshly added cytokines: 
		i) 100 ng/ml SCF, 
		ii) 5 ng/ml IL-3, and 
		iii) 3 IU/ml Epo.</li>
		<li>Count the cells using an automated cell counter or manually at a microscope using a hemocytometer.
		</li>
		<li>Plate in a 6-well cell-culture plate at a concentration of 5 x 105 cells/well to a final volume of 2.5 ml in EGM (2 x 105 LDBM cells/ml) and incubate at 37 &#176;C (this is considered as day #0 of culture).
		</li>
		<li>Change medium by aspirating 1.5 ml of the supernatant, spinning at 525 x g for&#160;5 min at&#160;RT, resuspending in 1.5 ml of fresh medium containing all 3 cytokines and adding back to the wells every day on days #2, 3, 4, to optimize proliferative phase. On day 3, remove all cells, count and split into appropriate number of wells in order to sustain well cell concentrations of ~2 x 105 cells/ml. Maintain culture at 37 &#176;C/5% CO2.</li>
		<li>On day 4, plate MS5 cells (murine stromal cell line) to wells of a new cell-culture 6-well plate. The MS5 cell-culture medium is &#945;-MEM containing 20% FBS, 100 units/ml penicillin/streptomycin, and 2 mM L-glutamine.</li>
		<li>On day 5, count number of cells (now significantly enriched in erythroblasts) in each well of the original culture plate using an automated cell counter or manually at a microscope using a hemocytometer.</li>
		<li>Lift all cells from each well and transfer to 15-ml conical tubes, spin down at 525 x g for&#160;5 min at&#160;RT, aspirate supernatant and dissolve pellets with fresh EGM containing only Epo (3 IU/ml) to a concentration of 2 x 105 cells/ml.</li>
		<li>Aspirate supernatant from the wells where MS-5 cells were plated the previous day (targeted to 70-80% confluency at the time of co-culture) and add the erythroid cells in these wells in EGM containing only Epo (although not their medium of choice, MS-5 cells survive well in EGM for several days).</li>
		<li>Change medium adding fresh EPO on day #6.</li>
		<li>Change medium on day #7, using EGM with no added cytokines. On days 7 through 9, test samples for enucleation with flow cytometry after staining with anti-Ter119 and Syto-16 daily and proceed to staining samples for Multi-Spectral Imaging Flow Cytometry (as detailed in section 3). 
		Note: Before plating and on day 2, 4, 6, and 7 of culture, monitor cultured cells for erythroblast enrichment and differentiation with flow cytometry by assessing surface markers CD44 and Ter119 vs size (FSC).9 Alternatively CD71, Ter119, and FSC can also be used10,11.</li>
	</ol>
	</li>
</ol>
2. Fast Enucleation Assay, According to the Protocol Described by Yoshida et al.12 with Modifications (Figure 1B)
<ol>
	<li>Stress erythropoiesis induction and stroma cell preparation for in vitro erythropoiesis culture
	<ol>
		<li>Anesthetize a 2-6 month old wild type C57/BL6 mouse per IACUC guidelines (e.g. with isoflurane solution). Ensure that the mouse has been adequately anesthetized by checking for absence of reflexive responses to a gentle hind-paw pinch and for regular respirations during the procedure. Use vet ophthalmic ointment on eyes to prevent dryness while under anesthesia.</li>
		<li>Induce stress erythropoiesis via tail bleeding to a final volume of 500 &#956;l. Using an insulin syringe, inject equal volume of normal saline intraperitoneally to assure fluid resuscitation of the animal (hold animal in Trendelenburg position before injecting and inject in the lower abdomen so as not to damage internal organs).</li>
		<li>Do not leave the mouse unattended until it has regained motor control as indicated by the animal starting to move around the cage and being able to stand and walk without falling. The phlebotomized mouse is placed in a cage without other mice.</li>
		<li>After 2 days, plate MS-5 cells in wells of a 24-well cell-culture plate. Incubate MS-5 cells at 37 &#176;C/5% CO2 in MS5 cell medium (a-MEM containing 20% FBS, 100 units/ml penicillin/streptomycin, and 2 mM L-glutamine) with the goal to be 70-80% confluent in plate wells after 48 hr.</li>
	</ol>
	</li>
	<li>Harvest of spleen and processing of splenocytes
	<ol>
		<li>Four days (96 hr) after stress erythropoiesis induction, euthanize previously bled mouse through IACUC-approved protocol (e.g. CO2 inhalation followed by cervical dislocation).</li>
		<li>Harvest spleen and put it in a 15-ml conical tube containing IMDM 2% FBS and keep on ice.</li>
		<li>Back in the laboratory, in the tissue culture hood under sterile conditions, invert spleen-containing tube on a 40-&#956;m cell strainer set on top of a 50-ml tube. Crush spleen using the plunger of a 5-ml plastic syringe.</li>
		<li>Wash cell strainer with IMDM+2% FBS and using the same medium, adjust the final volume of cell suspension to 5 ml.</li>
		<li>Carefully layer the 5 ml splenocyte suspension on 5 ml density gradient cell separation medium 1.083 g/ml in a 15-ml tube and spin at 750 x g for&#160;25 min at&#160;RT with no brake/low acceleration.</li>
		<li>Transfer supernatant (solution down to about the 2-ml mark of the 15-ml tube in order to acquire buffy coat) to a new 15-ml tube and perform one more wash with IMDM+2% FBS at 525 x g for&#160;5 min at&#160;RT.</li>
		<li>Aspirate supernatant and lyse red blood cells by suspending the pellet in 3 ml RBC lysis buffer for 5 min at&#160;RT.</li>
		<li>Add 7 ml IMDM+2% FBS to wash cells and to dilute and neutralize the RBC lysis buffer and spin at 525 x g for&#160;5 min at&#160;4&#160;&#176;C.</li>
		<li>Aspirate supernatant and suspend pelleted cells in 2 ml of erythroblast growth medium (EGM).</li>
	</ol>
	</li>
	<li>Culture of the isolated low-density splenocytes, enriched in erythroblasts, on plastic (first stage of fast in vitro erythropoiesis culture)
	<ol>
		<li>Count cells on an automated cell counter or manually by a hemocytometer. Usual number of cells isolated per spleen at this stage is ~15 x 106.</li>
		<li>Suspend cells further in EGM containing the cytokines (at final concentrations): SCF 50 ng/ml, IL-3 5 ng/ml, and Epo 2 U/ml.</li>
		<li>Plate 1-5 x 106 cells in a final volume of 1 ml/well (same number of cells per well depending on total number of cells) of a 24-well cell-culture plate and incubate O/N at 37&#160;&#176;C/5% CO2.</li>
	</ol>
	</li>
	<li>Culture of erythroblasts on MS5 cells (second stage of fast in vitro erythropoiesis culture
	<ol>
		<li>Aspirate supernatant from the plastic well and lift the cells (highly enriched in erythroblasts) by adding 2 ml of&#160;cold 10 mM EDTA in PBS for 5 min, on ice to each well.</li>
		<li>Put cells in fresh tubes, wash once in EGM (without cytokines) and resuspend in the same.</li>
		<li>Plate 5 x 105-1 x 106 cells in a 1-2 ml volume to each MS5 cell-coated well of a 24-well plate. If pharmacological inhibitors are being used in the experiment, add them at appropriate concentrations now.</li>
		<li>Incubate for 6 to 8 hr&#160;(time guided by microscopic observation of approximately 30%-40% enucleation in the untreated WT sample). The binding of erythroblasts to MS-5 cells accelerates their enucleation.</li>
		<li>Lift cells from each well by adding 2 ml of cold PBS + 10 mM EDTA, for 5 min, on ice. Along with the erythroblasts, MS-5 cells will also be collected but these can later be easily excluded during flow cytometric analysis as FSChi Ter119- cells.</li>
		<li>At this stage, cells can be fixed and stained for analysis by Multi-Spectral Imaging Flow Cytometry.</li>
	</ol>
	</li>
</ol>
3. Staining of Erythroblasts for Localization of Intracellular Proteins or Lipid Rafts During Enucleation by Multi-spectral Imaging Flow Cytometry&#160;
<ol>
	<li>Wash cells in PBS, spin 525 x g for&#160;5 min at&#160;RT and aspirate supernatant.</li>
	<li>Fix cells by resuspending cell pellets in 500 &#956;l of 3.7% formaldehyde in PBS for 15 min (fixation time may vary depending on the antigen being probed) and pipetting gently.</li>
	<li>Transfer to 1.5-ml plastic centrifuge tubes and incubate for 15 min at&#160;RT.</li>
	<li>Spin on a bench microcentrifuge 2,000 x g for&#160;20 sec, aspirate supernatant and perform one wash by adding 500 &#956;l PBS to each tube and pipetting gently.</li>
	<li>Spin on a bench microcentrifuge 2,000 x g for&#160;20 sec, aspirate supernatant and keep tubes on ice for at least 15 min. Permeablization steps 3.6-3.9 should be done quickly and efficiently, and following spinning/aspiration at RT, cell pellets should immediately be put back on ice, in order for cells to better retain their integrity.</li>
	<li>Take acetone solutions out from -20 &#176;C freezer and put on ice. Permeabilize cells by resuspending cell pellets first in 500 &#956;l ice-cold 50% acetone (1:1 with dH2O) and pipetting gently.</li>
	<li>Spin on bench microcentrifuge 2,000 x g for&#160;20 sec, aspirate supernatant and resuspend cell pellets in 500 &#956;l&#160;ice-cold&#160;100% acetone by pipetting gently.</li>
	<li>Spin on bench microcentrifuge 2,000 x g for&#160;20 sec, aspirate supernatant and resuspend cell pellets once more in 500 &#956;l&#160;ice-cold&#160;50% acetone by pipetting gently.</li>
	<li>Spin on bench microcentrifuge 2,000 x g for&#160;20 sec, aspirate supernatant and wash cells once in cold FACS buffer (PBS + 0.5% BSA) by pipetting gently.</li>
	<li>Prepare labeling cocktail with antibodies or markers for the molecules of interest: 0.1 U/100 &#956;l AF488-phalloidin for F-actin staining and 1 &#956;l/100 &#956;l Ter119-PECy7 for erythroid cell staining. Alternative or additional staining can also be done using AF-488-anti-&#946;-tubulin antibody (1:50), AF-594&#8211;conjugated cholera toxin subunit B to label lipid rafts (1:200), anti-pMRLC (Ser19) primary antibody for the phosphorylated myosin regulatory light chain (1:50), followed by anti-rabbit AF-488&#8211;conjugated secondary antibody (1:400), and anti-&#947;-tubulin primary rabbit antibody (1:100) followed by anti-rabbit AF-555-conjugated secondary antibody (1:300).</li>
	<li>Following supernatant aspiration, resuspend cell pellets in 100 &#956;l of the marker cocktail, pipette gently and incubate for 30 min at&#160;RT.</li>
	<li>Prepare FACS buffer containing 2.5 &#956;M of the nuclear stain Draq5.</li>
	<li>Wash cells in FACS buffer, spin down on bench microcentrifuge 2,000 x g for&#160;20 sec, aspirate supernatant and resuspend in 60 &#956;l FACS buffer containing Draq5.</li>
	<li>Run samples on the imaging flow cytometer to collect at least 10,000 events per experiment, compensate the raw data files as previously published13,&#160;and analyze results as shown in Figure 2, using the analysis software specific to the imaging flow cytometer.</li>
</ol>

<ol>
	<li>McGrath, K. E., Kingsley, P. D., Koniski, A. D., Porter, R. L., Bushnell, T. P., Palis, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enucleation+of+primitive+erythroid+cells+generates+a+transient+population+of+&amp;#34;pyrenocytes&amp;#34;+in+the+mammalian+fetus.">Enucleation of primitive erythroid cells generates a transient population of &amp;#34;pyrenocytes&amp;#34; in the mammalian fetus.</a> Blood. 111, 2409-2417 (2008).</li><li>Chasis, J. A., Mohandas, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Erythroblastic+islands:+niches+for+erythropoiesis.">Erythroblastic islands: niches for erythropoiesis.</a> Blood. 112, 470-478 (2008).</li><li>Koury, S. T., Koury, M. J., Bondurant, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cytoskeletal+distribution+and+function+during+the+maturation+and+enucleation+of+mammalian+erythroblasts.">Cytoskeletal distribution and function during the maturation and enucleation of mammalian erythroblasts.</a> J Cell Biol. 109, 3005-3013 (1989).</li><li>Ji, P., Jayapal, S. R., Lodish, H. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enucleation+of+cultured+mouse+fetal+erythroblasts+requires+Rac+GTPases+and+mDia2.">Enucleation of cultured mouse fetal erythroblasts requires Rac GTPases and mDia2.</a> Nat Cell Biol. 10, 314-321 (2008).</li><li>Keerthivasan, G., Small, S., Liu, H., Wickrema, A., Crispino, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vesicle+trafficking+plays+a+novel+role+in+erythroblast+enucleation.">Vesicle trafficking plays a novel role in erythroblast enucleation.</a> Blood. 116, 3331-3340 (2010).</li><li>McGrath, K. E., Bushnell, T. P., Palis, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multispectral+imaging+of+hematopoietic+cells:+where+flow+meets+morphology.">Multispectral imaging of hematopoietic cells: where flow meets morphology.</a> J Immunol Methods. 336, 91-97 (2008).</li><li>Konstantinidis, D. G., 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=Signaling+and+cytoskeletal+requirements+in+erythroblast+enucleation.">Signaling and cytoskeletal requirements in erythroblast enucleation.</a> Blood. 119, 6118-6127 (2012).</li><li>Giarratana, M. 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=Ex+vivo+generation+of+fully+mature+human+red+blood+cells+from+hematopoietic+stem+cells.">Ex vivo generation of fully mature human red blood cells from hematopoietic stem cells.</a> Nat Biotechnol. 23, 69-74 (2005).</li><li>Chen, K., Liu, J., Heck, S., Chasis, J. A., An, X., Mohandas, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Resolving+the+distinct+stages+in+erythroid+differentiation+based+on+dynamic+changes+in+membrane+protein+expression+during+erythropoiesis.">Resolving the distinct stages in erythroid differentiation based on dynamic changes in membrane protein expression during erythropoiesis.</a> Proc Natl Acad Sci U S A. , (2009).</li><li>Kalfa, T. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rac1+and+Rac2+GTPases+are+necessary+for+early+erythropoietic+expansion+in+the+bone+marrow+but+not+in+the+spleen.">Rac1 and Rac2 GTPases are necessary for early erythropoietic expansion in the bone marrow but not in the spleen.</a> Haematologica. 95, 27-35 (2010).</li><li>Koulnis, M., Pop, R., Porpiglia, E., Shearstone, J. R., Hidalgo, D., Socolovsky, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+and+analysis+of+mouse+erythroid+progenitors+using+the+CD71/TER119+flow-cytometric+assay.">Identification and analysis of mouse erythroid progenitors using the CD71/TER119 flow-cytometric assay.</a> J Vis Exp. , (2011).</li><li>Yoshida, H., Kawane, K., Koike, M., Mori, Y., Uchiyama, Y., Nagata, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phosphatidylserine-dependent+engulfment+by+macrophages+of+nuclei+from+erythroid+precursor+cells.">Phosphatidylserine-dependent engulfment by macrophages of nuclei from erythroid precursor cells.</a> Nature. 437, 754-758 (2005).</li><li>Ortyn, W. E., 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=Sensitivity+measurement+and+compensation+in+spectral+imaging.">Sensitivity measurement and compensation in spectral imaging.</a> Cytometry A. 69, 852-862 (2006).</li></ol>

The authors declare no competing financial interests.

In recent years the study of erythroblast enucleation has gained increasing momentum&#160;since it is the step in in vitro erythropoiesis cultures that is most difficult to reproduce efficiently in order to achieve successful, large-scale production of red blood cells ex vivo.&#160;Up until recently, the study of erythroblast enucleation utilized mainly fluorescence microscopy and flow cytometry methods.&#160;Fluorescence microscopy methods, albeit helpful in identifying participating molecules, require...

Terminal differentiation within the erythroid lineage in mammals concludes with the dramatic process of enucleation, through which the orthochromatic erythroblast expels its membrane-encased nucleus (pyrenocyte)1, generating a reticulocyte2. The exact mechanism of this process, which is also the rate-limiting step of successful, large-scale, production of red blood cells in vitro, is not yet fully elucidated. The localization of key proteins and structures within enucleating erythroblasts relies on the use of fluorescent and electron microscopy3-5. This tedious process typically results in the identification of a limited number of enucleation events and does not always allow meaningful statistical analysis. Expanding on a method of erythroblast identification described previously by McGrath et al.6, we have developed a novel approach of identifying and studying enucleation events by Multi-Spectral Imaging Flow Cytometry (multiparameter high-speed cell imaging in flow, a method that combines fluorescent microscopy with flow cytometry)7, which can provide a sufficient number of observations to obtain measurements and perform statistical analysis.
Here, we describe first two in vitro erythropoiesis culture methods used in order to synchronize erythroblasts and increase the probability of capturing enucleation at the time of evaluation. Then we describe in detail the staining of erythroblasts after fixation and permeabilization in order to study the localization of intracellular proteins or lipid rafts during enucleation by multi-spectral imaging flow cytometry.
Samples are run on an imaging flow cytometer and the collected cells are gated appropriately to identify orthochromatic erythroblasts6. Orthochromatic erythroblasts are then analyzed based on their aspect ratio, as measured in brightfield imaging, versus their value for the parameter delta centroid XY Ter119-DNA, which is defined as the distance between the centers of the areas stained for Ter119 and DNA, respectively. The population of cells with low aspect ratio and high delta centroid XY Ter119/DNA is highly enriched in enucleating cells.&#160;Using wild-type (WT) erythroblasts versus erythroblasts with Mx-Cre mediated conditional deletion of Rac1 on Rac2-/- or combined Rac2-/-; Rac3-/- genetic background and this novel analysis protocol of multi-spectral imaging flow cytometry, we recently demonstrated that enucleation resembles asymmetric cytokinesis and that the formation of an actomyosin ring regulated in part by Rac GTPases is important for enucleation progression7.

<table border="0" cellpadding="0" cellspacing="0" width="934">
	<tbody>
		<tr height="22">
			<td height="22" style="height:22px;width:363px;">&#945;MEM medium</td>
			<td style="width:199px;">CellGro&#160;</td>
			<td style="width:207px;">15-012-CV</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="29">
			<td height="29" style="height:29px;width:363px;">IMDM medium</td>
			<td style="width:199px;">Hyclone (Thermo Scientific)</td>
			<td style="width:207px;">SH30228.01</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:363px;">Stempro-34 SFM</td>
			<td style="width:199px;">GIBCO (Life Tech)</td>
			<td style="width:207px;">10640</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="30">
			<td height="30" style="height:30px;width:363px;">Stempro-34 nutrient supplement</td>
			<td style="width:199px;">GIBCO (Life Tech)</td>
			<td style="width:207px;">10641-025</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:363px;">Fetal Bovine Serum (FBS)</td>
			<td style="width:199px;">Atlanta Biologicals</td>
			<td style="width:207px;">512450</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:363px;">BIT9500</td>
			<td style="width:199px;">Stemcell Technologies</td>
			<td style="width:207px;">09500</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;width:363px;">Bovine Serum Albumin (BSA)</td>
			<td style="width:199px;">Fisher Scientific</td>
			<td style="width:207px;">BP-1600-100</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:363px;">Phosphate buffered saline (PBS)</td>
			<td style="width:199px;">Hyclone (Thermo Scientific)</td>
			<td style="width:207px;">SH30028.02</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:363px;">Penicillin/Streptomycin</td>
			<td style="width:199px;">Hyclone (Thermo Scientific)</td>
			<td style="width:207px;">SV30010</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:363px;">L-glutamine</td>
			<td style="width:199px;">Hyclone (Thermo Scientific)</td>
			<td style="width:207px;">SH30590.01</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:363px;">Isothesia (Isoflurane)</td>
			<td style="width:199px;">Butler-Schein</td>
			<td style="width:207px;">029405</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:363px;">Histopaque 1.083mg/ml</td>
			<td style="width:199px;">Sigma</td>
			<td style="width:207px;">10831</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="27">
			<td height="27" style="height:27px;width:363px;">BD Pharmlyse (RBC lysis buffer)</td>
			<td style="width:199px;">BD Biosciences</td>
			<td style="width:207px;">555899</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:363px;">Acetone</td>
			<td style="width:199px;">Sigma-Aldrich</td>
			<td style="width:207px;">534064</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="29">
			<td height="29" style="height:29px;width:363px;">Formaldehyde</td>
			<td style="width:199px;">Fisher Scientific</td>
			<td style="width:207px;">BP 531-500</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:363px;">Hydrocortisone</td>
			<td style="width:199px;">Sigma</td>
			<td style="width:207px;">H4001</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="26">
			<td height="26" style="height:26px;width:363px;">Stem Cell Factor (SCF)</td>
			<td style="width:199px;">Peprotech</td>
			<td style="width:207px;">250-03</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:363px;">Interleukin-3 (IL-3)</td>
			<td style="width:199px;">Peprotech</td>
			<td style="width:207px;">213-13</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:363px;">EPOGEN Epoetin Alfa (Erythropoietin, EPO)</td>
			<td style="width:199px;">AMGEN</td>
			<td style="width:207px;">available by pharmacy</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="31">
			<td height="31" style="height:31px;width:363px;">CD44-FITC antibody</td>
			<td style="width:199px;">BD Pharmingen</td>
			<td style="width:207px;">553133</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:363px;">CD71-FITC antibody</td>
			<td style="width:199px;">BD Pharmingen</td>
			<td style="width:207px;">553266</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="30">
			<td height="30" style="height:30px;width:363px;">Ter119-PECy7 antibody</td>
			<td style="width:199px;">BD Pharmingen</td>
			<td style="width:207px;">557853</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:363px;">Phalloidin-AF488</td>
			<td style="width:199px;">Invitrogen (Life Technologies)</td>
			<td style="width:207px;">A12379</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:363px;">&#946;-tubulin-AF488 antibody</td>
			<td style="width:199px;">Cell Signaling</td>
			<td style="width:207px;">#3623</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:363px;">anti-rabbit AF488-secondary antibody</td>
			<td style="width:199px;">Invitrogen (Life Technologies)</td>
			<td style="width:207px;">A11008</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:363px;">anti-rabbit AF555-secondary antibody</td>
			<td style="width:199px;">Invitrogen (Life Technologies)</td>
			<td style="width:207px;">A21428</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:363px;">AF594-cholera toxin B subunit</td>
			<td style="width:199px;">Invitrogen (Life Technologies)</td>
			<td style="width:207px;">C34777</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:363px;">pMRLC (Ser19) antibody</td>
			<td style="width:199px;">Cell Signaling</td>
			<td style="width:207px;">#3671</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:363px;">&#947;-tubulin antibody</td>
			<td style="width:199px;">Sigma</td>
			<td style="width:207px;">T-3559</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:363px;">Syto16</td>
			<td style="width:199px;">Invitrogen (Life Technologies)</td>
			<td style="width:207px;">S7578</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:363px;">Draq5</td>
			<td style="width:199px;">Biostatus</td>
			<td style="width:207px;">DR50200</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:363px;">Ferrous sulfate</td>
			<td style="width:199px;">Sigma</td>
			<td style="width:207px;">F7002</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:363px;">Ferric nitrate</td>
			<td style="width:199px;">Sigma</td>
			<td style="width:207px;">F3002</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:363px;">EDTA</td>
			<td style="width:199px;">Fisher Scientific</td>
			<td style="width:207px;">BP120500</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="37">
			<td height="37" style="height:37px;width:363px;">15ml tubes</td>
			<td style="width:199px;">BD Falcon</td>
			<td style="width:207px;">352099</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="30">
			<td height="30" style="height:30px;width:363px;">50ml tubes</td>
			<td style="width:199px;">BD Falcon</td>
			<td style="width:207px;">352098</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="31">
			<td height="31" style="height:31px;width:363px;">6-well plates</td>
			<td style="width:199px;">BD Falcon</td>
			<td style="width:207px;">353046</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="27">
			<td height="27" style="height:27px;width:363px;">24-well plates</td>
			<td style="width:199px;">BD Falcon</td>
			<td style="width:207px;">351147</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="31">
			<td height="31" style="height:31px;width:363px;">Flow tubes</td>
			<td style="width:199px;">BD Falcon</td>
			<td style="width:207px;">352008</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:363px;">Tuberculin syringe</td>
			<td style="width:199px;">BD</td>
			<td style="width:207px;">309602</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:363px;">Insulin syringe</td>
			<td style="width:199px;">BD</td>
			<td style="width:207px;">329461</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:363px;">Syringe needle 25G5/8</td>
			<td style="width:199px;">BD</td>
			<td style="width:207px;">305122</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:363px;">Capped flow tubes</td>
			<td style="width:199px;">BD</td>
			<td style="width:207px;">352058</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="27">
			<td height="27" style="height:27px;width:363px;">40&#956;m cell strainer</td>
			<td style="width:199px;">BD Falcon</td>
			<td style="width:207px;">352340</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:363px;">Scalpel (disposable)</td>
			<td style="width:199px;">Feather</td>
			<td style="width:207px;">2975#21</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:363px;">FACS Canto Flow Cytometer</td>
			<td style="width:199px;">BD</td>
			<td style="width:207px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:363px;">ImagestreamX Mark II Imaging Flow Cytometer</td>
			<td style="width:199px;">AMNIS (EMD Millipore)</td>
			<td style="width:207px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="48">
			<td height="48" style="height:48px;width:363px;">Image Data Exploration and Analysis Software (IDEAS) version 4.0 and up.</td>
			<td style="width:199px;">AMNIS (EMD Millipore)</td>
			<td style="width:207px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;width:363px;">Hemavet 950 Cell Counter</td>
			<td style="width:199px;">Drew Scientific</td>
			<td>CDC-9950-002</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:363px;">NAPCO series 8000WJ Incubator</td>
			<td style="width:199px;">Thermo scientific</td>
			<td style="width:207px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:363px;">Allegra X-15R Centrifuge</td>
			<td style="width:199px;">Beckman Coulter</td>
			<td>392932</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:363px;">Mini Mouse Bench centrifuge</td>
			<td style="width:199px;">Denville</td>
			<td style="width:207px;">C0801</td>
			<td style="width:167px;"></td>
		</tr>
	</tbody>
</table>

identification of a murine erythroblast subpopulation  enriched in enucleating events by multi-spectral imaging flow cytometry

Erythropoiesis in mammals concludes with the dramatic process of enucleation that results in reticulocyte formation. The mechanism of enucleation has not yet been fully elucidated. A common problem encountered when studying the localization of key proteins and structures within enucleating erythroblasts by microscopy is the difficulty to observe a sufficient number of cells undergoing enucleation.&#160;We have developed a novel analysis protocol using multiparameter high-speed cell imaging in flow (Multi-Spectral Imaging Flow Cytometry), a method that combines immunofluorescent microscopy with flow cytometry, in order to identify efficiently a significant number of enucleating events, that allows to obtain measurements and perform statistical analysis.
We first describe here two in vitro erythropoiesis culture methods used in order to synchronize murine erythroblasts and increase the probability of capturing enucleation at the time of evaluation.&#160;Then, we describe in detail the staining of erythroblasts after fixation and permeabilization in order to study the localization of intracellular proteins or lipid rafts during enucleation by multi-spectral imaging flow cytometry.&#160;Along with size and DNA/Ter119 staining which are used to identify the orthochromatic erythroblasts, we utilize the parameters &#8220;aspect ratio&#8221; of a cell in the bright-field channel that aids in the recognition of elongated cells and &#8220;delta centroid XY Ter119/Draq5&#8221; that allows the identification of cellular events in which the center of Ter119 staining (nascent reticulocyte) is far apart from the center of Draq5 staining (nucleus undergoing extrusion), thus indicating a cell about to enucleate.&#160;The subset of the orthochromatic erythroblast population with high delta centroid and low aspect ratio is highly enriched in enucleating cells.

First, cells are analyzed based on their Brightfield Aspect Ratio (the ratio of the length of their minor versus their major axis) and their Brightfield Area (indicative of their size). Events with a Brightfield Area value lower than 20 and higher than 200 are mostly debris and cell aggregates, respectively, and are excluded from the analysis (Figure 2A). Single cells (gate &#8220;R1&#8221;) are then analyzed based on their value for the Gradient RMS parameter, which indicates sharpness of image. Gate &#...

Watch this Scientific Journal Video about Identification of a Murine Erythroblast Subpopulation  Enriched in Enucleating Events by Multi-spectral Imaging Flow Cytometry at JoVE.com

Identification of a Murine Erythroblast Subpopulation  Enriched in Enucleating Events by Multi-spectral Imaging Flow Cytometry

The present protocol describes a novel method of identifying a population of enucleating orthochromatic erythroblasts by multi-spectral imaging flow cytometry, providing a visualization of the erythroblast enucleation process.

Erythropoiesis in mammals concludes with the dramatic process of enucleation that results in reticulocyte formation. The mechanism of enucleation has not ...

identification-murine-erythroblast-subpopulation-enriched-enucleating

Research

JoVE Journal

Biology

12.5K Views.  University of Cincinnati College of Medicine. The present protocol describes a novel method of identifying a population of enucleating orthochromatic erythroblasts by multi-spectral imaging flow cytometry, providing a visualization of the erythroblast enucleation process.

Video: Identification of a Murine Erythroblast Subpopulation  Enriched in Enucleating Events by Multi-spectral Imaging Flow Cytometry

IP-FCM:  Immunoprecipitation Detected by Flow Cytometry

Immunoprecipitation detected by flow cytometry (IP-FCM) is an efficient method for detecting and quantifying protein-protein interactions. The basic principle extends that of sandwich ELISA, wherein the captured primary analyte can be detected together with other molecules physically associated within multiprotein complexes. The procedure involves covalent coupling of polystyrene latex microbeads with immunoprecipitating monoclonal antibodies (mAb) specific for a protein of interest, incubating these beads with cell lysates, probing captured protein complexes with fluorochrome-conjugated probes, and analyzing bead-associated fluorescence by flow cytometry. IP-FCM is extremely sensitive, allows analysis of proteins in their native (non-denatured) state, and is amenable to either semi-quantitative or quantitative analysis. As additional advantages, IP-FCM requires no genetic engineering or specialized equipment, other than a flow cytometer, and it can be readily adapted for high-throughput applications.

The IP-FCM method is presented, which allows a sensitive, robust, biochemical assessment of native protein-protein interactions, without requiring genetic engineering or large sample sizes.

Immunoprecipitation detected by flow cytometry (IP-FCM) is an efficient method for detecting and quantifying protein-protein interactions. The basic ...

Flow Cytometry Purification of Mouse Meiotic Cells

The heterogeneous nature of cell types in the testis and the absence of meiotic cell culture models have been significant hurdles to the study of the unique differentiation programs that are manifest during meiosis. Two principal methods have been developed to purify, to varying degrees, various meiotic fractions from both adult and immature animals: elutriation or Staput (sedimentation) using BSA and/or percoll gradients. Both of these methods rely on cell size and density to separate meiotic cells1-5. Overall, except for few cell populations6, these protocols fail to yield sufficient purity of the numerous meiotic cell populations that are necessary for detailed molecular analyses. Moreover, with such methods usually one type of meiotic cells can be purified at a given time, which adds an extra level of complexity regarding the reproducibility and homogeneity when comparing meiotic cell samples.
Here, we describe a refined method that allows one to easily visualize, identify, and purify meiotic cells, from germ cells to round spermatids, using FACS combined with Hoechst 33342 staining7,8. This method provides an overall snapshot of the entire meiotic process and allows one to highly purify viable cells from most stage of meiosis. These purified cells can then be analyzed in detail for molecular changes that accompany progression through meiosis, for example changes in gene expression9,10and the dynamics of nucleosome occupancy at hotspots of meiotic recombination11.

An efficient method to obtain highly purified viable meiotic fractions from mouse testis is described, which combines a refined cell dissociation protocol with fluorescent activated cell sorting (FACS). This method takes advantage of differences in the DNA content and nuclear density of discrete meiotic fractions.

The heterogeneous nature of cell types in the testis and the absence of meiotic cell culture models have been significant hurdles to the study of the ...

Optimized Staining and Proliferation Modeling Methods for Cell Division Monitoring using Cell Tracking Dyes

Fluorescent cell tracking dyes, in combination with flow and image cytometry, are powerful tools with which to study the interactions and fates of different cell types in vitro and in vivo.1-5 Although there are literally thousands of publications using such dyes, some of the most commonly encountered cell tracking applications include monitoring of:
<ol>
	<li>stem and progenitor cell quiescence, proliferation and/or differentiation6-8</li>
	<li>antigen-driven membrane transfer9 and/or precursor cell proliferation3,4,10-18 and</li>
	<li>immune regulatory and effector cell function1,18-21.</li>
</ol>
Commercially available cell tracking dyes vary widely in their chemistries and fluorescence properties but the great majority fall into one of two classes based on their mechanism of cell labeling. "Membrane dyes", typified by PKH26, are highly lipophilic dyes that partition stably but non-covalently into cell membranes1,2,11. "Protein dyes", typified by CFSE, are amino-reactive dyes that form stable covalent bonds with cell proteins4,16,18. Each class has its own advantages and limitations. The key to their successful use, particularly in multicolor studies where multiple dyes are used to track different cell types, is therefore to understand the critical issues enabling optimal use of each class2-4,16,18,24.
The protocols included here highlight three common causes of poor or variable results when using cell-tracking dyes. These are:
<ol>
	<li>Failure to achieve bright, uniform, reproducible labeling. This is a necessary starting point for any cell tracking study but requires attention to different variables when using membrane dyes than when using protein dyes or equilibrium binding reagents such as antibodies.</li>
	<li>Suboptimal fluorochrome combinations and/or failure to include critical compensation controls. Tracking dye fluorescence is typically 102 - 103 times brighter than antibody fluorescence. It is therefore essential to verify that the presence of tracking dye does not compromise the ability to detect other probes being used.</li>
	<li>Failure to obtain a good fit with peak modeling software. Such software allows quantitative comparison of proliferative responses across different populations or stimuli based on precursor frequency or other metrics. Obtaining a good fit, however, requires exclusion of dead/dying cells that can distort dye dilution profiles and matching of the assumptions underlying the model with characteristics of the observed dye dilution profile.</li>
</ol>
Examples given here illustrate how these variables can affect results when using membrane and/or protein dyes to monitor cell proliferation.

Successful use of cell tracking dyes to monitor immune cell function and proliferation involves several critical steps. We describe methods for: 1) obtaining bright, uniform, reproducible label-ing with membrane dyes; 2) selecting fluorochromes and data acquisition conditions; and 3) choosing a model to quantify cell proliferation based on dye dilution.

Fluorescent cell tracking dyes, in combination with flow and image cytometry, are powerful tools with which to study the interactions and fates of ...

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 ...

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) ...

Cytosolic Calcium Measurements in Renal Epithelial Cells by Flow Cytometry

A variety of cellular processes, both physiological and pathophysiological, require or are governed by calcium, including exocytosis, mitochondrial function, cell death, cell metabolism and cell migration to name but a few. Cytosolic calcium is normally maintained at low nanomolar concentrations; rather it is found in high micromolar to millimolar concentrations in the endoplasmic reticulum, mitochondrial matrix and the extracellular compartment. Upon stimulation, a transient increase in cytosolic calcium serves to signal downstream events. Detecting changes in cytosolic calcium is normally performed using a live cell imaging set up with calcium binding dyes that exhibit either an increase in fluorescence intensity or a shift in the emission wavelength upon calcium binding. However, a live cell imaging set up is not freely accessible to all researchers. Alternative detection methods have been optimized for immunological cells with flow cytometry and for non-immunological adherent cells with a fluorescence microplate reader. Here, we describe an optimized, simple method for detecting changes in epithelial cells with flow cytometry using a single wavelength calcium binding dye. Adherent renal proximal tubule epithelial cells, which are normally difficult to load with dyes, were loaded with a fluorescent cell permeable calcium binding dye in the presence of probenecid, brought into suspension and calcium signals were monitored before and after addition of thapsigargin, tunicamycin and ionomycin.

Calcium is involved in numerous physiological and pathophysiological signaling pathways. Live cell imaging requires specialized equipment and can be time consuming. A quick, simple method using a flow cytometer to determine relative changes in cytosolic calcium in adherent epithelial cells brought into suspension was optimized.

A variety of cellular processes, both physiological and pathophysiological, require or are governed by calcium, including exocytosis, mitochondrial ...

Identification of Intracellular Signaling Events Induced in Viable Cells by Interaction with Neighboring Cells Undergoing Apoptotic Cell Death

Cells dying by apoptosis, also referred to as regulated cell death, acquire multiple new activities that enable them to influence the function of adjacent live cells. Vital activities, such as survival, proliferation, growth, and differentiation, are among the many cellular functions modulated by apoptotic cells. The ability to recognize and respond to apoptotic cells appears to be a universal feature of all cells, regardless of lineage or organ of origination. However, the diversity and complexity of the response to apoptotic cells mandates that great care be taken in dissecting the signaling events and pathways responsible for any particular outcome. In particular, one must distinguish among the multiple mechanisms by which apoptotic cells can influence intracellular signaling pathways within viable responder cells, including: receptor-mediated recognition of the apoptotic cell, release of soluble mediators by the apoptotic cell, and/or engagement of the phagocytic machinery. Here, we provide a protocol for identifying intracellular signaling events that are induced in viable responder cells following their exposure to apoptotic cells. A major advantage of the protocol lies in the attention it pays to dissection of the mechanism by which apoptotic cells modulate signaling events within responding cells. While the protocol is specific for a conditionally immortalized mouse kidney proximal tubular cell line (BU.MPT cells), it is easily adapted to cell lines that are non-epithelial in origin and/or derived from organs other than the kidney. The use of dead cells as a stimulus introduces several unique factors that can hinder the detection of intracellular signaling events. These problems, as well as strategies to minimize or circumvent them, are discussed within the protocol. Application of this protocol should aid our expanding knowledge of the broad influence that dead or dying cells exert on their live neighbors, both in health and in disease.

Here, we present a protocol for the determination of intracellular signaling events induced in viable cells by physical interaction with adjacent dead or dying cells. The protocol focuses on signaling events induced by receptor-mediated recognition of the dead cells, as opposed to their phagocytic uptake or release of soluble mediators.

Cells dying by apoptosis, also referred to as regulated cell death, acquire multiple new activities that enable them to influence the function of adjacent ...

Analysis of Cell Suspensions Isolated from Solid Tissues by Spectral Flow Cytometry

Flow cytometry has been used for the past 40 years to define and analyze the phenotype of lymphoid and other hematopoietic cells. Initially restricted to the analysis of a few fluorochromes, currently there are dozens of different fluorescent dyes, and up to 14-18 different dyes can be combined at a time. However, several limitations still impair the analytical capabilities. Because of the multiplicity of fluorescent probes, data analysis has become increasingly complex due to the need of large, multi-parametric compensation matrices. Moreover, mutant mouse models carrying fluorescent proteins to detect and trace specific cell types in different tissues have become available, so the analysis (by flow cytometry) of auto-fluorescent cell suspensions obtained from solid organs is required. Spectral flow cytometry, which distinguishes the shapes of emission spectra along a wide range of continuous wavelengths, addresses some of these problems. The data is analyzed with an algorithm that replaces compensation matrices and treats auto-fluorescence as an independent parameter. Thus, spectral flow cytometry should be capable of discriminating fluorochromes with similar emission peaks and can provide a multi-parametric analysis without compensation requirements.
This protocol describes the spectral flow cytometry analysis, allowing for a 21-parameter (19 fluorescent probes) characterization and the management of an auto-fluorescent signal, providing high resolution in minor population detection. The results presented here show that spectral flow cytometry presents advantages in the analysis of cell populations from tissues difficult to characterize in conventional flow cytometry, such as the heart and the intestine. Spectral flow cytometry thus demonstrates the multi-parametric analytical capacity of high-performing conventional flow cytometry without the requirement for compensation and enables auto-fluorescence management.

This article describes spectral cytometry, a new approach in flow cytometry that uses the shapes of emission spectra to distinguish fluorochromes. An algorithm replaces compensations and can treat auto-fluorescence as an independent parameter. This new approach allows for the proper analysis of cells isolated from solid organs.

Flow cytometry has been used for the past 40 years to define and analyze the phenotype of lymphoid and other hematopoietic cells. Initially restricted to ...

Measuring Endoreduplication by Flow Cytometry of Isolated Tuber Protoplasts

Endoreduplication, the replication of a cell's nuclear genome without subsequent cytokinesis, yields cells with increased DNA content and is associated with specialization, development and increase in cellular size. In plants, endoreduplication seems to facilitate the growth and expansion of certain tissues and organs. Among them is the tuber of potato (Solanum tuberosum), which undergoes considerable cellular expansion in fulfilling its function of carbohydrate storage. Thus, endoreduplication may play an important role in how tubers are able to accommodate this abundance of carbon. However, the cellular debris resulting from crude nuclear isolation methods of tubers, methods that can be used effectively with leaves, precludes the estimation of the tuber endoreduplication index (EI). This article presents a technique for assessing tuber endoreduplication through the isolation of protoplasts while demonstrating representative results obtained from different genotypes and compartmentalized tuber tissues. The major limitations of the protocol are the time and reagent costs required for sample preparation as well as relatively short lifespan of samples after lysis of protoplasts. While the protocol is sensitive to technical variation, it represents an improvement over traditional methods of nuclear isolation from these large specialized cells. Possibilities for improvements to the protocol such as recycling enzyme, the use of fixatives, and other alterations are proposed.

The protocol described herein is a method for measuring endoreduplication within tubers of potato (Solanum tuberosum). It includes plasmolysis and protoplast extraction steps to decrease the noise and debris in downstream flow cytometric analysis.

Endoreduplication, the replication of a cell's nuclear genome without subsequent cytokinesis, yields cells with increased DNA content and is associated ...

Sensitive Measurement of Mitophagy by Flow Cytometry Using the pH-dependent Fluorescent Reporter mt-Keima

Mitophagy is a process of selective removal of damaged or unnecessary mitochondria using autophagy machinery. Close links have been found between defective mitophagy and various human diseases, including neurodegenerative diseases, cancer, and metabolic diseases. In addition, recent studies have shown that mitophagy is involved in normal cellular processes, such as differentiation and development. However, the precise role of and molecular mechanisms underlying mitophagy require further study. Therefore, it is critical to develop a robust and convenient method for measuring changes in mitophagy activity. Here, we describe a detailed protocol for quantitatively assessing mitophagy activity through flow cytometry using the mitochondria-targeted fluorescent protein Keima (mt-Keima). This flow cytometry assay can analyze mitophagy activity more rapidly and sensitively than conventional microscopy- or immunoblotting-based methods. This protocol can be applied to analyze mitophagy activity in various cell types.

Mitophagy, the selective degradation of mitochondria, has been implicated in mitochondrial homeostasis and is deregulated in various human diseases. However, convenient experimental methods for measuring mitophagy activity are very limited. Here, we provide a sensitive assay for measuring mitophagy activity using flow cytometry.