This research project was supported by an ARRA Supplement, 5 R01 NS056380. Additional support was provided through the Viral Vector Core and the Microscopy Core of the Emory Neuroscience NINDS Core Facilities grant, P30NS055077. We thank the Emory Transgenic Mouse and Gene Targeting Core for deriving the mouse line from GENSAT; Greg Pazour for the stable SSTR3-GFP IMCD3 cell line; and Bradley Yoder for the Sstr3-GFP lentiviral construct. Monoclonal antibodies were obtained from the Developmental Studies Hybridoma Bank, developed under the auspices of the NICHD, and maintained by The University of Iowa, Department of Biological Sciences, Iowa City, IA 52242. All animal procedures were approved by the IACUC and the Biosafety Committee at Emory University.

Adult mice are euthanized by mechanical cervical dislocation. All animal procedures were approved by the IACUC and the Biosafety Committee at Emory University.
1. Embryo Generation
<ol>
	<li>Cross tamoxifen- inducible Cre line, CAGGCreER, and dsRedCre reporter line (Tg(CAG-Bgeo,-DsRed*MST)1Nagy) (Figure 1) 5,6. To monitor the relative timing of Shh response in the daughter cells, cross CAGGCreER and dsRed line with the Olig2-eGFP BAC transgenic mice (Tg(Olig2-EGFP)EK23Gsat) (Figure 1) 7,8.</li>
	<li>Dissolve tamoxifen in 100% ethanol, and perform intraperitoneal injection of 2.5 mg tamoxifen per 40 g of body weight into pregnant females at embryonic 6.5 (E6.5) to induce Cre expression and dsRed labeling in a small subset of cells.</li>
	<li>48 hr later dissect embryos, identify dsRed positive embryos using the fluorescent microscope, transfer them to the culture dish and observe single cell divisions during ex vivo imaging (see below). </li>
</ol>
2. Whole Mouse Embryo Culture
<ol>
	<li>Dissect E8.5 embryos in pre-warmed wash medium containing DMEM/F12 (1:1) supplemented with 10% newborn calf serum and 1% Penicillin/Streptomycin (P/S) 9.</li>
	<li>Directly after dissection, place embryos on the 37 &deg;C heating stage under the fluorescent microscope and identify as GFP and/or dsRed positive (see below).</li>
	<li>Transfer up to 2 embryos into a 500 &mu;l drop of pre-equilibrated culture media containing 50% Rat Serum from a Sprague-Dawley male and 50% DMEM/F12 (1:1) without phenol red supplemented with L-Glutamine and 1% of 1 M HEPES in 0.85% NaCl and P/S 9.</li>
	<li>Apply a thin layer (0.1 cm) of equilibrated light mineral oil over the medium to prevent evaporation and transfer the culture dish containing the embryos to the 37 &deg;C, 5% CO2 incubator.</li>
</ol>
3. Viral Infection
<ol>
	<li>In order to label cilia in the neuroepithelium, add 5-10 &mu;l of Sstr3-GFP lentivirus, approximately 2 million virions, to a 500 &mu;l equilibrated drop of culture medium containing an E8.5 embryo.</li>
	<li>After 18 hr of culture, transfer infected embryo into several drops of wash medium to wash out the virus and prepare neural tube slice.</li>
</ol>
4. Neural Tube Slice Preparation for Live Imaging
<ol>
	<li>Dissect neural tube of the E8.5 embryo in pre-warmed wash medium using a micro-knife size 0.025 mm, on a 1% agar coated dish.</li>
	<li>Place the isolated neural tube ventral side down in a 150 &mu;l drop of equilibrated culture medium without phenol red on the 35 mm poly-L-lysine coated glass bottom dish.</li>
	<li>Put small amounts of a 1:1 mixture made from 100% pure petroleum jelly and melted candle wax (candle from IKEA) around the mounted neural tube, and gently press by a narrow piece of glass coverslip in order to immobilize the sample.</li>
	<li>Cover the dish with a thin layer (~0.1 cm) of equilibrated light mineral oil (Figure 2).</li>
</ol>
5. Live Imaging and Time-lapse Confocal Microscopy
<ol>
	<li>Place dish under the Nikon A1R Laser Scanning Confocal Inverted Microscope equipped with an environmental chamber that regulates temperature, set to 37 &deg;C, and 5% CO2.</li>
	<li>Use 60x oil-immersion objective to record GFP labeled cilia and dsRed positive cells, while the 40x oil-immersion objective use to monitor Olig2-GFP and dsRed positive cells.</li>
	<li>Open the NIS Elements software to set up time lapse imaging conditions. Every 10 min acquire z-stacks of up to 25 &mu;m with a spacing of 1.5 &mu;m (40x objective) and up to 8 &mu;m with a spacing of 0.4 &mu;m (60x objective). Use 488 and 561 nm the excitation wavelengths and transmitted channel if needed. Acquire images at 512 x 512 size. Set up multiple user-defined regions of interest to perform simultaneously recording. 
	Optimal exposure to laser power and brightness of the image was adjusted by use low laser intensity (up to 11% for mCherry 561; up to 4.5% EGFP 405/488), scan speed 1, line average 2 and size of pin hole (61 &mu;m for dsRED; 28.1 &mu;m for Olig2; 72 &mu;m for SSTR3GFP; 61.3 &mu;m for dsRED and SSTR3GFP; 58 &mu;m for dsRED and Olig2). The use of genetically encoded fluorescent reporters enabled us to detect the brightness with low laser power.</li>
	<li>Analyze recorded data using Imaris 3D reconstruction software.</li>
</ol>
6. Immunofluorescence
<ol>
	<li>Fix embryos or isolated neural tubes in 4% paraformaldehyde / 0.1 M Phosphate Buffer on ice (4 &deg;C) for 1 hr in a glass dish.</li>
	<li>Wash samples 2 hr in PBS on ice (4 &deg;C) (change PBS a few times) and put in 30% sucrose / 0.1 M Phosphate Buffer over the night or until embryos sink.</li>
	<li>Embed in OCT, freeze on dry ice and store in -80 &deg;C. Perform sectioning on cryostat (10 mm).</li>
	<li>Wash slides for 10 min in wash solution containing 1% Heat-inactivated sheep serum and 0.1% Triton X-100 in PBS.</li>
	<li>Dilute primary antibodies in wash solution at following concentrations: Rat monoclonal anti-RFP (5F8,) 1:200; Rabbit anti-Arl13b serum 1:1500 and mouse monoclonal anti-Arl13b 1:5 (295B/54); Rabbit anti-Olig2 1:300; Mouse monoclonals Pax6, Shh and Nkx2.2- all 1:10; and Rabbit polyclonal Ki67 1:500. Add around 150 &mu;l per slide in flat humidified chamber, cover with parafilm to avoid drying out and leave over the night at 4 &deg;C.</li>
	<li>Wash slides in wash solution three times, 20 min each time at room temperature.</li>
	<li>Dilute secondary antibodies Alexa Fluor 488, 568, 350 in wash solutions at 1:200 concentration. Use Hoechst 1:3,000 or TO-PRO-3 1:500 to stain nuclei. Add 150 &mu;l per slide, leave 1 hr at room temperature in humidified chamber protected from light.</li>
	<li>Wash slides in wash solution two times, 30 min each time at room temperature.</li>
	<li>Mount slides in 80% ProLong Gold anti-fade reagent and view within 24 hr.</li>
</ol>

<ol>
	<li>Yamada, T., Pfaff, S. L., Edlund, T., Jessell, T. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Control+of+cell+pattern+in+the+neural+tube:+motor+neuron+induction+by+diffusible+factors+from+notochord+and+floor+plate.">Control of cell pattern in the neural tube: motor neuron induction by diffusible factors from notochord and floor plate.</a> Cell. 73, 673-686 (1993).</li><li>Ericson, J., Muhr, J., Placzek, M., Lints, T., Jessell, T. M., Edlund, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sonic+hedgehog+induces+the+differentiation+of+ventral+forebrain+neurons:+A+common+signal+for+ventral+patterning+within+the+neural+tube.">Sonic hedgehog induces the differentiation of ventral forebrain neurons: A common signal for ventral patterning within the neural tube.</a> Cell. 81, 747-756 (1995).</li><li>Briscoe, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Homeodomain+Protein+Code+Specifies+Progenitor+Cell+Identity+and+Neuronal+Fate+in+the+Ventral+Neural+Tube.">Homeodomain Protein Code Specifies Progenitor Cell Identity and Neuronal Fate in the Ventral Neural Tube.</a> Cell. 101, 435-445 (2000).</li><li>Berbari, N. F., Johnson, A. D., Lewis, J. S., Askwith, C. C., Mykytyn, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+ciliary+localization+sequences+within+the+third+intracellular+loop+of+G+protein-coupled+receptors.">Identification of ciliary localization sequences within the third intracellular loop of G protein-coupled receptors.</a> Mol. Biol. Cell. 19 (4), 1540-1547 (2008).</li><li>Vintersten, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mouse+in+red:+red+fluorescent+protein+expression+in+mouse+ES+cells,+embryos,+and+adult+animals.">Mouse in red: red fluorescent protein expression in mouse ES cells, embryos, and adult animals.</a> Genesis. 40 (4), 241-246 (2004).</li><li>Hayashi, S., McMahon, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+recombination+in+diverse+tissue+by+a+tamoxifen-inducible+form+of+Cre:+a+tool+for+temporally+regulated+gene+activation/inactivation+in+the+mouse.">Efficient recombination in diverse tissue by a tamoxifen-inducible form of Cre: a tool for temporally regulated gene activation/inactivation in the mouse.</a> Dev. Biol. 244 (2), 305-318 (2002).</li><li>Gong, S., Zheng, C., Doughty, M. L., Losos, K., Didkovsky, N., Schambra, U. B., Nowak, N. J., Joyner, A., Leblanc, G., Hatten, M. E., Heintz, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+gene+expression+atlas+of+the+central+nervous+system+based+on+bacterial+artificial+chromosomes.">A gene expression atlas of the central nervous system based on bacterial artificial chromosomes.</a> Nature. 425 (6961), 917-925 (2003).</li><li>Mukouyama, Y. S., Deneen, B., Lukaszewicz, A., Novitch, B. G., Wichterle, H., Jessell, T. M., Anderson, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Olig2++neuroepithelial+motoneuron+progenitors+are+not+multipotent+stem+cells+in+vivo.">Olig2+ neuroepithelial motoneuron progenitors are not multipotent stem cells in vivo.</a> Proc. Natl. Acad. Sci. U.S.A. 103 (5), 1551-1556 (2006).</li><li>Jones, E. A. V., Crotty, D., Kulesa, P. M., Waters, C. W., Baron, M. H., Fraser, S. E., Dickinson, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+in+vivo+imaging+of+postimplantation+mammalian+embryos+using+whole+embryo+culture.">Dynamic in vivo imaging of postimplantation mammalian embryos using whole embryo culture.</a> Genesis. 34, 228-235 (2002).</li><li>Piotrowska-Nitsche, K., Caspary, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Live+imaging+of+individual+cell+divisions+in+mouse+neuroepithelium+shows+asymmetry+in+cilium+formation+and+Sonic+hedgehog+response.">Live imaging of individual cell divisions in mouse neuroepithelium shows asymmetry in cilium formation and Sonic hedgehog response.</a> Cilia. 1 (6), (2012).</li><li>Nowotschin, S., Ferrer-Vaquer, A., Hadjantonakis, A. -. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+mouse+development+with+confocal+time-lapse+microscopy.">Imaging mouse development with confocal time-lapse microscopy.</a> Methods in Enzymology. 476, 351-377 (2010).</li></ol>

No conflicts of interest declared.

Our ex vivo system enables us to directly observe single cell divisions within the developing neuroepithelium in real time. As an example we examined cell divisions within the mouse embryonic neural tube and monitored either cilium formation or Shh response. We confirmed our imaging results (n = 24) were consistent with results from fixed sections (n = 178) indicating our technique provides physiologically relevant data.
Our technique relies on Cre induction being l...

<table border="1">
	<tbody>
		<tr>
			<td>Name of the reagent</td>
			<td>Company</td>
			<td>Catalogue number</td>
			<td>Comments (optional)</td>
		</tr>
		<tr>
			<td>Z/RED line (STOCK Tg(CAG-Bgeo,-DsRed*MST)1Nagy/J</td>
			<td>Jackson Laboratory</td>
			<td>005438</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Olig2-eGFP line (STOCK Tg(Olig2-EGFP)EK23Gsat/Mmcd</td>
			<td>MMRRC,</td>
			<td>010555-UCD</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>CAGGCreER</td>
			<td>Jackson Laboratory</td>
			<td>003724</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Tamoxifen</td>
			<td>Sigma</td>
			<td>T5648</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>DMEM/F12 (1:1)</td>
			<td>GIBCO</td>
			<td>21041-025</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Newborn calf serum</td>
			<td>Lonza</td>
			<td>14-416F</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin</td>
			<td>Invitrogen</td>
			<td>15140-122</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Rat Serum SD male</td>
			<td>Harlan Bioproducts</td>
			<td>4520</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>1M Hepes</td>
			<td>BioWhittaker</td>
			<td>17-737E</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>L-Glutamine</td>
			<td>GIBCO</td>
			<td>21041-025</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Light mineral oil</td>
			<td>Sigma</td>
			<td>M8410</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Sstr3-GFP lentivirus</td>
			<td>Emory Viral Core</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Micro-knife, size 0.025 mm</td>
			<td>Electron Microscopy Sciences</td>
			<td>62091</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>35 mm poly-L-lysine coated glass bottom dish</td>
			<td>MatTek</td>
			<td>P35GC-0-10-C</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>100% petroleum jelly</td>
			<td>Kroger</td>
			<td>FL9958c</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>A1R Laser Scanning Confocal Inverted Microscope</td>
			<td>Nikon</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>NIS Elements software</td>
			<td>Nikon</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Imaris 3D software</td>
			<td>Bitplane AG</td>
			<td>Imaris 7.2.3</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>OCT</td>
			<td>Tissue-Tek</td>
			<td>4583</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Cryostat</td>
			<td>Leica</td>
			<td>CM1850</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Heat-inactivated sheep serum</td>
			<td>Invitrogen</td>
			<td>16210-072</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Fisher Scientific</td>
			<td>BP151</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Parafolmaldehyde</td>
			<td>Sigma</td>
			<td>P6148</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Phosphate Buffer</td>
			<td>Lab made</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Rat monoclonal anti-RFP (5F8)</td>
			<td>Chromotek</td>
			<td>110411</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Rabbit anti-Arl13b serum</td>
			<td>NeuroMab</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>mouse monoclonal anti-Arl13b 1:5</td>
			<td>NeuroMab</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Rabbit anti-Olig2</td>
			<td>Chemicon</td>
			<td>AB9610</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Mouse monoclonals Pax6</td>
			<td>Developmental Hybridoma Bank</td>
			<td>Pax6</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Mouse monoclonalsShh</td>
			<td>Developmental Hybridoma Bank</td>
			<td>5E1</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Mouse monoclonals Nkx2.2</td>
			<td>Developmental Hybridoma Bank</td>
			<td>74.5A5</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Rabbit polyclonal Ki67</td>
			<td>Abcam</td>
			<td>AB15580</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Alexa Fluor 488</td>
			<td>Molecular Probes</td>
			<td>A11029</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Alexa Fluor 568</td>
			<td>Molecular Probes</td>
			<td>A11031</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Alexa Fluor 350</td>
			<td>Molecular Probes</td>
			<td>A11046</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Hoechst</td>
			<td>Fisher</td>
			<td>AC22989</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>TO-PRO-3</td>
			<td>Invitrogen</td>
			<td>T3605</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>ProLong Gold anti-fade reagent</td>
			<td>Invitrogen</td>
			<td>P36934</td>
			<td>&nbsp;</td>
		</tr>
	</tbody>
</table>

ex vivo live imaging of single cell divisions in mouse neuroepithelium

We developed a system that integrates live imaging of fluorescent markers and culturing slices of embryonic mouse neuroepithelium. We took advantage of existing mouse lines for genetic cell lineage tracing: a tamoxifen-inducible Cre line and a Cre reporter line expressing dsRed upon Cre-mediated recombination. By using a relatively low level of tamoxifen, we were able to induce recombination in a small number of cells, permitting us to follow individual cell divisions. Additionally, we observed the transcriptional response to Sonic Hedgehog (Shh) signaling using an Olig2-eGFP transgenic line 1-3 and we monitored formation of cilia by infecting the cultured slice with virus expressing the cilia marker, Sstr3-GFP 4. In order to image the neuroepithelium, we harvested embryos at E8.5, isolated the neural tube, mounted the neural slice in proper culturing conditions into the imaging chamber and performed time-lapse confocal imaging. Our ex vivo live imaging method enables us to trace single cell divisions to assess the relative timing of primary cilia formation and Shh response in a physiologically relevant manner. This method can be easily adapted using distinct fluorescent markers and provides the field the tools with which to monitor cell behavior in situ and in real time.

Here we performed ex vivo live imaging of single cell divisions within the E8.5 mouse neuroepithelium. To label individual cells, we induced Cre recombinase in a subset of cells containing a Cre reporter line that expressed dsRed upon recombination 5,6(Figure 3A). Thus, 48 hr later we were able to observe single cell divisions during ex vivo imaging (Figures 4A-D). Concomitantly, we monitored when the labeled cells became Shh-responsive by including a Shh tra...

Watch this Scientific Journal Video about Ex vivo Live Imaging of Single Cell Divisions in Mouse Neuroepithelium at JoVE.com

Ex vivo Live Imaging of Single Cell Divisions in Mouse Neuroepithelium

Here we develop the tools necessary for ex vivo live imaging to trace single cell divisions in the mouse E8.5 neuroepithelium

Ex vivo Live Imaging of Single Cell Divisions in Mouse Neuroepithelium

We developed a system that integrates live imaging of fluorescent markers and culturing slices of embryonic mouse neuroepithelium. We took advantage of ...

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10.3K Views.  Emory University School of Medicine. Here we develop the tools necessary for ex vivo live imaging to trace single cell divisions in the mouse E8.5 neuroepithelium

Video: Ex vivo Live Imaging of Single Cell Divisions in Mouse Neuroepithelium

Multiple-mouse Neuroanatomical Magnetic Resonance Imaging

The field of mouse phenotyping with magnetic resonance imaging (MRI) is rapidly growing, motivated by the need for improved tools for characterizing and evaluating mouse models of human disease. MRI is an excellent modality for investigating genetically altered animals. It is capable of whole brain coverage, can be used in vivo, and provides multiple contrast mechanisms for investigating different aspects of neuranatomy and physiology. The advent of high-field scanners along with the ability to scan multiple mice simultaneously allows for rapid phenotyping of novel mutations.
Effective mouse MRI studies require attention to many aspects of experiment design. In this article, we will describe general methods to acquire quality images for mouse phenotyping using a system that images mice concurrently in shielded transmit/receive radio frequency (RF) coils in a common magnet (Bock et al., 2003). We focus particularly on anatomical phenotyping, an important and accessible application that has shown a high potential for impact in many mouse models at our imaging centre. Before we can provide the detailed steps to acquire such images, there are important practical considerations for both in vivo brain imaging (Dazai et al., 2004) and ex vivo brain imaging (Spring et al., 2007) that should be noted. These are discussed below.

Magnetic resonance imaging (MRI) has become an increasingly popular tool for examining the phenotype of genetically altered mice. This article illustrates the methods necessary to achieve high-throughput phenotyping of genetically altered mice using multiple-mouse MRI.

The field of mouse phenotyping with magnetic resonance imaging (MRI) is rapidly growing, motivated by the need for improved tools for characterizing and ...

High-resolution Live Imaging of Cell Behavior in the Developing Neuroepithelium

The embryonic spinal cord consists of cycling neural progenitor cells that give rise to a large percentage of the neuronal and glial cells of the central nervous system (CNS). Although much is known about the molecular mechanisms that pattern the spinal cord and elicit neuronal differentiation1, 2, we lack a deep understanding of these early events at the level of cell behavior. It is thus critical to study the behavior of neural progenitors in real time as they undergo neurogenesis.
In the past, real-time imaging of early embryonic tissue has been limited by cell/tissue viability in culture as well as the phototoxic effects of fluorescent imaging. Here we present a novel assay for imaging such tissue for long periods of time, utilizing a novel ex vivo slice culture protocol and wide-field fluorescence microscopy (Fig. 1). This approach achieves long-term time-lapse monitoring of chick embryonic spinal cord progenitor cells with high spatial and temporal resolution.
This assay may be modified to image a range of embryonic tissues3, 4 In addition to the observation of cellular and sub-cellular behaviors, the development of novel and highly sensitive reporters for gene activity (for example, Notch signaling5) makes this assay a powerful tool with which to understand how signaling regulates cell behavior during embryonic development.

Imaging embryonic tissue in real-time is challenging over long periods of time. Here we present an assay for monitoring cellular and sub-cellular changes in chick spinal cord for long periods with high spatial and temporal resolution. This technique can be adapted for other regions of the nervous system and developing embryo.

The embryonic spinal cord consists of cycling neural progenitor cells that give rise to a large percentage of the neuronal and glial cells of the central ...

Live Imaging of Mitosis in the Developing Mouse Embryonic Cortex

Although of short duration, mitosis is a complex and dynamic multi-step process fundamental for development of organs including the brain. In the developing cerebral cortex, abnormal mitosis of neural progenitors can cause defects in brain size and function. Hence, there is a critical need for tools to understand the mechanisms of neural progenitor mitosis. Cortical development in rodents is an outstanding model for studying this process. Neural progenitor mitosis is commonly examined in fixed brain sections. This protocol will describe in detail an approach for live imaging of mitosis in ex vivo embryonic brain slices. We will describe the critical steps for this procedure, which include: brain extraction, brain embedding, vibratome sectioning of brain slices, staining and culturing of slices, and time-lapse imaging. We will then demonstrate and describe in detail how to perform post-acquisition analysis of mitosis. We include representative results from this assay using the vital dye Syto11, transgenic mice (histone H2B-EGFP and centrin-EGFP), and in utero electroporation (mCherry-&#945;-tubulin). We will discuss how this procedure can be best optimized and how it can be modified for study of genetic regulation of mitosis. Live imaging of mitosis in brain slices is a flexible approach to assess the impact of age, anatomy, and genetic perturbation in a controlled environment, and to generate a large amount of data with high temporal and spatial resolution. Hence this protocol will complement existing tools for analysis of neural progenitor mitosis.

Neural progenitor mitosis is a critical parameter of neurogenesis. Much of our understanding of neural progenitor mitosis is based on analysis of fixed tissue. Live imaging in embryonic brain slices is a versatile technique to assess mitosis with high temporal and spatial resolution in a controlled environment.

Although of short duration, mitosis is a complex and dynamic multi-step process fundamental for development of organs including the brain. In the ...

Ex Vivo Imaging of Postnatal Cerebellar Granule Cell Migration Using Confocal Macroscopy

During postnatal development, immature granule cells (excitatory interneurons) exhibit tangential migration in the external granular layer, and then radial migration in the molecular layer and the Purkinje cell layer to reach the internal granular layer of the cerebellar cortex. Default in migratory processes induces either cell death or misplacement of the neurons, leading to deficits in diverse cerebellar functions. Centripetal granule cell migration involves several mechanisms, such as chemotaxis and extracellular matrix degradation, to guide the cells towards their final position, but the factors that regulate cell migration in each cortical layer are only partially known. In our method, acute cerebellar slices are prepared from P10 rats, granule cells are labeled with a fluorescent cytoplasmic marker and tissues are cultured on membrane inserts from 4 to 10 hr before starting real-time monitoring of cell migration by confocal macroscopy at 37 &#176;C in the presence of CO2. During their migration in the different cortical layers of the cerebellum, granule cells can be exposed to neuropeptide agonists or antagonists, protease inhibitors, blockers of intracellular effectors or even toxic substances such as alcohol or methylmercury to investigate their possible role in the regulation of neuronal migration.

Ex Vivo Imaging of Postnatal Cerebellar Granule Cell Migration Using Confocal Macroscopy

During postnatal cerebellum development, immature granule cells originating from the germinal zone exhibit distinct modalities of migration to reach their final destination and to establish neuronal networks. This protocol describes the preparation of cerebellar slices and the confocal macroscopic approach used to investigate the factors that regulate neuronal migration.

During postnatal development, immature granule cells (excitatory interneurons) exhibit tangential migration in the external granular layer, and then ...

Simultaneous ex vivo Functional Testing of Two Retinas by in vivo Electroretinogram System

An In vivo electroretinogram (ERG) signal is composed of several overlapping components originating from different retinal cell types, as well as noise from extra-retinal sources. Ex vivo ERG provides an efficient method to dissect the function of retinal cells directly from an intact isolated retina of animals or donor eyes. In addition, ex vivo ERG can be used to test the efficacy and safety of potential therapeutic agents on retina tissue from animals or humans. We show here how commercially available in vivo ERG systems can be used to conduct ex vivo ERG recordings from isolated mouse retinas. We combine the light stimulation, electronic and heating units of a standard in vivo system with custom-designed specimen holder, gravity-controlled perfusion system and electromagnetic noise shielding to record low-noise ex vivo ERG signals simultaneously from two retinas with the acquisition software included in commercial in vivo systems. Further, we demonstrate how to use this method in combination with pharmacological treatments that remove specific ERG components in order to dissect the function of certain retinal cell types.

Simultaneous ex vivo Functional Testing of Two Retinas by in vivo Electroretinogram System

Ex vivo ERG can be used to record electrical activity of retinal cells directly from isolated intact retinas of animals or humans. We demonstrate here how common in vivo ERG systems can be adapted for ex vivo ERG recordings in order to dissect the electrical activity of retinal cells.

An In vivo electroretinogram (ERG) signal is composed of several overlapping components originating from different retinal cell types, as well as noise ...

Single-cell Resolution Fluorescence Live Imaging of Drosophila Circadian Clocks in Larval Brain Culture

The circadian pacemaker circuit orchestrates rhythmic behavioral and physiological outputs coordinated with environmental cues, such as day/night cycles. The molecular clock within each pacemaker neuron generates circadian rhythms in gene expression, which underlie the rhythmic neuronal functions essential to the operation of the circuit. Investigation of the properties of the individual molecular oscillators in different subclasses of pacemaker neurons and their interaction with neuronal signaling yields a better understanding of the circadian pacemaker circuit. Here, we present a time-lapse fluorescent microscopy approach developed to monitor the molecular clockwork in clock neurons of cultured Drosophila larval brain. This method allows the multi-day recording of the rhythms of genetically encoded fluorescent circadian reporters at single-cell resolution. This setup can be combined with pharmacological manipulations to closely analyze real-time response of the molecular clock to various compounds. Beyond circadian rhythms, this multipurpose method in combination with powerful Drosophila genetic techniques offers the possibility to study diverse neuronal or molecular processes in live brain tissue.

Single-cell Resolution Fluorescence Live Imaging of Drosophila Circadian Clocks in Larval Brain Culture

The goal of this protocol is to establish ex vivo Drosophila larval brain culture optimized to monitor circadian molecular rhythms with long-term fluorescence time-lapse imaging. The application of this method to pharmacological assays is also discussed.

The circadian pacemaker circuit orchestrates rhythmic behavioral and physiological outputs coordinated with environmental cues, such as day/night cycles. ...

Ex Vivo Imaging of Cell-specific Calcium Signaling at the Tripartite Synapse of the Mouse Diaphragm

The electrical activity of cells in tissues can be monitored by electrophysiological techniques, but these are usually limited to the analysis of individual cells. Since an increase of intracellular calcium (Ca2+) in the cytosol often occurs because of the electrical activity, or in response to a myriad of other stimuli, this process can be monitored by the imaging of cells loaded with fluorescent calcium-sensitive dyes.&#160; However, it is difficult to image this response in an individual cell type within whole tissue because these dyes are taken up by all cell types within the tissue. In contrast, genetically encoded calcium indicators (GECIs) can be expressed by an individual cell type and fluoresce in response to an increase of intracellular Ca2+, thus permitting the imaging of Ca2+ signaling in entire populations of individual cell types. Here, we apply the use of the GECIs GCaMP3/6 to the mouse neuromuscular junction, a tripartite synapse between motor neurons, skeletal muscle, and terminal/perisynaptic Schwann cells. We demonstrate the utility of this technique in classic ex vivo tissue preparations. Using an optical splitter, we perform dual-wavelength imaging of dynamic Ca2+ signals and a static label of the neuromuscular junction (NMJ) in an approach that could be easily adapted to monitor two cell-specific GECI or genetically encoded voltage indicators (GEVI) simultaneously. Finally, we discuss the routines used to capture spatial maps of fluorescence intensity. Together, these optical, transgenic, and analytic techniques can be employed to study the biological activity of distinct cell subpopulations at the NMJ in a wide variety of contexts.

Ex Vivo Imaging of Cell-specific Calcium Signaling at the Tripartite Synapse of the Mouse Diaphragm

Here we present a protocol to image calcium signaling in populations of individual cell types at the murine neuromuscular junction.

The electrical activity of cells in tissues can be monitored by electrophysiological techniques, but these are usually limited to the analysis of ...

Transpupillary Two-Photon In Vivo Imaging of the Mouse Retina

The retina transforms light signals from the environment into electrical signals that are propagated to the brain. Diseases of the retina are prevalent and cause visual impairment and blindness. Understanding how such diseases progress is critical to formulating new treatments. In vivo&#160;microscopy in animal models of disease is a powerful tool for understanding neurodegeneration and has led to important progress towards treatments of conditions ranging from Alzheimer&#39;s disease to stroke. Given that the retina is the only central nervous system structure inherently accessible by optical approaches, it naturally lends itself towards in vivo imaging. However, the native optics of the lens and cornea present some challenges for effective imaging access.
This protocol outlines methods for in vivo two-photon imaging of cellular cohorts and structures in the mouse retina at cellular resolution, applicable for both acute- and chronic-duration imaging experiments. It presents examples of retinal ganglion cell (RGC), amacrine cell, microglial, and vascular imaging using a suite of labeling techniques including adeno-associated virus (AAV) vectors, transgenic mice, and inorganic dyes. Importantly, these techniques extend to all cell types of the retina, and suggested methods for accessing other cellular populations of interest are described. Also detailed are example strategies for manual image postprocessing for display and quantification. These techniques are directly applicable to studies of retinal function in health and disease.

In vivo imaging is a powerful tool for the study of biology in health and disease. This protocol describes transpupillary imaging of the mouse retina with a standard two-photon microscope. It also demonstrates different in vivoimaging methods to fluorescently label multiple cellular cohorts of the retina.

The retina transforms light signals from the environment into electrical signals that are propagated to the brain. Diseases of the retina are prevalent ...

In vivo Calcium Imaging in Mouse Inferior Olive

Inferior olive (IO), a nucleus in the ventral medulla, is the only source of climbing fibers that form one of the two input pathways entering the cerebellum. IO has long been proposed to be crucial for motor control and its activity is currently considered to be at the center of many hypotheses of both motor and cognitive functions of the cerebellum. While its physiology and function have been relatively well studied on single-cell level in vitro, presently there are no reports on the organization of the IO network activity in living animals. This is largely due to the extremely challenging anatomical location of the IO, making it difficult to subject to conventional fluorescent imaging methods, where an optic path must be created through the entire brain located dorsally to the region of interest.
Here we describe an alternative method for obtaining state-of-the-art -level calcium imaging data from the IO network. The method takes advantage of the extreme ventral location of the IO and involves a surgical procedure for inserting a gradient-refractive index (GRIN) lens through the neck viscera to come into contact with the ventral surface of the calcium sensor GCaMP6s-expressing IO in anesthetized mice. A representative calcium imaging recording is shown to demonstrate the feasibility to record IO neuron activity after the surgery. While this is a non-survival surgery and the recordings must be conducted under anesthesia, it avoids damage to life-critical brainstem nuclei and allows conducting large variety of experiments investigating spatiotemporal activity patterns and input integration in the IO. This procedure with modifications could be used for recordings in other, adjacent regions of the ventral brainstem.

In vivo Calcium Imaging in Mouse Inferior Olive

We present a protocol to expose the brainstem of adult mouse from the ventral side. By using a gradient-refractive index lens with a miniature microscope, calcium imaging can be used to examine the activity of inferior olive neural somata in vivo.

Inferior olive (IO), a nucleus in the ventral medulla, is the only source of climbing fibers that form one of the two input pathways entering the ...

Mouse Retina OCT Fibergram Alignment with Confocal Images

Alignment of Visible-Light Optical Coherence Tomography Fibergrams with Confocal Images of the Same Mouse Retina

In recent years, in vivo retinal imaging, which provides non-invasive, real-time, and longitudinal information about biological systems and processes, has been increasingly applied to obtain an objective assessment of neural damage in eye diseases. Ex vivo confocal imaging of the same retina is often necessary to validate the in vivo findings especially in animal research. In this study, we demonstrated a method for aligning an ex vivo confocal image of the mouse retina with its in vivo images. A new clinical-ready imaging technology called visible light optical coherence tomography fibergraphy (vis-OCTF) was applied to acquire in vivo images of the mouse retina. We then performed the confocal imaging of the same retina as the &#34;gold standard&#34; to validate the in vivo vis-OCTF images. This study not only enables further investigation of the molecular and cellular mechanisms but also establishes a foundation for a sensitive and objective evaluation of neural damage in vivo.

Author Spotlight: Advancements in In Vivo and Ex Vivo Retinal Imaging for Improved Glaucoma Diagnosis and Treatment 

The present protocol outlines the steps for aligning in vivo visible-light optical coherence tomography fibergraphy (vis-OCTF) images with ex vivo confocal images of the same mouse retina for the purpose of verifying the observed retinal ganglion cell axon bundle morphology in the in vivo images.

In recent years, in vivo retinal imaging, which provides non-invasive, real-time, and longitudinal information about biological systems and processes, has ...