Name: tracking cells in gfp-transgenic zebrafish using the photoconvertible psmorange system
Uploaded: 2016-02-05T15:00:00
Description: Watch this Scientific Journal Video about Tracking Cells in GFP-transgenic Zebrafish Using the Photoconvertible PSmOrange System at JoVE.com

We thank O. Subach for providing the original H2B-PSmOrange plasmid and our fish facility team for fish care. We are grateful to the Nikon Imaging Center at the University of Heidelberg for access to microscopy equipment and analysis software. We acknowledge the support of the Core Facility Live Cell Imaging Mannheim at the CBTM (DFG INST 91027/10-1 FUGG). This work was supported by the Excellenzcluster CellNetworks, EcTop Spatio-temporal coordination of signaling processes (EcTop 2), University of Heidelberg to C.A.B. and the Medical Faculty Mannheim of the University Heidelberg and the DFG (FOR 1036/2, 298/3-1 and 298/6-1) to M.C.

1. H2B-PSmOrange mRNA In Vitro Transcription and mRNA Purification
<ol>
	<li>Linearize the H2B-PSmOrange containing pCS2+ plasmid using the NotI restriction enzyme according to manufacturer&#39;s instructions. 
	Note: Perform the next steps using appropriate protections such as gloves and lab coat to prevent mRNA contamination and degradation.</li>
	<li>Purify the linearized DNA using a PCR Purification kit or phenol-chloroform based methods according to manufacturers&#39; protocols.</li>
	<li>Use 1 &#181...

<ol>
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D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microinjection+of+zebrafish+embryos+to+analyze+gene+function.">Microinjection of zebrafish embryos to analyze gene function.</a> J Vis Exp. (25), e1115 (2009).</li><li>Concha, M. L., 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=Local+tissue+interactions+across+the+dorsal+midline+of+the+forebrain+establish+CNS+laterality.">Local tissue interactions across the dorsal midline of the forebrain establish CNS laterality.</a> Neuron. 39, 423-438 (2003).</li><li>Auer, T. O., Duroure, K., Concordet, J. 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Transgenic embryos carrying fluorescent reporters have helped fundamentally to understand embryonic development. However, there is still the essential need for promoters to facilitate the specific visualization of particular structures. In their absence, researchers rely on techniques such as the photoconversion of fluorescent proteins to find out about the origin and development of their structure of interest. This in turn is a crucial prerequisite to identify the molecular mechanisms involved in its development. Techni...

Exponentially improving imaging techniques allow following developmental processes over time periods of up to about four consecutive days3. In zebrafish and many other animal model systems, specific cells, tissues, axonal or vascular structures are marked by transgenic green or sometimes red or yellow fluorescent proteins to facilitate visualization. However, in most transgenic lines the transgene is not specifically expressed in the cells of interest but also additional structures, which hinders the precise tracking of for instance single cells or groups of cells.
Fluorescent photoconvertible proteins are well suited for cell tracking during embryonic development. The prerequisites for the application of such proteins are a long-lived nature, a well-separated emission range upon conversion and bright fluorescence. Available photoconvertible proteins comprise those that change their emission range upon conversion such as Kaede4, KiGR5, mEos26, PS-CFP2 or Dendra27 and others which are only fluorescent when photoactivated (PAmCherry8, PAGFP9 or PATagRFP10). Their applications to track cells in existing FP-transgenic animals are however limited as they often involve a green fluorescent state or do not fulfill all of the above criteria. Only recently, Subach and colleagues reported the PSmOrange protein, which changes its emission from orange/red to far red upon photoconversion and was successfully applied in cells in culture and cultured cells injected into mice2.
To investigate the protein's suitability for cell tracking in a living embryo, we generated an expression construct for the microinjection of nuclear-tagged H2B-PSmOrange into zebrafish embryos. We find that the protein fulfills all prerequisites for successful cell tracking in GFP transgenic backgrounds during the first 4 (and possibly more) days of zebrafish embryonic development. During this time, most of the cell migratory events are completed in fish making the PSmOrange system an excellent addition to the zebrafish toolkit.

<table border="0" cellpadding="0" cellspacing="0" width="821">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:303px;">PCR Purification Kit</td>
			<td style="width:233px;">Qiagen</td>
			<td align="right" style="width:119px;">28104</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">mMESSAGE mMACHINE SP6 Transcription kit</td>
			<td>Ambion</td>
			<td>AM1340</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">RNeasy MiniElute Cleanup kit</td>
			<td>Qiagen</td>
			<td align="right">74204</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Plastic Pasteur</td>
			<td>alpha laboratories</td>
			<td>LW4000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Original H2B-PSmOrange Plasmid</td>
			<td>Addgene</td>
			<td>31920</td>
			<td>The plasmid described in the paper is available in the Carl lab</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">FemtoJet Microinjector</td>
			<td>Eppendorf</td>
			<td>5247 000.013</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Forceps (5 Inox)</td>
			<td>NeoLab</td>
			<td>2-1633</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Lab-Tek II Chambered #1.5 German Coverglass System&#160;</td>
			<td>Nunc</td>
			<td align="right">155382</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Nikon A1R+</td>
			<td>Nikon GmbH Germany</td>
			<td>No Number</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Nikon PLAN Apo &#955; 20x air objective&#160;</td>
			<td>Nikon GmbH Germany</td>
			<td>No Number</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NIS Elements AR Software (v. 4.30.02)</td>
			<td>Nikon GmbH Germany/Laboratory Imaging</td>
			<td>No Number</td>
			<td></td>
		</tr>
	</tbody>
</table>

tracking cells in gfp-transgenic zebrafish using the photoconvertible psmorange system

The rapid development of transparent zebrafish embryos (Danio rerio) in combination with fluorescent labelings of cells and tissues allows visualizing developmental processes as they happen in the living animal. Cells of interest can be labeled by using a tissue specific promoter to drive the expression of a fluorescent protein (FP) for the generation of transgenic lines. Using fluorescent photoconvertible proteins for this purpose additionally allows to precisely follow defined structures within the expression domain. Illuminating the protein in the region of interest, changes its emission spectrum and highlights a particular cell or cell cluster leaving other transgenic cells in their original color. A major limitation is the lack of known promoters for a large number of tissues in the zebrafish. Conversely, gene- and enhancer trap screens have generated enormous transgenic resources discretely labeling literally all embryonic structures mostly with GFP or to a lesser extend red or yellow FPs. An approach to follow defined structures in such transgenic backgrounds would be to additionally introduce a ubiquitous photoconvertible protein, which could be converted in the cell(s) of interest. However, the photoconvertible proteins available involve a green and/or less frequently a red emission state1 and can therefore often not be used to track cells in the FP-background of existing transgenic lines. To circumvent this problem, we have established the PSmOrange system for the zebrafish2,3. Simple microinjection of synthetic mRNA encoding a nuclear form of this protein labels all cell nuclei with orange/red fluorescence. Upon targeted photoconversion of the protein, it switches its emission spectrum to far red. The quantum efficiency and stability of the protein makes PSmOrange a superb cell-tracking tool for zebrafish and possibly other teleost species.

Figure 1 illustrates an example of the PSmOrange photoconversion system. The pineal complex is a conserved structure in the vertebrate dorsal diencephalon. Like in many other vertebrates, this complex consists of the pineal organ in the center of the diencephalon and the left-sided parapineal cells. Elegant but time-consuming uncaging experiments showed that parapineal cells originate in the anterior part of the pineal organ13. In tg(foxD3:GFP); tg(flh:GFP) tra...

Watch this Scientific Journal Video about Tracking Cells in GFP-transgenic Zebrafish Using the Photoconvertible PSmOrange System at JoVE.com

Tracking Cells in GFP-transgenic Zebrafish Using the Photoconvertible PSmOrange System

We established the photoconvertible PSmOrange system as a powerful, straight-forward and cost inexpensive tool for in vivo cell tracking in GFP transgenic backgrounds. This protocol describes its application in the zebrafish model system.

The rapid development of transparent zebrafish embryos (Danio rerio) in combination with fluorescent labelings of cells and tissues allows visualizing ...

The overall goal of the PSmOrange Photo Conversion Technology is to track cells in the living animal during embryonic development and disease. This method can answer key questions in developmental biology such as uncovering the origin of cells which develop into tissues and organs. The main advantage of this technique is that it can be applied in GFP transgenic backgrounds.This method can also be applied in different fields of investigation such as regeneration, tumor progression and invasion. After generating and embedding PSmOrange and GFP expressing embryos according to the text protocol, place the embryo under the confocal microscope and use the 20x air objective and 488 and 561 nanometer lasers to scan the specimen to identify an area to photoconvert. To detect the PSmOrange protein before photoconversion, use the 561 nanometer laser at 0.74 milliwatts of power measured at the focus plane above the objective and adjust the laser power as necessary.Adjust the zoom factors to highlight the area of interest and reduce image acquisition time and photo toxicity. Using the 488 and 561 nanometer lasers in sequential mode and a Z step between 1.0 and 2.0 micrometers, acquire a Z stack covering the structures of interest. Adjust the line average and scan frequency to optimize the image quality.Then scan the sample and select the region of interest, or ROI tool, to highlight the area to photoconvert before fixing the ROI as the stimulation area. Select the photoactivation bleaching module, check the box to activate the 488 nanometer laser, then set the 488 nanometer laser to 80%and the scan speed to 0.5 seconds per frame. Next, open the photoconversion utility and click on Add'to specify the photoconversion protocol.In the acquisition stimulation menu, set Phase One to acquisition and in the loops menu, indicate the number of images to be acquired before photoconversion. Set Phase Two to stimulation and enter the number of stimulation events to be performed. Adjust Phase Three as described for Phase One.Optionally, insert a Waiting Phase after Phase Two by entering the time to wait before the last round of image acquisition. Once the parameters are set, apply the stimulation setting and run the photoconversion. Miscroscopic settings are crucial for PSmOrange photoconversion.To ensure a successful photoconversion, the embryo is imaged directly after the experiment to detect the photoconverted PSmOrange protein. If the conversion was not successful, the procedure is repeated. Using the 488, 561 and 640 nanometer lasers, and setting the 640 nanometer laser to high power, up to 4.5 milliwatts, acquire a final z stack with the settings just described.To dismount the embryo, remove the chamber from the microscope and use forceps to remove the embryo from the agarose. Transfer the embryo into a new sterilized plastic petri dish, or sterilized 6-well plate, containing 0.2 millimolar PTU in E3.Incubate the embryo at 28 degrees Celsius until the desired stage of development. To analyze the fate of photoconverted PSmOrange protein expressing cells, re-embed the embryo according to the text protocol.Under the confocal miscroscope, scan the specimen to identify photoconverted cells in the GFP transgenic structure of interest. Use the 488, 561, and 640 nanometer lasers to acquire a z stack with a fixed stack of 1 to 2 micrometers in sequential mode covering the structures. Using Image J Fiji software, identify cells which co-express GFP and the photoconverted protein.Duplicate the original stack, use the Gaussian Blur plugin and the image calculator to subtract the smooth stacks from the original. Apply specific thresholds to the green and far red channels in order to highlight the photoconverted cells. Then use the Analyze Particles tool to detect the threshold areas in the green channel with a suitable setting.Repeat this step for the far red channel. Open the image calculator plugin to detect the co-localizing cells. Display in yellow the overlapping ROIs in the green or the far red channel using the Analyze Particles tool.Using NIS-Elements software, carry out 3D date evaluation and display the stack in 3D using the Show Volume View option. Then use the graphic interface to select the green, red, and far red channels, adjust the brightness and the contrast and crop the 3D stack to highlight the photoconverted area. Shown here is an example of the PSmOrange photocoversion system in zebra fish transgenic FOXD3 floating head GFP embryos.At 26 hours post-fertilization, two cell clusters in the anterior part of the pineal were photoconverted and immediately imaged. The protein was detected with a 640 nanometer far red laser but not with a 561 nanometer laser. In these cells, GFP expression was initially reduced due to photobleaching.At 52 HPF, GFP and H2B PSmOrange were detected in the photoconverted H2B PSmOrange protein expressing cells. A few of these cells formed the parapineal on the left side of the brain. This result is consistent with previous reports on the parapineal cell origin in the anterior pineal and shows the applicability of the PSmOrange technique in the living GFP transgenic vertebrate embryo.Following this procedure, the cell tracking analysis can be performed in genetically manipululated embryos in order to answer additional questions regarding the molecular hierarchies underlying the cell's development.

tracking-cells-gfp-transgenic-zebrafish-using-photoconvertible

Research

JoVE Journal

Developmental Biology

Live Imaging of Innate Immune and Preneoplastic Cell Interactions Using an Inducible Gal4/UAS Expression System in Larval Zebrafish Skin

Here we describe a method to conditionally induce epithelial cell transformation by the use of the 4-Hydroxytamoxifen (4-OHT) inducible KalTA4-ERT2/UAS expression system1 in zebrafish larvae, and the subsequent live imaging of innate immune cell interaction with HRASG12V expressing skin cells. The KalTA4-ERT2/UAS system is both inducible and reversible which allows us to induce cell transformation with precise temporal/spatial resolution in vivo. This provides us with a unique opportunity to live image how individual preneoplastic cells interact with host tissues as soon as they emerge, then follow their progression as well as regression. Recent studies in zebrafish larvae have shown a trophic function of innate immunity in the earliest stages of tumorigenesis2,3. Our inducible system would allow us to live image the onset of cellular transformation and the subsequent host response, which may lead to important insights on the underlying mechanisms for the regulation of oncogenic trophic inflammatory responses. We also discuss how one might adapt our protocol to achieve temporal and spatial control of ectopic gene expression in any tissue of interest.

Studying the earliest events of preneoplastic cell progression and innate immune cell interaction is pivotal to understand and treat cancer. Here we describe a method to conditionally induce epithelial cell transformations and the subsequent live imaging of innate immune cell interaction with HRASG12V expressing skin cells in zebrafish larvae.

Here we describe a method to conditionally induce epithelial cell transformation by the use of the 4-Hydroxytamoxifen (4-OHT) inducible KalTA4-ERT2/UAS ...

Alginate Encapsulation of Pluripotent Stem Cells Using a Co-axial Nozzle

Pluripotent stem cells (PS cells) are the focus of intense research due to their role in regenerative medicine and drug screening. However, the development of a mass culture system would be required for using PS cells in these applications. Suspension culture is one promising culture method for the mass production of PS cells, although some issues such as controlling aggregation and limiting shear stress from the culture medium are still unsolved. In order to solve these problems, we developed a method of calcium alginate (Alg-Ca) encapsulation using a co-axial nozzle. This method can control the size of the capsules easily by co-flowing N2 gas. The controllable capsule diameter must be larger than 500 &#181;m because too high a flow rate of N2 gas causes the breakdown of droplets and thus heterogeneous-sized capsules. Moreover, a low concentration of Alg-Na and CaCl2 causes non-spherical capsules. Although an Alg-Ca capsule without a coating of Alg-PLL easily dissolves enabling the collection of cells, they can also potentially leak out from capsules lacking an Alg-PLL coating. Indeed, an alginate-PLL coating can prevent cellular leakage but is also hard to break. This technology can be used to research the stem cell niche as well as the mass production of PS cells because encapsulation can modify the micro-environment surrounding cells including the extracellular matrix and the concentration of secreted factors.

We established a method of encapsulating pluripotent stem cells (PS cells) into alginate hydrogel capsules using a co-axial nozzle. This prevents cells from aggregating excessively and limits the shear stress experienced by cells in suspension culture. The technique is applicable to the mass production of PS cells as well as research on stem cell niche.

Pluripotent stem cells (PS cells) are the focus of intense research due to their role in regenerative medicine and drug screening.  However, the ...

Analysis of Zebrafish Larvae Skeletal Muscle Integrity with Evans Blue Dye

The zebrafish model is an emerging system for the study of neuromuscular disorders. In the study of neuromuscular diseases, the integrity of the muscle membrane is a critical disease determinant. To date, numerous neuromuscular conditions display degenerating muscle fibers with abnormal membrane integrity; this is most commonly observed in muscular dystrophies. Evans Blue Dye (EBD) is a vital, cell permeable dye that is rapidly taken into degenerating, damaged, or apoptotic cells; in contrast, it is not taken up by cells with an intact membrane. EBD injection is commonly employed to ascertain muscle integrity in mouse models of neuromuscular diseases. However, such EBD experiments require muscle dissection and/or sectioning prior to analysis. In contrast, EBD uptake in zebrafish is visualized in live, intact preparations. Here, we demonstrate a simple and straightforward methodology for performing EBD injections and analysis in live zebrafish. In addition, we demonstrate a co-injection strategy to increase efficacy of EBD analysis. Overall, this video article provides an outline to perform EBD injection and characterization in zebrafish models of neuromuscular disease.

In this study, we describe a straightforward method to perform Evans Blue Dye (EBD) analysis on zebrafish larvae. This technique is a powerful tool for the characterization of skeletal muscle integrity and delineation of zebrafish models of muscular dystrophy, and is a valuable method for the development of novel therapeutics.

The zebrafish model is an emerging system for the study of neuromuscular disorders.  In the study of neuromuscular diseases, the integrity of the muscle ...

The Production of Pluripotent Stem Cells from Mouse Amniotic Fluid Cells Using a Transposon System

Induced pluripotent stem (iPS) cells are generated from mouse and human somatic cells by forced expression of defined transcription factors using different methods. Here, we produced iPS cells from mouse amniotic fluid cells, using a non-viral-based transposon system. All obtained iPS cell lines exhibited characteristics of pluripotent cells, including the ability to differentiate toward derivatives of all three germ layers in vitro and in vivo. This strategy opens up the possibility of using cells from diseased fetuses to develop new therapies for birth defects.

In this study, we generate induced pluripotent stem cells from mouse amniotic fluid cells, using a non-viral-based transposon system.

Induced pluripotent stem (iPS) cells are generated from mouse and human somatic cells by forced expression of defined transcription factors using ...

Single-cell Photoconversion in Living Intact Zebrafish

Animal and plant tissue is composed of distinct populations of cells. These cells interact over time to build and maintain the tissue and can cause disease when disrupted. Scientists have developed clever techniques to investigate characteristics and natural dynamics of these cells within intact tissue by expressing fluorescent proteins in subsets of cells. However, at times, experiments require more selected visualization of cells within the tissue, sometimes at the single-cell or population-of-cells manner. To achieve this and visualize single cells within a population of cells, scientists have utilized single-cell photoconversion of fluorescent proteins. To demonstrate this technique, we show here how to direct UV light to an Eos-expressing cell of interest in an intact, living zebrafish. We then image those photoconverted Eos+ cells 24 h later to determine how they changed in the tissue. We describe two techniques: single cell photoconversion and photoconversions of populations of cell. These techniques can be used to visualize cell-cell interactions, cell-fate and differentiation, and cell migrations, making it a technique that is applicable in numerous biological questions.

Here, we present a protocol to show how cell photoconversion is achieved through UV exposure to specific areas expressing the fluorescent protein, Eos, in living animals.

Animal and plant tissue is composed of distinct populations of cells. These cells interact over time to build and maintain the tissue and can cause ...

Computational Analysis of the Caenorhabditis elegans Germline to Study the Distribution of Nuclei, Proteins, and the Cytoskeleton

The Caenorhabditis elegans (C. elegans) germline is used to study several biologically important processes including stem cell development, apoptosis, and chromosome dynamics. While the germline is an excellent model, the analysis is often two dimensional due to the time and labor required for three-dimensional analysis. Major readouts in such studies are the number/position of nuclei and protein distribution within the germline. Here, we present a method to perform automated analysis of the germline using confocal microscopy and computational approaches to determine the number and position of nuclei in each region of the germline. Our method also analyzes germline protein distribution that enables the three-dimensional examination of protein expression in different genetic backgrounds. Further, our study shows variations in cytoskeletal architecture in distinct regions of the germline that may accommodate specific spatial developmental requirements. Finally, our method enables automated counting of the sperm in the spermatheca of each germline. Taken together, our method enables rapid and reproducible phenotypic analysis of the C. elegans germline.

Computational Analysis of the Caenorhabditis elegans Germline to Study the Distribution of Nuclei, Proteins, and the Cytoskeleton

We present an automated method for three-dimensional reconstruction of the Caenorhabditis elegans germline. Our method determines the number and position of each nucleus within the germline and analyses germline protein distribution and cytoskeletal structure.

The Caenorhabditis elegans (C. elegans) germline is used to study several biologically important processes including stem cell development, apoptosis, and ...

Three-dimensional Angiogenesis Assay System using Co-culture Spheroids Formed by Endothelial Colony Forming Cells and Mesenchymal Stem Cells

Studies in the field of angiogenesis have been aggressively growing in the last few decades with the recognition that angiogenesis is a hallmark of more than 50 different pathological conditions, such as rheumatoid arthritis, oculopathy, cardiovascular diseases, and tumor metastasis. During angiogenesis drug development, it is crucial to use in vitro assay systems with appropriate cell types and proper conditions to reflect the physiologic angiogenesis process. To overcome limitations of current in vitro angiogenesis assay systems using mainly endothelial cells, we developed a 3-dimensional (3D) co-culture spheroid sprouting assay system. Co-culture spheroids were produced by two human vascular cell precursors, endothelial colony forming cells (ECFCs) and mesenchymal stem cells (MSCs) with a ratio of 5 to 1. ECFCs+MSCs spheroids were embedded into type I collagen matrix to mimic the in vivo extracellular environment. A real-time cell recorder was utilized to continuously observe the progression of angiogenic sprouting from spheroids for 24 h. Live cell fluorescent labeling technique was also applied to tract the localization of each cell type during sprout formation. Angiogenic potential was quantified by counting the number of sprouts and measuring the cumulative length of sprouts generated from the individual spheroids. Five randomly-selected spheroids were analyzed per experimental group. Comparison experiments demonstrated that ECFCs+MSCs spheroids showed greater sprout number and cumulative sprout length compared with ECFCs-only spheroids. Bevacizumab, an FDA-approved angiogenesis inhibitor, was tested with the newly-developed co-culture spheroid assay system to verify its potential to screen anti-angiogenic drugs. The IC50 value for ECFCs+MSCs spheroids compared to the ECFCs-only spheroids was closer to the effective plasma concentration of bevacizumab obtained from the xenograft tumor mouse model. The present study suggests that the 3D ECFCs+MSCs spheroid angiogenesis assay system is relevant to physiologic angiogenesis, and can predict an effective plasma concentration in advance of animal experiments.

Three-dimensional co-culture spheroid angiogenesis assay system is designed to mimic the physiologic angiogenesis. Co-culture spheroids are formed by two human vascular cell precursors, ECFCs and MSCs, and embedded in collagen gel. The new system is effective for evaluating angiogenic modulators, and provides more relevant information to the in vivo study.

Studies in the field of angiogenesis have been aggressively growing in the last few decades with the recognition that angiogenesis is a hallmark of more ...

Visualizing Ocular Morphogenesis by Lightsheet Microscopy Using rx3:GFP Transgenic Zebrafish

Vertebrate eye development is a complex process that begins near the end of embryo gastrulation and requires the precise coordination of cell migration, proliferation, and differentiation. Time-lapse imagining offers unique insight to the behavior of cells during eye development because it allows us to visualize oculogenesis in vivo. Zebrafish are an excellent model to visualize this process due to their highly conserved vertebrate eye and their ability to develop rapidly and externally while remaining optically transparent. Time-lapse imaging studies of zebrafish eye development are greatly facilitated by use of the transgenic zebrafish line Tg(rx3:GFP). In the developing forebrain, rx3:GFP expression marks the cells of the single eye field, and GFP continues to be expressed as the eye field evaginates to form an optic vesicle, which then invaginates to form an optic cup. High resolution time lapse imaging of rx3:GFP expression, therefore, allows us to track the eye primordium through time as it develops into the retina. Lightsheet microscopy is an ideal method to image ocular morphogenesis over time due to its ability to penetrate thicker samples for fluorescent imaging, minimize photobleaching and phototoxicity, and image at a high speed. Here, a&#160;protocol is&#160;provided&#160;for time-lapse imaging of ocular morphogenesis using a commercially available lightsheet microscope and an image processing workstation to analyze the resulting data. This protocol details the procedures for embryo anesthesia, embedding in low melting temperature agarose, suspension in the imaging chamber, setting up the imaging parameters, and finally analyzing the imaging data using image analysis software. The resulting dataset can provide valuable insights into the process of ocular morphogenesis, as well as perturbations to this process as a result of genetic mutation, exposure to pharmacological agents, or other experimental manipulations.

Here, a&#160;protocol is&#160;provided&#160;for time-lapse imaging of ocular morphogenesis using a commercially available lightsheet microscope and an image processing workstation to analyze the resulting data. This protocol details the procedures for embryo anesthesia, embedding in low melting temperature agarose, suspension in the imaging chamber, setting up the imaging parameters, and finally analyzing the imaging data using image analysis software.&#160;

Vertebrate eye development is a complex process that begins near the end of embryo gastrulation and requires the precise coordination of cell migration, ...

An Optimized O9-1/Hydrogel System for Studying Mechanical Signals in Neural Crest Cells

Neural crest cells (NCCs) are vertebrate embryonic multipotent cells that can migrate and differentiate into a wide array of cell types that give rise to various organs and tissues. Tissue stiffness produces mechanical force, a physical cue that plays a critical role in NCC differentiation; however, the mechanism remains unclear. The method described here provides detailed information for the optimized generation of polyacrylamide hydrogels of varying stiffness, the accurate measurement of such stiffness, and the evaluation of the impact of mechanical signals in O9-1 cells, a NCC line that mimics in vivo NCCs.
Hydrogel stiffness was measured using atomic force microscopy (AFM) and indicated different stiffness levels accordingly. O9-1 NCCs cultured on hydrogels of varying stiffness showed different cell morphology and gene expression of stress fibers, which indicated varying biological effects caused by mechanical signal changes. Moreover, this established that varying the hydrogel stiffness resulted in an efficient in vitro system to manipulate mechanical signaling by altering gel stiffness and analyzing the molecular and genetic regulation in NCCs. O9-1 NCCs can differentiate into a wide range of cell types under the influence of the corresponding differentiation media, and it is convenient to manipulate chemical signals in vitro. Therefore, this in vitro system is a powerful tool to study the role of mechanical signaling in NCCs and its interaction with chemical signals, which will help researchers better understand the molecular and genetic mechanisms of neural crest development and diseases.

Detailed step-by-step protocols are described here for studying mechanical signals in vitro using multipotent O9-1 neural crest cells and polyacrylamide hydrogels of varying stiffness.

Neural crest cells (NCCs) are vertebrate embryonic multipotent cells that can migrate and differentiate into a wide array of cell types that give rise to ...

Light-Induced GFP Expression in Zebrafish Embryos using the Optogenetic TAEL/C120 System

Inducible gene expression systems are an invaluable tool for studying biological processes. Optogenetic expression systems can provide precise control over gene expression timing, location, and amplitude using light as the inducing agent. In this protocol, an optogenetic expression system is used to achieve light-inducible gene expression in zebrafish embryos. This system relies on an engineered transcription factor called TAEL based on a naturally occurring light-activated transcription factor from the bacterium E. litoralis. When illuminated with blue light, TAEL dimerizes, binds to its cognate regulatory element called C120, and activates transcription. This protocol uses transgenic zebrafish embryos that express the TAEL transcription factor under the control of the ubiquitous ubb promoter. At the same time, the C120 regulatory element drives the expression of a fluorescent reporter gene (GFP). Using a simple LED panel to deliver activating blue light, induction of GFP expression can first be detected after 30 min of illumination and reaches a peak of more than 130-fold induction after 3 h of light treatment. Expression induction can be assessed by quantitative real-time PCR (qRT-PCR) and by fluorescence microscopy. This method is a versatile and easy-to-use approach for optogenetic gene expression.

Optogenetics is a powerful tool with wide-ranging applications. This protocol demonstrates how to achieve light-inducible gene expression in zebrafish embryos using the blue light-responsive TAEL/C120 system.

Inducible gene expression systems are an invaluable tool for studying biological processes. Optogenetic expression systems can provide precise control ...