We thank Gillian Stanfield for comments on the manuscript. T.A.J. is supported by the University of Utah Genetics Training Grant T32-GM007464 from NIH NIGMS.

1. Mosaic Generation
<ol>
	<li>Genetic Cross 
	w FRT19A tub:GAL80 FLP122/Y; Btl-GAL4, UAS-GFP (males) X * FRT19A/Bal (females), where * represents the mutant to be examined. Note: Set up cross at least one day prior to experiment, as this allows animals to mate appropriately.</li>
	<li>Pre-lay: Transfer cross to fly-food vials with a small smear of fresh yeast paste placed on the media. Allow to lay for 1 hr at 25 &deg;C.</li>
	<li>Lay: Transfer animals from pre-lay vial to a fresh vial with a small smear of fresh yeast paste. Allow to lay for 6 hr at 25 &deg;C.</li>
	<li>Transfer adults back to pre-lay vial for storage and use in subsequent experiments. Immediately heat shock the lay vial containing 0-6 hr old embryos for 45 min at 38 &deg;C, in a circulating water bath. Note: The surface of the food should be below the water level to verify all embryos are appropriately heat shocked.</li>
	<li>Incubate heat shocked vials at 25 &deg;C for 4-5 days until third instar larvae start to wander.</li>
</ol>
2. Screen for Mosaic Animals
<ol>
	<li>Using fine forceps gently pick wandering third-instar larvae from the sides of the vial and place them into chilled 100% glycerol in a small plastic plate.</li>
	<li>Examine larvae using a high magnification-dissecting microscope equipped with fluorescent optics. Identify larvae with mosaic expression of fluorescently labeled tracheal cells. Typically, this can be done at 10-20X magnification.</li>
</ol>
3. Heat Fixation
<ol>
	<li>Using fine forceps carefully pick mosaic animals out of the dish and place in a drop of fresh 100% glycerol on a 75x25x1 mm white glass microscope slide. Note: multiple animals can be placed in the drop (Figure 1A). 
	Animals can also be placed in a drop of glycerol directly onto a coverslip, but care must be taken during fixation (step 3.2), as the animals will heat very quickly and can become over-fixed.</li>
	<li>Place glass slide onto 70 &deg;C heat block until the animals just stop moving, no more than 20 sec for a slide, and 10 sec for a cover slip (Figure 1B). Animals will wriggle initially but stop and become rigid and elongated once dead. Note: overlong exposure to heat will damage terminal branches and lumens as well as make the GFP signal dim and diffuse. For optimal efficiency it is recommended to have the heat block in the same room as the microscopes.</li>
	<li>Using fine forceps carefully orient all larvae in the drop in a single direction, such that all larvae on the slide are oriented parallel to one another (Figure 1C).</li>
	<li>Gently place an 18x18mm micro cover glass on top of larvae (or invert the coverslip onto a glass slide) and avoid forming bubbles (Figure 1D). Note: coverslip may not lie exactly flat over larvae, this is not a problem.</li>
	<li>Image larvae within 30 min. Heat fixed terminal cells will degrade and GFP signal will become very diffuse.</li>
</ol>
4. In vivo Imaging of Tracheal Terminal Cells
<ol>
	<li>Place slide on the stage of a compound stereomicroscope. Using a 5X objective locate the two parallel dorsal trunks running from anterior to posterior on the dorsal surface of the animal (Figure 1F). Locate the two dorsal terminal cells, directly between the two dorsal trunks. This helps identify the appropriate segment for analysis.</li>
	<li>Once oriented, rotate the animals to image desired terminal cells. To do this, carefully push the coverslip on the edge with the forceps perpendicular to the long axis of the larvae, slowly rolling the larvae underneath the coverslip (Figures 1E and 1G).</li>
	<li>Selecting the appropriate terminal cells is critical for consistent results and comparisons between mutants. The fat body branch (FB) terminal cells are easily found adjacent to the dorsal trunk, lateral to the midline. The lateral group G terminal cells (LG) are easily found and are located just lateral of the ventral midline (Figure 1H). Note: in the most anterior (Tr1) and posterior (Tr10) segments the arrangement of terminal cell is divergent from other segments. We only analyze terminal cells in segments Tr2-Tr9. Dorsal terminal cells have a more stereotyped branching pattern than other tracheal terminal cells. This may depend on additional, non-cell autonomous signals, and this should be considered when deciding whether to include them in analysis.</li>
	<li>Once a terminal cell of interest has been identified, capture an image using the desired magnification; typically 10X or 20X is best (Figure 2A). Note: due to variable branching patterns, try to capture images that include as many branches and branch tips as possible.</li>
	<li>Without moving the stage, switch off the fluorescence and turn on the transmitted light to capture a brightfield image of the same cell and focal plane (Figure 2B). The lumen will be visualized as darkly contrasting within the terminal cell space. If planning on quantify terminal cell branches and lumens, collect multiple images in multiple focal planes of each terminal cell.</li>
</ol>
5. Analysis and Quantification of Terminal Cell Morphology Using ImageJ
<ol>
	<li>Open the fluorescent and brightfield images using the ImageJ (<a href="http://rsb.info.nih.gov/ij/" target="_blank">http://rsb.info.nih.gov/ij/</a>) plug-in NeuronJ (<a href="http://www.imagescience.org/meijering/software/neuronj/" target="_blank">http://www.imagescience.org/meijering/software/neuronj/</a>).</li>
	<li>Using the "Add tracings" tool, manually trace the branches and lumen of the entire terminal cell.</li>
	<li>Using the "Label tracings" tool, rename and recolor to assign each line within the trace a specific designation.</li>
	<li>Using the "Set parameters" tool, adjust the line width from 6-10 pixels (for 512x512 images obtained from the digital camera connected to the compound microscope. For higher or lower resolution cameras, the pixel width should be scaled appropriately), using all other default settings, and choose "OK". Then use the "Make snapshot" tool to take an image. Choose "Draw trace" to get a snapshot of the trace that can be shown side-by-side with the original.</li>
	<li>Select the "Measure tracings" tool and select the tracing type (i.e. which branches to measure based on the specific designations assigned in step 5.3). Next, select "Display tracing measurements" and "Clear previous measurements" then click "RUN". This will produce a spreadsheet that contains the name, label, length (in pixels), and other data for the image. This data can then be saved as a Microsoft Excel spreadsheet for further statistical analysis.</li>
</ol>

<ol>
	<li>Manning, G., Krasnow, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+the+Drosophila+Tracheal+System.">Development of the Drosophila Tracheal System.</a> The Development of Drosophila melanogaster. , 609-685 (1993).</li><li>Jarecki, J., Johnson, E., Krasnow, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxygen+regulation+of+airway+branching+in+Drosophila+is+mediated+by+branchless+FGF.">Oxygen regulation of airway branching in Drosophila is mediated by branchless FGF.</a> Cell. 99 (2), 211-220 (1999).</li><li>Ghabrial, A. S., Krasnow, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Social+interactions+among+epithelial+cells+during+tracheal+branching+morphogenesis.">Social interactions among epithelial cells during tracheal branching morphogenesis.</a> Nature. 441 (7094), 746-749 (2006).</li><li>Ruiz, O. E., Nikolova, L. S., Metzstein, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophila+Zpr1+(Zinc+Finger+Protein+1)+Is+Required+Downstream+of+Both+EGFR+And+FGFR+Signaling+in+Tracheal+Subcellular+Lumen+Formation.">Drosophila Zpr1 (Zinc Finger Protein 1) Is Required Downstream of Both EGFR And FGFR Signaling in Tracheal Subcellular Lumen Formation.</a> PLoS ONE. 7 (9), e45649 (2012).</li><li>Ghabrial, A. S., Levi, B. P., Krasnow, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+systematic+screen+for+tube+morphogenesis+and+branching+genes+in+the+Drosophila+tracheal+system.">A systematic screen for tube morphogenesis and branching genes in the Drosophila tracheal system.</a> PLoS Genetics. 7 (7), e1002087 (2011).</li><li>Baer, M. M., Bilstein, A., Leptin, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+clonal+genetic+screen+for+mutants+causing+defects+in+larval+tracheal+morphogenesis+in+Drosophila.">A clonal genetic screen for mutants causing defects in larval tracheal morphogenesis in Drosophila.</a> Genetics. 176 (4), 2279-2291 (2007).</li><li>Schottenfeld-Roames, J., Ghabrial, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Whacked+and+Rab35+polarize+dynein-motor-complex-dependent+seamless+tube+growth.">Whacked and Rab35 polarize dynein-motor-complex-dependent seamless tube growth.</a> Nat. Cell Biol. 14 (4), 386-393 (2012).</li><li>Levi, B. P., Ghabrial, A. S., Krasnow, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophila+talin+and+integrin+genes+are+required+for+maintenance+of+tracheal+terminal+branches+and+luminal+organization.">Drosophila talin and integrin genes are required for maintenance of tracheal terminal branches and luminal organization.</a> Development. 133 (12), 2383-2393 (2006).</li><li>Jones, T. A., Metzstein, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+function+for+the+PAR+complex+in+subcellular+morphogenesis+of+tracheal+terminal+cells+in+Drosophila+melanogaster.">A novel function for the PAR complex in subcellular morphogenesis of tracheal terminal cells in Drosophila melanogaster.</a> Genetics. 189 (1), 153-164 (2011).</li><li>Gervais, L., Casanova, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+coupling+of+cell+elongation+and+lumen+formation+in+a+single+cell.">In vivo coupling of cell elongation and lumen formation in a single cell.</a> Curr. Biol. 20 (4), 359-366 (2010).</li><li>Lee, T., Luo, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mosaic+analysis+with+a+repressible+cell+marker+for+studies+of+gene+function+in+neuronal+morphogenesis.">Mosaic analysis with a repressible cell marker for studies of gene function in neuronal morphogenesis.</a> Neuron. 22 (3), 451-461 (1999).</li><li>Shiga, Y., Tanaka-Matakatsu, M., Hayashi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+nuclear+GFP/&#223;-galactosidase+fusion+protein+as+a+marker+for+morphogenesis+in+living+Drosophila.">A nuclear GFP/&#223;-galactosidase fusion protein as a marker for morphogenesis in living Drosophila.</a> Dev. Growth Differ. 38, 99-106 (1996).</li><li>Meijering, E., Jacob, M., Sarria, J. -. C. F., Steiner, P., Hirling, H., Unser, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design+and+validation+of+a+tool+for+neurite+tracing+and+analysis+in+fluorescence+microscopy+images.">Design and validation of a tool for neurite tracing and analysis in fluorescence microscopy images.</a> Cytometry. Part A: The Journal of the International Society for Analytical Cytology. 58 (2), 167-176 (2004).</li><li>Centanin, L., Dekanty, A., Romero, N., Irisarri, M., Gorr, T. A., Wappner, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+autonomy+of+HIF+effects+in+Drosophila:+tracheal+cells+sense+hypoxia+and+induce+terminal+branch+sprouting.">Cell autonomy of HIF effects in Drosophila: tracheal cells sense hypoxia and induce terminal branch sprouting.</a> Dev. Cell. 14 (4), 547-558 (2008).</li></ol>

The authors declare that they have no competing financial interest.

The heat fixation technique described here is a rapid and convenient tool for imaging Drosophila larval tracheal terminal cells. Here, we use this technique to examine the branching and lumen pattern of wild-type cells. Tracheal cells expressing GFP, driven by the tracheal specific promoter breathless, can be easily visualized through the larval cuticle after heat fixation. The specific branching patterns of individual terminal cells, as well as those of the air-filled lumen, can be quickly visualized a...

Cell shape is critical for function of individual cells within an organism, as well as cells that function as part of a tissue or organ. We use Drosophila tracheal terminal cells, a component of the insect respiratory system, to investigate the molecular mechanisms that participate in controlling two conserved types of cellular morphology: branching and tube formation (lumenogenesis). Terminal cells are located at the tips of a network of branched tubes that functions to deliver oxygen to internal tissues1 and have an elaborate branched morphology which depends on an FGF signaling pathway that is controlled by local oxygen levels within target tissues2. Terminal cell branches are thin tubes, with a gas-filled subcellular lumen running through each branch. The distinct cellular architectures of terminal cells, along with the ease by which genetic analysis can be performed in Drosophila, make these cells an excellent model for investigating mechanisms of cellular outgrowth, branching, and intracellular tube formation. Terminal cells have proved a useful model for understanding some of the signaling pathways leading to branched cell differentiation, outgrowth, and maturation2-4. Using this system unbiased, forward genetic screens for cell morphogenesis mutants have been performed, yielding insights into mechanisms controlling cell shape5,6. For instance, these screens have revealed that a specific RabGAP is required for cytoskeletal polarity and vesicle trafficking in lumen formation and positioning7; that integrin-mediated adhesion is required for branch stability8; and that epithelial PAR-polarity proteins regulate polarized membrane trafficking required for both branching and lumen formation9. Other studies in terminal cells have shown that asymmetric actin accumulation and microtubule organization is required for cell elongation and lumenogenesis10. Thus, diverse, conserved cell biological mechanisms contribute to terminal cell morphogenesis.
Here, we describe a method to rapidly fix intact third-instar Drosophila larvae for analysis of terminal cell branching and lumen formation. This protocol can also be carried out on both first and second instar animals. Key to this technique is the ability to visualize terminal cells that are genetically labeled by fluorescent protein expression directly through the larval cuticle of intact animals. Since this procedure does not require any post-fixation manipulations, such as antibody staining, to observe the cells, it is well suited to high throughput analysis, including genetic or drug screening. Fluorescent protein expression reveals the structure of the cytoplasmically-filled branches. Tube formation can be monitored in parallel using brightfield microscopy to identify the gas-filled lumen, which contrasts with the surrounding fluid-filled tissues.
Included in this protocol is the method for generating genetic mosaics based on the MARCM system11, to produce homozygous mutant terminal cells labeled with fluorescent proteins in otherwise unlabeled animals. This is necessary, since terminal cells only elaborate their complex structures relatively late in development; genetic mosaics allow for bypass of gene requirements in other tissues earlier in development. To generate MARCM clones, trachea are labeled using the tracheal-specific driver breathless (btl)12. Described here is the protocol for the Drosophila X chromosome; for other chromosomes, a similar procedure can be used, with genetic reagents appropriate to the chromosome being examined. Here, trachea are labeled by expression of a cytoplasmically localized GFP, but the procedure works equally well with expression of other fluorescent proteins, such as DsRed.
Additionally, we have included a method to quantify branching patterns and lumen formation in terminal cells, based on methods developed for characterizing neuronal branch patterns13. This kind of quantitative data can be critical in discerning the precise role of genes in the branching or lumenogenesis process, as well as allowing for direct comparisons between different mutants9.

<table border="1">
	<tbody>
		<tr>
			<td>Name of Reagent/Material</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Student Dumont #5 forceps</td>
			<td>Fine Scientific Tools</td>
			<td>91150-20</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Leica MZ16 Dissecting microscope (or equivalent)</td>
			<td>Leica</td>
			<td>MZ16</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>AxioImager M1 compound microscope (or equivalent)</td>
			<td>Carl Zeiss</td>
			<td>&nbsp;</td>
			<td>Equiped with AxioCam MRm, A-PLAN 10X/0.25, EC PLAN-NEOFLUAR20X/0.5, Filter Set 38HE</td>
		</tr>
		<tr>
			<td>100% Glycerol</td>
			<td>BioExpress</td>
			<td>M152-4L</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Fly stock</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>Genotype: w FRT19A tub:GAL80 FLP122; Btl-GAL4, UAS-GFP y w FRT19A</td>
		</tr>
		<tr>
			<td>Fly stock</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
			<td>Genotype: y w FRT19A</td>
		</tr>
	</tbody>
</table>

examination of drosophila larval tracheal terminal cells by light microscopy

Cell shape is critical for cell function. However, despite the importance of cell morphology, little is known about how individual cells generate specific shapes. Drosophila tracheal terminal cells have become a powerful genetic model to identify and elucidate the roles of genes required for generating cellular morphologies. Terminal cells are a component of a branched tubular network, the tracheal system that functions to supply oxygen to internal tissues. Terminal cells are an excellent model for investigating questions of cell shape as they possess two distinct cellular architectures. First, terminal cells have an elaborate branched morphology, similar to complex neurons; second, terminal cell branches are formed as thin tubes and contain a membrane-bound intracellular lumen. Quantitative analysis of terminal cell branch number, branch organization and individual branch shape, can be used to provide information about the role of specific genetic mechanisms in the making of a branched cell. Analysis of tube formation in these cells can reveal conserved mechanisms of tubulogenesis common to other tubular networks, such as the vertebrate vasculature. Here we describe techniques that can be used to rapidly fix, image, and analyze both branching patterns and tube formation in terminal cells within Drosophila larvae. These techniques can be used to analyze terminal cells in wild-type and mutant animals, or genetic mosaics. Because of the high efficiency of this protocol, it is also well suited for genetic, RNAi-based, or drug screens in the Drosophila tracheal system.

Results are shown in Figure 2. A single lateral group (LG) terminal cell shows extensive subcellular branching (visualized by GFP; A) and a gas-filled subcellular lumen running through each of the branches (visualized by brightfield microscopy; B). These images were collected from a mosaic L3 larva, generated using the MARCM system described in sections 1 &amp; 2, and heat fixed and imaged, as described in sections 3 &amp; 4. Panels C &amp; D show a NeuronJ generated trace, as described in section 5, of ...

Watch this Scientific Journal Video about Examination of Drosophila Larval Tracheal Terminal Cells by Light Microscopy at JoVE.com

Examination of Drosophila Larval Tracheal Terminal Cells by Light Microscopy

Here, we present a method for light microscopy analysis of tracheal terminal cells in Drosophila larvae. This method allows for quick examination of branch and lumen morphology in whole animals and would be useful for analysis of individual mutants or screens for mutations affecting terminal cell development.

Examination of Drosophila Larval Tracheal Terminal Cells by Light Microscopy

Cell shape is critical for cell function. However, despite the importance of cell morphology, little is known about how individual cells generate specific ...

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10.2K Views.  University of Utah. Here, we present a method for light microscopy analysis of tracheal terminal cells in Drosophila larvae. This method allows for quick examination of branch and lumen morphology in whole animals and would be useful for analysis of individual mutants or screens for mutations affecting terminal cell development.

Video: Examination of Drosophila Larval Tracheal Terminal Cells by Light Microscopy

Dissection of Larval CNS in Drosophila Melanogaster

The central nervous system (CNS) of Drosophila larvae is complex and poorly understood.  One way to investigate the CNS is to use immunohistochemistry to examine the expression of various novel and marker proteins.  Staining of whole larvae is impractical because the tough cuticle prevents antibodies from penetrating inside the body cavity.  In order to stain these tissues it is necessary to dissect the animal prior to fixing and staining.  In this article we demonstrate how to dissect Drosophila larvae without damaging the CNS.  Begin by tearing the larva in half with a pair of fine forceps, and then turn the cuticle "inside-out" to expose the CNS.  If the dissection is performed carefully the CNS will remain attached to the cuticle.  We usually keep the CNS attached to the cuticle throughout the fixation and staining steps, and only completely remove the CNS from the cuticle just prior to mounting the samples on glass slides.  We also show some representative images of a larval CNS stained with Eve, a transcription factor expressed in a subset of neurons in the CNS.  The article concludes with a discussion of some of the practical uses of this technique and the potential difficulties that may arise.

In this article we demonstrate how to dissect the central nervous system from third instar Drosophila larvae.

The central nervous system (CNS) of Drosophila larvae is complex and poorly understood.  One way to investigate the CNS is to use immunohistochemistry to ...

Drosophila Larval NMJ Dissection

The Drosophila neuromuscular junction (NMJ) is an established model system used for the study of synaptic development and plasticity. The widespread use of the Drosophila motor system is due to its high accessibility. It can be analyzed with single-cell resolution. There are 30 muscles per hemisegment whose arrangement within the peripheral body wall are known. A total of 35 motor neurons attach to these muscles in a pattern that has high fidelity. Using molecular biology and genetics, one can create transgenic animals or mutants. Then, one can study the developmental consequences on the morphology and function of the NMJ. In order to access the NMJ for study, it is necessary to carefully dissect each larva. In this article we demonstrate how to properly dissect Drosophila larvae for study of the NMJ by removing all internal organs while leaving the body wall intact. This technique is suitable to prepare larvae for imaging, immunohistochemistry, or electrophysiology.

This protocol demonstrates how to dissect Drosophila larvae in preparation for immunohistochemistry and/or imaging of the neuromuscular junction.

The Drosophila neuromuscular junction (NMJ) is an established model system used for the study of synaptic development and plasticity. The widespread use ...

Drosophila Larval NMJ Immunohistochemistry

The Drosophila neuromuscular junction (NMJ) is an established model system used for the study of synaptic development and plasticity. The widespread use of the Drosophila motor system is due to its high accessibility. It can be analyzed with single-cell resolution. There are 30 muscles per hemisegment whose arrangement within the peripheral body wall are known. A total of 31 motor neurons attach to these muscles in a pattern that has high fidelity. Using molecular biology and genetics, one can create transgenic animals or mutants. Then, one can study the developmental consequences on the morphology and function of the NMJ. Immunohistochemistry can be used to clearly image the components of the NMJ. In this article, we demonstrate how to use antibody staining to visualize the Drosophila larval NMJ.

Drosophila Larval NMJ Immunohistochemistry

This protocol demonstrates how to perform immunohistochemistry on dissected Drosophila larva.

Presynaptically Silent Synapses Studied with Light Microscopy

Synaptic plasticity likely underlies the nervous system's ability to learn and remember and may also represent an adaptability that prevents otherwise damaging insults from becoming neurotoxic.  We have been studying a form of presynaptic plasticity that is interesting in part because it is expressed as a digital switching on and off of a presynaptic terminal s ability to release vesicles containing the neurotransmitter glutamate.  Here we demonstrate a protocol for visualizing the activity status of presynaptic terminals in dissociated cell cultures prepared from the rodent hippocampus.  The method relies on detecting active synapses using staining with a fixable form of the styryl dye FM1-43, commonly used to label synaptic vesicles.  This staining profile is compared with immunostaining of the same terminals with an antibody directed against the vesicular glutamate transporter 1 (vGluT-1), a stain designed to label all glutamate synapses regardless of activation status.   We find that depolarizing stimuli induce presynaptic silencing.  The population of synapses that is silent under baseline conditions can be activated by prolonged electrical silencing or by activation of cAMP signaling pathways.

Glutamatergic synapses can switch from an active mode to a silent mode. We demonstrate that presynaptic activity status in dissociated culture of rodent neurons is visualized using a fixable form of the FM1-43 dye to visualize active synapses and immunostaining with vGluT-1 antibody to visualize all glutamate synapses.

Synaptic plasticity likely underlies the nervous system's ability to learn and remember and may also represent an adaptability that prevents otherwise ...

Preparation of Drosophila S2 cells for Light Microscopy

The ideal experimental system would be cheap and easy to maintain, amenable to a variety of techniques, and would be supported by an extensive literature and genome sequence database. Cultured Drosophila S2 cells, the product of disassociated 20-24 hour old embryos1, possess all these properties. Consequently, S2 cells are extremely well-suited for the analysis of cellular processes, including the discovery of the genes encoding the molecular components of the process or mechanism of interest. The features of S2 cells that are most responsible for their utility are the ease with which they are maintained, their exquisite sensitivity to double-stranded (ds)RNA-mediated interference (RNAi), and their tractability to fluorescence microscopy as either live or fixed cells.
S2 cells can be grown in a variety of media, including a number of inexpensive, commercially-available, fully-defined, serum-free media2. In addition, they grow optimally and quickly at 21-24&deg;C and can be cultured in a variety of containers. Unlike mammalian cells, S2 cells do not require a regulated atmosphere, but instead do well with normal air and can even be maintained in sealed flasks.
Complementing the ease of RNAi in S2 cells is the ability to readily analyze experimentally-induced phenotypes by phase or fluorescence microscopy of fixed or live cells. S2 cells grow in culture as a single monolayer but do not display contact inhibition. Instead, cells tend to grow in colonies in dense cultures. At low density, S2 cultures grown on glass or tissue culture-treated plastic are round and loosely-attached. However, the cytology of S2 cells can be greatly improved by inducing them to flatten extensively by briefly culturing them on a surface coated with the lectin, concanavalin A (ConA)3. S2 cells can also be stably transfected with fluorescently-tagged markers to label structures or organelles of interest in live or fixed cells. Therefore, the usual scenario for the microscopic analysis of cells is this: first, S2 cells (which can possess transgenes to express tagged markers) are treated by RNAi to eliminate a target protein(s). RNAi treatment time can be adjusted to allow for differences in protein turn-over kinetics and to minimize cell trauma/death if the target protein is important for viability. Next, the treated cells are transferred to a dish containing a coverslip pre-coated with conA to induce cells to spread and tightly adhere to the glass. Finally, cells are imaged with the researcher's choice of microscopy modes. S2 cells are particularly good for studies requiring extended visualization of live cells since these cells stay healthy at room temperature and normal atmosphere.

Preparation of Drosophila S2 cells for Light Microscopy

Drosophila Schneider (S2) cells are an increasingly popular system for the discovery and functional analysis of genes. Our goal is to describe some of the microscopic techniques that make S2 cells such an increasingly important experimental system.

The ideal experimental system would be cheap and easy to maintain, amenable to a variety of techniques, and would be supported by an extensive literature ...

Dissection and Staining of Drosophila Larval Ovaries

Many organs depend on stem cells for their development during embryogenesis and for maintenance or repair during adult life. Understanding how stem cells form, and how they interact with their environment is therefore crucial for understanding development, homeostasis and disease. The ovary of the fruit fly Drosophila melanogaster has served as an influential model for the interaction of germ line stem cells (GSCs) with their somatic support cells (niche) 1, 2. The known location of the niche and the GSCs, coupled to the ability to genetically manipulate them, has allowed researchers to elucidate a variety of interactions between stem cells and their niches 3-12.
Despite the wealth of information about mechanisms controlling GSC maintenance and differentiation, relatively little is known about how GSCs and their somatic niches form during development. About 18 somatic niches, whose cellular components include terminal filament and cap cells (Figure 1), form during the third larval instar 13-17. GSCs originate from primordial germ cells (PGCs). PGCs proliferate at early larval stages, but following the formation of the niche a subgroup of PGCs becomes GSCs 7, 16, 18, 19. Together, the somatic niche cells and the GSCs make a functional unit that produces eggs throughout the lifetime of the organism.
Many questions regarding the formation of the GSC unit remain unanswered. Processes such as coordination between precursor cells for niches and stem cell precursors, or the generation of asymmetry within PGCs as they become GSCs, can best be studied in the larva. However, a methodical study of larval ovary development is physically challenging. First, larval ovaries are small. Even at late larval stages they are only 100&mu;m across. In addition, the ovaries are transparent and are embedded in a white fat body. Here we describe a step-by-step protocol for isolating ovaries from late third instar (LL3) Drosophila larvae, followed by staining with fluorescent antibodies. We offer some technical solutions to problems such as locating the ovaries, staining and washing tissues that do not sink, and making sure that antibodies penetrate into the tissue. This protocol can be applied to earlier larval stages and to larval testes as well.

Dissection and Staining of Drosophila Larval Ovaries

How niches and stem cells form during development is an important question with practical implications. In the Drosophila ovary, germ line stem cells and their somatic niches form during larval development. This video demonstrates how to dissect, stain and mount female gonads from late third instar (LL3) Drosophila larvae.

Many organs depend on stem cells for their development during embryogenesis and for maintenance or repair during adult life. Understanding how stem cells ...

In vivo Clonal Tracking of Hematopoietic Stem and Progenitor Cells Marked by Five Fluorescent Proteins using Confocal and Multiphoton Microscopy

We developed and validated a fluorescent marking methodology for clonal tracking of hematopoietic stem and progenitor cells (HSPCs) with high spatial and temporal resolution to study in vivo hematopoiesis using the murine bone marrow transplant experimental model. Genetic combinatorial marking using lentiviral vectors encoding fluorescent proteins (FPs) enabled cell fate mapping through advanced microscopy imaging. Vectors encoding five different FPs: Cerulean, EGFP, Venus, tdTomato, and mCherry were used to concurrently transduce HSPCs, creating a diverse palette of color marked cells. Imaging using confocal/two-photon hybrid microscopy enables simultaneous high resolution assessment of uniquely marked cells and their progeny in conjunction with structural components of the tissues. Volumetric analyses over large areas reveal that spectrally coded HSPC-derived cells can be detected non-invasively in various intact tissues, including the bone marrow (BM), for extensive periods of time following transplantation. Live studies combining video-rate multiphoton and confocal time-lapse imaging in 4D demonstrate the possibility of dynamic cellular and clonal tracking in a quantitative manner.

In vivo Clonal Tracking of Hematopoietic Stem and Progenitor Cells Marked by Five Fluorescent Proteins using Confocal and Multiphoton Microscopy

Combinatorial 5 fluorescent proteins marking of hematopoietic stem and progenitor cells allows in vivo clonal tracking via confocal and two-photon microscopy, providing insights into bone marrow hematopoietic architecture during regeneration. This method allows non-invasive fate mapping of spectrally-coded HSPCs-derived cells in intact tissues for extensive periods of time following transplantation.

We developed and validated a fluorescent marking methodology for clonal tracking of hematopoietic stem and progenitor cells (HSPCs) with high spatial and ...

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) ...

Measurement of Larval Activity in the Drosophila Activity Monitor

Drosophila larvae are used in many behavioral studies, yet a simple device for measuring basic parameters of larval activity has not been available. This protocol repurposes an instrument often used to measure adult activity, the TriKinetics Drosophila activity monitor (MB5 Multi-Beam Activity Monitor) to study larval activity. The instrument can monitor the movements of animals in 16 individual 8 cm glass assay tubes, using 17 infrared detection beams per tube. Logging software automatically saves data to a computer, recording parameters such as number of moves, times sensors were triggered, and animals&#8217; positions within the tubes. The data can then be analyzed to represent overall locomotion and/or position preference as well as other measurements. All data are easily accessible and compatible with basic graphing and data manipulation software. This protocol will discuss how to use the apparatus, how to operate the software and how to run a larval activity assay from start to finish.

Measurement of Larval Activity in the Drosophila Activity Monitor

This report describes a method for measuring Drosophila larval activity using the TriKinetics Drosophila Activity Monitor. The device employs infrared beams to detect movements of up to 16 individual animals. Data can be analyzed to represent motion parameters including rates and the positions of the animals within the assay chambers.

Drosophila larvae are used in many behavioral studies, yet a simple device for measuring basic parameters of larval activity has not been available. This ...

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

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

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

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