Name: examination of drosophila larval tracheal terminal cells by light microscopy
Uploaded: 2013-07-09T13:00:00
Description: Watch this Scientific Journal Video about Examination of Drosophila Larval Tracheal Terminal Cells by Light Microscopy at JoVE.com

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....

<ol>
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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. 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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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