We thank Aida de la Cruz for developing and teaching the original protocol on which this version is based10. Work in the Buttitta Lab is supported by NIH grant GM086517.

1. Fly Husbandry
<ol>
 <li>Cross flies of desired genotypes in narrow plastic vials with 10 ml Yeast-Glucose Medium3 or other protein-rich media of your choice. The extensive Drosophila transgenic tools available for tissue specific expression and lineage tracing with in vivo fluorescent protein expression are described in detail elsewhere4,5. Transfer parents to fresh vials daily to obtain series of 24 hr progeny collections, or for more precise staging, collect embryos on agar ...

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A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescent+BrdU+labeling+and+nuclear+flow+sorting+of+the+Drosophila+ovary.">Fluorescent BrdU labeling and nuclear flow sorting of the Drosophila ovary.</a> Methods Mol. Biol. 247, 203-213 (2004).</li><li>Bjorklund, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+pathways+regulating+cell+size+and+cell-cycle+progression+by+RNAi.">Identification of pathways regulating cell size and cell-cycle progression by RNAi.</a> Nature. 439, 1009-1013 (2006).</li><li>Neufeld, T. P., de la Cruz, A. F., Johnston, L. A., Edgar, B. 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The protocol described here allows for analysis of cell cycle, relative cell size and relative cell number in live Drosophila tissues at various developmental stages. When this analysis is coupled with cell-type specific fluorescent protein expression or lineage tracing, detailed information can be obtained about cellular responses to discreet cell cycle or growth perturbations. As proof of principle, we disrupted quiescence in the pupal fly brain by expressing G1-S cell cycle regulators in GFP labeled cel...

Flow cytometry can be used for measurements of cell viability, relative cell size, DNA content and fluorescent protein expression in live cell populations. Due to the replication of nuclear DNA during S-phase, information about DNA content in a population of cells can be used to infer relative percentages in different cell cycle phases 1-3. This method has become a cornerstone of cell cycle analysis in model systems from yeast to mammals.
The fruit fly Drosophila melanogaster has become an excellent model system for genetic in vivo analyses of cell cycle regulation. The extensive genetic tools available in flies allow for elegant tissue specific and temporally regulated manipulations of cell cycle regulators along with in vivo fluorescent protein-based lineage tracing 4-6. Flow cytometry has been used to study DNA content in a number of Drosophila cell types, including endoreplicating cells and cultured mitotic cells 7,8. An important advance for in vivo cell cycle studies was made by de la Cruz and Edgar, with the development of a protocol for flow cytometric analysis of live diploid Drosophila imaginal discs 9,10, a protocol which has been used and adapted by many labs. This technique, when coupled with genetic in vivo lineage tracing via inducible fluorescent protein expression and tissue specific labeling, allows one to obtain information about gene manipulation effects on overall cell doubling time, cell size and to determine precise timing of cell cycle phases in vivo 9,11. However this method has thus far relied on the use of the cell permeable Hoechst 33342 DNA-intercalating dye to stain and quantify DNA in live cells, which has limited users to flow cytometers with a UV laser capable of exciting the Hoechst dye. These are generally found only in sorters (i.e. BD FACS Vantage, BD FACSAria) or expensive multicolor benchtop systems (i.e. BD LSR), usually requiring support by institutional flow core facilities.
We have modified the Hoechst-based protocol to use a new live-cell DNA dye from Invitrogen, Vybrant DyeCycle Violet. This dye is compatible with a violet 405 nm laser, more common in smaller benchtop analyzers and available in the small self-contained benchtop analyzer, the Attune Acoustic Focusing Cytometer. Here we present a detailed protocol for cell cycle analysis that can be coupled with cell type, cell size, cell number and lineage analysis in a variety of Drosophila tissues during various stages of development using DyeCycle Violet and the Attune. This protocol expands the number of cytometers suitable for such analysis with Drosophila tissues and provides examples of how this type of live cell cycle analysis can be modified for additional tissue types and developmental stages.

<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>12x75 mm Polystyrene Round-Bottom 5 ml Test Tube </td>
 <td>BD Falcon </td>
 <td>352058 </td>
 <td>5 ml tubes</td>
 </tr>
 <tr>
 <td>Attune Acoustic Focusing Cytometer</td>
 <td>Life Technologies/ Applied Biosystems</td>
 <td>4445315</td>
 <td>Blue / Violet configuration</td>
 </tr>
 <tr>
 <td>Attune Cytometer Software (version 1.2.5)</td>
 <td>Life Technologies/ Applied Biosystems</td>
 <td>Free </td>
 <td>PC only</td>
 </tr>
 <tr>
 <td>Attune Performance Tracking Beads (5 x 106 beads/ ml) </td>
 <td>Life Technologies/ Applied Biosystems</td>
 <td>4449754 </td>
 <td>For daily performance test</td>
 </tr>
 <tr>
 <td>Dumont #5 Inox forceps </td>
 <td>Fine Science Tools</td>
 <td>11251-20 </td>
 <td></td>
 </tr>
 <tr>
 <td>Embryo dishes 
 30 mm x 12mm </td>
 <td>Electron Microscopy Sciences</td>
 <td>70543-30 </td>
 <td>Glass dissection dishes </td>
 </tr>
 <tr>
 <td>Eppendorf Thermomixer</td>
 <td>Eppendorf</td>
 <td>022670051 </td>
 <td></td>
 </tr>
 <tr>
 <td>Trypsin-EDTA Solution (10x)</td>
 <td>Sigma</td>
 <td>T4174 </td>
 <td></td>
 </tr>
 <tr>
 <td>Vannas-T&uuml;bingen Spring Scissors </td>
 <td>Fine Science Tools</td>
 <td>15003-08 </td>
 <td>Straight 5mm Cutting Edge </td>
 </tr>
 <tr>
 <td>Vybrant DyeCycle Violet Stain</td>
 <td>Life Technologies/ Invitrogen</td>
 <td>V35003 </td>
 <td></td>
 </tr>
 <tr>
 <td></td>
 <td></td>
 <td></td>
 <td>Table 1. Required reagents and instruments.</td>
 </tr>
 <tr>
 <td></td>
 <td></td>
 <td></td>
 <td>Live DNA Stain Solution (10 ml):
 1 ml 10X Ca2+ Mg2+ free PBS (pH7.2) 
 9 ml 10X Trypsin-EDTA (Sigma) 
 5 &mu;l Invitrogen Vybrant DyeCycle Violet (note that this is 0.25X the recommended concentration for mammalian cells. We find that higher concentrations are toxic to Drosophila cells.)
 10X Ca2+ Mg2+ free PBS (pH7.2): 1.37M NaCl, 27 mM KCl, 100mM Na2HPO4 (dibasic), 20mM KH2PO4 (monobasic) adjusted to pH 7.2
 </td>
</tr>
 <tr>
 <td></td>
 <td></td>
 <td></td>
 <td><table border="1">
 <tbody>
 <tr>
 <td></td>
 <td>FSC</td>
 <td>SSC</td>
 <td>BL1</td>
 <td>VL1</td>
 </tr>
 <tr>
 <td>Threshold (x1000)</td>
 <td>100</td>
 <td>10</td>
 <td>10</td>
 <td>10</td>
 </tr>
 <tr>
 <td>Voltage (mV)</td>
 <td>2950</td>
 <td>4250</td>
 <td>1800</td>
 <td>1150</td>
 </tr>
 </tbody>
 </table>
Table 2. Threshold and voltage setting for the analysis in Figure 2.</td>
 </tr>
 </tbody>
 </table>

live cell cycle analysis of drosophila tissues using the attune acoustic focusing cytometer and vybrant dyecycle violet dna stain

Flow cytometry has been widely used to obtain information about DNA content in a population of cells, to infer relative percentages in different cell cycle phases. This technique has been successfully extended to the mitotic tissues of the model organism Drosophila melanogaster for genetic studies of cell cycle regulation in vivo. When coupled with cell-type specific fluorescent protein expression and genetic manipulations, one can obtain detailed information about effects on cell number, cell size and cell cycle phasing in vivo. However this live-cell method has relied on the use of the cell permeable Hoechst 33342 DNA-intercalating dye, limiting users to flow cytometers equipped with a UV laser. We have modified this protocol to use a newer live-cell DNA dye, Vybrant DyeCycle Violet, compatible with the more common violet 405nm laser. The protocol presented here allows for efficient cell cycle analysis coupled with cell type, relative cell size and cell number information, in a variety of Drosophila tissues. This protocol extends the useful cell cycle analysis technique for live Drosophila tissues to a small benchtop analyzer, the Attune Acoustic Focusing Cytometer, which can be run and maintained on a single-lab scale.

Figure 2 shows representative results for a larval wing sample, expressing GFP in the posterior half of the tissue, using the provided GFP template. Similar results are obtained with the same tissue type and expression pattern for RFP using the provided RFP template (Figure 3A). The provided templates and voltages (Table 2) are suitable for analysis of larval eyes (Figure 3B), brains and wings, as well as pupal eyes, brains (Figure 3D) and wings. H...

Watch this Scientific Journal Video about Live Cell Cycle Analysis of Drosophila Tissues using the Attune Acoustic Focusing Cytometer and Vybrant DyeCycle Violet DNA Stain at JoVE.com

Live Cell Cycle Analysis of Drosophila Tissues using the Attune Acoustic Focusing Cytometer and Vybrant DyeCycle Violet DNA Stain

A protocol for cell cycle analysis of live Drosophila tissues using the Attune Acoustic Focusing Cytometer is described. This protocol simultaneously provides information about relative cell size, cell number, DNA content and cell type via lineage tracing or tissue specific expression of fluorescent proteins in vivo.

Live Cell Cycle Analysis of Drosophila Tissues using the Attune Acoustic Focusing Cytometer and Vybrant DyeCycle Violet DNA Stain

Flow cytometry has  been widely used to obtain information about DNA content in a population of  cells, to infer relative percentages in different cell ...