We would like to thank Dr. Sarala Pradhan for working on an earlier version of this protocol. We would like to thank NSF-IOS 1354282 for funding while we developed this protocol. We would like to thank NIH-NIDCR RO1DE025311 for funding our lab currently.

1. Collecting Eggs to Generate Larvae for Dissection
<ol>
	<li>Cross 30-40 virgin female Dpp-GAL4/TM6 Tb Hu flies to 10-15 male Sp/CyO-GFP; UAS-Dpp-GFP/TM6 Tb Hu. 
	NOTE: Any two genotypes containing Dpp-GAL4 and UAS-Dpp-GFP may be used as long as the balancers have larval markers allowing for selection of the appropriate progeny during the larval stage.</li>
	<li>To collect eggs, flip the crossed flies into a fresh vial of food and allow them to lay for 3&#8211;4 h before removing them from the vial. To encourage egg laying, a small amount of yeast paste made of granulated yeast mixed with a small amount of water can be added to the top of the food before the flies are introduced to the vial. The same set of crossed flies can be kept and used for up to 7 days of egg collections. 
	NOTE: Any standard Drosophila cornmeal food recipe should be acceptable. Used here is the food recipe described by Hazegh and Reis20.</li>
	<li>Keep the egg collection vials at 25 &#176;C for approximately 144 h until larvae are at the third instar (wandering) stage.</li>
	<li>To select the appropriate larvae for dissection (those expressing both Dpp-GAL4 and UAS-Dpp-GFP) first choose larvae that are non-Tb. These larvae will be normal length rather than short and fat.</li>
	<li>Among the non-Tb larvae there will be larvae expressing CyO-GFP and larvae expressing Dpp-GFP. To select the Dpp-GFP expressing larvae, view them under a fluorescence stereomicroscope. While both Dpp-GFP and CyO-GFP expressing larve will have some GFP fluorescence, the Dpp-GFP expressing larvae can be distinguished in that the GFP is restricted to the wing discs and the fluorescence is much less bright than the CyO-GFP expressing larvae. Select these less bright larvae for dissection.</li>
</ol>
2. Preparing Solution for Larval Imaging and Dissection
<ol>
	<li>For live imaging of wing discs, prepare modified HL3 media21 (70 mM NaCl, 5 mM KCl, 1.5 mM CaCl2 dyhydrate, 4 mM MgCl2, 10 mM NaHCO3, 5 mM trehalose dyhydrate, 115 mM sucrose, 5 mM HEPES). This media allows the wing disc to be kept alive for imaging21.</li>
	<li>Adjust pH to 7.1 using HEPES and filter with a 0.22 &#956;m filter. Use this media for both the wing disc dissections and as the mounting media for live imaging.</li>
</ol>
3. Preparing Slides for Wing Disc Mounting
<ol>
	<li>Place two pieces of colorless double-sided tape widthwise across a microscope slide, leaving a space of about 5 mm between them. The pieces of tape should be long enough that the ends of the tape lie flush with the edges of the microscope slide.</li>
	<li>Use a flat edge (such as the handle end of a pair of dissecting forceps) to press the tape firmly to the slide so that no media can seep underneath it.</li>
	<li>Place 25 &#956;L of modified HL3 media between the two pieces of tape. The wing disc will be mounted in this drop of media between pieces of tape so that the tape prevents the coverslip from crushing the disc (Figure 1A).</li>
</ol>
4. Dissecting and Mounting Wing Discs for Imaging
<ol>
	<li>Dissect larvae in the prepared modified HL3 media26.</li>
	<li>Gently tear larvae in half using two pairs of forceps and discard the posterior half of the larva.</li>
	<li>Grasp the middle of the anterior half of the larva with one pair of forceps and use another pair of closed forceps to push the mouth hooks back into the larva until the larva is completely inverted.</li>
	<li>The wing discs can be most easily found by looking for the sharp bends in the two darker colored primary branches of the tracheae that run down both sides of the larvae. The wing discs lie directly under these bends in the tracheae in an inverted larva.</li>
	<li>Gently remove the wing discs and transfer them to the 25 &#956;L of HL3 media on the prepared microscope slide. It is important to make sure that no pieces of trachea are left attached to the dissected wing discs as this can cause the discs to float, making imaging difficult.</li>
	<li>Arrange the wing disc so that the peripodial side of the wing pouch is facing upward away from the microscope slide with the disc lying flat (see Figure 1A,B).</li>
	<li>Cover the wing disc and tape with a coverslip and seal the coverslip using nail polish. Once the polish is dry, immediately proceed to the imaging steps below.</li>
</ol>
5. Imaging Dpp Release
<ol>
	<li>Image the mounted wing disc using a confocal laser scanning microscope with a 40x oil objective and 488 nm laser. The Dpp-GFP should appear as a stripe of GFP fluorescence down the center of the wing disc with small puncta of Dpp-GFP being released from this center stripe of cells.</li>
	<li>Collect images at a speed of 2 Hz for 2 min to visualize Dpp release. For best results, set the laser at a setting just strong enough to get a clear image of the Dpp-releasing cells to avoid over-bleaching during image collection. The images can be collected as a time series which can then be exported as AVI files (no compression, 3 frames/s) to obtain video files of the Dpp release.</li>
</ol>

<ol>
	<li>Ferguson, E. L., Anderson, K. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Decapentaplegic+acts+as+a+morphogen+to+organize+dorsal-ventral+pattern+in+the+Drosophila+embryo.">Decapentaplegic acts as a morphogen to organize dorsal-ventral pattern in the Drosophila embryo.</a> Cell. 71 (3), 451-461 (1992).</li><li>Ferguson, E. L., Anderson, K. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Localized+enhancement+and+repression+of+the+activity+of+the+TGF-beta+family+member,+decapentaplegic,+is+necessary+for+dorsal-ventral+pattern+formation+in+the+Drosophila+embryo.">Localized enhancement and repression of the activity of the TGF-beta family member, decapentaplegic, is necessary for dorsal-ventral pattern formation in the Drosophila embryo.</a> Development. 114 (3), 583-597 (1992).</li><li>Wharton, K. A., Ray, R. P., Gelbart, W. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+activity+gradient+of+decapentaplegic+is+necessary+for+the+specification+of+dorsal+pattern+elements+in+the+Drosophila+embryo.">An activity gradient of decapentaplegic is necessary for the specification of dorsal pattern elements in the Drosophila embryo.</a> Development. 117 (2), 807-822 (1993).</li><li>Raftery, L. A., Twombly, V., Wharton, K., Gelbart, W. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetic+screens+to+identify+elements+of+the+decapentaplegic+signaling+pathway+in+Drosophila.">Genetic screens to identify elements of the decapentaplegic signaling pathway in Drosophila.</a> Genetics. 139 (1), 241-254 (1995).</li><li>Raftery, L. A., Sanicola, M., Blackman, R. K., Gelbart, W. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+relationship+of+decapentaplegic+and+engrailed+expression+in+Drosophila+imaginal+disks:+do+these+genes+mark+the+anterior-posterior+compartment+boundary.">The relationship of decapentaplegic and engrailed expression in Drosophila imaginal disks: do these genes mark the anterior-posterior compartment boundary.</a> Development. 113 (1), 27-33 (1991).</li><li>Blackman, R. K., Sanicola, M., Raftery, L. A., Gillevet, T., Gelbart, W. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+extensive+3'+cis-regulatory+region+directs+the+imaginal+disk+expression+of+decapentaplegic,+a+member+of+the+TGF-beta+family+in+Drosophila.">An extensive 3' cis-regulatory region directs the imaginal disk expression of decapentaplegic, a member of the TGF-beta family in Drosophila.</a> Development. 111 (3), 657-666 (1991).</li><li>de Celis, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+and+function+of+decapentaplegic+and+thick+veins+during+the+differentiation+of+the+veins+in+the+Drosophila+wing.">Expression and function of decapentaplegic and thick veins during the differentiation of the veins in the Drosophila wing.</a> Development. 124 (5), 1007-1018 (1997).</li><li>De Celis, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pattern+formation+in+the+Drosophila+wing:+The+development+of+the+veins.">Pattern formation in the Drosophila wing: The development of the veins.</a> Bioessays. 25 (5), 443-451 (2003).</li><li>Letsou, A., 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=Drosophila+Dpp+signaling+is+mediated+by+the+punt+gene+product:+a+dual+ligand-binding+type+II+receptor+of+the+TGF+beta+receptor+family.">Drosophila Dpp signaling is mediated by the punt gene product: a dual ligand-binding type II receptor of the TGF beta receptor family.</a> Cell. 80 (6), 899-908 (1995).</li><li>Nellen, D., Affolter, M., Basler, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Receptor+serine/threonine+kinases+implicated+in+the+control+of+Drosophila+body+pattern+by+decapentaplegic.">Receptor serine/threonine kinases implicated in the control of Drosophila body pattern by decapentaplegic.</a> Cell. 78 (2), 225-237 (1994).</li><li>Raftery, L. A., Sutherland, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TGF-beta+family+signal+transduction+in+Drosophila+development:+from+Mad+to+Smads.">TGF-beta family signal transduction in Drosophila development: from Mad to Smads.</a> Developmental Biology. 210 (2), 251-268 (1999).</li><li>Dahal, G. R., Pradhan, S. J., Bates, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inwardly+rectifying+potassium+channels+regulate+Dpp+release+in+the+Drosophila+wing+disc.">Inwardly rectifying potassium channels regulate Dpp release in the Drosophila wing disc.</a> Development. 144 (15), 2771-2783 (2017).</li><li>Dahal, G. R., 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=An+inwardly+rectifying+K++channel+is+required+for+patterning.">An inwardly rectifying K+ channel is required for patterning.</a> Development. 139 (19), 3653-3664 (2012).</li><li>George, L. F., 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=Ion+Channel+Contributions+to+Wing+Development+in+Drosophila+melanogaster.">Ion Channel Contributions to Wing Development in Drosophila melanogaster.</a> G3. 9 (4), 999-1008 (2019).</li><li>Huang, H., Liu, S., Kornberg, T. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glutamate+signaling+at+cytoneme+synapses.">Glutamate signaling at cytoneme synapses.</a> Science. 363 (6430), 948-955 (2019).</li><li>Teleman, A. A., Cohen, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dpp+gradient+formation+in+the+Drosophila+wing+imaginal+disc.">Dpp gradient formation in the Drosophila wing imaginal disc.</a> Cell. 103 (6), 971-980 (2000).</li><li>Miesenbock, G., De Angelis, D. A., Rothman, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualizing+secretion+and+synaptic+transmission+with+pH-sensitive+green+fluorescent+proteins.">Visualizing secretion and synaptic transmission with pH-sensitive green fluorescent proteins.</a> Nature. 394 (6689), 192-195 (1998).</li><li>Dahal, G. R., Pradhan, S. J., Bates, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inwardly+rectifying+potassium+channels+influence+Drosophila+wing+morphogenesis+by+regulating+Dpp+release.">Inwardly rectifying potassium channels influence Drosophila wing morphogenesis by regulating Dpp release.</a> Development. 144 (15), 2771-2783 (2017).</li><li>Duffy, J. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=GAL4+system+in+Drosophila:+a+fly+geneticist's+Swiss+army+knife.">GAL4 system in Drosophila: a fly geneticist's Swiss army knife.</a> Genesis. 34 (1-2), 1-15 (2002).</li><li>Hazegh, K. E., Reis, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Buoyancy-based+Method+of+Determining+Fat+Levels+in+Drosophila.">A Buoyancy-based Method of Determining Fat Levels in Drosophila.</a> Journal of Visualized Experiments. (117), e54744 (2016).</li><li>Feng, Y., Ueda, A., Wu, C. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+modified+minimal+hemolymph-like+solution,+HL3.1,+for+physiological+recordings+at+the+neuromuscular+junctions+of+normal+and+mutant+Drosophila+larvae.">A modified minimal hemolymph-like solution, HL3.1, for physiological recordings at the neuromuscular junctions of normal and mutant Drosophila larvae.</a> Journal of Neurogenetics. 18 (2), 377-402 (2004).</li><li>Hsiung, F., Ramirez-Weber, F. A., Iwaki, D. D., Kornberg, T. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dependence+of+Drosophila+wing+imaginal+disc+cytonemes+on+Decapentaplegic.">Dependence of Drosophila wing imaginal disc cytonemes on Decapentaplegic.</a> Nature. 437 (7058), 560-563 (2005).</li><li>Roy, S., Hsiung, F., Kornberg, T. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Specificity+of+Drosophila+cytonemes+for+distinct+signaling+pathways.">Specificity of Drosophila cytonemes for distinct signaling pathways.</a> Science. 332 (6027), 354-358 (2011).</li><li>Kornberg, T. B., Roy, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cytonemes+as+specialized+signaling+filopodia.">Cytonemes as specialized signaling filopodia.</a> Development. 141 (4), 729-736 (2014).</li><li>Roy, S., Huang, H., Liu, S., Kornberg, T. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cytoneme-mediated+contact-dependent+transport+of+the+Drosophila+decapentaplegic+signaling+protein.">Cytoneme-mediated contact-dependent transport of the Drosophila decapentaplegic signaling protein.</a> Science. 343 (6173), 1244624 (2014).</li><li>Kornberg, T. 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The authors have nothing to disclose.

BMPs such as Dpp make their significant impact when they bind a complex of membrane bound receptors to cause a cascade of intracellular signaling in neighboring or apparently distant cells. Dr. Thomas Kornberg&#8217;s lab has shown that cells that produce the Dpp signal contact cells that receive the signal using actin based thin filapodia-like structures called cytonemes15,24,25. These data suggest that developmental cell-cell ...

Bone Morphogenetic Proteins (BMPs) are essential for early embryogenesis and patterning of adult structures. BMPs are produced and secreted to affect transcription of target genes needed for growth and cell differentiation in responding cells. Decapentaplegic (Dpp) is a Drosophila homolog of BMP4 that is important for development of embryonic and adult structures like the wing1,2,3,4. Several groups have focused on the role of Dpp in patterning adult fly wings because 1) the wings are comprised of two transparent epithelia sheets with a consistent venation pattern that can be easily assessed; 2) the wing discs are also reasonably flat, can be cultured outside of the larva, and are simple to image and quantify differences in pattern; and 3) the wing pattern development is sensitive to Dpp such that small perturbations in the pathway will impact wing venation pattern.
Dpp is produced in cells located in the anterior/posterior boundary of the wing disc5,6,7,8. Dpp binds to a complex of type 1 and type 2 serine/threonine kinase receptors9,10. Upon Dpp binding, the type 2 receptor phosphorylates the type 1 receptor which then phosphorylates Mothers against Dpp (Mad), a Smad 1/5/8 homolog. Phosphorylated SMAD recruits an additional co-Smad (Medea), which enables it enter to the nucleus where it regulates target genes, leading to downstream effects such as proliferation or differentiation4,11.
Recently, the Bates Lab has shown that the improper release of Dpp within the wing disc can lead to a decrease in Mad phosphorylation, reduction in target gene expression, and wing patterning defects12,13. Several ion channels impact development of the Drosophila wing and associated structures14,15. These ion channels could also be involved in Dpp release. In determining the mechanism of morphogen release, it is important that there is a method to visualize release events.
Drs. Aurelio Teleman and Stephen Cohen created a Dpp-GFP fusion protein which is able to rescue loss of Dpp, meaning that it is biologically active and is released in a biologically relevant manner16. Here, we describe how we visualize Dpp release events using this Dpp-GFP. This fusion protein is particularly useful because GFP is pH sensitive such that when it is in acidic vesicles, the fluorescence is quenched17. Therefore, when a protein tagged with GFP is released from a vesicle into the more neutral extracellular environment, GFP fluorescence intensity increases17. We took advantage of the pH sensitivity of GFP to determine if Dpp-GFP resides in acidic vesicles. We imaged wing discs expressing Dpp-GFP before and after the addition of ammonium chloride, which neutralizes intracellular compartments vesicles18. We found a significant increase in fluorescence of puncta after the addition of ammonium chloride, suggesting that intracellular Dpp-GFP is quenched before the addition of ammonium chloride18. We conclude that intracellular Dpp-GFP resides in acidic membrane-bound compartments, such as vesicles, and is unquenched upon addition of ammonium chloride to neutralize the pH of intracellular compartments18. This makes live imaging of Dpp-GFP a useful technique to visualize the dynamics of Dpp in the Drosophila wing disc as it is released from acidic compartments into the extracellular environment.
Here, we describe the method we use to visualize Dpp release events using Dpp-GFP. Dpp-GFP can be expressed in its native pattern in Drosophila wing discs using the UAS-GAL4 system19. This is the method that was used to determine that Irk channels impact Dpp release18. We validated the method by live-imaging z-stacks. We do not see Dpp-GFP puncta moving within the plane of focus in time series if we acquired in one plane of focus. We also do not see movement of Dpp-GFP puncta if we imaged in a z-stack. We conclude that the Dpp-GFP puncta seen using this method are release events rather than movement of vesicles intracellularly. This method of live-imaging of Dpp-GFP could potentially be used to test other putative modifiers of Dpp release for their impact on Dpp dynamics or could be modified to look at the dynamics of other ligands

<table>
	<tbody>
		<tr>
			<td>Baker&#39;s yeast</td>
			<td>Red Star</td>
			<td>&#160;</td>
			<td>&#160;</td>
		</tr>
		<tr>
			<td>CaCl2 dyhydrate</td>
			<td>Fisher Scientific</td>
			<td>C79-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Coverslips</td>
			<td>VWR</td>
			<td>484-457</td>
			<td></td>
		</tr>
		<tr>
			<td>Double-sided tape</td>
			<td>Scotch</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Drosophila Agar Type II</td>
			<td>Apex</td>
			<td>66-104</td>
			<td></td>
		</tr>
		<tr>
			<td>Drosophila melanogaster: Dpp-GAL4/TM6 Tb Hu</td>
			<td></td>
			<td></td>
			<td>This stock will soon be made available at Bloomington Drosophila Stock Center</td>
		</tr>
		<tr>
			<td>Drosophila melanogaster: Sp/CyO-GFP; UAS-Dpp-GFP/TM6 Tb Hu</td>
			<td></td>
			<td></td>
			<td>This stock will soon be made available at Bloomington Drosophila Stock Center</td>
		</tr>
		<tr>
			<td>Dumont Tweezers #5</td>
			<td>World Precision Instruments</td>
			<td>500233</td>
			<td>Forceps for dissecting</td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Sigma Aldrich</td>
			<td>H3375</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Fisher Scientific</td>
			<td>AC193780010</td>
			<td></td>
		</tr>
		<tr>
			<td>Light Corn Syrup</td>
			<td>Karo</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Malt Extract</td>
			<td>Breiss</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MgCl2</td>
			<td>Fisher Scientific</td>
			<td>AC223210010</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope slides</td>
			<td>Sigma Aldrich</td>
			<td>S8400</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Fisher Scientific</td>
			<td>S271-500</td>
			<td></td>
		</tr>
		<tr>
			<td>NaHCO3</td>
			<td>RPI</td>
			<td>S22060-1000.0</td>
			<td></td>
		</tr>
		<tr>
			<td>Nail polish</td>
			<td>Electron Micsroscopy Sciences</td>
			<td>72180</td>
			<td></td>
		</tr>
		<tr>
			<td>Propionic Acid</td>
			<td>VWR</td>
			<td>U330-09</td>
			<td></td>
		</tr>
		<tr>
			<td>Soy Flour</td>
			<td>ADM Specialty Ingredients</td>
			<td>062-100</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Fisher Scientific</td>
			<td>S5-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Fisher</td>
			<td>S512</td>
			<td></td>
		</tr>
		<tr>
			<td>Tegosept</td>
			<td>Genesee Scientific</td>
			<td>20-259</td>
			<td></td>
		</tr>
		<tr>
			<td>Trehalose dyhydrate</td>
			<td>Chem-Impex International, Inc.</td>
			<td>00766</td>
			<td></td>
		</tr>
		<tr>
			<td>Yellow Corn Meal</td>
			<td>Quaker</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Zeiss LSM 780 confocal microscope</td>
			<td>Zeiss</td>
			<td></td>
			<td>Microscope for live imaging</td>
		</tr>
		<tr>
			<td>Zeiss SteREO Discovery.V8 microscope</td>
			<td>Zeiss</td>
			<td></td>
			<td>Microscope for dissections</td>
		</tr>
	</tbody>
</table>

imaging dpp release from a drosophila wing disc

The transforming Growth Factor-beta (TGF-&#946;) superfamily is essential for early embryonic patterning and development of adult structures in multicellular organisms. The TGF-&#946; superfamily includes TGF-&#946;, bone morphogenetic protein (BMPs), Activins, Growth and Differentiation Factors, and Nodals. It has long been known that the amount of ligand exposed to cells is important for its effects. It was thought that long-range concentration gradients set up embryonic pattern. However, recently it has become clear that the timing of exposure to these ligands is also important for their downstream transcriptional consequences. A TGF-&#946; superfamily ligand cannot have a developmental consequence until it is released from the cell in which it was produced. Until recently, it was difficult to determine when these ligands were released from cells. Here we show how to measure the release of a Drosophila BMP called Decapentaplegic (Dpp) from the cells of the wing primordium or wing disc. This method could be modified for other systems or signaling ligands.

Figure 2 shows representative live-imaging results of this protocol. When the protocol is successful, Dpp-GFP can be seen as a stripe down the center of the wing disc with nuclei visible as non-fluorescent circles within the Dpp-GFP region (Figure 2). Dpp-GFP release is visible as fluorescent puncta that appear and disappear. We have observed Dpp-GFP fluorescence appearing and disappearing in the cell bodies and far from the cell bodies. Dpp signaling is depende...

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Imaging Dpp Release from a Drosophila Wing Disc

The timing of exposure to ligands may impact their developmental consequences. Here we show how to image release of a Drosophila bone morphogenetic protein (BMP) called Dpp from cells of the wing disc.

Imaging Dpp Release from a Drosophila Wing Disc

The transforming Growth Factor-beta (TGF-&#946;) superfamily is essential for early embryonic patterning and development of adult structures in ...

imaging-dpp-release-from-a-drosophila-wing-disc

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JoVE Journal

Developmental Biology

5.5K Views.  University of Colorado School of Medicine. The timing of exposure to ligands may impact their developmental consequences. Here we show how to image release of a Drosophila bone morphogenetic protein (BMP) called Dpp from cells of the wing disc.

Video: Imaging Dpp Release from a Drosophila Wing Disc

Live-imaging of the Drosophila Pupal Eye

Inherent processes of Drosophila pupal development can shift and distort the eye epithelium in ways that make individual cell behavior difficult to track during live cell imaging. These processes include: retinal rotation, cell growth and organismal movement. Additionally, irregularities in the topology of the epithelium, including subtle bumps and folds often introduced as the pupa is prepared for imaging, make it challenging to acquire in-focus images of more than a few ommatidia in a single focal plane. The workflow outlined here remedies these issues, allowing easy analysis of cellular processes during Drosophila pupal eye development. Appropriately-staged pupae are arranged in an imaging rig that can be easily assembled in most laboratories. Ubiquitin-DE-Cadherin:GFP and GMR-GAL4&#8211;driven UAS-&#945;-catenin:GFP are used to visualize cell boundaries in the eye epithelium 1-3. After deconvolution is applied to fluorescent images captured at multiple focal planes, maximum projection images are generated for each time point and enhanced using image editing software. Alignment algorithms are used to quickly stabilize superfluous motion, making individual cell behavior easier to track.

Live-imaging of the Drosophila Pupal Eye

This protocol presents an efficient method for imaging the live Drosophila pupal eye neuroepithelium. This method compensates for tissue movement and uneven topology, enhances visualization of cell boundaries through the use of multiple GFP-tagged junction proteins, and uses an easily-assembled imaging rig.

Inherent processes of Drosophila pupal development can shift and distort the eye epithelium in ways that make individual cell behavior difficult to track ...

Upright Imaging of Drosophila Egg Chambers

Drosophila melanogaster oogenesis provides an ideal context for studying varied developmental processes since the ovary is relatively simple in architecture, is well-characterized, and is amenable to genetic analysis. Each egg chamber consists of germ-line cells surrounded by a single epithelial layer of somatic follicle cells. Subsets of follicle cells undergo differentiation during specific stages to become several different cell types. Standard techniques primarily allow for a lateral view of egg chambers, and therefore a limited view of follicle cell organization and identity. The upright imaging protocol describes a mounting technique that enables a novel, vertical view of egg chambers with a standard confocal microscope. Samples are first mounted between two layers of glycerin jelly in a lateral (horizontal) position on a glass microscope slide. The jelly with encased egg chambers is then cut into blocks, transferred to a coverslip, and flipped to position egg chambers upright. Mounted egg chambers can be imaged on either an upright or an inverted confocal microscope. This technique enables the study of follicle cell specification, organization, molecular markers, and egg development with new detail and from a new perspective.

Upright Imaging of Drosophila Egg Chambers

The upright imaging method described in this protocol allows for the detailed visualization of the poles of a developing Drosophila melanogaster egg. This end-on view provides a new perspective into the arrangements and morphologies of multiple cell types in the follicular epithelium.

Drosophila melanogaster oogenesis provides an ideal context for studying varied developmental processes since the ovary is relatively simple in ...

Imaging Calcium in Drosophila at Egg Activation

Egg activation is a universal process that includes a series of events to allow the fertilized egg to complete meiosis and initiate embryonic development. One aspect of egg activation, conserved across all organisms examined, is a change in the intracellular concentration of calcium (Ca2+) often termed a 'Ca2+ wave'. While the speed and number of oscillations of the Ca2+ wave varies between species, the change in intracellular Ca2+ is key in bringing about essential events for embryonic development. These changes include resumption of the cell cycle, mRNA regulation, cortical granule exocytosis, and rearrangement of the cytoskeleton.
In the mature Drosophila egg, activation occurs in the female oviduct prior to fertilization, initiating a series of Ca2+-dependent events. Here we present a protocol for imaging the Ca2+ wave in Drosophila. This approach provides a manipulable model system to interrogate the mechanism of the Ca2+ wave and the downstream changes associated with it.

Imaging Calcium in Drosophila at Egg Activation

This article describes an adaptable ex vivo protocol for visualizing Ca2+ during egg activation in Drosophila.

Egg activation is a universal process that includes a series of events to allow the fertilized egg to complete meiosis and initiate embryonic development. ...

Long-term Live Imaging of Drosophila Eye Disc

Live imaging provides the ability to continuously track dynamic cellular and developmental processes in real time. Drosophila larval imaginal discs have been used to study many biological processes, such as cell proliferation, differentiation, growth, migration, apoptosis, competition, cell-cell signaling, and compartmental boundary formation. However, methods for the long-term ex vivo culture and live imaging of the imaginal discs have not been satisfactory, despite many efforts. Recently, we developed a method for the long-term ex vivo culture and live imaging of imaginal discs for up to 18 h. In addition to using a high insulin concentration in the culture medium, a low-melting agarose was also used to embed the disc to prevent it from drifting during the imaging period. This report uses the eye-antennal discs as an example. Photoreceptor R3/4-specific m&#948;0.5-Ga4 expression was followed to demonstrate that photoreceptor differentiation and ommatidial rotation can be observed during a 10 h live imaging period. This is a detailed protocol describing this simple method.

Long-term Live Imaging of Drosophila Eye Disc

This protocol describes a detailed method for the long-term ex vivo culture and live imaging of a Drosophila imaginal disc. It demonstrates photoreceptor differentiation and ommatidial rotation within the 10 h period of live imaging of the eye disc. The protocol is simple and does not require expensive setup.

Live imaging provides the ability to continuously track dynamic cellular and developmental processes in real time. Drosophila larval imaginal discs have ...

In Vivo Imaging of Muscle-tendon Morphogenesis in Drosophila Pupae

Muscles together with tendons and the skeleton enable animals including humans to move their body parts. Muscle morphogenesis is highly conserved from animals to humans. Therefore, the powerful Drosophila model system can be used to study concepts of muscle-tendon development that can also be applied to human muscle biology. Here, we describe in detail how morphogenesis of the adult muscle-tendon system can be easily imaged in living, developing Drosophila pupae. Hence, the method allows investigating proteins, cells and tissues in their physiological environment. In addition to a step-by-step protocol with helpful tips, we provide a comprehensive overview of fluorescently tagged marker proteins that are suitable for studying the muscle-tendon system. To highlight the versatile applications of the protocol, we show example movies ranging from visualization of long-term morphogenetic events &#8211; occurring on the time scale of hours and days &#8211; to visualization of short-term dynamic processes like muscle twitching occurring on time scale of seconds. Taken together, this protocol should enable the reader to design and perform live-imaging experiments for investigating muscle-tendon morphogenesis in the intact organism.

In Vivo Imaging of Muscle-tendon Morphogenesis in Drosophila Pupae

Here, we present an easy-to-use and versatile method to perform live imaging of developmental processes in general and muscle-tendon morphogenesis in particular in living Drosophila pupae.

Muscles together with tendons and the skeleton enable animals including humans to move their body parts. Muscle morphogenesis is highly conserved from ...

Live Imaging and Analysis of Muscle Contractions in Drosophila Embryo

Coordinated muscle contractions are a form of rhythmic behavior seen early during development in Drosophila embryos. Neuronal sensory feedback circuits are required to control this behavior. Failure to produce the rhythmic pattern of contractions can be indicative of neurological abnormalities. We previously found that defects in protein O-mannosylation, a posttranslational protein modification, affect the axon morphology of sensory neurons and result in abnormal coordinated muscle contractions in embryos. Here, we present a relatively simple method for recording and analyzing the pattern of peristaltic muscle contractions by live imaging of late stage embryos up to the point of hatching, which we used to characterize the muscle contraction phenotype of protein O-mannosyltransferase mutants. Data obtained from these recordings can be used to analyze muscle contraction waves, including frequency, direction of propagation and relative amplitude of muscle contractions at different body segments. We have also examined body posture and taken advantage of a fluorescent marker expressed specifically in muscles to accurately determine the position of the embryo midline. A similar approach can also be utilized to study various other behaviors during development, such as embryo rolling and hatching.

Live Imaging and Analysis of Muscle Contractions in Drosophila Embryo

Here, we present a method to record embryonic muscle contractions in Drosophila embryos in a non-invasive and detail-oriented manner.

Coordinated muscle contractions are a form of rhythmic behavior seen early during development in Drosophila embryos. Neuronal sensory feedback circuits ...

Thawing, Culturing, and Cryopreserving Drosophila Cell Lines

There are currently over 160 distinct Drosophila cell lines distributed by the Drosophila Genomics Resource Center (DGRC). With genome engineering, the number of novel cell lines is expected to increase. The DGRC aims to familiarize researchers with using Drosophila cell lines as an experimental tool to complement and drive their research agenda. Procedures for working with a variety of Drosophila cell lines with distinct characteristics are provided, including protocols for thawing, culturing, and cryopreserving cell lines. Importantly, this publication demonstrates the best practices required to work with Drosophila cell lines to minimize the risk of contaminations from adventitious microorganisms or from other cell lines. Researchers who become familiar with these procedures will be able to delve into the many applications that use Drosophila cultured cells including biochemistry, cell biology and functional genomics.

Thawing, Culturing, and Cryopreserving Drosophila Cell Lines

Drosophila cell lines are important reagents for both fundamental and biomedical research. This article provides protocols for thawing, subculturing, and the cryopreservation of commonly used Drosophila cell lines to assist researchers in incorporating the use of these reagents in their research.

There are currently over 160 distinct Drosophila cell lines distributed by the Drosophila Genomics Resource Center (DGRC). With genome engineering, the ...

A Direct and Simple Method to Assess Drosophila melanogaster's Viability from Embryo to Adult

In Drosophila melanogaster, viability assays are used to determine the fitness of certain genetic backgrounds. Allelic variations can result in partial or complete loss of viability at different stages of development. Our lab has developed a method to assess viability in Drosophila from embryo to fully mature adult. The method relies on quantifying the number of progeny present at different stages during development, starting with hatched embryos. After embryos have been quantified, additional stages are counted, including L1/L2, pupae, and mature adults. After all stages have been examined, a statistical analysis such as the chi-square test is used to determine if there is a significant difference between the starting number of progeny (hatched embryos) and later stages culminating in the observed number of adults, thus rejecting or accepting the null hypothesis (that the number of hatched embryos will be equal to the number of larvae, pupae, and adults recorded throughout the stages of development). The primary advantage of this assay is its simplicity and accuracy, as it does not require an embryo rinse to transfer them to the food vial, avoiding losses from technical errors. Although the protocol described here does not directly examine L2/L3 larvae, additional steps can be added to account for these. Comparing the number of hatched embryos, L1, pupae, and adults can help determine if viability was compromised during the L2/L3 stages for further studies (the use of colored food helps with visual identification of larvae). Overall, this method can help Drosophila researchers and educators determine when viability is compromised during the fly life cycle. Routine assessment of stocks using this assay can prevent accumulation of secondary mutations that may affect the phenotype of the originally isolated mutant, especially if the original mutations affect fitness. For this reason, our lab maintains multiple copies of each of our Dm ime4 alleles and routinely checks the purity of each stock with this method in addition to other molecular analyses.&#160;

A Direct and Simple Method to Assess Drosophila melanogaster's Viability from Embryo to Adult

This protocol is designed to assess the viability of Drosophila at every developmental stage, from embryo to adult. The method can be used to determine and compare the viability of different genotypes or growth conditions.

In Drosophila melanogaster, viability assays are used to determine the fitness of certain genetic backgrounds. Allelic variations can result in partial or ...

Whole Animal Imaging of Drosophila melanogaster using Microcomputed Tomography

Biomedical imaging tools permit investigation of molecular mechanisms across spatial scales, from genes to organisms. Drosophila melanogaster, a well-characterized model organism, has benefited from the use of light and electron microscopy to understand gene function at the level of cells and tissues. The application of imaging platforms that allow for an understanding of gene function at the level of the entire intact organism would further enhance our knowledge of genetic mechanisms. Here a whole animal imaging method is presented that outlines the steps needed to visualize Drosophila at any developmental stage using microcomputed tomography (&#181;-CT). The advantages of &#181;-CT include commercially available instrumentation and minimal hands-on time to produce accurate 3D information at micron-level resolution without the need for tissue dissection or clearing methods. Paired with software that accelerate image analysis and 3D rendering, detailed morphometric analysis of any tissue or organ system can be performed to better understand mechanisms of development, physiology, and anatomy for both descriptive and hypothesis testing studies. By utilizing an imaging workflow that incorporates the use of electron microscopy, light microscopy, and &#181;-CT, a thorough evaluation of gene function can be performed, thus furthering the usefulness of this powerful model organism.

Whole Animal Imaging of Drosophila melanogaster using Microcomputed Tomography

A protocol is presented that allows for the visualization of intact Drosophila melanogaster at any stage of development using microcomputed tomography.

Biomedical imaging tools permit investigation of molecular mechanisms across spatial scales, from genes to organisms. Drosophila melanogaster, a ...

Dissection and Live-Imaging of the Late Embryonic Drosophila Gonad

The Drosophila melanogaster male embryonic gonad is an advantageous model to study various aspects of developmental biology including, but not limited to, germ cell development, piRNA biology, and niche formation. Here, we present a dissection technique to live-image the gonad ex vivo during a period when in vivo live-imaging is highly ineffective. This protocol outlines how to transfer embryos to an imaging dish, choose appropriately-staged male embryos, and dissect the gonad from its surrounding tissue while still maintaining its structural integrity. Following dissection, gonads can be imaged using a confocal microscope to visualize dynamic cellular processes. The dissection procedure requires precise timing and dexterity, but we provide insight on how to prevent common mistakes and how to overcome these challenges. To our knowledge this is the first dissection protocol for the Drosophila embryonic gonad, and will permit live-imaging during an otherwise inaccessible window of time. This technique can be combined with pharmacological or cell-type specific transgenic manipulations to study any dynamic processes occurring within or between the&#160;cells in their natural gonadal environment.

Dissection and Live-Imaging of the Late Embryonic Drosophila Gonad

Here, we provide a dissection protocol required to live-image the late embryonic Drosophila male gonad. This protocol will permit observation of dynamic cellular processes under normal conditions or after transgenic or pharmacological manipulation.

The Drosophila melanogaster male embryonic gonad is an advantageous model to study various aspects of developmental biology including, but not limited to, ...