We appreciate assistance from members of the fly community, particularly Dr. Denise Montell, Dr. Lynn Cooley, and Dr. Pernille Rorth, for reagents. We thank Flybase, the Bloomington Drosophila Stock Center, and Developmental Studies Hybridoma Bank for information and providing fly stocks and antibodies, respectively. LM is supported by the Department of Education&#160;Grant, Graduate Assistance in the Areas of National Need (GAANN) training fellowship (P200A120017) and by a NIGMS Initiative for Maximizing Student Development Grant (2 R25-GM55036). A portion of the microscopy work was supported by NSF MRI grant DBI-0722569 and the Keith R. Porter Core Imaging Facility. Research was supported in part by a NSF CAREER Award (1054422) and a Basil O&#8217;Connor Starter Scholar Award from the March of Dimes, both awarded to MSG.

1. Dissection of Ovarioles
<ol>
	<li>Transfer about fifteen 2-4-day-old female flies and a few males to a fresh fly food vial with added active dry yeast. Use cotton as a plug for the vials, and add a few drops of water to the cotton to keep the humidity high.</li>
	<li>Place vial in a 25 &#176;C incubator for 14-16 hr to maximize the number of stage 8-10 egg chambers. 
	NOTE: Incubation time varies depending on temperature and desired stage.</li>
	<li>Prepare dissection media, 0.1M KPO4 and NP40 solutions as needed for the next day (see Materials).</li>
	<li>Anesthetize the flies using CO2, and place under a dissection microscope. Pipet several drops of dissection media into each cavity in the glass depression slide.</li>
	<li>Hold forceps in each hand at an approximately 30&#176; angle to the table top and orient one female fly with the wings down. With your non-dominant hand, pick up the female using forceps, grasping her at the anterior of the abdomen, near the thorax, and submerge her into the dissection media in the depression slide (Figure 1A inset).</li>
	<li>With the other pair of forceps, grasp the exoskeleton at the ventral posterior of the abdomen and pierce through. Grab the ovaries at the posterior end, then pull them out of the abdomen and place into the fresh media on the other side of the depression slide. (Figure 1A inset). Avoid pulling apart the gut. Discard the carcass.</li>
	<li>Repeat with the other female flies until all ovaries are dissected. Discard the males.</li>
	<li>With one pair of forceps, hold an ovary at the posterior end (near the largest egg chambers), and with the other hand use a pair of forceps to pinch one of the most anterior egg chambers (germarium). (Figure 1A).</li>
	<li>Slowly and steadily, pull an ovariole chain out of the ovary sheath. Continue to dissect out ovarioles individually until all desired egg chambers are removed.</li>
	<li>Repeat steps 1.7-1.8 for all dissected ovaries.</li>
	<li>Once complete, transfer ovarioles to a 0.6ml tube using a plastic transfer pipette.</li>
	<li>Let ovarioles settle to the bottom of tube, then proceed to fixing and staining steps.</li>
</ol>
2. Immunofluorescent (IF) Staining of Ovarioles
<ol>
	<li>Carefully remove dissection media from ovarioles with a pipette. Be sure not to remove any ovarioles or egg chambers. Leave approximately 50 &#956;l&#160;of ovarioles and dissection media.</li>
	<li>Add 50 &#956;l of 16% paraformaldehyde to 150 &#956;l of 0.1 M KPO4 Buffer in a tube, and add solution to egg chambers to fix them. Incubate while rocking for 10 min. CAUTION: paraformaldehyde is toxic.</li>
	<li>Remove fixative and rinse twice with 0.5 ml NP40 wash buffer.</li>
	<li>Wash two times for 15 min each at RT.</li>
	<li>Refer to standard IF protocol15 for subsequent steps.
	<ol>
		<li>Briefly, after fixation, add primary antibodies at the appropriate dilutions and incubate O/N at 4 &#176;C. Wash in NP40 several times, then add secondary antibodies (1:200 dilutions).</li>
		<li>Wash several times in NP40, then add DAPI (1:1,000) for 10 min, then repeat washes. Once IF protocol is complete, add 200&#160;&#956;l&#160;of 50% glycerol in PBS to egg chambers and let sit at RT for 2 hr.</li>
		<li>Remove solution, replace it with 70% glycerol in PBS, and cover with foil. Place sample at 4 &#7506;C until ready for mounting. Meanwhile, continue with step 3.</li>
	</ol>
	</li>
</ol>
3. Advance Preparation of Glycerin Jelly Slides
<ol>
	<li>Measure at least 4 ml&#160;of glycerin jelly using a spatula and fill a glass cell culture tube to the half way mark. Melt glycerin jelly in a water bath at 55 &#176;C for 30 min.</li>
	<li>Pour a small drop of glycerol, approximately 300 &#956;l, from the stock solution onto two microscope slides. Using a tissue, spread glycerol in a thin layer across each of the slides. This provides a base and allows for easy removal of glycerin jelly at step 5.6.</li>
	<li>Cut the tip off of a filtered 1,000 &#956;l pipette tip. Use cut pipette tip to transfer 1,000-1,500 &#956;l of warm glycerin jelly slowly to each microscope slide. Take care to prevent bubbles.</li>
	<li>Let glycerin jelly slides sit for 5 min at RT&#160;to set.</li>
	<li>Place each glycerin jelly slide in 60&#160;mm &#215; 15&#160;mm petri dish and cover with plastic wrap. Place at 4 &#176;C O/N. Optionally, store glycerin jelly slides for up to 5 days at 4 &#176;C.</li>
</ol>
4. Mounting Egg Chambers
<ol>
	<li>Using samples from step 2.5, pipette several 3 &#956;l drops of egg chambers in 70% glycerol across one glycerin jelly slide. Continue pipetting 3 &#956;l drops until all egg chambers are on this slide. Make sure each drop contains at least ten egg chambers. Meanwhile, heat a culture tube of glycerin jelly in a 55 &#176;C water bath.</li>
	<li>Place the glycerin jelly slide with egg chambers under a dissection microscope. Adjust magnification so that only one drop of egg chambers is in the field of view (Figure 1B).</li>
	<li>Using a 30 gauge needle as a spoon, pick up the desired stage egg chamber. When necessary, separate desired egg chambers from an ovariole chain using the needle as a knife.</li>
	<li>To avoid debris that may interfere with imaging, transfer the egg chamber to the second glycerin jelly slide, with the anterior facing left (Figure 1E-1). Repeat until there are at least seven egg chambers lined up in a column (Figure 1C).</li>
	<li>Form new columns of seven until all desired egg chambers are transferred to the second glycerin jelly slide.</li>
	<li>Tear off a small piece of tissue and twist. Use this to absorb the excess PBS-Glycerol from the egg chambers by lightly touching each one. Take care to not remove egg chambers.</li>
	<li>Cut off the tip of a filtered 200 &#956;l pipette tip. Use this to transfer 150 &#956;l of glycerin jelly to cover all the columns of egg chambers. 
	NOTE: The amount of glycerin jelly needed to cover the columns is based on egg chamber stages and number of columns. Amount may be adjusted.</li>
	<li>Let mounted egg chambers sit for 5 min at RT until the top layer of glycerin jelly is completely solidified (Figure 1D).</li>
	<li>Place slide of mounted egg chambers in a 60&#160;mm &#215; 15&#160;mm petri dish and cover with plastic wrap. Store at 4 &#176;C O/N to allow the glycerin jelly layers to solidify together (place in the dark if there is concern about photobleaching).</li>
</ol>
5. Preparation of Egg Chambers for Imaging
<ol>
	<li>Place slide of mounted egg chambers under a dissection microscope. Adjust magnification so that only one column of egg chambers is in the field of view.</li>
	<li>Using a 45&#176; angle miniature scalpel, cut a straight line along the right side of the first column of egg chambers (close to the posterior side of the egg chambers). (Figure 1D-E)</li>
	<li>Next, cut above the first egg chamber at the top and below the last egg chamber in the column. At this point the column of egg chambers should be cut on three sides.</li>
	<li>Using a microknife, slice along the left side of the column, as close as possible to the anterior side of the egg chambers (Figure 1E-3).</li>
	<li>Pipette 100 &#956;l of cold 1X PBT over the cut column.</li>
	<li>Use a round edged spatula to remove the excess glycerin jelly around three sides of the cut column of egg chambers and discard, leaving the rest on the slide.</li>
	<li>Insert the spatula in the cut made at the anterior side of egg chambers and separate the column from the primary glycerin jelly block.</li>
	<li>Prepare samples for either inverted (5.8.1) or upright (5.8.2) microscopy.
	<ol>
		<li>For Inverted Microscope: Transfer the column of egg chambers to a coverslip with anterior side of egg chambers facing down. Repeat steps 5.2-5.8 until all columns of glycerin jelly have been removed and mounted. Add a couple of drops of 50% PBS-Glycerol onto each block of egg chambers to prevent them from drying out. Image egg chambers directly on coverslip.</li>
		<li>For Upright Microscope: Transfer the column of egg chambers to a microscope slide with the anterior side facing up. Repeat steps 5.2-5.9 until all columns of glycerin jelly have been removed and mounted on microscope slides. Add a couple of drops of 50% PBS-Glycerol onto each block of egg chambers and cover blocks with a #1 &#189; coverslip.</li>
	</ol>
	</li>
</ol>

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L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expanding+the+morphogenetic+repertoire:+perspectives+from+the+Drosophila+egg.">Expanding the morphogenetic repertoire: perspectives from the Drosophila egg.</a> Dev Cell. 22 (1), 12-23 (2012).</li><li>Montell, D. J., Yoon, W. H., Starz-Gaiano, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Group+choreography:+mechanisms+orchestrating+the+collective+movement+of+border+cells.">Group choreography: mechanisms orchestrating the collective movement of border cells.</a> Nat Rev Mol Cell Biol. 13 (10), 631-645 (2012).</li><li>Spradling, A. 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The authors have no competing financial interests.

Here we describe a method to mount and image small, developing egg chambers from a end-on perspective. Common techniques for imaging egg chambers are optimized for lateral views and primarily allow precise visualization of medio-lateral follicle cells when stained with fluorescent antibodies. The use of Z-stacks or 3-D reconstructions aids in viewing multiple focal planes, but is still inadequate for sub-cellular resolution of the poles of elliptical egg chambers (Figure 2D). While this can be overcome p...

Study of Drosophila melanogaster has provided great insights into the genetic regulation of a wide range of phenomena. In particular, there has been extensive research on egg development, because oogenesis provides a tractable way to investigate many different developmental processes, including tissue patterning, cell polarity changes, cell cycle switching, and translational regulation1,2,3,4. One important morphogenic event during oogenesis is the specification, acquisition of motility, and migration of a set of cells called border cells (reviewed in 5). Since cell migration is a key feature of animal morphogenesis, and because the genetic regulation of this process is well-conserved, mechanisms determined in flies are likely to be important in other contexts. Thus, we are investigating the molecular control of border cell migration. For our studies, we have developed a new method to observe the anterior poles of developing eggs, where border cells arise, to examine how they develop in detail.
Within the ovary, egg chambers at various developmental stages exist along chains called ovarioles, which are encased in a thin sheath (Figure 1A). Each egg chamber will go on to form one egg. During oogenesis, several different cell types must develop in a coordinated manner. The D. melanogaster egg chamber consists of 16 germ-line cells, including one oocyte, surrounded by a single-layer follicular epithelium6. A small number of specialized cells, called polar cells, arise at the anterior and posterior poles of the epithelium. The 6-8 border cells originate in the anterior epithelium of the egg chamber, induced by the polar cells5,7. In mid-oogenesis (stage 9), the border cells detach from their neighbors and migrate between the nurse cells to reach the oocyte at the posterior of the egg chamber5,7. This movement must be accomplished while the border cells remain in a cluster surrounding two non-motile polar cells, making this a type of collective cell migration. Successful migration of the border cell cluster ensures proper development of the micropyle of the egg shell, which is necessary for fertilization.
The anterior polar cells instruct border cell fate by activating a signal transduction cascade. Polar cells secrete a cytokine, Unpaired (UPD), which binds to a transmembrane receptor, Domeless (DOME), on neighboring follicle cells during stage 8 of oocyte development8,9. The binding of UPD causes Janus tyrosine kinase (JAK) to phosphorylate the Signal Transducer and Activator of Transcription (STAT)8,10,11. STAT then moves to the nucleus to activate transcription. Slow Border Cells (SLBO) is a transcription factor that is a direct transcriptional target of STAT and is also required for border cell migration12. Lateral views of egg chambers indicate that STAT activity is regulated in a gradient across the anterior epithelium8,11,13. Follicle cells closest to the polar cells have the highest levels of activated STAT, thus they become border cells and invade the adjacent germ-line tissue.
To understand how the border cells are specified within and detach from the epithelium, we need to observe how the tissue is organized. If we view egg chambers from an anterior-on perspective, we would expect radial symmetry of STAT activity in the follicle cells surrounding the polar cells. An end-on view would also more accurately show differences of membrane proteins and cell-cell interfaces prior to and during detachment than comparing cells in different focal planes. Because egg chambers are oblong and attached to each other by stalk cells, they settle onto slides laterally, making it difficult to observe the anterior architecture. Thus, much information about the cells at the poles of the egg chamber has been inferred from lateral views. Although some information can be obtained through algorithmic 3-D reconstructions of optical sections, light scattering, photobleaching, and poorer limits of resolution in the Z-axis make this information less detailed and reliable in the absence of expensive techniques like super-resolution microscopy14. Other kinds of section-based imaging (for example, electron microscopy or microtome sectioning) require extensive manipulation of tissues, including dehydration, increasing the likelihood for artifacts. Thus, we developed a new method to image D. melanogaster egg chambers while upright. This method has already proven useful in elucidating how motile cells are fated (see Representative results and Manning et al, under review), and is likely to be more broadly valuable in studies of other aspects of oogenesis.

<table border="0" cellpadding="0" cellspacing="0" width="1027">
	<tbody>
		<tr height="40">
			<td height="40" style="height:40px;width:348px;">Name of Reagent/ Equipment</td>
			<td style="width:279px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:283px;">Comments/Description</td>
		</tr>
		<tr height="96">
			<td height="96" style="height:96px;width:348px;">0.1 M Potassium phosphate Buffer (KPO4 Buffer)</td>
			<td style="width:279px;"></td>
			<td style="width:119px;"></td>
			<td style="width:283px;">Add 3.1 g of NaH2PO4&#8226;H2O and 10.9 g of Na2HPO4 (anhydrous) to distilled H2O to make a volume of 1 L. The pH of the final solution will be 7.4. This buffer can be stored for up to 1 mo at 4&#176;C.</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:348px;">16% Paraformaldehyde aqueous solution, EM grade</td>
			<td style="width:279px;">Electron Microscopy Sciences</td>
			<td style="width:119px;">15710</td>
			<td>methanol-free to preserve GFP fluorescence</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">30G x 1/2 inch needle&#160;</td>
			<td style="width:279px;">VWR</td>
			<td style="width:119px;">BD305106</td>
			<td>Regular bevel</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:348px;">Active Dry Yeast</td>
			<td style="width:279px;">Genesee Scientific</td>
			<td>62-103</td>
			<td>To fatten female flies</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">Bovine Serum Albumin</td>
			<td style="width:279px;">PAA-cell culture company</td>
			<td style="width:119px;">A15-701</td>
			<td>Used in NP40 Wash Buffer</td>
		</tr>
		<tr height="39">
			<td height="39" style="height:39px;width:348px;">Dumont #5 Forceps</td>
			<td style="width:279px;">Fine Science Tools</td>
			<td style="width:119px;">11295-10</td>
			<td style="width:283px;">Dumostar alloy, biologie tip; sharp tips are essential for ovariole dissection</td>
		</tr>
		<tr height="39">
			<td height="39" style="height:39px;width:348px;">DAPI (4&#8242;,6-Diamidino-2-phenylindole dihydrochloride)</td>
			<td style="width:279px;">Sigma Aldrich</td>
			<td style="width:119px;">D9542</td>
			<td style="width:283px;">5mg/ml stock solution&#160;&#160;</td>
		</tr>
		<tr height="39">
			<td height="39" style="height:39px;width:348px;">Fetal Bovine Serum (FBS)</td>
			<td style="width:279px;">Life Technologies</td>
			<td style="width:119px;">16140-071</td>
			<td style="width:283px;">Added to supplement dissection medium (10%)&#160;</td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:348px;">Glass culture tube</td>
			<td style="width:279px;">VWR</td>
			<td>47729-576</td>
			<td>14mL</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">Glass Depression Slides</td>
			<td style="width:279px;">VWR</td>
			<td>470019-020</td>
			<td>1.2 mm Thick, Double Cavity</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">Glycerin Jelly&#160;</td>
			<td style="width:279px;">Electron Microsocpy Sciences</td>
			<td>17998-10</td>
			<td>Mounting media</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">Glycerol</td>
			<td style="width:279px;">IBI Scientific</td>
			<td style="width:119px;">IB15760</td>
			<td>70% in PBS</td>
		</tr>
		<tr height="39">
			<td height="39" style="height:39px;width:348px;">IGEPAL CA-630</td>
			<td style="width:279px;">Sigma Aldrich</td>
			<td style="width:119px;">I3021-500ML</td>
			<td style="width:283px;">(interchangable for Nonidet P-40)&#160; Used in NP40 Wash Buffer&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">Leica Fluorescent Stereoscope&#160;</td>
			<td style="width:279px;">Leica Microsystems</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">Leica SP5 Confocal Microscope</td>
			<td style="width:279px;">Leica Microsystems</td>
			<td style="width:119px;"></td>
			<td>40x/0.55NA dry objective&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">Micro spatula&#160;</td>
			<td style="width:279px;">VWR</td>
			<td style="width:119px;">82027-518</td>
			<td>Stainless steel</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">Microknife&#160;</td>
			<td style="width:279px;">Roboz Surgical Instrument Company</td>
			<td style="width:119px;">37-7546</td>
			<td>45&#7506; angle</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">Microscope Slide</td>
			<td style="width:279px;">VWR</td>
			<td style="width:119px;">16004-368</td>
			<td>75x25x1 mm</td>
		</tr>
		<tr height="58">
			<td height="58" style="height:58px;width:348px;">NP40 Wash Buffer</td>
			<td style="width:279px;"></td>
			<td style="width:119px;"></td>
			<td style="width:283px;">50mM TRIS-HCL, 150mM NaCl, 0.5% Ipegal, 1mg/ml BSA, and 0.02% sodium azide</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">Penicillin-Streptomycin-Glutamine</td>
			<td style="width:279px;">Life Technologies</td>
			<td>10378-016</td>
			<td>Added to supplement dissection medium (0.6X)</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">Petridish- Polysterine, sterile</td>
			<td style="width:279px;">VWR</td>
			<td>82050-548</td>
			<td>60Wx15H mm</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">Phosphate Buffer Saline</td>
			<td style="width:279px;">Sigma Aldrich</td>
			<td style="width:119px;">P3813-10PAK</td>
			<td>10 packs of Powder</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">Potassium phosphate dibasic</td>
			<td style="width:279px;">Sigma Aldrich</td>
			<td style="width:119px;">P3786-500G</td>
			<td>Used in 0.1M KPO4 Buffer&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">Potassium phosphate monobasic</td>
			<td style="width:279px;">Sigma Aldrich</td>
			<td style="width:119px;">P9791-500G</td>
			<td>Used in 0.1M KPO4 Buffer&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">Schneider&#8217;s Insect Medium</td>
			<td style="width:279px;">Life Technologies</td>
			<td style="width:119px;"> 
			11720018</td>
			<td>With L-glutamine and sodium bicarbonate</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:348px;">Sodium azide</td>
			<td style="width:279px;">Sigma Aldrich</td>
			<td style="width:119px;">S2002-25G</td>
			<td>Used in fluorescent antibody staining</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">Sodium chloride</td>
			<td style="width:279px;">Sigma Aldrich</td>
			<td style="width:119px;">S3014-500G</td>
			<td>Used in NP40 Wash Buffer</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">TRIS-HCL</td>
			<td style="width:279px;">IBI Scientific</td>
			<td style="width:119px;">IB70144</td>
			<td>1M TRIS-HCL, pH 7.4</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:348px;">Volocity 3D Image Analysis Software</td>
			<td style="width:279px;">PerkinElmer</td>
			<td style="width:119px;"></td>
			<td>For processing confocal Z-stacks</td>
		</tr>
	</tbody>
</table>

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.

The upright imaging method allowed us to see directly the organization of cells in the anterior follicular epithelium at stage 8. A general marker for follicle cell fate, the Eyes Absent (EYA) protein, as well as the nuclear DNA marker DAPI, showed even expression across this field of cells, and demonstrated that all cells could be seen with similar staining intensities (Figure 2B&#8221;). Proteins regulated in response to the cytokine UPD, however, showed variable patterns and expression levels. Polar c...

Watch this Scientific Journal Video about Upright Imaging of Drosophila Egg Chambers at JoVE.com

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.

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 ...

upright-imaging-of-drosophila-egg-chambers

Research

JoVE Journal

Developmental Biology

7.5K Views.  University of Maryland Baltimore County. 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.

Video: Upright Imaging of Drosophila Egg Chambers

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 ...

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 ...

Analysis of Actomyosin Dynamics at Local Cellular and Tissue Scales Using Time-lapse Movies of Cultured Drosophila Egg Chambers

Drosophila immature eggs are called egg chambers, and their structure resembles primitive organs that undergo morphological changes from a round to an ellipsoid shape during development. This developmental process is called oogenesis and is crucial to generating functional mature eggs to secure the next fly generation. For these reasons, egg chambers have served as an ideal and relevant model to understand animal organ development.
Several in vitro culturing protocols have been developed, but there are several disadvantages to these protocols. One involves the application of various covers that exert an artificial pressure on the imaged egg chambers in order to immobilize them and to increase the imaged acquisition plane of the circumferential surface of the analyzed egg chambers. Such an approach may negatively influence the behavior of the thin actomyosin machinery that generates the power to rotate egg chambers around their longer axis.
Thus, to overcome this limitation, we culture Drosophila egg chambers freely in the media in order to reliably analyze actomyosin machinery along the circumference of egg chambers. In the first part of the protocol, we provide a manual detailing how to analyze the actomyosin machinery in a limited acquisition plane at the local cellular scale (up to 15 cells). In the second part of the protocol, we provide users with a new Fiji-based plugin that allows the simple extraction of a defined thin layer of the egg chambers&#8217; circumferential surface. The following protocol then describes how to analyze actomyosin signals at the tissue scale (&#62;50 cells). Finally, we pinpoint the limitations of these approaches at both the local cellular and tissue scales and discuss its potential future development and possible applications.

Analysis of Actomyosin Dynamics at Local Cellular and Tissue Scales Using Time-lapse Movies of Cultured Drosophila Egg Chambers

This protocol provides a Fiji-based, user-friendly methodology along with straightforward instructions explaining how to reliably analyze actomyosin behavior in individual cells and curved epithelial tissues. No programming skills are required to follow the tutorial; all steps are performed in a semi-interactive manner using the graphical user interface of Fiji and associated plugins.

Drosophila immature eggs are called egg chambers, and their structure resembles primitive organs that undergo morphological changes from a round to an ...

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 ...

Human Egg Maturity Assessment and Its Clinical Application

The optimal timing of intracytoplasmic sperm injection (ICSI) is of a serious concern for fertility programs because untimely sperm entry diminishes the egg&#39;s developmental competence. Presence of the first polar body (PB) together with the meiotic spindle indicates completion of the oocyte maturation and the egg&#39;s readiness for fertilization. In clinical practice, it is customary to assume that all oocytes displaying a PB are mature metaphase (MII) oocytes. However, PB extrusion precedes the formation of the bipolar MII spindle. This asynchrony makes the mere presence of PB an unreliable marker of oocyte maturity. Noninvasive spindle imaging using polarized light microscopy (PLM) allows quick and easy inspection of whether the PB-displaying oocyte actually reassembled a meiotic spindle prior to ICSI. Here, we present a standard protocol to perform human egg maturity assessment in the clinical laboratory. We also show how to optimize the time of ICSI with respect to the oocyte&#39;s developmental stage in order to prevent premature sperm injection of late-maturing oocytes. Using this approach, even immature oocytes extruding PB in vitro can be clinically utilized. Affirmation that MII spindle is present prior to sperm injection and individual adjustment of the time of ICSI is particularly important in poor prognosis in-vitro fertilization (IVF) cycles with a low number of oocytes available for fertilization.

We provide an outline of the clinical protocol for non-invasive assessment of human egg maturity using polarized light microscopy.

The optimal timing of intracytoplasmic sperm injection (ICSI) is of a serious concern for fertility programs because untimely sperm entry diminishes the ...

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.

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.

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

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.