Name: protocols for visualizing steroidogenic organs and their interactive organs with immunostaining in the fruit fly drosophila melanogaster
Uploaded: 2017-04-14T14:00:00
Description: Watch this Scientific Journal Video about Protocols for Visualizing Steroidogenic Organs and Their Interactive Organs with Immunostaining in the Fruit Fly Drosophila melanogaster at JoVE.com

We thank Reiko Kise and Tomotsune Ameku for their technical support for this work. We are also grateful to Kei Ito, Olga Alekseyenko, Akiko Koto, Masayuki Miura, the Bloomington Drosophila Stock Center, KYOTO Stock Center (DGRC), and the Developmental Studies Hybridoma Bank for stocks and reagents. This work was supported by grants to Y.S.N. from JSPS KAKENHI Grant Number 16K20945, The Naito Foundation, and Inoue Science Research Award; and by a grant to R.N. from MEXT KAKENHI Grant Number 16H04792.

NOTE: The overall scheme of protocols is shown in Figure 1.
1. The Dissection of the Larval Ring Gland (RG)
NOTE: In D. melanogaster, which belongs to cyclorrhaphous Diptera, the PG is within a composite endocrine organ called the ring gland (RG, Figure 2D).&#160;Since it is unfeasible that the PG is surgically separated from other types of cells (discussed later), a practical target is to i...

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We studied ecdysteroid biosynthesis and its regulatory mechanism in D. melanogaster, and devised a protocol for dissection and immunostaining. The timing of ecdysteroid biosynthesis is affected by environmental cues through neuronal inputs33, so it is essential to maintain the innervation of the ecdysteroidogenic organs along with the brain, VNC, and other tissues during dissection.
As described above, the&#160;D. melanogaster PG forms a complex endocr...

In multicellular organisms, a group of cells is endowed with a specialized function in their biogenic activity that is essential for the whole body. To fulfill their missions, each tissue or organ expresses a series of genes related to their functions and communicates with other tissues to orchestrate their activities in the context of development. To characterize such specialized cellular functions and inter-organ interactions, we need to specify a group of cells along with other types of cells being kept intact in the multicellular architecture.
One example of such specialized organs is a steroidogenic organ, where many biosynthetic enzymes mediate the conversion steps from cholesterol to active steroid hormones1. Most of these enzyme genes are specifically expressed in steroidogenic organs, and the biosynthesis pathway is tightly regulated by many external stimuli via humoral inputs and neuronal inputs. Once synthesized, steroid hormones are secreted into the hemolymph and are targeted to many tissues and organs for regulating the expression of a variety of genes2. Therefore, the action of a steroid hormone induces a systemic response to maintain homeostasis, growth, and reproduction.
To investigate the functions of steroid hormone biosynthesis and the pleiotropic actions of steroid hormones, Drosophila melanogaster can be utilized as a suitable model system. During the larval stages, the insect steroid hormone, ecdysteroid, is biosynthesized in a specialized endocrine organ called the prothoracic gland (PG)3. In the PG, several ecdysteroidogenic enzymes specifically catalyze the multiple conversion steps from cholesterol to ecdysone, which controls molting and metamorphosis at the appropriate developmental stages4. Therefore, a dynamic change in&#160;ecdysteroid titer is regulated by many signaling pathways in response to environmental cues. On the other hand, in the adult stage, ecdysteroid plays essential roles in physiology, including reproduction, sleep, memory, and lifespan5,6,7,8. It is known that ecdysteroid is actively biosynthesized in the ovary, regulating the progression of oogenesis6,7,8,9,10,11. Recently we have reported that the number of germline stem cells (GSCs) is affected by ecdysteroid and sex peptide signaling in response to mating stimuli12.
Powerful tools of D. melanogaster genetics and cell biology, including well-annotated genome information, binary gene expression systems, and transgenic RNAi techniques, have enabled us to identify genes essential to ecdysteroid biosynthesis in the PG and the ovary13,14,15. Once the ecdysteroidogenic genes are identified, the transcriptional regulation of these genes and the dynamic localizations of gene products can be examined in the biosynthesis pathway16. For this purpose, quantitative-reverse transcription-PCR, RNA in situ hybridization, and immunohistological analysis are conducted. The application of these techniques includes a challenging task; the&#160;elaborate dissection of the PG or the ovary. In particular, the PG of the fruit fly is relatively smaller than that of other insects (e.g. the silkworm and the blow fly), so one needs to practice the vital skill of fruit fly dissection for sampling. Furthermore, both ecdysteroidogenic organs receive innervations from the central nervous system (CNS)17,18,19,20. Thus, for accurate anatomical analyses, the ecdysteroidogenic organs should be kept intact along with the CNS and other organs, not to disrupt their neuronal connections.
Here we provide protocols for the dissection and visualization of steroidogenic organs in D. melanogaster. Learning the dissection technique is the key starting point for these&#160;experiments. In addition, one can successfully label the steroidogenic organs as well as their interactive organs with several antibodies and GAL4 driver lines. Taking advantage of these techniques, materials, and genetics, one can study the comprehensive mechanisms of steroid hormone biosynthesis.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>egg collection</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>tissue culture dish (55 mm)</td>
			<td>AS ONE</td>
			<td>1-8549-02</td>
			<td>&#160;for grape-juice agar plates</td>
		</tr>
		<tr>
			<td>collection cup</td>
			<td>HIKARI KAGAKU</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>yeast paste</td>
			<td>Oriental dry yeast, Tokyo</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>100% grape juice</td>
			<td>Welch Food Inc.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>rearing larvae</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>small vials (12ml, 40&#215;23.5 mm, PS)</td>
			<td>SARSTEDT</td>
			<td>58.487</td>
			<td></td>
		</tr>
		<tr>
			<td>disposable loop</td>
			<td>AS ONE</td>
			<td>6-488-01</td>
			<td></td>
		</tr>
		<tr>
			<td>standard fly food</td>
			<td></td>
			<td></td>
			<td>&#160;the recepi us on the website of Blooington stock center.</td>
		</tr>
		<tr>
			<td>dissection</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>dissecting microscope</td>
			<td>Carl Zeiss</td>
			<td>Stemi 2000-C</td>
			<td></td>
		</tr>
		<tr>
			<td>dissecting microscope</td>
			<td>Leica</td>
			<td>S8 AP0</td>
			<td></td>
		</tr>
		<tr>
			<td>tissue culture dish (35 x 10 mm, non-treated)</td>
			<td>IWAKI</td>
			<td>1000-035</td>
			<td></td>
		</tr>
		<tr>
			<td>Sylgard</td>
			<td>TORAY</td>
			<td></td>
			<td>coarting silicon inside dishes</td>
		</tr>
		<tr>
			<td>Terumo needle (27G, 0.40 x 19 mm)&#160;</td>
			<td>TERUMO</td>
			<td>NN-2719S</td>
			<td>A &#34;knife&#34; to cut the tissue</td>
		</tr>
		<tr>
			<td>Terumo syringe,&#12288;1ml</td>
			<td>TERUMO</td>
			<td>SS-01T</td>
			<td></td>
		</tr>
		<tr>
			<td>forceps, Inox, #5</td>
			<td>Dumont, Switzerland</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>insect pin (0.18 mm in diameter)</td>
			<td>Shiga Brand</td>
			<td></td>
			<td>for fillet dissection</td>
		</tr>
		<tr>
			<td>micro scissors</td>
			<td>NATSUME SEISAKUSHO CO LTD.&#160;</td>
			<td>MB-50-10</td>
			<td></td>
		</tr>
		<tr>
			<td>fixation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ultrapure water</td>
			<td>Merck Millipore</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>phosphate buffered saline (PBS)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Formaldehyde</td>
			<td>Nacalai tesque</td>
			<td>16222-65</td>
			<td></td>
		</tr>
		<tr>
			<td>Paraformaldehyde</td>
			<td>Nacalai tesque</td>
			<td>02890-45</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton-X100</td>
			<td>Nacalai tesque</td>
			<td>35501-15</td>
			<td></td>
		</tr>
		<tr>
			<td>microtubes (1.5 ml)</td>
			<td>INA OPTIKA</td>
			<td>CF-0150</td>
			<td></td>
		</tr>
		<tr>
			<td>Incubation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>As one swist mixer TM-300 (rocker)</td>
			<td>As one</td>
			<td>TM-300</td>
			<td>rocker</td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin</td>
			<td>SIGMA</td>
			<td>9048-46-8</td>
			<td></td>
		</tr>
		<tr>
			<td>primary antibody</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>anti-Sro (guinea pig), 1:1000</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>anti-GFP (rabbit), 1:1000</td>
			<td>Molecular Probes</td>
			<td>A6455</td>
			<td>Shimada-Niwa ans Niwa, 2014</td>
		</tr>
		<tr>
			<td>anti-GFP (mouse mAb, GF200), 1:100</td>
			<td>Nakarai tesque</td>
			<td>04363-66</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-5HT (rabbit), 1:500</td>
			<td>SIGMA</td>
			<td>S5545</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-Hts 1B1 (mouse)</td>
			<td>Developmental Studies Hybridoma Bank (DSHB)</td>
			<td>1B1</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-DE-cadherin (rat), 1:20</td>
			<td>DSHB</td>
			<td>DCAD2</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-nc82 (mouse), 1:50</td>
			<td>DSHB</td>
			<td>nc82</td>
			<td></td>
		</tr>
		<tr>
			<td>secondary antibody</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-Rabbit IgG (H+L) Secondary Antibody, Alexa Fluor 488 conjugate</td>
			<td>Life Technologies</td>
			<td>A-11008</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-Mouse IgG (H+L) Secondary Antibody, Alexa Fluor 488 conjugate</td>
			<td>Life Technologies</td>
			<td>A-11001</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-Rat IgG (H+L) Secondary Antibody, Alexa Fluor 546 conjugate</td>
			<td>Life Technologies</td>
			<td>A-11081</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-Guinea Pig IgG (H+L) Secondary Antibody, Alexa Fluor 555 conjugate</td>
			<td>Life Technologies</td>
			<td>A-21435</td>
			<td></td>
		</tr>
		<tr>
			<td>Alexa Fluor 546 dye-conjugated phalloidin</td>
			<td>Life Technologies</td>
			<td>A-22283</td>
			<td></td>
		</tr>
		<tr>
			<td>Mounting reagents</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Micro slide glass</td>
			<td>Matsunami Glass Ind.,Ltd.</td>
			<td>SS7213</td>
			<td></td>
		</tr>
		<tr>
			<td>Square microscope cover glass</td>
			<td>Matsunami Glass Ind.,Ltd.</td>
			<td>C218181</td>
			<td></td>
		</tr>
		<tr>
			<td>FluorSave reagent (Mounting reagent)</td>
			<td>Calbiochem</td>
			<td>345789</td>
			<td></td>
		</tr>
		<tr>
			<td>Transfer pipette 1 ml (Disposable dropper)</td>
			<td>WATSON</td>
			<td>5660-222-1S</td>
			<td></td>
		</tr>
		<tr>
			<td>imaging</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>LSM700 laser scanning microscope system</td>
			<td>Carl Zeiss</td>
			<td></td>
			<td>inverted Axio Observer. Z1 SP left</td>
		</tr>
		<tr>
			<td>image processing</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>LSM700 ZEN</td>
			<td>Carl Zeiss</td>
			<td></td>
			<td>It is a special user interface based on the 64 bit Microsoft Windows7 operating system</td>
		</tr>
		<tr>
			<td>ImageJ</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Fly stocks</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>w; GMR45C06-GAL4</td>
			<td></td>
			<td></td>
			<td>&#160;from Bloomington Drosophila Stock Center. (#46260)</td>
		</tr>
		<tr>
			<td>UAS&#8211;GFP; UAS&#8211;mCD8::GFP</td>
			<td></td>
			<td></td>
			<td>gifts from K. Ito, The University of Tokyo.</td>
		</tr>
		<tr>
			<td>w[1118]</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>w; phantom-GAL4#22/UAS-turboRFP</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>w; UAS-mCD8::GFP; TRH-GAL4</td>
			<td></td>
			<td></td>
			<td>see in Ref29, Alekseyenko, O. V, Lee, C. &#38; Kravitz, E. A.(2010)</td>
		</tr>
		<tr>
			<td>w; UAS-mCD8::GFP</td>
			<td></td>
			<td></td>
			<td>&#160;from Bloomington Drosophila Stock Center. (#32188)</td>
		</tr>
		<tr>
			<td>yw;; nSyb-GAL4</td>
			<td></td>
			<td></td>
			<td>&#160;from Bloomington Drosophila Stock Center. (#51941)</td>
		</tr>
	</tbody>
</table>

protocols for visualizing steroidogenic organs and their interactive organs with immunostaining in the fruit fly drosophila melanogaster

In multicellular organisms, a small group of cells is endowed with a specialized function in their biogenic activity, inducing a systemic response to&#160;growth and reproduction. In insects, the larval prothoracic gland (PG) and the adult female ovary play essential roles in biosynthesizing the principal steroid hormones called ecdysteroids. These ecdysteroidogenic organs are innervated from the nervous system, through&#160;which the timing of biosynthesis is affected by environmental cues. Here we describe a protocol for visualizing ecdysteroidogenic organs and their interactive organs in larvae and adults of the fruit fly Drosophila melanogaster, which provides a suitable model system for studying steroid hormone biosynthesis and its regulatory mechanism. Skillful dissection allows us to maintain the positions of ecdysteroidogenic organs and their interactive organs including the brain, the ventral nerve cord, and other tissues. Immunostaining with antibodies against ecdysteroidogenic enzymes, along with transgenic fluorescence proteins driven by tissue-specific promoters, are available to label ecdysteroidogenic cells. Moreover, the innervations of the ecdysteroidogenic organs can also be labeled by specific antibodies or a collection of GAL4 drivers in various types of neurons. Therefore, the ecdysteroidogenic organs and their neuronal connections can be&#160;visualized simultaneously&#160;by immunostaining and transgenic techniques. Finally, we describe how to visualize germline stem cells, whose proliferation and maintenance are controlled by ecdysteroids. This method contributes to comprehensive understanding of steroid hormone biosynthesis and its neuronal regulatory mechanism.

We used the above protocols to visualize steroidogenic organs and their interactive organs in D. melanogaster larvae and adult females. The overall scheme of protocols is shown in Figure 1.
The RG, including the PG (Figure 2D), is smaller and more transparent than the brain and is located at the anterior-dorsal side of the brain (Figure 2A-C and 3A-E). To label the PG cells, several groups have generated various types of antibodies against ecdysteroidogenic e...

Watch this Scientific Journal Video about Protocols for Visualizing Steroidogenic Organs and Their Interactive Organs with Immunostaining in the Fruit Fly Drosophila melanogaster at JoVE.com

Protocols for Visualizing Steroidogenic Organs and Their Interactive Organs with Immunostaining in the Fruit Fly Drosophila melanogaster

We describe a protocol for dissection, fixation, and immunostaining of steroidogenic organs in Drosophila larvae and adult females to study steroid hormone biosynthesis and its regulatory mechanism. In addition to steroidogenic organs, we visualize the innervation of steroidogenic organs as well as steroidogenic target cells such as germline stem cells.

Protocols for Visualizing Steroidogenic Organs and Their Interactive Organs with Immunostaining in the Fruit Fly Drosophila melanogaster

In multicellular organisms, a small group of cells is endowed with a specialized function in their biogenic activity, inducing a systemic response ...

The overall goal of this procedure is to visualize the steroidogenic organs and their interactive organs in larvae or adult females of the fruit fly, Drosophila melanogaster. This method can help understand insect steroid hormone biosynthesis, and the neuronal regulatory mechanism underlying mating and metamorphosis. The main advantage of this technique is that the innervation of steroidogenic organs and the relative portion of their interactive organs remains intact.Generally, individuals new to this method will struggle because the steroidogenic organs in fly larvae are quite tiny and transparent. My lab and I are pleased to share our dissection protocols. So, let's get started.After preparing the larvae, start the course dissection in a three centimeter dish filled with PBS, under a dissecting microscope. First, grip the mouth hook with forceps. Then, using micro scissors, sever the body at about a third of the length from the anterior tip.Next, hold the anterior length with one pair of forceps and use a second pair to gently push the tip of the head into the body, to ultimately turn the larval body inside out. Prepare up to 20 larvae in this manner within 10 minutes, and then transfer them into fixative solution. After 30 minutes, wash the preparations, and proceed with immunostaining.To begin, leave the larvae immersed in water for about one hour, to asphyxiate and thus immobilize the larvae. Then, place a larva dorsal side up in a drop of PBS on a silicone-coated dish. The dorsal side has the two tracheal tubes.Under a dissecting microscope, use forceps to insert an insect pin into the anterior tip. Then, stretch the body to the posterior side and put a second pin into the posterior tip. Next, make a small incision near the tail using micro scissors.From the incision, carefully cut the dorsal cuticle longitudinally along the dorsal midline, toward the head, while not damaging any of the tissues under the cuticle. After making the incision, stretch the body walls apart, and secure them with insect pins at the corners. Then, using forceps, remove the anterior fat body and salivary glands, thus exposing the brain-ring gland complex on the surface.Now, aspirate the PBS, and immerse the preparation in fixative solution. After 30 minutes, use forceps to remove the insect pins and transfer the preparation into a microtube filled with 0.3%PBT. Then, proceed with immunostaining.After immunostaining the larvae, use a disposable pipet to transfer the samples to a dish filled with 0.3%PBT. Under a dissecting microscope, grip the cuticle or mouth hook with one pair of forceps. Then, use a 27 gauge needle attached to a one milliliter syringe, like a knife, to remove the brain-ring gland eye disc complex from the body cuticle, by cutting away the anterior tip of the esophagus and eye discs.Next, using forceps, carefully separate the esophagus and gut from the brain-ring gland eye disc complex. Pull the gut out to the posterior side, since the esophagus passes through the brain above the ventral nerve cord. Finally, to isolate the brain-ring gland complex, carefully cut the connections between the brain disc, eye discs, and leg discs, with a needle knife.It is quite essential to use fine forceps with sharp edges during dissection. I'd strongly recommend that you sharpen forceps with a piece of grinding stone to bring their edges together without any gaps. To transfer the samples, use a micro pipet with a wide bore tip.Deposit the samples onto the center of the glass slide. Then, use forceps to position the samples onto their ventral sides, so the ring gland, which is located on the dorsal side of the brain, can be imaged. Next, tilt the slide and wipe off as much of the excess PBT as possible.Then, put a drop of mounting reagent near the samples and use forceps to slowly lower a cover slip over the reagent, and then over the samples. To dissect the adult female ovary, anesthetize flies with carbon dioxide gas. Then, cut off their heads and transfer their bodies to a three centimeter dish filled with PBS.Next, under a dissecting microscope, grip the dorsal side of the thorax with forceps, and take hold of abdominal segment A-5 or A-6 with a second pair of forceps. Then, peel away the abdominal cuticle towards the posterior side. Before proceeding, clean the sticky cuticle off the forceps.Next, pinch an ovaduct, and isolate the ovary. Then comb out and spread the tips of the ovary using forceps. Once spread, immerse the ovary in fixative solution for 30 minutes, to prepare them for staining.To make a preparation that maintains the innervation of the ovary, transfer anesthetized female flies to a silicone-coated dish filled with PBS. Under the dissection microscope, hold the proboscis, and peel away the head cuticle to expose the brain. From the brain, remove the attached trachea, leaving the brain connected to the ventral nerve cord.Then, hold the thorax by the dorsal side, and remove the legs and wings. Next, peel away the ventral cuticle of the thorax, beginning at the base of each leg. Once the VNC is exposed, very carefully remove the residual dorsal cuticle and muscles attached to the VNC, using forceps.Do not damage the connections between the brain and the VNC. Next, using forceps, peel away the abdominal cuticle to expose the ovaries and their interactive organs, which includes the prop, the gut, the ovaduct, the uterus, and the accessory gland. Finally, remove any residual tissues, including the trachea, and the fat body.Then, immerse the samples in fixative solution for 30 minutes, to prepare them for immunostaining. After immunostaining, transfer the samples to a glass slide with 0.1%PBT using a micro pipet. Then, view the slide with a microscope, and separate the strings of the ovarioles from each other using forceps.Do not injure the tips of the ovarioles during this process. They contain the germaria. When preparing the brain to reproductive organ complex, remove any residual cuticle, and spread the structures out onto the slide.Next, wipe off most of the excess PBT, and then apply a drop of mounting reagent to the sample. Next, slowly place a cover slip onto the slide using forceps and store the slide at four degrees celsius in the dark. Later, observe the samples under the microscope, and bring the steroidogenic organs into the field of view.Once the view is fixed, switch the imaging system to the image acquisition mode. During the larval stages, the prothoracic gland was labeled with antibodies against ecdysteroidogenic enzymes, including the anti-shroud antibody. To visualize the neuronal connection between the prothoracic gland and the brain, the brain-ring gland complex was dissected.The filet dissection method shows the stomatogastric nervous system, in which a group of serotonergic neurons project to the prothoracic gland, the proventriculus, and the pharyngeal muscles. In adult females, ovarian ecdysteroid affects many aspects of ovogenesis, such as GSC proliferation. The GSCs are located in the germarium at the tip of each ovariole in the ovary.Within the germarium, the GSCs were specifically labeled using two antibodies, 1B1, and DE-cadherin. To visualize the innervation of the ovary, the ovary was dissected, along with the brain, VNC, gut, prop, uterus, and spermatheca. Neurons were visualized by mCD8:GFP under the control of the n-Synaptobrevin GAL4 driver.Additionally, muscles'structure were stained using diconjugated phalloidin. Although dissection of the steroidogenic organs can at first feel difficult, use this movie to learn the cutting point of the tissues to more easily isolate the organ without injury. We hope that our protocol is informative, not only for beginners, but also experienced researchers.Once mastered, you can apply this procedure to your research, and brush up to fit with your needs. We hope this protocol will help the comprehensive understanding of steroid hormone biosynthesis. More detailed step-by-step protocols are available in the manuscript.Please check it out.

protocols-for-visualizing-steroidogenic-organs-their-interactive

Research

JoVE Journal

Developmental Biology

Assaying Blood Cell Populations of the Drosophila melanogaster Larva

In vertebrates, hematopoiesis is regulated by inductive microenvironments (niches). Likewise, in the invertebrate model organism&#160;Drosophila melanogaster, inductive microenvironments known as larval Hematopoietic Pockets (HPs) have been identified as anatomical sites for the development and regulation of blood cells (hemocytes), in particular of the self-renewing macrophage lineage.&#160;HPs are segmentally repeated pockets between the epidermis and muscle layers of the larva, which also comprise sensory neurons of the peripheral nervous system. In the larva, resident (sessile) hemocytes are exposed to anti-apoptotic, adhesive and proliferative cues from these sensory neurons and potentially other components of the HPs, such as the lining muscle and epithelial layers. During normal development, gradual release of resident hemocytes from the HPs fuels the population of circulating hemocytes, which culminates in the release of most of the resident hemocytes at the beginning of metamorphosis. Immune assaults, physical injury or mechanical disturbance trigger the premature release of resident hemocytes into circulation. The switch of larval hemocytes between resident locations and circulation raises the need for a common standard/procedure to selectively isolate and quantify these two populations of blood cells from single Drosophila larvae. Accordingly, this protocol describes an automated method to release and quantify the resident and circulating hemocytes from single larvae. The method facilitates ex vivo approaches, and may be adapted to serve a variety of developmental stages of Drosophila and other invertebrate organisms.

Assaying Blood Cell Populations of the Drosophila melanogaster Larva

Drosophila blood cells, or hemocytes, cycle between resident sites and circulation. In the larva, resident (sessile) hemocytes localize to inductive microenvironments, the Hematopoietic Pockets, while circulating hemocytes move freely in the hemolymph. The goal of this protocol is the standardized isolation and quantification of these two, behaviorally distinct but interchanging, hemocyte populations.

In vertebrates, hematopoiesis is regulated by inductive microenvironments (niches). Likewise, in the invertebrate model organism&#160;Drosophila ...

Rearing the Fruit Fly Drosophila melanogaster Under Axenic and Gnotobiotic Conditions

The influence of microbes on myriad animal traits and behaviors has been increasingly recognized in recent years. The fruit fly Drosophila melanogaster is a model for understanding microbial interactions with animal hosts, facilitated by approaches to rear large sample sizes of Drosophila under microorganism-free (axenic) conditions, or with defined microbial communities (gnotobiotic). This work outlines a method for collection of Drosophila embryos, hypochlorite dechorionation and sterilization, and transfer to sterile diet. Sterilized embryos are transferred to sterile diet in 50 ml centrifuge tubes, and developing larvae and adults remain free of any exogenous microbes until the vials are opened. Alternatively, flies with a defined microbiota can be reared by inoculating sterile diet and embryos with microbial species of interest. We describe the introduction of 4 bacterial species to establish a representative gnotobiotic microbiota in Drosophila. Finally, we describe approaches for confirming bacterial community composition, including testing if axenic Drosophila remain bacteria-free into adulthood.

Rearing the Fruit Fly Drosophila melanogaster Under Axenic and Gnotobiotic Conditions

A method for rearing Drosophila melanogaster under axenic and gnotobiotic conditions is presented. Fly embryos are dechorionated in sodium hypochlorite, transferred aseptically to sterile diet, and reared in closed containers. Inoculating diet and embryos with bacteria leads to gnotobiotic associations, and bacterial presence is confirmed by plating whole-body Drosophila homogenates.

The influence of microbes on myriad animal traits and behaviors has been increasingly recognized in recent years. The fruit fly Drosophila melanogaster is ...

Visualizing the Interrenal Steroidogenic Tissue and Its Vascular Microenvironment in Zebrafish

This protocol introduces how to detect differentiated interrenal steroidogenic cells through a simple whole-mount enzymatic activity assay. Identifying differentiated steroidogenic tissues through chromogenic histochemical staining of 3-&#946;-Hydroxysteroid dehydrogenase /&#916;5-4 isomerase (3&#946;-Hsd) activity-positive cells is critical for monitoring the morphology and differentiation of adrenocortical and interrenal tissues in mammals and teleosts, respectively. In the zebrafish model, the optical transparency and tissue permeability of the developing embryos and larvae allow for whole-mount staining of 3&#946;-Hsd activity. This staining protocol, as performed on transgenic fluorescent reporter lines marking the developing pronephric and endothelial cells, enables the detection of the steroidogenic interrenal tissue in addition to the kidney and neighboring vasculature. In combination with vibratome sectioning, immunohistochemistry, and confocal microscopy, we can visualize and assay the vascular microenvironment of interrenal steroidogenic tissues. The 3&#946;-Hsd activity assay is essential for studying the cell biology of the zebrafish interrenal gland because to date, no suitable antibody is available for labeling zebrafish steroidogenic cells. Furthermore, this assay is rapid and simple, thus providing a powerful tool for mutant screens targeting adrenal (interrenal) genetic disorders as well as for determining disruption effects of chemicals on steroidogenesis in pharmaceutical or toxicological studies.

The interrenal gland in zebrafish is the teleostean counterpart of the mammalian adrenal gland. This protocol introduces how to perform the 3-&#946;-hydroxysteroid dehydrogenase (&#916;5-4 isomerase; 3&#946;-Hsd) enzymatic activity assay, which detects differentiated steroidogenic cells in the developing zebrafish.

This protocol introduces how to detect differentiated interrenal steroidogenic cells through a simple whole-mount enzymatic activity assay. Identifying ...

High-resolution Episcopic Microscopy (HREM) - Simple and Robust Protocols for Processing and Visualizing Organic Materials

We provide simple protocols for generating digital volume data with the high-resolution episcopic microscopy (HREM) method. HREM is capable of imaging organic materials with volumes up to 5 x 5 x 7 mm3 in typical numeric resolutions between 1 x 1 x 1 and 5 x 5 x 5 &#181;m3. Specimens are embedded in methacrylate resin and sectioned on a microtome. After each section an image of the block surface is captured with a digital video camera that sits on the phototube connected to the compound microscope head. The optical axis passes through a green fluorescent protein (GFP) filter cube and is aligned with a position, at which the bock holder arm comes to rest after each section. In this way, a series of inherently aligned digital images, displaying subsequent block surfaces are produced. Loading such an image series in three-dimensional (3D) visualization software facilitates the immediate conversion to digital volume data, which permit virtual sectioning in various orthogonal and oblique planes and the creation of volume and surface rendered computer models. We present three simple, tissue specific protocols for processing various groups of organic specimens, including mouse, chick, quail, frog and zebra fish embryos, human biopsy material, uncoated paper and skin replacement material.

High-resolution Episcopic Microscopy HREM - Simple and Robust Protocols for Processing and Visualizing Organic Materials

We provide simple and robust protocols for processing biopsy material of various species, embryos of biomedical model organisms and samples of other organic tissues in order to permit digital volume data generation with the high-resolution episcopic microscopy method.

We provide simple protocols for generating digital volume data with the high-resolution episcopic microscopy (HREM) method. HREM is capable of imaging ...

Dissection and Immunofluorescent Staining of Mushroom Body and Photoreceptor Neurons in Adult Drosophila melanogaster Brains

Nervous system development involves a sequential series of events that are coordinated by several signaling pathways and regulatory networks. Many of the proteins involved in these pathways are evolutionarily conserved between mammals and other eukaryotes, such as the fruit fly Drosophila melanogaster, suggesting that similar organizing principles exist during the development of these organisms. Importantly, Drosophila has been used extensively to identify cellular and molecular mechanisms regulating processes that are required in mammals including neurogenesis, differentiation, axonal guidance, and synaptogenesis. Flies have also been used successfully to model a variety of human neurodevelopmental diseases. Here we describe a protocol for the step-by-step microdissection, fixation, and immunofluorescent localization of proteins within the adult Drosophila brain. This protocol focuses on two example neuronal populations, mushroom body neurons and retinal photoreceptors, and includes optional steps to trace individual mushroom body neurons using Mosaic Analysis with a Repressible Cell Marker (MARCM) technique. Example data from both wild-type and mutant brains are shown along with a brief description of a scoring criteria for axonal guidance defects. While this protocol highlights two well-established antibodies for investigating the morphology of mushroom body and photoreceptor neurons, other Drosophila brain regions and the localization of proteins within other brain regions can also be investigated using this protocol.

Dissection and Immunofluorescent Staining of Mushroom Body and Photoreceptor Neurons in Adult Drosophila melanogaster Brains

This protocol describes the dissection and immunostaining of adult Drosophila melanogaster brain tissues. Specifically, this protocol highlights the use of Drosophila mushroom body and photoreceptor neurons as example neuronal subsets that can be accurately used to uncover general principles underlying many aspects of neuronal development.

Nervous system development involves a sequential series of events that are coordinated by several signaling pathways and regulatory networks. Many of the ...

Whole-mount Clearing and Staining of Arabidopsis Flower Organs and Siliques

Due to its formidable tools for molecular genetic studies, Arabidopsis thaliana is one of the most prominent model species in plant biology and, especially, in plant reproductive biology. However, plant morphological, anatomical, and ultrastructural analyses traditionally involve time-consuming embedding and sectioning procedures for bright field, scanning, and electron microscopy. Recent progress in confocal fluorescence microscopy, state-of-the-art 3-D computer-aided microscopic analyses, and the continuous refinement of molecular techniques to be used on minimally processed whole-mount specimens, has led to an increased demand for developing efficient and minimal sample processing techniques. In this protocol, we describe techniques for properly dissecting Arabidopsis flowers and siliques, basic clearing techniques, and some staining procedures for whole-mount observations of reproductive structures.

Whole-mount Clearing and Staining of Arabidopsis Flower Organs and Siliques

In this protocol, we describe techniques for the proper dissection of Arabidopsis flowers and siliques, some basic clearing techniques, and selected staining procedures for whole-mount observations of reproductive structures.

Due to its formidable tools for molecular genetic studies, Arabidopsis thaliana is one of the most prominent model species in plant biology and, ...

Three-dimensional Rendering and Analysis of Immunolabeled, Clarified Human Placental Villous Vascular Networks

Nutrient and gas exchange between mother and fetus occurs at the interface of the maternal intervillous blood and the vast villous capillary network that makes up much of the parenchyma of the human placenta. The distal villous capillary network is the terminus of the fetal blood supply after several generations of branching of vessels extending out from the umbilical cord. This network has a contiguous cellular sheath, the syncytial trophoblast barrier layer, which prevents mixing of fetal blood and the maternal blood in which it is continuously bathed. Insults to the integrity of the placental capillary network, occurring in disorders such as maternal diabetes, hypertension and obesity, have consequences that present serious health risks for the fetus, infant, and adult. To better define the structural effects of these insults, a protocol was developed for this study that captures capillary network structure on the order of 1 - 2 mm3 wherein one can investigate its topological features in its full complexity. To accomplish this, clusters of terminal villi from placenta are dissected, and the trophoblast layer and the capillary endothelia are immunolabeled. These samples are then clarified with a new tissue clearing process which makes it possible to acquire confocal image stacks to z- depths of ~1 mm. The three-dimensional renderings of these stacks are then processed and analyzed to generate basic capillary network measures such as volume, number of capillary branches, and capillary branch end points, as validation of the suitability of this approach for capillary network characterization.

This study presents a protocol for the reversible tissue clearing, immunostaining, 3D-rendering and analysis of vascular networks in human placenta villi samples on the order of 1 - 2 mm3.

Nutrient and gas exchange between mother and fetus occurs at the interface of the maternal intervillous blood and the vast villous capillary network that ...

Three-dimensional Organotypic Cultures of Vestibular and Auditory Sensory Organs

The sensory organs of the inner ear are challenging to study in mammals due to their inaccessibility to experimental manipulation and optical observation. Moreover, although existing culture techniques allow biochemical perturbations, these methods do not provide a means to study the effects of mechanical force and tissue stiffness during development of the inner ear sensory organs. Here we describe a method for three-dimensional organotypic culture of the intact murine utricle and cochlea that overcomes these limitations. The technique for adjustment of a three-dimensional matrix stiffness described here permits manipulation of the elastic force opposing tissue growth. This method can therefore be used to study the role of mechanical forces during inner ear development. Additionally, the cultures permit virus-mediated gene delivery, which can be used for gain- and loss-of-function experiments. This culture method preserves innate hair cells and supporting cells and serves as a potentially superior alternative to the traditional two-dimensional culture of vestibular and auditory sensory organs.

Three-dimensional organotypic cultures of the murine utricle and cochlea in optically clear collagen I gels preserve innate tissue morphology, allow for mechanical stimulation through adjustment of matrix stiffness, and permit virus-mediated gene delivery.

The sensory organs of the inner ear are challenging to study in mammals due to their inaccessibility to experimental manipulation and optical observation. ...

Visualizing the Node and Notochordal Plate In Gastrulating Mouse Embryos Using Scanning Electron Microscopy and Whole Mount Immunofluorescence

The post-implantation mouse embryo undergoes major shape changes after the initiation of gastrulation and morphogenesis. A hallmark of morphogenesis is the formation of the transient organizers, the node and notochordal plate, from cells that have passed through the primitive streak. The proper formation of these signaling centers is essential for the development of the body plan and techniques to visualize them are of high interest to mouse developmental biologists. The node and notochordal plate lie on the ventral surface of gastrulating mouse embryos around embryonic day (E) 7.5 of development. The node is a cup-shaped structure whose cells possess a single slender cilium each. The proper subcellular localization and rotation of the cilia in the node pit determines left-right asymmetry. The notochordal plate cells also possess single cilia albeit shorter than those of the node cells. The notochordal plate forms the notochord which acts as an important signaling organizer for somitogenesis and neural patterning. Because the cells of the node and notochordal plate are transiently present on the surface and possess cilia, they can be visualized using scanning electron microscopy (SEM). Among other techniques used to visualize these structures at the cellular level is whole mount immunofluorescence (WMIF) using the antibodies against the proteins that are highly expressed in the node and notochordal plate. In this report, we describe our optimized protocols to perform SEM and WMIF of the node and notochordal plate in developing mouse embryos to help in the assessment of tissue shape and cellular organization in wild-type and gastrulation mutant embryos.

The node and notochordal plate are transient signaling organizers in developing mouse embryos that can be visualized using several techniques. Here, we describe in detail how to perform two of the techniques to study their structure and morphogenesis: 1) scanning electron microscopy (SEM); and 2) whole mount immunofluorescence (WMIF).

The post-implantation mouse embryo undergoes major shape changes after the initiation of gastrulation and morphogenesis. A hallmark of morphogenesis is ...

Isolation of Embryonic Tissues and Formation of Quail-Chicken Chimeric Organs Using The Thymus Example

The capacity to isolate embryonic tissues was an essential step for establishing the quail-chicken chimera system, which in turn has provided undisputed contributions to unveiling key processes in developmental biology.
Herein is described an optimized method to isolate embryonic tissues from quail and chickens by microsurgery and enzymatic digestion while preserving its biological properties. After isolation, tissues from both species are associated in an in vitro organotypic assay for 48 h. Quail and chicken tissues can be discriminated by distinct nuclear features and molecular markers allowing the study of the cellular cross-talk between heterospecific association of tissues. This approach is, therefore, a useful tool for studying complex tissue interactions in developmental processes with highly dynamic spatial modifications, such as those occurring during pharyngeal morphogenesis and the formation of the foregut endoderm-derived organs. This experimental approach was first developed to study the epithelial-mesenchymal interactions during early-stages of thymus formation. In this, the endoderm-derived prospective thymic rudiment and mesoderm-derived mesenchyme, were isolated from quail and chicken embryos, respectively.
The capacity of the associated tissues to generate organs can be further tested by grafting them onto the chorioallantoic membrane (CAM) of a chicken embryo. The CAM provides nutrients and allows gas exchanges to the explanted tissues. After 10 days of in ovo development, the chimeric organs can be analyzed in the harvested explants by conventional morphological methods. This procedure also allows studying tissue-specific contributions during organ formation, from its initial development (in vitro development) to the final stages of organogenesis (in ovo development).
Finally, the improved isolation method also provides three-dimensionally (3D) preserved embryonic tissues, that can also be used for high-resolution topographical analysis of tissue-specific gene-expression patterns.

This article provides a method to isolate pure embryonic tissues from quail and chicken embryos that can be combined to form ex vivo chimeric organs.

The capacity to isolate embryonic tissues was an essential step for establishing the quail-chicken chimera system, which in turn has provided undisputed ...