The authors gratefully acknowledge the work of Liuliu Zheng and Zenghui Xue, who helped pioneer this technique in the Sokac lab, as well as Hasan Seede who helped with the analysis. The work for this study is funded by a grant from NIH (R01 GM115111).

1. Prepare embryo collection cups and apple juice agar plates
<ol>
	<li>Five days prior to the injection experiment, construct28 or procure at least two small&#160;embryo collection cups. Make fresh 60 mm apple juice agar plates to be used with small collection cups28. Store plates in plastic boxes covered with damp paper towels at 4 &#176;C. 
	NOTE: Small embryo collection cups, populated with fly numbers as described in step 1.3, will provide sufficient embryo numbers per experiment, while also ensuring that embryo handling and injection can be done in a short enough time to allow imaging of early developmental stages.</li>
	<li>Warm apple juice plates to 18 &#176;C and add a dab of yeast paste to the center of the plate. Yeast paste is a simple paste of active yeast and distilled water.</li>
	<li>To promote the most generous egg laying, set up collection cups with flies 2 days prior to the experiment. Add at least 100 females and 50 male flies to the collection cups, and top with a prepared apple juice plate (Figure 1, step 1). On the days leading up to the injection experiment change the apple juice plates at least twice each day, once in the morning and once in the evening. 
	NOTE: The best injection and imaging results are obtained when embryo collection cups are kept at 18 &#176;C with a 12 h light on/light off cycle.</li>
</ol>
2. Prepare a working stock solution of G-actinRed for microinjection
NOTE: This preparation only makes 2 &#956;L of a 5 mg/mL working stock of G-actinRed, so if users are unaccustomed to the microinjection technique, it is advantageous to skip to step 3 and practice the microinjections with a neutral pH buffer to conserve precious working stock. The 10 &#956;g stock of G-actinRed from the vendor can be stored in its original packaging in a 16 oz screw top jar with ~500 g of desiccant at 4 &#176;C for up to 6 months.
<ol>
	<li>Prepare a G-buffer stock solution in advance: 5 mM Tris-HCl, 0.2 mM CaCl2, pH 8.0. Filter and store at room temperature.</li>
	<li>On the day of injections, prepare 1 mL of a G-buffer working solution in a fresh snap cap microcentrifuge tube on ice using the G-buffer stock from step 2.1, supplemented with the following at the indicated final concentrations: 1 mM dithiothreitol (DTT) and 0.2 mM ATP, pH 8.0. 
	NOTE: The 1 mL volume of G-buffer working solution is more than what is needed for an experiment but simplifies the preparation. Excess can be discarded after the experiment or users can scale down according to their preference.
	<ol>
		<li>Keeping the 10 &#956;g G-actinRed stock on ice, first add 1 &#956;L of filtered, distilled water to the top of the pink droplet of G-actinRed inside the tube.</li>
		<li>Next, add 1 &#956;L of the cold, freshly prepared G-buffer working solution from step 2.2. Pipet up and down ~20 times to mix well with the pipette volume set to 1 &#956;L. The G-actinRed stock will now be at the final dilution of 5 mg/mL.</li>
	</ol>
	</li>
	<li>Incubate the prepared G-actinRed for 30 min on ice undisturbed.</li>
	<li>Centrifuge the prepared G-actinRed at 16,000 x g for 20 min at 4 &#176;C in a microcentrifuge to remove any precipitate.</li>
	<li>Carefully pipet 1.5 &#956;L of the supernatant into a fresh snap cap microcentrifuge tube on ice, avoiding the dark pink pellet.</li>
	<li>Store the prepared G-actinRed supernatant on ice for up to 6 h until ready to load into a microneedle. 
	NOTE: Microneedles can be pulled from capillary tubes in advance on a micropipette puller, then stored at room temperature on a strip of modeling clay in a 100 x 20 mm Petri dish. Suggested parameters for microneedle pulling can be found in the Pipette Cookbook29.</li>
</ol>
3. Collect embryos and mount for injection
<ol>
	<li>Allow flies to lay embryos for 30 min on apple juice plates with yeast paste at 18 &#176;C.</li>
	<li>While flies are laying, pre-warm an apple juice agar plate without yeast paste to room temperature, cut out a 4 cm x 1 cm rectangular wedge of apple juice agar with a razor blade, and place on a 25 mm x 75 mm glass slide.
	<ol>
		<li>Harvest plate from the 30 minute collection and dechorionate embryos by pouring fresh bleach, diluted 1:1 with distilled water, onto the plate and swirling the plate for 1 min, as described in28 (Figure 1, step 2). 
		NOTE: Different brands of bleach are sold at different concentrations. The bleach used here is 6% sodium hypochlorite from the bottle and is diluted to a final concentration of 3% sodium hypochlorite. Other bleach brands at slightly lower concentrations will work equally well.</li>
		<li>Pour the bleach and dechorionated embryos into a collection basket (a 70 &#956;m cell strainer) and rinse the plate twice with distilled water from a squirt bottle, adding these washes to the collection basket.</li>
		<li>Vigorously rinse the dechorionated embryos in the collection basket with distilled water until no yeast clumps are visible and the basket leaves no pink marks from excess bleach when blotted on a paper towel.</li>
	</ol>
	</li>
	<li>Using a paintbrush with bristles dampened with distilled water, transfer dechorionated and washed embryos from the collection basket onto the prepared apple juice agar wedge on the glass slide.</li>
	<li>Use a pair of fine tip tweezers or a dissecting needle to arrange ten embryos in a straight line along the long axis of the rectangular agar wedge (Figure 1, step 3). Arrange the embryos head-to-tail, such that their anterior pole is facing to the right and dorsal side is facing the researcher (Figure 1, step 3, magnified).</li>
	<li>Cut off 0.5 cm of the end of a P200 pipette tip with a razor blade and dip into the &#8220;embryo glue&#8221; (described in28). Generously coat a region 5 mm in width (Figure 1, step 4) along the long edge of a 24 mm x 50 mm rectangular coverslip, and let dry, glue side up. Drying will take ~30 s and is complete once the entire glue-coated region appears matte rather than wet or shiny. 
	NOTE: Prepare &#8220;embryo glue&#8221; at least 48 h in advance. Add n-Heptane to strips of double-sided tape in a scintillation vial as described in28.</li>
	<li>Once the &#8220;embryo glue&#8221; has dried, gently place the coverslip glue side down on top of the row of aligned embryos on the agar, leaving 2-3 mm of space between the edge of the coverslip and the row of embryos. 
	NOTE: Sticking the embryos too close to the edge of the coverslip may lead to the embryos drying out too much during the course of the experiment.</li>
	<li>Flip the coverslip over so that the embryos are now facing up. They should be stuck in a line along one long edge of the coverslip, and their ventral region facing the closest edge of the coverslip (Figure 1, step 4, magnified).</li>
	<li>Desiccate the embryos by placing the coverslip with embryos gently on top of 150 g of fresh blue desiccant stored in a 16 oz screw top jar. Tightly screw on the lid and incubate for 8-10 min (Figure 1, step 5).</li>
	<li>After desiccation, remove the coverslip from the desiccant jar and tape each short side of the coverslip to a microscope slide, embryo side up, with two 4 cm2 pieces of double-sided tape so that the embryo coverslip will fit onto the injection stage (Figure 1, step 6).</li>
	<li>Add 2-3 drops of Halocarbon 27 oil with a Pasteur pipette to cover the aligned embryos and protect them from further dehydration (Figure 1, step 6).</li>
</ol>
4. Inject and heat stress embryos to promote actin rod formation
NOTE: All injections are done in a temperature-controlled room at 18 &#176;C.
<ol>
	<li>Prepare humid incubation chambers from a glass Petri dish at least 100 mm x 20 mm in size and line the chamber with twists of lab tissue wipers dampened with distilled water (Figure 1, step 8). Pre-warm the incubation chambers at 32 &#176;C or the desired incubation temperature prior to injecting embryos.</li>
	<li>Open the airflow valve for the microinjector and turn on the microinjector (compressed air or house air with a pressure of at least 90 psi is suitable).</li>
	<li>While embryos are desiccating, backload the previously prepared G-actinRed supernatant into the microneedle using a micro loader tip. Set the pipette to draw up 1-1.5 &#956;L. 
	NOTE: Because of the viscosity of the actin, loading volumes may not be accurate and there may be enough actin left to load at least one to two more microneedles. Up to 60 embryos can be injected per loaded microneedle if the microneedle is calibrated properly and does not become clogged during the course of the experiment.</li>
	<li>Attach the microneedle to the needle holder and tighten the screw. Connect the air tube to the microinjector and ensure that the backflow pressure on the microneedle equilibrates to 30 hPa.</li>
	<li>Calibrate the microinjector settings to expel a 100 &#956;m diameter bubble of G-actinRed (~500 pL) on a slide micrometer. Rotate the pressure knob (500-1500 hPa) and injection pulse time knob (0.1-0.5 s) on the microinjector to get the right bubble size. Adjust these settings each time a new microneedle is loaded to account for variability in actin viscosity and microneedle tip size. 
	NOTE: The prepared G-actinRed is viscous and there may be air in the tip of the microneedle that should be expelled before injecting embryos. If the G-actinRed does not readily expel from the tip of the microneedle, gently break the microneedle tip against the edge of the slide micrometer.</li>
	<li>Place the slide with mounted embryos onto the microscope stage. 
	NOTE: Every injection set up will be different, so researchers will have to adjust their injection method accordingly. Here the embryos are moved with respect to a stationary microneedle, injecting each embryo by running the embryo into the microneedle.</li>
	<li>Adjust the micromanipulator stage and focus of the 10x objective on the light microscope so that the embryos are visible. The embryos are in the correct focal plane when the outlines of the vitelline membrane are sharpest and the embryo appears largest. Choose embryos to inject that are in the correct developmental stage, so that by the time the post-injection incubation is complete, most of the clutch reaches the desired developmental stage (e.g., inject embryos at Bownes&#8217; stage 2-330 in order to observe rods at cellularization after heat stress at 32 &#176;C).</li>
	<li>Use the microneedle controls to bring the needle into the same focal plane as the embryos. 
	NOTE: If the microneedle catches on the coverslip while moving the stage or microneedle, then the microneedle is too close to the slide and is not in the correct focal plane. The microneedle should be parallel to the coverslip, and not at a significant angle (Figure 1, step 7).</li>
	<li>Insert the microneedle into the embryo so that it hits the embryo in the middle of its ventral region, at the embryo &#8220;equator&#8221;. Trigger injection with the foot pedal or &#8220;inject&#8221; button when the microneedle tip is visible inside the middle of the embryo (Figure 1, step 7).</li>
	<li>Inject the G-actinRed once and slowly remove the microneedle. Move the stage and repeat for each embryo of the appropriate developmental stage. 
	NOTE: Expansion of the embryo is normal as the G-actinRed is injected and a bit of cytoplasm may leak out of the embryo.</li>
	<li>After all the embryos have been injected, place the slide with the embryos in the prepared humid incubation chamber and close the lid (Figure 1, step 8). If trying to obtain embryos that reach cellularization, heat stress the embryos at 32 &#176;C for 60-75 min in the humid incubation chamber. 
	NOTE: Incubation times are noted that allow visualization of rods in cellularizing heat stressed embryos. The incubation time will be longer for non heat stress control embryos because development will be slower at a lower temperature31. These control embryos can be incubated in humid chambers at temperatures such as 18 &#176;C or 25 &#176;C, depending on design of the specific experiment and the question to be asked. The minimum incubation time necessary for the G-actinRed to diffuse throughout the embryo is 30 min.</li>
</ol>
5. Image actin rods in heat stressed embryos by confocal microscopy
<ol>
	<li>While the embryos are being heat stressed, turn on the confocal microscope and select the 561 nm laser channel.</li>
	<li>Move the objective lens (25x, 40x or 63x recommended) to the working position.</li>
	<li>If imaging heat stressed embryos, then set the heated stage incubator to achieve an internal temperature of 32 &#176;C. A point-and-shoot or infrared thermometer can be used to check the temperature at or near the objective.</li>
	<li>Remove the slide with injected embryos from the humid incubation chamber after incubation is complete (Figure 1, step 9).</li>
	<li>Working quickly, gently pry off the double-sided tape pieces that were used to adhere the coverslip with mounted embryos to the slide (Figure 1, step 9). 
	CAUTION: Be gentle during these steps as coverslips can easily shatter if too much force is applied.</li>
	<li>Stick two 2.5 cm long pieces of double-sided tape together and cut the tape in half lengthwise to make two strips, 2.5 x 0.5 cm long (Figure 1, step 10).</li>
	<li>Stick two-thirds of the length of each tape strip onto the first coverslip, flanking each side of the embryos in Halocarbon 27 oil (Figure 1, step 10, orange), leaving one-third of the tape strips hanging off the edge of the first coverslip where the embryos are stuck. Use gloved hands and be careful not to touch the embryos during this step.</li>
	<li>Gently place a second rectangular coverslip on top of the tape strips to sandwich the embryos between the coverslips (Figure 1, step 10, blue). Align the 25 mm edges but keep the 50 mm edges offset from one another by 1 cm in width. 
	NOTE: This second coverslip&#8217;s full surface will become the new imaging surface that will face the objective lens, so take care not to get fingerprints or Halocarbon 27 oil on this second coverslip surface. The offset is necessary so that extra Halocarbon 27 oil can be added to evenly immerse the embryos. If needed, add Halocarbon 27 oil at the seam where the two coverslips meet at the top of the sandwich and it will coat the embryos by capillary action (see dashed lines in Figure 1, step 10).</li>
	<li>Gently tap down on the areas of the coverslip that are directly on top of the tape strips with the blunt side of a razorblade to get the coverslip to adhere to the tape.</li>
	<li>Flip the coverslip sandwich over and place on a lab tissue wiper to keep the imaging surface clean and carry to the confocal microscope (Figure 1, step 11). Ensure that the tape is completely stuck to both coverslips before imaging.</li>
	<li>Confirm that the heated stage is at temperature and if using an inverted microscope, add immersion liquid onto the selected objective lens.</li>
	<li>Place the coverslip sandwich onto the stage carefully to ensure that the new imaging surface (2nd coverslip) is the one touching the immersion liquid (Figure 1, step 11). 
	NOTE: If needed, adhere the coverslip sandwich to the stage with two small pieces of double-sided tape to prevent unnecessary movement during imaging if the coverslips do not fit well in the heated stage.</li>
	<li>Focus on an embryo that is in cellularization (Bownes stage 4a30) or desired developmental stage using either transmitted light or fluorescence.</li>
	<li>Once an embryo has been brought into focus, switch to the laser acquisition mode on the confocal microscope and adjust laser power and gain, frame size, tiling, and projection settings as desired.</li>
	<li>Take surface-view images through the focal planes of the embryo&#8217;s nuclei to find intranuclear actin rods. Rods should appear in multiple orientations as bright streaks or dots inside the comparatively dark nuclei (Figure 2A, 2C).</li>
</ol>
6. Alternative imaging experiments
<ol>
	<li>Perform FRAP to investigate actin turnover along the length of intranuclear actin rods or in cytoplasmic actin structures, such as the tips of the plasma membrane furrows during cellularization.</li>
	<li>In the imaging software, choose a rectangular region around furrow tips or actin rods in which to acquire the experiment.</li>
	<li>Choose a small square region of the center of an actin rod within the rectangular acquisition region to bleach. Ensure that the tips of the actin rod are visible and do not get bleached during the course of the experiment to allow for accurate tracking of the rod inside the nucleus.</li>
	<li>Set the bleach laser to iterate 50x and set the bleach laser power to maximum.</li>
	<li>Choose a time course to acquire images every second for a total up to 120 s at maximum pixel dwell speed and set the laser to bleach after the first two seconds of image acquisition.</li>
	<li>Quantify the data to determine the half-time of fluorescence recovery1.</li>
</ol>

<ol>
	<li>Figard, L., 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=Cofilin-mediated+Actin+Stress+Response+is+maladaptive+in+heat-stressed+embryos.">Cofilin-mediated Actin Stress Response is maladaptive in heat-stressed embryos.</a> Cell Reports. 26 (49), 3493-3501 (2019).</li><li>Ashworth, S. L., 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=ADF/cofilin+mediates+actin+cytoskeletal+alterations+in+LLC-PK+cells+during+ATP+depletion.">ADF/cofilin mediates actin cytoskeletal alterations in LLC-PK cells during ATP depletion.</a> American Journal of Physiology Renal Physiology. 284 (4), 852-862 (2003).</li><li>Vandebrouck, 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=In+vitro+analysis+of+rod+composition+and+actin+dynamics+in+inherited+myopathies.">In vitro analysis of rod composition and actin dynamics in inherited myopathies.</a> Journal of Neuropathology and Experimental Neurology. 69 (5), 429-441 (2010).</li><li>Minamide, L. S., Striegl, A. M., Boyle, J. A., Meberg, P. J., Bamburg, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neurodegenerative+stimuli+induce+persistent+ADF/cofilin-actin+rods+that+disrupt+distal+neurite+function.">Neurodegenerative stimuli induce persistent ADF/cofilin-actin rods that disrupt distal neurite function.</a> Nature Cell Biology. 2 (9), 628-636 (2000).</li><li>Bamburg, J. 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=ADF/Cofilin-actin+rods+in+neurodegenerative+diseases.">ADF/Cofilin-actin rods in neurodegenerative diseases.</a> Current Alzheimer Research. 7 (3), 241-250 (2010).</li><li>Bamburg, J. R., Bernstein, B. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Actin+dynamics+and+cofilin-actin+rods+in+alzheimer+disease.">Actin dynamics and cofilin-actin rods in alzheimer disease.</a> Cytoskeleton. 73 (9), 477-497 (2016).</li><li>Bernstein, B. W., Chen, H., Boyle, J. A., Bamburg, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Formation+of+actin-ADF/cofilin+rods+transiently+retards+decline+of+mitochondrial+potential+and+ATP+in+stressed+neurons.">Formation of actin-ADF/cofilin rods transiently retards decline of mitochondrial potential and ATP in stressed neurons.</a> AJP: Cell Physiology. 291 (5), 828-839 (2006).</li><li>Munsie, L. N., Desmond, C. R., Truant, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cofilin+nuclear-cytoplasmic+shuttling+affects+cofilin-actin+rod+formation+during+stress.">Cofilin nuclear-cytoplasmic shuttling affects cofilin-actin rod formation during stress.</a> Journal of Cell Science. 125 (17), 3977-3988 (2012).</li><li>Iida, K., Iida, H., Yahara, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heat+shock+induction+of+intranuclear+actin+rods+in+cultured+mammalian+cells.">Heat shock induction of intranuclear actin rods in cultured mammalian cells.</a> Experimental Cell Research. 165, 207-215 (1986).</li><li>Ohta, Y., Nishida, E., Sakai, H., Miyamoto, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dephosphorylation+of+cofilin+accompanies+heat+shock-induced+nuclear+accumulation+of+cofilin.">Dephosphorylation of cofilin accompanies heat shock-induced nuclear accumulation of cofilin.</a> Journal of Biological Chemistry. 264 (27), 16143-16148 (1989).</li><li>Iida, K., Matsumoto, S., Yahara, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+KKRKK+sequence+is+involved+in+heat+shock-induced+nuclear+translocation+of+the+18-kDa+actin-binding+protein,+cofilin.">The KKRKK sequence is involved in heat shock-induced nuclear translocation of the 18-kDa actin-binding protein, cofilin.</a> Cell Structure and Function. 17 (1), 39-46 (1992).</li><li>Minamide, L. S., 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=Isolation+and+characterization+of+cytoplasmic+cofilin-actin+rods.">Isolation and characterization of cytoplasmic cofilin-actin rods.</a> Journal of Biological Chemistry. 285 (8), 5450-5460 (2010).</li><li>Masurovsky, E. B., Benitez, H. H., Kim, S. U., Murray, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Origin,+development,+and+nature+of+intranuclear+rodlets+and+associated+bodies+in+chicken+sympathetic+neurons.">Origin, development, and nature of intranuclear rodlets and associated bodies in chicken sympathetic neurons.</a> The Journal of Cell Biology. 44 (7), 172-191 (1970).</li><li>Feldman, M. L., Peters, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intranuclear+rods+and+sheets+in+rat+cochlear+nucleus.">Intranuclear rods and sheets in rat cochlear nucleus.</a> Journal of Neurocytology. 1 (2), 109-127 (1972).</li><li>Nishida, E., 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=Cofilin+is+a+component+of+intranuclear+and+cytoplasmic+actin+rods+induced+in+cultured+cells.">Cofilin is a component of intranuclear and cytoplasmic actin rods induced in cultured cells.</a> Cell Biology. 84 (8), 5262-5266 (1987).</li><li>Ono, S., Abe, H., Nagaoka, R., Obinata, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Colocalization+of+ADF+and+cofilin+in+intranuclear+actin+rods+of+cultured+muscle+cells.">Colocalization of ADF and cofilin in intranuclear actin rods of cultured muscle cells.</a> Journal of Muscle Research and Cell Motility. 14 (2), 195-204 (1993).</li><li>Xue, Z., Sokac, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Back-to-back+mechanisms+drive+actomyosin+ring+closure+during+Drosophila+embryo+cleavage.">Back-to-back mechanisms drive actomyosin ring closure during Drosophila embryo cleavage.</a> The Journal of Cell Biology. 215 (3), 335-344 (2016).</li><li>Cao, J., Albertson, R., Riggs, B., Field, C. M., Sullivan, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nuf,+a+Rab11+effector,+maintains+cytokinetic+furrow+integrity+by+promoting+local+actin+polymerization.">Nuf, a Rab11 effector, maintains cytokinetic furrow integrity by promoting local actin polymerization.</a> Journal of Cell Biology. 182 (2), 301-313 (2008).</li><li>Spracklen, A. J., Fagan, T. N., Lovander, K. E., Tootle, T. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+pros+and+cons+of+common+actin+labeling+tools+for+visualizing+actin+dynamics+during+Drosophila+oogenesis.">The pros and cons of common actin labeling tools for visualizing actin dynamics during Drosophila oogenesis.</a> Developmental Biology. 393 (2), 209-226 (2014).</li><li>Chen, Q., Nag, S., Pollard, T. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Formins+filter+modified+actin+subunits+during+processive+elongation.">Formins filter modified actin subunits during processive elongation.</a> Journal of Structural Biology. 177 (1), 32-39 (2012).</li><li>Iordanou, E., Chandran, R. R., Blackstone, N., Jiang, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RNAi+interference+by+dsRNA+injection+into+Drosophila+embryos.">RNAi interference by dsRNA injection into Drosophila embryos.</a> Journal of Visualized Experiments. (50), 2477 (2011).</li><li>Juarez, M. T., Patterson, R. A., Li, W., McGinnis, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microinjection+wound+assay+and+in+vivo+localization+of+epidermal+wound+response+reporters+in+Drosophila+embryos.">Microinjection wound assay and in vivo localization of epidermal wound response reporters in Drosophila embryos.</a> Journal of Visualized Experiments. 81, 50750 (2013).</li><li>Carreira-Rosario, 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=Recombineering+homologous+recombination+constructs+in+Drosophila.">Recombineering homologous recombination constructs in Drosophila.</a> Journal of Visualized Experiments. (77), 50346 (2013).</li><li>Brust-Mascher, I., Scholey, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microinjection+techniques+for+studying+mitosis+in+the+Drosophila+melanogaster+syncytial+embryo.">Microinjection techniques for studying mitosis in the Drosophila melanogaster syncytial embryo.</a> Journal of Visualized Experiments. (31), 1382 (2009).</li><li>Catrina, I. E., Bayer, L. V., Omar, O. S., Bratu, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualizing+and+tracking+endogenous+mRNAs+in+live+Drosophila+melanogaster+egg+chambers.">Visualizing and tracking endogenous mRNAs in live Drosophila melanogaster egg chambers.</a> Journal of Visualized Experiments. (148), 58545 (2019).</li><li>Wessel, A. D., Gumalla, M., Grosshans, J., Schmidt, 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=The+mechanical+properties+of+early+Drosophila+embryos+measured+by+high-speed+video+microrheology.">The mechanical properties of early Drosophila embryos measured by high-speed video microrheology.</a> Biophysical Journal. 108 (8), 1899-1907 (2015).</li><li>Mollinari, C., Gonz&#225;lez, A., Cid-Arregui, A., Garc&#237;a-Carranc&#225;, <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microinjection+and+transgenesis.">Microinjection and transgenesis.</a> Microinjection and Transgenesis: Strategies and Protocols. , 587-603 (1998).</li><li>Figard, L., Sokac, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+cell+shape+change+in+living+Drosophila+embryos.">Imaging cell shape change in living Drosophila embryos.</a> Journal of Visualized Experiments. (49), 2503 (2011).</li><li>Oesterle, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Pipette Cookbook 2018: P-97 and P-1000 Micropipette Pullers. , (2018).</li><li>Bownes, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+photographic+study+of+development+in+the+living+embryo+of+Drosophila+melanogaster.">A photographic study of development in the living embryo of Drosophila melanogaster.</a> Journal of Embryology and Experimental Morphology. 33 (3), 789-801 (1975).</li><li>Powsner, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effects+of+temperature+on+the+durations+of+the+developmental+stages+of+Drosophila+melanogaster.">The effects of temperature on the durations of the developmental stages of Drosophila melanogaster.</a> Physiological Zoology. 8 (4), 474-520 (1935).</li><li>Hunter, M. V., Willoughby, P. M., Bruce, A. E. E., Fernandez-Gonzalez, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxidative+Stress+Orchestrates+Cell+Polarity+to+Promote+Embryonic+Wound+Healing.">Oxidative Stress Orchestrates Cell Polarity to Promote Embryonic Wound Healing.</a> Developmental Cell. 47 (3), 377-387 (2018).</li></ol>

No conflicts of interests declared.

The significance of this method is that it utilizes the well-established protocol of microinjection in Drosophila embryos21,22,23,24,25,26,27 to enable new research regarding the ASR and accompanying actin rod assembly. A major advantage of injecting G-actinRed into live ...

This protocol describes how to inject G-actinRed to visualize the assembly of intranuclear actin rods in heat-stressed embryos that are undergoing an inducible Actin Stress Response (ASR)1. We developed this protocol to aid studies of the ASR, which in embryos leads to disrupted morphogenesis and reduced viability, and in adult human cell types is associated with pathologies including renal failure2, muscle myopathies3, and Alzheimer&#8217;s and Huntington&#8217;s Disease4,5,6,7,8. This ASR is induced by numerous cellular stresses, including heat shock9,10,11, oxidative stress4,6, reduced ATP synthesis12, and abnormal Huntingtin or &#946;-amyloid oligomerization4,5,6,7,9,13,14,15,16. A hallmark of the ASR is the assembly of aberrant actin rods in either the cytoplasm or nucleus of affected cells, which is driven by stress-induced hyperactivation of an actin interacting protein, Cofilin1,5,6,10. Unfortunately, key knowledge gaps remain regarding the ASR. For example, the function of the actin rods is not known. We do not understand why rods form in the cytoplasm of some cell types, but the nucleus of others. Nor is it clear whether the ASR is protective or maladaptive for cells or embryos undergoing stress. Finally, we still do not know the detailed mechanisms underlying Cofilin hyperactivation or actin rod assembly. Thus, this protocol provides a rapid and versatile assay to probe the ASR by visualizing actin rod formation and dynamics in the highly tractable experimental system of the living fruit fly embryo.
The protocol to microinject G-actinRed into living Drosophila embryos was initially developed to study the dynamics of normal cytoplasmic actin structures17 during tissue building events. In those studies, we found that G-actinRed injection did not adversely affect early developmental processes in the embryo, including cytokinesis or gastrulation17,18. We then modified the protocol, adapting the embryo handling and G-actinRed injection to allow imaging of actin rods in heat stressed embryos undergoing the ASR1. Other methods besides G-actinRed injection can be used to visualize actin in embryos. These methods rely on expressing fluorescent proteins (FPs) tagged to actin or to domains of actin binding proteins, such as Utrophin-mCherry, Lifeact, F-tractin-GFP, and Moesin-GFP (reviewed in19). However, using these FP probes requires caution because they can stabilize or disrupt some actin structures, do not equally label all actin structures20, and in the case of actin-GFP, are highly overexpressed &#8211; problematic for the analysis of rod assembly which is not only stress dependent but also actin concentration dependent1. Thus, G-actinRed is the preferred probe for rod studies in fly embryos, and the large size of the embryo allows its easy injection.
The workflow of this protocol is similar to other well-established microinjection techniques that have been used for injecting proteins, nucleic acids, drugs, and fluorescent indicators into Drosophila embryos21,22,23,24,25,26,27. However, following the microinjection of G-actinRed here, embryos are exposed to mild heat stress to induce the ASR and intranuclear actin rod assembly. For labs with access to flies and an injection rig, this method should be readily implementable and adaptable for specific lines of study in regard to the ASR, including its induction by different stresses or modulation in distinct genetic backgrounds.

<table border="0" cellpadding="0" cellspacing="0" style="width:837px;" width="838">
	<tbody>
		<tr height="40">
			<td height="40" style="height:40px;width:223px;">Adenosine triphosphate (ATP)</td>
			<td style="width:195px;">Millipore-Sigma</td>
			<td style="width:121px;">A23835G</td>
			<td style="width:299px;">Component of G buffer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Apple juice, Mott&#39;s, 64 fl oz</td>
			<td style="width:195px;">Mott&#39;s</td>
			<td style="width:121px;">014800000344</td>
			<td>Component of apple juice plates</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Bacto Agar</td>
			<td style="width:195px;">BD</td>
			<td style="width:121px;">214010</td>
			<td>Component of apple juice plates</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:223px;">Bleach, PureBright Germicidal, 6.0% sodium hypochlorite</td>
			<td style="width:195px;">KIK International</td>
			<td style="width:121px;">059647210020</td>
			<td>For dechorionating embryos</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Calcium chloride</td>
			<td style="width:195px;">Millipore-Sigma</td>
			<td style="width:121px;">C1016500G</td>
			<td>Component of G buffer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Cell strainer, 70 &#956;m</td>
			<td style="width:195px;">Falcon</td>
			<td style="width:121px;">352350</td>
			<td>For collecting dechorionated embryos</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:223px;">Confocal microscope, LSM 880 34-channel with Airyscan</td>
			<td style="width:195px;">Zeiss</td>
			<td style="width:121px;">0000001994956</td>
			<td>For imaging intranuclear actin rods</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Desiccant</td>
			<td style="width:195px;">Drierite</td>
			<td style="width:121px;">24001</td>
			<td>For desiccating embryos</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:223px;">Dissecting microscope, Stemi 508 Stereoscope with 8:1 zoom</td>
			<td style="width:195px;">Zeiss</td>
			<td style="width:121px;">4350649000000</td>
			<td>For arranging embryos on agar wedge</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Dissecting needle, 5 in</td>
			<td style="width:195px;">Fisher Scientific</td>
			<td style="width:121px;">08965A</td>
			<td>For arranging embryos on agar wedge</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Dithiothreitol (DTT)</td>
			<td style="width:195px;">Fisher Scientific</td>
			<td style="width:121px;">BP1725</td>
			<td>Component of G buffer</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:223px;">Double-sided Tape, Scotch Permanent, 0.5 in x 250 in</td>
			<td style="width:195px;">3M</td>
			<td>021200010323</td>
			<td>For making embryo glue</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Embryo collection cage</td>
			<td style="width:195px;">Genessee Scientific</td>
			<td style="width:121px;">59100</td>
			<td>For housing adult flies and collecting embryos</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:223px;">Fine tip tweezers, Dumont Tweezer, Style 5</td>
			<td style="width:195px;">Electron Microscopy Sciences</td>
			<td style="width:121px;">72701D</td>
			<td>For arranging embryos on agar wedge</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:223px;">Glass capillaries, Borosillicate glass, thin 1 mm x 0.75 mm</td>
			<td style="width:195px;">World Precision Instruments, Inc.</td>
			<td style="width:121px;">TW1004</td>
			<td>For microneedles</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Halocarbon oil 27</td>
			<td style="width:195px;">Millipore-Sigma</td>
			<td style="width:121px;">H8773100ML</td>
			<td>For hydration of embryos</td>
		</tr>
		<tr height="120">
			<td height="120" style="height:120px;width:223px;">Heated stage incubator</td>
			<td style="width:195px;">Zeiss</td>
			<td style="width:121px;">4118579020000, 4118609020000, 4118609010000</td>
			<td>For confocal imaging</td>
		</tr>
		<tr height="18">
			<td height="18" style="height:19px;width:223px;">Lab Tissue Wipers, KimWipes</td>
			<td style="width:195px;">Kimberly-Clark</td>
			<td style="width:121px;">34155</td>
			<td>Lab tissue wipers</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:223px;">Light microscope, Invertoskop 40C Inverted Phase contrast microscope, refurbished</td>
			<td style="width:195px;">Zeiss</td>
			<td style="width:121px;">Discontinued</td>
			<td>Injection microscope</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Methyl-4-hydroxybenzoate</td>
			<td style="width:195px;">Millipore-Sigma</td>
			<td style="width:121px;">H36471KG</td>
			<td>Component of apple juice plates</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Microinjector, FemtoJet4x</td>
			<td style="width:195px;">Eppendorf</td>
			<td>5253000025</td>
			<td>Microinjector</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:223px;">Micro loader tips, epT.I.P.S. 20 &#956;L</td>
			<td style="width:195px;">Eppendorf</td>
			<td style="width:121px;">5242956003</td>
			<td>For loading microneedles</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:223px;">Micromanipulator and injection stage with x,y,z dials for needle adjustment</td>
			<td style="width:195px;">Bernard Instruments, Inc (Houston, TX)</td>
			<td style="width:121px;">Custom</td>
			<td>For performing microinjections</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:223px;">Micropipette puller, Model P-97, Flaming/Brown</td>
			<td style="width:195px;">Sutter Instruments</td>
			<td style="width:121px;">P97</td>
			<td>For pulling capillary tubes to make microneedles</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:223px;">Microscope cover glass 24x50-1.5</td>
			<td style="width:195px;">Fisher Scientific</td>
			<td style="width:121px;">12544E</td>
			<td>For mounting embryos</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:223px;">Microscope slides, Lilac Colorfrost, Precleaned, 25 x 75 x 1mm</td>
			<td style="width:195px;">Fisher Scientific</td>
			<td style="width:121px;">22037081</td>
			<td>For mounting embryos for injection</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">n-Heptane</td>
			<td style="width:195px;">Fisher Scientific</td>
			<td style="width:121px;">H3601</td>
			<td>Component of embryo glue</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Objective, 10x</td>
			<td style="width:195px;">Zeiss</td>
			<td style="width:121px;">Discontinued</td>
			<td>10x objective for injection microscope</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:223px;">Objective, C-Apochromat 40x/1,2 W Korr. FCS</td>
			<td style="width:195px;">Zeiss</td>
			<td style="width:121px;">4217679971711</td>
			<td>40x water objective for confocal</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:41px;width:223px;">Objective, LD LCI Plan-Apochromat 25x/0.8 Imm Cor DIC M27 for oil, water, silicone oil or glycerine immersion (D=0-0.17mm) (WD=0.57mm at D=0.17mm)</td>
			<td style="width:195px;">Zeiss</td>
			<td style="width:121px;">4208529871000</td>
			<td>25x mixed immersion objective for confocal</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:223px;">Objective, Plan-Apocrhomat 63x/1.40 Oil DIC f/ELYRA</td>
			<td style="width:195px;">Zeiss</td>
			<td style="width:121px;">4207829900799</td>
			<td>63x oil objective for confocal</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:223px;">Paintbrush, Robert Simmons Expression E85 Pointed Round size 2</td>
			<td style="width:195px;">Daler-Rowney</td>
			<td style="width:121px;">038372016954</td>
			<td>For transferring embryos</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:223px;">Paper towels, Kleenex C-fold paper towels, white</td>
			<td style="width:195px;">Kimberly-Clark</td>
			<td style="width:121px;">884266344845</td>
			<td>For blotting cell strainer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Pasteur pipette, 5 3/4 in</td>
			<td style="width:195px;">Fisher Scientific</td>
			<td style="width:121px;">1367820A</td>
			<td>For covering embryos with oil</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Petri dish, glass, 100 x 20 mm</td>
			<td style="width:195px;">Corning</td>
			<td style="width:121px;">3160102</td>
			<td>For humid incubation chamber</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Petri dish, plastic, 60 x 15 mm</td>
			<td style="width:195px;">VWR</td>
			<td style="width:121px;">25384092</td>
			<td>For apple juice plates</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:223px;">Pipette, Eppendorf Reference 0.5-10 &#956;L</td>
			<td style="width:195px;">Eppendorf</td>
			<td style="width:121px;">2231000604</td>
			<td>For loading the microneedle</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Pipette tip, xTIP4 250 &#956;L</td>
			<td style="width:195px;">Biotix</td>
			<td style="width:121px;">63300006</td>
			<td>For adding embryo glue to coverslip</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Razor blade</td>
			<td style="width:195px;">VWR</td>
			<td style="width:121px;">55411050</td>
			<td>For cutting agar wedge, tape, pipette tips</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:223px;">Rhodamine-conjugated globular actin, human platelet (non-muscle; 4x10 &#956;g)</td>
			<td style="width:195px;">Cytoskeleton, Inc.</td>
			<td style="width:121px;">APHR-A</td>
			<td>G-actin^Red</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:223px;">Scintillation vial, 20 mL Glass borosillicate with polyethylene liner and urea caps</td>
			<td style="width:195px;">Fisher Scientific</td>
			<td style="width:121px;">033377</td>
			<td>For making embryo glue</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Screw top jar, 16 oz</td>
			<td style="width:195px;">Nalgene</td>
			<td style="width:121px;">000194414195</td>
			<td>For desiccating embryos</td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:223px;">Stage micrometer</td>
			<td style="width:195px;">Electron Microscopy Sciences</td>
			<td style="width:121px;">602104PG</td>
			<td>For calibrating volume of G-actin injection</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Sucrose</td>
			<td style="width:195px;">Millipore-Sigma</td>
			<td style="width:121px;">840971KG</td>
			<td>Component of apple juice plates</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:223px;">Trizma base</td>
			<td style="width:195px;">Millipore-Sigma</td>
			<td style="width:121px;">T15031KG</td>
			<td>Component of G buffer</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:223px;">Yeast, Lesaffre Yeast Corporation Yeast, Red Star Active Dry, 32 oz</td>
			<td style="width:195px;">Lesaffre Yeast Corporation</td>
			<td style="width:121px;">117929157002</td>
			<td>Component of yeast paste</td>
		</tr>
	</tbody>
</table>

imaging intranuclear actin rods in live heat stressed drosophila embryos

The purpose of this protocol is to visualize intranuclear actin rods that assemble in live Drosophila melanogaster embryos following heat stress. Actin rods are a hallmark of a conserved, inducible Actin Stress Response (ASR) that accompanies human pathologies, including neurodegenerative disease. Previously, we showed that the ASR contributes to morphogenesis failures and reduced viability of developing embryos. This protocol allows the continued study of mechanisms underlying actin rod assembly and the ASR in a model system that is highly amenable to imaging, genetics and biochemistry. Embryos are collected and mounted on a coverslip to prepare them for injection. Rhodamine-conjugated globular actin (G-actinRed) is diluted and loaded into a microneedle. A single injection is made into the center of each embryo. After injection, embryos are incubated at elevated temperature and intranuclear actin rods are then visualized by confocal microscopy. Fluorescence recovery after photobleaching (FRAP) experiments may be performed on the actin rods; and other actin-rich structures in the cytoplasm can also be imaged. We find that G-actinRed polymerizes like endogenous G-actin and does not, on its own, interfere with normal embryo development. One limitation of this protocol is that care must be taken during injection to avoid serious injury to the embryo. However, with practice, injecting G-actinRed into Drosophila embryos is a fast and reliable way to visualize actin rods and can easily be used with flies of any genotype or with the introduction of other cellular stresses, including hypoxia and oxidative stress.

A schematic workflow of embryo handling is depicted in Figure 1, and a timetable for a typical experiment is presented in Table 1. An estimate for a good experimental outcome is that for every 10 embryos injected, at least half of the embryos viewed will be at the correct developmental stage, undamaged, and exhibit a robust ASR with heat stress at 32 &#176;C. This ASR will be evidenced by the assembly of intranuclear actin rods as shown in the representative surface view ima...

Watch this Scientific Journal Video about Imaging Intranuclear Actin Rods in Live Heat Stressed Drosophila Embryos at JoVE.com

Imaging Intranuclear Actin Rods in Live Heat Stressed Drosophila Embryos

The goal of this protocol is to inject Rhodamine-conjugated globular actin into Drosophila embryos and image intranuclear actin rod assembly following heat stress.

Imaging Intranuclear Actin Rods in Live Heat Stressed Drosophila Embryos

The purpose of this protocol is to visualize intranuclear actin rods that assemble in live Drosophila melanogaster embryos following heat stress. Actin ...

imaging-intranuclear-actin-rods-live-heat-stressed-drosophila

Research

JoVE Journal

Developmental Biology

3.4K Views.  Baylor College of Medicine. The goal of this protocol is to inject Rhodamine-conjugated globular actin into Drosophila embryos and image intranuclear actin rod assembly following heat stress.

Video: Imaging Intranuclear Actin Rods in Live Heat Stressed Drosophila Embryos

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 ...

Ploidy Manipulation of Zebrafish Embryos with Heat Shock 2 Treatment

Manipulation of ploidy allows for useful transformations, such as diploids to tetraploids, or haploids to diploids. In the zebrafish Danio rerio, specifically the generation of homozygous gynogenetic diploids is useful in genetic analysis because it allows the direct production of homozygotes from a single heterozygous mother. This article describes a modified protocol for ploidy duplication based on a heat pulse during the first cell cycle, Heat Shock 2 (HS2). Through inhibition of centriole duplication, this method results in a precise cell division stall during the second cell cycle. The precise one-cycle division stall, coupled to unaffected DNA duplication, results in whole genome duplication. Protocols associated with this method include egg and sperm collection, UV treatment of sperm, in vitro fertilization and heat pulse to cause a one-cell cycle division delay and ploidy duplication. A modified version of this protocol could be applied to induce ploidy changes in other animal species.

A modified protocol for ploidy manipulation uses a heat shock to induce a one-cycle stall in cytokinesis in the early embryo. This protocol is demonstrated in the zebrafish but may be applicable to other species.

Manipulation of ploidy allows for useful transformations, such as diploids to tetraploids, or haploids to diploids. In the zebrafish Danio rerio, ...

Biosensing Motor Neuron Membrane Potential in Live Zebrafish Embryos

The protocols described here are designed to allow researchers to study cell communication without altering the integrity of the environment in which the cells are located. Specifically, they have been developed to analyze the electrical activity of excitable cells, such as spinal neurons. In such a scenario, it is crucial to preserve the integrity of the spinal cell, but it is also important to preserve the anatomy and physiological shape of the systems involved. Indeed, the comprehension of the manner in which the nervous system-and other complex systems-works must be based on a systemic approach. For this reason, the live zebrafish embryo was chosen as a model system, and the spinal neuron membrane voltage changes were evaluated without interfering with the physiological conditions of the embryos. 
Here, an approach combining the employment of zebrafish embryos with a FRET-based biosensor is described. Zebrafish embryos are characterized by a very simplified nervous system and are particularly suited for imaging applications thanks to their transparency, allowing for the employment of fluorescence-based voltage indicators at the plasma membrane during zebrafish development. The synergy between these two components makes it possible to analyze the electrical activity of the cells in intact living organisms, without perturbing the physiological state. Finally, this non-invasive approach can co-exist with other analyses (e.g., spontaneous movement recordings, as shown here).

Protocols described here allow for the study of the electrical properties of excitable cells in the most non-invasive physiological conditions by employing zebrafish embryos in an in vivo system together with a fluorescence resonance energy transfer (FRET)-based genetically encoded voltage indicator (GEVI) selectively expressed in the cell type of interest.

The protocols described here are designed to allow researchers to study cell communication without altering the integrity of the environment in which the ...

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 Vitro Ovule Cultivation for Live-cell Imaging of Zygote Polarization and Embryo Patterning in Arabidopsis thaliana

In most flowering plants, the zygote and embryo are hidden deep in the mother tissue, and thus it has long been a mystery of how they develop dynamically; for example, how the zygote polarizes to establish the body axis and how the embryo specifies various cell fates during organ formation. This manuscript describes an in vitro ovule culture method to perform live-cell imaging of developing zygotes and embryos of Arabidopsis thaliana. The optimized cultivation medium allows zygotes or early embryos to grow into fertile plants. By combining it with a poly(dimethylsiloxane) (PDMS) micropillar array device, the ovule is held in the liquid medium in the same position. This fixation is crucial to observe the same ovule under a microscope for several days from the zygotic division to the late embryo stage. The resulting live-cell imaging can be used to monitor the real-time dynamics of zygote polarization, such as nuclear migration and cytoskeleton rearrangement, and also the cell division timing and cell fate specification during embryo patterning. Furthermore, this ovule cultivation system can be combined with inhibitor treatments to analyze the effects of various factors on embryo development, and with optical manipulations such as laser disruption to examine the role of cell-cell communication.

In Vitro Ovule Cultivation for Live-cell Imaging of Zygote Polarization and Embryo Patterning in Arabidopsis thaliana

This manuscript describes an in vitro ovule cultivation method that enables live-cell imaging of Arabidopsis zygotes and embryos. This method is utilized to visualize the intracellular dynamics during zygote polarization and the cell fate specification in developing embryos.

In most flowering plants, the zygote and embryo are hidden deep in the mother tissue, and thus it has long been a mystery of how they develop dynamically; ...

Live Imaging of Mouse Secondary Palate Fusion

The fusion of the secondary palatal shelves to form the intact secondary palate is a key process in mammalian development and its disruption can lead to cleft secondary palate, a common congenital anomaly in humans. Secondary palate fusion has been extensively studied leading to several proposed cellular mechanisms that may mediate this process. However, these studies have been mostly performed on fixed embryonic tissues at progressive timepoints during development or in fixed explant cultures analyzed at static timepoints. Static analysis is limited for the analysis of dynamic morphogenetic processes such a palate fusion and what types of dynamic cellular behaviors mediate palatal fusion is incompletely understood. Here we describe a protocol for live imaging of ex vivo secondary palate fusion in mouse embryos. To examine cellular behaviors of palate fusion, epithelial-specific Keratin14-cre was used to label palate epithelial cells in ROSA26-mTmGflox reporter embryos. To visualize filamentous actin, Lifeact-mRFPruby reporter mice were used. Live imaging of secondary palate fusion was performed by dissecting recently-adhered secondary palatal shelves of embryonic day (E) 14.5 stage embryos and culturing in agarose-containing media on a glass bottom dish to enable imaging with an inverted confocal microscope. Using this method, we have detected a variety of novel cellular behaviors during secondary palate fusion. An appreciation of how distinct cell behaviors are coordinated in space and time greatly contributes to our understanding of this dynamic morphogenetic process. This protocol can be applied to mutant mouse lines, or cultures treated with pharmacological inhibitors to further advance understanding of how secondary palate fusion is controlled.

Here, we present a protocol for live imaging of mouse secondary palate fusion using confocal microscopy. This protocol can be used in combination with a variety of fluorescent reporter mouse lines, and with pathway inhibitors for mechanistic insight. This protocol can be adapted for live imaging in other developmental systems.

The fusion of the secondary palatal shelves to form the intact secondary palate is a key process in mammalian development and its disruption can lead to ...

Methods for Imaging Intracellular pH of the Follicle Stem Cell Lineage in Live Drosophila Ovarian Tissue

Changes in intracellular pH (pHi) play important roles in the regulation of many cellular functions, including metabolism, proliferation, and differentiation. Typically, pHi dynamics are determined in cultured cells, which are amenable to measuring and experimentally manipulating pHi. However, the recent development of new tools and methodologies has made it possible to study pHi dynamics within intact, live tissue. For Drosophila research, one important development was the generation of a transgenic line carrying a pHi biosensor, mCherry::pHluorin. Here, we describe a protocol that we routinely use for imaging live Drosophila ovarioles to measure pHi in the epithelial follicle stem cell (FSC) lineage in mCherry::pHluorin transgenic wild type lines; however, the methods described here can be easily adapted for other tissues, including the wing discs and eye epithelium. We describe techniques for expressing mCherry::pHluorin in the FSC lineage, maintaining ovarian tissue during live imaging, and acquiring and analyzing images to obtain pHi values.

Methods for Imaging Intracellular pH of the Follicle Stem Cell Lineage in Live Drosophila Ovarian Tissue

We provide a protocol for imaging intracellular pH of an epithelial stem cell lineage in live Drosophila ovarian tissue. We describe methods to generate transgenic flies expressing a pH biosensor, mCherry::pHluorin, image the biosensor using quantitative fluorescence imaging, generate standard curves, and convert fluorescence intensity values to pH values.

Changes in intracellular pH (pHi) play important roles in the regulation of many cellular functions, including metabolism, proliferation, and ...

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 ...

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, ...

Applications of Immobilization of Drosophila Tissues with Fibrin Clots for Live Imaging

Drosophila is an important model system to study a vast range of biological questions. Various organs and tissues from different developmental stages of the fly such as imaginal discs, the larval brain or egg chambers of adult females or the adult intestine can be extracted and kept in culture for imaging with time-lapse microscopy, providing valuable insights into cell and developmental biology. Here, we describe in detail our current protocol for the dissection of Drosophila larval brains, and then present our current approach for immobilizing and orienting larval brains and other tissues on a glass coverslip using Fibrin clots. This immobilization method only requires the addition of Fibrinogen and Thrombin to the culture medium. It is suitable for high-resolution time lapse imaging on inverted microscopes of multiple samples in the same culture dish, minimizes the lateral drifting frequently caused by movements of the microscope stage in multi-point visiting microscopy and allows for the addition and removal of reagents during the course of imaging. We also present custom-made macros that we routinely use to correct for drifting and to extract and process specific quantitative information from time-lapse analysis.

Applications of Immobilization of Drosophila Tissues with Fibrin Clots for Live Imaging

This protocol describes applications of sample immobilization using Fibrin clots, limiting drifting, and allowing the addition and washout of reagents during live imaging. Samples are transferred to a drop of Fibrinogen containing culture medium on the surface of a coverslip, after which polymerization is induced by adding thrombin.

Drosophila is an important model system to study a vast range of biological questions. Various organs and tissues from different developmental stages of ...