Name: imaging intranuclear actin rods in live heat stressed drosophila embryos
Uploaded: 2020-05-15T14:30:00
Description: Watch this Scientific Journal Video about Imaging Intranuclear Actin Rods in Live Heat Stressed Drosophila Embryos at JoVE.com

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 numb...

<ol>
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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. 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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. 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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. 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(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. 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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 ...

Our protocol is significant because it uses the well-established technique of microinjection in Drosophila embryos to allow new research on the actin stress response and accompanying actin rod assembly. The main advantage of this technique is that we can study the actin stress response under a variety of contexts, such as a mutant screen or under different stress conditions. An individual who has never performed this technique before may struggle with handling the embryos and performing the microinjection.We recommend practicing these steps until the user feels comfortable. Visual demonstration of this method is critical because the steps of embryo handling, positioning, and mounting for both microinjection and imaging might not be clear from written instructions alone. Prepare embryo collection cups and apple juice agar plates according to manuscript directions.To promote the most generous egg laying, set up collection cups with flies two days prior to the experiment. Add at least 100 female and 50 male flies to each collection cup, then cover it with an apple juice plate. Prepare a working solution of G-actin red and store it on ice until it is loaded into the microneedle.Allow flies to lay embryos for 30 minutes on the apple juice plates with yeast paste at 18 degrees Celsius. While the flies are laying, cut out a four by one centimeter rectangular wedge of apple juice agar with a razor blade and place it on a 25 by 75 millimeter glass slide. Harvest the plate from the collection and dechorionate the embryos by pouring fresh bleach solution onto the plate and swirling it for one minute.Dampen the bristles of a paintbrush with distilled water, then use it to transfer dechorionated and washed embryos from the collection basket onto the prepared apple juice agar wedge on the glass slide. Use a pair of fine tip tweezers or a dissecting needle to arrange 10 embryos in a straight line along the long axis of the rectangular agar wedge. Arrange the embryos head to tail such that their dorsal side is facing the researcher.Cut half a centimeter off the end of a P200 pipette tip with a razor blade and dip it into the embryo glue. Generously coat a five millimeter region along the long edge of a 24 by 50 millimeter rectangular coverslip and let it dry glue side up. Once the embryo glue has dried, gently place the coverslip glue side down on top of the row of aligned embryos on the agar, leaving two to three millimeters of space between the edge of the coverslip and the row of embryos.Flip the coverslip over so that the embryos are facing up. They should be stuck in a line along one long edge of the coverslip with their ventral region facing the closest edge. Place the coverslip on top of 150 grams of fresh blue desiccant in a 16 ounce screw top jar and tightly screw on the lid.Desiccate the embryos for 8 to 10 minutes, then remove the coverslip from the desiccant jar and tape each short side of the coverslip to a microscope slide embryo side up. Add two to three drops of hollow carbon 27 oil with a Pasteur pipette to cover the aligned embryos and protect them from further dehydration. While the embryos are desiccating, back load the previously prepared G-actin red supernatant into the microneedle with a microloader tip.Attach the microneedle to the needle holder and tighten the screw. Place the slide with the mounted embryos onto the microscope stage and use the microneedle controls to bring the needle into the same focal plane as the embryos. Insert the microneedle into the embryo so that it hits the embryo in the middle of its ventral region at the embryo equator.When the microneedle tip is visible inside the middle of the embryo, trigger the injection. After the injection, slowly remove the microneedle. Move the stage and perform the injection on the other embryos.After all embryos have been injected, place the slide with the embryos in a humid incubation chamber and close the lid. Remove the slide with the injected embryos from the humid incubation chamber. Working quickly, gently pry off the double-sided tape pieces that were used to adhere the coverslip to the slide.Stick two 2.5 centimeter long pieces of double-sided tape together and cut the tape in half lengthwise to make two strips. Stick 2/3 of the length of each tape strip onto the first coverslip, blanking each side of the embryos. Leave 1/3 of the tape strips hanging off the edge of the first coverslip where the embryos are stuck.Gently place a second rectangular coverslip on top of the tape strips to sandwich the embryos between the coverslips, aligning the 25 millimeter edges but keeping the 50 millimeter edges offset from one another by one centimeter. Confirm that the heated stage is at the appropriate temperature. And if using an inverted microscope, add immersion liquid onto the selected objective lens.Place the coverslip sandwich onto the stage carefully, making sure that the new imaging surface is the one touching the immersion liquid. Focus on an embryo that is in cellularization, then switch to the laser acquisition mode on the confocal microscope and adjust laser power and gain, frame size, tiling, and projection settings as desired. Take surface view images through the focal planes of the embryo's nuclei to find intranuclear actin rods.Rods should appear in multiple orientations as bright streaks or dots inside the comparatively dark nuclei. The actin stress response and heat-stressed embryos is evident by the assembly of intranuclear actin rods. Actin rods appear in different orientations inside the nuclei and can be imaged through several focal planes.In comparison, control embryos incubated at 18 degrees Celsius do not display actin rods. The percent nuclei containing rods can be quantified and FRAP experiments can be performed on the rods. An example of a fluorescence recovery plot for a bleached versus unbleached region of an actin rod is shown here.When attempting this procedure, it is important to remember the actin rod formation is temperature dependent. For the steps following the microinjection, it is crucial to keep embryos at the desired incubation temperature. After microinjection, the researcher can perform FRAP to confirm the lack of F-actin turnover in the actin rods or to quantify changes in F-actin turnover occurring in other actin-rich structures.

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

Research

JoVE Journal

Developmental Biology

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 ...

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 ...

Optogenetic Inhibition of Rho1-Mediated Actomyosin Contractility in Drosophila

Optogenetic Inhibition of Rho1-Mediated Actomyosin Contractility Coupled with Measurement of Epithelial Tension in Drosophila Embryos

Contractile forces generated by actin and non-muscle myosin II ("actomyosin contractility") are critical for morphological changes of cells and tissues at multiple length scales, such as cell division, cell migration, epithelial folding, and branching morphogenesis. An in-depth understanding of the role of actomyosin contractility in morphogenesis requires approaches that allow the rapid inactivation of actomyosin, which is difficult to achieve using conventional genetic or pharmacological approaches. The presented protocol demonstrates the use of a CRY2-CIBN based optogenetic dimerization system, Opto-Rho1DN, to inhibit actomyosin contractility in Drosophila embryos with precise temporal and spatial controls. In this system, CRY2 is fused to the dominant negative form of Rho1 (Rho1DN), whereas CIBN is anchored to the plasma membrane. Blue light-mediated dimerization of CRY2 and CIBN results in rapid translocation of Rho1DN from the cytoplasm to the plasma membrane, where it inactivates actomyosin by inhibiting endogenous Rho1. In addition, this article presents a detailed protocol for coupling Opto-Rho1DN-mediated inactivation of actomyosin with laser ablation to investigate the role of actomyosin in generating epithelial tension during Drosophila ventral furrow formation. This protocol can be applied to many other morphological processes that involve actomyosin contractility in Drosophila embryos with minimal modifications. Overall, this optogenetic tool is a powerful approach to dissect the function of actomyosin contractility in controlling tissue mechanics during dynamic tissue remodeling.

Author Spotlight: Optogenetic Inhibition of Rho1-Mediated Actomyosin Contractility Coupled with Measurement of Epithelial Tension in Drosophila Embryos  

Actomyosin contractility plays an important role in cell and tissue morphogenesis. However, it is challenging to manipulate actomyosin contractility in vivo acutely. This protocol describes an optogenetic system that rapidly inhibits Rho1-mediated actomyosin contractility in Drosophila embryos, revealing the immediate loss of epithelial tension after the inactivation of actomyosin in vivo.

Contractile forces generated by actin and non-muscle myosin II ("actomyosin contractility") are critical for morphological changes of cells and tissues at ...