Name: analyzing synaptic modulation of drosophila melanogaster photoreceptors after exposure to prolonged light
Uploaded: 2017-02-10T14:00:00
Description: Watch this Scientific Journal Video about Analyzing Synaptic Modulation of Drosophila melanogaster Photoreceptors after Exposure to Prolonged Light at JoVE.com

We are grateful to T. St&#252;rner for helpful corrections, discussions and comments on the manuscript; S.L. Zipursky for providing fly stocks; M Sch&#246;lling for performing image processing. Part of the image analysis was performed at A. Kakita&#39;s lab. This work was supported by Alexander von Humboldt Foundation and JSPS Fellowships for Research Abroad (A.S.), JSPS Fellows (S.H.-S.), Grant-In- Aid for Start-up (24800024), on Innovative Areas (25110713), Mochida, Takeda, Inamori, Daiichi-Sankyo, Toray Foundations (T.S.), DZNE core funding (G.T.) and DZNE Light Microscopy Facility (C.M.).

The experimental procedures described in this protocol involve exclusively work with Drosophila and are not subjected to animal welfare laws in Germany and Japan.
1. Light Exposure Conditions
<ol>
	<li>Prepare flies that carry sensless-flippase (sens-flp) and bruchpilot-FRT-STOP-FRT-gfp (brp-FSF-gfp)15 for visualizing Brp-GFP in photoreceptor R8 neurons (R8s). The genomic locus encoding brp within a Bacterial Artif...

<ol>
	<li>Alabi, A. A., Tsien, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synaptic+Vesicle+Pools+and+Dynamics.">Synaptic Vesicle Pools and Dynamics.</a> Cold Spring Harbor Perspectives in Biology. 4 (8), (2012).</li><li>Couteaux, R., Pecot-Dechavassine, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=[Synaptic+vesicles+and+pouches+at+the+level+of+&amp;#34;active+zones&amp;#34;+of+the+neuromuscular+junction].">[Synaptic vesicles and pouches at the level of &amp;#34;active zones&amp;#34; of the neuromuscular junction].</a> C R Acad Sci Hebd Seances Acad Sci D. 271 (25), 2346-2349 (1970).</li><li>Schoch, S., Gundelfinger, E. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+organization+of+the+presynaptic+active+zone.">Molecular organization of the presynaptic active zone.</a> Cell and Tissue Research. 326 (2), 379-391 (2006).</li><li>Sudhof, T. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Presynaptic+Active+Zone.">The Presynaptic Active Zone.</a> Neuron. 75 (1), 11-25 (2012).</li><li>Owald, D., Sigrist, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assembling+the+presynaptic+active+zone.">Assembling the presynaptic active zone.</a> Curr Opin Neurobiol. 19 (3), 311-318 (2009).</li><li>Lazarevic, V., Schone, C., Heine, M., Gundelfinger, E. D., Fejtova, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extensive+remodeling+of+the+presynaptic+cytomatrix+upon+homeostatic+adaptation+to+network+activity+silencing.">Extensive remodeling of the presynaptic cytomatrix upon homeostatic adaptation to network activity silencing.</a> J Neurosci. 31 (28), 10189-10200 (2011).</li><li>Matz, J., Gilyan, A., Kolar, A., McCarvill, T., Krueger, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+structural+alterations+of+the+active+zone+lead+to+sustained+changes+in+neurotransmitter+release.">Rapid structural alterations of the active zone lead to sustained changes in neurotransmitter release.</a> Proc Natl Acad Sci U S A. 107 (19), 8836-8841 (2010).</li><li>Spangler, S. 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=Liprin-alpha2+promotes+the+presynaptic+recruitment+and+turnover+of+RIM1/CASK+to+facilitate+synaptic+transmission.">Liprin-alpha2 promotes the presynaptic recruitment and turnover of RIM1/CASK to facilitate synaptic transmission.</a> J Cell Biol. 201 (6), 915-928 (2013).</li><li>Sugie, 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=Molecular+Remodeling+of+the+Presynaptic+Active+Zone+of+Drosophila+Photoreceptors+via+Activity-Dependent+Feedback.">Molecular Remodeling of the Presynaptic Active Zone of Drosophila Photoreceptors via Activity-Dependent Feedback.</a> Neuron. 86 (3), 711-725 (2015).</li><li>Sigrist, S. J., Schmitz, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+and+functional+plasticity+of+the+cytoplasmic+active+zone.">Structural and functional plasticity of the cytoplasmic active zone.</a> Curr Opin Neurobiol. 21 (1), 144-150 (2011).</li><li>Kittel, R. J., 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=Active+zone+assembly+and+synaptic+release.">Active zone assembly and synaptic release.</a> Biochem Soc Trans. 34 (Pt 5), 939-941 (2006).</li><li>Kittel, R. J., 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=Bruchpilot+promotes+active+zone+assembly,+Ca2++channel+clustering,+and+vesicle+release.">Bruchpilot promotes active zone assembly, Ca2+ channel clustering, and vesicle release.</a> Science. 312 (5776), 1051-1054 (2006).</li><li>Hallermann, 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=Naked+dense+bodies+provoke+depression.">Naked dense bodies provoke depression.</a> J Neurosci. 30 (43), 14340-14345 (2010).</li><li>Wagh, D. 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=Bruchpilot,+a+protein+with+homology+to+ELKS/CAST,+is+required+for+structural+integrity+and+function+of+synaptic+active+zones+in+Drosophila.">Bruchpilot, a protein with homology to ELKS/CAST, is required for structural integrity and function of synaptic active zones in Drosophila.</a> Neuron. 49 (6), 833-844 (2006).</li><li>Chen, Y., 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=Cell-type-specific+labeling+of+synapses+in+vivo+through+synaptic+tagging+with+recombination.">Cell-type-specific labeling of synapses in vivo through synaptic tagging with recombination.</a> Neuron. 81 (2), 280-293 (2014).</li><li>Andlauer, T. F., Sigrist, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+analysis+of+Drosophila+larval+neuromuscular+junction+morphology.">Quantitative analysis of Drosophila larval neuromuscular junction morphology.</a> Cold Spring Harb Protoc. 2012 (4), 490-493 (2012).</li><li>Ippolito, D. M., Eroglu, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantifying+synapses:+an+immunocytochemistry-based+assay+to+quantify+synapse+number.">Quantifying synapses: an immunocytochemistry-based assay to quantify synapse number.</a> J Vis Exp. (45), (2010).</li><li>Schmitz, S. K., 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=Automated+analysis+of+neuronal+morphology,+synapse+number+and+synaptic+recruitment.">Automated analysis of neuronal morphology, synapse number and synaptic recruitment.</a> J Neurosci Methods. 195 (2), 185-193 (2011).</li><li>Danielson, E., Lee, S. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SynPAnal:+software+for+rapid+quantification+of+the+density+and+intensity+of+protein+puncta+from+fluorescence+microscopy+images+of+neurons.">SynPAnal: software for rapid quantification of the density and intensity of protein puncta from fluorescence microscopy images of neurons.</a> PLoS One. 9 (12), e115298 (2014).</li><li>Sanders, J., Singh, A., Sterne, G., Ye, B., Zhou, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Learning-guided+automatic+three+dimensional+synapse+quantification+for+drosophila+neurons.">Learning-guided automatic three dimensional synapse quantification for drosophila neurons.</a> BMC Bioinformatics. 16, 177 (2015).</li><li>Peng, H., Ruan, Z., Atasoy, D., Sternson, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Automatic+reconstruction+of+3D+neuron+structures+using+a+graph-augmented+deformable+model.">Automatic reconstruction of 3D neuron structures using a graph-augmented deformable model.</a> Bioinformatics. 26 (12), i38-i46 (2010).</li><li>Sturt, B. L., Bamber, B. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Automated+quantification+of+synaptic+fluorescence+in+C.+elegans.">Automated quantification of synaptic fluorescence in C. elegans.</a> J Vis Exp. (66), (2012).</li><li>Kremer, M. C., 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=Structural+long-term+changes+at+mushroom+body+input+synapses.">Structural long-term changes at mushroom body input synapses.</a> Curr Biol. 20 (21), 1938-1944 (2010).</li><li>Mosca, T. J., Luo, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synaptic+organization+of+the+Drosophila+antennal+lobe+and+its+regulation+by+the+Teneurins.">Synaptic organization of the Drosophila antennal lobe and its regulation by the Teneurins.</a> Elife. 3, e03726 (2014).</li><li>Wu, J. S., Luo, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+protocol+for+dissecting+Drosophila+melanogaster+brains+for+live+imaging+or+immunostaining.">A protocol for dissecting Drosophila melanogaster brains for live imaging or immunostaining.</a> Nat Protoc. 1 (4), 2110-2115 (2006).</li><li>Fischbach, K. F., Dittrich, A. P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Optic+Lobe+of+Drosophila-Melanogaster+.1+A+Golgi+Analysis+of+Wild-Type+Structure.">The Optic Lobe of Drosophila-Melanogaster .1 A Golgi Analysis of Wild-Type Structure.</a> Cell and Tissue Research. 258 (3), 441-475 (1989).</li><li>Berger-Muller, 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=Assessing+the+role+of+cell-surface+molecules+in+central+synaptogenesis+in+the+Drosophila+visual+system.">Assessing the role of cell-surface molecules in central synaptogenesis in the Drosophila visual system.</a> PLoS One. 8 (12), e83732 (2013).</li><li>Fouquet, W., 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=Maturation+of+active+zone+assembly+by+Drosophila+Bruchpilot.">Maturation of active zone assembly by Drosophila Bruchpilot.</a> J Cell Biol. 186 (1), 129-145 (2009).</li><li>Ke, M. T., 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=Super-Resolution+Mapping+of+Neuronal+Circuitry+With+an+Index-Optimized+Clearing+Agent.">Super-Resolution Mapping of Neuronal Circuitry With an Index-Optimized Clearing Agent.</a> Cell Rep. 14 (11), 2718-2732 (2016).</li><li>Ehmann, N., 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=Quantitative+super-resolution+imaging+of+Bruchpilot+distinguishes+active+zone+states.">Quantitative super-resolution imaging of Bruchpilot distinguishes active zone states.</a> Nat Commun. 5, 4650 (2014).</li></ol>

In this study, we showed how to prepare the light conditions to expose flies to an equal light intensity. We quantified not only the number of a synaptic marker puncta but could also spatially resolve the density of synapses along axons and measure the delocalization level of the marker protein in cytoplasmic areas. These three assessments allow us to evaluate the details of synaptic dynamics at single neuron level in different environmental conditions. Our protocol can be adapted to different synaptic proteins but also ...

The modulation of synaptic function contributes to the remarkable ability of the nervous system to precisely respond or adapt to changing environmental stimuli. Adjusting the presynaptic vesicle release probability is one way of controlling synaptic strength1. Synaptic vesicle release takes place at the Active Zone (AZ), a specialized region of the presynaptic membrane2. The AZ is characterized by a cassette of specific proteins3,4. Most proteins contributing to AZ assembly are highly conserved in nematodes, insects and mammals5. Recent studies suggest that the level of neuronal activity regulates the molecular composition of the AZ, which in turn contributes to the regulation of the functional output both in vitro and in vivo6,7,8. We previously found that photoreceptor AZs undergo molecular remodeling in Drosophila after prolonged exposure to natural ambient light9. In this condition, we observed that the number of Bruchpilot (Brp)-positive AZs was reduced in the photoreceptor axons.
The Brp/CAST/ELKS family proteins are fundamental building blocks of AZs in vertebrate and invertebrate synapses10. In Drosophila brp mutants, evoked vesicle release is suppressed11,12. The 17 C-terminal amino acid residues of Brp are essential for synaptic vesicle clustering at the Drosophila Neuromuscular Junction (NMJ)13,14. These studies demonstrated the central role of this molecule in AZ organization and function. With a recently developed genetic tool, Synaptic Tagging with Recombination (STaR), Brp can be observed in vivo in specific cell types, at endogenous expression levels and at a single synapse resolution15. This tool makes it feasible to evaluate the endogenous dynamics of synapses quantitatively in the complex central nervous system.
There have been several studies including synapse quantifications based on data obtained from confocal microscopy. Synaptic alterations have been evaluated by measuring the length, the area, the volume, the density and counting the number based on sophisticated software applications. For instance, the freeware ImageJ provides a quantification method for total synaptic area and synaptic density measures at the Drosophila NMJ16. The number of colocalization sites of pre and postsynaptic markers have been quantified using the plugin &#34;Puncta Analyzer&#34; available on the ImageJ software platform17. Alternatively, a multi-paradigm numerical computing environment based program, Synapse Detector (SynD), can automatically trace dendrites of neurons labeled with a fluorescent marker, and then quantifies the synaptic protein levels as a function of distance from the cell body18. The software Synaptic Puncta Analysis (SynPAnal), has been designed for the rapid analysis of 2D images of neurons acquired from confocal or fluorescent microscopy. The primary function of this software is the automatic and rapid quantification of density and intensity of protein puncta19. Recently, an automatic learning-based synapse detection algorithm has been generated for quantification of synaptic number in 3D20, taking advantage of the 3D Visualization-Assisted Analysis (Vaa3D) software21.
Commercial image analysis software are also powerful tools for synaptic quantifications. For instance, the fluorescently labeled neurotransmitter receptors or a presynaptic AZ component have been quantified in three dimensions with single-synapse resolution in C. elegans22 or the Drosophila olfactory system23,24, allowing hundreds of synapses to be rapidly characterized within a single sample.
Here, we present a method by a customized image analysis software plug-in implemented in a multi-paradigm numerical computing environment that allows to analyze semi-automatically multiple aspects of AZs, including their number, distribution and the level of enrichment of molecular components to the AZ. Thus, this complex analysis allowed us to evaluate the dynamics of synaptic components in axon terminals under different environmental conditions. We investigated the effect of light exposure on the output synapses of adult fly photoreceptors. The procedure is performed in three steps: 1) preparation for light exposure, 2) dissection, immunohistochemistry and confocal imaging, and 3) image analysis.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Vial</td>
			<td>Hightech, Japan</td>
			<td>MKC-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Plug</td>
			<td>Thermo Fisher Sciehtific, USA</td>
			<td>AS-275</td>
			<td></td>
		</tr>
		<tr>
			<td>Customized transparent rack made of acrylic resin&#160;</td>
			<td>Shin-Shin Corporation, Japan</td>
			<td></td>
			<td>a height of 41 cm, a base of 21 cm, a thickness of 4 cm and a height of 13 cm for each step</td>
		</tr>
		<tr>
			<td>Cool incubator</td>
			<td>MITSUBISHI ELECTRIC, Japan</td>
			<td>CN-40A</td>
			<td></td>
		</tr>
		<tr>
			<td>LED panel</td>
			<td>MISUMI, Japan</td>
			<td>LEDXC170-W</td>
			<td></td>
		</tr>
		<tr>
			<td>Digital light meter</td>
			<td>CEM</td>
			<td>DT-1301</td>
			<td></td>
		</tr>
		<tr>
			<td>Fly pad</td>
			<td>Tokken, Japan</td>
			<td>TK-HA03-S</td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dish (35 x 10 mm)</td>
			<td>Greiner Bio-One International, Germany</td>
			<td>627102</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS tablet</td>
			<td>Takara, Japan</td>
			<td>T900</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Wako, Japan</td>
			<td>160-24751</td>
			<td></td>
		</tr>
		<tr>
			<td>Dumont #5 Forceps</td>
			<td>Fine Science Tools</td>
			<td>11251-20</td>
			<td></td>
		</tr>
		<tr>
			<td>1.5 ml tube</td>
			<td>Sarstedt, Germany</td>
			<td>A. 152X</td>
			<td></td>
		</tr>
		<tr>
			<td>Formaldehyde 16%</td>
			<td>NEM, Japan</td>
			<td>3152</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipetman P-200</td>
			<td>Gilson</td>
			<td>F123601&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipetman P-20</td>
			<td>Gilson</td>
			<td>F123600</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipetman P-2</td>
			<td>Gilson</td>
			<td>F144801</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-chaoptin antibody</td>
			<td>DSHB</td>
			<td>24B10</td>
			<td></td>
		</tr>
		<tr>
			<td>Alexa568-conjugated anti-mouse antibody</td>
			<td>Life Technologies</td>
			<td>A-11031</td>
			<td></td>
		</tr>
		<tr>
			<td>VECTASHIELD Mounting Medium</td>
			<td>Vector Laboratories, Inc.</td>
			<td>H-1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope slide (76 x 26 mm)</td>
			<td>Thermo Fisher Scientific Gerhard Menzel B.V. &#38; Co. KG, Germany</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Coverslip (18 x 18 mm, 0.17 mm)</td>
			<td>Zeiss, Germany</td>
			<td>474030-9000-000</td>
			<td></td>
		</tr>
		<tr>
			<td>Industrial Microscopes</td>
			<td>Olympus, Japan</td>
			<td>SZ61-C-SET</td>
			<td></td>
		</tr>
		<tr>
			<td>Stereo Microscope Lighting</td>
			<td>Olympus, Japan</td>
			<td>KL 1600 LED</td>
			<td></td>
		</tr>
		<tr>
			<td>confocal microscopy</td>
			<td>Zeiss, Germany</td>
			<td>LSM780</td>
			<td></td>
		</tr>
		<tr>
			<td>Imaris</td>
			<td>Bitplane, Switzerland</td>
			<td></td>
			<td>Version 7.6.4 or above</td>
		</tr>
		<tr>
			<td>Matlab</td>
			<td>The MathWorks, Inc., USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Excel for Mac&#160;</td>
			<td>Microsoft</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

analyzing synaptic modulation of drosophila melanogaster photoreceptors after exposure to prolonged light

The nervous system has the remarkable ability to adapt and respond to various stimuli. This neural adjustment is largely achieved through plasticity at the synaptic level. The Active Zone (AZ) is the region at the presynaptic membrane that mediates neurotransmitter release and is composed of a dense collection of scaffold proteins. AZs of Drosophila melanogaster (Drosophila) photoreceptors undergo molecular remodeling after prolonged exposure to natural ambient light. Thus the level of neuronal activity can rearrange the molecular composition of the AZ and contribute to the regulation of the functional output.
Starting from the light exposure set-up preparation to the immunohistochemistry, this protocol details how to quantify the number, the spatial distribution, and the delocalization level of synaptic molecules at AZs in Drosophila photoreceptors. Using image analysis software, clusters of the GFP-fused AZ component Bruchpilot were identified for each R8 photoreceptor (R8) axon terminal. Detected Bruchpilot spots were automatically assigned to individual R8 axons. To calculate the distribution of spot frequency along the axon, we implemented a customized software plugin. Each axon&#39;s start-point and end-point were manually defined and the position of each Bruchpilot spot was projected onto the connecting line between start and end-point. Besides the number of Bruchpilot clusters, we also quantified the delocalization level of Bruchpilot-GFP within the clusters. These measurements reflect in detail the spatially resolved synaptic dynamics in a single neuron under different environmental conditions to stimuli.

The compound eye of Drosophila comprises ~780 ommatidia, each containing eight types of photoreceptors (R1-8). R7 and R8 project their axons to the second optic ganglion, the medulla, where they form synapses in layers M6 and M3, respectively26. To investigate the effect of prolonged exposure to light on the molecular composition of photoreceptor R8 active zones, we took advantage of the STaR method15. Endogenous expression levels o...

Watch this Scientific Journal Video about Analyzing Synaptic Modulation of Drosophila melanogaster Photoreceptors after Exposure to Prolonged Light at JoVE.com

Analyzing Synaptic Modulation of Drosophila melanogaster Photoreceptors after Exposure to Prolonged Light

Here we show how to quantify the number and spatial distribution of synaptic active zones in Drosophila melanogaster&#160;photoreceptors, highlighted with a genetically encoded molecular marker, and their modulation after prolonged exposure to light.

Analyzing Synaptic Modulation of Drosophila melanogaster Photoreceptors after Exposure to Prolonged Light

The nervous system has the remarkable ability to adapt and respond to various stimuli. This neural adjustment is largely achieved through plasticity at ...

The overall goal of this experimental procedure is to understand synaptic dynamics in a single neuron under different activation conditions. This method can help answer key questions in the synaptic plasticity field such as revealing changes in the molecular composition of synapses upon maturation of the neuron's activity. The main advantage of this technique is that it allows the semi-automated analysis of multiple aspects of synapses including their number, distribution, and the level of enrichment of molecular components after synapses.For this experiment, collect the flies into normal vials within six hours of eclosion. Load the collection vials into a transparent acrylic rack. In a small incubator set to 25 degrees celsius, position the rack at a precise distance from an LED panel where the light exposure is at an average of 1000 lux.Then, rear flies for one to three days using one of the following conditions, either constant darkness, 12 hours of light followed by 12 hours of darkness, or constant light. Later, dissect and stain the brains using standard techniques. To mount the fly brains, load a micropipet with mounting medium and deposit two 2 microliter drops at the center of a microscope slide about 2 cm apart.Place a cover slip onto each drop and the gape between about 0.2 mm. Then deposit 15 microliters of mounting medium over the cover slips and into the gap. Under a dissecting microscope, deposit the brain into the gap from micropipet.And then position the brains, ventral side up. Finally, attach a cover slip and seal it along the edges using clear nail polish. The brains can then be imaged using standard techniques to reconstitute 3D images.In this case, GFP luminescence is documented in cells with active Brp expression using the star method. Also in this example, R7 and R8 photoreceptor axons were immunolabled with anticiaoptin, which was viewed using RFP-tagged secondary antibodies. To quantify the number, distribution, and delocalization level of the Brp GFP puncta first load reconstituted 3D images of the brain made from image stacks.Brp puncta are displayed in white. Now, find the region of interest. In this case, R8 axon's terminals are located by following the thinning of the anticiaoptin positive axons at the entry point into the M3 medulla layer.At each R8 axon terminal identify the Brp GFP puncta using the spot detection module. Select add new spots then select segment only region of interest in the algorithm settings. Once the analysis region is defined, set the source channel to Brp GFP then set the estimated XY diameter to 0.35 microns.And then, check off background subtraction in the spot detection. Next, select quality as the filter type, and the puncta are filtered automatically. Complete this step by clicking finish.Repeat the spot detection method for all of R8 axons in the dataset. The next region to identify is the axon cytoplasm. First, generate surface objects with the surface function.Then, select add new surfaces, and under the algorithm settings, toggle segment only region of interest. Now, manually select the region of interest. Next, set the calculation perimeters.To find the photoreceptor channel as source, select the smooth option. For the threshold, select absolute intensity. Enable the split touching objects option.Set the seat points diameter to 0.5 microns and use the default filter settings for quality and number of voxels. The filter is then applied automatically. Now, go to edit and delete the pieces of surface generated outside of the region of interest.In this case, the other axons. After repeating the axon region detection for all R8 axons in the dataset, all the Brp puncta and R8 axons are identified as a set of spot objects. And the corresponding cytoplasmic regions are identified as surface objects.Now, proceed by manually defining each axon's orientation and space. This is important for later quantification of Brp GFP density along each neuron in the medulla neuropil. To do this, first define their start points and end points.Select add new measurement points, then select edit followed by select surface of object to work with the top of the surface objects. To define the start points, put measurement points on all the surface objects of the R axons in the M1 layer. Place these points in a systematic reproducible order.Next, define the end points. Select add new measurement points, edit, and surface of object again. Then, repeating the same systematic order, place measurement points on the bottom of the R axons in M3 layer.To quantify the Brp background intensity, analyze the cytoplasmic regions of two R7 axons. Select add new surfaces and manually define the region of an R7 axon as was done for the R8 axons. Use identical settings except do not toggle on the enable split touching objects option.Leave this off. Next, add a dummy spots object inside a defined R7 axon region. Select add new spots, and select skip automatic creation, and edit manually.Then, select center of object and click on the surface object to place the dummy spots object inside the R7 axon. Now, repeat the surface and spot detection steps for a second R7 axon. And then define the start and end terminal points of the R7 axons as done with the R8 axons.For this analysis, be certain to have the correct software installed. Open the dataset containing the spot data, surfaces data, and two measurement point objects, each containing the same number of measurement points. Inspect the data.Both of the measurement point objects must have the same number of measurement points for the calculations to work. Once the spots, axon regions, and start and end points have been defined, start the plugin. First, check the metadata, in particular, the voxel size.Open image properties from edit, then check the 3 dimensions of the voxel and microns under coordinates in geometry. Next, select a channel for the intensity analysis. In this case, the channel showing Brp GFP is selected.Then define the file name for the results. Next, define the number of bins as 10, and set the axon length to 100%Then define the regions of the puncta by setting the spot radius to 0.35 microns and the surrounding cytoplasmic region to 50 microns. Finally, execute the synapse detection command, and later, statistically analyze the output.Following the described protocols, Brp GFP puncta were analyzed in the R8 synapses of flies exposed to constant darkness, constant light, or a normal light/dark cycle. The number of Brp puncta was significantly reduced in R8 photoreceptors of flies kept in constant light. The distribution of the puncta was calculated using a custom plugin.R8 synapses were distributed all along the axonal shaft from the M1 to the M3 layer, but their density was higher at the M1 and M3 layers. Similarly, delocalization levels of the puncta were calculated. They were unchanged in all conditions, however delocalization levels of Brp GFP differed from other reporters, like Brp-short-cherry which becomes clearly defused under constant light.It is possible that there is inappropriate processing of the Brp short fragment after disassembling from the AZ.After watching this video, you should have a good understanding of how to analyze synaptic plastic properties in a single neuron. Such plastic properties includes the synapse number, their distribution, and the label of enrichment of a specific molecular component after the synapses.

analyzing-synaptic-modulation-drosophila-melanogaster-photoreceptors

Research

JoVE Journal

Neuroscience

Optogenetic Stimulation of Escape Behavior in Drosophila melanogaster

A growing number of genetically encoded tools are becoming available that allow non-invasive manipulation of the neural activity of specific neurons in Drosophila melanogaster1. Chief among these are optogenetic tools, which enable the activation or silencing of specific neurons in the intact and freely moving animal using bright light. Channelrhodopsin (ChR2) is a light-activated cation channel that, when activated by blue light, causes depolarization of neurons that express it. ChR2 has been effective for identifying neurons critical for specific behaviors, such as CO2 avoidance, proboscis extension and giant-fiber mediated startle response2-4. However, as the intense light sources used to stimulate ChR2 also stimulate photoreceptors, these optogenetic techniques have not previously been used in the visual system. Here, we combine an optogenetic approach with a mutation that impairs phototransduction to demonstrate that activation of a cluster of loom-sensitive neurons in the fly's optic lobe, Foma-1 neurons, can drive an escape behavior used to avoid collision. We used a null allele of a critical component of the phototransduction cascade, phospholipase C-&beta;, encoded by the norpA gene, to render the flies blind and also use the Gal4-UAS transcriptional activator system to drive expression of ChR2 in the Foma-1 neurons. Individual flies are placed on a small platform surrounded by blue LEDs. When the LEDs are illuminated, the flies quickly take-off into flight, in a manner similar to visually driven loom-escape behavior. We believe that this technique can be easily adapted to examine other behaviors in freely moving flies.

Optogenetic Stimulation of Escape Behavior in Drosophila melanogaster

Genetically encoded optogenetic tools enable noninvasive manipulation of specific neurons in the Drosophila brain. Such tools can identify neurons whose activation is sufficient to elicit or suppress particular behaviors. Here we present a method for activating Channelrhodopsin2 that is expressed in targeted neurons in freely walking flies.

A  growing number of genetically encoded tools are becoming available that allow non-invasive  manipulation of the neural activity of specific neurons in ...

Determination of the Spontaneous Locomotor Activity in Drosophila melanogaster

Drosophila melanogaster has been used as an excellent model organism to study environmental and genetic manipulations that affect behavior. One such behavior is spontaneous locomotor activity. Here we describe our protocol that utilizes Drosophila population monitors and a tracking system that allows continuous monitoring of the spontaneous locomotor activity of flies for several days at a time. This method is simple, reliable, and objective and can be used to examine the effects of aging, sex, changes in caloric content of food, addition of drugs, or genetic manipulations that mimic human diseases.

Determination of the Spontaneous Locomotor Activity in Drosophila melanogaster

Drosophila melanogaster are useful in studying genetic or environmental manipulations that affect behaviors such as spontaneous locomotor activity.&#160; Here we describe a protocol that utilizes monitors with infrared beams and data analysis software to quantify spontaneous locomotor activity.&#160;

Drosophila melanogaster has been used as an excellent model organism to study environmental and genetic manipulations that affect behavior. One such ...

Conditions Affecting Social Space in Drosophila melanogaster

The social space assay described here can be used to quantify social interactions of Drosophila melanogaster &#8212; or other small insects &#8212; in a straightforward manner. As we previously demonstrated 1, in a two-dimensional chamber, we first force the flies to form a tight group, subsequently allowing them to take their preferred distance from each other. After the flies have settled, we measure the distance to the closest neighbor (or social space), processing a static picture with free online software (ImageJ). The analysis of the distance to the closest neighbor allows researchers to determine the effects of genetic and environmental factors on social interaction, while controlling for potential confounding factors. Diverse factors such as climbing ability, time of day, sex, and number of flies, can modify social spacing of flies. We thus propose a series of experimental controls to mitigate these confounding effects. This assay can be used for at least two purposes. First, researchers can determine how their favorite environmental shift (such as isolation, temperature, stress or toxins) will impact social spacing 1,2. Second, researchers can dissect the genetic and neural underpinnings of this basic form of social behavior 1,3. Specifically, we used it as a diagnostic tool to study the role of orthologous genes thought to be involved in social behavior in other organisms, such as candidate genes for autism in humans 4.

Conditions Affecting Social Space in Drosophila melanogaster

The effect of genes and environment on social space of Drosophila melanogaster can be quantified through a powerful but straightforward analytical paradigm. We show here different factors that can affect this social space, and thus need to be taken into consideration when designing experiments in this paradigm.

The social space assay described here can be used to quantify social interactions of Drosophila melanogaster &#8212; or other small insects &#8212; in a ...

High Throughput Assay to Examine Egg-Laying Preferences of Individual Drosophila melanogaster

Recently, egg-laying preference of Drosophila has emerged as a genetically tractable model to study the neural basis of simple decision-making processes. When selecting sites to deposit their eggs, female flies are capable of ranking the relative attractiveness of their options and choosing the &#34;greater of two goods.&#34; However, most egg-laying preference assays are not practical if one wants to take a systematic genetic screening approach to search for the circuit basis underlying this simple decision-making process, as they are population-based and laborious to set up. To increase the throughput of studying of egg-laying preferences of single females, we developed custom chambers that each can simultaneously assay egg-laying preferences of up to thirty individual flies as well as a protocol that ensures each female has a high egg-laying rate (so that their preference is readily discernable and more convincing). Our approach is simple to execute and produces very consistent results. Additionally, these chambers can be equipped with different attachments to allow video recording the egg-laying animals and to deliver light for optogenetics studies. This article provides the blueprints for fabricating these chambers and the procedure for preparing the flies to be assayed in these chambers.

High Throughput Assay to Examine Egg-Laying Preferences of Individual Drosophila melanogaster

This protocol describes a high throughput assay for testing egg-laying preferences of Drosophila melanogaster at single-animal resolution. This assay provides a simple, efficient, and scalable platform to identify genes and circuit components that control a simple decision-making process.

Recently, egg-laying preference of Drosophila has emerged as a genetically tractable model to study the neural basis of simple decision-making processes. ...

Electrophysiological Method for Recording Intracellular Voltage Responses of Drosophila Photoreceptors and Interneurons to Light Stimuli In Vivo

Voltage responses of insect photoreceptors and visual interneurons can be accurately recorded with conventional sharp microelectrodes. The method described here enables the investigator to measure long-lasting (from minutes to hours) high-quality intracellular responses from single Drosophila R1-R6 photoreceptors and Large Monopolar Cells (LMCs) to light stimuli. Because the recording system has low noise, it can be used to study variability among individual cells in the fly eye, and how their outputs reflect the physical properties of the visual environment. We outline all key steps in performing this technique. The basic steps in constructing an appropriate electrophysiology set-up for recording, such as design and selection of the experimental equipment are described. We also explain how to prepare for recording by making appropriate (sharp) recording and (blunt) reference electrodes. Details are given on how to fix an intact fly in a bespoke fly-holder, prepare a small window in its eye and insert a recording electrode through this hole with minimal damage. We explain how to localize the center of a cell's receptive field, dark- or light-adapt the studied cell, and to record its voltage responses to dynamic light stimuli. Finally, we describe the criteria for stable normal recordings, show characteristic high-quality voltage responses of individual cells to different light stimuli, and briefly define how to quantify their signaling performance. Many aspects of the method are technically challenging and require practice and patience to master. But once learned and optimized for the investigator's experimental objectives, it grants outstanding in vivo neurophysiological data.

Electrophysiological Method for Recording Intracellular Voltage Responses of Drosophila Photoreceptors and Interneurons to Light Stimuli In Vivo

Sharp microelectrodes enable accurate electrophysiological characterization of photoreceptor and visual interneuron output in living Drosophila. Here we show how to use this method to record high-quality voltage responses of individual cells to controlled light stimulation. This method is ideal for studying neural information processing in insect compound eyes.

Voltage responses of insect photoreceptors and visual interneurons can be accurately recorded with conventional sharp microelectrodes. The method ...

Electrophysiological Method for Whole-cell Voltage Clamp Recordings from Drosophila Photoreceptors

Whole-cell voltage clamp recordings from Drosophila melanogaster photoreceptors have revolutionized the field of invertebrate visual transduction, enabling the use of D. melanogaster molecular genetics to study inositol-lipid signaling and Transient Receptor Potential (TRP) channels at the single-molecule level. A handful of labs have mastered this powerful technique, which enables the analysis of the physiological responses to light under highly controlled conditions. This technique allows control over the intracellular and extracellular media; the membrane voltage; and the fast application of pharmacological compounds, such as a variety of ionic or pH indicators, to the intra- and extracellular media. With an exceptionally high signal-to-noise ratio, this method enables the measurement of dark spontaneous and light-induced unitary currents (i.e.&#160;spontaneous and quantum bumps) and macroscopic Light-induced Currents (LIC) from single D. melanogaster photoreceptors. This protocol outlines, in great detail, all the key steps necessary to perform this technique, which includes both electrophysiological and optical recordings. The fly retina dissection procedure for the attainment of intact and viable ex vivo isolated ommatidia in the bath chamber is described. The equipment needed to perform whole-cell and fluorescence imaging measurements are also detailed. Finally, the pitfalls in using this delicate preparation during extended experiments are explained.

Electrophysiological Method for Whole-cell Voltage Clamp Recordings from Drosophila Photoreceptors

Whole-cell recordings from Drosophila melanogaster photoreceptors enable the measurement of spontaneous dark bumps, quantum bumps, macroscopic responses to light, and current-voltage relationships under various conditions. In combination with D. melanogaster genetic manipulation tools, this method enables the study of the ubiquitous inositol-lipid signaling pathway and its target, the TRP channel.

Whole-cell voltage clamp recordings from Drosophila melanogaster photoreceptors have revolutionized the field of invertebrate visual transduction, ...

Desensitization and Recovery of Crayfish Photoreceptors Upon Delivery of a Light Stimulus

A method to study desensitization and recovery of crayfish photoreceptors is presented. We performed intracellular electrical recordings of photoreceptor cells in isolated eyestalks using the discontinuous single electrode-switched voltage-clamp configuration. First, with a razor blade we made an opening in the dorsal cornea to get access to the retina. Thereafter, we inserted a glass electrode through the opening, and penetrated a cell as reported by the recording of a negative potential. Membrane potential was clamped at the photoreceptor's resting potential and a light-pulse was applied to activate currents. Finally, the two light-flash protocol was employed to measure current desensitization and recovery. The first light-flash triggers, after a lag period, the transduction ionic current, which after reaching a peak amplitude decays towards a desensitized state; the second flash, applied at varying time intervals, assesses the state of the light-activated conductance. To characterize the light-elicited current, three parameters were measured: 1) latency (the time elapsed between light flash delivery and the moment in which current achieves 10% of its maximum value); 2) peak current; and 3) desensitization time constant (exponential time constant of the current decay phase). All parameters are affected by the first pulse.
To quantify recovery from desensitization, the ratio p2/p1 was employed versus time between pulses. p1 is the peak current evoked by the first light-pulse, and p2 is the peak current evoked by the second pulse. These data were fitted to a sum of exponential functions. Finally, these measurements were carried out as function of circadian time.

A protocol for the study of desensitization and sensitivity recovery of crayfish photoreceptors as a function of circadian time is presented.

A method to study desensitization and recovery of crayfish photoreceptors is presented. We performed intracellular electrical recordings of photoreceptor ...

Monitoring Cell-to-cell Transmission of Prion-like Protein Aggregates in Drosophila Melanogaster

Protein aggregation is a central feature of most neurodegenerative diseases, including Alzheimer&#39;s disease (AD), Parkinson&#39;s disease (PD), Huntington&#39;s disease (HD), and amyotrophic lateral sclerosis (ALS). Protein aggregates are closely associated with neuropathology in these diseases, although the exact mechanism by which aberrant protein aggregation disrupts normal cellular homeostasis is not known. Emerging data provide strong support for the hypothesis that pathogenic aggregates in AD, PD, HD, and ALS have many similarities to prions, which are protein-only infectious agents responsible for the transmissible spongiform encephalopathies. Prions self-replicate by templating the conversion of natively-folded versions of the same protein, causing spread of the aggregation phenotype. How prions and prion-like proteins in AD, PD, HD, and ALS move from one cell to another is currently an area of intense investigation. Here, a Drosophila melanogaster model that permits monitoring of prion-like, cell-to-cell transmission of mutant huntingtin (Htt) aggregates associated with HD is described. This model takes advantage of powerful tools for manipulating transgene expression in many different Drosophila tissues and utilizes a fluorescently-tagged cytoplasmic protein to directly report prion-like transfer of mutant Htt aggregates. Importantly, the approach we describe here can be used to identify novel genes and pathways that mediate spreading of protein aggregates between diverse cell types in vivo. Information gained from these studies will expand the limited understanding of the pathogenic mechanisms that underlie neurodegenerative diseases and reveal new opportunities for therapeutic intervention.

Monitoring Cell-to-cell Transmission of Prion-like Protein Aggregates in Drosophila Melanogaster

Accumulating evidence supports the idea that pathogenic protein aggregates associated with neurodegenerative diseases spread between cells with prion-like properties. Here, we describe a method that enables visualization of cell-to-cell spreading of prion-like aggregates in the model organism, Drosophila melanogaster.

Protein aggregation is a central feature of most neurodegenerative diseases, including Alzheimer&#39;s disease (AD), Parkinson&#39;s disease (PD), ...

Combining Optogenetics with Artificial microRNAs to Characterize the Effects of Gene Knockdown on Presynaptic Function within Intact Neuronal Circuits

The purpose of this protocol is to characterize the effect of gene knockdown on presynaptic function within intact neuronal circuits. We describe a workflow on how to combine artificial microRNA (miR)-mediated RNA interference with optogenetics to achieve selective stimulation of manipulated presynaptic boutons in acute brain slices. The experimental approach involves the use of a single viral construct and a single neuron-specific promoter to drive the expression of both an optogenetic probe and artificial miR(s) against presynaptic gene(s). When stereotactically injected in the brain region of interest, the expressed construct makes it possible to stimulate with light exclusively the neurons with reduced expression of the gene(s) under investigation. This strategy does not require the development and maintenance of genetically modified mouse lines and can in principle be applied to other organisms and to any neuronal gene of choice. We have recently applied it to investigate how the knockdown of alternative splice isoforms of presynaptic P/Q-type voltage-gated calcium channels (VGCCs) regulates short-term synaptic plasticity at CA3 to CA1 excitatory synapses in acute hippocampal slices. A similar approach could also be used to manipulate and probe the neuronal circuitry in vivo.

This protocol provides a workflow on how to combine artificial microRNA-mediated RNA interference with optogenetics to stimulate specifically presynaptic boutons with reduced expression of selective gene(s) within intact neuronal circuits.

The purpose of this protocol is to characterize the effect of gene knockdown on presynaptic function within intact neuronal circuits. We describe a ...

In Vivo Optical Calcium Imaging of Learning-Induced Synaptic Plasticity in Drosophila melanogaster

Decades of research in many model organisms have led to the current concept of synaptic plasticity underlying learning and memory formation. Learning-induced changes in synaptic transmission are often distributed across many neurons and levels of processing in the brain. Therefore, methods to visualize learning-dependent synaptic plasticity across neurons are needed. The fruit fly Drosophila melanogaster represents a particularly favorable model organism to study neuronal circuits underlying learning. The protocol presented here demonstrates a way in which the processes underlying the formation of associative olfactory memories, i.e., synaptic activity and their changes, can be monitored in vivo. Using the broad array of genetic tools available in Drosophila, it is possible to specifically express genetically encoded calcium indicators in determined cell populations and even single cells. By fixing a fly in place, and opening the head capsule, it is possible to visualize calcium dynamics in these cells whilst delivering olfactory stimuli. Additionally, we demonstrate a set-up in which the fly can be subjected, simultaneously, to electric shocks to the body. This provides a system in which flies can undergo classical olfactory conditioning - whereby a previously na&#239;ve odor is learned to be associated with electric shock punishment - at the same time as the representation of this odor (and other untrained odors) is observed in the brain via two-photon microscopy. Our lab has previously reported the generation of synaptically localized calcium sensors, which enables one to confine the fluorescent calcium signals to pre- or postsynaptic compartments. Two-photon microscopy provides a way to spatially resolve fine structures. We exemplify this by focusing on neurons integrating information from the mushroom body, a higher-order center of the insect brain. Overall, this protocol provides a method to examine the synaptic connections between neurons whose activity is modulated as a result of olfactory learning.

In Vivo Optical Calcium Imaging of Learning-Induced Synaptic Plasticity in Drosophila melanogaster

Here we present a protocol with which pre- and/or postsynaptic calcium can be visualized in the context of Drosophila learning and memory. In vivo calcium imaging using synaptically localized calcium sensors is combined with a classical olfactory conditioning paradigm such that the synaptic plasticity underlying this type of associative learning may be determined.