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>
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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>

The authors have nothing to disclose.

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

6.4K Görüntüleme.  Niigata University. 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 en...