We thank Michael Rosbash for his mentorship and support during the initial phase of the development of this method. This work was funded by the JST PRESTO program, the Swiss National Science Foundation (31003A_149893 and 31003A_169548), the European Research Council (ERC-StG-311194), Novartis Foundation for Medical-Biomedical Research (13A39) and the University of Geneva.

1. Preparation of Stock Solutions Under a Culture Hood
<ol>
	<li>Prepare 400 mL of 1x Schneider Active Medium (SAM) optimized for ex vivo culture of larval brains (modified from reference24,25) (Table 1). Aliquot to 5 mL and flash freeze in liquid nitrogen (LN2), store at - 80 &#176;C.</li>
	<li>Prepare 1x Dissecting Saline Solution (DSS) by diluting 10x stock solution (modified from reference26) (<st...

<ol>
	<li>Sheeba, V., Kaneko, M., Sharma, V. K., Holmes, 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+Drosophila+circadian+pacemaker+circuit:+Pas+De+Deux+or+Tarantella?.">The Drosophila circadian pacemaker circuit: Pas De Deux or Tarantella?.</a> Crit Rev Biochem Mol Biol. 43 (1), 37-61 (2008).</li><li>Granados-Fuentes, D., Herzog, 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=The+clock+shop:+coupled+circadian+oscillators.">The clock shop: coupled circadian oscillators.</a> Exp Neurol. 243, 21-27 (2013).</li><li>Zhang, Y., Emery, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chapter+15+-+Molecular+and+neural+control+of+insects+circadian+rhythms.">Chapter 15 - Molecular and neural control of insects circadian rhythms.</a> Insect molecular biology and biochemistry. , 513-551 (2012).</li><li>Hardin, P. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+genetic+analysis+of+circadian+timekeeping+in+Drosophila.">Molecular genetic analysis of circadian timekeeping in Drosophila.</a> Adv Genet. 74, 141-173 (2011).</li><li>Yoshii, T., Rieger, D., Helfrich-Forster, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two+clocks+in+the+brain:+an+update+of+the+morning+and+evening+oscillator+model+in+Drosophila.">Two clocks in the brain: an update of the morning and evening oscillator model in Drosophila.</a> Prog Brain Res. 199, 59-82 (2012).</li><li>Malpel, S., Klarsfeld, A., Rouyer, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Circadian+synchronization+and+rhythmicity+in+larval+photoperception-defective+mutants+of+Drosophila.">Circadian synchronization and rhythmicity in larval photoperception-defective mutants of Drosophila.</a> J Biol Rhythms. 19 (1), 10-21 (2004).</li><li>Mazzoni, E. O., Desplan, C., Blau, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Circadian+pacemaker+neurons+transmit+and+modulate+visual+information+to+control+a+rapid+behavioral+response.">Circadian pacemaker neurons transmit and modulate visual information to control a rapid behavioral response.</a> Neuron. 45 (2), 293-300 (2005).</li><li>Sabado, V., Vienne, L., Nunes, J. M., Rosbash, M., Nagoshi, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescence+circadian+imaging+reveals+a+PDF-dependent+transcriptional+regulation+of+the+Drosophila+molecular+clock.">Fluorescence circadian imaging reveals a PDF-dependent transcriptional regulation of the Drosophila molecular clock.</a> Sci Rep. 7, 41560 (2017).</li><li>Hyun, 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=Drosophila+GPCR+Han+is+a+receptor+for+the+circadian+clock+neuropeptide+PDF.">Drosophila GPCR Han is a receptor for the circadian clock neuropeptide PDF.</a> Neuron. 48 (2), 267-278 (2005).</li><li>Lear, B. 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=A+G+protein-coupled+receptor,+groom-of-PDF,+is+required+for+PDF+neuron+action+in+circadian+behavior.">A G protein-coupled receptor, groom-of-PDF, is required for PDF neuron action in circadian behavior.</a> Neuron. 48 (2), 221-227 (2005).</li><li>Mertens, I., 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=PDF+receptor+signaling+in+Drosophila+contributes+to+both+circadian+and+geotactic+behaviors.">PDF receptor signaling in Drosophila contributes to both circadian and geotactic behaviors.</a> Neuron. 48 (2), 213-219 (2005).</li><li>Ayaz, D., 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=Axonal+injury+and+regeneration+in+the+adult+brain+of+Drosophila.">Axonal injury and regeneration in the adult brain of Drosophila.</a> J Neurosci. 28 (23), 6010-6021 (2008).</li><li>Prithviraj, R., Trunova, S., Giniger, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ex+vivo+culturing+of+whole,+developing+Drosophila+brains.">Ex vivo culturing of whole, developing Drosophila brains.</a> J Vis Exp. (65), (2012).</li><li>Siller, K. H., Serr, M., Steward, R., Hays, T. S., Doe, C. Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Live+imaging+of+Drosophila+brain+neuroblasts+reveals+a+role+for+Lis1/dynactin+in+spindle+assembly+and+mitotic+checkpoint+control.">Live imaging of Drosophila brain neuroblasts reveals a role for Lis1/dynactin in spindle assembly and mitotic checkpoint control.</a> Mol Biol Cell. 16 (11), 5127-5140 (2005).</li><li>Zschatzsch, M., 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=Regulation+of+branching+dynamics+by+axon-intrinsic+asymmetries+in+Tyrosine+Kinase+Receptor+signaling.">Regulation of branching dynamics by axon-intrinsic asymmetries in Tyrosine Kinase Receptor signaling.</a> Elife. 3, e01699 (2014).</li><li>Cabernard, C., Doe, C. Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Live+imaging+of+neuroblast+lineages+within+intact+larval+brains+in+Drosophila.">Live imaging of neuroblast lineages within intact larval brains in Drosophila.</a> Cold Spring Harb Protoc. 2013 (10), 970-977 (2013).</li><li>Januschke, J., Gonzalez, 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+interphase+microtubule+aster+is+a+determinant+of+asymmetric+division+orientation+in+Drosophila+neuroblasts.">The interphase microtubule aster is a determinant of asymmetric division orientation in Drosophila neuroblasts.</a> The Journal of Cell Biology. 188 (5), 693-706 (2010).</li><li>Williamson, W. R., Hiesinger, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+developing+and+adult+Drosophila+brains+and+retinae+for+live+imaging.">Preparation of developing and adult Drosophila brains and retinae for live imaging.</a> J Vis Exp. (37), (2010).</li><li>Roberts, 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=Light+evokes+rapid+circadian+network+oscillator+desynchrony+followed+by+gradual+phase+retuning+of+synchrony.">Light evokes rapid circadian network oscillator desynchrony followed by gradual phase retuning of synchrony.</a> Curr Biol. 25 (7), 858-867 (2015).</li><li>Sehadova, H., 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=Temperature+entrainment+of+Drosophila's+circadian+clock+involves+the+gene+nocte+and+signaling+from+peripheral+sensory+tissues+to+the+brain.">Temperature entrainment of Drosophila's circadian clock involves the gene nocte and signaling from peripheral sensory tissues to the brain.</a> Neuron. 64 (2), 251-266 (2009).</li><li>Sellix, M. T., Currie, J., Menaker, M., Wijnen, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescence/luminescence+circadian+imaging+of+complex+tissues+at+single-cell+resolution.">Fluorescence/luminescence circadian imaging of complex tissues at single-cell resolution.</a> J Biol Rhythms. 25 (3), 228-232 (2010).</li><li>Liang, X., Holy, T. E., Taghert, P. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synchronous+Drosophila+circadian+pacemakers+display+nonsynchronous+Ca(2)(+)+rhythms+in+vivo.">Synchronous Drosophila circadian pacemakers display nonsynchronous Ca(2)(+) rhythms in vivo.</a> Science. 351 (6276), 976-981 (2016).</li><li>Liang, X., Holy, T. E., Taghert, P. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Series+of+Suppressive+Signals+within+the+Drosophila+Circadian+Neural+Circuit+Generates+Sequential+Daily+Outputs.">A Series of Suppressive Signals within the Drosophila Circadian Neural Circuit Generates Sequential Daily Outputs.</a> Neuron. , (2017).</li><li>Kuppers-Munther, B., 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=A+new+culturing+strategy+optimises+Drosophila+primary+cell+cultures+for+structural+and+functional+analyses.">A new culturing strategy optimises Drosophila primary cell cultures for structural and functional analyses.</a> Dev Biol. 269 (2), 459-478 (2004).</li><li>Schneider, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differentiation+of+Larval+Drosophila+Eye-Antennal+Discs+in+Vitro.">Differentiation of Larval Drosophila Eye-Antennal Discs in Vitro.</a> J Exp Zool. 156, 91-103 (1964).</li><li>Jiang, S. A., Campusano, J. M., Su, H., O'Dowd, D. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophila+mushroom+body+Kenyon+cells+generate+spontaneous+calcium+transients+mediated+by+PLTX-sensitive+calcium+channels.">Drosophila mushroom body Kenyon cells generate spontaneous calcium transients mediated by PLTX-sensitive calcium channels.</a> J Neurophysiol. 94 (1), 491-500 (2005).</li><li>Hafer, N., Schedl, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dissection+of+larval+CNS+in+Drosophila+melanogaster.">Dissection of larval CNS in Drosophila melanogaster.</a> J Vis Exp. (1), e85 (2006).</li><li>Schindelin, 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=Fiji:+an+open-source+platform+for+biological-image+analysis.">Fiji: an open-source platform for biological-image analysis.</a> Nat Methods. 9 (7), 676-682 (2012).</li><li>Rabinovich, D., Mayseless, O., Schuldiner, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long+term+ex+vivo+culturing+of+Drosophila+brain+as+a+method+to+live+image+pupal+brains:+insights+into+the+cellular+mechanisms+of+neuronal+remodeling.">Long term ex vivo culturing of Drosophila brain as a method to live image pupal brains: insights into the cellular mechanisms of neuronal remodeling.</a> Front Cell Neurosci. 9, 327 (2015).</li><li>Forer, A., Pickett-Heaps, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fibrin+clots+keep+non-adhering+living+cells+in+place+on+glass+for+perfusion+or+fixation.">Fibrin clots keep non-adhering living cells in place on glass for perfusion or fixation.</a> Cell Biol Int. 29 (9), 721-730 (2005).</li><li>Forer, A., Pickett-Heaps, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cytochalasin+D+and+latrunculin+affect+chromosome+behaviour+during+meiosis+in+crane-fly+spermatocytes.">Cytochalasin D and latrunculin affect chromosome behaviour during meiosis in crane-fly spermatocytes.</a> Chromosome Res. 6 (7), 533-549 (1998).</li><li>Lukinavi&#269;ius, G., 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=SiR-Hoechst+is+a+far-red+DNA+stain+for+live-cell+nanoscopy.">SiR-Hoechst is a far-red DNA stain for live-cell nanoscopy.</a> Nature Communications. 6, 8497 (2015).</li><li>Medioni, C., Ephrussi, A., Besse, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Live+imaging+of+axonal+transport+in+Drosophila+pupal+brain+explants.">Live imaging of axonal transport in Drosophila pupal brain explants.</a> Nat Protoc. 10 (4), 574-584 (2015).</li><li>Enoki, R., Ono, D., Hasan, M. T., Honma, S., Honma, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-cell+resolution+fluorescence+imaging+of+circadian+rhythms+detected+with+a+Nipkow+spinning+disk+confocal+system.">Single-cell resolution fluorescence imaging of circadian rhythms detected with a Nipkow spinning disk confocal system.</a> J Neurosci Methods. 207 (1), 72-79 (2012).</li><li>Ozel, M. N., Langen, M., Hassan, B. A., Hiesinger, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Filopodial+dynamics+and+growth+cone+stabilization+in+Drosophila+visual+circuit+development.">Filopodial dynamics and growth cone stabilization in Drosophila visual circuit development.</a> Elife. 4, (2015).</li><li>Yao, Z., Macara, A. M., Lelito, K. R., Minosyan, T. Y., Shafer, O. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+functional+neuronal+connectivity+in+the+Drosophila+brain.">Analysis of functional neuronal connectivity in the Drosophila brain.</a> J Neurophysiol. 108 (2), 684-696 (2012).</li></ol>

Here we described the method for long-term fluorescence time-lapse microscopy of cultured larval brains. The success of this type of experiments depends on multiple factors, such as the health of the culture, method for immobilization of the brain explant, fluorescence intensity and signal-to-noise ratio of the reporter, temporal and spatial resolution, and accessibility to the explant. These factors can be mutually exclusive. For example, increasing time-lapse frequency affects the health of the culture, and the immobil...

Circadian clocks help organisms to adapt to the periodic environmental changes generated by the 24 h rotation of the Earth. The interlocked transcriptional-translational feedback loops commonly underlie the molecular machinery of circadian clocks across species1. The circadian pacemaker circuit composed of clock-containing neurons integrates time-of-day information conveyed by the environmental cues, such as light/dark (LD) and temperature cycles, to orchestrate the rhythms of a plethora of daily physiological and behavioral processes2,3. The coordination of molecular rhythms with neuronal inputs and outputs is critically important for the operation of the circadian circuit but remains only partially understood.
In Drosophila, at the core of the molecular clock, the CLOCK/CYCLE (CLK/CYC) heterodimer activates the transcription of period (per) and timeless (tim). PER and TIM form a complex and enter the nucleus, where they inhibit transcriptional activity of CLK/CYC and consequently their own transcription. Post-transcriptional and post-translational regulations cause delays between CLK/CYC-mediated transcription and repression by PER/TIM, ensuring the generation of circa 24-h molecular oscillations1,3,4. About 150 neurons containing these molecular clocks form a circuit to control circadian behavior of adult flies5. A much simpler yet fully functional circadian circuit consisting of 3 groups of clock neurons - 5 ventral Lateral Neurons (LNvs; 4 PDF-positive LNvs and one PDF-negative LNv, see below), 2 Dorsal Neuron 1s (DN1s) and 2 Dorsal Neuron 2s (DN2s) - is present in the larval brain6,7.
The simple larval circadian circuit offers an excellent model to study the interactions between inter-neuronal communication and the molecular clockwork. Using our newly developed fluorescent reporter PER-TDT, which mimics the levels of PER protein and its subcellular location, we sought to characterize the dynamics of the molecular clockwork in different clock neuron subgroups in the larval circadian circuit8. Furthermore, knowing the key role of the neuropeptide pigment-dispersing factor (PDF) produced by 4 LNvs in regulating circadian rhythms at the neuronal level9,10,11, we wanted to examine the direct effect of PDF on the molecular clocks. To this end, we developed a method to monitor circadian gene expression rhythms in larval brain explant over multiple days by time-lapse confocal microscopy. The protocol was also adapted for pharmacological assays to test the effect of PDF or other compounds on the level of PER-TDT. Thus, the adaptation consists of making the brain explant culture accessible to drug application, increasing temporal resolution and imaging for a shorter duration.
Ex vivo culture of Drosophila brains of different developmental stages have been previously established12,13,14,15,16,17,18. Whereas these protocols have been used for imaging various biological phenomena, some of them are not compatible with imaging at single-cell resolution or do not support the culture for more than several hours. Alternative methods to perform long-term live imaging of circadian neurons in Drosophila include bioluminescence imaging of molecular rhythms19,20,21 and fluorescence imaging of calcium indicator with light sheet microscopy22,23. Although bioluminescence imaging can achieve higher temporal resolution and light sheet microscopy can be adaptable for in vivo imaging, they are limited on the spatial resolution and require specialized microscope systems.
The method described here is tailored to visualize fluorescent signals in the whole brain culture at single-cell resolution over multiple days. This facile and versatile method could be adapted to image cultured adult fly brains and for pharmacological experiments to study many different problems in Drosophila neurobiology.

<table>
	<tbody>
		<tr>
			<td>KH2PO4</td>
			<td>Sigma-Aldrich</td>
			<td>P5655</td>
			<td>I am not sure they are exactly the same ones we have in the lab. I chose &#34;suitable for insect cell culture&#34; whenever available</td>
		</tr>
		<tr>
			<td>CaCl2</td>
			<td>Sigma-Aldrich</td>
			<td>C7902</td>
			<td></td>
		</tr>
		<tr>
			<td>MgSO4.7H2O</td>
			<td>Sigma-Aldrich</td>
			<td>230391</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma-Aldrich</td>
			<td>S5886</td>
			<td></td>
		</tr>
		<tr>
			<td>NaHCO3</td>
			<td>Sigma-Aldrich</td>
			<td>S5761</td>
			<td></td>
		</tr>
		<tr>
			<td>D-(+) Glucose</td>
			<td>Sigma-Aldrich</td>
			<td>G7021</td>
			<td></td>
		</tr>
		<tr>
			<td>Yeast extract</td>
			<td>Sigma-Aldrich</td>
			<td>Y1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Insulin</td>
			<td>Sigma-Aldrich</td>
			<td>I0516-5ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin</td>
			<td>Sigma-Aldrich</td>
			<td>P4333</td>
			<td></td>
		</tr>
		<tr>
			<td>BIS-TRIS</td>
			<td>Sigma-Aldrich</td>
			<td>B4429</td>
			<td></td>
		</tr>
		<tr>
			<td>L-(&#8722;)-Malic acid</td>
			<td>Sigma-Aldrich</td>
			<td>M7397</td>
			<td></td>
		</tr>
		<tr>
			<td>D-(+)-Trehalose dihydrate</td>
			<td>Sigma-Aldrich</td>
			<td>T0167</td>
			<td></td>
		</tr>
		<tr>
			<td>Succinic acid</td>
			<td>Sigma-Aldrich</td>
			<td>S9512</td>
			<td></td>
		</tr>
		<tr>
			<td>Fumaric acid</td>
			<td>Sigma-Aldrich</td>
			<td>F8509</td>
			<td></td>
		</tr>
		<tr>
			<td>&#945;-Ketoglutaric acid</td>
			<td>Sigma-Aldrich</td>
			<td>K1128</td>
			<td></td>
		</tr>
		<tr>
			<td>Non-heat-inactivated, Foetal Calf Serum (FCS) Mycoplasma and Virus screened</td>
			<td>BioConcept Ltd. Amimed</td>
			<td>2-01F30-I</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES-KOH, pH 7.4</td>
			<td>E&#38;K Scientific Products</td>
			<td>EK-654011</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sigma-Aldrich</td>
			<td>P5405</td>
			<td></td>
		</tr>
		<tr>
			<td>NaH2PO4</td>
			<td>Sigma-Aldrich</td>
			<td>S5011</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Sigma-Aldrich</td>
			<td>S7903</td>
			<td></td>
		</tr>
		<tr>
			<td>Fibrinogen from bovine plasma</td>
			<td>Calbiochem (Merck)</td>
			<td>341573-1GM</td>
			<td>CAUTION: Harmful by inhalation, in contact with skin and if swallowed. Manipulate under laminar flow</td>
		</tr>
		<tr>
			<td>Thrombin from bovine plasma</td>
			<td>Sigma-Aldrich</td>
			<td>T9549</td>
			<td>CAUTION: Health Hazard, use gloves</td>
		</tr>
		<tr>
			<td>PDF, NH2-NSELINSLLSLPKNMNDA-OH</td>
			<td>Chi Scientific</td>
			<td>custom made</td>
			<td></td>
		</tr>
		<tr>
			<td>Vaccum grease</td>
			<td>Sigma-Aldrich</td>
			<td>18405</td>
			<td></td>
		</tr>
		<tr>
			<td>35 mm Dish, No. 1.5 Coverslip, 20 mm Glass Diameter, Uncoated</td>
			<td>MatTek</td>
			<td>P35G-1.5-20-C</td>
			<td></td>
		</tr>
		<tr>
			<td>Corning Falcon Easy-Grip Tissue Culture Dishes</td>
			<td>fisherscientific</td>
			<td>08-772A</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile 500 mL Steritop-GP 33 mm threaded bottle top filter, 0.22 &#956;m</td>
			<td>Millipore</td>
			<td>SCGPS05RE</td>
			<td></td>
		</tr>
		<tr>
			<td>Polytetrafluoroethylene (PTFE) film</td>
			<td>Dupont</td>
			<td>200A Teflon FEP Film</td>
			<td></td>
		</tr>
		<tr>
			<td>Millex-HV Syringe Filter Unit, 0.45&#160;&#181;m, PVDF, 33&#160;mm, gamma sterilized</td>
			<td>Millipore</td>
			<td>SLHV033RS</td>
			<td></td>
		</tr>
		<tr>
			<td>Millex-GV Syringe Filter Unit, 0.22&#160;&#181;m, PVDF, 33&#160;mm, gamma sterilized</td>
			<td>Millipore</td>
			<td>SLGV033RS</td>
			<td></td>
		</tr>
		<tr>
			<td>Three-well glass dissection dish</td>
			<td>Any company</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Fine forceps, size 5, Dumont</td>
			<td>Fine Science Tools</td>
			<td>11254-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Tandem scanner inverted TCS SP5 confocal microscope, with resonant scanner and HyD photo-multiplier detectors</td>
			<td>Leica microsystem CMS GmbH</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Temperature control chamber</td>
			<td>Life Imaging Services</td>
			<td>The CUBE &#38; BOX temperature control system, custom designed</td>
			<td></td>
		</tr>
		<tr>
			<td>Stage-top humidity controller</td>
			<td>Life Imaging Services</td>
			<td>custom made</td>
			<td></td>
		</tr>
		<tr>
			<td>Water Immersion Micro Dispenser: dispenser, extended micro-pump MP6 series and Autoimmersion Objective Controller software</td>
			<td>Leica microsystem CMS GmbH</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>SUM-stack creation and 3D correction drift plugin</td>
			<td>ImageJ software</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>10x iterative deconvolution</td>
			<td>AutoQuant and Imaris software</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

single-cell resolution fluorescence live imaging of drosophila circadian clocks in larval brain culture

The circadian pacemaker circuit orchestrates rhythmic behavioral and physiological outputs coordinated with environmental cues, such as day/night cycles. The molecular clock within each pacemaker neuron generates circadian rhythms in gene expression, which underlie the rhythmic neuronal functions essential to the operation of the circuit. Investigation of the properties of the individual molecular oscillators in different subclasses of pacemaker neurons and their interaction with neuronal signaling yields a better understanding of the circadian pacemaker circuit. Here, we present a time-lapse fluorescent microscopy approach developed to monitor the molecular clockwork in clock neurons of cultured Drosophila larval brain. This method allows the multi-day recording of the rhythms of genetically encoded fluorescent circadian reporters at single-cell resolution. This setup can be combined with pharmacological manipulations to closely analyze real-time response of the molecular clock to various compounds. Beyond circadian rhythms, this multipurpose method in combination with powerful Drosophila genetic techniques offers the possibility to study diverse neuronal or molecular processes in live brain tissue.

Here, we show the representative results of the long-term recording of a circadian fluorescent reporter in ex vivo larval brain culture, and the live imaging results of PDF bath application on reporter expression.
Non-wandering L3 larvae expressing the molecular clock reporter PER-TDT and UAS-mCD8::YFP driven by a clock neuron driver Clk(856)-gal4 (Figure 1C) were entrained in LD. ...

Watch this Scientific Journal Video about Single-cell Resolution Fluorescence Live Imaging of Drosophila Circadian Clocks in Larval Brain Culture at JoVE.com

Single-cell Resolution Fluorescence Live Imaging of Drosophila Circadian Clocks in Larval Brain Culture

The goal of this protocol is to establish ex vivo Drosophila larval brain culture optimized to monitor circadian molecular rhythms with long-term fluorescence time-lapse imaging. The application of this method to pharmacological assays is also discussed.

Single-cell Resolution Fluorescence Live Imaging of Drosophila Circadian Clocks in Larval Brain Culture

The circadian pacemaker circuit orchestrates rhythmic behavioral and physiological outputs coordinated with environmental cues, such as day/night cycles. ...

The overall goal of this procedure is to culture Drosophila larval brains for multi-day time-lapse fluorescence microscopy. This method can help answer key questions in the field of Drosophila neurogenetics, such as gene expression changes that occur in specific neuronal populations. The main advantage of this technique is that it enables the imaging of fluorescent probes at single cell resolution in live brain over the course of hours to days.When preparing the reagents for this procedure, work under a culture hood. Both an aliquot of SAM medium and of thrombin must be thawed to begin. Set aside the thrombin.Take a 2.5 milliliter aliquot of SAM, and put the remaining SAM on ice and set it aside. Then put penicillin streptomycin in the aliquoted SAM and keep it at room temperature. For long-term imaging experiments, prepare an imagining chamber, apply autoclaved vacuum grease to the plastic regions around the well of a glass bottom dish.Then sterilize the greased dish with UV light under the hood. Now, mix an aliquot of SAM into the fibrinogen and transfer the mixture to 37 degrees Celsius, where it won't polymerize for two hours. For the dissection, clean the forceps in two three-well glass dissection dishes with 70%ethanol.Then load four wells with 400 microliters of DSS, and one well with 400 microliters of SAM. Keep the dissection dishes on a chilled plate. From a vial of propagating flies, scoop out some medium containing non-wandering third instar larvae, and transfer up to seven with forceps to a well of cold DSS.Then, pass the larvae through three of the four DSS-loaded wells to clean them off. Leave them in the final well until dissected. Use the fourth well of DSS to dissect the larval brains with a pair of clean fine forceps.Use the well established inside-out method. With proficiency each larvae can be processed in about 30 seconds. After each dissection, use a 20 microliter pipet tip pre-rinsed with DSS to transfer the brain in about three microliters of DSS to the SAM filled well.Prepare up to seven brains for the embedding procedure. After transferring the brain into working solution, dispense the brain and medium onto the lid of a sterile petri dish. Then, add another 3.5 microliters of SAM with antibiotics, and add 3.5 microliters of warm SAM with fibrinogen.It is important to maintain the SAM medium with fibrinogen at 37 degrees throughout the procedure. Next, mix the solution around the brain by gently pipetting with the same pipet tip and aspirate two microliters of the solution to deposit on a coverslip for a glass bottom dish. Then add 0.8 microliters of thrombin to the droplet and mix very quickly to initialize the polymerization which will appear white.Then, use forceps to gently pick the brain and set it onto the polymerizing fibrin matrix. I think the thrombin, after the brain was transferred to the droplet, it's not recommended, as it complicates a lot of the procedure. Orient the brain as needed, and very gently push the brain as close to the coverslip as possible.Then pick a layer of polymerized fibrin and fold it on top of the brain using small and gentle movements that do not detach the matrix. Continue to fold layers of polymerized fibrin over the brain from different parts of the clot to stabilize the brain. Then deposit 20 microliters of SAM with antibiotics over the embedded brain to halt the thrombin activity.Using this procedure, proceed with embedding five to six brains on a glass bottom dish. For long-term imaging, immerse the embedded brains in 600 microliters of SAM with antibiotics. Then lay a piece of PTFE membrane over the medium and stick the edges of the membrane to the greased parts of the dish.For short assays, fill the dish with two milliliters of SAM with antibiotics, immersing the brains and omit the use of the PTFE membrane. Using the described procedures, brains expressing a molecular clock reporter driven by a clock neuron driver, were entrained in light-dark then prepared as explant cultures. The long-term cultures were set up during the light phase, just prior to dark.A SUM-stack containing the neuron of interest was created in the mean fluorescence intensity of the area corresponding to the neuron was measured after background subtraction. To determine rhythmicity of the reporter expression, both maximum entropy spectral analysis and manual inspection were used. Next, larvae of the same genotype were dissected either one hour after subjective dawn, or one hour after subjective dusk.The brains were imaged twice within an hour to get a baseline. Then, PDF or vehicle was added to the culture medium and the brains were imaged hourly for six hours. In brains harvested shortly after dark, the PER-TDT expression profile in LNvs showed a time of day-dependent increase in fluorescence intensity upon PDF addition.This also occurred in the DN1s and to a lesser extent on the DN2s. After watching this video, you should have a good understanding of how to make ex vivo brain culture from Drosophila larvae using a 3D matrix of fibrin. Once mastered, the whole procedure takes about 30 minutes, from dissection to embedding.Prior to starting the dissections, prepare the imaging setup so the brain can be imaged immediately after embedding. Following this procedure, adult Drosophila brains can be also cultured for fluorescence time-lapse imaging in order to answer additional questions.

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7.4K ビュー.  University of Geneva. The overall goal of this procedure is to culture Drosophila larval brains for multi-day time-lapse fluorescence microscopy. This method can help answer key questions in the field of Drosophila neurogenetics, such as gene expression changes that occur in specific neuronal populations. The main advantage of this technique is that it enables the imaging of fluorescent probes at single cell resolution in live brain over the course of hours to days.When preparing the reagents for this proce...

ビデオ: Single-cell Resolution Fluorescence Live Imaging of Drosophila Circadian Clocks in Larval Brain Culture

Visualization of Larval Segmental Nerves in 3rd Instar Drosophila Larval Preparations

Drosophila melanogaster is emerging as a powerful model system for studying the development and function of the nervous system, particularly because of its convenient genetics and fully sequenced genome. Additionally, the larval nervous system is an ideal model system to study mechanisms of axonal transport as the larval segmental nerves contain bundles of axons with their cell bodies located within the brain and their nerve terminals ending along the length of the body. Here we describe the procedure for visualization of synaptic vesicle proteins within larval segmental nerves. If done correctly, all components of the nervous system, along with associated tissues such as muscles and NMJs, remain intact, undamaged, and ready to be visualized. 3rd instar larvae carrying various mutations are dissected, fixed, incubated with synaptic vesicle antibodies, visualized and compared to wild type larvae. This procedure can be adapted for several different synaptic or neuronal antibodies and changes in the distribution of a variety of proteins can be easily observed within larval segmental nerves.

Visualization of Larval Segmental Nerves in 3rd Instar Drosophila Larval Preparations

Drosophila melanogaster larvae provide an ideal model system to investigate the mechanisms of axonal transport within larval segmental nerves. Using this procedure, 3rd instar larvae carrying various mutations can be compared to wild type larvae.

Drosophila melanogaster is emerging as a powerful model system for studying the development and function of the nervous system, particularly because of ...

Live-cell Imaging of Sensory Organ Precursor Cells in Intact Drosophila Pupae

Since the discovery of Green Fluorescent Protein (GFP), there has been a revolutionary change in the use of live-cell imaging as a tool for understanding fundamental biological mechanisms. Striking progress has been particularly evident in Drosophila, whose extensive toolkit of mutants and transgenic lines provides a convenient model to study evolutionarily-conserved developmental and cell biological mechanisms. We are interested in understanding the mechanisms that control cell fate specification in the adult peripheral nervous system (PNS) in Drosophila. Bristles that cover the head, thorax, abdomen, legs and wings of the adult fly are individual mechanosensory organs, and have been studied as a model system for understanding mechanisms of Notch-dependent cell fate decisions. Sensory organ precursor (SOP) cells of the microchaetes (or small bristles), are distributed throughout the epithelium of the pupal thorax, and are specified during the first 12 hours after the onset of pupariation. After specification, the SOP cells begin to divide, segregating the cell fate determinant Numb to one daughter cell during mitosis. Numb functions as a cell-autonomous inhibitor of the Notch signaling pathway.
Here, we show a method to follow protein dynamics in SOP cell and its progeny within the intact pupal thorax using a combination of tissue-specific Gal4 drivers and GFP-tagged fusion proteins 1,2.This technique has the advantage over fixed tissue or cultured explants because it allows us to follow the entire development of an organ from specification of the neural precursor to growth and terminal differentiation of the organ. We can therefore directly correlate changes in cell behavior to changes in terminal differentiation. Moreover, we can combine the live imaging technique with mosaic analysis with a repressible cell marker (MARCM) system to assess the dynamics of tagged proteins in mitotic SOPs under mutant or wildtype conditions. Using this technique, we and others have revealed novel insights into regulation of asymmetric cell division and the control of Notch signaling activation in SOP cells (examples include references 1-6,7 ,8).

Live-cell Imaging of Sensory Organ Precursor Cells in Intact Drosophila Pupae

In this video, we describe a method for live cell imaging of asymmetrically dividing sensory organ progenitor cells and epidermal cells in intact Drosophila pupae

Since the discovery of Green Fluorescent Protein (GFP), there has been a revolutionary change in the use of live-cell imaging as a tool for understanding ...

A Rapid Approach to High-Resolution Fluorescence Imaging in Semi-Thick Brain Slices

A fundamental goal to both basic and clinical neuroscience is to better understand the identities, molecular makeup, and patterns of connectivity that are characteristic to neurons in both normal and diseased brain. Towards this, a great deal of effort has been placed on building high-resolution neuroanatomical maps1-3. With the expansion of molecular genetics and advances in light microscopy has come the ability to query not only neuronal morphologies, but also the molecular and cellular makeup of individual neurons and their associated networks4. Major advances in the ability to mark and manipulate neurons through transgenic and gene targeting technologies in the rodent now allow investigators to 'program' neuronal subsets at will5-6. Arguably, one of the most influential contributions to contemporary neuroscience has been the discovery and cloning of genes encoding fluorescent proteins (FPs) in marine invertebrates7-8, alongside their subsequent engineering to yield an ever-expanding toolbox of vital reporters9. Exploiting cell type-specific promoter activity to drive targeted FP expression in discrete neuronal populations now affords neuroanatomical investigation with genetic precision.
Engineering FP expression in neurons has vastly improved our understanding of brain structure and function. However, imaging individual neurons and their associated networks in deep brain tissues, or in three dimensions, has remained a challenge. Due to high lipid content, nervous tissue is rather opaque and exhibits auto fluorescence. These inherent biophysical properties make it difficult to visualize and image fluorescently labelled neurons at high resolution using standard epifluorescent or confocal microscopy beyond depths of tens of microns. To circumvent this challenge investigators often employ serial thin-section imaging and reconstruction methods10, or 2-photon laser scanning microscopy11. Current drawbacks to these approaches are the associated labor-intensive tissue preparation, or cost-prohibitive instrumentation respectively.
Here, we present a relatively rapid and simple method to visualize fluorescently labelled cells in fixed semi-thick mouse brain slices by optical clearing and imaging. In the attached protocol we describe the methods of: 1) fixing brain tissue in situ via intracardial perfusion, 2) dissection and removal of whole brain, 3) stationary brain embedding in agarose, 4) precision semi-thick slice preparation using new vibratome instrumentation, 5) clearing brain tissue through a glycerol gradient, and 6) mounting on glass slides for light microscopy and z-stack reconstruction (Figure 1).
For preparing brain slices we implemented a relatively new piece of instrumentation called the 'Compresstome' VF-200 (http://www.precisionary.com/products_vf200.html). This instrument is a semi-automated microtome equipped with a motorized advance and blade vibration system with features similar in function to other vibratomes. Unlike other vibratomes, the tissue to be sliced is mounted in an agarose plug within a stainless steel cylinder. The tissue is extruded at desired thicknesses from the cylinder, and cut by the forward advancing vibrating blade. The agarose plug/cylinder system allows for reproducible tissue mounting, alignment, and precision cutting. In our hands, the 'Compresstome' yields high quality tissue slices for electrophysiology, immunohistochemistry, and direct fixed-tissue mounting and imaging. Combined with optical clearing, here we demonstrate the preparation of semi-thick fixed brain slices for high-resolution fluorescent imaging.

Here we describe a rapid and simple method to image fluorescently labeled cells in semi-thick brain slices. By fixing, slicing, and optically clearing brain tissue we describe how standard epifluorescent or confocal imaging can be used to visualize individual cells and neuronal networks within intact nervous tissue.

A fundamental goal to both basic and clinical neuroscience is to better understand the identities, molecular makeup, and patterns of connectivity that are ...

Morphological Analysis of Drosophila Larval Peripheral Sensory Neuron Dendrites and Axons Using Genetic Mosaics

Nervous system development requires the correct specification of neuron position and identity, followed by accurate neuron class-specific dendritic development and axonal wiring. Recently the dendritic arborization (DA) sensory neurons of the Drosophila larval peripheral nervous system (PNS) have become powerful genetic models in which to elucidate both general and class-specific mechanisms of neuron differentiation.
There are four main DA neuron classes (I-IV)1. They are named in order of increasing dendrite arbor complexity, and have class-specific differences in the genetic control of their differentiation2-10. The DA sensory system is a practical model to investigate the molecular mechanisms behind the control of dendritic morphology11-13 because: 1) it can take advantage of the powerful genetic tools available in the fruit fly, 2) the DA neuron dendrite arbor spreads out in only 2 dimensions beneath an optically clear larval cuticle making it easy to visualize with high resolution in vivo, 3) the class-specific diversity in dendritic morphology facilitates a comparative analysis to find key elements controlling the formation of simple vs. highly branched dendritic trees, and 4) dendritic arbor stereotypical shapes of different DA neurons facilitate morphometric statistical analyses.
DA neuron activity modifies the output of a larval locomotion central pattern generator14-16. The different DA neuron classes have distinct sensory modalities, and their activation elicits different behavioral responses14,16-20. Furthermore different classes send axonal projections stereotypically into the Drosophila larval central nervous system in the ventral nerve cord (VNC)21. These projections terminate with topographic representations of both DA neuron sensory modality and the position in the body wall of the dendritic field7,22,23. Hence examination of DA axonal projections can be used to elucidate mechanisms underlying topographic mapping7,22,23, as well as the wiring of a simple circuit modulating larval locomotion14-17.
We present here a practical guide to generate and analyze genetic mosaics24 marking DA neurons via MARCM (Mosaic Analysis with a Repressible Cell Marker)1,10,25 and Flp-out22,26,27 techniques (summarized in Fig. 1).

Morphological Analysis of Drosophila Larval Peripheral Sensory Neuron Dendrites and Axons Using Genetic Mosaics

The dendritic arborization sensory neurons of the Drosophila larval peripheral nervous system are useful models to elucidate both general and neuron class-specific mechanisms of neuron differentiation. We present a practical guide to generate and analyze dendritic arborization neuron genetic mosaics.

Nervous system development requires the correct specification of neuron position and identity, followed by accurate neuron class-specific dendritic ...

Non-Laser Capture Microscopy Approach for the Microdissection of Discrete Mouse Brain Regions for Total RNA Isolation and Downstream Next-Generation Sequencing and Gene Expression Profiling

As technological platforms, approaches such as next-generation sequencing, microarray, and qRT-PCR have great promise for expanding our understanding of the breadth of molecular regulation. Newer approaches such as high-resolution RNA sequencing (RNA-Seq)1 provides new and expansive information about tissue- or state-specific expression such as relative transcript levels, alternative splicing, and micro RNAs2-4. Prospects for employing the RNA-Seq method in comparative whole transcriptome profiling5 within discrete tissues or between phenotypically distinct groups of individuals affords new avenues for elucidating molecular mechanisms involved in both normal and abnormal physiological states. Recently, whole transcriptome profiling has been performed on human brain tissue, identifying gene expression differences associated with disease progression6. However, the use of next-generation sequencing has yet to be more widely integrated into mammalian studies.
Gene expression studies in mouse models have reported distinct profiles within various brain nuclei using laser capture microscopy (LCM) for sample excision7,8. While LCM affords sample collection with single-cell and discrete brain region precision, the relatively low total RNA yields from the LCM approach can be prohibitive to RNA-Seq and other profiling approaches in mouse brain tissues and may require sub-optimal sample amplification steps. Here, a protocol is presented for microdissection and total RNA extraction from discrete mouse brain regions. Set-diameter tissue corers are used to isolate 13 tissues from 750-&mu;m serial coronal sections of an individual mouse brain. Tissue micropunch samples are immediately frozen and archived. Total RNA is obtained from the samples using magnetic bead-enabled total RNA isolation technology. Resulting RNA samples have adequate yield and quality for use in downstream expression profiling. This microdissection strategy provides a viable option to existing sample collection strategies for obtaining total RNA from discrete brain regions, opening possibilities for new gene expression discoveries.

Non-Laser Capture Microscopy Approach for the Microdissection of Discrete Mouse Brain Regions for Total RNA Isolation and Downstream Next-Generation Sequencing and Gene Expression Profiling  |

RNA expression profiling of discrete mouse brain regions requires a precise and repeatable tissue collection strategy. A protocol that uses both coronal brain sectioning and tissue corer-assisted microdissection is described here. The yield and quality of total RNA obtained from the resulting samples confirms the utility of the outlined method.

As technological platforms, approaches such as next-generation sequencing, microarray, and qRT-PCR have great promise for expanding our understanding of ...

High-resolution Live Imaging of Cell Behavior in the Developing Neuroepithelium

The embryonic spinal cord consists of cycling neural progenitor cells that give rise to a large percentage of the neuronal and glial cells of the central nervous system (CNS). Although much is known about the molecular mechanisms that pattern the spinal cord and elicit neuronal differentiation1, 2, we lack a deep understanding of these early events at the level of cell behavior. It is thus critical to study the behavior of neural progenitors in real time as they undergo neurogenesis.
In the past, real-time imaging of early embryonic tissue has been limited by cell/tissue viability in culture as well as the phototoxic effects of fluorescent imaging. Here we present a novel assay for imaging such tissue for long periods of time, utilizing a novel ex vivo slice culture protocol and wide-field fluorescence microscopy (Fig. 1). This approach achieves long-term time-lapse monitoring of chick embryonic spinal cord progenitor cells with high spatial and temporal resolution.
This assay may be modified to image a range of embryonic tissues3, 4 In addition to the observation of cellular and sub-cellular behaviors, the development of novel and highly sensitive reporters for gene activity (for example, Notch signaling5) makes this assay a powerful tool with which to understand how signaling regulates cell behavior during embryonic development.

Imaging embryonic tissue in real-time is challenging over long periods of time. Here we present an assay for monitoring cellular and sub-cellular changes in chick spinal cord for long periods with high spatial and temporal resolution. This technique can be adapted for other regions of the nervous system and developing embryo.

The embryonic spinal cord consists of cycling neural progenitor cells that give rise to a large percentage of the neuronal and glial cells of the central ...

Ex vivo Live Imaging of Single Cell Divisions in Mouse Neuroepithelium

We developed a system that integrates live imaging of fluorescent markers and culturing slices of embryonic mouse neuroepithelium. We took advantage of existing mouse lines for genetic cell lineage tracing: a tamoxifen-inducible Cre line and a Cre reporter line expressing dsRed upon Cre-mediated recombination. By using a relatively low level of tamoxifen, we were able to induce recombination in a small number of cells, permitting us to follow individual cell divisions. Additionally, we observed the transcriptional response to Sonic Hedgehog (Shh) signaling using an Olig2-eGFP transgenic line 1-3 and we monitored formation of cilia by infecting the cultured slice with virus expressing the cilia marker, Sstr3-GFP 4. In order to image the neuroepithelium, we harvested embryos at E8.5, isolated the neural tube, mounted the neural slice in proper culturing conditions into the imaging chamber and performed time-lapse confocal imaging. Our ex vivo live imaging method enables us to trace single cell divisions to assess the relative timing of primary cilia formation and Shh response in a physiologically relevant manner. This method can be easily adapted using distinct fluorescent markers and provides the field the tools with which to monitor cell behavior in situ and in real time.

Ex vivo Live Imaging of Single Cell Divisions in Mouse Neuroepithelium

Here we develop the tools necessary for ex vivo live imaging to trace single cell divisions in the mouse E8.5 neuroepithelium

We developed a system that integrates live imaging of fluorescent markers and culturing slices of embryonic mouse neuroepithelium. We took advantage of ...

Functional Analysis of the Larval Feeding Circuit in Drosophila

The serotonergic feeding circuit in Drosophila melanogaster larvae can be used to investigate neuronal substrates of critical importance during the development of the circuit. Using the functional output of the circuit, feeding, changes in the neuronal architecture of the stomatogastric system can be visualized. Feeding behavior can be recorded by observing the rate of retraction of the mouth hooks, which receive innervation from the brain. Locomotor behavior is used as a physiological control for feeding, since larvae use their mouth hooks to traverse across an agar substrate. Changes in feeding behavior can be correlated with the axonal architecture of the neurites innervating the gut. Using immunohistochemistry it is possible to visualize and quantitate these changes. Improper handling of the larvae during behavior paradigms can alter data as they are very sensitive to manipulations. Proper imaging of the neurite architecture innervating the gut is critical for precise quantitation of number and size of varicosities as well as the extent of branch nodes. Analysis of most circuits allow only for visualization of neurite architecture or behavioral effects; however, this model allows one to correlate the functional output of the circuit with the impairments in neuronal architecture.

Functional Analysis of the Larval Feeding Circuit in Drosophila

The feeding circuit in Drosophila melanogaster larvae serves a simple yet powerful model that allows changes in feeding rate to be correlated with alterations in the stomatogastric neural circuitry. This circuit is composed of central serotonergic neurons that send projections to the mouth hooks as well as the foregut.

The serotonergic  feeding circuit in Drosophila  melanogaster larvae can be used to investigate neuronal substrates of  critical importance during the ...

Live Imaging of Mitosis in the Developing Mouse Embryonic Cortex

Although of short duration, mitosis is a complex and dynamic multi-step process fundamental for development of organs including the brain. In the developing cerebral cortex, abnormal mitosis of neural progenitors can cause defects in brain size and function. Hence, there is a critical need for tools to understand the mechanisms of neural progenitor mitosis. Cortical development in rodents is an outstanding model for studying this process. Neural progenitor mitosis is commonly examined in fixed brain sections. This protocol will describe in detail an approach for live imaging of mitosis in ex vivo embryonic brain slices. We will describe the critical steps for this procedure, which include: brain extraction, brain embedding, vibratome sectioning of brain slices, staining and culturing of slices, and time-lapse imaging. We will then demonstrate and describe in detail how to perform post-acquisition analysis of mitosis. We include representative results from this assay using the vital dye Syto11, transgenic mice (histone H2B-EGFP and centrin-EGFP), and in utero electroporation (mCherry-&#945;-tubulin). We will discuss how this procedure can be best optimized and how it can be modified for study of genetic regulation of mitosis. Live imaging of mitosis in brain slices is a flexible approach to assess the impact of age, anatomy, and genetic perturbation in a controlled environment, and to generate a large amount of data with high temporal and spatial resolution. Hence this protocol will complement existing tools for analysis of neural progenitor mitosis.

Neural progenitor mitosis is a critical parameter of neurogenesis. Much of our understanding of neural progenitor mitosis is based on analysis of fixed tissue. Live imaging in embryonic brain slices is a versatile technique to assess mitosis with high temporal and spatial resolution in a controlled environment.

Although of short duration, mitosis is a complex and dynamic multi-step process fundamental for development of organs including the brain. In the ...

Live Imaging of Drosophila Larval Neuroblasts

Stem cells divide asymmetrically to generate two progeny cells with unequal fate potential: a self-renewing stem cell and a differentiating cell. Given their relevance to development and disease, understanding the mechanisms that govern asymmetric stem cell division has been a robust area of study. Because they are genetically tractable and undergo successive rounds of cell division about once every hour, the stem cells of the Drosophila central nervous system, or neuroblasts, are indispensable models for the study of stem cell division. About 100 neural stem cells are located near the surface of each of the two larval brain lobes, making this model system particularly useful for live imaging microscopy studies. In this work, we review several approaches widely used to visualize stem cell divisions, and we address the relative advantages and disadvantages of those techniques that employ dissociated versus intact brain tissues. We also detail our simplified protocol used to explant whole brains from third instar larvae for live cell imaging and fixed analysis applications.

Live Imaging of Drosophila Larval Neuroblasts

This protocol details a streamlined method used to conduct live cell imaging in the context of an intact larval brain. Live cell imaging approaches are invaluable for the study of asymmetric neural stem cell divisions as well as other neurogenic and developmental processes, consistently uncovering mechanisms that were previously overlooked.

Stem cells divide asymmetrically to generate two progeny cells with unequal fate potential: a self-renewing stem cell and a differentiating cell. Given ...