We would like to thank all the members of our lab for their advice, useful discussions and comments on the manuscript. We would also particularly like to thank Marta Koch and Bassem Hassan for the excellent suggestion that we wait until 1.5 hours APF before dissecting brains for culturing in remodeling experiments. We also thank the NHGRI imaging facility for the use of their confocal microscope. This work was supported by the Basic Neuroscience Program of the NINDS Intramural Research Program, NIH (Z01 NS003106).

A. Preparation of Media
<ol>
	<li>Prepare complete media by filter-sterilizing Schneider's Drosophila Media supplemented with 10% Fetal Bovine Serum and 1% penicillin/streptomycin.</li>
	<li>Media should be prepared fresh each time. Alternatively, a fresh aliquot of pre-frozen media can be thawed before each use.</li>
	<li>Prior to culturing, add 10 &mu;g/ml insulin and 2 &mu;g/ml ecdysone to the media. Drugs were prepared as concentrated stocks and frozen in small aliquots. Thawed aliquots were not refrozen.</li>
	<li>All working solutions should be maintained at 25 &deg;C.</li>
</ol>
Culturing of Larval Brains
1. Selection and Dissection of Larval Brains
<ol>
	<li>Add 500 &mu;l of media to a 12 mm Millicell cell culture insert. The dissected brains will be placed in these inserts to facilitate easy immunostaining.</li>
	<li>Add a small amount of prepared media to a dissection watch glass.</li>
	<li>Using a small spatula, pick up wandering third instar larvae and place them in the watch glass. (We presume that the ex vivo culture method would apply equally well to first or second instar larvae, but we have not tested this.)</li>
	<li>Holding the posterior end of the larva with a pair of forceps, carefully open up the anterior end with a second pair of #5 forceps.</li>
	<li>Quickly dissect out the brain, keeping the ventral nerve cord intact.</li>
</ol>
2. Ex vivo culturing of Dissected Larval Brains
<ol>
	<li>Using pre-wet pipette tips, transfer the brain carefully into the cell culture inserts, pre-filled with media.</li>
	<li>Transfer brains, in media, to an incubator at 25 &deg;C till the desired time-point is reached. This method works efficiently for up to 48 hr in culture.</li>
	<li>Replace the media at 8 hours. Beyond that, replace half of the media every 5-6 hours.</li>
</ol>
3. Pharmacological Manipulation of Larval Brains
This method of ex vivo culturing can be used to pharmacologically corroborate genetic interactions previously demonstrated in our lab 1.
<ol>
	<li>Add 100 &mu;M roscovitine and 100 &mu;M olomoucine to prepared media.</li>
	<li>Transfer dissected brains to this media.</li>
	<li>Culture brains at 25 &deg;C for 24 hours.</li>
	<li>Replace the media at 8 hours. Beyond that, replace half of the media (with drugs) every 5-6 hours.</li>
</ol>
Culturing of Pupal Brains
1. Selection of Pupae for Dissection
<ol>
	<li>Mark white pupae on bottles/vials.</li>
	<li>Only choose pupae that are completely white. Pupae with any sort of coloration should not be included.</li>
	<li>This stage is 0 hours After Puparium Formation (APF).</li>
	<li>These pupae will be ready for dissection 1.5 hours after marking. This step is crucial to ensure that developmental pruning occurs in ex vivo culture.</li>
</ol>
2. Dissection of Pupae
<ol>
	<li>Add 500 &mu;l of media to a 12 mm Millicell cell culture insert. (The dissected brains will be placed in these inserts to facilitate easy immunostaining).</li>
	<li>Once the desired time-point has been reached, add a small amount of prepared media to a dissection watch glass.</li>
	<li>Using a small, wet spatula, pick up pupae previously marked for dissection and place them in the watch glass.</li>
	<li>Holding the posterior end of the pupae with a pair of forceps, carefully open the anterior end of the pupa case with a second pair of #5 forceps.</li>
	<li>Quickly dissect out the brain, keeping the ventral nerve cord intact and attached.</li>
</ol>
3. Ex vivo Culturing of Dissected Pupal Brains
<ol>
	<li>Transfer the brain carefully into the cell culture inserts, pre-filled with media.</li>
	<li>Transfer brains, in media, to an incubator at 25 &deg;C till the desired time-point is reached. We used this method for up to 10 hours in culture for the experiment shown, but it can be extended to longer periods of observation and treatment, if needed.</li>
	<li>For time-points longer than 8 hours APF, replace media every 5-6 hours.</li>
</ol>
From this step on, the protocol remains unchanged for both larvae and pupae.
B. Fixing Dissected Brains
<ol>
	<li>Once the desired time-point is reached, remove media and add 500 &mu;l of 4% formaldehyde in 1x PBS with 0.5% Triton X-100 (PBST) for 30 minutes, replacing with fresh formaldehyde after 15 minutes.</li>
	<li>Make sure not to allow brains to dry while replacing media with fixative.</li>
	<li>Wash off formaldehyde with four 10 minute washes of 1x PBS with 0.5% TritonX-100 (PBST).</li>
</ol>
C. Staining Fixed Brains
<ol>
	<li>After formaldehyde has been washed off, block brains for 1 hour in a blocking solution of 1x PBS with 1% Normal Goat Serum and 1% Bovine Serum Albumin.</li>
	<li>Add primary antibodies made up in blocking solution.</li>
	<li>Incubate brains overnight at 4 &deg;C.</li>
	<li>The next morning, wash off primary antibodies with four 10 minute washes of PBST.</li>
	<li>Add secondary antibodies made up in blocking solution.</li>
	<li>Leave at room temperature for 4 hours.</li>
	<li>Wash off secondary antibodies with four 10 minute washes of PBST.</li>
</ol>
D. Mounting Fixed and Stained Brains for Microscopy
<ol>
	<li>Equilibrate brains in Vectashield mounting media for 1 hour.</li>
	<li>Mount brains on glass slides using the Vectashield mounting media.</li>
	<li>Place glass chips on either side of the brains before mounting the cover slip. This prevents the brains from being squashed, while keeping sample thin enough to scan all focal planes with a confocal microscope. Brains were roughly oriented upon mounting to facilitate viewing the features of interest. When necessary, brain images were rotated with Imaris software to provide an optimal view for documentation and measurement.</li>
	<li>Seal cover slips with clear nail polish.</li>
	<li>Store slides away from light.</li>
</ol>
E. Representative Results
Figure 1 shows a panel of third-instar larval brains of (A) wild-type flies and (B) flies that express a dominant-negative derivative of Cdk5 (Cdk5DN) (Connell-Crowley et al., 2000). Both express actin-GFP (green) in MB gamma neurons. As described previously (Trunova et al., 2011), there is a region in the proximal axons of wild-type gamma neurons that fails to accumulate actin-GFP, thus showing up as a "clear zone" (A, bracket), and fasciclin 2 protein (red) accumulates in the axons only up to the ventral border of this zone (white horizontal line). The dotted line in the third panel of Figure 1(A) indicates the position of the MB, highlighting the actin "clear zone" and its ventral border. In flies expressing Cdk5DN, the actin clear zone is absent (B) and Fasciclin 2 (FasII) immunoreactivity spreads dorsally through that region. (Note that variable numbers of FasII-positive axons project horizontally across the MB; these are not relevant to the phenotype). Scale bar represents 20 &mu;m.
Using our method of ex vivo culturing, we treated wild-type flies with a combination of roscovitine and olomoucine, pharmacological inhibitors of Cdk5 activity. Figure 2 shows a panel of third-instar larval brains of control (A) and drug-treated (B) wild-type flies. Similar to flies expressing a dominant negative Cdk5 construct, brains treated with Cdk5 inhibitors for 24 hours, show the characteristic loss of actin clear zone and shift in FasII boundary (square brackets). White lines show position of wild-type FasII boundary. Scale bar represents 20 &mu;m.
Figure 3 shows a representative series of Drosophila mushroom bodies from 0-10 hours APF, labeled with membrane-targeted mCD8-GFP (green). Brackets indicate the calyx, that is, the dendritic projections of the MB. Prior to metamorphosis, one can see MB axons coursing dorso-ventrally in thick bundles, as well as a 'haze' of fluorescent signal arising from the dense dendritic arbor (bracket). Panel A shows brains dissected at the time indicated. Note the pruning of dendrites in the region indicated by the brackets, such that by 6-8 hrs APF, the haze of dendritic signal is gone (though the axonal signal is unaffected). Brains in panel B were dissected at 0 hours APF, before the internal ecdysone spike (Truman and Riddiford, 2002), and cultured ex vivo as indicated. These show no developmental pruning of dendrites; rather the dendritic signal persists at 10 hrs APF. To circumvent this, pupae are marked at 0 hours APF, but dissected at 1.5 hours APF and cultured. Panel C shows a representative series of these Drosophila mushroom bodies from 0-10 hours APF. As in the non-cultured samples, dendritic signal is undetectable by 8 hr APF. Scale bar represents 20 &mu;m.

<ol>
	<li>Trunova, S., Baek, B., 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=Cdk5+regulates+the+size+of+an+axon+initial+segment-like+compartment+in+mushroom+body+neurons+of+the+Drosophila+central+brain.">Cdk5 regulates the size of an axon initial segment-like compartment in mushroom body neurons of the Drosophila central brain.</a> J. Neurosci. 31 (29), 10451-10462 (2011).</li><li>Nakada, 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=Accumulation+of+anchored+proteins+forms+membrane+diffusion+barriers+during+neuronal+polarization.">Accumulation of anchored proteins forms membrane diffusion barriers during neuronal polarization.</a> Nat. Cell Biol. 5 (7), 626-632 (2003).</li><li>Schmid, G., Strosznajder, J. B., Wesierska-Gadek, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interplay+between+the+p53+tumor+suppressor+protein+family+and+Cdk5:+novel+therapeutic+approaches+for+the+treatment+of+neurodegenerative+disease+using+selective+Cdk+inhibitors.">Interplay between the p53 tumor suppressor protein family and Cdk5: novel therapeutic approaches for the treatment of neurodegenerative disease using selective Cdk inhibitors.</a> Mol Neurobiol. 34 (1), 27-50 (2006).</li><li>Kahsai, L., Zars, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Learning+and+memory+in+Drosophila:+behavior,+genetics,+and+neural+system.">Learning and memory in Drosophila: behavior, genetics, and neural system.</a> Int. Rev. Neurobiol. 99, 139-167 (2011).</li><li>Lee, T., Lee, A., 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=Development+of+the+Drosophila+mushroom+bodies:+sequential+generation+of+three+distinct+types+of+neurons+from+a+neuroblast.">Development of the Drosophila mushroom bodies: sequential generation of three distinct types of neurons from a neuroblast.</a> Development. 126, 4065-4076 (1999).</li><li>Watts, R. J., Hoopfer, E. D., 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=Axon+pruning+during+Drosophila+metamorphosis:+evidence+for+local+degeneration+and+requirement+of+the+ubiquitin-proteasome+system.">Axon pruning during Drosophila metamorphosis: evidence for local degeneration and requirement of the ubiquitin-proteasome system.</a> Neuron. 38 (6), 871-885 (2003).</li><li>Lee, T., Marticke, S., Sung, C., Robinow, 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=Cell-autonomous+requirement+of+the+USP/EcR-B+ecdysone+receptor+for+mushroom+body+neuronal+remodeling+in+Drosophila.">Cell-autonomous requirement of the USP/EcR-B ecdysone receptor for mushroom body neuronal remodeling in Drosophila.</a> Neuron. 28 (3), 807-818 (2000).</li><li>Connell-Crowley, L., Le Gall, M., Vo, D. J., 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=The+cyclin-dependent+kinase+Cdk5+controls+multiple+aspects+of+axon+patterning+in+vivo.">The cyclin-dependent kinase Cdk5 controls multiple aspects of axon patterning in vivo.</a> Curr. Biol. 10 (10), 599-602 (2000).</li><li>Truman, J. W., Riddiford, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endocrine+insights+into+the+evolution+of+metamorphosis+in+insects.">Endocrine insights into the evolution of metamorphosis in insects.</a> Annu. Rev. Entomol. 47, 467-500 (2002).</li><li>Noguchi, T., Miller, K. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+role+for+actin+dynamics+in+individualization+during+spermatogenesis+in+Drosophila+melanogaster.">A role for actin dynamics in individualization during spermatogenesis in Drosophila melanogaster.</a> Development. 130, 1805-1816 (2003).</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>Brown, H. L. D., Cherbas, L., Cherbas, P., Truman, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+time-lapse+imaging+and+dominant+negative+receptors+to+dissect+the+steroid+receptor+control+of+neuronal+remodeling+in+Drosophila.">Use of time-lapse imaging and dominant negative receptors to dissect the steroid receptor control of neuronal remodeling in Drosophila.</a> Development. 133, 275-288 (2006).</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), e1936 (2010).</li></ol>

No conflicts of interest declared.

Chronic genetic manipulations of tissue structure and function, including mutations and expression of transgenes, typically produce a combination of immediate effects and late indirect consequences that can be very difficult to separate. Complementing genetic methods with pharmacology can facilitate interrogation of the time course behind a phenotype. For example, this has been a powerful approach for dissecting the contributions of different cytoskeletal components during spermatogenesis in Drosophila <s...

<table border="1">
 <tbody>
 <tr>
 <td>Name of Reagent</td>
 <td>Company</td>
 <td>Catalog Number</td>
 <td>Final Concentration</td>
 </tr>
 <tr>
 <td>Schneider's Drosophila Media</td>
 <td>Invitrogen</td>
 <td>21720-024</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Fetal Bovine Serum (heat-inactivated)</td>
 <td>Invitrogen</td>
 <td>10082-147</td>
 <td>10% </td>
 </tr>
 <tr>
 <td>Penicillin/Streptomycin</td>
 <td>Invitrogen</td>
 <td>15140-122</td>
 <td>1% </td>
 </tr>
 <tr>
 <td>Insulin</td>
 <td>Invitrogen</td>
 <td>12585-014</td>
 <td>10&mu;g/ml </td>
 </tr>
 <tr>
 <td>Ecdysone</td>
 <td>Sigma-Aldrich</td>
 <td>H5142</td>
 <td>2&mu;g/ml </td>
 </tr>
 <tr>
 <td>Roscovitine</td>
 <td>Sigma-Aldrich</td>
 <td>R7772</td>
 <td>100&mu;M </td>
 </tr>
 <tr>
 <td>Olomoucine</td>
 <td>Sigma-Aldrich</td>
 <td>O0886</td>
 <td>100&mu;M </td>
 </tr>
 <tr>
 <td>Normal Goat Serum</td>
 <td>Invitrogen</td>
 <td>50062Z</td>
 <td>1% </td>
 </tr>
 <tr>
 <td>Bovine Serum Albumin</td>
 <td>Fisher Scientific</td>
 <td>M9501</td>
 <td>1% </td>
 </tr>
 <tr>
 <td>Formaldehyde</td>
 <td>Sigma-Aldrich</td>
 <td>D4551</td>
 <td>4% </td>
 </tr>
 <tr>
 <td>Triton-X 100</td>
 <td>Fisher Scientific</td>
 <td>BP151</td>
 <td>0.5% </td>
 </tr>
 <tr>
 <td>Phosphate Buffered Saline</td>
 <td>Invitrogen</td>
 <td>70011-044</td>
 <td>1X </td>
 </tr>
 <tr>
 <td>Vectashield</td>
 <td>Vector Laboratories</td>
 <td>H1000</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Millicell Cell Culture Inserts</td>
 <td>Millipore</td>
 <td>PI8P01250</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Multidish, 4 well</td>
 <td>Thermo Scientific</td>
 <td>176740</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Dumont #5 Forceps</td>
 <td>Fine Science Tools</td>
 <td>11251-20</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Microscope Slides</td>
 <td>Fisher Scientific</td>
 <td>12-544-7</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Cover Glass</td>
 <td>Fisher Scientific</td>
 <td>12-548-5M</td>
 <td>&nbsp;</td>
 </tr>
 </tbody>
 </table>

ex vivo culturing of whole, developing drosophila brains

We describe a method for ex vivo culturing of whole Drosophila brains. This can be used as a counterpoint to chronic genetic manipulations for investigating the cell biology and development of central brain structures by allowing acute pharmacological interventions and live imaging of cellular processes. As an example of the technique, prior work from our lab1 has shown that a previously unrecognized subcellular compartment lies between the axonal and somatodendritic compartments of axons of the Drosophila central brain. The development of this compartment, referred to as the axon initial segment (AIS)2, was shown genetically to depend on the neuron-specific cyclin-dependent kinase, Cdk5. We show here that ex vivo treatment of wild-type Drosophila larval brains with the Cdk5-specific pharmacological inhibitors roscovitine and olomoucine3 causes acute changes in actin organization, and in localization of the cell-surface protein Fasciclin 2, that mimic the changes seen in mutants that lack Cdk5 activity genetically.
A second example of the ex vivo culture technique is provided for remodeling of the connections of embryonic mushroom body (MB) gamma neurons during metamorphosis from larva to adult. The mushroom body is the center of olfactory learning and memory in the fly4, and these gamma neurons prune their axonal and dendritic branches during pupal development and then re-extend branches at a later timepoint to establish the adult innervation pattern5. Pruning of these neurons of the MB has been shown to occur via local degeneration of neurite branches6, by a mechanism that is triggered by ecdysone, a steroid hormone, acting at the ecdysone receptor B17, and that is dependent on the activity of the ubiquitin-proteasome system6. Our method of ex vivo culturing can be used to interrogate further the mechanism of developmental remodeling. We found that in the ex vivo culture setting, gamma neurons of the MB recapitulated the process of developmental pruning with a time course similar to that in vivo. It was essential, however, to wait until 1.5 hours after puparium formation before explanting the tissue in order for the cells to commit irreversibly to metamorphosis; dissection of animals at the onset of pupariation led to little or no metamorphosis in culture. Thus, with appropriate modification, the ex vivo culture approach can be applied to study dynamic as well as steady state aspects of central brain biology.

Watch this Scientific Journal Video about Ex vivo Culturing of Whole, Developing Drosophila Brains at JoVE.com

Ex vivo Culturing of Whole, Developing Drosophila Brains

This article describes a method by which one can mimic in vivo development of the Drosophila mushroom body in an ex vivo culture system.

Ex vivo Culturing of Whole, Developing Drosophila Brains

We describe a method for ex vivo culturing of whole Drosophila brains. This can be used as a counterpoint to chronic genetic manipulations for ...

ex-vivo-culturing-of-whole-developing-drosophila-brains

Research

JoVE Journal

Neuroscience

13.0K Views.  National Institute of Neurological Disorders and Stroke. This article describes a method by which one can mimic in vivo development of the Drosophila mushroom body in an ex vivo culture system.

Video: Ex vivo Culturing of Whole, Developing Drosophila Brains

In vivo Electroporation of Developing Mouse Retina

The functional characterization of genes expressed during mammalian retinal development remains a significant challenge. Gene targeting to generate constitutive or conditional loss of function knockouts remains cost and labor intensive, as well as time consuming. Adding to these challenges, retina expressed genes may have essential roles outside the retina leading to unintended confounds when using a knockout approach. Furthermore, the ability to ectopically express a gene in a gain of function experiment can be extremely valuable when attempting to identify a role in cell fate specification and/or terminal differentiation.
We present a method for the rapid and efficient incorporation of DNA plasmids into the neonatal mouse retina by electroporation. The application of short electrical impulses above a certain field strength results in a transient increase in plasma membrane permeability, facilitating the transfer of material across the membrane 1,2,3,4. Groundbreaking work demonstrated that electroporation could be utilized as a method of gene transfer into mammalian cells by inducing the formation of hydrophilic plasma membrane pores allowing the passage of highly charged DNA through the lipid bilayer 5. Continuous technical development has resulted in the viability of electroporation as a method for in vivo gene transfer in multiple mouse tissues including the retina, the method for which is described herein 6, 7, 8, 9, 10. 
DNA solution is injected into the subretinal space so that DNA is placed between the retinal pigmented epithelium and retina of the neonatal (P0) mouse and electrical pulses are applied using a tweezer electrode. The lateral placement of the eyes in the mouse allows for the easy orientation of the tweezer electrode to the necessary negative pole-DNA-retina-positive pole alignment. Extensive incorporation and expression of transferred genes can be identified by postnatal day 2 (P2). Due to the lack of significant lateral migration of cells in the retina, electroporated and non-electroporated regions are generated. Non-electroporated regions may serve as internal histological controls where appropriate. 
Retinal electroporation can be used to express a gene under a ubiquitous promoter, such as CAG, or to disrupt gene function using shRNA constructs or Cre-recombinase. More targeted expression can be achieved by designing constructs with cell specific gene promoters. Visualization of electroporated cells is achieved using bicistronic constructs expressing GFP or by co-electroporating a GFP expression construct. Furthermore, multiple constructs may be electroporated for the study of combinatorial gene effects or simultaneous gain and loss of function of different genes. Retinal electroporation may also be utilized for the analysis of genomic cis-regulatory elements by generating appropriate expression constructs and deletion mutants. Such experiments can be used to identify cis-regulatory regions sufficient or required for cell specific gene expression 11. Potential experiments are limited only by construct availability.

In vivo Electroporation of Developing Mouse Retina

A method for the incorporation of plasmid DNA into murine retinal cells for the purpose of performing either gain- or loss of function studies in vivo is presented. This method capitalizes on the transient increase in permeability of cell plasma membranes induced by the application of an external electrical field.

The functional characterization of genes expressed during mammalian retinal development remains a significant challenge.  Gene targeting to generate ...

Ex Vivo Optogenetic Dissection of Fear Circuits in Brain Slices

Optogenetic approaches are now widely used to study the function of neural populations and circuits by combining targeted expression of light-activated proteins and subsequent manipulation of neural activity by light. Channelrhodopsins (ChRs) are light-gated cation-channels and when fused to a fluorescent protein their expression allows for visualization and concurrent activation of specific cell types and their axonal projections in defined areas of the brain. Via stereotactic injection of viral vectors, ChR fusion proteins can be constitutively or conditionally expressed in specific cells of a defined brain region, and their axonal projections can subsequently be studied anatomically and functionally via ex vivo optogenetic activation in brain slices. This is of particular importance when aiming to understand synaptic properties of connections that could not be addressed with conventional electrical stimulation approaches, or in identifying novel afferent and efferent connectivity that was previously poorly understood. Here, a few examples illustrate how this technique can be applied to investigate these questions to elucidating fear-related circuits in the amygdala. The amygdala is a key region for acquisition and expression of fear, and storage of fear and emotional memories. Many lines of evidence suggest that the medial prefrontal cortex (mPFC) participates in different aspects of fear acquisition and extinction, but its precise connectivity with the amygdala is just starting to be understood. First, it is shown how ex vivo optogenetic activation can be used to study aspects of synaptic communication between mPFC afferents and target cells in the basolateral amygdala (BLA). Furthermore, it is illustrated how this ex vivo optogenetic approach can be applied to assess novel connectivity patterns using a group of GABAergic neurons in the amygdala, the paracapsular intercalated cell cluster (mpITC), as an example.

Ex Vivo Optogenetic Dissection of Fear Circuits in Brain Slices

Optogenetic approaches are widely used to manipulate neural activity and assess the consequences for brain function. Here, a technique is outlined that&#160;upon in vivo expression of the optical activator Channelrhodopsin, allows for ex vivo analysis of synaptic properties of specific long range and local neural connections in fear-related circuits.

Optogenetic approaches are now widely used to study the function of neural populations and circuits by combining targeted expression of light-activated ...

A Simple One-step Dissection Protocol for Whole-mount Preparation of Adult Drosophila Brains

There is an increasing interest in using Drosophila to model human brain degenerative diseases, map neuronal circuitries in adult brains, and study the molecular and cellular basis of higher brain functions. A whole-mount preparation of adult brains with well-preserved morphology is critical for such whole brain-based studies, but can be technically challenging and time-consuming. This protocol describes an easy-to-learn, one-step dissection approach of an adult fly head in less than 10 s, while keeping the intact brain attached to the rest of the body to facilitate subsequent processing steps. The procedure helps remove most of the eye and tracheal tissues normally associated with the brain that can interfere with the later imaging step, and also places less demand on the quality of the dissecting forceps. Additionally, we describe a simple method that allows convenient flipping of the mounted brain samples on a coverslip, which is important for imaging both sides of the brains with similar signal intensity and quality. As an example of the protocol, we present an analysis of dopaminergic (DA) neurons in adult brains of WT (w1118) flies. The high efficacy of the dissection method makes it particularly useful for large-scale adult brain-based studies in Drosophila.

A Simple One-step Dissection Protocol for Whole-mount Preparation of Adult Drosophila Brains

The adult Drosophila brain is a valuable system for studying neuronal circuitry, higher brain functions, and complex disorders. An efficient method to dissect whole brain tissue from the small fly head will facilitate brain-based studies. Here we describe a simple, one-step dissection protocol of adult brains with well-preserved morphology.

There is an increasing interest in using Drosophila to model human brain degenerative diseases, map neuronal circuitries in adult brains, and study the ...

Ex Utero Electroporation and Organotypic Slice Cultures of Embryonic Mouse Brains for Live-Imaging of Migrating GABAergic Interneurons

GABAergic interneurons (INs) are critical components of neuronal networks that drive cognition and behavior. INs destined to populate the cortex migrate tangentially from their place of origin in the ventral telencephalon (including from the medial and caudal ganglionic eminences (MGE, CGE)) to the dorsal cortical plate in response to a variety of intrinsic and extrinsic cues. Different methodologies have been developed over the years to genetically manipulate specific pathways and investigate how they regulate the dynamic cytoskeletal changes required for proper IN migration. In utero electroporation has been extensively used to study the effect of gene repression or overexpression in specific IN subtypes while assessing the impact on morphology and final position. However, while this approach is readily used to modify radially migrating pyramidal cells, it is more technically challenging when targeting INs. In utero electroporation generates a low yield given the decreased survival rates of pups when electroporation is conducted before e14.5, as is customary when studying MGE-derived INs. In an alternative approach, MGE explants provide easy access to the MGE and facilitate the imaging of genetically modified INs. However, in these explants, INs migrate into an artificial matrix, devoid of endogenous guidance cues and thalamic inputs. This prompted us to optimize a method where INs can migrate in a more naturalistic environment, while circumventing the technical challenges of in utero approaches. In this paper, we describe the combination of ex utero electroporation of embryonic mouse brains followed by organotypic slice cultures to readily track, image and reconstruct genetically modified INs migrating along their natural paths in response to endogenous cues. This approach allows for both the quantification of the dynamic aspects of IN migration with time-lapse confocal imaging, as well as the detailed analysis of various morphological parameters using neuronal reconstructions on fixed immunolabeled tissue.

Ex Utero Electroporation and Organotypic Slice Cultures of Embryonic Mouse Brains for Live-Imaging of Migrating GABAergic Interneurons

Here, we provide a low-cost and reliable method to generate electroporated brain organotypic slice cultures from mouse embryos suitable for confocal microscopy and live-imaging techniques.

GABAergic interneurons (INs) are critical components of neuronal networks that drive cognition and behavior. INs destined to populate the cortex migrate ...

Ex Vivo Calcium Imaging for Visualizing Brain Responses to Endocrine Signaling in Drosophila

Organ-to-organ communication by endocrine signaling, for example, from the periphery to the brain, is essential for maintaining homeostasis. As a model animal for endocrine research, Drosophila melanogaster, which has sophisticated genetic tools and genome information, is being increasingly used. This article describes a method for the calcium imaging of Drosophila brain explants. This method enables the detection of the direct signaling of a hormone to the brain. It is well known that many peptide hormones act through G-protein-coupled receptors (GPCRs), whose activation causes an increase in the intracellular Ca2+concentration. Neural activation also elevates intracellular Ca2+ levels, from both Ca2+ influx and the release of Ca2+ stored in the endoplasmic reticulum (ER). A calcium sensor, GCaMP, can monitor these Ca2+ changes. In this method, GCaMP is expressed in the neurons of interest, and the GCaMP-expressing larval brain is dissected and cultured ex vivo. The test peptide is then applied to the brain explant, and the fluorescent changes in GCaMP are detected using a spinning disc confocal microscope equipped with a CCD camera. Using this method, any water-soluble molecule can be tested, and various cellular events associated with neural activation can be imaged using the appropriate fluorescent indicators. Moreover, by modifying the imaging chamber, this method can be used to image other Drosophila organs or the organs of other animals.

Ex Vivo Calcium Imaging for Visualizing Brain Responses to Endocrine Signaling in Drosophila

This paper describes a protocol for ex vivo calcium imaging of the Drosophila brain. In this method, natural or synthetic compounds can be applied to the buffer to test their ability to activate particular neurons in the brain.

Organ-to-organ communication by endocrine signaling, for example, from the periphery to the brain, is essential for maintaining homeostasis. As a model ...

Metabolic Analysis of Drosophila melanogaster Larval and Adult Brains

This protocol describes a method for measuring the metabolism in Drosophila melanogaster larval and adult brains. Quantifying metabolism in whole organs provides a tissue-level understanding of energy utilization that cannot be captured when analyzing primary cells and cell lines. While this analysis is ex vivo, it allows for the measurement from a number of specialized cells working together to perform a function in one tissue and more closely models the in vivo organ. Metabolic reprogramming has been observed in many neurological diseases, including neoplasia, and neurodegenerative diseases. This protocol was developed to assist the D. melanogaster community&#39;s investigation of metabolism in neurological disease models using a commercially available metabolic analyzer. Measuring metabolism of whole brains in the metabolic analyzer is challenging due to the geometry of the brain. This analyzer requires samples to remain at the bottom of a 96-well plate. Cell samples and tissue punches can adhere to the surface of the cell plate or utilize spheroid plates, respectively. However, the spherical, three-dimensional shape of D. melanogaster brains prevents the tissue from adhering to the plate. This protocol requires a specially designed and manufactured micro-tissue restraint that circumvents this problem by preventing any movement of the brain while still allowing metabolic measurements from the analyzer&#39;s two solid-state sensor probes. Oxygen consumption and extracellular acidification rates are reproducible and sensitive to a treatment with metabolic inhibitors. With a minor optimization, this protocol can be adapted for use with any whole tissue and/or model system, provided that the sample size does not exceed the chamber generated by the restraint. While basal metabolic measurements and an analysis after a treatment with mitochondrial inhibitors are described within this protocol, countless experimental conditions, such as energy source preference and rearing environment, could be interrogated.

Metabolic Analysis of Drosophila melanogaster Larval and Adult Brains

We present a protocol for measuring oxygen consumption and extracellular acidification in Drosophila melanogaster larval and adult brains. A metabolic analyzer is utilized with an adapted and optimized protocol. Micro-tissue restraints are a critical component of this protocol and were designed and created specifically for their use in this analysis.

This protocol describes a method for measuring the metabolism in Drosophila melanogaster larval and adult brains. Quantifying metabolism in whole organs ...

Mouse Retina OCT Fibergram Alignment with Confocal Images

Alignment of Visible-Light Optical Coherence Tomography Fibergrams with Confocal Images of the Same Mouse Retina

In recent years, in vivo retinal imaging, which provides non-invasive, real-time, and longitudinal information about biological systems and processes, has been increasingly applied to obtain an objective assessment of neural damage in eye diseases. Ex vivo confocal imaging of the same retina is often necessary to validate the in vivo findings especially in animal research. In this study, we demonstrated a method for aligning an ex vivo confocal image of the mouse retina with its in vivo images. A new clinical-ready imaging technology called visible light optical coherence tomography fibergraphy (vis-OCTF) was applied to acquire in vivo images of the mouse retina. We then performed the confocal imaging of the same retina as the &#34;gold standard&#34; to validate the in vivo vis-OCTF images. This study not only enables further investigation of the molecular and cellular mechanisms but also establishes a foundation for a sensitive and objective evaluation of neural damage in vivo.

Author Spotlight: Advancements in In Vivo and Ex Vivo Retinal Imaging for Improved Glaucoma Diagnosis and Treatment 

The present protocol outlines the steps for aligning in vivo visible-light optical coherence tomography fibergraphy (vis-OCTF) images with ex vivo confocal images of the same mouse retina for the purpose of verifying the observed retinal ganglion cell axon bundle morphology in the in vivo images.

In recent years, in vivo retinal imaging, which provides non-invasive, real-time, and longitudinal information about biological systems and processes, has ...

Preparation for Ex Vivo Color Fundus Photography

Understanding Motor Neuron Responses to Spinal Cord Stimulation

The Ex vivo Preparation of Spinal Cord Slice for the Whole-Cell Patch-Clamp Recording in Motor Neurons During Spinal Cord Stimulation

Spinal cord stimulation (SCS) can effectively restore locomotor function after spinal cord injury (SCI). Because the motor neurons are the final unit to execute sensorimotor behaviors, directly studying the electrical responses of motor neurons with SCS can help us understand the underlying logic of spinal motor modulation. To simultaneously record diverse stimulus characteristics and cellular responses, a patch-clamp is a good method to study the electrophysiological characteristics at a single-cell scale. However, there are still some complex difficulties in achieving this goal, including maintaining cell viability, quickly separating the spinal cord from the bony structure, and using the SCS to successfully induce action potentials. Here, we present a detailed protocol using patch-clamp to study the electrical responses of motor neurons to SCS with high spatiotemporal resolution, which can help researcher improve their skills in separating the spinal cord and maintaining the cell viability at the same time to smoothly study the electrical mechanism of SCS on motor neuron and avoid unnecessary trial and mistake.

Author Spotlight: Advancing Spinal Cord Stimulation - Exploring the Cellular Responses of Motor Neurons Through Patch-Clamp Electrophysiology 

This protocol describes a method using a patch-clamp to study the electrical responses of motor neurons to spinal cord stimulation (SCS) with high spatiotemporal resolution, which can help researchers improve their skills in separating the spinal cord and maintaining cell viability simultaneously.

Spinal cord stimulation (SCS) can effectively restore locomotor function after spinal cord injury (SCI). Because the motor neurons are the final unit to ...

Monitoring Epileptiform Events in Drosophila via Calcium Imaging

Ex Vivo Calcium Imaging for Drosophila Model of Epilepsy

Epilepsy is a neurological disorder characterized by recurrent seizures, partially correlated with genetic origin, affecting over 70 million individuals worldwide. Despite the clinical importance of epilepsy, the functional analysis of neural activity in the central nervous system is still to be developed. Recent advancements in imaging technology, in combination with stable expression of genetically encoded calcium indicators, such as GCaMP6, have revolutionized the study of epilepsy at both brain-wide and single-cell resolution levels. Drosophila melanogaster has emerged as a tool for investigating the molecular and cellular mechanisms underlying epilepsy due to its sophisticated molecular genetics and behavioral assays. In this study, we present a novel and efficient protocol for ex vivo calcium imaging in GCaMP6-expressing adult Drosophila to monitor epileptiform activities. The whole brain is prepared from cac, a well-known epilepsy gene, knockdown flies for calcium imaging with a confocal microscope to identify the neural activity as a follow-up to the bang-sensitive seizure-like behavior assay. The cac knockdown flies showed a higher rate of seizure-like behavior and abnormal calcium activities, including more large spikes and fewer small spikes than wild-type flies. The calcium activities were correlated to seizure-like behavior. This methodology serves as an efficient methodology in screening the pathogenic genes for epilepsy and exploring the potential mechanism of epilepsy at the cellular level.

Author Spotlight: Insights into the Techniques and Findings of Recent Advancements in Epilepsy Research 

Here, we present a protocol for ex vivo calcium imaging in GCaMP6-expressing adult Drosophila to monitor epileptiform activities. The protocol provides a valuable tool for investigating ictal events in adult Drosophila through ex vivo calcium imaging, allowing for exploration of the potential mechanisms of epilepsy at the cellular levels.

Epilepsy is a neurological disorder characterized by recurrent seizures, partially correlated with genetic origin, affecting over 70 million individuals ...