I thank Dr. Maureen Barr, under whose supervision the dauer IL2 remodeling phenotype was initially characterized. Thanks to Dr. C. Britt Carlson for critical reading of the manuscript. Funding in the Barr lab was from the NIH (5R01DK59418) and postdoctoral fellowships from the USDA (2010-65106-20587) and the New Jersey Commission on Spinal Cord Research (CSCR12FEL004). Current funding for this work is from a University of Illinois Urbana-Champaign College of ACES FIRE grant.

1 Crude Dauer feromone Produzione <ol><li> Grow OP50 E. coli da una singola colonia O / N a 37 ° C sotto agitazione in 100 ml di brodo LB a 200 rpm. NOTA: Questo / cultura O N può essere fatta in anticipo e conservato a 4 ° C. </li><li> Grow N2 C. elegans il 15-20 Giugno piatti cm Petri con NGM agar (vedi ricetta nella tabella 1), testa di serie con 50 ml di OP50 E. coli fino a quando il batterio è quasi esaurito 19. </li><li> Fai 5x 250 ml di S supporti (vedi ricetta nella tabella 1) in 1 L beute 19. NOTA: Questa soluzione può essere effettuato in anticipo. </li><li> Coltivare una cultura di OP50 E. coli in 4 l di brodo LB O / N inoculando con 1 ml di OP50 in E. coli e agitazione a 37 ° C per 16 ore. </li><li> Lavare i nematodi da piastre (passo 1.2) con 1 ml di soluzione S basale (vedi ricetta nella tabella 1) e di trasferimento nematodi 4-5 piastre in ciascuna delle 4 1 L Erlenmeyer palloni con i media S preparata al punto 1.3 (a 4 5 piattiper ogni pallone) 19. </li><li> Centrifugare la OP50 dal punto 1.4 a 650 xg per 10 minuti e rimuovere il surnatante. Risospendere ogni pellet batterico in 10 ml di soluzione S basale. Trasferire la stessa quantità di batteri risospese ad ogni pallone di nematodi. </li><li> Collocare i flaconi in un agitatore orbitale a temperatura ambiente (20 - 25 ° C) e 100 - 150 rpm per 4 - 5 giorni fino a quando la soluzione inizia a cancellare, indicando una deplezione di cibo. </li><li> Una volta che il cibo è esaurito, crescerà un&#39;altra cultura O / N di OP50 E. coli in 4x 1 l di brodo LB. Centrifugare i batteri a 650 xg per 10 minuti e aggiungere una pallina da un pallone a ciascuno dei palloni S multimediali con nematodi. Restituire i palloni S media per l&#39;agitatore orbitale, come al punto 1.7, per altri 3-4 giorni fino a quando il cibo si esaurisce di nuovo. </li><li> Dai ~ 1 ml aliquota della soluzione da ciascuna beuta e stimare la concentrazione nematode da sub-campionamento 1 microlitri da ogni 1 ml aliquota e contando il numero di nematodi. NOTA: L&#39;popolazione di nematodi dovrebbe essere 50.000 - 75.000 nematodi / ml. A questa concentrazione la maggior parte dei nematodi sono dauers. </li><li> Eliminare eventuali fiaschi contaminati. NOTA: La contaminazione si manifesta frequentemente come ife fungine visto durante la fase 1.9. </li><li> Nematodi Centrifugare a 4000 xg per 10 min a 4 ° C. Eliminare il pellet nematode e conservare il surnatante. In alternativa, consultare la discussione per l&#39;utilizzo di questi animali per fare un feromone a bassa potenza. </li><li> Filtrare il surnatante con # 1 carta da filtro Whatman. NOTA: Una boccetta di vuoto sarà accelerare questo processo. </li><li> Inoltre Filtrare il surnatante con unità di filtrazione a vuoto sterile 0,45 micron. NOTA: filtrato può essere conservato O / N a 4 ° C o procedere a 1.14. </li><li> Aggiungere il filtrato in un becher da 2 L con un ancoretta. Mettere in una cappa su una piastra riscaldante scalpore. Portate ad ebollizione mescolando ed evaporare a circa 200 ml. Trasferire la soluzione in un becher da 500 ml. Continuare l&#39;ebollizione fino a circa 50 ml sono left. NOTA: Si deve prestare attenzione durante questa fase in quanto è possibile per la soluzione a bollire sopra. Il colore finale 50 ml è un marrone scuro. In qualsiasi momento durante il processo di cottura, il calore può essere spento e il filtrato O / N conservato a temperatura ambiente oa 4 ° C. </li><li> Lasciate raffreddare e centrifugare per 5 minuti a 1000 x g. Versare il surnatante in un becher da 100 ml e scartare il pellet. </li><li> Lessare il surnatante verso il basso per una crosta marrone. Togliere dal fuoco e rompere la crosta con una spatola. Aggiungere sufficiente etanolo 200 prova a coprire la crosta. Coprire il becher con Parafilm e lasciate riposare O / N a RT. Eliminare l&#39;etanolo in un bicchiere pulito e messo a lato. Aggiungere etanolo fresco per coprire la crosta. Ripetere estrazioni O / N 3 volte. Si riuniscono gli estratti. </li><li> Utilizzare una pompa a vuoto per asciugare gli estratti di etanolo. Se una pompa a vuoto non è disponibile, aggiungere l&#39;estratto etanolico di un becher pulito e caldo a 50 ° C sotto agitazione in una cappa aspirante. NOTA: Una volta che l&#39;etanolo è evaporato un residuo appiccicoso di light colore marrone deve rimanere. Se si usa il riscaldamento, la cura dovrebbe essere presa per non bruciare la soluzione di riscaldamento per troppo tempo. </li><li> Disciogliere il residuo in 10 ml di acqua distillata sterile. Filtro sterilizzare questa soluzione con un filtro a siringa da 0,22 micron e conservare a -20 ° C in aliquote di 1 ml. NOTA: 1 ml di acqua viene utilizzata per sciogliere il residuo per ogni 100 ml di coltura nematode liquido originale. Ad esempio, se una delle fiasche di coltura liquido viene scartato a causa della contaminazione, quindi regolare la quantità di acqua utilizzata per sciogliere il residuo. </li></ol> 2 Determinazione del feromone Dose Response <ol><li> Preparare dauer feromone facendo 6x 5 ml di NGM media con Noble agar senza peptone, e integrato con 50 mg / ml di streptomicina solfato e una serie di dauer feromone (vedi ricetta in Tabella 1) 4, 19. Miscelare i componenti in un 13x100 mm provetta di vetro, bollire sopra un becco Bunsen, e poi versare in tre centimetri piastre di Petri. </li><li> Pesare amtubo icrocentrifuge. Aggiungere 1 ml di O / N coltura di E. coli OP50 al tubo e centrifugare a ~ 17.000 xg in una provetta. Rimuovere tutto il surnatante. Pesare nuovamente il tubo e determinare il peso del pellet batterico. Risospendere il pellet con tampone M9 (vedi ricetta in Tabella 1) per una concentrazione finale di 4% (w / v). Aliquotare 10 microlitri della sospensione batterica sul centro di ciascuna piastra feromone 4. Conservare le piastre O / N a RT. </li><li> Scegli 10-15 gravide N2 wild-type ermafroditi un giorno dopo la muta in età adulta sulle piastre feromoni 4. Conservare le piastre a 25 ° C per 3 - 4 ore. </li><li> Scegli fuori tutti i ermafroditi adulti. Registrare il numero di uova deposte per ogni piatto. Sigillare le piastre con parafilm e ritornare a 25 ° C per 3 giorni 17. </li><li> Contare la percentuale di dauers (Figura 2). Nota: Per entrambi i metodi, è importante notare che dauers (e ad un ex minoretenda non dauers) salirà sulle pareti e sul coperchio delle piastre di Petri. E &#39;quindi importante esaminare tutte le superfici del piatto per nematodi. </li><li> Montare i dati ad una curva dose-risposta e stimare la concentrazione CE 90 del feromone (feromone sufficiente ad indurre il 90% degli animali per formare dauers) come mostrato in Figura 3 Nota:. Usiamo tipicamente un modello di regressione logistica per stimare la CE 90 , ma diversi pacchetti software statistici possono avere metodi alternativi che producono stime simili. </li></ol> 3 Immagini dal vivo di Dauer IL2 neuroni <ol><li> Preparare piatti dauer feromoni come nel protocollo 2 utilizzando il valore EC 90 determinata al punto 2.6. </li><li> Indurre dauers utilizzando i metodi del protocollo 2 con un ceppo che trasporta un giornalista transgene integrato IL2 (myIs13 [P klp-6 :: GFP], myIs14 [P klp-6 :: GFP], myIs16 [P <em&gt; KLP-6 :: tdTomato] o qIs56 [P lag-2 :: GFP]) 12, 20, 21. NOTA: Se si utilizza q Is56, espressione di GFP non sarà visibile nei IL2Qs fino a diverse ore nel molt dauer e alcuni degli eventi di rimodellamento iniziali non saranno visibili. Inoltre, mentre il segnale fluorescente dalla P lag-2 :: GFP transgene è in definitiva più luminoso nelle IL2s durante dauer rispetto ai 6 KLP-reporter fluorescenti P, la P lag-2 :: transgene GFP esprime anche debolmente nei muscoli della testa che può mascherare i bei rami IL2. </li><li> Dopo la deposizione delle uova, rimuovere gli ermafroditi adulti, sigillare le piastre con Parafilm e incubare per 34 ore a 25 ° C 17. NOTA: La lunghezza del tempo per la muta dauer varia leggermente da individuo a individuo. La rapida periodo più di dendrite arborizzazione inizia 4-5 ore dopo l&#39;inizio della muta dauer (39-44hr dopo la deposizione delle uova a 25 ° C) 12. </li><li> Il giorno prima di imaging, costituiscono una soluzione di 10% (w / v) agarosio in tampone M9 con dauer feromone alla concentrazione CE 90. Aliquota circa 100 ml di agarosio su un vetrino da microscopio e rapidamente, ma delicatamente, posizionare un&#39;altra diapositiva in alto per creare una superficie piana agarosio. Dopo l&#39;agarosio si è solidificato, avvolgere le diapositive saran wrap e conservare in una camera umida (scatola punta della pipetta con tovaglioli di carta bagnati). </li><li> Dopo il periodo di incubazione 34 ore, esaminare le piastre di feromone per nematodi che hanno smesso faringeo pompaggio. Scivoli separati in modo tale che una sola superficie di un vetrino ha agarosio su di esso. Scegli uno o più nematodi su un pad agarosio del 10% e 1 μ l di 0,1 micron sferette di polistirene 22. NOTA: Con una popolazione ben sincronizzato, la maggior parte dei nematodi sul piatto entrerà nella muta da L2D a dauer. Tuttavia, ci possono essere variazioni tra individuals. E &#39;quindi importante notare funzionalità aggiuntive (stoma occlusione, faringeo rimodellamento) per stimare la quantità di tempo che gli animali sono stati all&#39;interno della muta dauer (vedi risultati rappresentativi per esempio). </li><li> Determinare l&#39;orientamento (sinistra / destra, dorsale / ventrale) del nematode. Cattura immagini di Z-stack di un dendrite IL2Q ad ingrandimento 100X con la possibile intensità di fluorescenza più basso ogni 15 minuti o quando necessario per l&#39;esperimento specifico. Continuare a catturare immagini fino a quando il nematode ha separato dalla cuticola L2D e immobilizzazione è impossibile o se l&#39;animale si riprende da dauer (faringe comincia pompaggio). Quando non l&#39;imaging attivamente, posizionare il vetrino in una camera umida. NOTA: Usiamo un microscopio epifluorescente con un contrasto di interferenza differenziale di fase e motorizzato (DIC) ottica. </li></ol>

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The authors have nothing to disclose

Un esame della neuroplasticità specifici per dauer e altri cambiamenti morfologici Dauer-associata richiede controllata e affidabile di formazione dauers sia attraverso la mutazione genetica (cioè mutanti, DAF-C) o in caso di esposizione di wild-type animali a feromone. Mentre l&#39;uso di una mutazione genetica per indurre dauers è conveniente, può confondere risultati. Pertanto, i dati raccolti con mutazioni daf-c devono essere successivamente confermati con wild-type animali indotti ad entrare n...

Plasticità fenotipica, tra cui plasticità evolutiva e comportamentale, è importante per adattamenti alle condizioni ambientali avverse ed è considerato una forza trainante nell&#39;evoluzione 1. C. elegans è un organismo modello utilizzato frequentemente per gli studi di sviluppo e neurobiologia. In condizioni ideali, C. elegans si sviluppa attraverso quattro stadi larvali prima di entrare nella fase riproduttiva adulto. Tuttavia, in condizioni di scarsa disponibilità di cibo e di alta densità di popolazione, C. elegans può subire un interruttore di sviluppo e di entrare in una fase di lunga durata e resistente alle sollecitazioni dauer 2. Dauers mostrano molte differenze morfologiche e comportamentali da non dauers che probabilmente mediano questa resistenza allo stress. Gli stimoli ambientali e percorsi genetici che regolano l&#39;ingresso dauer sono stati ampiamente descritti 3, 4, 5, 6, 7. Tuttavia, i meccanismi molecolari che controllano le singole modifiche fenotipiche che si verificano durante formazione dauer sono meno ben compreso. L&#39;esame di fenotipi specifici-Dauer richiede la produzione di animali Dauer. Questo può essere realizzato in tre modi: 1) Picking da una cultura affamato di C. elegans, 2) Uso della formazione dauer costitutiva (daf-c) mutanti, 3) induzione della formazione dauer attraverso feromone purificato. E &#39;relativamente semplice per scegliere dauers da una piastra standard NGM con una C. popolazione elegans che ha esaurito il suo batterica di approvvigionamento alimentare. Nelle nostre mani, una piastra standard NGM originariamente seminato con 50 ml di OP50 Escherichia coli, ha permesso di crescere per 3 giorni e successivamente inoculate con 3 - 4 adulti ermafroditi mantenuta a 25 ° C, si esaurirà la fornitura di cibo entro una settimana e produrre diverse migliaia dauers all&#39;interno di un ulteriore 3 giorni (oltre a numerosi non-dauers affamati). Tuttavia, questo metodo non è soddisfacente per i processi che si verificano durante l&#39;esame muta in dAuer. E &#39;difficile determinare quale delle diverse migliaia di animali su un piatto tipico Starved stanno entrando in dauer. Inoltre, l&#39;uso di una piastra di fame non offre alcuna possibilità di sincronizzazione. L&#39;uso di mutanti daf-c consente la sincronizzazione e la generazione affidabile di dauers. Tuttavia, non vi è alcuna garanzia che una particolare daf-c mutazione non influirà altri fenotipi specifici-Dauer da solo o in combinazione con altre mutazioni. La presenza di un feromone dauer stato implicito Cassada e Russell e successivamente dimostrato da Golden e Riddle. Il feromone dauer da allora è stato caratterizzato chimicamente 2, 8, 9, 10. Feromone purificato è costituito da una miscela complessa di ascarosides, che in forme diverse a regolare entrambi i processi comportamentali e di sviluppo 9, 11. L&#39;uso di un estratto di feromone greggio dauer permette di induzione affidabile controllata di dauers sincronizzati in uno sfondo wild-type. </p&gt; Il sistema nervoso e le cellule gliali associate subiscono rimodellamento durante dauer larva formazione 12, 13, 14. Alcuni di questi cambiamenti sono irreversibili, come ad esempio la ristrutturazione delle cellule gliali durante dauer 13, 14. Tuttavia altri eventi di rimodellamento sono reversibili dopo un ritorno favorevole condizioni ambientali. Ad esempio, una serie di quattro neuroni IL2Q subiscono una rapida e reversibile rimodellamento neuronale durante la formazione dauer tra cui: arborizzazione dei dendriti, un passaggio da singolo dendritiche ai neuroni e assoni multidendritic rimodellamento 12. I metodi consentono qui per imaging attendibile in vivo di neuroplasticità indotta da stress in un organismo modello. I metodi presentati per la produzione e la sperimentazione di greggio dauer feromone sono precedentemente descritti e compilati da diverse fonti 4, 8, 15, 16, 17, 18.

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		<tr height="40">
			<td height="40" style="height:40px;width:259px;">N2 C. elegans Bristol strain</td>
			<td style="width:152px;">Caenorhabditis Genetics Center</td>
			<td style="width:212px;"></td>
			<td style="width:251px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">PT2660 myIs13[Pklp-6::gfp] III</td>
			<td style="width:152px;">Upon request from Schroeder lab</td>
			<td></td>
			<td style="width:251px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">PT2762 myIs14[Pklp-6::gfp] V</td>
			<td style="width:152px;">Upon request from Schroeder lab</td>
			<td></td>
			<td style="width:251px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">JK2868 qIs56[Plag-2::gfp] V</td>
			<td style="width:152px;">Caenorhabditis Genetics Center</td>
			<td></td>
			<td style="width:251px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;">OP50 E. coli</td>
			<td style="width:152px;">Caenorhabditis Genetics Center</td>
			<td></td>
			<td style="width:251px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Petri dishes</td>
			<td style="width:152px;">Tritech Research</td>
			<td>60 mm T3308, 35 mm T3501</td>
			<td style="width:251px;"></td>
		</tr>
		<tr height="132">
			<td height="132" style="height:132px;">NGM agar</td>
			<td style="width:152px;">Various</td>
			<td></td>
			<td style="width:251px;">3 g NaCl, 17 g agar, 2.5 g peptone in 975 mL H2O autoclaved cooled to 55&#176;C followed by 1 mL of 5 mg/ml cholesterol in ethanol, 25 mL of 1 M KPO4 buffer (pH 6.0), 1 mL of 1 M CaCl2, 1 mL of 1 M MgSO4</td>
		</tr>
		<tr height="356">
			<td height="356" style="height:356px;">S Media</td>
			<td style="width:152px;">Various</td>
			<td></td>
			<td style="width:251px;">S media consists of S basal solution (1.46 g NaCl, 0.25g K2HPO4, 1.5 g KH2PO4, 0.25 ml of 5 mg/ml cholesterol in ethanol and H2O to 250 mL. Autoclaved.) To the S basal solution add 2.5 mL of potassium citrate pH 6.0 (2 g citric acid monohydrate, 29.4 g tri-potassium citrate monohydrate, H2O to 100 mL, autoclaved), 2.5 mL of Trace Metals Solution (1.86 g disodium EDTA, 0.69 g FeSO4&#160;&#8226;7 H2O, 0.2 g MnCl2&#8226;4 H2O, 0.29 g ZnSO4&#160;&#8226;7 H2O, 0.025 g CuSO4&#160;&#8226;5 H2O, H2O to 1 liter. Autoclaved and stored in the dark), 0.75 mL of 1 M CaCl2, and 0.75 mL of 1 M MgSO4.</td>
		</tr>
		<tr height="392">
			<td height="392" style="height:392px;width:259px;">Dauer pheromone plates for dose-response assay</td>
			<td style="width:152px;">Various</td>
			<td></td>
			<td style="width:251px;">Mix 0.085 g Noble agar, 0.5 mL of 0.513 M NaCl and 5 &#181;L of 5 mg/ml cholesterol dissolved in ethanol in each of 6x 15 mL culture tubes. Add sufficient crude pheromone to each tube to create a range of concentrations. Add H2O to bring the volume to 4.725 mL.&#160; Boil over a Bunsen burner until the agar is dissolved and then cool to 55 &#176;C. Add 125 &#181;L 1 M KPO4 buffer (pH 6.0), 50 &#181;l 0.1 M CaCl2, 50 &#181;L 0.1 M MgSO4 and 50 &#181;l of 5 mg/ml streptomycin sulfate to each tube.&#160; Pour the contents of each tube into a 35 mm diameter Petri dish. Let the agar solidify at room temperature overnight (if longer, store in enclosed container to prevent excessive drying).</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Microsphere beads 0.1 micron</td>
			<td style="width:152px;">Polysciences Inc.</td>
			<td>00876-15</td>
			<td style="width:251px;"></td>
		</tr>
		<tr height="68">
			<td height="68" style="height:68px;">M9 buffer</td>
			<td style="width:152px;">Various</td>
			<td></td>
			<td style="width:251px;">Mix 3 g KH2PO4, 6 g Na2HPO4, 5 g NaCl, 1 ml 1 M MgSO4, H2O to 1 liter. Sterilize by autoclaving</td>
		</tr>
	</tbody>
</table>

in vivo imaging of dauer-specific neuronal remodeling in c. elegans

I meccanismi che controllano lo stress-indotta plasticità fenotipica di animali sono spesso complesse e difficili da studiare in vivo. Un classico esempio di plasticità indotta da stress è la fase dauer di C. elegans. Dauers sono uno stadio larvale di sviluppo alternativo formata in condizioni di basse concentrazioni di cibo batterica e alte concentrazioni di un feromone dauer. Dauers visualizzare ampia plasticità evolutiva e comportamentale. Ad esempio, un set di quattro quadranti interno-labiale (IL2Q) neuroni soggetta ad un esteso rimodellamento reversibile durante la formazione dauer. Utilizzando la ben nota voce di percorsi ambientali di regolazione dauer, un metodo precedentemente stabilito per la produzione di greggio dauer feromone da grandi culture nematodi liquido è dimostrata. Con questo metodo, una concentrazione di 50.000 - 75.000 nematodi / ml di coltura liquido è sufficiente a produrre una molto potente greggio dauer feromone. La potenza feromone greggio è determined da un saggio biologico dose-risposta. Infine, sono descritti i metodi utilizzati per in vivo time-lapse imaging dei IL2Qs durante la formazione dauer.

La produzione di greggio risultati dauer feromoni in un liquido giallo (Figura 1) che è sia caldo e freddo stabile. Aliquote di feromone greggio vengono conservati a -20 ° C indefinitamente senza perdita evidente di attività. In seguito la produzione di feromoni, un unico biotest dose-risposta è sufficiente per una stima approssimativa di potenza. Tuttavia, per la maggior parte degli esperimenti è necessario ripetere il saggio biologico 2 - 3 volte e prendere una media di ciascun esperimento. I ris...

Watch this Scientific Journal Video about In Vivo Imaging of Dauer-specific Neuronal Remodeling in C. elegans at JoVE.com

In Vivo Imaging of Dauer-specific Neuronal Remodeling in C. elegans

Following exposure to specific environmental stressors, the nematode Caenorhabditis elegans undergoes extensive phenotypic plasticity to enter into a stress-resistant &#8216;dauer&#8217; juvenile stage. We present methods for the controlled induction and imaging of neuroplasticity during dauer.

In Vivo Imaging di Dauer-specifica neuronale ritocca in C. elegans

The mechanisms controlling stress-induced phenotypic plasticity in animals are frequently complex and difficult to study in vivo. A classic example of ...

in-vivo-imaging-of-dauer-specific-neuronal-remodeling-in-c-elegans

Research

JoVE Journal

Neuroscience

In Vivo Imaging of Dauer-specific Neuronal Remodeling in C. elegans

11.2K Views.  University of Illinois Urbana-Champaign. Following exposure to specific environmental stressors, the nematode Caenorhabditis elegans undergoes extensive phenotypic plasticity to enter into a stress-resistant ‘dauer’ juvenile stage. We present methods for the controlled induction and imaging of neuroplasticity during dauer. 

Video: In Vivo Imaging of Dauer-specific Neuronal Remodeling in C. elegans

Transfection of Mouse Retinal Ganglion Cells by in vivo Electroporation

The targeting and refinement of RGC projections to the midbrain is a popular and powerful model system for studying how precise patterns of neural connectivity form during development. In mice, retinofugal projections are arranged in a topographic manner and form eye-specific layers in the Lateral Geniculate Nucleus (dLGN) of the thalamus and the Superior Colliculus (SC). The development of these precise patterns of retinofugal projections has typically been studied by labeling populations of RGCs with fluorescent dyes and tracers, such as horseradish peroxidase1-4. However, these methods are too coarse to provide insight into developmental changes in individual RGC axonal arbor morphology that are the basis of retinotopic map formation. They also do not allow for the genetic manipulation of RGCs.
Recently, electroporation has become an effective method for providing precise spatial and temporal control for delivery of charged molecules into the retina5-11. Current retinal electroporation protocols do not allow for genetic manipulation and tracing of retinofugal projections of a single or small cluster of RGCs in postnatal mice. It has been argued that postnatal in vivo electroporation is not a viable method for transfecting RGCs since the labeling efficiency is extremely low and hence requires targeting at embryonic ages when RGC progenitors are undergoing differentiation and proliferation6. 
In this video we describe an in vivo electroporation protocol for targeted delivery of genes, shRNA, and fluorescent dextrans to murine RGCs postnatally. This technique provides a cost effective, fast and relatively easy platform for efficient screening of candidate genes involved in several aspects of neural development including axon retraction, branching, lamination, regeneration and synapse formation at various stages of circuit development. In summary we describe here a valuable tool which will provide further insights into the molecular mechanisms underlying sensory map development.

Transfection of Mouse Retinal Ganglion Cells by in vivo Electroporation

We demonstrate an in vivo electroporation protocol for transfecting single or small clusters of retinal ganglion cells (RGCs) and other retinal cell types in postnatal mice over a wide range of ages. The ability to label and genetically manipulate postnatal RGCs in vivo is a powerful tool for developmental studies.

Trasfezione delle cellule gangliari della retina di topo In vivo Elettroporazione

The targeting and refinement of RGC projections to the midbrain is a popular and powerful model system for studying how precise patterns of neural ...

Ricerca

Neuroscienze

In vivo Laser Axotomy in C. elegans

Neurons communicate with other cells via axons and dendrites, slender membrane extensions that contain pre- or post-synaptic specializations. If a neuron is damaged by injury or disease, it may regenerate. Cell-intrinsic and extrinsic factors influence the ability of a neuron to regenerate and restore function. Recently, the nematode C. elegans has emerged as an excellent model organism to identify genes and signaling pathways that influence the regeneration of neurons1-6. The main way to initiate neuronal regeneration in C. elegans is laser-mediated cutting, or axotomy. During axotomy, a fluorescently-labeled neuronal process is severed using high-energy pulses. Initially, neuronal regeneration in C. elegans was examined using an amplified femtosecond laser5. However, subsequent regeneration studies have shown that a conventional pulsed laser can be used to accurately sever neurons in vivo and elicit a similar regenerative response1,3,7.
We present a protocol for performing in vivo laser axotomy in the worm using a MicroPoint pulsed laser, a turnkey system that is readily available and that has been widely used for targeted cell ablation. We describe aligning the laser, mounting the worms, cutting specific neurons, and assessing subsequent regeneration. The system provides the ability to cut large numbers of neurons in multiple worms during one experiment. Thus, laser axotomy as described herein is an efficient system for initiating and analyzing the process of regeneration.

In vivo Laser Axotomy in C. elegans

A protocol to cut neurons in C. elegans with a MicroPoint pulsed laser is presented. We describe setting up the system, immobilizing worms, and severing labeled neurons. Advantages include a relatively low-cost system and the ability to sever neuronal processes or ablate cells in vivo.

In vivo Laser assotomia in C. elegans

Neurons communicate with other cells via axons and dendrites, slender membrane extensions that contain pre- or post-synaptic specializations. If a neuron ...

Functional Neuroimaging Using Ultrasonic Blood-brain Barrier Disruption and Manganese-enhanced MRI

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains technically challenging. One approach, Activation-Induced Manganese-enhanced MRI (AIM MRI), has been used successfully to map neuronal activity in rodents 1-5. In AIM MRI, Mn2+ acts a calcium analog and accumulates in depolarized neurons 6,7. Because Mn2+ shortens the T1 tissue property, regions of elevated neuronal activity will enhance in MRI. Furthermore, Mn2+ clears slowly from the activated regions; therefore, stimulation can be performed outside the magnet prior to imaging, enabling greater experimental flexibility. However, because Mn2+ does not readily cross the blood-brain barrier (BBB), the need to open the BBB has limited the use of AIM MRI, especially in mice.
One tool for opening the BBB is ultrasound. Though potentially damaging, if ultrasound is administered in combination with gas-filled microbubbles (i.e., ultrasound contrast agents), the acoustic pressure required for BBB opening is considerably lower. This combination of ultrasound and microbubbles can be used to reliably open the BBB without causing tissue damage 8-11.
Here, a method is presented for performing AIM MRI by using microbubbles and ultrasound to open the BBB. After an intravenous injection of perflutren microbubbles, an unfocused pulsed ultrasound beam is applied to the shaved mouse head for 3 minutes. For simplicity, we refer to this technique of BBB Opening with Microbubbles and UltraSound as BOMUS 12. Using BOMUS to open the BBB throughout both cerebral hemispheres, manganese is administered to the whole mouse brain. After experimental stimulation of the lightly sedated mice, AIM MRI is used to map the neuronal response.
To demonstrate this approach, herein BOMUS and AIM MRI are used to map unilateral mechanical stimulation of the vibrissae in lightly sedated mice 13. Because BOMUS can open the BBB throughout both hemispheres, the unstimulated side of the brain is used to control for nonspecific background stimulation. The resultant 3D activation map agrees well with published representations of the vibrissae regions of the barrel field cortex 14. The ultrasonic opening of the BBB is fast, noninvasive, and reversible; and thus this approach is suitable for high-throughput and/or longitudinal studies in awake mice.

A technique is described for broadly opening the blood-brain barrier in the mouse using microbubbles and ultrasound. Using this technique, manganese can be administered to the mouse brain. Because manganese is an MRI contrast agent that accumulates in depolarized neurons, this approach enables imaging of neuronal activity.

Neuroimaging funzionale con l&#39;impiego dell&#39;ecografia emato-encefalica e la barriera di Turbativa del Manganese-enhanced MRI

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains ...

Automated Quantification of Synaptic Fluorescence in C. elegans

Synapse strength refers to the amplitude of postsynaptic responses to presynaptic neurotransmitter release events, and has a major impact on overall neural circuit function. Synapse strength critically depends on the abundance of neurotransmitter receptors clustered at synaptic sites on the postsynaptic membrane. Receptor levels are established developmentally, and can be altered by receptor trafficking between surface-localized, subsynaptic, and intracellular pools, representing important mechanisms of synaptic plasticity and neuromodulation. Rigorous methods to quantify synaptically-localized neurotransmitter receptor abundance are essential to study synaptic development and plasticity. Fluorescence microscopy is an optimal approach because it preserves spatial information, distinguishing synaptic from non-synaptic pools, and discriminating among receptor populations localized to different types of synapses. The genetic model organism Caenorhabditis elegans is particularly well suited for these studies due to the small size and relative simplicity of its nervous system, its transparency, and the availability of powerful genetic techniques, allowing examination of native synapses in intact animals.
Here we present a method for quantifying fluorescently-labeled synaptic neurotransmitter receptors in C. elegans. Its key feature is the automated identification and analysis of individual synapses in three dimensions in multi-plane confocal microscope output files, tabulating position, volume, fluorescence intensity, and total fluorescence for each synapse. This approach has two principal advantages over manual analysis of z-plane projections of confocal data. First, because every plane of the confocal data set is included, no data are lost through z-plane projection, typically based on pixel intensity averages or maxima. Second, identification of synapses is automated, but can be inspected by the experimenter as the data analysis proceeds, allowing fast and accurate extraction of data from large numbers of synapses. Hundreds to thousands of synapses per sample can easily be obtained, producing large data sets to maximize statistical power. Considerations for preparing C. elegans for analysis, and performing confocal imaging to minimize variability between animals within treatment groups are also discussed. Although developed to analyze C. elegans postsynaptic receptors, this method is generally useful for any type of synaptically-localized protein, or indeed, any fluorescence signal that is localized to discrete clusters, puncta, or organelles.
The procedure is performed in three steps: 1) preparation of samples, 2) confocal imaging, and 3) image analysis. Steps 1 and 2 are specific to C. elegans, while step 3 is generally applicable to any punctate fluorescence signal in confocal micrographs.

Automated Quantification of Synaptic Fluorescence in C. elegans

The abundance of neurotransmitter receptors clustered at synapses strongly influences synaptic strength. This method quantifies fluorescently-labeled neurotransmitter receptors in three dimensions with single-synapse resolution in C. elegans, allowing hundreds of synapses to be rapidly characterized within a single sample without distortions introduced by z-plane projection.

Quantificazione automatica di fluorescenza in Synaptic<em&gt; C. elegans</em

Synapse strength refers to the amplitude of postsynaptic responses to presynaptic neurotransmitter release events, and has a major impact on overall ...

Dual Electrophysiological Recordings of Synaptically-evoked Astroglial and Neuronal Responses in Acute Hippocampal Slices

Astrocytes form together with neurons tripartite synapses, where they integrate and modulate neuronal activity. Indeed, astrocytes sense neuronal inputs through activation of their ion channels and neurotransmitter receptors, and process information in part through activity-dependent release of gliotransmitters. Furthermore, astrocytes constitute the main uptake system for glutamate, contribute to potassium spatial buffering, as well as to GABA clearance. These cells therefore constantly monitor synaptic activity, and are thereby sensitive indicators for alterations in synaptically-released glutamate, GABA and extracellular potassium levels. Additionally, alterations in astroglial uptake activity or buffering capacity can have severe effects on neuronal functions, and might be overlooked when characterizing physiopathological situations or knockout mice. Dual recording of neuronal and astroglial activities is therefore an important method to study alterations in synaptic strength associated to concomitant changes in astroglial uptake and buffering capacities. Here we describe how to prepare hippocampal slices, how to identify stratum radiatum astrocytes, and how to record simultaneously neuronal and astroglial electrophysiological responses. Furthermore, we describe how to isolate pharmacologically the synaptically-evoked astroglial currents.

The preparation of acute brain slices from isolated hippocampi, as well as the simultaneous electrophysiological recordings of astrocytes and neurons in stratum radiatum during stimulation of schaffer collaterals is described. The pharmacological isolation of astroglial potassium and glutamate transporter currents is demonstrated.

Due registrazioni elettrofisiologiche di sinapticamente-evocati Risposte astrogliale e neuronale in acute fettine di ippocampo

Astrocytes form together with neurons tripartite synapses, where they integrate and modulate neuronal activity. Indeed, astrocytes sense neuronal inputs ...

In vivo Neuronal Calcium Imaging in C. elegans

The nematode worm C. elegans is an ideal model organism for relatively simple, low cost neuronal imaging in vivo. Its small transparent body and simple, well-characterized nervous system allows identification and fluorescence imaging of any neuron within the intact animal. Simple immobilization techniques with minimal impact on the animal's physiology allow extended time-lapse imaging. The development of genetically-encoded calcium sensitive fluorophores such as cameleon 1 and GCaMP 2 allow in vivo imaging of neuronal calcium relating both cell physiology and neuronal activity. Numerous transgenic strains expressing these fluorophores in specific neurons are readily available or can be constructed using well-established techniques. Here, we describe detailed procedures for measuring calcium dynamics within a single neuron in vivo using both GCaMP and cameleon. We discuss advantages and disadvantages of both as well as various methods of sample preparation (animal immobilization) and image analysis. Finally, we present results from two experiments: 1) Using GCaMP to measure the sensory response of a specific neuron to an external electrical field and 2) Using cameleon to measure the physiological calcium response of a neuron to traumatic laser damage. Calcium imaging techniques such as these are used extensively in C. elegans and have been extended to measurements in freely moving animals, multiple neurons simultaneously and comparison across genetic backgrounds. C. elegans presents a robust and flexible system for in vivo neuronal imaging with advantages over other model systems in technical simplicity and cost.

In vivo Neuronal Calcium Imaging in C. elegans

With its small transparent body, well-documented neuroanatomy and a host of amenable genetic techniques and reagents, C. elegans makes an ideal model organism for in vivo neuronal imaging using relatively simple, low-cost techniques. Here we describe single neuron imaging within intact adult animals using genetically encoded fluorescent calcium indicators.

In vivo imaging di calcio neuronale in C. elegans

The nematode worm C. elegans is an ideal model organism  for relatively simple, low cost neuronal imaging in vivo. Its small transparent body and simple, ...

Fast Micro-iontophoresis of Glutamate and GABA: A Useful Tool to Investigate Synaptic Integration

One of the fundamental interests in neuroscience is to understand the integration of excitatory and inhibitory inputs along the very complex structure of the dendritic tree, which eventually leads to neuronal output of action potentials at the axon. The influence of diverse spatial and temporal parameters of specific synaptic input on neuronal output is currently under investigation, e.g. the distance-dependent attenuation of dendritic inputs, the location-dependent interaction of spatially segregated inputs, the influence of GABAergig inhibition on excitatory integration, linear and non-linear integration modes, and many more.
With fast micro-iontophoresis of glutamate and GABA it is possible to precisely investigate the spatial and temporal integration of glutamatergic excitation and GABAergic inhibition. Critical technical requirements are either a triggered fluorescent lamp, light-emitting diode (LED), or a two-photon scanning microscope to visualize dendritic branches without introducing significant photo-damage of the tissue. Furthermore, it is very important to have a micro-iontophoresis amplifier that allows for fast capacitance compensation of high resistance pipettes. Another crucial point is that no transmitter is involuntarily released by the pipette during the experiment.
Once established, this technique will give reliable and reproducible signals with a high neurotransmitter and location specificity. Compared to glutamate and GABA uncaging, fast iontophoresis allows using both transmitters at the same time but at very distant locations without limitation to the field of view. There are also advantages compared to focal electrical stimulation of axons: with micro-iontophoresis the location of the input site is definitely known and it is sure that only the neurotransmitter of interest is released. However it has to be considered that with micro-iontophoresis only the postsynapse is activated and presynaptic aspects of neurotransmitter release are not resolved. In this article we demonstrate how to set up micro-iontophoresis in brain slice experiments.

In this article we introduce fast micro-iontophoresis of neurotransmitters as a technique to investigate integration of postsynaptic signals with high spatial and temporal precision.

Veloce micro-ionoforesi di glutammato e GABA: un utile strumento per indagare l&#39;integrazione Synaptic

One of the fundamental interests in neuroscience is to understand the integration of excitatory and inhibitory inputs along the very complex structure of ...

Super-resolution Imaging of Neuronal Dense-core Vesicles

Detection of fluorescence provides the foundation for many widely utilized and rapidly advancing microscopy techniques employed in modern biological and medical applications. Strengths of fluorescence include its sensitivity, specificity, and compatibility with live imaging. Unfortunately, conventional forms of fluorescence microscopy suffer from one major weakness, diffraction-limited resolution in the imaging plane, which hampers studies of structures with dimensions smaller than ~250 nm. Recently, this limitation has been overcome with the introduction of super-resolution fluorescence microscopy techniques, such as photoactivated localization microscopy (PALM). Unlike its conventional counterparts, PALM can produce images with a lateral resolution of tens of nanometers. It is thus now possible to use fluorescence, with its myriad strengths, to elucidate a spectrum of previously inaccessible attributes of cellular structure and organization.
Unfortunately, PALM is not trivial to implement, and successful strategies often must be tailored to the type of system under study. In this article, we show how to implement single-color PALM studies of vesicular structures in fixed, cultured neurons. PALM is ideally suited to the study of vesicles, which have dimensions that typically range from ~50-250 nm. Key steps in our approach include labeling neurons with photoconvertible (green to red) chimeras of vesicle cargo, collecting sparsely sampled raw images with a super-resolution microscopy system, and processing the raw images to produce a high-resolution PALM image. We also demonstrate the efficacy of our approach by presenting exceptionally well-resolved images of dense-core vesicles (DCVs) in cultured hippocampal neurons, which refute the hypothesis that extrasynaptic trafficking of DCVs is mediated largely by DCV clusters.

We describe how to implement photoactivated localization microscopy (PALM)-based studies of vesicles in fixed, cultured neurons. Key components of our protocol include labeling vesicles with photoconvertible chimeras, collecting sparsely sampled raw images with a super-resolution microscopy system, and processing the raw images to produce a super-resolution image.

Super-Resolution Imaging di vescicole neuronali Dense-core

Detection of fluorescence provides the foundation for many widely utilized and rapidly advancing microscopy techniques employed in modern biological and ...

Utilizing Combined Methodologies to Define the Role of Plasma Membrane Delivery During Axon Branching and Neuronal Morphogenesis

During neural development, growing axons extend to multiple synaptic partners by elaborating axonal branches. Axon branching is promoted by extracellular guidance cues like netrin-1 and results in dramatic increases to the surface area of the axonal plasma membrane. Netrin-1-dependent axon branching likely involves temporal and spatial control of plasma membrane expansion, the components of which are supplied through exocytic vesicle fusion. These fusion events are preceded by formation of SNARE complexes, comprising a v-SNARE, such as VAMP2 (vesicle-associated membrane protein 2), and plasma membrane t-SNAREs, syntaxin-1 and SNAP25 (synaptosomal-associated protein 25). Detailed herein isa multi-pronged approach used to examine the role of SNARE mediated exocytosis in axon branching. The strength of the combined approach is data acquisition at a range of spatial and temporal resolutions, spanning from the dynamics of single vesicle fusion events in individual neurons to SNARE complex formation and axon branching in populations of cultured neurons. This protocol takes advantage of established biochemical approaches to assay levels of endogenous SNARE complexes and Total Internal Reflection Fluorescence (TIRF) microscopy of cortical neurons expressing VAMP2 tagged with a pH-sensitive GFP (VAMP2-pHlourin) to identify netrin-1 dependent changes in exocytic activity in individual neurons. To elucidate the timing of netrin-1-dependent branching, time-lapse differential interference contrast (DIC) microscopy of single neurons over the order of hours is utilized. Fixed cell immunofluorescence paired with botulinum neurotoxins that cleave SNARE machinery and block exocytosis demonstrates that netrin-1 dependent axon branching requires SNARE-mediated exocytic activity.

Light microscopy techniques coupled with biochemical assays elucidate the involvement of SNARE-mediated exocytosis in netrin-dependent axon branching. This combination of techniques permits identification of molecular mechanisms controlling axon branching and cell shape change.

Utilizzando metodologie combinati per definire il ruolo della membrana plasmatica di consegna Durante Axon ramificazione e neuronale morfogenesi

During neural development, growing axons extend to multiple synaptic partners by elaborating axonal branches. Axon branching is promoted by extracellular ...

Using an Adapted Microfluidic Olfactory Chip for the Imaging of Neuronal Activity in Response to Pheromones in Male C. Elegans Head Neurons

The use of calcium indicators has greatly enhanced our understanding of neural dynamics and regulation. The nematode Caenorhabditis elegans, with its completely mapped nervous system and transparent anatomy, presents an ideal model for understanding real-time neural dynamics using calcium indicators. In combination with microfluidic technologies and experimental designs, calcium-imaging studies using these indicators are performed in both free-moving and trapped animals. However, most previous studies utilizing trapping devices, such as the olfactory chip described in Chronis et al., have devices designed for use in the more common hermaphrodite, as the less common male is both morphologically and structurally dissimilar. An adapted olfactory chip was designed and fabricated for increased efficiency in male neuronal imaging with using young adult animals. A turn was incorporated into the worm loading port to rotate the animals and to allow for the separation of the individual neurons within a bilateral pair in 2D imaging. Worms are exposed to a controlled flow of odorant within the microfluidic device, as described in previous hermaphrodite studies. Calcium transients are then analyzed using the open-source software ImageJ. The procedure described herein should allow for an increased amount of male-based C. elegans calcium imaging studies, deepening our understanding of the mechanisms of sex-specific neuronal signaling.

Using an Adapted Microfluidic Olfactory Chip for the Imaging of Neuronal Activity in Response to Pheromones in Male C. Elegans Head Neurons

The use of an adapted &#34;olfactory chip&#34; for the efficient calcium imaging of C. elegans males is described here. Studies of male exposure to glycerol and a pheromone are also shown.

Tramite un Chip olfattiva di microfluidica adattato per l'Imaging dell'attività neuronale in risposta ai feromoni in neuroni di testa maschio C. Elegans

The use of calcium indicators has greatly enhanced our understanding of neural dynamics and regulation. The nematode Caenorhabditis elegans, with its ...