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 Feromônio Produção <ol><li> Crescer OP50 E. coli a partir de uma única colónia O / N a 37 ° C, agitando, em 100 ml de caldo LB a 200 rpm. NOTA: Este cultura D / N pode ser feito com antecedência e guardadas a 4 ° C. </li><li> Crescer N2 C. elegans em junho 15-20 cm placas de Petri contendo ágar NGM (ver receita na Tabela 1) inoculadas com 50 ul de E. OP50 coli até que as bactérias está quase esgotada 19. </li><li> Faça 5x 250 ml de S mídia (ver receita na Tabela 1) em 1 L frascos Erlenmeyer de 19. NOTA: Esta solução pode ser feita com antecedência. </li><li> Crescer uma cultura de OP50 E. coli em 4 L de caldo LB S / N por meio da inoculação de 1 ml de OP50 em E. coli e agitação a 37 ° C durante 16 horas. </li><li> Lave os nematóides das placas (passo 1.2) com 1 ml de solução S basal (ver receita na Tabela 1) e nematóides de transferência de 4-5 placas em cada um dos quatro frascos de 1 L de Erlenmeyer com os meios de comunicação S preparada no passo 1.3 (4 5 placaspara cada frasco) 19. </li><li> Centrifuga-se o passo de OP50 1,4 a 650 xg durante 10 min e remover o sobrenadante. Ressuspender cada sedimento bacteriano em 10 ml de solução de S basal. Transferir quantidades iguais de bactérias em suspensão para cada frasco de nematóides. </li><li> Colocar os frascos num agitador orbital, à temperatura ambiente (20 - 25 ° C) e 100 - 150 rpm durante 4-5 dias, até que a solução começa a limpar, indicando uma exaustão de alimentos. </li><li> Uma vez que a comida está esgotado, crescer outra cultura O / N de OP50 E. coli em 4x 1 L de caldo de LB. Centrifuga-se as bactérias a 650 xg durante 10 min e adicionar uma pelete a partir de um balão para cada um dos frascos S media com nematóides. Devolver os frascos S de mídia para o agitador orbital, como no passo 1.7, por mais 3-4 dias até que o alimento está esgotado novamente. </li><li> Tomar um ~ alíquota de 1 ml de solução de cada frasco e estimar a concentração de nemátodos por sub-amostragem de 1 ul de cada alíquota de 1 ml e a contagem do número de nemátodos. NOTA: Opopulação do nematóide deve ser 50.000 - 75.000 nematóides / ml. A esta concentração, a maior parte dos nemátodes são dauers. </li><li> Descarte qualquer frascos contaminados. NOTA: Contaminação frequentemente se manifesta como hifas fúngicas visto durante a etapa 1.9. </li><li> Nemátodos de centrifugar a 4000 xg durante 10 min a 4 ° C. Desprezar o pelete nemátodo e reter o sobrenadante. Alternativamente, consulte a discussão para o uso desses animais para fazer um feromônio de baixa potência. </li><li> Filtrar o sobrenadante com # 1 filtro de papel Whatman. NOTA: uma garrafa térmica vai acelerar este processo. </li><li> Além disso filtrar o sobrenadante através de unidades de filtração de 0,45 um vácuo estéril. NOTA: O filtrado pode ser mantido O / N a 4 ° C ou prosseguir para 1,14. </li><li> Adicionar-se o filtrado para uma proveta de 2 L com uma barra de agitação. Coloque em um exaustor em uma placa de aquecimento mexa. Deixe ferver, mexendo e evaporar a cerca de 200 ml. Transferir a solução para um copo de 500 ml. Prosseguir a ebulição até cerca de 50 ml são lepés NOTA: Cuidados devem ser tomados durante este passo como é possível que a solução para transbordar. A cor dos finais de 50 ml é um castanho escuro. Em qualquer altura durante o processo de cozimento, o calor pode ser desligado e o filtrado foi armazenado O / N à temperatura ambiente ou a 4 ° C. </li><li> Deixar arrefecer e centrifugar durante 5 minutos a 1000 x g. Verter o sobrenadante para uma proveta de 100 ml e descartar o sedimento. </li><li> Ferva o sobrenadante até uma crosta marrom. Retire do fogo e quebrar a crosta com uma espátula. Adicionar suficiente de etanol prova 200 para cobrir a casca. Cobrir o copo com Parafilm e deixe descansar O / N à temperatura ambiente. Deitar fora o etanol em um copo limpo e colocado para o lado. Adicionar etanol fresco para cobrir a casca. Repita extrações O / N 3 vezes. Reúnem-se os extratos. </li><li> Usar uma bomba de vácuo para secar os extractos de etanol. Se uma bomba de vácuo não está disponível, adicionar o extracto de etanol para um recipiente limpo e quente a 50 ° C com agitação numa hotte. NOTA: Uma vez que o etanol tenha evaporado um resíduo pegajoso de lcor marrom ight deve permanecer. Se o aquecimento é usado, deve ser tomado cuidado para não queimar a solução por meio de aquecimento por muito tempo. </li><li> Dissolve-se resíduo em 10 ml de água destilada estéril. Filtro de esterilizar a solução com um filtro de seringa de 0,22 um e armazenar a -20 ° C em alíquotas de 1 ml. NOTA: 1 ml de água é utilizada para dissolver o resíduo, para cada 100 ml de cultura inicial de nemátodos líquido. Por exemplo, se um dos frascos de cultura líquido é rejeitado devido a contaminação, em seguida, ajustar a quantidade de água utilizada para dissolver o resíduo. </li></ol> 2 Determinação do Feromônio Dose Response <ol><li> Prepare dauer feromona fazendo 6x 5 ml de meio de agar com NGM Noble, sem peptona, e suplementado com 50 ug / ml de sulfato de estreptomicina e uma gama de dauer feromona (ver receita na Tabela 1) 4, 19. Misturar os componentes num 13x100 mm tubo de cultura de vidro, ferver mais um bico de Bunsen, em seguida, despeje em 3 centímetros placas de Petri. </li><li> Pesar amtubo icrocentrifuge. Adicionar 1 ml de cultura O / N do E. coli OP50 para o tubo e centrifuga-se a 17.000 x g ~ em um tubo de microcentrífuga. Remover todo o sobrenadante. Pesa-se o tubo de novo e determinar o peso do sedimento de bactérias. Ressuspender o sedimento com tampão M9 (ver receita na Tabela 1) para uma concentração final de 4% (w / v). Aliquota de 10 ul da suspensão bacteriana sobre o centro de cada placa 4 de feromonas. Placas de loja O / N à temperatura ambiente. </li><li> Escolha 10-15 grávidas N2 do tipo selvagem hermafroditas, um dia após a muda até a idade adulta para as placas de feromônio 4. Armazenar as placas a 25 ° C durante 3-4 horas. </li><li> Escolha fora de todos os hermafroditas adultos. Registre o número de ovos postos por cada placa. Selar as placas com parafilme e regresso a 25 ° C durante 3 dias 17. </li><li> Contagem da percentagem de dauers (Figura 2). Nota: Para ambos os métodos, é importante notar que dauers (e, em menor extenda não dauers) vai subir as paredes e na tampa de placas de Petri. Por isso, é importante examinar todas as superfícies do prato para nematóides. </li><li> Ajustar os dados a uma curva de dose-resposta e calcular a concentração de EC90 de feromona (feromona suficiente para induzir 90% de animais para formar dauers) como mostrado na Figura 3 Nota:. Nós normalmente utilizam um modelo de regressão logística para estimar a CE 90 , mas diferentes pacotes de software de estatística pode ter métodos alternativos que produzem estimativas similares. </li></ol> 3 Imagens ao vivo de Dauer IL2 Neurônios <ol><li> Prepare pratos Dauer feromônio como no protocolo 2, utilizando o valor de EC 90 determinou na etapa 2.6. </li><li> Induzir dauers usando os métodos no protocolo 2 com uma cepa carregando um IL2 repórter transgene integrado (myIs13 [P klp-6 :: GFP], myIs14 [P klp-6 :: GFP], myIs16 [P <em&gt; KLP-6 :: tdTomato] ou qIs56 [P lag-2 :: GFP]) 12, 20, 21. NOTA: Se q Is56 é usada, a expressão de GFP não será visível nos IL2Qs até várias horas para a muda Dauer e alguns dos eventos de remodelação iniciais não será visível. Além disso, enquanto o sinal de fluorescência a partir do desfasamento P-2 :: transgene GFP em última análise, é mais brilhante nos IL2s durante dauer que os P-6 klp repórteres fluorescentes, o desfasamento P-2 :: transgene gfp também fracamente expressa nos músculos da cabeça que pode mascarar os ramos IL2 finas. </li><li> Após a postura dos ovos, remover os hermafroditas adultos, selar as placas com parafilme e incubar durante 34 horas a 25 ° C 17. NOTA: O período de tempo para a muda Dauer varia ligeiramente entre os indivíduos. O período mais rápido de dendrito arborização começa 4-5 horas após o início da muda Dauer (39-44pós h a 25 ° C) 12, que estabelece-ovo. </li><li> O dia antes da imagem, formam uma solução de 10% (w / v) de agarose em tampão M9 com dauer feromona para a concentração EC90. Alíquota de aproximadamente 100 mL de agarose numa lâmina de microscópio e rapidamente, mas com cuidado, coloque outro slide na parte superior para criar uma superfície plana agarose. Após a agarose solidificou, enrole os slides em saran wrap e armazenar em uma câmara de umidade (caixa ponteira com papel-toalha molhada). </li><li> Após o período de incubação 34 h, examinar as placas de feromônio para nematóides que pararam de bombeamento da faringe. Lâminas separadas de tal forma que apenas uma superfície de uma lâmina de agarose tem nele. Escolher um ou mais nematóides numa almofada de agarose a 10% e 1 μ l de 0,1 micron esferas de poliestireno de 22. NOTA: Com uma população bem sincronizados, a maioria dos nematóides sobre a placa será entrar na muda de L2D de dauer. No entanto, pode haver variação entre indivíduos. Por isso, é importante observar características adicionais (oclusão do estoma, a remodelação da faringe) para estimar a quantidade de tempo que os animais tenham sido dentro da muda Dauer (ver resultados representativos, por exemplo). </li><li> Determinar a orientação (esquerda / direita, dorsal / ventral) do nematóide. Capturar imagens Z-stack de um dendrito IL2Q em 100x com a menor intensidade de fluorescência possível a cada 15 minutos ou quando necessário para o experimento específico. Continue a captura de imagens até que o nematóide se separou da cutícula L2D e imobilização é impossível ou se o animal se recupera de Dauer (faringe começa bombeamento). Quando não imaginando ativamente, coloque o slide em uma câmara de umidade. NOTA: Nós usamos um microscópio de epifluorescência com uma motorizada contraste fase e de interferência diferencial (DIC) óptica. </li></ol>

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The authors have nothing to disclose

Um exame de neuroplasticidade específicos de dauer e outras alterações morfológicas associadas à Dauer requer controlada e fiável a formação de dauers quer através de mutação genética (mutantes ou seja, daf-c) ou por exposição de animais de tipo selvagem de feromona. Enquanto a utilização de uma mutação genética para induzir dauers é conveniente, pode confundir os resultados. Assim, os dados coletados com mutações daf-C deve ser posteriormente confirmada com tipo selvagem animais ...

Plasticidade fenotípica, inclusive plasticidade do desenvolvimento e comportamental, é importante para as adaptações a condições ambientais adversas e é considerada uma força motriz na evolução 1. C. elegans é um organismo modelo frequentemente utilizado para estudos em desenvolvimento e neurobiologia. Sob condições ideais, C. elegans, desenvolvido em quatro fases larvares antes de entrar na fase adulta reprodutiva. No entanto, em condições de baixa disponibilidade de alimentos e altas densidades populacionais, C. elegans pode sofrer uma chave de desenvolvimento e entrar em um estágio Dauer longa vida e estresse resistente 2. Dauers exibir várias diferenças morfológicas e comportamentais de não-dauers que provavelmente medeiam esta resistência ao estresse. Os estímulos ambientais e vias genéticas que regulam a entrada Dauer têm sido amplamente descrito 3, 4, 5, 6, 7. Contudo, os mecanismos moleculares que controlam alterações fenotípicas individuais que ocorrem dformação Dauer urante são menos conhecidas. O exame de fenótipos específicos de Dauer requer a produção de animais dauer. Isto pode ser realizado de três maneiras: 1) colheita de uma cultura de C. fome elegans, 2) Utilização de formação dauer constitutiva (daf-c) mutantes, 3) indução da formação, através de feromonas dauer purificado. É relativamente simples para escolher dauers de uma placa com um padrão NGM C. população elegans que esgotou a sua bacteriana-abastecimento alimentar. Nas nossas mãos, uma placa NGM padrão originalmente semeada com 50 ul de OP50 Escherichia coli, deixou-se crescer durante 3 dias e em seguida inoculados com 3 - hermafroditas 4 adultos mantida a 25 ° C irá esgotar a fonte de alimento dentro de uma semana e produzem vários milhares dauers dentro de 3 dias adicionais (além de inúmeras não-dauers famintas). No entanto, este método não é satisfatório para os processos de exame que ocorrem durante a muda em dAuer. É difícil determinar qual dos vários milhares de animais em um prato típico faminto estão entrando em Dauer. Além disso, o uso de uma placa de fome oferece qualquer possibilidade de sincronização. A utilização de mutantes daf-c permite a sincronização e a geração segura de dauers. No entanto, não há qualquer garantia de que uma mutação daf-c em particular não irá afectar outros fenótipos específicos de Dauer sozinho ou em combinação com outras mutações. A presença de um feromônio dauer estava implícito pela primeira vez por Cassada e Russell e mais tarde demonstrado por Dourado e Riddle. A feromona dauer já foi caracterizada quimicamente 2, 8, 9, 10. A feromona purificado é constituído por uma mistura complexa de ascarosides, que em diferentes formas de regular a ambos os processos comportamentais e de desenvolvimento 9, 11. Utilização de um extracto bruto de feromonas dauer permite a indução controlada fiável do dauers sincronizados num fundo de tipo selvagem. </p&gt; O sistema nervoso e as células gliais associadas sofrer remodelação durante Dauer larva formação 12, 13, 14. Algumas dessas mudanças são irreversíveis, como a remodelação das células da glia durante Dauer 13, 14. Porém outros eventos de remodelação são reversíveis após um retorno à favorável condições ambientais. Por exemplo, um conjunto de quatro neurônios IL2Q sofrer remodelação neuronal rápida e reversível durante a formação Dauer incluindo: arborização dendrito, a transferência do único dendrítica de neurônios e axônios multidendritic remodelação 12. Os métodos aqui permitem a imagiologia in vivo de confiança de neuroplasticidade induzida pelo stress num modelo de organismo. Os métodos apresentados para a produção e teste de feromona dauer bruto são descritos anteriormente e compilada a partir de várias fontes de 4, 8, 15, 16, 17, 18.

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			<td height="40" style="height:40px;width:259px;">N2 C. elegans Bristol strain</td>
			<td style="width:152px;">Caenorhabditis Genetics Center</td>
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		</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

Os mecanismos que controlam a plasticidade fenotípica induzida por estresse em animais são muitas vezes complexas e difíceis de estudar in vivo. Um exemplo clássico de plasticidade induzida por estresse é a fase de Dauer C. elegans. Dauers estão numa fase de desenvolvimento larvar alternativa formada em condições de baixas concentrações de alimentos de bactérias e concentrações elevadas de uma feromona dauer. Dauers exibir extensa plasticidade do desenvolvimento e comportamental. Por exemplo, um conjunto de quatro quadrante interno-labial (IL2Q) neurônios passam por extensa remodelação reversível durante a formação Dauer. Utilizando a entrada de potenciais vias de regulação dauer bem conhecido, um método previamente estabelecido para a produção de dauer bruto feromona de culturas em larga escala de nematóides líquido é demonstrada. Com este método, uma concentração de 50.000 - 75.000 nemátodos / ml de líquido de cultura é suficiente para produzir uma altamente potente feromona dauer bruto. A potência de feromonas em bruto é determined por um bioensaio de resposta à dose. Por fim, os métodos utilizados para in vivo de lapso de tempo de imagem dos IL2Qs durante a formação Dauer são descritos.

A produção de resultados Dauer bruto feromônio em um líquido amarelo (Figura 1) que é tanto calor e frio estável. Alíquotas de feromona bruto são armazenadas a -20 ° C indefinidamente sem qualquer perda na actividade óbvia. Após a produção da feromona, um único bioensaio de dose-resposta é suficiente para uma estimativa da potência. No entanto, para a maioria das experiências, é necessário repetir o bioensaio de 2 - 3 vezes e ter uma média de cada experimento. Os resultados represent...

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 de imagens de Dauer específica Neuronal Remodelação em 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

11.1K visualizações.  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. 

Vídeo: 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.

Transfecção de células de camundongo por Ganglionares da Retina In vivo Eletroporação

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

Neurociência

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 axotomia em C. elegans

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

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.

Quantificação automatizada de fluorescência em 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.

Dois registros eletrofisiológicos de sinapticamente evocadas Respostas astroglial e neuronal em fatias hipocampais agudas

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.

Na imagem cálcio vivo Neuronal em 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.

Rápido Micro-iontoforese de glutamato e GABA: uma ferramenta útil para investigar Integração 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 da Neuronal Vesicles 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.

Utilizando metodologias combinadas para definir o papel do Plasma Membrane entrega durante Axon Ramificação e Neuronal morfogênese

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.

Usando um Chip olfativo Microfluidic adaptado para a imagem da atividade Neuronal em resposta aos Pheromones em neurônios de cabeça masculino C. Elegans

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

Quantitative Approaches for Scoring in vivo Neuronal Aggregate and Organelle Extrusion in Large Exopher Vesicles in C. elegans

Toxicity of misfolded proteins and mitochondrial dysfunction are pivotal factors that promote age-associated functional neuronal decline and neurodegenerative disease across species. Although these neurotoxic challenges have long been considered to be cell-intrinsic, considerable evidence now supports that misfolded human disease proteins originating in one neuron can appear in neighboring cells, a phenomenon proposed to promote pathology spread in human neurodegenerative disease.
C. elegans adult neurons that express aggregating proteins can extrude large (~4 &#181;m) membrane-surrounded vesicles that can include the aggregated protein, mitochondria, and lysosomes. These large vesicles are called &#8220;exophers&#8221; and are distinct from exosomes (which are about 100x smaller and have different biogenesis). Throwing out cellular debris in exophers may occur by a conserved mechanism that constitutes a fundamental, but formerly unrecognized, branch of neuronal proteostasis and mitochondrial quality control, relevant to processes by which aggregates spread in human neurodegenerative diseases.
While exophers have been mostly studied in animals that express high copy transgenic mCherry within touch neurons, these protocols are equally useful in the study of exophergenesis using fluorescently tagged organelles or other proteins of interest in various classes of neurons.
Described here are the physical features of C. elegans exophers, strategies for their detection, identification criteria, optimal timing for quantitation, and animal growth protocols that control for stresses that can modulate exopher production levels. Together, details of protocols outlined here should serve to establish a standard for quantitative analysis of exophers across laboratories. This document seeks to serve as a resource in the field for laboratories seeking to elaborate molecular mechanisms by which exophers are produced and by which exophers are reacted to by neighboring and distant cells.

Quantitative Approaches for Scoring in vivo Neuronal Aggregate and Organelle Extrusion in Large Exopher Vesicles in C. elegans

This protocol describes approaches for detection and quantitation of large aggregate and/or organelle extrusions (~4 &#181;m) produced by C. elegans cells in the form of membrane-bound exophers. We describe strains, growth conditions, scoring criteria, timing, and microscopy considerations needed to facilitate dissection of this debris expulsion mechanism.