El apoyo del Instituto Australiano de Ciencia Nuclear e Ingeniería se reconoce. TCK es el ganador de premios AINSE. Laboratorio de Medicina epigenómico el apoyo de la Nacional de Salud y Consejo de Investigación Médica de Australia (566.559). LM con el apoyo de Melbourne de Investigación (Universidad de Melbourne) y de Imágenes Biomédicas becas complementarias CRC. El apoyo de Monash Micro Imaging (Drs. Stephen Cody y Carmichael Iska) fue muy valiosa para este trabajo.

<html> Preparación de células <ol><li> Queratinocitos humanos (FEP-1811) se cultivaron en los queratinocitos-Serum medio libre (K-SFM, Invitrogen) suplementado con factor de crecimiento epidérmico, el extracto de pituitaria bovina y 20 mg / ml de gentamicina, a 37 ° C y CO 2 al 5%. </li><li> Una suspensión de células individuales ha sido preparado por separar con tripsina-EDTA (0,05% v / v) </li><li> Las células fueron sembradas en 8 y Laboratorio de diapositivas Tek II microcámara (10.000 células / pocillo) y las diapositivas se incubaron durante 3 días a 37 º C y 5% CO 2. </li></ol> Irradiación <ol><li> Las células fueron irradiados en el hielo con 2 Gy utilizando una fuente de 137 Cs (Gammacell 1000 irradiador Elite; Nordion Internacional, ON, Canadá; 20,6 segundos / Gy) </li><li> El control no irradiado y 2 Gy células irradiadas se incubaron durante 1 hora a 37 ° C y 5% CO 2. </li></ol> La tinción de inmunofluorescencia <ol><li> Los medios de comunicación fue avisado y se lavaron las células con 300μl de PBS (w / o Ca 2 + o Mg 2 +) por pozo y se gira en un mezclador orbital durante 5 minutos. </li><li> El buffer fue advertido y 100μl de recién preparada 4% (v / v) paraformaldehído se añadió a cada pocillo y las diapositivas se incubaron a temperatura ambiente durante 10 minutos. Todas las incubaciones se realizaron en un canal de tinción humidificado </li><li> Las células fueron lavadas con PBS (w / o Ca 2 + o Mg 2 +). Las láminas fueron colocadas en un frasco de Coplin y se gira en un mezclador orbital durante 5 minutos. Esta etapa de lavado se repitió otras dos veces. </li><li> El buffer fue advertido y el exceso de PBS fue borrada suavemente. </li><li> Las células fueron permeabilized con 100 ml de Triton X-100 (0,1% v / v) por pozo y una incubación de 10 minutos a temperatura ambiente. </li><li> Las células fueron lavadas con PBS (w / o Ca 2 + o Mg 2 +) como se describe en los pasos 3 y 4 anteriores. </li><li> La unión no específica de proteínas fue bloqueado con 100 ml de BSA (1% v / v) por pozo y 20 minutos de incubación a temperatura ambiente. </li><li> El exceso de BSA fue advertido y 100μl de la principal del ratón monoclonal anti-fosfo-histona H2AX de anticuerpos (diluido 1:500, en el 1% de BSA, Millipore), se añadió a cada pocillo de una incubación de 1 hora a temperatura ambiente. </li><li> Las células fueron lavadas con PBS (w / o Ca 2 + o Mg 2 +) como se describe en los pasos 3 y 4 y se incubaron con 100μl del anticuerpo secundario (Alexa Fluor 488 cabra anti-ratón IgG diluido 1:500, en el 1% de BSA ; Invitrogen) por pocillo durante 45 minutos a temperatura ambiente en la oscuridad. (Anticuerpo diluido se mantuvo en la oscuridad durante todo el procedimiento) </li><li> Las células fueron lavadas con PBS (w / o Ca 2 + o Mg 2 +) como se describe en los pasos 3 y 4 anteriores. Sin embargo, la exposición a la luz se redujo al mínimo el uso de aluminio. </li><li> Contratinción nuclear se realizó con 100 ml TOPRO3 (diluido 1:500; Invitrogen) por pozo y una incubación de 10 minutos a temperatura ambiente </li><li> Las células fueron lavadas con PBS (w / o Ca 2 + o Mg 2 +) como se describe en el paso 10. </li><li> Las cámaras fueron cuidadosamente removidos de las diapositivas, el exceso de humedad se borró y las diapositivas se deja secar al aire. </li><li> Una gota de prolongar GOLD anti-fade solución (Invitrogen) se añadió por pocillo y diapositivas montadas fueron (22x50 mm cubreobjetos) y el exceso de líquido alrededor de los bordes de la diapositiva se borró. </li><li> Las diapositivas fueron mantenidos en la oscuridad durante 30 minutos a temperatura ambiente antes de sellar con esmalte de uñas. </li><li> Las diapositivas fueron almacenados durante la noche a 4 ° C en la oscuridad, antes del análisis. </li></ol> Microscopía / Análisis <ol><li> Zeiss LSM510 Meta Confocal Microscpe utiliza para adquirir imágenes con la GFP estándar (por γH2AX - Alexa Fluor 488 cabra anti-IgG de ratón) y el láser rojo lejano (por TOPRO-3). Típicamente, un aceite de 63 x lente objetivo de inmersión se usa. Las imágenes se adquieren en un modelo de la serie Z con un tamaño de paso de 0,5 micras. Un tamaño de paso de 0.5 micras fue elegida para minimizar la pérdida de los actuales focos en diferentes planos en los núcleos. Durante el análisis, los planos individuales son deconvoluted y apilados para producir una imagen proyectada máxima para minimizar la superposición de los focos (Top-hat filtro aplicado). </li><li> Metamorph (Molecular Devices, EE.UU.) se utilizó para analizar el número de focos. El programa cuantifica el número de focos en cada celda después de que el umbral se ha aplicado para excluir a fondo. La información se registra en una hoja de cálculo Microsoft Excel para su posterior análisis. </li></ol><img src="/files/ftp_upload/1957/1957fig1.jpg" alt="Figura 1" /> Figura 1. Visualización de inmunofluorescencia γH2AX focos (verde) en queratinocitos humanos no tratados y en las células irradiadas con 2 Gy y se incubó durante 1 hora a 37 ° C, 5% de CO 2. ADN fue manchado con TOPRO-3 (azul). Las imágenes fueron adquiridas con un Zeiss LSM 510 microscopio confocal Meta. Bar = 10 micras. e_content &quot;&gt; <img src="/files/ftp_upload/1957/1957fig2.jpg" alt="Figura 2" /> Figura 2. Inmunofluorescencia visualización de γH2AX focos (verde) en los queratinocitos humanos y en células irradiadas con 2 Gy y se incubó durante 1 hora a 37 ° C, 5% de CO 2. Las imágenes fueron adquiridas con un Zeiss LSM 510 microscopio confocal Meta con 0,5 micras Z-corte (1-9) para asegurar que todos los focos se han desarrollado. Las imágenes se apilan entonces para la cuantificación utilizando Metamorph. ADN fue manchado con TOPRO-3 (azul). El γH2AX apilados y las imágenes fueron apilados azul para la visualización. Bar = 10 micras.

<ol>
	<li>Rogakou, E. P., Boon, C., Redon, C., Bonner, W. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Megabase+chromatin+domains+involved+in+DNA+double-strand+breaks+in+vivo.">Megabase chromatin domains involved in DNA double-strand breaks in vivo.</a> J. Cell Biol. 146, 905-916 (1999).</li><li>Bonner, W. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gamma+H2AX+and+cancer.">Gamma H2AX and cancer.</a> Nature Reviews Cancer. 8 (12), 957-967 (2008).</li><li>Savic, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Formation+of+Dynamic+[gamma]-H2AX+Domains+along+Broken+DNA+Strands+Is+Distinctly+Regulated+by+ATM+and+MDC1+and+Dependent+upon+H2AX+Densities+in+Chromatin.">Formation of Dynamic [gamma]-H2AX Domains along Broken DNA Strands Is Distinctly Regulated by ATM and MDC1 and Dependent upon H2AX Densities in Chromatin.</a> Molecular Cell. 34 (3), 298-310 (2009).</li><li>Downs, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Binding+of+chromatin-modifying+activities+to+phosphorylated+histone+H2A+at+DNA+damage+sites.">Binding of chromatin-modifying activities to phosphorylated histone H2A at DNA damage sites.</a> Mol Cell. 16 (6), 979-990 (2004).</li><li>Chowdhury, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=[gamma]-H2AX+Dephosphorylation+by+Protein+Phosphatase+2A+Facilitates+DNA+Double-Strand+Break+Repair.">[gamma]-H2AX Dephosphorylation by Protein Phosphatase 2A Facilitates DNA Double-Strand Break Repair.</a> Molecular Cell. 20 (5), 801-809 (2005).</li><li>Nakada, S., Chen, G., Gingras, A., Durocher, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PP4+is+a+gamma+H2AX+phosphatase+required+for+recovery+from+the+DNA+damage+checkpoint.">PP4 is a gamma H2AX phosphatase required for recovery from the DNA damage checkpoint.</a> EMBO Rep. 9 (10), 1019-1026 (2008).</li><li>Altaf, M., Auger, A., Covic, M., C&#244;t&#233;, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Connection+between+histone+H2A+variants+and+chromatin+remodeling+complexes.">Connection between histone H2A variants and chromatin remodeling complexes.</a> Biochem Cell Biol. 87 (1), 35-50 (2009).</li><li>Kusch, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acetylation+by+Tip60+Is+Required+for+Selective+Histone+Variant+Exchange+at+DNA+Lesions.">Acetylation by Tip60 Is Required for Selective Histone Variant Exchange at DNA Lesions.</a> Science. 306, 2084-2087 (2004).</li><li>Hurlin, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Progression+of+human+papillomavirus+type+18-immortalized+human+keratinocytes+to+a+malignant+phenotype.">Progression of human papillomavirus type 18-immortalized human keratinocytes to a malignant phenotype.</a> Proc Natl Acad Sci U S A. 88 (2), 570-574 (1991).</li><li>Dickey, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=H2AX:+functional+roles+and+potential+applications.">H2AX: functional roles and potential applications.</a> Chromosoma. , (2009).</li></ol>

Después de la exposición a la radiación ionizante (rayos γ), γH2AX forma rápida los focos y los números de focos de alcanzar un máximo entre los 30-60 minutos 2. Por lo tanto, nuestra una hora después de la irradiación punto del tiempo refleja la formación inicial del OSD. Hemos utilizado la dosis de radiación clínicamente relevante de 2 Gy para nuestro experimento. Sin embargo, el método puede ser utilizado para la dosis de radiación hasta 4 Gy para la detección de la formación inicial del OSD; superposición significativa de los focos se opone a la cuantificación exacta de las dosis más altas. Mayores dosis de radiación se puede utilizar por más tiempo de incubación después de la irradiación, como γH2AX focos se han perdido debido a una reparación, lo que resulta en un número cuantificable. Por lo general, cuatro horas y hasta 24 horas después de la irradiación tiempos de incubación se utilizan para la reparación de control de ADN. Hemos utilizado el ADN de la mancha TOPRO-3 debido a las limitaciones en los láseres de excitación de nuestro microscopio confocal. Más comúnmente, 4,6-diamidino-2-phenylindole dihidrocloruro (DAPI) se utiliza para contratinción nuclear. A pesar de que utiliza un microscopio confocal, microscopio de epifluorescencia con z-el corte de la capacidad es adecuada. El método de inmunofluorescencia es adecuado para el cáncer de otros adherentes y líneas celulares normales, hemos probado T98G glioblastoma humano y normal de las células endoteliales humanas y de rata H9c2 miocitos del ventrículo embrionario. Por último, la cuantificación de γH2AX es útil en el contexto de las radiaciones ionizantes inducida por daño en el ADN, de los daños el control de ADN como se ilustra en el experimento y la reparación (sensibilidad a la radiación). El ensayo es también útil para evaluar la eficacia de los compuestos que modulan la respuesta celular a la radiación (es decir, los protectores de la radiación y sensibilizadores). Además, γH2AX está surgiendo como un potencial marcador molecular en el envejecimiento y la enfermedad, sobre todo en el cáncer 10.

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		<div>
		<table border="1">
		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>Keratinocyte-Serum Free Medium (K-SFM)</td>
<td>Media</td>
<td>Invitrogen</td>
<td>17005042</td>
<td>Keratinocyte media supplemented with human recombinant Epidermal Growth Factor 1-53 (EGF 1-53), and Bovine Pituitary Extract (BPE).</td>
</tr>
<tr>
<td>Lab Tek lI Chamber Slides (8-well)</td>
<td>Chamber Slides</td>
<td>Nunc Denmark</td>
<td>NUN154534</td>
<td>&nbsp;</td>
<tr>
<td>Coverslips (22x50mm)</td>
<td>Coverslips</td>
<td>Menzel-Gl&auml;ser</td>
<td>CS2250100</td>
<td>&nbsp;</td>
<tr>
<td>Bovine Serum Albumin (BSA)</td>
<td>&nbsp;</td>
<td>Sigma-Aldrich</td>
<td>A7906</td>
<td>BSA (1%) is used to block any non-specific antibody binding. Primary and secondary antibodies are diluted in BSA.</td>
</tr>
<tr>
<td>PBS (without Ca2+ and Mg2+)</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>17-517Q</td>
<td>&nbsp;</td>
<tr>
<td>0.5% Trypsin-EDTA x10</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>15400-054</td>
<td>Trypsin-EDTA (0.05%) used to detach cells from culture flasks.</td>
</tr>
<tr>
<td>Triton X-100</td>
<td>Reagent</td>
<td>Sigma-Aldrich</td>
<td>T8787</td>
<td>Triton X-100 (0.1%) used to permeabilise cells.</td>
</tr>
<tr>
<td>Paraformaldehyde</td>
<td>Reagent</td>
<td>Sigma-Aldrich</td>
<td>158127</td>
<td>Paraformaldehyde (4%) used to fix cells.</td>
</tr>
<tr>
<td>Mouse monoclonal anti-phospho histone-H2AX antibody</td>
<td>Primary Antibody</td>
<td>Millipore</td>
<td>16193</td>
<td>Dilution of primary antibody (1:500), in 1% BSA.</td>
</tr>
<tr>
<td>Alexa Fluor 488 goat anti-mouse IgG (H+L)</td>
<td>Secondary Antibody</td>
<td>Invitrogen</td>
<td>11029</td>
<td>Dilution of secondary antibody (1:500), in 1% BSA.</td>
</tr>
<tr>
<td>TOPRO3</td>
<td>DNA Stain</td>
<td>Invitrogen</td>
<td>T3605</td>
<td>DNA stain commonly used: 4,6-diamidino-2-phenylindole dihydrochloride (DAPI). Can only be used with microscopes with the appropriate excitation laser.</td>
</tr>
<tr>
<td>ProLong Gold</td>
<td>Anti-fade solution</td>
<td>Invitrogen</td>
<td>P36930</td>
<td>Refractive index of 1.42 at 20&deg;C.</td>
</tr>
<tr>
<td>Tissue Culture Flask, Vented Cap</td>
<td>Culture Flask</td>
<td>BD Falcon</td>
<td>353112</td>
<td>&nbsp;</td>
<tr>
<td>Tissue Culture Dish (150x25mm)</td>
<td>Petridish</td>
<td>BD Falcon</td>
<td>353025</td>
<td>&nbsp;</td>
<tr>
<td>Coplin Jar, glass</td>
<td>&nbsp;</td>
<td>Grale Scientific P/L</td>
<td>1771-OG</td>
<td>&nbsp;</td>
<tr>
<td>Staining Trough</td>
<td>&nbsp;</td>
<td>Grale Scientific P/L</td>
<td>V1991.99</td>
<td>&nbsp;</td>
<tr>
<td>Gammacell 1000 Elite Irradiator</td>
<td>Gamma Irradiator</td>
<td>Nordion International Inc.</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Zeiss LSM 510 Meta Confocal</td>
<td>Confocal Microscope</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Metamorph</td>
<td>Software for Imaging analysis</td>
<td>Molecular Devices, USA</td>
<td>&nbsp;</td>
<td>&nbsp;</td>		</tbody>
		</table>
		</div>

quantification of &gamma;h2ax foci in response to ionising radiation

ADN de doble filamento se rompe (DSBs), que son inducidas por cualquiera de los procesos metabólicos endógenos o por causas exógenas, son una de las lesiones del ADN más críticos con respecto a la supervivencia y la preservación de la integridad genómica. Una primera respuesta a la inducción de DSBs es la fosforilación de la variante de la histona H2A, H2AX, en la serina-139 de residuos, en el altamente conservadas C-terminal motivo SQEY, formando γH2AX<sup&gt; 1</sup&gt;. Después de la inducción de DSBs, H2AX es rápidamente fosforilado por la fosfatidil-inosito 3-quinasa (PIKK) de la familia de las proteínas, la ataxia telangiectasia mutada (ATM), el ADN-proteína de la subunidad catalítica y la quinasa ATM y RAD3 relacionados (ATR)<sup&gt; 2</sup&gt;. Por lo general, sólo unos pocos pares de bases (pb) están implicados en un OSD, sin embargo, no hay amplificación de la señal significativa, dada la importancia de las modificaciones de la cromatina en la señalización de daño en el ADN y la reparación. La fosforilación de H2AX mediada predominantemente por ATM se extiende a las áreas adyacentes de la cromatina, que afecta a aproximadamente 0,03% del total de H2AX celulares por OSD<sup&gt; 2,3</sup&gt;. Esto corresponde a la fosforilación de aproximadamente 2000 moléculas H2AX que abarca ~ 2 Mbps regiones de la cromatina que rodea el sitio de la OSD y los resultados en la formación de focos discretos γH2AX que pueden ser fácilmente visualizados y cuantificados por microscopía de inmunofluorescencia<sup&gt; 2</sup&gt;. La pérdida de γH2AX al OSD refleja reparación, sin embargo, existe cierta controversia en cuanto a lo que define la reparación completa de DSBs, se ha propuesto que la reincorporación de las dos hebras de ADN es suficiente sin embargo, también se ha sugerido que restablecimiento de la cromatina estado original de la compactación es necesario<sup&gt; 8.4</sup&gt;. La desaparición de γH2AX implica al menos en parte, defosforilación por fosfatasas, fosfatasa 2A y 4C fosfatasa<sup&gt; 5,6</sup&gt;. Además, la eliminación de γH2AX de redistribución que implican el intercambio de histonas con H2A.Z se ha implicado<sup&gt; 7,8</sup&gt;. Es importante destacar que el análisis cuantitativo de los focos γH2AX ha llevado a una amplia gama de aplicaciones en la investigación médica y la energía nuclear. Este sentido, demuestran el método más comúnmente utilizado de inmunofluorescencia para la evaluación de daños en el ADN inicial de detección y cuantificación de γH2AX focos en γ-irradiados queratinocitos humanos adherentes<sup&gt; 9</sup&gt;.

Watch this Scientific Journal Video about Quantification of ÃŽÂ³H2AX Foci in Response to Ionising Radiation at JoVE.com

Quantification of &#947;H2AX Foci in Response to Ionising Radiation

La cuantificación de ADN de doble filamento con la formación de estrías γH2AX como un marcador molecular se ha convertido en una herramienta indispensable en la biología de la radiación. Aquí se demuestra el uso de un ensayo de inmunofluorescencia para la cuantificación de γH2AX focos después de la exposición de las células a la radiación.

La cuantificación de γH2AX focos en respuesta a la radiación ionizante

DNA double-strand breaks (DSBs), which are induced by either endogenous metabolic processes or by exogenous sources, are one of the most critical DNA ...

quantification-of-h2ax-foci-in-response-to-ionising-radiation

Nanyang Technological University

Research

JoVE Journal

Biology

Quantification of &gamma;H2AX Foci in Response to Ionising Radiation

20.3K vistas.  The Alfred Medical Research and Education Precinct. La cuantificación de ADN de doble filamento con la formación de estrías γH2AX como un marcador molecular se ha convertido en una herramienta indispensable en la biología de la radiación. Aquí se demuestra el uso de un ensayo de inmunofluorescencia para la cuantificación de γH2AX focos después de la exposición de las células a la radiación.

Video: Quantification of γH2AX Foci in Response to Ionising Radiation

Quantitation of &gamma;H2AX Foci in Tissue Samples

DNA double-strand breaks (DSBs) are particularly lethal and genotoxic lesions, that can arise either by endogenous (physiological or pathological) processes or by exogenous factors, particularly ionizing radiation and radiomimetic compounds. Phosphorylation of the H2A histone variant, H2AX, at the serine-139 residue, in the highly conserved C-terminal SQEY motif, forming &gamma;H2AX, is an early response to DNA double-strand breaks1. This phosphorylation event is mediated by the phosphatidyl-inosito 3-kinase (PI3K) family of proteins, ataxia telangiectasia mutated (ATM), DNA-protein kinase catalytic subunit and ATM and RAD3-related (ATR)2. Overall, DSB induction results in the formation of discrete nuclear &gamma;H2AX foci which can be easily detected and quantitated by immunofluorescence microscopy2. Given the unique specificity and sensitivity of this marker, analysis of &gamma;H2AX foci has led to a wide range of applications in biomedical research, particularly in radiation biology and nuclear medicine. The quantitation of &gamma;H2AX foci has been most widely investigated in cell culture systems in the context of ionizing radiation-induced DSBs. Apart from cellular radiosensitivity, immunofluorescence based assays have also been used to evaluate the efficacy of radiation-modifying compounds. In addition, &gamma;H2AX has been used as a molecular marker to examine the efficacy of various DSB-inducing compounds and is recently being heralded as important marker of ageing and disease, particularly cancer3. Further, immunofluorescence-based methods have been adapted to suit detection and quantitation of &gamma;H2AX foci ex vivo and in vivo4,5. Here, we demonstrate a typical immunofluorescence method for detection and quantitation of &gamma;H2AX foci in mouse tissues.

Quantitation of &#947;H2AX Foci in Tissue Samples

Quantitation of DNA double-strand breaks on the basis of &gamma;H2AX foci has become an invaluable tool, particularly in radiation biology, for the evaluation of tissue radiosensitivity and effects of radiation modifying compounds. Here we demonstrate the use of an immunofluorescence assay for quantitation of &gamma;H2AX foci in tissue samples.

La cuantificación de γH2AX focos en muestras de tejido

DNA double-strand breaks (DSBs) are particularly lethal and genotoxic lesions, that can arise either by endogenous (physiological or pathological) ...

Investigación

Biología

Evaluation of the Spatial Distribution of &gamma;H2AX following Ionizing Radiation

An early molecular response to DNA double-strand breaks (DSBs) is phosphorylation of the Ser-139 residue within the terminal SQEY motif of the histone H2AX1,2. This phosphorylation of H2AX is mediated by the phosphatidyl-inosito 3-kinase (PI3K) family of proteins, ataxia telangiectasia mutated (ATM), DNA-protein kinase catalytic subunit and ATM and RAD3-related (ATR)3. The phosphorylated form of H2AX, referred to as &gamma;H2AX, spreads to adjacent regions of chromatin from the site of the DSB, forming discrete foci, which are easily visualized by immunofluorecence microscopy3. Analysis and quantitation of &gamma;H2AX foci has been widely used to evaluate DSB formation and repair, particularly in response to ionizing radiation and for evaluating the efficacy of various radiation modifying compounds and cytotoxic compounds4.
Given the exquisite specificity and sensitivity of this de novo marker of DSBs, it has provided new insights into the processes of DNA damage and repair in the context of chromatin. For example, in radiation biology the central paradigm is that the nuclear DNA is the critical target with respect to radiation sensitivity. Indeed, the general consensus in the field has largely been to view chromatin as a homogeneous template for DNA damage and repair. However, with the use of &gamma;H2AX as molecular marker of DSBs, a disparity in &gamma;-irradiation-induced &gamma;H2AX foci formation in euchromatin and heterochromatin has been observed5-7. Recently, we used a panel of antibodies to either mono-, di- or tri- methylated histone H3 at lysine 9 (H3K9me1, H3K9me2, H3K9me3) which are epigenetic imprints of constitutive heterochromatin and transcriptional silencing and lysine 4 (H3K4me1, H3K4me2, H3K4me3), which are tightly correlated actively transcribing euchromatic regions, to investigate the spatial distribution of &gamma;H2AX following ionizing radiation8. In accordance with the prevailing ideas regarding chromatin biology, our findings indicated a close correlation between &gamma;H2AX formation and active transcription9. Here we demonstrate our immunofluorescence method for detection and quantitation of &gamma;H2AX foci in non-adherent cells, with a particular focus on co-localization with other epigenetic markers, image analysis and 3D-modeling.

Evaluation of the Spatial Distribution of &#947;H2AX following Ionizing Radiation

Microscopic analysis of &gamma;H2AX foci, which form following the phosphorylation of H2AX at Ser-139 in response to DNA double-strand breaks, has become an invaluable tool in radiation biology. Here we used an antibody to mono-methylated histone H3 at lysine 4 as an epigenetic marker of actively transcribing euchromatin, to evaluate the spatial distribution of radiation-induced &gamma;H2AX formation within the nucleus.

Evaluación de la distribución espacial de la radiación ionizante γH2AX siguientes

An early molecular response to DNA double-strand breaks (DSBs) is phosphorylation of the Ser-139 residue within the terminal SQEY motif of the histone ...

Polarized Translocation of Fluorescent Proteins in Xenopus Ectoderm in Response to Wnt Signaling

Cell polarity is a fundamental property of eukaryotic cells that is dynamically regulated by both intrinsic and extrinsic factors during embryonic development 1, 2. One of the signaling pathways involved in this regulation is the Wnt pathway, which is used many times during embryogenesis and critical for human disease3, 4, 5. Multiple molecular components of this pathway coordinately regulate signaling in a spatially-restricted manner, but the underlying mechanisms are not fully understood. Xenopus embryonic epithelial cells is an excellent system to study subcellular localization of various signaling proteins. Fluorescent fusion proteins are expressed in Xenopus embryos by RNA microinjection, ectodermal explants are prepared and protein localization is evaluated by epifluorescence. In this experimental protocol we describe how subcellular localization of Diversin, a cytoplasmic protein that has been implicated in signaling and cell polarity determination6, 7 is visualized in Xenopus ectodermal cells to study Wnt signal transduction8. Coexpression of a Wnt ligand or a Frizzled receptor alters the distribution of Diversin fused with red fluorescent protein, RFP, and recruits it to the cell membrane in a polarized fashion 8, 9. This ex vivo protocol should be a useful addition to in vitro studies of cultured mammalian cells, in which spatial control of signaling differs from that of the intact tissue and is much more difficult to analyze.

Polarized Translocation of Fluorescent Proteins in Xenopus Ectoderm in Response to Wnt Signaling

Xenopus embryonic ectoderm has become an attractive model for studies of cell polarity. An assay is described, in which subcellular distribution of fluorescent proteins is assessed in ectoderm cells. This protocol will help address questions related to spatial control of signaling.

Translocación polarizado de proteínas fluorescentes en Xenopus Ectodermo en respuesta a la señalización de Wnt

Cell polarity is a fundamental property of eukaryotic cells that is dynamically regulated by both intrinsic and extrinsic factors during embryonic ...

Two- and Three-Dimensional Live Cell Imaging of DNA Damage Response Proteins

Double-strand breaks (DSBs) are the most deleterious DNA lesions a cell can encounter. If left unrepaired, DSBs harbor great potential to generate mutations and chromosomal aberrations1. To prevent this trauma from catalyzing genomic instability, it is crucial for cells to detect DSBs, activate the DNA damage response (DDR), and repair the DNA. When stimulated, the DDR works to preserve genomic integrity by triggering cell cycle arrest to allow for repair to take place or force the cell to undergo apoptosis. The predominant mechanisms of DSB repair occur through nonhomologous end-joining (NHEJ) and homologous recombination repair (HRR) (reviewed in2). There are many proteins whose activities must be precisely orchestrated for the DDR to function properly. Herein, we describe a method for 2- and 3-dimensional (D) visualization of one of these proteins, 53BP1.
The p53-binding protein 1 (53BP1) localizes to areas of DSBs by binding to modified histones3,4, forming foci within 5-15 minutes5. The histone modifications and recruitment of 53BP1 and other DDR proteins to DSB sites are believed to facilitate the structural rearrangement of chromatin around areas of damage and contribute to DNA repair6. Beyond direct participation in repair, additional roles have been described for 53BP1 in the DDR, such as regulating an intra-S checkpoint, a G2/M checkpoint, and activating downstream DDR proteins7-9. Recently, it was discovered that 53BP1 does not form foci in response to DNA damage induced during mitosis, instead waiting for cells to enter G1 before localizing to the vicinity of DSBs6. DDR proteins such as 53BP1 have been found to associate with mitotic structures (such as kinetochores) during the progression through mitosis10.
In this protocol we describe the use of 2- and 3-D live cell imaging to visualize the formation of 53BP1 foci in response to the DNA damaging agent camptothecin (CPT), as well as 53BP1's behavior during mitosis. Camptothecin is a topoisomerase I inhibitor that primarily causes DSBs during DNA replication. To accomplish this, we used a previously described 53BP1-mCherry fluorescent fusion protein construct consisting of a 53BP1 protein domain able to bind DSBs11. In addition, we used a histone H2B-GFP fluorescent fusion protein construct able to monitor chromatin dynamics throughout the cell cycle but in particular during mitosis12. Live cell imaging in multiple dimensions is an excellent tool to deepen our understanding of the function of DDR proteins in eukaryotic cells.

This protocol describes a method for visualizing a DNA double-strand break signaling protein activated in response to DNA damage as well as its localization during mitosis.

De dos y tres dimensiones imágenes de células vivas de las proteínas de respuesta al daño del ADN

Double-strand breaks (DSBs) are the most deleterious DNA lesions a cell can encounter. If left unrepaired, DSBs harbor great potential to generate ...

Quantification of Orofacial Phenotypes in Xenopus

Xenopus has become an important tool for dissecting the mechanisms governing craniofacial development and defects. A method to quantify orofacial development will allow for more rigorous analysis of orofacial phenotypes upon abrogation with substances that can genetically or molecularly manipulate gene expression or protein function. Using two dimensional images of the embryonic heads, traditional size dimensions-such as orofacial width, height and area- are measured. In addition, a roundness measure of the embryonic mouth opening is used to describe the shape of the mouth. Geometric morphometrics of these two dimensional images is also performed to provide a more sophisticated view of changes in the shape of the orofacial region. Landmarks are assigned to specific points in the orofacial region and coordinates are created. A principle component analysis is used to reduce landmark coordinates to principle components that then discriminate the treatment groups. These results are displayed as a scatter plot in which individuals with similar orofacial shapes cluster together. It is also useful to perform a discriminant function analysis, which statistically compares the positions of the landmarks between two treatment groups. This analysis is displayed on a transformation grid where changes in landmark position are viewed as vectors. A grid is superimposed on these vectors so that a warping pattern is displayed to show where significant landmark positions have changed. Shape changes in the discriminant function analysis are based on a statistical measure, and therefore can be evaluated by a p-value. This analysis is simple and accessible, requiring only a stereoscope and freeware software, and thus will be a valuable research and teaching resource.

Quantification of Orofacial Phenotypes in Xenopus

A method to quantify the orofacial size and shape of Xenopus laevis embryos has been developed. In this protocol, traditional size measurements are combined with geometric morphometrics to allow for more sophisticated analyses of orofacial development and defects.

La cuantificación de fenotipos en Orofacial<em&gt; Xenopus</em

Xenopus has become an important tool for dissecting the mechanisms governing craniofacial development and defects. A method to quantify orofacial ...

Measuring Glutathione-induced Feeding Response in Hydra

Hydra is among the most primitive organisms possessing a nervous system and chemosensation for detecting reduced glutathione (GSH) for capturing the prey. The movement of prey organisms causes mechanosensory discharge of the stinging cells called nematocysts from hydra, which are inserted into the prey. The feeding response in hydra, which includes curling of the tentacles to bring the prey towards the mouth, opening of the mouth and consequent engulfing of the prey, is triggered by GSH present in the fluid released from the injured prey. To be able to identify the molecular mechanism of the feeding response in hydra which is unknown to date, it is necessary to establish an assay to measure the feeding response. Here, we describe a simple method for the quantitation of the feeding response in which the distance between the apical end of the tentacle and mouth of hydra is measured and the ratio of such distance before and after the addition of GSH is determined. The ratio, called the relative tentacle spread, was found to give a measure of the feeding response. This assay was validated using a starvation model in which starved hydra show an enhanced feeding response in comparison with daily fed hydra.

Here we describe a simple assay for the quantification of the feeding response in hydra induced by the reduced form of glutathione. This assay relies on measuring the distance between the apical end of the tentacle and mouth of hydra.

Medición inducida glutatión-Alimentación Respuesta en Hydra

Hydra is among the most primitive organisms possessing a nervous system and chemosensation for detecting reduced glutathione (GSH) for capturing the prey. ...

Quantitation of Endothelial Cell Adhesiveness In Vitro

One of the cardinal processes of inflammation is the infiltration of immune cells from the lumen of the blood vessel to the surrounding tissue. This occurs when endothelial cells, which line blood vessels, become adhesive to circulating immune cells such as monocytes. In vitro measurement of this adhesiveness has until now been done by quantifying the total number of monocytes that adhere to an endothelial layer either as a direct count or by indirect measurement of the fluorescence of adherent monocytes. While such measurements do indicate the average adhesiveness of the endothelial cell population, they are confounded by a number of factors, such as cell number, and do not reveal the proportion of endothelial cells that are actually adhesive. Here we describe and demonstrate a method which allows the enumeration of adhesive cells within a tested population of endothelial monolayer. Endothelial cells are grown on glass coverslips and following desired treatment are challenged with monocytes (that may be fluorescently labeled). After incubation, a rinsing procedure, involving multiple rounds of immersion and draining, the cells are fixed. Adhesive endothelial cells, which are surrounded by monocytes are readily identified and enumerated, giving an adhesion index that reveals the actual proportion of endothelial cells within the population that are adhesive.

Quantitation of Endothelial Cell Adhesiveness In Vitro

We report an in vitro method that allows the quantitation of the actual number of adhesive cells within an endothelial cell monolayer.

La cuantificación de la adhesividad de la célula endotelial<em&gt; In Vitro</em

One of the cardinal processes of inflammation is the infiltration of immune cells from the lumen of the blood vessel to the surrounding tissue. This ...

Experimental Approaches to Study Mitochondrial Localization and Function of a Nuclear Cell Cycle Kinase, Cdk1

Although mitochondria possess their own transcriptional machinery, merely 1% of mitochondrial proteins are synthesized inside the organelle. The nuclear-encoded proteins are transported into mitochondria guided by their mitochondria targeting sequences (MTS); however, a majority of mitochondrial localized proteins lack an identifiable MTS. Nevertheless, the fact that MTS can instruct proteins to go into the mitochondria provides a valuable tool for studying mitochondrial functions of normally nuclear and/or cytoplasmic proteins. We have recently identified the cell cycle kinase CyclinB1/Cdk1 complex in the mitochondria. To specifically study the mitochondrial functions of this complex, mitochondrial overexpression and knock-down of this complex without interfering with its nuclear or cytoplasmic functions were essential. By tagging CyclinB1/Cdk1 with MTS, we were able to achieve mitochondrial overexpression of this complex to study its mitochondrial targets as well as functions. Via tagging dominant-negative Cdk1 with MTS, inhibition of Cdk1 activity was accomplished particularly in the mitochondria. Potential mitochondrial targets of CyclinB1/Cdk1 complex were identified using a gel-based proteomics approach. Unlike traditional 2D gel analysis, we employed 2-dimensional difference gel electrophoresis (2D-DIGE) technology followed by phosphoprotein staining to fluorescently label differentially phosphorylated proteins in mitochondrial Cdk1 expressing cells. Identification of phosphoprotein spots that were altered in wild type versus dominant negative Cdk1 bearing mitochondria revealed the identity of mitochondrial targets of Cdk1. Finally, to determine the effect of CyclinB1/Cdk1 mitochondrial localization in cell cycle progression, a cell proliferation assay using a synthetic thymidine analogue EdU (5-ethynyl-2&#8242;-deoxyuridine) was used to monitor the cells as they go through the cell cycle and replicate their DNA. Altogether, we demonstrated a variety of approaches available to study mitochondrial localization and activity of a cell cycle kinase. These are advanced, yet easy to follow methods that will be beneficial to many cell biology researchers.

Here, we outline how to study mitochondrial localization of a (cell cycle) kinase, and how to determine its sub-mitochondrial location as well as potential mitochondrial substrates/targets. Forced expression of proteins into the mitochondria provides a useful tool for studying the functional consequences of mitochondrial localization of a protein of interest.

Los enfoques experimentales para estudiar mitocondrial localización y función de un ciclo celular quinasa nuclear, Cdk1

Although mitochondria possess their own transcriptional machinery, merely 1% of mitochondrial proteins are synthesized inside the organelle. The ...

Examination of Proteins Bound to Nascent DNA in Mammalian Cells Using  BrdU-ChIP-Slot-Western Technique

Histone deacetylases 1 and 2 (HDAC1,2) localize to the sites of DNA replication. In the previous study, using a selective inhibitor and a genetic knockdown system, we showed novel functions for HDAC1,2 in replication fork progression and nascent chromatin maintenance in mammalian cells. Additionally, we used a BrdU-ChIP-Slot-Western technique that combines chromatin immunoprecipitation (ChIP) of bromo-deoxyuridine (BrdU)-labeled DNA with slot blot and Western analyses to quantitatively measure proteins or histone modification associated with nascent DNA.
Actively dividing cells were treated with HDAC1,2 selective inhibitor or transfected with siRNAs against Hdac1 and Hdac2 and then newly synthesized DNA was labeled with the thymidine analog bromodeoxyuridine (BrdU). The BrdU labeling was done at a time point when there was no significant cell cycle arrest or apoptosis due to the loss of HDAC1,2 functions. Following labeling of cells with BrdU, chromatin immunoprecipitation (ChIP) of histone acetylation marks or the chromatin-remodeler was performed with specific antibodies. BrdU-labeled input DNA and the immunoprecipitated (or ChIPed) DNA was then spotted onto a membrane using the slot blot technique and immobilized using UV. The amount of nascent DNA in each slot was then quantitatively assessed using Western analysis with an anti-BrdU antibody. The effect of loss of HDAC1,2 functions on the levels of newly synthesized DNA-associated histone acetylation marks and chromatin remodeler was then determined by normalizing the BrdU-ChIP signal obtained from the treated samples to the control samples.

In this protocol, we describe a novel BrdU-ChIP-Slot-Western technique to examine proteins and histone modifications associated with newly synthesized or nascent DNA.

El examen de las proteínas unidas al ADN naciente en células de mamífero utilizando BrdU-chip-Slot-occidental Técnica

Histone deacetylases 1 and 2 (HDAC1,2) localize to the sites of DNA replication. In the previous study, using a selective inhibitor and a genetic ...

High Resolution Quantification of Crystalline Cellulose Accumulation in Arabidopsis Roots to Monitor Tissue-specific Cell Wall Modifications

Plant cells are surrounded by a cell wall, the composition of which determines their final size and shape. The cell wall is composed of a complex matrix containing polysaccharides that include cellulose microfibrils that form both crystalline structures and cellulose chains of amorphous organization. The orientation of the cellulose fibers and their concentrations dictate the mechanical properties of the cell. Several methods are used to determine the levels of crystalline cellulose, each bringing both advantages and limitations. Some can distinguish the proportion of crystalline regions within the total cellulose. However, they are limited to whole-organ analyses that are deficient in spatiotemporal information. Others relying on live imaging, are limited by the use of imprecise dyes. Here, we report a sensitive polarized light-based system for specific quantification of relative light retardance, representing crystalline cellulose accumulation in cross sections of Arabidopsis thaliana roots. In this method, the cellular resolution and anatomical data are maintained, enabling direct comparisons between the different tissues composing the growing root. This approach opens a new analytical dimension, shedding light on the link between cell wall composition, cellular behavior and whole-organ growth.

High Resolution Quantification of Crystalline Cellulose Accumulation in Arabidopsis Roots to Monitor Tissue-specific Cell Wall Modifications

Crystalline cellulose is an important constituent of the plant cell wall. However, its quantification at a cellular resolution is technically challenging. Here, we report the use of polarized light technology and root cross sections to obtain information of cell wall composition at a spatiotemporal resolution.

Alta resolución Cuantificación de celulosa cristalina acumulación en<em&gt; Arabidopsis</em&gt; Las raíces para monitorear la célula específica de tejido de pared Modificaciones

Plant cells are surrounded by a cell wall, the composition of which determines their final size and shape. The cell wall is composed of a complex matrix ...