The support of the Australian Institute of Nuclear Science and Engineering is acknowledged. TCK was the recipient of AINSE awards. Epigenomic Medicine Lab is supported by the National Health and Medical Research Council of Australia (566559). LM is supported by Melbourne Research (University of Melbourne) and Biomedical Imaging CRC supplementary scholarships. The support of Monash Micro Imaging (Drs Stephen Cody and I&#347;ka Carmichael) was invaluable for this work.

Cell Preparation
<ol>
 <li>Human keratinocytes (FEP-1811) were grown in Keratinocyte-Serum Free Medium (K-SFM; Invitrogen) supplemented with epidermal growth factor, bovine pituitary extract and 20 &mu;g/ml gentamicin, at 37&deg;C and 5% CO2.</li>
 <li>A single cell suspension was prepared by detaching with trypsin-EDTA (0.05% v/v) </li>
 <li>Cells were seeded in 8-well Lab Tek II microchamber slides (10,000 cells/well) and slides were incubated for 3 days at 37&deg;C and 5% CO2. </li>
</o...

<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>

No conflicts of interest declared.

Following exposure to ionising radiation (&gamma;-rays), &gamma;H2AX foci form rapidly and foci numbers reach a maximum between 30-60 minutes2. Therefore, our 1 hour post-irradiation time point reflects initial DSB formation. We have used the clinically relevant radiation dose of 2 Gy for our experiment. However, the method can be used for radiation doses up to 4 Gy for detection of initial DSB formation; significant overlap of foci precludes accurate quantitation at higher doses. Higher radiation doses may be...

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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

DNA double-strand breaks (DSBs), which are induced by either endogenous metabolic processes or by exogenous sources, are one of the most critical DNA lesions with respect to survival and preservation of genomic integrity. An early response to the induction of DSBs is phosphorylation of the H2A histone variant, H2AX, at the serine-139 residue, in the highly conserved C-terminal SQEY motif, forming &gamma;H2AX1. Following induction of DSBs, H2AX is rapidly phosphorylated by the phosphatidyl-inosito 3-kinase (PIKK) family of proteins, ataxia telangiectasia mutated (ATM), DNA-protein kinase catalytic subunit and ATM and RAD3-related (ATR)2. Typically, only a few base-pairs (bp) are implicated in a DSB, however, there is significant signal amplification, given the importance of chromatin modifications in DNA damage signalling and repair. Phosphorylation of H2AX mediated predominantly by ATM spreads to adjacent areas of chromatin, affecting approximately 0.03% of total cellular H2AX per DSB2,3. This corresponds to phosphorylation of approximately 2000 H2AX molecules spanning ~2 Mbp regions of chromatin surrounding the site of the DSB and results in the formation of discrete &gamma;H2AX foci which can be easily visualized and quantitated by immunofluorescence microscopy2. The loss of &gamma;H2AX at DSB reflects repair, however, there is some controversy as to what defines complete repair of DSBs; it has been proposed that rejoining of both strands of DNA is adequate however, it has also been suggested that re-instatement of the original chromatin state of compaction is necessary4-8. The disappearence of &gamma;H2AX involves at least in part, dephosphorylation by phosphatases, phosphatase 2A and phosphatase 4C5,6. Further, removal of &gamma;H2AX by redistribution involving histone exchange with H2A.Z has been implicated7,8. Importantly, the quantitative analysis of &gamma;H2AX foci has led to a wide range of applications in medical and nuclear research. Here, we demonstrate the most commonly used immunofluorescence method for evaluation of initial DNA damage by detection and quantitation of &gamma;H2AX foci in &gamma;-irradiated adherent human keratinocytes9.

Watch this Scientific Journal Video about Quantification of Î³H2AX Foci in Response to Ionising Radiation at JoVE.com

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

Quantification of DNA double-strand streaks using &gamma;H2AX formation as a molecular marker has become an invaluable tool in radiation biology. Here we demonstrate the use of an immunofluorescence assay for quantification of &gamma;H2AX foci after exposure of cells to radiation.

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

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

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20.2K visualizações.  The Alfred Medical Research and Education Precinct. Quantificação de DNA dupla fita-estrias usando formação γH2AX como um marcador molecular tornou-se uma ferramenta valiosa na biologia da radiação. Aqui mostramos o uso de um teste de imunofluorescência para a quantificação dos focos γH2AX após a exposição das células à radiação.