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The γ-H2AX assay

The γ-H2AX assay scores DNA double strand breaks by quantifying phosphorylation of the histone H2AX which co-localizes to them. For the γ-H2AX analysis, both images of Hoechst stained nuclei and the γ-H2AX foci, visualized with Alexa Fluor 555 are acquired. Rather than counting foci, as is the standard procedure at low doses, but which saturates around 2 Gy, the RABiT analysis scores the total fluorescence in each nucleus. This modification allows scoring doses up to 8 Gy or more.

Although not useful for diagnosing acute exposures, due to the 24-48h persistence of the γ-H2AX signal, we have seen that this is a good marker for both probing radiation sensitivity and for quantifying chronic exposures (e.g. to ingested 137Cs).

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Center for High-Throughput Minimally-Invasive Radiation Biodosimetry