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.