title: Radiation dose determines the method for quantification of DNA double strand breaks.
abstract: Ionizing radiation induces DNA double strand breaks (DSBs) that trigger phosphorylation of the histone protein H2AX (γH2AX). Immunofluorescent staining visualizes formation of γH2AX foci, allowing their quantification. This method, as opposed to Western blot assay and Flow cytometry, provides more accurate analysis, by showing exact position and intensity of fluorescent signal in each single cell. In practice there are problems in quantification of γH2AX. This paper is based on two issues: the determination of which technique should be applied concerning the radiation dose, and how to analyze fluorescent microscopy images obtained by different microscopes. HTB140 melanoma cells were exposed to γ-rays, in the dose range from 1 to 16 Gy. Radiation effects on the DNA level were analyzed at different time intervals after irradiation by Western blot analysis and immunofluorescence microscopy. Immunochemically stained cells were visualized with two types of microscopes: AxioVision (Zeiss, Germany) microscope, comprising an ApoTome software, and AxioImagerA1 microscope (Zeiss, Germany). Obtained results show that the level of γH2AX is time and dose dependent. Immunofluorescence microscopy provided better detection of DSBs for lower irradiation doses, while Western blot analysis was more reliable for higher irradiation doses. AxioVision microscope containing ApoTome software was more suitable for the detection of γH2AX foci.
authors.affiliation: Vinča Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia.
authors.forename: Tanja
authors.initials: T
authors.lastname: Bulat
authors.affiliation: Vinča Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia.
authors.forename: Otilija
authors.initials: O
authors.lastname: Keta
authors.affiliation: Vinča Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia.
authors.forename: Lela
authors.initials: L
authors.lastname: Korićanac
authors.affiliation: Vinča Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia.
authors.forename: Jelena
authors.initials: J
authors.lastname: Žakula
authors.affiliation: Vinča Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia.
authors.forename: Ivan
authors.initials: I
authors.lastname: Petrović
authors.affiliation: Vinča Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Ristić-Fira
authors.affiliation: Faculty of Medical Sciences, University of Kragujevac, Kragujevac, Serbia.
authors.forename: Danijela
authors.initials: D
authors.lastname: Todorović
mesh_terms: D015153:Blotting, Western; D045744:Cell Line, Tumor / Q000528:radiation effects; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D006657:Histones / Q000528:radiation effects*; D006801:Humans; D008545:Melanoma / Q000532:radiotherapy*; D008856:Microscopy, Fluorescence; D010766:Phosphorylation; D011874:Radiometry / Q000379:methods*
chemical_list: C468783:H2AX protein, human; D006657:Histones