Radiation Induced Chromatin Conformation Changes Analysed by Fluorescent Localization Microscopy, Statistical Physics, and Graph Theory
Panel A. The figure shows the radial radial distribution function for H3K4 antibodies representing euchromatin (methylated histone variants) for non-irradiated and irradiated cells. Error bars represent the standard deviation of the mean value after averaging over the sample of cells. The value for g(r) at small distances goes up to around 20, indicating the high marker densities during repair. The rapid drop off of the radial distribution function within a distance of about 50 nm shows that euchromatin forms small clustered areas. Upon exposure to 0.5 Gy γ-irradiation, a change in the correlation function can be observed in cells that were imaged after 30 min and 48 hrs. The value at small radial distances increases compared to non-irradiated cells. This indicates that the density in the euchromatic regions becomes on average higher in irradiated cells. Panel B. The distribution of edge lengths in the Delaunay triangulation of the markers confirms these observations. A sharp peak in the distribution at around 30 nm can be seen in untreated cells. In 48 h post-irradiation cells, the peak spreads slightly.