Regensburg 2013 – scientific programme

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BP: Fachverband Biologische Physik

BP 11: Posters: Statistical Physics in Biological Systems (joint with DY)

BP 11.15: Poster

Monday, March 11, 2013, 17:30–19:30, Poster B2

Measuring structural changes in chromatin induced by ionizing radiation: an analysis of localization microscopy images — •Yang Zhang¹, Gabriell Máté¹, Sabina Hillebrandt², Patrick Müller², Michael G. Hausmann², and Dieter W. Heermann¹ — ¹Institute for Theoretical Physics, Heidelberg University, Germany — ²Kirchhoff-Institute for Physics, Heidelberg University, Germany

The elaborate cell response to the arising of DNA double-strand breaks caused by ionizing radiation (IR) involves local remodeling and structural changes of the surrounding chromatin. In particular, experiments indicate different repair characteristics in heterochromatin (HC) and euchromatin (EC). However, there is still no detailed understanding of these changes of the genome organization. In this work we analyzed localization microscopy images by means of statistical physics and graph theory to provide a quantitative description of structural changes induced by IR. HeLa cells were exposed to different doses of IR. Positions of fluorescence stained nucleosomes were determined using localization microscopy. Simultaneously, markers of modified histones indicating HC or EC were localized. We then calculated the pair correlation functions as well as edge length distributions and mean coordination numbers for graphs obtained by triangulations of the marker positions. Our results show that HC regions undergo a relaxation immediately after exposure to ionizing radiation while EC regions show the opposite behavior. We further demonstrate that at later times after irradiation these alterations become less pronounced.