title: Induction of linear tracks of DNA double-strand breaks by alpha-particle irradiation of cells.
abstract: Understanding how cells maintain genome integrity when challenged with DNA double-strand breaks (DSBs) is of major importance, particularly since the discovery of multiple links of DSBs with genome instability and cancer-predisposition disorders. Ionizing radiation is the agent of choice to produce DSBs in cells; however, targeting DSBs and monitoring changes in their position over time can be difficult. Here we describe a procedure for induction of easily recognizable linear arrays of DSBs in nuclei of adherent eukaryotic cells by exposing the cells to alpha particles from a small Americium source (Box 1). Each alpha particle traversing the cell nucleus induces a linear array of DSBs, typically 10-20 DSBs per 10 mum track length. Because alpha particles cannot penetrate cell-culture plastic or coverslips, it is necessary to irradiate cells through a Mylar membrane. We describe setup and irradiation procedures for two types of experiments: immunodetection of DSB response proteins in fixed cells grown in Mylar-bottom culture dishes (Option A) and detection of fluorescently labeled DSB-response proteins in living cells irradiated through a Mylar membrane placed on top of the cells (Option B). Using immunodetection, recruitment of repair proteins to individual DSB sites as early as 30 s after irradiation can be detected. Furthermore, combined with fluorescence live-cell microscopy of fluorescently tagged DSB-response proteins, this technique allows spatiotemporal analysis of the DSB repair response in living cells. Although the procedures might seem a bit intimidating, in our experience, once the source and the setup are ready, it is easy to obtain results. Because the live-cell procedure requires more hands-on experience, we recommend starting with the fixed-cell application.
authors.affiliation: Center for Microscopical Research, Department of Cell Biology and Histology, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands. j.stap@amc.uva.nl
authors.forename: Jan
authors.initials: J
authors.lastname: Stap
authors.forename: Przemek M
authors.initials: PM
authors.lastname: Krawczyk
authors.forename: Carel H
authors.initials: CH
authors.lastname: Van Oven
authors.forename: Gerrit W
authors.initials: GW
authors.lastname: Barendsen
authors.forename: Jeroen
authors.initials: J
authors.lastname: Essers
authors.forename: Roland
authors.initials: R
authors.lastname: Kanaar
authors.forename: Jacob A
authors.initials: JA
authors.lastname: Aten
mesh_terms: D000512:Alpha Particles; D000576:Americium; D045744:Cell Line, Tumor; D004247:DNA / Q000528:radiation effects*; D004249:DNA Damage; D006801:Humans
chemical_list: D004247:DNA; D000576:Americium