Chromosomal aberrations

Genetic effects of charged particles

The exposure of cells to ionising radiations such as X-rays, γ-rays or charged particles can result in an injury of different cellular constituents including DNA. DNA, which carries the genetic information of the cell, is the most critical target. In higher organisms the DNA is organised in chromosomes. During interphase (growth phase of the cell) the chromosomes are long, thin threads that are individually indistinguishable.  During cell division (mitosis) chromosomes reach their highest degree of condensation. In this stage chromosomes are usually examined by light microscopy.

The number and types of aberrations provide valuable on the possible health risks associated with radiation exposure such as cancer induction. This is particularly important for the planning of manned missions to Moon and Mars (Lee et. al. 2005) and for the application of particle beams in cancer therapy (Nasonova and Ritter 2004). Furthermore, aberration yields are used to estimate the dose to which an individual has been accidentally exposed (retrospective biological dosimetry).

Presently, at GSI the cytogenetic effects of C^- to Fe ions are studied in mammalian cells such as human lymphocytes and fibroblasts. Chromosome aberrations are measured in conventional metaphase samples as well as in interphase cells following premature chromosome condensation (e.g. Nasonova et al. 2004, Nasonova and Ritter 2004). Damages are visualised after solid staining or by the painting of particular chromosomes applying Fluorescence in situ hybridisation. Examples are shown in figures 1-3.

Our investigations cover both the induction of aberrations in the first cell generation after exposure and the transmission of aberrations to later cell generations. Furthermore, cell-type specific factors modifying the expression of aberrations such as apoptosis (lymphocytes) or premature differentiation (fibroblasts) are investigated to gain deeper insights into the fate of injured cells.

fig. 1

Detection of aberrations by solid staining. The cell (human lymphocyte) carries a dicentric chromosome accompanied by a fragment.   

fig. 2

 Analysis of aberrations by two-colour fluorescence in situ hybridisation. Here, chromosomes 2 (red) and 4 (green) were painted, the other chromosomes are counterstained and appear blue. The cell (human fibroblast) carries a reciprocal translocation involving chromosome 2. This is seen as a bicolour chromosome (red/blue).

fig. 3

 Detection of aberrations by multicolour fluorescence in situ hybridisation. Here, the karyotype of a human fibroblast with multiple aberrations is shown.

contact: s.rittergsi.de