Embryology Research Today is a free monthly online journal that collates and summarizes the latest research about Embryology, including details on stem cells, reproduction, transplants, cloning.

Quantification of ionizing radiation-induced cell death in situ in a vertebrate embryo.

Bladen CL, Flowers MA, Miyake K, Podolsky RH, Barrett JT, Kozlowski DJ, Dynan WS

Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA 30912, USA.

Quantitative studies of radiation cytotoxicity have been performed mostly in cells in culture. For a variety of reasons, however, the response of cells in culture may not reflect the response for cells in situ in a whole organism. We describe here an approach for quantification of radiation-induced cell death in vivo using the transparent embryo of the zebrafish, Danio rerio, as a model vertebrate system. Using this system, we show that the number of TUNEL-positive cells within a defined region increases approximately linearly with radiation dose up to 1 Gy. The results are consistent with predictions of a linear-quadratic model. The use of alternative models, accommodating a response threshold or low-dose hypersensitivity, did not significantly improve the fit to the observed data. Attenuation of the expression of the 80-kDa subunit of Ku, an essential protein for the nonhomologous end-joining pathway of repair, led to a dose reduction of 30- to 34-fold, possibly approaching the limit where each double-strand break causes a lethal hit. In both the Ku80-attenuated and the control embryos, apoptotic cells were distributed uniformly, consistent with a cell-autonomous mechanism of cell death. Together, these results illustrate the potential of the zebrafish for quantitative studies of radiation-induced cell death during embryogenesis and in vivo.

Published 19 July 2007 in Radiat Res, 168(2): 149-57.
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