This project builds further on previously gathered knowledge within the Radiobiology Unit and aims to establish a mechanistic link between early effects of acute radiation exposure of mouse embryos and late effects in adult mice. The objectives of the project will be to evaluate:
(1) the exact role of p53 and some of its targets in the development of radiation-induced microcephaly;
(2) whether this microcephaly is related to the observed cognitive defects at adult age;
(3) whether these morphological and cognitive defects may be prevented by pharmacological inhibition of p53 at the time of radiation exposure.
The first two aims will be investigated using neuron-specific p53 knock-out mice in comparison with their wild-type littermates. These mice will be bred at the new SCK•CEN animal facility, and will have an inactive p53 gene, specifically in neurons of the cerebral cortex. Using magnetic resonance imaging and behavioral tests, we will evaluate whether they also develop microcephaly and behavioral defects after prenatal radiation exposure. Possible mechanisms will be investigated using immunohistochemistry for apoptosis, neuronal differentiation, and neuronal migration.
Furthermore, we will investigate the function of some recently discovered p53 targets (Quintens et al., accepted and under revision) using primary neuronal cell cultures (in vitro), or zebrafish embryos (in vivo). We will investigate their function in the DNA damage response (cell cycle, DNA repair, apoptosis), neuronal differentiation and brain development, both under normal and DNA damaging conditions. For this, we will silence these genes using either small interfering RNA (in vitro) or morpholino (in vivo) technology.
For the third aim, we will treat pregnant mice with a pharmacological p53 inhibitor, such as alpha-pifithrin (PFT), at the time of irradiation. PFT has already been shown to reduce the genotoxic side effects of radiation treatment on healthy tissue in mice. As for the brain-specific p53 knock-outs, we will firstly investigate the brain size and behavior of the progeny of PFT-treated, irradiated mice. Furthermore, we will assess whether PFT-treated mice have a greater risk for developing radiation-induced cancer in order to evaluate the suitability of PFT as a potential drug for pregnant women undergoing radiation therapy. These results might have important implications for radiation protection of pregnant women and their unborn babies.