Gene expression changes in mouse brain after exposure to low‐dose ionizing radiation

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Abstract
Purpose: To characterize the cellular functions associated with the altered transcript profiles of mouse brain exposed to low‐dose in vivo gamma‐irradiation. Materials and methods: Cerebral RNA was isolated at 30 min and 4 h after whole‐body irradiation at 0.1 or 2 Gy, hybridized to random oligonucleotide arrays, and evaluated for time and dose–response patterns by multifactorial analyses. Results: Brain irradiation modulated the expression patterns of 1574 genes, of which 855 showed more than 1.5‐fold variation. about 30% of genes showed dose‐dependent variations, including genes exclusively affected by 0.1 Gy. About 60% of genes showed time‐dependent variation with more genes affected at 30 min than at 4 h. Early changes involved signal transduction, ion regulation and synaptic signalling. Later changes involved metabolic functions including myelin and protein synthesis. Low‐dose radiation also modulated the expression of genes involved in stress response, cell‐cycle control and DNA synthesis/repair. Conclusions: Doses of 0.1 Gy induced changes in gene expression that were qualitatively different from those at 2 Gy. The findings suggest that low‐dose irradiation of the brain induces the expression of genes involved in protective and reparative functions, while down‐modulating genes involved in neural signalling activity.