Analysis of the transcription factors Mash1 and Pax6 following X-ray irradiation. The quantification of Mash1 (A) (n=5 mice) and Pax6 (B) (n=5 mice) expression in the ON, for different time points post X-ray irradiation, showed a peak at 24 hours for both transcription factors (Mash1:F(5,12) = 9.239, p = 0.0008; Pax6:F(5,16 )= 4.9991, p = 0.0061). Mash1 staining in C, control, E, 24 hours and G, 1 week post X-ray irradiation. There was nuclear expression of Mash1 in OSNs (white arrows) and sustentacular cells (open arrow). Pax6 staining in D, control, F, 24 hours and H, 1 week post X-ray irradiation. Pax6 localisation appeared in the nuclei of OSNs (white arrows) in controls (D), and 24 hours (F) and 1 week (H) post-irradiation. In particular, 24 hours post-irradiation, Pax6-positive nuclei appeared in the sustentacular cell layer (open arrow). Most of the Pax6 immunoreactivity appeared in the bowl-like areas of the ON. Dashed line indicates basal lamina. All sections have nuclei counterstained with DAPI (blue). Scale bars: C,E,G, 50 μm; D,F,H, 30 μm. * p ≤ 0.05, ** p ≤ 0.01.