Extended Data Fig. 6: Cortical bone protects from UV-induced DNA damage.
From: Protection from UV light is an evolutionarily conserved feature of the haematopoietic niche
a, Paraffin section of a D. tinctorius hind leg (from Extended Data Fig., specimen e) after irradiation with UVB post mortem; the leg was severed from the body and irradiated with UVB. The dashed outline represents the cortical bone. Note the higher staining intensity of the anti-CPD antibody in nuclei within the muscle tissue compared to nuclei within the bone marrow. This part of the leg is not yet haematopoietic (compare to Extended Data Fig. 5e, which shows the haematopoietic marrow in the other leg), but contains chondrocytes. Note that even the chondrocyte nuclei closest to the cortical bone are stained much less than the cells outside the cortical bone (arrows from below and from above, respectively). The triangle represents the direction of the UV source; white tip towards UV source. Scale bar, 50 μm. b, Quantification of grey scale values of nuclei inside (n = 17) and outside (n = 41) the cortical bone. Each data point represents the mean grey value of a 16 × 16 pixel circle inside the nucleus, the difference is highly significant (unpaired Student’s two-tailed t-test, P < 0.0001); data are mean ± s.d.
