Figure 5

Clivus development requires osteoclast-osteoblast trans-pairing. (a) Midsagittal plane of a representative micro-CT image of WT mouse skull at P21. Colour bar shows bone mineral density (BMD) levels, from 1 (blue) to 600 (red) mg/cm³. BO, basioccipital bone. Scale bar, 5 mm. Voxel size, 60 μm. (b) Dorsal view of the WT cranial base. Scale bar, 5 mm. (c) Midsagittal plane of a representative micro-CT image from a Tnfsf11^−/− mouse at P21 (n = 6). Colour bar, as in (a). Scale bar, 5 mm. (d) Dorsal view of sample in (c). BMD of BO is higher than that of WT BO. Scale bar, 5 mm. (e) Comparison of basioccipital bones at P3 (blue) and P21 (magenta) in representative micro-CT images from WT mice (P3, n = 4; P21, n = 8). Bone matrix is resorbed on the dorsal side (arrows) and forms on the ventral side (arrowheads) of the basioccipital bone. Dashed lines indicate the clivus angle, as defined by the angle between the chondro-osseous junction (vertical) and the dorsal surface of the basioccipital bone at the midline. The clivus develops towards cervical vertebra 1 (C1). Scale bar, 1 mm. Voxel size, 40 μm (P3) and 60 μm (P21). (f) Analysis similar to (e) in Tnfsf11^−/− mice. Clivus formation is not prominent between P3 (blue) and P21 (magenta). Scale bar, 1 mm. (g) Postnatal temporal changes in clivus angle in WT (closed circles. P3, n = 4; P7, n = 6; P14, n = 4; P21, n = 8) and Tnfsf11^−/− (open squares. P3, n = 3; P7, n = 3; P14, n = 4; P21, n = 6) mice. The data are shown as means ± SD. Day 7, *p = 0.011; Day 14, *p = 0.022; Day 21, ***p = 0.00004.