Fig. 2: Ex vivo live imaging of bone expansion reveals progressive differentiation of osteoblasts.
From: Self-propagating wave drives morphogenesis of skull bones in vivo
A Max projection of Osx1-GFP::Cre labeled frontal bone at 0 h (E13.75) and 6 h, together with the osteogenic front (magenta) and individually tracked cells (cyan). Scale bar = 100 µm. B The relative displacement for the osteogenic front (magenta) and tracked cells (cyan) over the course of 6 h starting from E13.75, defined as the displacement normalized by the total displacement of the osteogenic front at 6 h. Shaded areas show SEMs (N = 4, n = 199 tracked cells). C Box plot with all individual data points of rate of expansion at the osteogenic front compared to that of tracked cells, computed from the same data as in (B). The center represents the mean, and the bounds represent the standard error. D Average GFP intensity profiles along the medial-lateral axis for a labeled frontal bone in an ex vivo imaging experiment starting at E13.75. Each graph arises from one time frame, with the color indicated in the legend. E GFP labeling scheme in Osx1-GFP::Cre; R26RmT/mG explants. F Representative fixed tissue image of Osx1-GFP::Cre; R26RmT/mG (N = 6). The arrows with solid outline indicate cells that have both membrane and nuclear stain, and the arrow with dashed outline indicates a cell with only nuclear stain. G Max projections showing GFP localization in E13.75 live movies of Osx1-GFP::Cre; R26RmT/mG explants at 5 h time intervals. Scale bars = 50 µm. H Schematic of a coronal section with the bone labeled in cyan. The inset shows the imaged areas of I with the approximate domains of Sp7+ osteoblasts (cyan) and Runx2+ precursor cells (magenta). I DAPI, Runx2, and SP7 immunoreactivity at the osteogenic front in E14.5 coronal sections (N = 8).
