Figure 1.

Prx1-CreERT mediated tracing and Bmpr1a ablation in adult mice. (a) Schedule for TAM administration to 2-month-old mice. TAM was injected to both Prx1-CreERT; Bmpr1a^f/f and Bmpr1a^f/f mice (age- and sex-matched littermates) on every other day for 3 doses. One month after the last Tam injection, bone tissues were retrieved and analyzed. (b) Tissue specificity and effectiveness of Cre recombinase in Prx1-CreERT; Rosa-tdTomato mice. Osteoblasts and osteocytes as well as the endosteal and periosteal surfaces of bones were labeled by tdTomato fluorescent signals. N = 3 mice, Scale bar = 200 μm. (c) In vitro analysis revealed tdTomato + bone marrow BM-MSCs (left panel) with the potential to differentiate into ALP-positive osteoblasts (right panel). Lower panel indicates higher magnification of upper panel. Upper panel scale bar = 100 μm and lower panel scale bar = 50 μm. (d) Quantitative real-time RT-PCR analysis of BM-MSCs showed that Bmpr1a was deleted (>70%) in the mutant mice. (e) Immunoblotting of bone extracts also confirmed a reduction in the level of Bmpr1a and phosphorylated-Smad 1/5/8. Left panel: Representative Western blots; Right panel: Quantification of relative protein expressions (from three repeated experiments) plotted in the graph as fold change. N = 4 mice/group; ^*P < 0.05. For the full-length blots see Supplementary Fig. S1.