Bmpr1a regulates SuSCs and stem cell-dependent bone formation. (A-L) Kidney capsule transplantation with limiting dilution analysis of control and Bmpr1aAx2 cells, isolated from the P5 suture mesenchyme with Dox treatment from E16.5 to P3, examines SuSC frequency. Ectopic bone formation is assessed by von Kossa staining in whole mounts (A-H) and histology in sections (I-L). (M) Limiting dilution analysis shows the success of bone formation with transplantation of 105, 104, 103, and 102 cells, providing a quantitative estimation for stem cell frequency using ELDA software. (N-O) Sections of the P7 sagittal suture are examined by immunostaining of Axin2 and counterstaining with DAPI. Broken lines define the calvarial bones. (P) The graph shows the average percentage of Axin2-expressing cells in control and mutant sutures (asterisk, p < 0.01, n=3, mean ± SEM, student t-test). Note Axin2+ SuSCs is reduced by Bmpr1a deficiency. Images are representatives of three independent experiments. Scale bars, 4mm (A-J); 200 μm (I-L); 100 μm (N-O).