Figure 3.

Loss of Asxl1 in Pre-osteoblasts and Their Progenies Leads to BOS-like Phenotypes in Mice

(A) High-resolution X-ray images demonstrate runting of OsxCre;Asxl1^Δ/Δ mice compared with Asxl1^fl/fl littermates at 3 weeks of life.

(B) Serial body weight measurement of OsxCre;Asxl1^Δ/Δ mice and Asxl1^fl/fl littermates (n = 6 mice per genotype). Mice were weighed weekly on the same date and time.

(C) Distal femur BMD of 3-week-old Asxl1^fl/fl (n = 4 mice) and OsxCre;Asxl1^Δ/Δ (n = 6 mice).

(D and E) μCT analysis shows a significantly reduced bone volume (D) and trabecular bone (E) in OsxCre;Asxl1^Δ/Δ (n = 6 mice) compared with Asxl1^fl/fl controls (n = 4 mice). Scale bar represents 200 μm.

(F and G) Dynamic bone histomorphometry was performed using alizarin labeling. The mineral apposition rate (MAR, F) and bone formation rate (BFR/BS, G) are significantly decreased in OsxCre;Asxl1^Δ/Δ (n = 6 mice) versus controls (n = 4 mice). Scale bar represents 20 μm.

(H) Quantitation of percentage of PDGFRα⁺CD45⁻TER119⁻CD31⁻ BMSCs in the bone marrow of OsxCre;Asxl1^Δ/Δ (n = 5 mice) and littermate controls (n = 4 mice, 5 weeks old).

(I) The frequencies of CFU-F per femur from Asxl1^fl/fl (n = 5 mice) and OsxCre;Asxl1^Δ/Δ (n = 7 mice) are shown.

(J) The frequencies of CFU osteoblasts per femur are shown (top panel). Representative ALP staining of osteoblastic colonies cultured in osteogenic culture medium from OsxCre;Asxl1^Δ/Δ (n = 5 mice) and Asxl1^fl/fl (n = 3 mice) BMMNCs.

(K) Ratio of ALP⁺ osteoblasts to total colonies demonstrates impaired osteoblast differentiation in OsxCre;Asxl1^Δ/Δ (n = 5 mice) compared with littermate controls (n = 3 mice).

Data are presented as mean ± SEM. ^∗p < 0.05, ^∗∗p < 0.005, ^∗∗∗p < 0.001. See also Figures S2 and S3.