Fig. 1.

Siglec15 deficiency in macrophage-lineage cells leads to cell fusion failure and a decrease in bone volume. a Illustration of the preparation for Trap⁺ pOC and mOC differentiation. b Hierarchical clustering heatmap showing the expression of the mouse Siglec family in BMMs, pOCs, and mOCs detected and analyzed by RNA-seq. c Western blot analysis of Siglec15 in BMMs, pOCs and mOCs. d Representative μCT images of femurs from Siglec15^fl/fl and Siglec15^ΔLysM mice: 3D trabecular reconstruction (top) and 2D cross-sectional view (bottom). The bar represents 4 mm. e Quantitative μCT analysis of trabecular number (Tb.N), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), and cortical thickness (Ct.Th); n = 5. f TRAP staining of distal Siglec15^fl/fl and Siglec15^ΔLysM femur sections and quantification of the multinuclear osteoclast number; the bar represents 200 μm. TRAP staining with quantification of the osteoclast number per well (g) and relative TRAP activity (h) of BMMs isolated from Siglec15^fl/fl and Siglec15^ΔLysM mice. i Immunostaining of Siglec15^fl/fl (WT) and Siglec15^ΔLysM osteoclasts with phalloidin and anti-Siglec15; the average number of nuclei was quantified. j Bone resorption assay of Siglec15^fl/fl (WT) and Siglec15^ΔLysM osteoclasts quantified by pit area formation, n = 3. The bar represents 100 μm. Data represent the mean ± SD, and statistically significant differences are indicated as *P < 0.05; **P < 0.01; ***P < 0.001