Fig. 7

Osteoclast-driven degradation of Fgfr3-Runx2^cKO synchondroses. Fgfr3-Runx2^cHet and Fgfr3-Runx2^cKO mice were injected with tamoxifen at P3 and lineage-traced to P42 (a) and 3 months (b). Synchondroses were stained with tartrate-resistant acid phosphatase (TRAP). Boxed regions show higher magnification. TRAP⁺ osteoclasts sparsely label the primary spongiosa at P42 and 3 months in Fgfr3-Runx2^cHet synchondroses (a, b left magnified panels, arrowheads). TRAP⁺ signal envelopes the entire fusion defect in the SOS of Fgfr3-Runx2^cKO animals (a, b right magnified panels, yellow dashed lines). Fgfr3-Runx2^cHet and Fgfr3-Runx2^cKO mice were injected with tamoxifen at P3 and lineage-traced to P42 (c) and 3 months (d). Synchondroses were stained with fluorescent TRAP (ELF97). Boxed regions show higher magnification. TRAP⁺ osteoclasts sparsely label the primary spongiosa at P42 and 3 months in Fgfr3-Runx2^cHet synchondroses (c, d left magnified panels, arrowheads). In the SOS of Fgfr3-Runx2^cKO mice, Col1a1(2.3 kb)-GFP⁺, Fgfr3^CE-tdT⁺, TRAP⁺ cells independently label the fusion defect (c, d right magnified panels, arrowheads). Red: Fgfr3^CE-tdT, green: Col1a1(2.3 kb)-GFP, purple: TRAP. Scale bar: 100 µm. Quantification of colorimetric TRAP⁺ osteoclasts (e) and % area TRAP⁺ signal (f) at P42 [Fgfr3-Runx2^cHet n = 3, Fgfr3-Runx2^cKO n = 6 (SOS)/n = 5 (ISS)] and 3 months [Fgfr3-Runx2^cHet n = 3, Fgfr3-Runx2^cKO n = 4 (SOS)/n = 5 (ISS)]. *P < 0.05, Mann-Whitney’s U-test. Data are presented as mean ± s.d. g Quantification of fluorescent TRAP⁺ osteoclasts at P42 [Fgfr3-Runx2^cHet n = 4, Fgfr3-Runx2^cKO n = 5 (SOS)/n = 4 (ISS)] and 3 months [Fgfr3-Runx2^cHet n = 4 (SOS)/n = 3 (ISS), Fgfr3-Runx2^cKO n = 4 (SOS)/n = 4 (ISS)]. *P < 0.05, Mann-Whitney’s U-test. Data are presented as mean ± s.d