Fig. 4: The only live offspring of Col1a1fapKO genotype exhibits severe skeletal defects.

a Radiograph of three-week-old wild-type (WT, Fap-Cre-negative;Col1a1^loxP/loxP) and Col1a1^fapKO mice. b H&E staining of the forelimb whole-mount sections of 3-week-old WT (n = 3) and Col1a1^fapKO (n = 1, limited by the fact that only one live Col1a1^fapKO mouse was ever observed) mice. c H&E staining, Masson’s Trichrome staining (MTS), and Safranin-O/Fast Green staining on serial sections of the forelimbs from three-week-old WT (n = 3) and Col1a1^fapKO (n = 1, limited by the fact that only one live Col1a1^fapKO mouse was ever observed) mice. d Quantification of % positive area for MTS staining (blue indicating collagen deposition) and Safranin-O/Fast Green staining (red indicating cartilage) based on the staining shown in (c). Quantification of % positive area for staining was based on 10 bone samples from WT group (n = 3 mice) and Col1a1^fapKO group (n = 1 mouse, limited by the fact that only one live Col1a1^fapKO mouse was ever observed). The unpaired, two-tailed t test was used to compare the mean of two independent groups. *P = 0.0116, ***P = 1.11E-06. Data are represented as mean ± SEM. e Representative H&E and immunofluorescence images of humerus serial sections from Fap-Cre;LSL-tdTomato mice (n = 3 mice at 2-month-old) stained for osteoblast marker osteocalcin (green) and Fap-Cre-induced tdTomato (red). Scale bars, 50 μm. Scale bars of whole-mount sections, 5 mm; Scale bars at 50× magnification, 500 μm; Scale bars at 200× magnification, 100 μm.