Figure 2. Perichondrium-targeted conditional Ext1-KO mice develop multiple osteochondromas.

(A) X-ray images of 4-week-old Fsp1-Ext1^CKO and control littermates (Ext1^flox/flox; WT). Fsp1-Ext1^CKO mice show bony protrusions in long bones, vertebrae, and rib bones (arrows). (B) Whole-mount skeletal preparations of Fsp1-Ext1^CKO and control littermates (Ext1^flox/flox; WT) at 2, 4, and 12 weeks of age. (C) Safranin O/Fast Green–stained sections through bony tumors in the femur, tibia, and vertebrae of Fsp1-Ext1^CKO mice (arrowheads). These tumors have a tissue structure consistent with osteochondroma (right panels). Scale bars: 0.05 mm. Data shown are representative images; each analysis was performed on at least 3 animals per genotype.