Fig. 5. TUNEL staining of osteoblastic cells undergoing apoptosis in the post-frontal suture of calvaria. Cross sections of calvarial bone at the post-frontal suture (PF) were stained with TUNEL to visualize the apoptotic cells (A) or with Toluidine Blue (B). Wild type (WT) and Stat1^-/- calvarial sutures show no signs of apoptosis (A), while TgFGF and TgFGF/Stat1^-/- show numerous apoptotic cells around the PF suture and osteogenic front (indicated by arrows in B). The osteogenic front is more advanced in WT and Stat1^-/- mice (B), while in TgFGF and TgFGF/Stat1^-/- the fronts remain far apart from each other.