Fig. 4. Histological analysis of the calvarial sutures in Fgfr2^+/S252W mice. (A,C,E,G,I,K) Control littermates; (B,D,F,H,J,L) corresponding regions in mutant mice. (A-F) HE staining shows the development of the sagittal suture from E16.5 to P1. (A,B) No obvious difference of the sagittal sutures between the mutant and control at E16.5. (C,D) More proximate osteogenic fronts are evident at the mutant sagittal suture at E18.5. (E,F) Osteoid deposition is seen across the mutant sagittal suture at P1. (G-L) HE staining shows: a wide gap between the osteogenic fronts at the mutant interfrontal suture at P1 (G,H); presynostosis/synostosis with osteoid deposition at the mutant coronal suture at P1 (I,J); and presynostosis/synostosis at the mutant lambdoid suture at P1 (K,L). Arrows, osteogenic fronts; arrowheads, presynostosis/synostosis with osteoid formation; s, skin; p, parietal bone; b, brain; f, frontal bone; ip, interparietal bone. Scale bars: A-H,K,L, 50 µm; I,J, 25 µm.