Fig. 7.

Model of jawbone regeneration. (A) During endochondral bone development, chondrocyte (blue) and osteocyte (red) lineages are largely distinct. By contrast, cells co-express chondrocyte and osteoblast gene programs during lower jawbone regeneration in adult zebrafish, with chondrocyte-like cells rapidly mineralizing and maturing into osteoblasts. (B) During bone homeostasis, periosteal cells (gray layer) self-renew and contribute to new osteoblasts (black). In response to jawbone resection, Ihha signaling induces the chondrogenic differentiation of periosteal cells, with these repair chondrocytes (blue) maturing into bone-producing cells.