Model for osteoblast maturation in the fin ray. Early (runx2a, runx2b, osx), intermediate (spp-1), and mature (ZNS5) osteoblast domains are represented on the left. These genes are expressed in partially overlapping domains in the lateral osteoblast compartment (between the basal layer of the epidermis,e, and the actintrichia, yellow). The region of cx43-positive cells is indicated in purple in the cartoon of the fin ray. We suggest that the cx43-positive proliferating cells cross actinotrichia and contribute to the cells in zone 1.