Integrin regulatory switching in development: oscillation of beta 5 integrin mRNA expression during epithelial-mesenchymal interactions in tooth development.

Integrin receptors for extracellular matrix molecules are thought to play important roles in morphogenesis since they mediate aspects of embryonic cell adhesion and migration. Using in situ hybridization, the mRNA expression pattern of the beta 5 integrin receptor subunit was examined during murine tooth development, a classical system for studying morphogenesis. In developing tooth, high-level expression of beta 5 integrin mRNA alternates from epithelium to mesenchyme and back to epithelium. Each switch in localization occurs within one day. These results demonstrate that an integrin mRNA can be precisely and rapidly up- and down-regulated over unexpectedly short time spans, and that expression can oscillate between adjacent, interacting epithelial and mesenchymal tissues during morphogenesis. This rapid modulation of mRNA expression suggests a potential regulatory role for the beta 5 integrin receptor in morphogenesis.