DIFFERENTIAL EXPRESSION OF LAMININ ALPHA-CHAINS DURING MURINE TOOTH DEVELOPMENT

Basement membranes of the developing tooth have been previously shown to contain laminins, but the nature of the laminins have not been desc ribed, We here studied the distribution of five different laminin alph a chains during tooth development, We show that both epithelial and me senchymal cells produce laminin alpha chains, The mRNAs of three lamin in alpha chains, alpha 1, alpha 2, and alpha 4, were expressed in the tooth mesenchyme, whereas two, the alpha 3 and alpha 5 chain mRNAs, we re found in epithelium. Drastic changes in the expression patterns of the two epithelial chains were found during development, The alpha 5 m RNA was widely expressed in tooth epithelia, and the corresponding pro tein was evenly distributed along the tooth basement membrane througho ut embryonic development, This suggests a role for alpha 5 as a major laminin alpha chain in tooth basement membrane during embryonic stages , The subsequent disappearance of alpha 5 and the drastic increase in alpha 3A mRNA expression during terminal ameloblast differentiation an d enamel secretion suggest that alpha 3A acts as an important chain in the enamel matrix after degradation of tooth basement membrane. These studies show that laminin networks in tooth epithelia form as a resul t of epithelial-mesenchymal interactions and that the molecular compos ition of the laminin networks varies drastically during development of tooth. (C) 1997 Wiley-Liss, Inc.