Characterization of amelogenin mRNA from secretory- and maturation-stage rat incisor enamel.

Amelogenins are extracellular matrix proteins expressed at the secretory and the maturation stages of enamel formation. To characterize amelogenin transcripts from these two stages, rat incisor enamel-organ mRNA was hybridized to a mouse amelogenin cDNA. Northern analysis of the mRNA showed four amelogenin transcripts at the secretory stage. Two of these were larger than previously described, and would code for high molecular-weight amelogenins (> 40 kDa). These transcripts were similar in size to at least three bovine amelogenin mRNAs. At the maturation stage, one transcript slightly smaller than the major amelogenin transcript from the secretory stage was apparent. These differences may indicate a selective splicing of amelogenin mRNA in the maturation stage as compared to the secretory stage of enamel development.