IDENTIFICATION OF 2 ADDITIONAL EXONS AT THE 3' END OF THE AMELOGENIN GENE

Alternative splicing of the amelogenin gene generates a family of prot eins secreted by ameloblasts that are primarily responsible for tooth enamel formation. Here the presence of two additional exons, downstrea m of exon 7, which are followed by an alternate polyadenylation site, is reported. Long polymerase chain reaction was used with a rat genomi c amelogenin template to amplify sequences downstream from the primary polyadenylation sire. Within the amplified sequences, two exons of 45 bp (exon 8) and 110 bp (exon 9) were identified. The presence of thes e additional exons in the human and mouse genome was indicated by Sout hern blot analysis. Antibodies raised against a synthetic peptide corr esponding to a sequence encoded by exon 9 positively stained ameloblas ts in sections of developing murine and porcine unerupted teeth. These results suggest that an amelogenin protein(s) that includes sequences derived from exons 8 and 9 is synthesized by the ameloblasts. (C) 199 8 Elsevier Science Ltd. Ail rights reserved.