ALTERNATIVE SPLICING OF AMELOGENIN MESSENGER-RNA FROM RAT INCISOR AMELOBLASTS

Amelogenin proteins are a major component of the developing enamel mat rix, and are likely to have a key role in the control of enamel biomin eralization. The heterogeneity of amelogenin is in part due to alterna tive splicing of the amelogenin RNA transcripts. Several patterns of a lternative splicing have been described in mouse, bovine, porcine, and human enamel, with all alternatively spliced products having homologo us 5' and 3' sequences within the coding regions. In these studies, we have used anchored PCR to identify alternatively spliced amelogenin c DNA sequences in the rat. We found amelogenin cDNAs that could be divi ded into two groups based on their 3' sequence. Group 1 cDNAs had a no vel terminal sequence that has not been previously identified, while g roup 2 cDNAs were similar to those previously identified in other anim al species. We identified a sequence, identical to the novel 3' amelog enin cDNA sequence, in rat genomic DNA downstream from the previously identified exon 7. The putative amelogenin proteins predicted for the two groups differed in their predicted isoelectric points, with the no vel group 1 proteins having a more basic isoelectric point.