Alternative Splicing of Amelogenin mRNA from Rat Incisor Ameloblasts

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Abstract
Amelogenin proteins are a major component of the developing enamel matrix, and are likely to have a key role in the control of enamel biomineralization. The heterogeneity of amelogenin is in part due to alternative splicing of the amelogenin RNA transcripts. Several patterns of alternative splicing have been described in mouse, bovine, porcine, and human enamel, with all alternatively spliced products having homologous 5' and 3' sequences within the coding regions. In these studies, we have used anchored PCR to identify alternatively spliced amelogenin cDNA sequences in the rat. We found amelogenin cDNAs that could be divided into two groups based on their 3' sequence. Group 1 cDNAs had a novel terminal sequence that has not been previously identified, while group 2 cDNAs were similar to those previously identified in other animal species. We identified a sequence, identical to the novel 3' amelogenin 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 novel group 1 proteins having a more basic isoelectric poi