Figure 4. (Panel A) Analysis of RT-PCR products with amelogenin exon 2 and exon 7-specific primer sets. PCR was carried out for each sample by 25 cycles. The amplified products were analyzed by 4.5% polyacrylamide gel electrophoresis. Lane M: molecular-size standard, x 174 HaeIII digested (New England Bio-Lab). Lane 1, secretory ameloblasts in the molar; lane 2, secretory ameloblasts in the incisor; lane 3, maturation ameloblast in the incisor; lane 4, odontoblasts in the molar; and lane 5, odontoblasts in the incisor. (Panel B) Amelogenin gene expression in erupted first molar odontoblasts. Lane 1: PCR with upstream primer at exon 5 and downstream primer at exon 6; lane 2, PCR with upstream primer at exon 2 and downstream primer at exon 7; and lane 3, PCR with GAPDH-specific primers.