Journal of Dental Research, Vol 75, 1735-1741, Copyright © 1996 by International & American Associations for Dental Research Online Journals

ARTICLES

Cloning, cDNA sequence, and alternative splicing of porcine amelogenin mRNAs

C. C. Hu, J. D. Bartlett, C. H. Zhang, Q. Qian, O. H. Ryu and J. P. Simmer
University of Texas School of Dentistry, Health Science Center at San Antonio, Department of Pediatric Dentistry 78284-7888, USA.

In mammals, the organic matrix of developing enamel is dominated by amelogenins. To investigate the expression of proteins secreted into the developing enamel matrix, we have constructed a porcine enamel organ epithelia-specific cDNA library. The amelogenin fraction of the cDNA library was characterized by the cloning of amelogenin-specific polymerase chain-reaction (PCR) amplification products, 5' and 3' rapid amplification of cDNA ends (RACE), and by helper phage rescue of unamplified clones. Clones were characterized that encode porcine amelogenin isoforms 173, 157, 56, 41, and 40 amino acids in length. The structure of the porcine amelogenin gene differs from that of any of those yet described. There are two homologous but distinct exons 1, 2, and 7. One of the two exon 7s can vary in length depending upon the selection of either of two polyadenylation signal/cleavage sites. As a rule, a given exon 1 always pairs with the same exon 2 but can be associated with either exon 7. Despite significant sequence divergence within these exons, no differences are observed in exons 3, 5, and 6. We interpret these findings as evidence of a single amelogenin gene expressed from two promoters; however, the results do not exclude the existence of a second amelogenin gene. The variability generated through the use of alternate promoters and exon 7s primarily affects the non-coding regions of the message. A given amelogenin isoform expressed from the two promoters displays four amino acid differences within the signal peptide, while the secreted proteins are identical. Similarly, the alternative use of exon 7 does not alter the structure of the protein products. The pattern of RNA splicing of amelogenin pre-mRNAs is different for the transcripts expressed from the two promoters. The 173- and the 56-residue amelogenins can be expressed from either promoter, while the 157-residue amelogenin is generated by only one of the two promoters.

This article has been cited by other articles:

				K. Tanimoto, T. Le, L. Zhu, H.E. Witkowska, S. Robinson, S. Hall, P. Hwang, P. DenBesten, and W. Li Reduced Amelogenin-MMP20 Interactions in Amelogenesis Imperfecta J. Dent. Res., May 1, 2008; 87(5): 451 - 455. [Abstract] [Full Text] [PDF]

				R. Lakshminarayanan, D. Fan, C. Du, and J. Moradian-Oldak The Role of Secondary Structure in the Entropically Driven Amelogenin Self-Assembly Biophys. J., November 15, 2007; 93(10): 3664 - 3674. [Abstract] [Full Text] [PDF]

				S. Delgado, M. Ishiyama, and J.-Y. Sire Validation of Amelogenesis Imperfecta Inferred from Amelogenin Evolution J. Dent. Res., April 1, 2007; 86(4): 326 - 330. [Abstract] [Full Text] [PDF]

				L. Xu, H. Harada, and A. Taniguchi The Exon 6ABC Region of Amelogenin mRNA Contribute to Increased Levels of Amelogenin mRNA through Amelogenin Protein-enhanced mRNA Stabilization J. Biol. Chem., October 27, 2006; 281(43): 32439 - 32444. [Abstract] [Full Text] [PDF]

				L. Xu, H. Harada, T. Yokohama-Tamaki, S. Matsumoto, J. Tanaka, and A. Taniguchi Reuptake of Extracellular Amelogenin by Dental Epithelial Cells Results in Increased Levels of Amelogenin mRNA through Enhanced mRNA Stabilization J. Biol. Chem., January 27, 2006; 281(4): 2257 - 2262. [Abstract] [Full Text] [PDF]

				T. Ikawa, A. Kakegawa, T. Nagano, H. Ando, Y. Yamakoshi, T. Tanabe, J.P. Simmer, C.-C. Hu, M. Fukae, and S. Oida Porcine Amelogenin is Expressed from the X and Y Chromosomes J. Dent. Res., February 1, 2005; 84(2): 144 - 148. [Abstract] [Full Text] [PDF]

				E. Venezia, M. Goldstein, B.D. Boyan, and Z. Schwartz THE USE OF ENAMEL MATRIX DERIVATIVE IN THE TREATMENT OF PERIODONTAL DEFECTS: A LITERATURE REVIEW AND META-ANALYSIS Crit. Rev. Oral. Biol. Med., November 1, 2004; 15(6): 382 - 402. [Abstract] [Full Text] [PDF]

				L. Wang and J. Moradian-Oldak Assessment of Enamelysin (MMP-20) Selectivity to Three Peptide Bonds on Amelogenin Sequence J. Dent. Res., October 1, 2002; 81(10): 664 - 667. [Abstract] [Full Text] [PDF]

				T. Iwata, Y. Morotome, T. Tanabe, M. Fukae, I. Ishikawa, and S. Oida Noggin Blocks Osteoinductive Activity of Porcine Enamel Extracts J. Dent. Res., June 1, 2002; 81(6): 387 - 391. [Abstract] [Full Text] [PDF]

				S. Oida, T. Nagano, Y. Yamakoshi, H. Ando, M. Yamada, and M. Fukae Amelogenin Gene Expression in Porcine Odontoblasts J. Dent. Res., February 1, 2002; 81(2): 103 - 108. [Abstract] [Full Text] [PDF]

				M. Iwase, Y. Satta, and N. Takahata Sex-Chromosomal Differentiation and Amelogenin Genes in Mammals Mol. Biol. Evol., August 1, 2001; 18(8): 1601 - 1603. [Full Text] [PDF]

				S. Toyosawa, C. O'hUigin, F. Figueroa, H. Tichy, and J. Klein Identification and characterization of amelogenin genes in monotremes, reptiles, and amphibians PNAS, October 27, 1998; 95(22): 13056 - 13061. [Abstract] [Full Text] [PDF]

				C. W. Gibson, Z.-A. Yuan, B. Hall, G. Longenecker, E. Chen, T. Thyagarajan, T. Sreenath, J. T. Wright, S. Decker, R. Piddington, et al. Amelogenin-deficient Mice Display an Amelogenesis Imperfecta Phenotype J. Biol. Chem., August 17, 2001; 276(34): 31871 - 31875. [Abstract] [Full Text] [PDF]