title: Origin, splicing, and expression of rodent amelogenin exon 8.
abstract: Amelogenin RNA transcripts undergo extensive alternative splicing, and MMP-20 processes the isoforms following their secretion. Since amelogenins have been ascribed cell-signaling activities, we asked if a lack of proteolytic processing by MMP-20 affects amelogenin signaling and consequently alters amelogenin splice site selection. RT-PCR analyses of amelogenin mRNA between control and Mmp20(-/-)mice revealed no differences in the splicing pattern. We characterized 3 previously unidentified amelogenin alternatively spliced transcripts and demonstrated that exon-8-encoded amelogenin isoforms are processed by MMP-20. Transcripts with exon 8 were expressed approximately five-fold less than those with exon 7. Analyses of the mouse and rat amelogenin gene structures confirmed that exon 8 arose in a duplication of exons 4 through 5, with translocation of the copy downstream of exon 7. No downstream genomic sequences homologous to exons 4-5 were present in the bovine or human amelogenin genes, suggesting that this translocation occurred only in rodents.
authors.affiliation: Department of Cytokine Biology, Harvard School of Dental Medicine, Boston, MA 02115, USA. jbartlett@forsyth.org
authors.forename: J D
authors.initials: JD
authors.lastname: Bartlett
authors.forename: R L
authors.initials: RL
authors.lastname: Ball
authors.forename: T
authors.initials: T
authors.lastname: Kawai
authors.forename: C E
authors.initials: CE
authors.lastname: Tye
authors.forename: M
authors.initials: M
authors.lastname: Tsuchiya
authors.forename: J P
authors.initials: JP
authors.lastname: Simmer
mesh_terms: D017398:Alternative Splicing / Q000235:genetics / Q000502:physiology*; D053523:Amelogenin / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D003743:Dental Enamel / Q000201:enzymology / Q000378:metabolism; D005091:Exons / Q000502:physiology; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D053519:Matrix Metalloproteinase 20 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008963:Molar / Q000201:enzymology / Q000378:metabolism; D008969:Molecular Sequence Data; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics
chemical_list: D053523:Amelogenin; D047908:Intracellular Signaling Peptides and Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D053519:Matrix Metalloproteinase 20