Expression profile of microRNA during tooth germ development

Objectives: MicroRNAs (miRNAs) are a class of short noncoding RNAs molecules that post-transcriptionally regulate gene expression in plants and animals. Since their discovery as regulators of developmental timing in Caenorhabditis elegans, hundreds of miRNAs have been identified. However, expression of miRNA in tooth has never reported. To investigate the expression profile of miRNA in tooth development, we perform miRNA array analysis.

Methods: The microRNA was isolated from embryonic day 16 (E16), postonatal day 1 (P1) and P3 mouse molar tooth germ by acid-phenol method. Isolated microRNA labeled with fluorescence, and then performed Genopal DNA microarray analysis.

Results: Expression of 200 microRNAs in tooth germ development was analyzed by microarray method. Fifteen microRNAs were down-regulated in P3 molar compared with E16, however, only two microRNAs were up-regulated. Expression of mmu-miR-18, 124a, 127, and 301 were gradually decreased between E16 and P3. Expression of mmu-miR-1, 15b, 19a, 20b, 31, 93, 106b, 125a, 130b, 133a, and 296 were decrease between P1 and P3. Gja1 is one of the gap junctional proteins that specifically express in secretary ameloblast and odontoblast, but not early stage of tooth germ. Target miRNAs for Gja1 predicted by Sanger Institute miRBase were mmu-miR-1, 101a, 101b, 199a-3p, 200a, 338-3p, 376a, and 434-3p. Among of those miRNA, expression of mmu-miR-1, 101a, 376a, and 434-3 in P3 molars were decreased compared with E16. On the other hand, rests of them were not changed during tooth development indicating that down-regulated miRNA may be important for the expression of Gja1 during tooth development.

Conclusion: Our results indicate that profile of miRNA expression may be useful for undetstanding the regulation of tooth specific gene expression.