Transforming growth factor‐β1 regulates expression of the matrix metalloproteinase 20 (Mmp20) gene through a mechanism involving the transcription factor,myocyte enhancer factor‐2C,in ameloblast lineage cells

Matrix metalloproteinase‐20 (Mmp20) plays an essential role in amelogenesis during tooth development and is regulated by transforming growth factor‐β1 (TGF‐β1) in mouse ameloblast lineage cells (ALCs). The objective of this study was to explore the role of myocyte enhancer factor‐2C (MEF2C), a key transcription factor in craniofacial development, in TGF‐β1‐induced Mmp20 gene expression. We investigated Mmp20 expression in ALCs over‐expressing MEF2C and in ALCs with MEF2C knocked down. We also analyzed activity of the Mmp20 promoter using a transient reporter gene‐expression assay in cultured ALCs. Putative transcription factor‐binding sites for MEF2C and TGF‐β1 on the Mmp20 promoter were analyzed with bioinformatics tools and examined using an electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP). The expression of Mmp20 was induced, in a dose‐dependent manner, by MEF2C over‐expression, and TGF‐β1‐induced Mmp20 expression was blocked by MEF2C knockdown in ALCs. There was a TGF‐β1/MEF2C‐responsive region, including a putative MEF2‐binding site, between base pairs ?356 and ?73 of the Mmp20 promoter. Mutation of the putative MEF2‐binding site significantly reduced Mmp20 promoter activity upon activation with MEF2C or TGF‐β1. In conclusion, TGF‐β1‐induced Mmp20 expression in ALCs was regulated through the MEF2‐binding site on the Mmp20 promoter and thus mediated by the MEF2C signaling pathway.