Downregulated miR-29a/b/c during Contact Inhibition Stage Promote 3T3-L1 Adipogenesis by Targeting DNMT3A.

Differentiation of 3T3-L1 cells into adipocytes involves a highly-orchestrated series of events including contact inhibition (CI), clonal expansion, growth arrest, and terminal differentiation. Recent study demonstrated that 3T3-L1 preadipocytes will not be differentiated into mature adipocytes without CI stage, which indicated that CI stage plays an important role during 3T3-L1 adipogenesis. However, the molecular mechanism is not yet fully understood. In the present study, we found that the expression level of miR-29a/b/c was decreased and the expression of DNMT3A was up-regulated during CI stage, respectively. Furthermore, overexpression of miR-29a/b/c during CI stage inhibits adipogenesis significantly but not at other stages. In addition, miR-29a/b/c repressed DNMT3A expression by directly targeting its 3' untranslated region (3' UTR). Our data reveal a novel mechanism of miR-29a/b/c in the regulation of adipogenesis.