MiR-200b is involved in Tgf-beta signaling to regulate mammalian palate development

Various cellular and molecular events are involved in palatogenesis, including apoptosis, epithelialmesenchymal transition (EMT), cell proliferation, and cell migration. Smad2 and Snail, which are well-known key mediators of the transforming growth factor beta (Tgf-beta) pathway, play a crucial role in the regulation of palate development. Regulatory effects of microRNA 200b (miR-200b) on Smad2 and Snail in palatogenesis have not yet been elucidated. The aim of this study is to determine the relationship between palate development regulators miR-200b and Tgf-beta-mediated genes. Expression of miR-200b, E-cadherin, Smad2, and Snail was detected in the mesenchyme of the mouse palate, while miR-200b was expressed in the medial edge epithelium (MEE) and palatal mesenchyme. After the contact of palatal shelves, miR-200b was no longer expressed in the mesenchyme around the fusion region. The binding activity of miR-200b to both Smad2 and Snail was examined using a luciferase assay. MiR-200b directly targeted Smad2 and Snail at both cellular and molecular levels. The function of miR-200b was determined by overexpression via a lentiviral vector in the palatal shelves. Ectopic expression of miR-200b resulted in suppression of these Tgf-beta-mediated regulators and changes of apoptosis and cell proliferation in the palatal fusion region. These results suggest that miR-200b plays a crucial role in regulating the Smad2, Snail, and in apoptosis during palatogenesis by acting as a direct non-coding, influencing factor. Furthermore, the molecular interactions between miR-200b and Tgf-beta signaling are important for proper palatogenesis and especially for palate fusion. Elucidating the mechanism of palatogenesis may aid the design of effective gene-based therapies for the treatment of congenital cleft palate.