IRF6 is the mediator of TGFβ3 during regulation of the epithelial mesenchymal transition and palatal fusion

Mutation in interferon regulatory factor 6 (IRF6) is known to cause syndromic and non-syndromic cleft lip/palate in human. In this study, we investigated the molecular mechanisms related to IRF6 during palatal fusion using palatal shelves organ culture. The results showed that ablation of Irf6 resulted in a delay in TGF beta 3-regulated palatal fusion. Ectopic expression of IRF6 was able to promote palatal fusion and rescue shTgf beta 3-induced fusion defect. These findings indicate that IRF6 is involved in TGF beta 3-mediated palatal fusion. Molecular analysis revealed that ectopic expression of IRF6 increased the expression of SNAI2, an epithelial mesenchymal transition (EMT) regulator, and diminished the expression of various epithelial markers, such as E-cadherin, Plakophilin and ZO-1. In addition, knockdown of Irf6 expression decreased SNAI2 expression, and restored the expression of ZO-1 and Plakophilin that were diminished by TGF beta 3. Blocking of Snai2 expression delayed palatal fusion and abolished the IRF6 rescuing effect associated with shTgf beta 3-induced fusion defect. These findings indicate that TGF beta 3 increases IRF6 expression and subsequently regulates SNAI2 expression, and IRF6 appears to regulate EMT during palatal fusion via SNAI2. Taken together, this study demonstrates that IRF6 is a mediator of TGF beta 3, which regulates EMT and fusion process during the embryonic palate development.