Inhibition of the Zeb family prevents murine palatogenesis through regulation of apoptosis and the cell cycle

Mammalian palate separates the oral and nasal cavities for normal feeding, breathing and speech. The palatal shelves are a pair of maxillary prominences that consist of the neural crest-derived mesenchyme and surrounding epithelium. Palatogenesis is completed by the fusion of the midline epithelial seam (MES) after the medial edge epithelium (MEE) cells make contact between the palatal shelves. Various cellular and molecular events, such as apoptosis, cell proliferation, cell migration, and epithelial-mesenchymal transition (EMT), are involved in palatogenesis. The Zeb family of transcription factors is an essential player during normal embryonic development. The distinct role of the Zeb family has not been thoroughly elucidated to date. In mouse palate, the Zeb family factors are expressed in the palatal mesenchyme until MEE contact. Interestingly, the expression of the Zeb family has also been observed in MES, which is already fused with the mesenchymal region. The regulatory roles of the Zeb family in palatogenesis have not been elucidated to date. The purpose of this study is to determine the Zeb family effects on the cellular events. To investigate the functions of the Zeb family, siRNA targeting Zeb family was used to treat in vitro organ culture for temporary inhibition of the Zeb family during palatogenesis. In the cultured palate containing siRNA, MES was clearly observed, and E-cadherin, an epithelial marker, was still expressed. Inhibition of the Zeb family results in the suppression of apoptosis, increased cell proliferation, and defective cell migration in the developing palate. Our data suggest that the Zeb family plays multiple roles in the stimulation and inhibition of apoptosis and cell proliferation and efficient mesenchymal cell migration during palatogenesis.