Twist Regulates Cadherin-Mediated Differentiation and Fusion of Human Trophoblastic Cells

Abstract

The formation of the multinucleated syncytiotrophoblast of the human placenta by the terminal differentiation and fusion of mononucleate cytotrophoblasts is a critical step in pregnancy. Previous studies have demonstrated that this cellular event is dependent on a progressive decrease in the levels of the cell-adhesion molecule, E-cadherin. The aim of the study was to examine the role of Twist, a transcription factor identified as a key repressor of E-cadherin expression, in the differentiation of human trophoblastic cells. The expression of Twist or E-cadherin were first examined in first-trimester chorionic villi by immunohistochemistry. Gain- or loss-of-function studies on Twist were then performed in BeWo choriocarcinoma cells. The presence or absence of multinucleated syncytium was confirmed by indirect immunofluorescence using antibodies directed against Twist, E-cadherin, or desmoplakin, a cellular marker of mononucleate cytotrophoblasts. The formation of multinucleated syncytium was associated with increased Twist and a decreased E-cadherin expression. Similarly, exogenous expression of Twist resulted in a continuous and progressive decrease in E-cadherin expression and the subsequent formation of syncytium in BeWo cells maintained under normal culture conditions. In contrast, small interfering RNA specific for Twist inhibited 8-Br-cAMP (8-bromoadenosine 3',5'-cyclic monophosphate)-mediated differentiation and fusion of over time in culture. Twist is an upstream regulator of the E-cadherin-mediated terminal differentiation and fusion in a human trophoblastic cell line in vitro.