Down-Regulation of StarD7 by RNA interference modulates biochemical differentiation and fusion of human choriocarcinoma JEG-3 cells

FLORES MARTIN J; RENA VC; MÁRQUEZ S; PANZETTA DUTARI G; GENTI RAIMONDI S

Iguazú, Misiones

Simposio; Symposium "Gene Expression and RNA Processing“; 2011

ICGEB-ANPCYT-CONICET

StarD7 gene encodes a protein that belongs to the family of StaR-related lipid transfer proteins, which are implicated in intracellular lipid transport, metabolism, and signaling. It has been previously documented that StarD7 has a wide-spread mRNA expression in trophoblastic tissues with highest levels in choriocarcinoma JEG-3 cells. StarD7 is partially relocated from the cytoplasm to the plasma membrane during in vitro cytotrophoblast differentiation into syncytiotrophoblast. Furthermore, we have shown that StarD7 promoter is synergistically activated by the Steroidogenic factor 1 and β-catenin and that the TCF4 binding site plays an important role through Wnt/ß-catenin signaling. Herein, StarD7 expression was down-regulated by siRNA to explore its function in JEG-3 cells. Silencing of StarD7 expression, confirmed by qRT-PCR and western blot, led to a marked decrease of in Cnx43, MBD2 and ABCG2 mRNA levels, all of them associated with Wnt signaling. In addition a diminution of phospholipid synthesis was observed. In contrast, expression of syncytial formation markers, such as β-hCG protein production and secretion, as well as the mRNA levels of β-hCG, GCMa and syncytin were increased. What is more, fluorescent microscopy performed by immunostaining for desmoplakin suggested that there was a reduction of intercellular desmosomes between adjacent JEG-3 cells after knocking-down StarD7 expression. Altogether these findings suggest that StarD7 plays a role in trophoblast cell differentiation events through transport and uptake of lipids.