Down-regulation of StarD7 by RNA interference increases b-hCG production and secretion in JEG-3 cells

FLORES MARTIN J; RENA VC; RIDANO, M.E; PANZETTA DUTARI G; GENTI RAIMONDI S

Santiago de Chile

Congreso; IFPA (Internacional Federation of Placenta Associations) Meeting 2010; 2010

IFPA (Internacional Federation of Placenta Associations)

StarD7 gene encodes a protein that belongs to the family of StaR-related lipid transfer (START) proteins, which are implicated in intracellular lipid transport, metabolism, and signaling. StarD7 shares a conserved central region with a START domain, it consists of a 210-amino acid globular domain with an internal hydrophobic cavity for lipid binding. It has been previously documented that StarD7 has a wide-spread mRNA expression in trophoblastic tissues and several tumour cell lines whit highest levels in choriocarcinoma JEG-3 cells. We have recently reported that StarD7 is partially relocated from the cytoplasm to the plasma membrane during in vitro cytotrophoblast differentiation into syncytiotrophoblast. Suggesting that it may play a functional role in this process through phospholipids uptake and transport. Furthermore, we have shown that ß-catenin activates human StarD7 expression through Wnt/ß-catenin signaling. Several reports emphasize the role of Wnt/ß-catenin signaling in blastocyt competence, implantation, and normal placental development as well as in gestational diseases. Herein, to explore its function in JEG-3 cells StarD7 expression was down-regulated by siRNA. Silencing of StarD7 expression, confirmed by qRT-PCR and western blot, led to a marked decrease of Cnx43, iNOS, MBD2, ABCG2 and TGFbRII mRNA levels, all of them associated with Wnt signalling. In contrast, expression of syncytial formation markers, such as β-hCG protein production and secretion, as well as β-hCG mRNA levels, was increased by StarD7 siRNA. In addition, 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. Whether this response is unique to this cell line is being currently investigating using other models such as BeWo and primary trophoblast cells. These findings indicate that the inhibition of StarD7 transcript level alters the expression of several critical genes suggesting that it may play a role in placental development. Supported by CONICET, FONCy, MinCyT of Córdoba and SECyT-UNC