Down ?Regulation of StarD7 by RNA interferente modulates biochemical differentiation and fusion of human choriocarcinama JEG-3 cells

SEBASTIAN MARQUEZ; GRACIELA PANZETTA -DUTARI; VIVIANA RENA; MÁRQUEZ SEBASTIAN; SUSANA GENTI DE RAIMONDI; JESICA FLORES- MARTÍN

iguazu Misiones

Simposio; International Symposium ?Gene Expression and RNA Processing; 2011

International Centre of Genetic Engineering and Biotechnology and Facultad de Ciencias Exactas y Naturales, Univ. de Buenos Aires. Agencia Nac. de Promoción Científica y Tecnológica

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. It has been previously documented that StarD7 has a wide-spread mRNA expression in trophoblastic tissues whit 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(SF-1), β-catenin and that the T cell-specific transcription factor 4 (TCF4) binding site plays an important role, through Wnt/ß-catenin signaling. 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 Gap junction protein 43kDa (Cnx43), Methyl-CpG binding domain protein 2 (MBD2) and ATP-binding cassette sub-family G (ABCG2) mRNA levels, all of them associated with Wnt signalling measured by qRT-PCR and a diminution of phospholipid synthesis from labelled glycerol. In contrast, expression of syncytial formation markers, such as β-hCG protein production and secretion, as well as β-hCG, GCMa and Syncytin 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. Altogether these findings suggest that StarD7 plays a role in trophoblast cell differentiation events through transport and uptake of lipids.