Expression and localization of StarD7 in trophoblast cells

S ANGELETTI; R NORES; V RENA; R FRETES; G PANZETTA-DUTARI; S GENTI-RAIMONDI

Woods Hole, Massachusetts

Simposio; Twelfth Annual "Frontiers in Reproduction" Symposium; 2009

Marine Biological Laboratory

The StAR-related lipid transfer (START) domain is defined as a motif of around 200 amino acids implicated in lipid/sterol binding. In a previous study, we identified the StarD7 transcript encoding one of the 15 family members with START domain present in the human genome. This transcript was found to be over-expressed in choriocarcinoma JEG-3 cell line. In addition, we demonstrated that the recombinant StarD7 protein forms stable Gibbs and Langmuir monolayers at the air-buffer interface, showing marked surface activity and interaction with phospholipid monolayers, mainly with phosphatidylserine, cholesterol and phosphatidylglycerol. Objectives: This study was undertaken to evaluate the expression and localization of StarD7 protein in trophoblastic samples. Methods: Western blot, immunohistochemical and immunofluorescence assays were performed with two different antibodies obtained against over-expressed StarD7 and StarD7-C-terminal amino acids. Furthermore, StarD7 transcript levels were determined by quantitative real time PCR. Results: Here, we show for the first time the presence of StarD7 protein in human trophoblast cells. Western blot assays revealed a unique specific 34 kDa protein in JEG-3 cell line, choriocarcinoma tissue, complete hydatidiform mole, early and normal term placenta. Immunohistochemical data from early placentas showed that this protein is abundant in the syncytiotrophoblasts, mainly at the apical side of the syncytium, with a weak and focal reaction in the cytotrophoblast cells, whereas in normal term placentas the protein is homogeneously distributed in the cytoplasm of the syncytiotrophoblasts. Furthermore, an increased StarD7 mRNA and protein expression, as well as a change in its sub-cellular localization was observed in in vitro differentiating cytotrophoblast isolated from normal term placenta. Conclusions: Our findings suggest that StarD7 may play a functional role in the process of trophoblast differentiation, may be through phospholipids uptake and transport.