Distribution of human endogenous retrovirus type W receptor in normal human villous placenta.
BACKGROUND
The fusion of trophoblast cells into the villous syncytiotrophoblast is crucial for appropriate placental function and fetal development. Fusion occurs following the interaction of syncytin-1, an envelope protein of the endogenous retrovirus HERV-W, and the RD114/mammalian type D retrovirus receptor (RDR/ASCT2) on adjacent cell membranes. This process must be tightly regulated in order to maintain the proliferative pool of cytotrophoblast cells as well as the function of the syncytia.


OBJECTIVE
We sought to investigate whether syncytial fusion of placental cytotrophoblast cells may be regulated via modulation of RDR/ASCT2 expression.


METHODS
Expression of RDR/ASCT2 in term and first trimester villous placenta was assessed along with a number of molecular markers using immunofluorescent staining. In a complementary approach, Western blotting was used to investigate RDR/ASCT2 expression in a panel of choriocarcinoma cell lines before and after stimulation of fusion.


RESULTS
Villous placental RDR/ASCT2 expression was found to be restricted to the cytotrophoblast compartment, being largely absent in the syncytiotrophoblast. Local variations in RDR/ASCT2 expression were not associated with the proliferative status of cytotrophoblast cells. RDR/ASCT2 expression was also shown to be down-regulated in BeWo choriocarcinoma cells after stimulation of syncytial fusion.


CONCLUSIONS
This first report of the localisation and distribution of RDR/ASCT2 in human placental villi suggests that the fusion of placental trophoblast cells is not regulated by local or temporal variations of RDR/ASCT2 expression in villous cytotrophoblast cells.
Gene and Stem Cell Therapy Program, Centenary Institute of Cancer Medicine and Cell Biology, University of Sydney, NSW, Australia.
M D
MD
Hayward
A J G
AJ
Pötgens
S
S
Drewlo
P
P
Kaufmann
J E J
JE
Rasko
D026962:Amino Acid Transport System ASC / Q000378:metabolism*; D045744:Cell Line, Tumor; D002822:Choriocarcinoma / Q000378:metabolism / Q000473:pathology; D002824:Chorionic Villi / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006801:Humans; D015778:Minor Histocompatibility Antigens; D010920:Placenta / Q000378:metabolism* / Q000473:pathology; D011247:Pregnancy; D014327:Trophoblasts / Q000378:metabolism / Q000473:pathology; D014594:Uterine Neoplasms / Q000378:metabolism / Q000473:pathology
D026962:Amino Acid Transport System ASC; D015778:Minor Histocompatibility Antigens; C420506:SLC1A5 protein, human