Role of HERV-W syncytin-1 in placentation and maintenance of human pregnancy.
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Noorali S, Rotar IC, Lewis C, Pestaner JP, Pace DG, Sison A, Bagasra O
Role of HERV-W syncytin-1 in placentation and maintenance of human pregnancy.
Appl Immunohistochem Mol Morphol. 2009 Jul;17(4):319-28. doi: 10.1097/PAI.0b013e31819640f9.
- PubMed ID
- 19407656 [ View in PubMed]
- Abstract
Over half of human genome contains retroelements, including retrotransposons, retroviruses, and other elements. Human endogenous retroviruses (HERVs) comprise about 8% of human genome. The products of 2 of 16 identified genes of HERV-W seem to play a pivotal role in the placentation. These 2 genes are HERV-W env glycoprotein (syncytin-1) and HERV-FRD env glycoprotein (syncytin-2). It has been shown previously that syncytin-1 mediates cell-cell fusions of cytotrophoblasts into syncytiotrophoblasts. In addition, HERV-W env contains an immunosuppressive region that may prevent rejection of a semiallogenic fetus from the mother's immune system. We analyzed 40 full-term placental tissues to localize the expression of syncytin-1-ISR by immunohistochemical staining and by reverse trancscriptase (RT) in situ polymerase chain reaction (PCR). Both the immunostaining and in situ RT-PCR showed strong expression of syncytin-1 in the syncytiotrophoblast layer from the full-term placental tissues. To further analyze the mechanism of early embryo HERV-W env activation, we utilized a HTR-8/SVneo cell line developed from first trimester human trophoblasts and subjected them to various physiologic concentrations of maternal hormones. Quantitative RT-PCR analyses demonstrated that exposure to progesterone significantly upregulated the HERV-W env expression, whereas several other hormones apparently played lesser roles. In conclusion, our findings suggest that expression of syncytin-1 (HERV-W env) in utero is expressed exclusively in the syncytiotrophoblast layer and is upregulated by progesterone.