title: Role of HERV-W syncytin-1 in placentation and maintenance of human pregnancy.
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.
authors.affiliation: South Carolina Center for Biotechnology, Claflin University, Orangeburg, SC 29115, USA.
authors.forename: Samina
authors.initials: S
authors.lastname: Noorali
authors.forename: Ioana C
authors.initials: IC
authors.lastname: Rotar
authors.forename: Cindi
authors.initials: C
authors.lastname: Lewis
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Pestaner
authors.forename: Donald Gene
authors.initials: DG
authors.lastname: Pace
authors.forename: Antonio
authors.initials: A
authors.lastname: Sison
authors.forename: Omar
authors.initials: O
authors.lastname: Bagasra
mesh_terms: D000328:Adult; D002460:Cell Line; D020077:Endogenous Retroviruses / Q000502:physiology*; D005260:Female; D015686:Gene Products, env / Q000096:biosynthesis*; D015894:Genome, Human / Q000502:physiology*; D006801:Humans; D010929:Placentation / Q000502:physiology*; D011247:Pregnancy / Q000378:metabolism*; D011257:Pregnancy Proteins / Q000096:biosynthesis*; D011374:Progesterone / Q000378:metabolism; D014327:Trophoblasts / Q000166:cytology / Q000378:metabolism
chemical_list: C518353:ERVFRD-1 protein, human; D015686:Gene Products, env; D011257:Pregnancy Proteins; C405335:syncytin; D011374:Progesterone