Temporal Regulation of the Expression of Syncytin (HERV-W), Maternally Imprinted PEG10, and SGCE in Human Placenta1

Abstract

Maternally imprinted PEG10 and SGCE, separated by approximately 2.15 Mb from Syncytin (HERV-W) gene at 7q21.3, are implicated in choriocarcinoma and Silver-Russell syndrome. Here we have analyzed the temporal regulation of mRNA expression of these genes in placenta and demonstrate that Syncytin gene activation is highest in term placenta, PEG10, downregulated at early hypoxic phase, and highly activated at 11-12 wk of gestation. In contrast, transcription from SGCE remained unchanged throughout pregnancy, suggesting two neighboring imprinted genes are differentially regulated at very early pregnancy. Additionally, accumulation of two major species of mRNA (8 kb and 3.1 kb) encoded by HERV-W in placenta is regulated: 3.1 kb mRNA level remained unchanged throughout pregnancy, whereas the production of 8 kb species was highest in term placenta. Western blot and immunohistochemical staining of placental tissues with monoclonal antibodies revealed a marked reduction of syncytin glycoprotein synthesis in late pregnancy. Therefore, the relative levels of 3.1 kb and 8 kb mRNAs in trophoblasts could regulate syncytin protein synthesis, possibly by competition of the two mRNA species for translational apparatus.

Microarray-based Identification of Individual HERV Loci Expression: Application to Biomarker Discovery in Prostate Cancer

“…Over the last 10 years, most of the attempts for HERV expression measurement have used RT-PCR techniques either to focus on a specific locus [20][21][22][23][24] or based on the relative conservation of the pol genes to evaluate general trends within HERV genera 25,26 . Additionally, PCR amplifications using highly degenerated primers coupled with low density microarrays intended to detect and quantify the expression of HERV families 27,28 .…”

Developmental cell biology of human villous trophoblast: current research problems

“…These include ADAM12 and the endogenous retroviral envelope proteins syncytin 1 and 2 (Huppertz et al, 2006a). Syncytin 2 is in villous cytotrophoblast (Kudaka et al, 2008;Malassine et al, 2007) while syncytin 1 is regulated by GCM-1 (Lin et al, 2005) and probably arises in intermediate cytotrophoblasts in advance of fusion, as well as being expressed in the syncytium (Huppertz et al, 2006a;Mi et al, 2000;Smallwood et al, 2003). Ultrastructural observations have implicated lysosomal enzymes in fusion (Contractor et al, 1977).…”

Syncytins expression in cultured trophoblast cells according to differentiation status

“…Syncytin 1 is thought to be expressed mainly in the syncytiotrophoblast layer of villous trophoblasts [4][5][6] while others report that syncytin 1 is also expressed in the extravillous trophoblast, all along its differentiation pathway: cytotrophoblastic cells of the column, interstitial extravillous trophoblast (EVCT), multinucleated giant cells, and endovascular trophoblast [7]. On the other hand, syncytin 2 expression was found in villous cytotrophoblasts, but not in extravillous trophoblast.…”