Expression of an Endogenous Retrovirus (ERV3 HERV-R) in Human Reproductive and Embryonic Tissues—Evidence for a Function for Envelope Gene Products

Abstract

A B S T R A C TERV3 (HERV-R) is a complete human endogenous retrovirus located on the long arm of chromosome 7. It is expressed in several human tissues as LTR env spliced transcripts (9 and 3.5 kb). The highest level of expression is to be found in placenta and virus expression is down-regulated in choriocarcinoma cell lines. By means of in situ hybridization, the expression of ERV3 =was studied in selected human reproductive and embryonic tissues. It is concluded that (a) ERV3 env is expressed in syncytiotrophoblasts not only in the placenta but also in hydatidiform moles and choriocarcinomas ( irrespective of origin) (b) ERV3 expression in placenta correlates to cell fusion but probably not to the fertilization process itself (c) ERV3 %is highly expressed in certain cells in spermatogenesis but not in the Sertoli or Leydig cells, and finally (d) ERV3 env is expressed in certain embryonic tissues such as the adrenal gland and nervous tissues.

Perspective: Transposable Elements, Parasitic Dna, and Genome Evolution

“…A highly conserved portion of the env gene of both endogenous and exogenous retroelements has been shown to be immunosuppressive (Denner 1998). Further, the tissues in which it is expressed, such as the placenta, are precisely those that one would expect if the purpose of the expression were to protect the embryo from attack (Huang and Calarco 1981;Larsson et al 1994;Venables et al 1995). Thus, it has been proposed that some endogenous retroelements in mammals have been recruited in order to make vivipary possible (Venables et al 1995;Villarreal 1997).…”

Detecting the expression of human endogenous retrovirus E envelope transcripts in human prostate adenocarcinoma

“…ERV3 env mRNAs are expressed in placenta and in some tumor cell lines. [13][14][15][16] ERV3 expression may play a pathogenic role in human inflammatory vascular disease. 17 In humans, the discovery of the expression of HERV mRNA, HERV proteins, and even HERV particles associated with human diseases, especially malignant disease, has increased in recent years, 18 -22 although a defined role for HERVs in human physiology or pathophysiology has remained elusive.…”

Retrovirus endógenos humanos: Significado biológico e implicaciones evolutivas

“…De hecho, las primeras observaciones de partículas retrovirales se remontan a los años 70 en placentas normales (Imamura et al, 1976;Dirksen y Levy, 1977;Daniel y Chilton, 1978, revisado por Ueno et al, 1983y Hohenadl et al, 1996, donde, además, se detecta una gran actividad de la transcriptasa inversa (Nelson et al, 1978;Larsson et al, 1994). La gran expresión de proteínas de diferentes familias de HERVs en este tejido ha sugerido (Boyd et al, 1993;Villareal, 1997;Harris, 1998) una función para ellos en el fenóme-no mismo de la placentación, que, pese a su enorme importancia, es un proceso poco comprendido, y cuya aparición sigue siendo un interrogante evolutivo de primer orden.…”