Placental endogenous retrovirus (ERV): structural, functional, and evolutionary significance

Area of Science:

• Reproductive biology
• Evolutionary biology
• Virology

Background:

• Endogenous retroviruses (ERVs) have been detected in mammalian placentas for 25 years.
• Recent molecular data support earlier electron microscopy findings on placental ERVs.
• The precise role of ERVs in placental function remains largely unknown.

Purpose of the Study:

• To review evidence for ERVs in human and animal placental tissues.
• To explore the functional significance of ERVs in placental invasiveness and maternal immunosuppression.
• To evaluate the hypothesis that ERVs influenced the evolution of placental mammals.

Main Methods:

• Review of existing molecular biological and electron microscopic data.
• Integration of findings on ERVs in placental and other tissues (e.g., teratocarcinoma cells).
• Discussion of ERVs in relation to metalloproteinases, immunosuppression, growth factors, and protooncogenes.

Main Results:

• Evidence confirms the presence of ERVs in placental tissues across species.
• Potential roles for ERVs in placental invasiveness and maternal immune modulation are discussed.
• A link between ERVs, protooncogenes, and trophoblast malignancy is explored.

Conclusions:

• Ancient trophoblastic ERVs may have been crucial in the evolutionary divergence of placental mammals.
• Further research is needed to fully elucidate the functional significance of ERVs in pregnancy.
• ERVs offer insights into placental development, structure, and evolutionary history.