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Placental Development and Endogenous Retroviruses.
Kazuhiko Imakawa1, So Nakagawa2, Kazuya Kusama1
1Animal Resource Science Center, The University of Tokyo.
Uirusu
|May 10, 2017
Summary
Endogenous retroviruses (ERVs) have been co-opted during mammalian evolution to form the placenta, driving trophoblast cell fusion and placental diversity. This "baton pass" hypothesis explains ERV
Area of Science:
- Evolutionary biology
- Developmental biology
- Genomics
Background:
- The placenta, a key organ for mammalian reproduction, has a complex evolutionary history.
- Trophoblast cells, crucial for placental function, exhibit high expression of endogenous retroviruses (ERVs) and LTR retrotransposons.
- The evolutionary role of ERV expression in placental development remains incompletely understood.
Purpose of the Study:
- To review the diversity of placental structures across mammalian species.
- To explore the involvement of specific ERVs, such as Peg10 and Peg11, in ancient placental development.
- To examine the function of env-related genes in trophoblast cell fusion and syncytiotrophoblast formation.
Main Methods:
- Comparative analysis of placental structures across mammalian orders.
- Review of genetic data on ERV expression in trophoblast cells.
- Examination of the "baton pass" hypothesis regarding ERV integration and cell fusion.
Main Results:
- Mammalian placental structures exhibit greater diversity than previously anticipated.
- Specific ERVs (Peg10, Peg11) are linked to ancient placental development.
- Env-related genes (Syncytins, Fematrin-1) mediate trophoblast cell fusion, forming the syncytiotrophoblast.
Conclusions:
- Endogenous retroviral gene variants integrated into mammalian genomes have likely replaced ancestral genes responsible for cell fusion.
- The "baton pass" hypothesis suggests successive ERV integrations facilitated trophoblast cell fusion, enhancing placental morphology and reproductive success.
- ERV-driven cell fusion contributes to fetal survival and reproductive advantage in placental mammals.
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