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Updated: Jun 19, 2026
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Ex vivo Culture of Human Placental Explants for the Study of Viral Transmission Across the Maternal-Fetal Interface
Published on: December 30, 2025
Update on endogenous retroviruses in cattle placenta
1School of Pharmaceutical Sciences, Ohu University, Fukushima 963-8611, Japan.
The Journal of Reproduction and Development
|June 17, 2026
Summary
Endogenous retroviruses (ERVs) provide essential functions in cattle placenta, acting as structural fusogens and immune regulators. These ancient viral elements offer crucial "hardware" and "software" for successful bovine pregnancy.
Area of Science:
- Reproductive biology and genomics
- Mammalian evolutionary genomics
- Placental development and function
Background:
- Endogenous retroviruses (ERVs) are integrated into mammalian genomes, with significant roles in placental evolution, particularly in primates and mice.
- Their specific organization and functions in epitheliochorial placentas, like those in cattle, are less understood compared to other species.
- Understanding ERVs in cattle is crucial for insights into pregnancy, reproduction, and comparative genomics.
Purpose of the Study:
- To provide an updated view of endogenous retroviruses (ERVs) in the cattle placenta by integrating genomic, transcriptomic, and functional data.
- To define the interacting roles of ERVs in supporting bovine pregnancy, termed Roles 1-3.
- To highlight outstanding questions and outline experimental strategies for future research on ERV contributions to cattle reproduction.
Main Methods:
- Genomic analysis to identify and characterize ERV elements and their distribution in the bovine genome (ARS-UCD2.0 assembly).
- Transcriptomic analysis to assess ERV expression patterns in placental tissues.
- Functional data integration to infer the roles of ERVs in placental development and function, including promoter methylation and chromatin control.
Main Results:
- Identified ERVs contributing to placental function through three main roles: structural fusogens (Role 1), immune-inducible enhancers (Role 2), and epigenetic regulators (Role 3).
- Role 1 involves ERVs like syncytin-Rum1 and BERV-K1 supporting trophoblast cell fusion for the synepitheliochorial interface.
- Role 2 highlights ERV/LTR enhancers (e.g., MER41_BT, Bov-A2) responding to immune stimulation (IFNT/IFNG) and regulating interferon-pathway genes.
- Role 3 demonstrates ERVs (e.g., BERV-K1, BERV-K3) involved in epigenetic gating and signaling, with developmental changes in promoter methylation and chromatin control.
- ERV-derived elements constitute significant portions of the genome (3.21% UNION, 4.71% LTR/ERV) and are organized into ancient and younger lineages.
Conclusions:
- Endogenous retroviruses provide essential 'hardware' (fusogens) and 'software' (enhancers, epigenetic switches) for bovine pregnancy.
- These ERV-derived elements play multifaceted roles in establishing the placental interface, regulating immune responses, and controlling gene expression during gestation.
- Further research integrating genome editing, epigenome profiling, and single-cell approaches is needed to fully elucidate ERV impacts on cattle implantation, placentome development, and reproductive success.
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