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Human oocytes express murine retroviral equivalents
B O Nilsson1, P O Kättström, P Sundström
1Department of Human Anatomy, Biomedical Centre, Uppsala, Sweden.
Abstract:
Unfertilized human oocytes expressed a gp70-related epitope as observed when staining section immunocytochemically with a panel of monoclonal antibodies against gp70 of murine leukemia virus. Some oocytes also expressed virus-like particles at the cell membrane. Follicular fluids, corresponding to these oocytes, contained p30- and gp70-related antigens, reverse transcriptase, and an increased titer of interferon. The three- to four-cell human cleavage stages did not contain the gp70-related epitope. It is concluded that human oocytes, but not early cleavage stages, express products that suggest the presence of an active endogenous retrovirus genome.
Insights
Unfertilized human oocytes show evidence of an active endogenous retrovirus genome, expressing specific proteins and virus-like particles. Early human embryo cleavage stages do not exhibit these retroviral markers.
Area of Science:
- Reproductive biology
- Virology
- Molecular biology
Background:
- Endogenous retroviruses (ERVs) are integrated into host genomes and can be expressed.
- Expression of ERV proteins in human oocytes is not well understood.
- gp70 is a retroviral envelope protein found in murine leukemia virus.
Purpose of the Study:
- To investigate the presence of retroviral products in human oocytes and early cleavage stages.
- To determine if human oocytes express gp70-related epitopes and virus-like particles.
- To analyze follicular fluids for retroviral antigens and enzymatic activity.
Main Methods:
- Immunocytochemical staining of human oocytes using monoclonal antibodies against gp70.
- Electron microscopy to detect virus-like particles.
- Biochemical assays on follicular fluids for p30 and gp70 antigens, reverse transcriptase, and interferon.
Main Results:
- Unfertilized human oocytes expressed a gp70-related epitope.
- Virus-like particles were observed on the surface of some oocytes.
- Follicular fluids contained p30 and gp70 antigens, reverse transcriptase, and increased interferon.
- gp70 epitope was absent in three- to four-cell human cleavage stages.
Conclusions:
- Human oocytes express products indicative of an active endogenous retrovirus genome.
- Early human cleavage stages lack these specific retroviral markers.
- These findings suggest a potential role for endogenous retroviruses in early human development.