Related Experiment Videos
DNA methylation, retroviruses, and embryogenesis
Abstract:
By exposing preimplantation embryos to Moloney leukemia virus (M-MuLV), we have previously derived substrains of mice designated as Mov-1-Mov-13 which genetically transmit the virus from one generation to the next. In some of the substrains the inserted viral genome becomes activated at specific stages of embryogenesis and the available evidence suggests that these viral genomes are developmentally regulated. To investigate the effect of cellular differentiation on virus expression, M-MuLV was introduced either into preimplantation or post-implantation mouse embryos or into embryonal carcinoma (EC) cells. Whereas preimplantation embryos or EC cells are not permissive for virus expression, efficient replication occurred in postimplantation embryos or in differentiated cell lines. The viral genomes introduced into early embryonal cells were highly methylated and noninfectious when analyzed in the adult. In contrast, viral genomes introduced into postimplantation embryos or into differentiated cells remained unmethylated and were infectious in a transfection assay. These results demonstrate an efficient de novo methylation activity which appears to be involved in repression of genes introduced into pluripotent embryonal cells and which is not observed in cells of the postimplantation embryo or in differentiated cells in tissue culture.
Insights
This study reveals that early mouse embryos and embryonal carcinoma cells methylate and silence introduced Moloney leukemia virus (M-MuLV) genomes. Later-stage embryos and differentiated cells allow M-MuLV replication, indicating developmental regulation of viral gene expression.
Area of Science:
- Developmental Biology
- Virology
- Epigenetics
Background:
- Moloney leukemia virus (M-MuLV) can be genetically transmitted through mouse substrains (Mov-1-Mov-13).
- Viral genome activation in these substrains suggests developmental regulation of M-MuLV expression.
Purpose of the Study:
- To investigate the impact of cellular differentiation on Moloney leukemia virus (M-MuLV) expression.
- To determine how M-MuLV genome methylation and infectivity are affected by developmental stage.
Main Methods:
- Introduction of M-MuLV into preimplantation embryos, postimplantation embryos, and embryonal carcinoma (EC) cells.
- Analysis of viral genome methylation and infectivity using transfection assays.
- Comparison of M-MuLV replication in different developmental stages and cell types.
Main Results:
- Preimplantation embryos and EC cells were non-permissive for M-MuLV expression, with viral genomes becoming methylated and noninfectious.
- Postimplantation embryos and differentiated cell lines supported efficient M-MuLV replication, with viral genomes remaining unmethylated and infectious.
- Evidence for de novo methylation activity repressing genes in pluripotent embryonal cells was observed.
Conclusions:
- Cellular differentiation plays a critical role in regulating Moloney leukemia virus (M-MuLV) expression and epigenetic state.
- De novo methylation in pluripotent cells acts as a mechanism to repress introduced viral genes.
- Developmental stage significantly influences the permissiveness of mouse cells to M-MuLV replication and epigenetic modification.