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The methylation pattern of endogenous mouse mammary tumor virus proviral genes is tissue specific and stably
Abstract:
The methylation pattern of mouse mammary tumor virus (MMTV) proviral genes endogenous to the mouse strains C3H, 020, FM/JmsA, C57BL6, and BALB/c were investigated in various organs and mammary tumor tissue. Digestion of DNA with EcoRI or with EcoRI and HpaII followed by Southern blotting analysis and hybridization to a nick-translated MMTV DNA, allowed the distinction between the fully methylated and hypomethylated gene copies. MMTV proviral gene methylation was found to be organ specific, and the methylation pattern is stably inherited. The same proviral units present in different strains of mice exhibit the same organ-specific methylation patterns. Although proviral genes are normally heavily methylated in all tissues, hypomethylation of endogenous proviral genes was found in organs not known to express MMTV.
Insights
Methylation patterns of mouse mammary tumor virus (MMTV) proviral genes are organ-specific and stably inherited across different mouse strains. Hypomethylation occurs in tissues not typically expressing MMTV.
Area of Science:
- Genetics
- Epigenetics
- Virology
Background:
- Endogenous mouse mammary tumor virus (MMTV) proviral genes are integrated into the mouse genome.
- Epigenetic modifications, such as DNA methylation, regulate gene expression.
- Understanding MMTV methylation is crucial for studying its role in host-pathogen interactions and potential oncogenesis.
Purpose of the Study:
- To investigate the methylation patterns of endogenous MMTV proviral genes in various organs and mammary tumor tissues of different mouse strains.
- To determine if MMTV methylation patterns are organ-specific and heritable.
- To identify potential correlations between MMTV hypomethylation and gene expression in non-canonical tissues.
Main Methods:
- DNA extraction from various organs and mammary tumor tissues of five mouse strains (C3H, 020, FM/JmsA, C57BL6, BALB/c).
- DNA digestion using restriction enzymes EcoRI and HpaII.
- Southern blotting analysis and hybridization with a nick-translated MMTV DNA probe.
- Distinguishing between fully methylated and hypomethylated MMTV proviral gene copies.
Main Results:
- MMTV proviral gene methylation patterns were found to be organ-specific.
- The observed methylation patterns were stably inherited within mouse strains.
- Different mouse strains exhibited the same organ-specific methylation patterns for the same proviral units.
- Hypomethylation of endogenous MMTV proviral genes was detected in organs not known for MMTV expression, despite normal heavy methylation in most tissues.
Conclusions:
- Endogenous MMTV proviral gene methylation is a highly organ-specific epigenetic phenomenon.
- These methylation patterns are conserved across different mouse strains and are stably inherited.
- The presence of hypomethylated MMTV proviral genes in non-expressing organs suggests a complex regulatory landscape and potential for alternative roles or reactivation.