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Gene-specific timing and epigenetic memory in oocyte imprinting
Diana Lucifero1, Mellissa R W Mann, Marisa S Bartolomei
1McGill University, Montreal Children's Hospital Research Institute and Departments of Pediatrics, Human Genetics and Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada H3H 1P3.
Human Molecular Genetics
|March 5, 2004
Summary
DNA methylation marks imprinted genes for parent-specific expression. This study reveals asynchronous methylation acquisition in growing mouse oocytes, linked to oocyte size and DNA methyltransferase accumulation.
Area of Science:
- Epigenetics
- Developmental Biology
- Genomics
Background:
- Imprinted genes require differential marking during germ cell development for parent-of-origin specific expression.
- A subset of imprinted genes gains DNA methylation during oocyte growth, but the timing and mechanisms remain unclear.
Purpose of the Study:
- To investigate the timing and mechanisms of DNA methylation acquisition at specific imprinted genes (Snrpn, Igf2r, Peg1, Peg3) in postnatal growing mouse oocytes.
- To explore the relationship between methylation acquisition, oocyte growth, and the expression of DNA methyltransferases.
Main Methods:
- Analysis of DNA methylation at differentially methylated regions (DMRs) of selected imprinted genes in postnatal mouse oocytes.
- Assessment of parental allele recognition in the absence of DNA methylation.
- Correlation of methylation acquisition with oocyte diameter and transcript levels of DNA methyltransferases (Dnmt3a, Dnmt3b, Dnmt3L).
Main Results:
- Methylation acquisition occurred asynchronously across different imprinted genes.
- Parental alleles retained epigenetic memory, recognized in a parental-specific manner even without DNA methylation.
- Methylation acquisition correlated with increasing oocyte diameter and the accumulation of Dnmt3a, Dnmt3b, and Dnmt3L transcripts.
- Methylation of intracisternal A particle (IAP) sequences also occurred during this oocyte growth window.
Conclusions:
- Provides insights into the epigenetic mechanisms governing imprint acquisition during female germline development.
- Suggests a link between oocyte growth, DNA methyltransferase expression, and the establishment of DNA methylation.
- Findings have implications for understanding reproductive technologies and epigenetic inheritance.