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Epigenetic modifications necessary for normal development are established during oocyte growth in mice
1Department of Animal Science, Tokyo University of Agriculture, Setagaya-ku, Tokyo 156-8502, Japan.
Biology of Reproduction
|February 24, 2000
Summary
Maternal chromatin gains the ability to support full-term development during oocyte growth. This crucial epigenetic reprogramming occurs in the latter half of oocyte growth, specifically when oocytes reach 50-69 micrometers in diameter.
Area of Science:
- Reproductive Biology
- Developmental Biology
- Epigenetics
Background:
- Maternal chromatin must acquire specific epigenetic modifications to support embryonic development.
- The precise timing of this chromatin maturation during oocyte growth is not well understood.
Purpose of the Study:
- To determine the specific stage of oocyte growth when maternal chromatin becomes competent for full-term development.
- To investigate the influence of oocyte origin on developmental potential.
Main Methods:
- Constructed mature metaphase II-arrested oocytes with chromatin from various oocyte growth stages via micromanipulation.
- Assessed developmental potential by in vitro fertilization, in vitro blastocyst development, and embryo transfer to recipients.
Main Results:
- The origin of maternal chromatin did not impact oocyte maturation, fertilization, or in vitro blastocyst development rates.
- Maternal chromatin acquired the capacity for term development during the latter half of oocyte growth (oocytes 60-69 µm in juvenile mice, 50-59 µm in adult mice).
Conclusions:
- Epigenetic modifications essential for post-implantation development are acquired during a defined period of oocyte growth.
- Oocyte size serves as a key indicator for chromatin competence in supporting full-term development.