Mol. Hum. Reprod. Advance Access originally published online on April 1, 2005
Molecular Human Reproduction 2005 11(5):325-333; doi:10.1093/molehr/gah166
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Temporary developmental arrest after storage of fertilized mouse oocytes at 4°C: effects on embryonic development, maternal mRNA processing and cell cycle
1Division of Basic Molecular Science and Molecular Medicine, School of Medicine, 2Center of Genetic Engineering for Human Diseases and 3Department of Molecular and Developmental Science, The Institute of Medical Sciences, Tokai University, Bohseidai, Isehara, Kanagawa 259-1193, Japan
4 To whom correspondence should be addressed at: Division of Basic Molecular Science and Molecular Medicine, School of Medicine, Tokai University, Bohseidai, Isehara, Kanagawa 259-1193, Japan. Email: sakurai{at}is.icc.u-tokai.ac.jp
The aim of this study was to examine whether fertilized mouse oocytes can survive after short-term incubation (for 648 h) at 4°C. When fertilized oocytes of ICR and C57BL/6 (B6) strain were incubated at 4°C and returned to normal culture conditions (37°C), development of these 4°C-treated embryos for up to 12 h (for ICR) to blastocyst stage did not differ from that of untreated oocytes. Even 4°C-treated embryos for 48 h developed to blastocysts at relatively good rates (33.3% for ICR and 50.8% for B6). The in vivo development of 4°C-treated embryos for 12, 24 and 36 h to fetal stage was similar to that of untreated ones. BrdU labelling assay revealed temporary cessation of DNA replication in 4°C-treated fertilized oocytes. Post-fertilization events including cytoplasmic polyadenylation of maternal mRNAs, mRNA degradation of a cell cycle-related gene and elevated mRNA expression of zygotic gene activation-related genes were temporarily suppressed in 4°C-treated embryos. These findings indicate that 4°C-treatment of fertilized murine oocytes results in temporary cessation of molecular events. We also show that 4°C-treated fertilized oocytes for 12 h can be used for preparation of transgenic mice.
Key words: cell cycle/fertilized oocyte/low temperature preservation/maternal RNA/4°C-storage