Temporary developmental arrest after storage of fertilized mouse oocytes at 4°C: Effects on embryonic development, maternal mRNA processing and cell cycle

Abstract

The aim of this study was to examine whether fertilized mouse oocytes can survive after short-term incubation (for 6-48 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. © The Author 2005. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved.