REGULAR ARTICLES

Cell Research (2003); 13(3):179-185

Delay of ZGA initiation occurred in 2-cell blocked mouse embryos

Jia Jing QIU^1,*, Wu Wen ZHANG^2,*, Zhi Li WU, Yi Hong WANG, Min QIAN², Yi Ping LI^**

¹Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 200031 Shanghai, China
²School of Life Science, East China Normal University, 200062 Shanghai, China

Received Sep-3-2002 Revised May-10-2003 Accepted May-12-2003

Correspondence: Yi Ping LI 0086-21-54921415 (phone) oocyte@sunm.shcnc.ac.cn Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 200031 Shanghai, China

Table of Contents Download as printable (PDF) file -1.25M Full Text (html)file Search Medline for articles by: Yi Ping LI

One-cell mouse embryos from KM strain and B6C3F1 strain were cultured in M16 medium, in which 2-cell block generally occurs. Embryos of KM strain exhibited 2-cell block, whereas B6C3F1 embryos, which are regarded as a nonblocking strain, proceeded to the 4-cell stage in our culture condition. It is often assumed that the block of early development is due to the failure of zygotic gene activation (ZGA) in cultured embryos. In this study we examined protein synthesis patterns by two-dimensional gel electrophoresis of [³⁵S] methionine radiolabeled 2-cell embryos. Embryos from the blocking strain and the nonblocking strain were compared in their development both in vitro and in vivo. The detection of TRC expression, a marker of ZGA, at 42 h post hCG in KM embryos developed in vitro suggested that ZGA was also initiated even in the 2-cell arrested embryos. Nevertheless, a significant delay of ZGA was observed in KM strain as compared with normally developed B6C3F1 embryos. At the very beginning of major ZGA as early as 36 h post hCG, TRC has already been expressed in B6C3F1 embryos developed in vitro and KM embryos developed in vivo. But for 2-cell blocked KM embryos, TRC was still not detectable even at 38 h post hCG. These evidences suggest that 2-cell-blocked embryos do initiate ZGA, and that 2-cell block phenomenon is due not to the disability in initiating ZGA, but to a delay of ZGA.

Key words: mouse embryo, two-cell block, zygotic gene activation (ZGA).