Analysis of thymidine kinase gene expression in preimplantation mouse embryos.
Thymidine kinase (TK) activity was examined during the development of preimplantation mouse embryos. TK activity was increased approximately 20-fold from day 2 embryos (2-cell) to day 5 embryos (late blastocyst). TK activity did not change along with the progression into S-phase of the first and the second cell cycles but increased sharply at S-phase of the third cell cycle. Analysis of TK mRNA with a reverse transcription-polymerase chain reaction (RT-PCR) method showed that the level of TK mRNA was low in ovulated eggs and 1-cell embryos and was hardly detectable in day 2 embryos (2-cell), but sharply increased in day 3 embryos (mixture of 5- to 8-cell and morula). The functional role of 5'-flanking sequence of TK gene was also investigated in preimplantation embryos after microinjection with the DNA construct of 5'-flanking sequence of TK (2.4 kb) linked to bacterial lacZ gene (TK2.5lacZ) into the pronucleus of 1-cell and subsequently by histochemical staining with X-gal. beta-Galactosidase activity was first detected in day 3 embryos (8-cell), and 30% of embryos were stained with X-gal in day 4 and day 5 embryos, respectively. These results show that an increase in TK activity occurred after 2-cell stage, and this increase was primarily due to the embryonic activation of TK gene expression. Also, it appears that the 5'-flanking sequence of TK may directly regulate the TK gene expression at the transcriptional level during preimplantation murine development.
Lee
D K
DK
Department of Molecular Biology, College of Natural Sciences, Seoul National University, Korea.
Sun
W
W
Rhee
K
K
Cho
H
H
Lee
C C
CC
Kim
K
K
D000818:Animals; D001483:Base Sequence; D001755:Blastocyst / Q000201:enzymology*; D018076:DNA, Complementary; D005314:Embryonic and Fetal Development; D005260:Female; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D018014:Gene Transfer Techniques; D051379:Mice; D008969:Molecular Sequence Data; D010957:Plasmids; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D013937:Thymidine Kinase / Q000235:genetics*
D018076:DNA, Complementary; D012333:RNA, Messenger; D013937:Thymidine Kinase