Transient expression of a translation initiation factor is conservatively associated with embryonic gene activation in murine and bovine embryos.
In the present study the abundance of mRNAs for eukaryotic translation initiation factors eIF-1A (formerly known as eIF-4C), -2alpha, -4A, -4E, and -5 was examined in in vivo-derived mouse embryos throughout preimplantation development using a semiquantitative reverse transcription-polymerase chain reaction assay. Although the mRNA profile for each gene is unique, only mRNA for eIF-1A transiently increases during embryonic gene activation (EGA) at the 2-cell stage, and this was confirmed by an independent hybridization-based assay. In in vitro-developed bovine embryos, mRNA for eIF-1A was transiently detected at the 8-cell stage, when the major activation of the genome occurs in this species. As in the mouse, detection in 8-cell bovine embryos was sensitive to the transcriptional inhibitor alpha-amanitin. It was also observed at the same time relative to cleavage in embryos cultured in defined medium under a reduced oxygen environment, and in medium supplemented with serum and somatic cells in 5% CO2 in air. Neither the chronology of early cleavage divisions nor the yield of bovine blastocysts differed in these culture media. Our results suggest that transient expression of eIF-1A in the mouse and cow is a conserved pattern of gene expression associated with EGA in mammals.
De Sousa
P A
PA
Departments of Obstetrics and Gynaecology and Physiology, University of Western Ontario, London,Ontario, Canada N6A 5C1.
Watson
A J
AJ
Schultz
R M
RM
D000546:Amanitins / Q000494:pharmacology; D000818:Animals; D015152:Blotting, Northern; D002417:Cattle; D017124:Conserved Sequence; D004247:DNA / Q000096:biosynthesis / Q000235:genetics; D053938:DNA Fragmentation / Q000235:genetics / Q000502:physiology; D004622:Embryo, Mammalian / Q000502:physiology*; D047108:Embryonic Development / Q000235:genetics; D015977:Eukaryotic Initiation Factor-1; D040061:Eukaryotic Initiation Factor-5; D005260:Female; D005307:Fertilization in Vitro; D005786:Gene Expression Regulation / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology*; D051379:Mice; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D010448:Peptide Initiation Factors / Q000096:biosynthesis* / Q000235:genetics; D011247:Pregnancy; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015533:Transcriptional Activation
D000546:Amanitins; D015977:Eukaryotic Initiation Factor-1; D040061:Eukaryotic Initiation Factor-5; D019384:Nucleic Acid Synthesis Inhibitors; D010448:Peptide Initiation Factors; D012333:RNA, Messenger; C026022:eukaryotic peptide initiation factor-1A; D004247:DNA