The absence of a Ca(2+) signal during mouse egg activation can affect parthenogenetic preimplantation development, gene expression patterns, and blastocyst quality.
A series of Ca(2+) oscillations during mammalian fertilization is necessary and sufficient to stimulate meiotic resumption and pronuclear formation. It is not known how effectively development continues in the absence of the initial Ca(2+) signal. We have triggered parthenogenetic egg activation with cycloheximide that causes no Ca(2+) increase, with ethanol that causes a single large Ca(2+) increase, or with Sr(2+) that causes Ca(2+) oscillations. Eggs were co-treated with cytochalasin D to make them diploid and they formed pronuclei and two-cell embryos at high rates with each activation treatment. However, far fewer of the embryos that were activated by cycloheximide reached the blastocyst stagecompared tothose activated by Sr(2+) orethanol. Any cycloheximide-activated embryos that reached the blastocyst stage had a smaller inner cell mass number and a greater rate of apoptosis than Sr(2+)-activated embryos. The poor development of cycloheximide-activated embryos was due to the lack of Ca(2+) increase because they developed to blastocyst stages at high rates when co-treated with Sr(2+) or ethanol. Embryos activated by either Sr(2+) or cycloheximide showed similar signs of initial embryonic genome activation (EGA) when measured using a reporter gene. However, microarray analysis of gene expression at the eight-cell stage showed that activation by Sr(2+) leads to a distinct pattern of gene expression from that seen with embryos activated by cycloheximide. These data suggest that activation of mouse eggs in the absence of a Ca(2+) signal does not affect initial parthenogenetic events, but can influence later gene expression and development.
Rogers
N T
NT
Department of Anatomy and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK.
Halet
G
G
Piao
Y
Y
Carroll
J
J
Ko
M S H
MS
Swann
K
K
D000818:Animals; D017209:Apoptosis; D001755:Blastocyst / Q000378:metabolism*; D020013:Calcium Signaling; D049109:Cell Proliferation; D002970:Cleavage Stage, Ovum; D003513:Cycloheximide / Q000494:pharmacology; D046149:Embryo Culture Techniques; D047108:Embryonic Development; D000431:Ethanol / Q000494:pharmacology; D005260:Female; D020869:Gene Expression Profiling / Q000379:methods; D018507:Gene Expression Regulation, Developmental; D020287:In Situ Nick-End Labeling; D051379:Mice; D008815:Mice, Inbred Strains; D020411:Oligonucleotide Array Sequence Analysis; D010312:Parthenogenesis; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology
D011500:Protein Synthesis Inhibitors; D000431:Ethanol; D003513:Cycloheximide