[HTML][HTML] The absence of a Ca2+ signal during mouse egg activation can affect parthenogenetic preimplantation development, gene expression patterns, and …

NT Rogers, G Halet, Y Piao, J Carroll, MSH Ko… - …, 2006 - rep.bioscientifica.com
NT Rogers, G Halet, Y Piao, J Carroll, MSH Ko, K Swann
Reproduction, 2006rep.bioscientifica.com
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 …
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.
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