Superovulation induces alterations in the epigenome of zygotes, and results in differences in gene expression at the blastocyst stage in mice.
Gamete and embryo manipulations can result in alterations to the epigenome, and are associated with altered gene expression. The initial objective of this study was to determine the transcript level of several epigenetic modifiers in embryos that had been cultured from the 2-cell stage until the late-blastocyst stage in four culture conditions. Cultured embryos were compared to control, in vivo-produced late blastocysts to ascertain if differences in gene expression existed among the culture conditions; none were observed. As all of the embryos used were produced in females that had undergone superovulation, we next compared the transcript level of the same epigenetic modifiers between superovulated, in vivo-produced embryos and embryos produced from natural ovulation. Following in vitro culturing, expression of the genes analyzed was increased in all superovulation groups. We therefore hypothesized that the superovulation procedure-used to increase the number of embryos obtained for experimentation-may have caused an inappropriate acquisition of epigenetic modifications in the maternal genome prior to ovulation, which in turn caused misexpression of genes at the blastocyst stage. To test this hypothesis, we compared the level of global DNA methylation and histone 3 lysine-9 or -14 acetylation in zygotes obtained by natural- or superovulation. Indeed, superovulation decreased global DNA methylation on the maternal pronucleus of zygotes, which inversely correlated with H3K9/14 acetylation. In conclusion, superovulation alters the epigenome of the oocyte, resulting in the dysregulation of gene expression at the blastocyst stage.
Division of Animal Sciences, University of Missouri, Columbia, Missouri.
Sarah Rose
SR
Huffman
Youngju
Y
Pak
Rocío Melissa
RM
Rivera
D000107:Acetylation; D000818:Animals; D001755:Blastocyst / Q000378:metabolism*; D015153:Blotting, Western; D019175:DNA Methylation / Q000502:physiology*; D046149:Embryo Culture Techniques / Q000379:methods*; D044127:Epigenesis, Genetic / Q000235:genetics / Q000502:physiology*; D005260:Female; D005455:Fluorescent Antibody Technique; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D006657:Histones / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D051379:Mice; D018613:Microscopy, Confocal; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013480:Superovulation / Q000502:physiology*
D006657:Histones