Effect of vitrification on protein O-GlcNAcylation in mouse metaphase II oocytes
Kang Zhang1, Tianyang Lan1, Feifei Lin1
1Key Laboratory of Animal Biotechnology of the Ministry of Agriculture, College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China.
In Brief:
Oocyte vitrification leads to DNA hypomethylation, which results in defect in early embryo development. This study reveals that oocyte vitrification impairs the DNA methylation pattern by influencing protein O-GlcNAcylation.
Abstract:
Oocyte vitrification leads to decreased DNA methylation levels, which impairs the quality and the developmental potential of oocytes. However, the underlying molecular mechanism still need to be further revealed. In this study, mouse metaphase II (M II) oocytes were frozen by vitrification technology, while fresh oocytes were used as the control group. The effect of oocyte vitrification on protein O-GlcNAcylation and its impact on the developmental potential of oocytes were elucidated. We found that the protein O-GlcNAcylation levels were significantly increased in vitrified oocytes. Increase of protein O-GlcNAcylation levels in control oocytes by PUGNAc (an O-GlcNAcase inhibitor) decreases blastocyst rate after parthenogenetic activation (20.82% in PUGNAc-treated group; 53.82% in control group, P < 0.05). We also discovered that DNA methylation was disrupted in two-cell embryos derived from vitrified oocytes, resulting in decreased 5mC and increased 5hmC, showing similar phenotypes to that derived from PUGNAc-treated oocytes. In vitrified and PUGNAc-treated oocytes, O-GlcNAcylated TET3 was significantly increased. Notably, by inhibiting protein O-GlcNAcylation in vitrified oocytes using OSMI1 (an O-GlcNAc transferase inhibitor) we restored the DNA methylation in two-cell embryos and ameliorated the developmental defects in early embryo. Thus, elevated protein O-GlcNAcylation in vitrified oocytes is an essential contributor to their declining embryonic developmental potential. Modulation of protein O-GlcNAcylation improves the developmental potential of vitrified oocytes.
Insights
Oocyte vitrification impairs early embryo development by altering DNA methylation patterns. This study shows elevated protein O-GlcNAcylation in vitrified oocytes contributes to these defects, and inhibiting it can restore developmental potential.
Area of Science:
- Reproductive Biology
- Epigenetics
- Developmental Biology
Background:
- Oocyte vitrification, a method for preserving fertility, can negatively impact oocyte quality and early embryo development.
- The precise molecular mechanisms underlying vitrification-induced developmental defects, particularly concerning DNA methylation, remain incompletely understood.
Purpose of the Study:
- To investigate the effect of oocyte vitrification on protein O-GlcNAcylation.
- To elucidate the role of protein O-GlcNAcylation in DNA methylation disruption and impaired developmental potential following oocyte vitrification.
- To explore therapeutic strategies targeting protein O-GlcNAcylation to improve vitrified oocyte quality.
Main Methods:
- Mouse metaphase II oocytes were subjected to vitrification or used fresh as controls.
- Protein O-GlcNAcylation levels were assessed in vitrified and fresh oocytes.
- Oocytes were treated with O-GlcNAcase inhibitor (PUGNAc) or O-GlcNAc transferase inhibitor (OSMI1) to modulate O-GlcNAcylation.
- Parthenogenetic activation and early embryo development rates (e.g., blastocyst formation) were evaluated.
- DNA methylation patterns (5mC and 5hmC) and TET3 expression were analyzed in resulting embryos.
Main Results:
- Vitrification significantly increased protein O-GlcNAcylation levels in mouse oocytes.
- Elevated O-GlcNAcylation in control oocytes reduced blastocyst formation rates after parthenogenetic activation.
- Vitrified oocytes exhibited disrupted DNA methylation (decreased 5mC, increased 5hmC) and elevated O-GlcNAcylated TET3.
- Inhibiting O-GlcNAcylation in vitrified oocytes with OSMI1 restored DNA methylation patterns and improved early embryo development.
Conclusions:
- Elevated protein O-GlcNAcylation is a key factor contributing to the decline in developmental potential of vitrified oocytes.
- O-GlcNAcylation influences DNA methylation dynamics, impacting early embryonic development.
- Modulating protein O-GlcNAcylation presents a promising therapeutic approach to enhance the quality and developmental competence of vitrified oocytes.
