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Updated: May 26, 2025
Defining the Program of Maternal mRNA Translation during In vitro Maturation using a Single Oocyte Reporter Assay
Published on: June 16, 2021
Disruption of oocyte SUMOylation impacts critical regulatory processes during folliculogenesis in mice†
Zian Liao1,2, Tessa E Steenwinkel1,3, Bruno Moscoso1
1Department of Pathology & Immunology, Baylor College of Medicine, Houston, TX, United States.
Abstract:
The conjugation of small ubiquitin-like modifiers (SUMO) to target proteins, known as SUMOylation, plays a crucial role in regulating protein homeostasis, activity, interaction with other proteins, and subcellular localization. Loss of SUMOylation in nongrowing oocytes by conditional deletion of the E2 SUMO conjugating enzyme, Ube2i, at the primordial follicle stage leads to female sterility due to complex changes in oocyte development, including altered folliculogenesis, defective meiotic progression, and premature loss of the ovarian reserve. In this study, proteomics was used to compare control and Ube2i conditional knockout ovaries during the first wave of folliculogenesis to identify key differences that may drive the premature follicle loss phenotype. Label-free mass spectrometry results showed that 238 proteins were significantly altered more than 2-fold (p < 0.05). Proteins upregulated in the Ube2i conditional knockout ovaries included those involved in mRNA splicing and WNT signaling, while those downregulated were related to metabolism, mitochondria, and the maternal effect proteins NLRP2 and NLRP9B. The majority of differentially expressed proteins showed no change by transcriptome analysis, indicating protein level regulation and revealing potential SUMOylation targets with necessary roles in oocyte and follicle development.
Insights
Loss of SUMOylation in oocytes due to Ube2i deletion causes female sterility. Proteomics revealed altered protein levels affecting mRNA splicing, WNT signaling, metabolism, and maternal factors, impacting follicle development.
Area of Science:
- Reproductive Biology
- Molecular Biology
- Proteomics
Background:
- SUMOylation regulates protein function, homeostasis, and localization.
- Loss of Ube2i SUMOylation in oocytes causes female sterility and premature ovarian reserve depletion.
- Oocyte development is complex and relies on precise molecular regulation.
Purpose of the Study:
- To identify key proteomic differences in ovaries lacking Ube2i during early folliculogenesis.
- To uncover proteins and pathways affected by SUMOylation loss that contribute to follicle loss.
- To reveal potential SUMOylation targets critical for oocyte and follicle development.
Main Methods:
- Conditional knockout of Ube2i in mouse oocytes.
- Label-free mass spectrometry-based proteomics.
- Comparative analysis of control and Ube2i knockout ovarian tissue.
- Transcriptome analysis for comparison with proteomic data.
Main Results:
- 238 proteins showed significant alterations (>2-fold change, p<0.05) in Ube2i knockout ovaries.
- Upregulated proteins were associated with mRNA splicing and WNT signaling.
- Downregulated proteins were linked to metabolism, mitochondria, and maternal effect proteins (NLRP2, NLRP9B).
- Most differentially expressed proteins were not altered at the transcriptome level, indicating post-transcriptional regulation.
Conclusions:
- SUMOylation by Ube2i is essential for maintaining ovarian reserve and normal oocyte development.
- Altered protein expression in mRNA splicing, WNT signaling, and metabolism contributes to the sterile phenotype.
- Proteomics identified novel SUMOylation targets crucial for ovarian follicle health and function.
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