Abstract
Reproductive aging is characterized by a marked decline in oocyte quality that contributes to infertility, miscarriages, and birth defects. This decline is multifactorial, and the underlying mechanisms are under active investigation. Here, we performed RNA-Seq on individual growing follicles from reproductively young and old mice to identify age-dependent functions in oocytes. This unbiased approach revealed genes involved in cellular processes known to change with age, including mitochondrial function and meiotic chromosome segregation, but also uncovered previously unappreciated categories of genes related to proteostasis and organelles required for protein metabolism. We further validated our RNA-Seq data by comparing nucleolar structure and function in oocytes from reproductively young and old mice, as this organelle is central for protein production. We examined key nucleolar markers, including upstream binding transcription factor (UBTF), an RNA polymerase I cofactor, and fibrillarin, an rRNA methyltransferase. In oocytes from mice of advanced reproductive age, UBTF was primarily expressed in giant fibrillar centers (GFCs), structures associated with high levels of rDNA transcription, and fibrillarin expression was increased ~2-fold. At the ultrastructural level, oocyte nucleoli from reproductively old mice had correspondingly more prominent fibrillar centers and dense fibrillar centers relative to young controls and more ribosomes were found in the cytoplasm. Taken together, our findings are significant because the growing oocyte is one of the most translationally active cells in the body and must accumulate high-quality maternally derived proteins to support subsequent embryo development. Thus, perturbations in protein metabolism are likely to have a profound impact on gamete health.
Original language | English (US) |
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Pages (from-to) | 1381-1393 |
Number of pages | 13 |
Journal | Aging Cell |
Volume | 16 |
Issue number | 6 |
DOIs | |
State | Published - Dec 2017 |
Funding
This work was supported by the Centers of Biomedical Research Excellence (P20 GM104936, F.E.D). In addition, summer student research for this project was supported by the Kansas Institutional Development Award (IDeA) (P20 GM103418, J.M.K). The Electron Microscopy Research Laboratory and Anatomy/COBRE Confocal Imaging Facility at KUMC are supported in part by NIH COBRE P20GM104936, and the JEOL JEM-1400 TEM used in the study was purchased with funds from S10RR027564. The Histology Core at KUMC is supported by P30 HD002528 (Kansas IDDRC). We would like to acknowledge Dr. Henry Yeh (Department of Biostatistics, KUMC) for assistance with statistical analyses and Allison Peak (Molecular Biology, SIMR) for assistance in the preparation of RNA-Seq libraries. We also thank Dr. Richard Schultz (Department of Biology, University of Pennsylvania) for his critical comments on the manuscript. This work was supported by the Centers of Biomedical Research Excellence (P20 GM104936, F.E.D). In addition, summer student research for this project was supported by the Kansas Institutional Development Award (IDeA) (P20 GM103418, J.M.K). The Electron Microscopy Research Laboratory and Anatomy/COBRE Confocal Imaging Facility at KUMC are supported in part by NIH COBRE P20GM104936, and the JEOL JEM-1400 TEM used in the study was purchased with funds from S10RR027564. The Histology Core at KUMC is supported by P30 HD002528 (Kansas IDDRC).
Keywords
- folliculogenesis
- nucleolus
- oogenesis
- proteostasis
- reproductive aging
- ribosome
ASJC Scopus subject areas
- Aging
- Cell Biology