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Characterization of oocyte and follicle development in growth differentiation factor-9-deficient mice
M J Carabatsos1, J Elvin, M M Matzuk
1Program in Cell, Molecular and Developmental Biology, Tufts University School of Medicine, Boston, Massachusetts, 02111, USA.
Abstract:
Female mice null for the oocyte-specific gene product, growth differentiation factor-9 (GDF-9), a member of the transforming growth factor-beta superfamily, exhibit primary infertility due to failed ovarian follicular development. The purpose of this study is to characterize oocyte and follicular differentiation as a function of animal age using cell culture and fluorescence, confocal, and electron microscopy. Analysis of follicles from GDF-9 homozygous mutant mice indicates that GDF-9-deficient oocytes grow more rapidly than control oocytes and that follicle growth ceases at the type 3b stage. Based on germinal vesicle (GV) chromatin patterns, fully grown oocytes isolated from GDF-9-deficient mice progress to advanced stages of differentiation equivalent to those found in antral follicles of control (heterozygous) mice. In vitro maturation of oocytes from homozygous mutant mice revealed that most oocytes are capable of resuming meiosis, with the ability to achieve meiotic completion reaching the highest levels in 6-week-old mice. Among the characteristic ultrastructural features of oocytes from homozygous mutant mice are perinuclear organelle aggregation, unusual peripheral Golgi complexes, and a failure to form cortical granules. Modified interconnections between granulosa cells and oocytes were also observed by ultrastructural (EM) and fluorescence microscopic analysis of follicles from GDF-9-deficient mice. These modifications included a decrease in the number of actin-based transzonal processes and modifications of microtubule-based projections that over time gave rise to invasion of the perivitelline space with eventual loss of oocyte viability. These cell-cell aberrations suggest a critical role for GDF-9 in the regulation of growth in preantral follicles through a mechanism involving bidirectional somatic cell-germ cell interactions.
Insights
Growth Differentiation Factor-9 (GDF-9) is crucial for ovarian follicular development in female mice. Its absence causes infertility by disrupting oocyte growth and cell interactions, leading to failed follicle maturation.
Area of Science:
- Reproductive Biology
- Developmental Biology
- Cell Biology
Background:
- Growth Differentiation Factor-9 (GDF-9) is an oocyte-specific gene product vital for ovarian follicular development.
- Deficiency in GDF-9 leads to primary infertility in female mice due to impaired follicle growth.
Purpose of the Study:
- To characterize oocyte and follicular differentiation in GDF-9 deficient mice across different ages.
- To investigate the cellular and ultrastructural changes associated with GDF-9 deficiency.
Main Methods:
- Cell culture techniques.
- Fluorescence microscopy.
- Confocal microscopy.
- Electron microscopy (EM).
Main Results:
- GDF-9 deficient oocytes showed accelerated growth but arrested follicle development at the type 3b stage.
- Oocytes from mutant mice reached advanced differentiation stages and could resume meiosis, with peak completion at 6 weeks.
- Ultrastructural analysis revealed perinuclear organelle aggregation, altered Golgi complexes, absent cortical granules, and abnormal granulosa cell-oocyte interactions.
Conclusions:
- GDF-9 is essential for regulating preantral follicle growth.
- Bidirectional somatic and germ cell interactions, mediated by GDF-9, are critical for maintaining oocyte viability and proper follicular development.