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Updated: Aug 8, 2026
Culture and Co-Culture of Mouse Ovaries and Ovarian Follicles
Published on: March 17, 2015
Expression of Fas and Fas ligand protein and mRNA in mouse oocytes and embryos
R L Kelkar1, S J Dharma, T D Nandedkar
1National Institute for Research in Reproductive Health, JM Street, Parel, Mumbai-400012, India.
Abstract:
During mammalian embryonic development, abnormal eggs and embryos are eliminated by apoptosis; however, the precise apoptotic pathways remain as yet unidentified. In the present study, expression of Fas and Fas ligand - the proximal members of the death receptor pathway, was evaluated in mouse preimplantation embryos by immunofluorescence and in situ hybridization techniques. Ovulated oocytes were collected from oviducts of cyclic mice on the day of oestrus (day 0), and one-cell, two-cell embryos and eight-cell morulae were collected from oviducts of mated animals on days 1, 2 and 3 of pregnancy, respectively. Blastocysts were flushed from the uterine horns on day 4. Expression of Fas and Fas L mRNAs and proteins was absent from embryos at days 0, 1 and 2. A marked increase in Fas and Fas L mRNA and protein expression was detected in all morphologically normal embryos on day 3 and day 4. In addition, embryos on days 3 and 4 were positive for terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) staining; however, absence of caspase 8 and 3 and intense localization of proliferating cell nuclear antigen confirmed the proliferative status of these embryos. Furthermore, TUNEL staining was absent in postimplantation embryonic sections obtained on day 6. The results of the present studies thus indicate an equilibrium between proliferation and apoptosis in the preimplantation embryo.
Insights
Apoptosis eliminates abnormal mammalian embryos. Fas and Fas ligand expression increases in preimplantation embryos on days 3 and 4, indicating a balance between proliferation and programmed cell death.
Area of Science:
- Developmental Biology
- Cell Biology
- Reproductive Biology
Background:
- Apoptosis (programmed cell death) is crucial for eliminating abnormal cells during mammalian embryonic development.
- The specific apoptotic pathways involved in preimplantation embryonic development remain largely unidentified.
Purpose of the Study:
- To investigate the expression of Fas and Fas ligand, key components of the death receptor pathway, in mouse preimplantation embryos.
- To determine the role of these molecules in regulating apoptosis during early embryonic development.
Main Methods:
- Immunofluorescence and in situ hybridization were used to detect Fas and Fas ligand mRNA and protein expression.
- Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) staining assessed apoptosis.
- Immunohistochemistry identified proliferating cell nuclear antigen and caspases 8 and 3.
Main Results:
- Fas and Fas ligand mRNA and protein were absent in mouse oocytes and embryos on days 0-2 of development.
- A significant increase in Fas and Fas ligand expression was observed in morphologically normal embryos on days 3 and 4.
- TUNEL staining was positive in day 3 and 4 embryos, but the absence of caspase 8/3 and presence of proliferating cell nuclear antigen indicated continued proliferation.
Conclusions:
- Fas and Fas ligand are expressed in mouse preimplantation embryos during a critical window of development (days 3-4).
- These findings suggest an equilibrium between proliferation and apoptosis in the preimplantation embryo, potentially involving the Fas pathway.
- Further research is needed to fully elucidate the precise apoptotic mechanisms governing early mammalian development.
