Sexual dimorphism during early bovine embryo development
(2016)
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- Authors
- Supervisors
- Donnay, Isabelle
- Abstract
- Differences between male and female preimplantation bovine embryos have been reported and concern numerous aspects as kinetics of development, cell number or metabolism. These differences are less or more obvious depending on the culture medium embryos are grown in and seem related to the expression of genes on both X chromosomes in female embryos at the blastocyst stage. This transcriptional sexual dimorphism can result in functional consequences and contribute to the differential ability of each sex to cope with its environment. This may in turn alter the sex ratio if embryo survival varies between sexes. We here evaluated developmental and apoptotic rates of in vitro produced male and female bovine embryos in two culture media, one containing fetal calf serum (FCS) and one containing bovine serum albumin (BSA). The levels of apoptosis were assessed in blastocysts collected 7 days after insemination (Day 7 pi) using simultaneously two staining techniques on the same embryos. Analysis by confocal microscopy and subsequent 3D reconstruction allowed a precise cell count and localization of apoptotic cells. Higher levels of apoptotic cells were observed in female embryos whatever the culture condition, but with a more pronounced difference in FCS medium. The sex effect on apoptosis was detected in both the inner cell mass and the trophectoderm and was more important in embryos of small size grown in presence of FCS. However, the higher level of apoptosis among female blastocysts at Day 7 pi did not result in a preferential degeneration of female embryos one day later since no shift in sex ratio was observed at Day 8 pi. In conclusion, female embryos are more prone to apoptosis than male ones. Moreover, culture conditions and embryonic size seem to affect the difference between sexes.
- Affiliations
Citations
Ghys, E. (2016). Sexual dimorphism during early bovine embryo development. https://hdl.handle.net/2078.5/186333