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Chromosomal constitution of mouse blastocysts derived from oocytes inseminated by multiple sperm insertion into the
E Macas1, M Rosselli, B Imthurn
1Department of Gynaecology and Obstetrics, University Hospital, Zurich, Switzerland.
Purpose:
Our purpose was to evaluate the rate of chromosomal aberrations in mouse blastocysts obtained after microinjection of multiple spermatozoa under the zona pellucida of mature oocytes. Without detecting the appearance of pronuclei, the microinjected mouse oocytes containing two polar bodies were cultivated to the blastocyst stage and then analyzed cytogenetically.
Results:
A chromosome study was carried out in a total of 109 blastocysts derived after microinjection of motile spermatozoa into the perivitelline space. Fifty-five blastocysts (50.5%) exhibited normal diploid chromosome complements, 30 (27.5%) showed different forms of mosaicism, and 24 (22%) exhibited haploidy caused by parthenogenetic activation. Compared to in vivo and in vitro control groups there was a significant increase in the parthenogenesis and mosaic forms of embryos produced by micromanipulation (P < 0.001). A total of 360 well-spread metaphases of 103 blastocysts was analyzed to determine whether the micromanipulation procedure increased the chance of aneuploidy. Aneuploid numbers of chromosomes were absent in all the metaphases analyzed.
Conclusion:
Mosaicism and parthenogenesis appear to be increased significantly following microinjection of multiple spermatozoa under the zona pellucida of mouse oocytes, and there was no evidence of aneuploidy.
Insights
Microinjection of multiple sperm into mouse oocytes significantly increases embryo mosaicism and parthenogenesis. However, this assisted reproductive technique did not lead to aneuploidy in the resulting blastocysts.
Area of Science:
- Reproductive Biology
- Developmental Biology
- Genetics
Background:
- Assisted reproductive technologies (ART) aim to improve fertilization outcomes.
- Understanding chromosomal integrity is crucial for ART success and developmental potential.
Purpose of the Study:
- To assess chromosomal aberration rates in mouse blastocysts after microinjection of multiple spermatozoa.
- To evaluate the impact of this specific micromanipulation technique on embryonic development and genetic stability.
Main Methods:
- Mouse oocytes were microinjected with multiple spermatozoa under the zona pellucida.
- Oocytes were cultured to the blastocyst stage without pronuclear observation.
- Cytogenetic analysis was performed on resulting blastocysts to determine chromosome complements.
Main Results:
- Of 109 analyzed blastocysts, 50.5% had normal diploid chromosomes, 27.5% showed mosaicism, and 22% exhibited haploidy due to parthenogenesis.
- Compared to controls, micromanipulation significantly increased parthenogenesis and mosaicism (P < 0.001).
- No aneuploidy was detected in 360 analyzed metaphases from 103 blastocysts.
Conclusions:
- Microinjection of multiple spermatozoa under the zona pellucida significantly elevates mosaicism and parthenogenesis rates in mouse embryos.
- The micromanipulation procedure, as performed, did not induce aneuploidy in the analyzed blastocysts.