Human Reproduction, Vol. 16, No. 11, 2362-2367,
November 2001
© 2001 European Society of Human Reproduction and Embryology
Cytogenetic analysis of human zygotes displaying three pronuclei and one polar body after intracytoplasmic sperm injection*
1 Department of Gynecology and Obstetrics, University of Ulm, Prittwitzstrasse 43, D-89075 Ulm and 2 Gregor Mendel Laboratories, 89231 Neu-Ulm, Germany
BACKGROUND: Digynic zygotes with three pronuclei and one polar body obtained after intracytoplasmic sperm injection (ICSI) were studied cytogenetically to elucidate the frequency and origin of chromosomal abnormalities at the earliest stage of conception. METHODS: Uncleaved, single-cell zygotes were incubated with podophyllotoxin and vinblastine and fixed by a gradual fixation air drying method. The chromosomes were stained with Giemsa. RESULTS: Twenty-two (50%) out of 44 informative zygotes revealed cytogenetic alterations, including aneuploidy (six cells, 13.6%), structural aberrations (10 cells, 22.7%) and combinations of numerical and structural abnormalities (two cells, 4.5%). In one case (2.3%), double aneuploidy or an effect of chromosomal translocation could not be distinguished and one zygote (2.3%) turned out tetraploid due to injection of a diploid spermatozoon. Two zygotes (4.5%) showed an irregular chromatid segregation between the two maternal complements. In completely analysable cells, the sex chromosome ratio XXX:XXY was 17:15. CONCLUSIONS: Digynic ICSI zygotes carry a high rate of cytogenetic abnormalities that obviously have been transmitted by the participating oocytes and spermatozoa. We also confirmed the previously reported, possibly ICSI-induced irregular oocyte chromatid segregation. The results suggest that aneuploidy in the oocytes must have been caused by predivision instead of non-disjunction.
Key words: chromosomal abnormalities/digynic triploidy/ICSI/irregular chromatid segregation/tripronuclear zygotes
* The results of this study have been presented in part at the 16th Annual Meeting of ESHRE, Bologna, Italy, 2000.
3 To whom correspondence should be addressed. E-mail: bernd.rosenbusch{at}medizin.uni-ulm.de
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