Zytogenetische Analyse von Zygoten mit drei Vorkernen nach partieller Zona dissection (PZD) der Eizellen

Abstract

Objective : Tripronuclear zygotes obtained after partial zona dissection (PZD) of the oocytes were analysed cytogenetically to determine the rate of chromosomal abnormalities and to allow a comparison with previously published data after conventional IVF. Material and Methods: ollowing incubation in hypotonic solution preparations were made from a total of 28 cells. Chromosomes were stained homogeneously with iemsa. Results: Six cells could not be evaluated whereas another one was characterised by the presence of a normal haploid and two non-interpretable metaphases. Complete karyotypes were established for 21 cells, taking the varying arrangement of the chromosome sets into consideration. Ten zygotes showed three separated haploid metaphases (distribution pattern n/n/n), eight zygotes had one haploid and one diploid chromosome set (n/ 2n) and in three cells the individual sets were not distinguishable (3n). The sex chromosome ratio XXX:XXY:XYY was 7:9:5. Cytogenetic abnormalities were found in eight zygotes including four with numerical and two with structural chromosome alterations. In two cells, aneuploidy and structural aberrations appeared simultaneously. Compared with previously analysed tripronuclear zygotes obtained after conventional IVF, the rate of aberrant zygotes (38.1% vs. 20%) as well as the incidence of aberrant (male + female) chromosome sets (14.1 % vs. 6.7%) were increased after PZD. However, these differences were not significant (probability of error=5%). Conclusion: The transmission of the abnormality could be ascribed to spermatozoa in two cases. The results indicate the need for further investigation of a possibly increased development of chromosomally aberrant zygotes after microinsemination. In addition, more information on the parental origin of the observed aberrations will be necessary.