Submission Number: KEE-4-1-1

Abstract Number: 241

ANEUPLOIDY BUT NOT MATERNAL IMPRINTING ASSOCIATED DEVELOPMENTAL ARREST AND APOPTOSIS IN MOUSE PREIMPLANTATION EMBRYOS.

David L Keefe* ^1,2 and L Liu* ^1,2

Department of Ob/Gyn, Women and Infants Hospital, Brown University, Providence, RI 02905 ¹
Marine Biological Laboratory, Woods Hole, MA 02543, USA ²

Abstract:
Aneuploidy is frequently encountered in human preimplantation embryos. We generated haploid and diploid parthenotes using mice as a model, then compared their subsequent development to normal, IVF embryos. Strontium in calcium-free medium activated mouse oocytes, led to extrusion of a second polar body and formation of a single pronucleus, and thus produced haploid parthenotes. Strontium plus cytochalasin D activated oocytes and led to the formation of two pronuclei, without second polar body extrusion, thus producing diploid parthenotes. Oocytes could not be activated by strontium in KSOM containing calcium. IVF of MII oocytes was performed in TYH medium and embryos were cultured in KSOM. Twenty-four hours after activation or IVF, rates of cleavage did not differ among haploid (91%) or diploid parthenotes (98%) and IVF embryos (92%). At 76 h, 77% of haploid parthenotes were at the morula stage, whereas 87% of diploid parthenotes and 86% of IVF embryos had developed to blastocysts. The cell number in the haploid parthenotes (27 8) was significantly (P<0.001) less than that of diploid parthenotes (39 9). By 96 h, degeneration of haploid morula was obvious, whereas blastocysts from IVF and diploid parthenotes had expanded or were hatching. The total cell number (40 18) in the haploid morula was significantly lower than that in diploid parthenotes (108 19) and IVF blastocysts (101 17). However, the percentage of apoptotic cells (16%) in the haploid morula was significantly higher than that in diploid parthenotes (3%) and IVF blastocysts (6%). The number of total and apoptotic cells was not different between the diploid parthenotes and IVF blastocysts. Diploid parthenotes developed as well as IVF embryos, at least during preimplantation stages, demonstrating the effective parthenogenetic activation triggered by strontium. It is suggested that haploid embryos arrested developmentally, then progressed to apoptosis and that neither maternal nor paternal imprinting affected development during the preimplantation stages.

Keywords: ploidy, apoptosis, embryo, mouse

This abstract is being presented at: 2:45 PM in session:
SESSION 11: APOPTOSIS IN REPRODUCTIVE BIOLOGY