BOVINE PARTHENOGENESIS IS CHARACTERIZED BY ABNORMAL CHROMOSOMAL COMPLEMENTS - IMPLICATIONS FOR MATERNAL AND PATERNAL CO-DEPENDENCE DURING EARLY BOVINE DEVELOPMENT

The present study was conducted to examine the karyotypes of parthenog enetic bovine embryos arising from the application of standard oocyte activation and diploidization methods. Bovine cumulus-oocyte complexes were collected and matured in vitro For 24 hr prior to oocyte activat ion with either 5 mu M ionomycin or 7% ethanol for 5 min. Groups of ac tivated oocytes were further treated with 5 mu g/ml cytochalasin D or 1.9 mM 6-dimethylaminopurine (DMAP) for 6 hr. Cleavage varied signific antly (P < .05) among the treatment groups with 68.0% of the ethanol- and DMAP-treated oocytes dividing. Blastocyst development did not vary with 18.4 +/- 2.5% of all treated oocytes progressing to this stage. Blastocyst development did not occur in groups subjected to oocyte act ivation alone. Blastocysts displayed haploid (2.3%), diploid (11.4%), tetraploid (40.9%), octaploid (4.5%), and mixoploid chromosomal comple ments (40.9%). Two-cell stage parthenogenotes resulting from ethanol o r ionomycin treatment alone displayed haploid (66.7%), diploid (16.7%) , tetraploid (4.2%), and mixoploid (12.5%) complements. Our results de monstrate that diploid bovine parthenogenotes arising from these proce dures are a minority, with the majority of parthenogenotes displaying polyploid and mixoploid chromosomal complements. The events contributi ng to these abnormal chromosomal complements occur as early as complet ion of the first cell cycle, possibly linking these events with the ab sence of a paternally supplied centrosome. (C) 1997 Wiley-Liss, Inc.