Mammalian parthenogenetic cell lines display abnormal chromosome complements and aberrant centriole number

Mature oocytes can be activated in vitro leading to the generation of pluripotent cells that show the standard features associated with their biparental counterpart. However many aspects still need to be elucidated and, in particular little attention has been addressed so far to the incidence of aneuploidy in these cells. In mammals, with the possible exception of mouse, the lack of the paternal contribution to the parthenote centrosome is considered as the most likely cause of aneuploidy. In this study we analysed the rate of aneuploidy and centriole distribution (as a marker of centrosome anomalies) in cell lines derived from pig and sheep parthenotes and in sheep parthenotes foetus that reached their maximum development in vivo (27 days). Centriole number and distribution was assessed both by immunocytochemical analysis and with ultrastructural evaluation. Karyotyping was performed on mitotically active cells. Chromosomes spreads were evaluated and processed using the Leica CW4000 Karyo software. The results obtained indicate that cell lines of parthenogenetic origin have, in all examined cases, an incidence of aneuploidy significantly higher than that of their respective controls with the majority of the cells displaying an hypo-haploid and hypo-diploid set up, possibly related to a loss of chromosomes during the mitotic process. A higher incidence of multiple centrioles was also detected, suggesting the hypothesis that aneuploidy may be related to the lack of paternal contribution that results in abnormal centrosome formation, incorrect control of the process of spindle rearrangement and consequent chromosomes malsegregation. Abnormal segregation and multicentriolar distribution was not limited to cell lines but was observed in parthenogenetic foetus, indicating that culture artifacts are unlikely to be the cause.