The Leading Blastomere of the 2-Cell Stage Parthenogenetic Porcine Embryo Contributes to the Abembryonic Part First

Roh S *,


Objective: Here in we investigated the embryonic-abembryonic axis of the blastocyst in the porcine species. To avoid the influences of the fertilization cone which indicates the sperm entry position and to prevent topological change of the two or more apposing pronuclei in the egg center caused by polyspermy after IVF we chose porcine parthenogenetic embryos for use in the present study even though they may not represent normal embryonic development in the pig. Here in we describe the fate of an individual blastomere from a 2-cell-stage parthenogenetic porcine embryo. Materials and Methods: For lineage tracing DiI a fluorescence dye was injected into only a blastomere of the 2-cell stage parthenogenetic porcine embryos. If the first blastomere to divide was labeled the embryo was included in the leading group and while all others were included in the lagging group. Mitochondrial distribution of 2-cell parthenotes was also examined by using MitoTracker Green staining and confocal system. Results: In 60.5% of the blastocysts in the lagging group the progeny of the labeled blastomeres formed the inner cell mass (ICM) and adjacent trophectoderm (TE) hemisphere; 62.1% of the blastocysts in the leading group had progeny of the labeled blastomeres distributed only to the TE (opposite of ICM). The rest of the lagging and leading groups showed random distributions. Unlike murine parthenotes biased mitochondrial distribution was also found in porcine parthenotes (38.1%). Conclusion: Our findings indicate that the ‘leading’ blastomere of the 2-cell porcine parthenote forms the distal TE (abembryonic) and that the ‘lagging’ blastomere forms the remaining portion of the blastocyst including the ICM (embryonic). Biased distribution of mitochondria in each 2-cell blastomere may contribute partly to this event. This study was supported by Korea Science and Engineering Foundation (KOSEF) grants funded by the Government of the Republic of Korea (MOST; M10641000001-06N4100-00110 and R01-2007-000-10316-0).