P20. Tracing blastomere fate decisions

Abstract

Our objective is to study lineage-specific gene expression of embryonic blastomeres after inhibition of cell-cell interaction. Intact, manually separated blastomeres from wild type and maternal knockout E-cadherin+/− two- to eight-cell stage mouse embryos were used. (Maternal knockout E-cadherin+/− blastomeres do not adhere to each other until after the eight-cell stage.) Individual blastomeres were cultured in vitro, after manual separation or after individual cell separation following each blastomere division. At 10 h of separation, embryos from which each blastomere survived (full set) were collected for gene expression analysis using high-throughput single-cell qPCR designed for both ICM (Oct-4, Sox2 and Sall4) and TE (Cdx2, Eomes and Borg5) lineage-specific marker. Significant up-regulation of TE lineage markers, Borg5 and Cdx2, was found in both separated and maternally deleted E-cadherin+/− blastomeres starting at the eight-cell stage, whereas no significant difference was found in ICM-lineage marker expression. These results indicate that without cell–cell interaction, single blastomeres preferentially express TE markers, suggesting that cell interaction among blastomeres is required for correct lineage decision.