新的即時成像、非侵入性細胞標記技術  發現

 2 細胞階段胚胎只有只有其中一個細胞

會演化成80% 胚胎主體 未來的外胚層  內胚層（卵黃囊）和滋養外胚層（胎盤）

 Labeling and live imaging of human embryos reveal that the majority of the future body originates, mostly, from one of the 2-cell stage blastomeres. Descendants of the first 2-cell stage blastomere to divide contribute more asymmetric divisions at the 8-cell stage, which generate the small number of founding epiblast cells before implantation. 

https://www.cell.com/action/showPdf?pii=S0092-8674%2824%2900455-0

The first two blastomeres contribute unequally to the human embryo  

https://doi.org/10.1016/j.cell.2024.04.029 

SUMMARY 

Retrospective lineage reconstruction of humans predicts that dramatic clonal imbalances in the body can be traced to the 2-cell stage embryo. However, whether and how such clonal asymmetries arise in the embryo is unclear. Here, we performed prospective lineage tracing of human embryos using live imaging, non-invasive cell labeling, and computational predictions to determine the contribution of each 2-cell stage blastomere to the epiblast (body), hypoblast (yolk sac), and trophectoderm (placenta). We show that the majority of epiblast cells originate from only one blastomere of the 2-cell stage embryo. We observe that only one to three cells become internalized at the 8-to-16-cell stage transition. Moreover, these internalized cells are more frequently derived from the first cell to divide at the 2-cell stage. We propose that cell division dynamics and a cell internalization bottleneck in the early embryo establish asymmetry in the clonal composition of the future human body.