Abstract
Blastomere fate and embryonic genome activation (EGA) during human embryonic development are unsolved areas of high scientific and clinical interest. Forty-nine blastomeres from 5- to 8-cell human embryos have been investigated following an efficient single-cell cDNA amplification protocol to provide a template for high-density microarray analysis. The previously described markers, characteristic of Inner Cell Mass (ICM) (n = 120), stemness (n = 190) and Trophectoderm (TE) (n = 45), were analyzed, and a housekeeping pattern of 46 genes was established. All the human blastomeres from the 5- to 8-cell stage embryo displayed a common gene expression pattern corresponding to ICM markers (e.g., DDX3, FOXD3, LEFTY1, MYC, NANOG, POU5F1), stemness (e.g., POU5F1, DNMT3B, GABRB3, SOX2, ZFP42, TERT), and TE markers (e.g., GATA6, EOMES, CDX2, LHCGR). The EGA profile was also investigated between the 5-6- and 8-cell stage embryos, and compared to the blastocyst stage. Known genes (n = 92) such as depleted maternal transcripts (e.g., CCNA1, CCNB1, DPPA2) and embryo-specific activation (e.g., POU5F1, CDH1, DPPA4), as well as novel genes, were confirmed. In summary, the global single-cell cDNA amplification microarray analysis of the 5- to 8-cell stage human embryos reveals that blastomere fate is not committed to ICM or TE. Finally, new EGA features in human embryogenesis are presented.
Highlights
Embryonic developmental fate can be described as a progressive loss of totipotency, whose primary outcome is commitment and differentiation into inner cell mass (ICM) and trophoectoderm (TE) [1,2]
2-cell blastomeres do not differ and their precise contribution to Inner Cell Mass (ICM) and/or TE cannot be anticipated at this early stage, but later in the morula stage when inner cells contribute to ICM, whereas outside cells differentiate into TE [12,13,14,15,16,17]
Understanding human preimplantation development from a global genome perspective is crucial for basic embryology research, regenerative medicine because of the derivation of human embryonic stem cells from single blastomeres
Summary
Embryonic developmental fate can be described as a progressive loss of totipotency, whose primary outcome is commitment and differentiation into inner cell mass (ICM) and trophoectoderm (TE) [1,2]. The second model stresses that the mouse embryo is entirely symmetric, and that it neither, has an AV nor shows any other pre-patterning According to this view, 2-cell blastomeres do not differ and their precise contribution to ICM and/or TE cannot be anticipated at this early stage, but later in the morula stage when inner cells contribute to ICM, whereas outside cells differentiate into TE [12,13,14,15,16,17]. We use the term ‘‘gene’’ instead of ‘‘gene feature’’ in the microarray data descriptions
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