Overexpression of trophoblast stem cell-enriched microRNAs promote trophoblast fate in embryonic stem cells.

The role of microRNAs (miRNA) in first cell fate choice of the preimplantation mouse embryo remains unresolved, as gene expression and knockout data are conflicting. This cell fate choice generates the extraembryonic lineage of the trophoblast and the embryonic lineage of the epiblast (inner cell mass). The trophoblast differentiates into polar and mural cells, where polar cells contribute to placental development and mural cells to the implantation process and Reicherts membrane. The inner cell mass further differentiates into the epiblast and primitive endoderm. We used stem cell lines that can be derived from the trophoblast and epiblast lineages to address the role of miRNAs in early lineage cell fate specification and determination. Using embryonic stem cells (ESC) and trophoblast stem cells (TSC) as starting and ending states of cell development we identified a network of TSC expressed miRNAs that are enriched in ESC targets mRNA. We used constitutive and inducible expression of TSC enriched miRNAs in ESC and show that they can drive cell morphology and gene expression profiles similar to trophoblast. Additionally we show that this process required HDAC2 inhibition and is miRNA specific, as cardiac specific miR-1 could not induce trophoblast under these conditions. In contrast to embryo derived and Cdx2 induced trophoblast cells, miRNAs promote a mural TE like cell phenotype. Transplantation into preimplantation mouse embryos showed that miRNA-induced trophoblast preferentially contributes to the mural trophoblast in both the blastocyst and the Reicherts membrane. Our data support a role for miRNAs and HDACs in the specification of the trophoblast and potentially the polar and mural cell types.

9

Nosi U, Lanner F, Huang T, Cox B