The Expression And Regulation Of Tissue Factor (TF)during Human Embryonic Stem Cell Differentiation

Human embryonic stem cells (hESCs) are pluripotent stem cells that can differentiate into virtually all types of adult cell. The one of the most promising stem cell sources can be used for many thus far incurable diseases, such as tissue repair and neurodegenerative diseases. Thus, hESC, thanks to its pluripotency, could be used as a cell model to investigate the differential expression of TF during cell differentiation.Tissue factor (TF), a47KD transmembrane glycoprotein, plays a pivotal role in coagulation by functioning as a receptor for FII/FIIa. Recently, it has also been implicated in biological processes as diverse as tumor angiogenesis, inflammation, atherosclerosis and embryonic development, especially in homeostasis. However, the precise mechanisms by which TF exerts pleiotropic effects remain to be fully understood.microRNAs (miRNAs) are small RNA molecules, about17-23nucleotides in length, and act as translational regulators of their target genes at the post-transcriptional level. miRNAs play a pivotal role in embryogenesis and development. The principal mechanism of miRNA regulation of gene expression is through the formation of miRNA-RNA-induced silencing complex in the cytoplasm, which binds to the3’-untranslated region (3’-UTR) of target transcripts and thereby leads to repression of protein translation or destabilization of mRNAs.Given that miRNAs post-transcriptionally regulate protein expression, we hypothesized that miRNA may determine the differential expression pattern of TF during hESCs differentiation into hematopoietic and trophoblasts. Bioinformatics analysis has suggested that there are miRNA-binding sites for miR-19, miR-20, and miR-106in3’-UTR-S (sense orientation) of the TF transcript. It has been demonstrated that TF expression is regulated by miR-19in breast cancer cells. Nevertheless, miRNA regulation of TF expression has not yet been examined in any model system of cell development.Akt and Erkl/2pathways are involved in many important physiological or pathophysiological processes, including development, cell proliferation, stress resistance, and tumor pathogenesis. Accumulating evidence suggests that TF expression is modulated by Akt or Erkl/2pathways in adult cells. However, it is still unclear whether Akt-or Erkl/2-mediated regulation of TF expression serves as the mechanistic basis for TF differential expression during differentiation.The present study attempted to investigate the differential expression of TF during hESCs differentiation by measuring TF levels in trophoblasts, in stem cells, including hESCs and hematopoietic stem/progenitor cells (HSPCs), and in adult mature cells, including G-M cells and erythrocytes. We also explored the potential mechanisms behind TF differential expression during differentiation by interrogating the role of miRNAs and Erkl/2pathways.