Human embryonic stem cells (hESCs) are cells which are capable of self-renewal and can be differentiated into all the cell types in the body, and this makes the hESCs to make use in stem cell therapy, drug discovery, and developmental studies. To utilize the hESCs, it is important to discover differentiation mechanisms and method for efficient differentiation. There are many possible regulation mechanisms on differentiation, and microRNAs are highlighted in these days.
MicroRNAs regulate gene expression by post-transcription mechanism, and regulate mRNA translation in animal cells, and play key roles in cellular differentiation. Like mRNAs, microRNAs are transcribed by RNA polymerase II, and processed by Drosha and Dicer. Mature microRNAs bind to 3’UTR of target mRNA and repress translation.
This study demonstrates the differential expression pattern of microRNAs and mRNAs during the differentiation of hESCs into hESC-derived definitive endoderm (DE) cells, DE cells-derived hepatocytes, hESC-derived CD34 positive cells, and CD34 positive cells-derived endothelial cells. The two lineages show differential expressions of mRNAs and microRNAs related to cytoskeleton and cell-adhesion. Endothelial cells make clustered cells, such as hepatocytes and gut-lining cells, and CD34 positive cells make dispersed cells such as blood cells. In this view, the different expression pattern of mRNAs and microRNAs seems biologically relevant.
Among microRNAs which show dramatic changes during hepatic differentiation, miR-21, miR-214, and miR-216a which are negative regulators of PTEN were enriched in hESC-derived hepatocytes. PI3K pathway is activated by extracellular signal, and PI3K phosphorylates $PIP_2$ into $PIP_3$, and PIP3 recruits many proteins which has PH domain to the membrane, and transmits signal to the downstream. PTEN de-phosphorylates $PIP_3$ to $PIP_2$, antagonizing the entire signaling pathway. As mRNAs related to focal adhesion and cytoskeleton are highly exp...