Highlights

Driving differentiation

14 Sep 2010

Mysterious molecules called lncRNA direct the fate of stem cells in the early mouse embryo

The vast therapeutic potential of stem cells is driving intensive research into the factors that control their differentiation.

The vast therapeutic potential of stem cells is driving intensive research into the factors that control their differentiation.

© iStockphoto/luismmolina

Embryonic stem cells (ESCs) are self-renewing cells that retain the ability to differentiate into any of the cell types that make up the body, a property known as pluripotency. ESCs have enormous therapeutic potential, and researchers are intensively studying the factors that control their differentiation.

Molecules called long, non-coding RNA (lncRNA) have recently been recognized by molecular biologists to be an important class of gene expression regulators. A team led by researchers from the A*STAR Genome Institute of Singapore (GIS) have now shown that lncRNA plays an important role in maintaining ESC pluripotency.

The lncRNA project, headed by former GIS scientist Leonard Lipovich and continued at the GIS by Paul Robson and Jameelah Sheik Mohamed, involved computational analysis of the entire mouse genome, leading to the identification of four genes encoding lncRNA that are expressed in mouse ESCs (mESCs). The researchers found the genes located close to DNA sequences that are recognized by the proteins Nanog and Oct4, which are known to keep ESCs in the pluripotent state by activating specific target genes.

The researchers then tested whether or not the lncRNA expression patterns correlated with pluripotency. First, they used a well-characterized method to induce mESCs to differentiate into ectoderm, cells that ultimately form the skin and nervous system. This led to a reduction in expression of Oct4 and Nanog, as expected, but also led to a significant decrease in expression of the genes encoding the four newly identified lncRNAs.

Lipovich and his co-workers then used RNA inhibition to block the synthesis of Oct4 and Nanog proteins in undifferentiated mESCs leading to differentiation. This also affected lncRNA expression. Blocking Oct4 significantly reduced expression of two of the lncRNAs, while blocking Nanog led to significant up-regulation of a third.

To functionally test these lncRNAs for their role in pluripotency, the team used RNA inhibition to block expression of the lncRNAs directly. They  found that this too promoted loss of pluripotency in mESCs. Loss of one of the lncRNAs was found to markedly reduce mESC division, while loss of another also caused morphological changes characteristic of differentiation.

Finally, the researchers found that over-expressing these lncRNAs in undifferentiated ESCs promotes differentiation along either the ectodermal or endodermal pathways by inducing expression of a specific set of genes.

These results demonstrate for the first time that lncRNAs are necessary for mESC pluripotency — and pluripotency of ESCs of other species, including humans — and that their expression is regulated by Oct4 and Nanog. “The next step would be to elucidate the mechanisms by which these molecules act to control gene expression,” says Mohamed.

The A*STAR-affiliated researchers contributing to this research are from the Genome Institute of Singapore.

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References

Mohamed, J.S., Gaughwin, P.M., Lim, B., Robson, P. & Lipovich, L. Conserved long noncoding RNAs transcriptionally regulated by Oct4 and Nanog modulate pluripotency in mouse embryonic stem cells. RNA 16, 324–337 (2010). | article

This article was made for A*STAR Research by Nature Research Custom Media, part of Springer Nature