"These are transient, non-coding molecules that do not incorporate into the genome, but promote self-replication and have the potential to induce pluripotency," Blelloch says. "They do their thing -- turn a somatic cell into an embryonic stem cell-like one -- and then they're gone."
"MicroRNAs give us a new tool to manipulate the fate of cells," Blelloch says.
MicroRNAs are snippets of single-stranded RNA that prevent a gene's code from being translated from messenger RNA into protein. They were debuted in 1993, when scientists reported the discovery of a microRNA in the microscopic roundworm C. elegans. Since then, the field has "exploded," says Blelloch, with hundreds of microRNAs discovered in the last eight years across a broad range of species, from plants to animals.
Produced in the nucleus and released into the cytoplasm, microRNAs home in on messenger RNAs that share part of their genetic sequence. When they find them, they latch on, preventing the messenger RNA from being processed by the protein-making machines known as ribosomes. As such, microRNAs are able to ratchet down a cell's production of a given protein.
Currently, Blelloch and his colleagues are working to replace all four transcription factors with microRNAs and conducting experiments that will reveal the mechanism by which these small molecules are able to induce pluripotency. The team will also be looking to determine which microRNAs might be able to turn adult cells directly into particular adult cell types, by-passing the embryonic stem cell-like stage altogether.
"The goal now is to ensure the safety of induced pluripotent stem cells and to differentiate them into cells that can be used to repair damaged tissue and treat disease," he says.
The study was supported by grants from the National Institutes of Health, California Institute for Regener
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