New Technique for Switching Off Genes

A method has been developed to inactivate selected genes in mice through RNA inhibition. The technique involves injecting mice with DNA that produces an unusual folded RNA in a single, double-stranded molecule. The research was reported in the July 4, 2002, issue of Nature.

"RNA inhibition has been shown to work in lower organisms, but there was some question about whether it would work in mammals,” said Dr. Mark Kay, professor of genetics and pediatrics at Stanford University (Palo Alto, CA, USA) and one of the researchers.

The main problem with RNA inhibition is the rapid rate at which cells destroy injected double-stranded RNA. A more promising approach is to inject suitable DNA, which would continually produce the proper RNA. Usual methods of injecting DNA, however, produce single-stranded RNA, which is useless for inhibition.

Using a type of DNA that produces an unusual form of RNA, which doubles back on itself like a hairpin to make a single, double-stranded molecule, solved the problem. Injecting this DNA into mice resulted in the production of single-stranded, folded RNA that was as effective at inhibiting the target gene as injecting double-stranded RNA. Furthermore, even after the hairpin RNA breaks down, the DNA remains in the cell and continues producing new RNA.

Dr. Kay stated that this initial work is a proof of concept. "The ultimate goal is to use this to treat a disease. We can do this by placing these molecules into standard gene-therapy vectors.”



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