28 January 2011
Chinese scientists have developed a much easier way to make the short strands of RNA that are an essential tool in understanding what genes do.
Short interfering ribonucleic acids (siRNAs) were first discovered in 1999, and found to interfere with the expression of specific genes, giving them a key role in controlling the molecular machinery in living organisms. Though initially identified in plants, they were later found in animals too, and this spurred an interest in using them as tools to investigate what specific genes do in the body.
One type of siRNAs, endoribonuclease-prepared siRNAs (esiRNAs), has recently attracted attention because of their greater specificity and their cost effectiveness. Jianzhong Xi and colleagues at Peking University have now demonstrated a lab on a chip method that makes large scale manufacture of esiRNAs much easier.
The chip consists of 96 pins. Each pin has a polymer bead at its end in which a number of DNA probes are immobilised, allowing hundreds of esiRNA products to be manipulated at the same time
siRNAs are RNA strands of 20-25 nucleotides long, making them straightforward to prepare by standard synthetic chemistry. However, the same cannot be said for esiRNAs, since these are mixtures of compounds prepared by enzymatic digestion - breakdown of food. The manufacture of esiRNA, says Xi, is 'a complex process, consisting of at least six steps, which require expensive instruments as well as demanding skills.'
Xi's work uses a novel chip consisting of an array of pins with polymer microbeads at one end, on which are fixed the pieces of DNA that are the starting point for the synthesis. Unlike the conventional multistep liquid manufacture method, this chip allows the simultaneous manipulation of hundreds of esiRNA products, 'significantly simplifying the manufacture process,' says Xi. Crucially, he adds, the amplification (copying a gene) and transcription (creating an RNA sequence from DNA) reactions involved in the production process occur without any effect from the polymer beads.
Frank Buchholz, professor of medical systems biology at the Technical University of Dresden, Germany, says 'the work by Xi demonstrates the superior performance of the esiRNA technology, and promises to improve the synthesis of these important reagents.'
Xi concludes that this 'simple and robust' method of manufacture 'promises both more intensive and extensive applications of esiRNAs.'