Gene Silencing

Gene Silencing or RNAi has been described as the most important scientific advance of the last decade. Proponents of the technology say that it will be able to silence the genes that cause HIV, Hepatitis and even cancer. With claims like that there are obviously billions of dollars are at stake. So it comes as something of a surprise that a small Queensland biotechnology company claims to have discovered and patented the most effective technique for silencing genes.

Gene Silencing refers to a technique ,called RNA interference (RNAi), for switching off genes within a cell. It is a technology that was first discovered in the 80's by a Norwegian researcher when he was able to affect the colour of blue Petunias. It has been used in plant research and breeding ever since. It involves introducing a double strand of RNA into a cell, one strand of which is identical to the RNA that is being targeted to be switched off. The cell identifies the double stranded RNA as an intruder (because the cell naturally only produces single stranded RNA) and then destroys it. In the process the target RNA is destroyed, thereby switching off the function of that gene. It is revolutionary technology but has many limitations.

Now, Mick Graham, from a Queensland based biotechnology company called Benitec, claims to have invented an alternative and more efficient way of doing this. It involves introducing a DNA construct into the cell, which then triggers the cell to produce its own double stranded RNA. He claims that this technique overcomes many of the limitations of conventional RNAi.

In plant research, Benitec's DNA based technology has been used to successfully switch off the gene that causes 'blackheart' in pineapples. When a pineapple is put into cold storage or hit by frost an enzyme is released that turns the centre of the pineapple black or brown. It costs the pineapple industry millions of dollars every year. After identifying the gene that causes the enzyme to be released, a DNA construct targeting that gene is fired into pineapple cells using a technique called 'biolistics'. These cells are then cloned and grown up to produce pineapples that have the gene which causes 'blackheart' switched off. The potential applications are enormous.

But the big breakthrough for Benitec is that they now claim to be the first in the world to have successfully switched off a gene in a mammal. 'Betty' is the lab mouse who is living proof of this. Small patches of her black coat pigments were switched off using this technology. The success of this 'proof of concept' experiment gives Benitec a dominant intellectual property position in the field.

They have now turned their attention to human cells and have shown that human breast cancer cells can be switched off in vitro.

The prospects for this technology in developing therapeutic applications for diseases including cancers, autoimmune dysfunctions and viral infections are enormous. Additionally, it can be used as a tool for determining gene function - if you can selectively switch off a gene you can then observe its biological function. Benitec look set to cash in. But only if they can enforce their patent in the fast moving biotechnology industry dominated by giant multinational corporations. It's a big challenge.




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