> First, this is NOT about genetic engineering -- these are naturally-occurring sequences.
The use of RNA in therapies requires the synthesis of large quantities of RNA. This RNA is essentially a small segment of code. The scientist writes this code, based upon observed sequences in nature, with the aim of targeting cellular functions. We do *not* use actual naturally occurring RNA, but synthetic RNA. In living organisms RNA is used for thousands or millions of functions, just like words in a language.
To say that these are "naturally occurring sequences" is the same as saying I am using ordinary letters to compose this sentence. The letters have no power by themselves. It is only when they are assembled into meaningful words and sentences do they gain force. As any writer knows, the careful choice of words is what distinguishes a skillful writer from a dolt.
In these experiments, investigators are using RNA to alter cell functions. The results depend entirely on the careful choice of code -- and -- the effect of this code. Here is the rub. We all know that no matter how well we compose our sentences, we can still be completely misunderstood. In fact, there always seems to be somebody who reads something you write and takes it completely the wrong way.
Here we have hit on the real risk of RNA therapy. No matter how careful the investigator is in choosing the sequence, even to the extent of copying "naturally occurring sequences," it cannot be known beforehand how the cell will react to the introduction of that sequence, any more than I can know beforehand how you will react to what I am typing here.
If you are still reading this, let me pull another card from the deck and lay it on the table. Scientists have now learned how to design RNA sequences that can cut the genomes of living organisms and insert specific genetic code, meaning that RNA *can* be used to make permanent changes in the genes of live plants and animals.
"The ability to modify specific elements of an organism's genes has been essential to advance our understanding of biology, including human health," said Jennifer Doudna, UC Berkeley. "However, the techniques for making these modifications in animals and humans have been a huge bottleneck in both research and the development of human therapeutics. This is going to remove a major bottleneck in the field, because it means that essentially anybody can use this kind of genome editing or reprogramming to introduce genetic changes into mammalian or, quite likely, other eukaryotic systems."
"I think this is going to be a real hit," said George Church, Harvard Medical School. "There are going to be a lot of people practicing this method because it is easier and about 100 times more compact than other techniques."
> Precise and efficient genome targeting technologies are needed to enable systematic reverse engineering of causal genetic variations by allowing selective perturbation of individual genetic elements. Here, we report the development of a new class of precision genome engineering tools based on the RNA-guided Cas9 nuclease. The ability to use RNA to program sequence-specific DNA cleavage defines a new class of genome engineering tools. -- Feng Zhang, et al. Broad Institute of MIT and Harvard
> Our versatile RNA-guided genome editing system can be readily adapted to modify other genomic sites by simply modifying the sequence of our gRNA expression vector to match a compatible sequence in the locus of interest. We expect RNA-guided genome targeting to have broad implications for synthetic biology, the direct and multiplexed perturbation of gene networks, and targeted ex vivo and in vivo gene therapy. George M. Church, et al. Harvard Medical School.
http://www.sciencemag.org
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