Many promising new therapies fail because of unwanted side effects. These are the collateral damage of the war on disease. For the increasingly promising field of gene therapy, which is now making spectacular progress, specificity is critical. An ideal gene therapy will only impact the target gene in a specific sub-population of cells. SINEUP, a new and exciting technology published in Nature, was developed by the labs of Prof. Stefano Gustinich at SISSA in Trieste, Italy and Dr. Piero Carninci at RIKEN in Yokohama, Japan. It exerts its effect on mRNA and provides pinpoint accuracy, being targetted to specific genes and only affecting cells in which a target protein is already made. The technique holds promise for treating hundreds of diseases caused by abnormally low protein levels. Haploinsufficiency disorders are prime targets for SINEUP, but conditions such as Parkinson's Disease in which reduced expression of specific proteins have been identified may also benefit. In addition, the SINEUP system offers a powerful new tool for basic research and bioproduction.
Today, Cell Guidance Systems, in partnership with TransSine Technologies, has launched a SINEUP kit which allows researchers to simply, routinely and specifically "Knock-up" or boost the levels of specific proteins. The kit is composed of a plasmid vector containing a SINEUP element and positive control constructs for eGFP. The researcher can specify which mRNA is targetted simply by inserting a small DNA sequence, complementary to the mRNA, into the construct. The construct is then transfected into cells and the SINEUP targets pre-existing mRNA (or mRNA from a co-transfected gene) for increased translation by recruiting ribosomes. Importantly, if the mRNA is not present, there is no effect. So the effect on adjacent cells can be completely different if one cell has mRNA and the other does not. This level of specificity is a key differentiator compared with alternative protein expression technologies.
Dr. Michael Jones, CEO of Cell Guidance Systems commented: "This is a very powerful technology. The launch of the SINEUP kit now brings it within easy reach of any scientist utilizing standard cloning techniques. As well as developing new therapies for disease, the technique can be used to dissect protein function and boost bioproduction."
Why is this important?
The human cell has around 20,000 different protein-encoding genes embedded along 23 chromosomes. Essentially the same set of chromosomes is present in every normal cell. The activity of these genes in each cell is orchestrated in a precise spatiotemporal manner to maintain our bodies in a healthy state. The information from individual genes is first transcribed into mRNA which is then read and translated by ribosomes to produce the proteins. Each of these steps (gene to mRNA to protein) can impact protein production.
When this system goes awry, disease may result. Correcting the protein production process or supplementing the protein can provide an effective therapy. Insulin therapy to treat diabetes is an example of this. However, simply injecting a protein is not possible if the protein needs to be more precisely controlled to prevent side effects. Over the last few decades, scientists have developed a range of techniques to engineer the protein production system. For example, a gene can be directly modified using "gene editing" techniques such as CRISPR/Cas9. However, the problem with gene editing, as with protein injections, is that it is difficult to confine activity to particular cells.
mRNA is a much more attractive target because it provides a level of specificity that is impossible to achieve with gene editing. The siRNA technique has been used for almost 20 years to disrupt mRNA, leading to a reduced amount of the protein it encodes. The converse of siRNA which "knocks-down" a gene, is a therapy that "knocks-up" or boosts the activity of mRNA, but before SINEUP, this has ability been lacking. SINEUP works by targetting specific mRNAs and promoting increased efficiency of protein production by recruiting more ribosomes. Increases in protein levels of as much as 10-fold have been achieved, with typical results between 2 to 4-fold. For many diseases, this relatively small increase is critical and significant changes in cell phenotype can then be detected.