Flipping the genetic switch: moderating gene therapy doses with the pA regulator
A recent research paper from scientists at the Baylor College of Medicine (TX, USA) outlines a novel gene regulation system called the pA regulator. Its employment of RNA-interacting molecules could revolutionize gene therapies by enabling finer control over their dose.
Gene therapies, like other therapeutics, must be maintained within strict therapeutic windows specific to the patient. Too high an expression of the therapeutic gene could be toxic, while too little could have no effect.
Despite mammalian gene regulation systems being well-understood, their incorporation into human gene therapies is limited by their immunogenicity. This is because the human immune system recognizes the regulatory proteins as foreign and rejects them, rendering the therapy ineffective. As a result, no such systems have been approved by the US FDA or other regulatory agencies.
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A recent research paper by Laising Yen and his team reports the use of small RNA-interacting molecules that act like a switch, called the pA regulator, to turn the expression of a gene ‘on’ or ‘off’. Its use in place of immunogenic regulatory proteins could regulate FDA-specification gene therapy doses without adverse immune system reactions.
The researchers engineered the pA regulator into the RNA molecule that is produced by the expression of the target gene. The regulator consists of a polyadenylation signal and an upstream binding site, which, in the case of this study, binds to an FDA-approved tetracycline molecule.
The polyadenylation signal recruits the cell’s regulatory machinery to cleave the RNA molecule, thus preventing the expression of the target gene. This is the default ‘off’ position of the switch.
To turn the switch ‘on’, the upstream binding site binds tetracycline. This molecule masks the polyA signal, leading to the expression of the target gene. Moderation of the gene expression is achieved by altering the availability of the masking molecule.
The researchers demonstrated the effects of this ‘on/off’ switch mechanism both in vivo in mice and in vitro in human cell lines, showing dose-dependent, reversible control and long-term stability of the genetic switch.
This finding holds promise for implementing dose-dependent regulators into gene therapies to maintain them within specific therapeutic windows.
“This strategy allows us to be more precise in the control of gene expression of a therapeutic protein. It enables us to adjust its production according to disease’s stages or tune to the patient’s specific needs, all using the FDA-approved tetracycline dose,” explains Yen, corresponding author of the study. “Our approach is not disease-specific, it can theoretically be used for regulating the expression of any protein and potentially has many therapeutic applications. In addition, this system is more compact and easier to implement than the existing technologies. Therefore, it also can be very useful in the lab to turn a gene of interest on or off to study its function.”