In gene therapy, not all genes can be transported equally well into the target cells. Researchers have now developed a flexible method to deliver large genes efficiently and without significant side effects. The approach has great potential for therapeutic applications.
Gene therapy is currently the most promising approach to treat hereditary diseases. Despite decisive breakthroughs in recent years, several hurdles still exist that hamper its broader application. These include the efficient delivery of genetic material into target cells using adeno-associated viral vectors (AVV). While these delivery vehicles are characterized by a good safety profile and high gene transfer efficiency, and are therefore very commonly used in gene therapies as well as in genome editing by CRISPR/Cas. But: AAVs have a limited uptake capacity for DNA and cannot fully transport larger genes.
In the past, various methods have been developed to circumvent this disadvantage of AAVs. For example, the DNA to be introduced is divided into two fragments, which are produced individually but reassemble seamlessly in the target tissue of the cell. However, the disadvantage of these methods is that they are not very efficient or not very flexible in experimental design and could also trigger side effects.
Merge only at transcript level
The team led by Elvir Becirovic, Professor of Experimental and Translational Ophthalmology at the University of Zurich, has now succeeded in developing a novel approach that circumvents these disadvantages. The new method REVeRT (reconstitution via mRNA trans-splicing) also uses the principle of two fragments on dual AAV vectors. The coding DNA material is packaged into the AAV vectors, introduced into the cells and transcribed into messenger RNA (transcript).
This has the advantage that the method is efficient and has fewer side effects," explains Becirovic. Our approach is also more flexible than previous methods because the large genes can be divided into two fragments at various points. And ’ His team has developed the method for ophthalmological applications in cell cultures and successfully evaluated it in animal models under various conditions, for example to cure hereditary macular degeneration with gene therapy.
Possible therapy for various diseases
Becirovic emphasizes, however, that REVeRT is also suitable for gene therapy of other genetic or acquired diseases - such as diverse, widespread blood or age-related diseases. Moreover, the new method can be used just as much for gene therapy studies in the context of genome editing by CRISPR/Cas. In order to be able to use such modules therapeutically, the DNA coding for them must also be introduced into the target cells as efficiently as possible with the aid of carriers such as AAVs. ’With CRISPR/Cas, further applications are possible that open up new therapeutic options,’ explains Becirovic.
Lisa Maria Riemayer et al. mRNA trans-splicing dual AAV vectors for (epi)genome editing and gene therapy. Nature Communications, October 18, 2023. doi: 10.1038/s41467’023 -42386-0.