Non-viral genetic therapy strategies for the treatment of ataxia telangiectasia

1 Aug '2019 by James Grey

My research is centred around gene therapy, with the specific aim of treating ataxia telangiectasia (A-T). This disease is characterised by cerebellar wasting, or atrophy, and eventually lymphoma; caused by mutations in the ataxia telangiectasia mutated gene, or ATM. The mutations which cause disease are typically located in the kinase domain or in proximity to regulatory regions of the protein. This disease is very rare, with zero fecundity, and as such is always caused by non-heritable mutations. The mutations vary in severity with the most severe likely impairing embryo viability. A-T can also be caused by a complete lack of ATM expression. The phenotype of ATM knock-out associated A-T is less severe than so-called kinase-dead ATM phenotypes where a non-functional protein is expressed in place of no expression at all.

The ATM protein is 3056 amino acids, encoded by an mRNA 13147 base pairs in length, from a 146 kilobase gene. As such, treating ATM with gene therapy is extremely problematic. Popular adeno-associated virus (AAV) systems cannot contain the quantity of DNA required to fix the ATM gene and fixing one mutation will only help a handful of patients due to the wide variation of mutations which cause A-T.

The technology my group has used to tackle this problem is glycosaminoglycan enhanced transduction peptides or GET-peptides for short. These peptides can complex with DNA via electrostatic interactions and form nanoparticles approximately 120 nm in size. This technology can form stable nanoparticles containing the full ATM gene, with no exons, and we have now shown that DNA molecules of this size can be delivered and expressed in vitro.

Using a translocase system known as ‘Sleeping Beauty’ we have shown stable expression in 50% of cells after two sequential deliveries of GET-peptide nanoparticles. We have also shown, in vitro, that the synthetic, human codon optimised, CpG-free ATM gene which is being delivered, is expressed but heavily regulated on both the mRNA and protein level. The aim of research now is to bring everything together into one system, delivering stable nanoparticles containing ATM and inserting the gene into the genome via Sleeping Beauty or by CRISPR/Cas9 for full recovery of cell-autonomous regulation of ATM. I really enjoy working on this new exciting technology, with the prospect of driving forward more powerful personalised medicines.

The quality of speakers and seminars at the 2019 Annual BSGCT conference was extremely high, with personal highlights being talks by Timothy Cox, speaking on Tay-Sachs and Sandhoff diseases; and Helen McCarthy, speaking on the RALA-peptide delivery system. What was particularly apparent, across speakers, was the grit and determination going into gene therapeutics for applications across a wide range of diseases with the sole purpose of making patients lives better. I found this atmosphere very inspiring and a great environment for creativity and discussion in the field, especially due to the relationships between researchers and the biotechnology and pharmaceutical industries.

I would like to take this opportunity to thank the European Society for Gene and Cell Therapy for awarding me with the best poster presentation award; and for giving me the opportunity to communicate my groups work to a wider audience.


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