New Perspectives of Designer Oligosaccharides: From Fixing Human Faulty Genes to Controlled Gene Expression

Timor Baasov, Schulich Faculty of Chemistry, Technion, Haifa, Haifa

The treatment of genetic disorders is one of the biggest challenges lying ahead of modern medicine. While major advancements have been made in gene therapy, it is still far from achieving clinical success. One alternative method that has emerged recently is suppression of pathogenic nonsense mutations through inducing translational readthrough of the in-frame stop mutations. Aminoglycosides were the first drugs that gave promising results in this respect. However, high toxicity of these drugs and reduced suppression activity at sub-toxic doses has limited their clinical use in suppression therapy.

To address these issues, we have designed and synthesized a series of new derivatives of aminoglycosides, and their ability to read-through stop codon mutations was examined in both in-vitro and animal models of various diseases. Some of them demonstrated exceptional improvement in stop-codon read-through activity while in parallel maintained low toxicity.

Encouraged, we also used the lead designer structures for controlled gene expression. For example, while the Cre/loxP system is widely used in mice to achieve cell-type-specific gene expression, these gene regulation systems possess some significant caveats in addressing fundamental neurobiological issues. To overcome these limitations, we designed a brand new Cre/loxP system by introducing a premature termination codon (PTC) into the coding sequence of Cre gene (nsCre). By this way, we achieved rapid and specific control of gene targeting by administering designer aminoglycosides into a pre-defined brain region of adult nsCre-expressing animals within desired time window. The observed biochemical data will be analyzed in terms of structure-activity-toxicity relationships of designed structures; in terms of their eukaryotic versus prokaryotic selectivity and 3D crystal structures of designed molecules in complex with the ribosomal A-site RNA construct.