Institute of Molecular Health Science
Host: Marko Jovanovic
Title: Correction of autosomal recessive disorders via CRISPR-associated base editors in adult animals
Abstract:The CRISPR-Cas genome-editing tool holds great promise for treatment of genetic disorders. Clinical translation, however, is hampered by the low frequency of precise repair of the Cas9-induced DNA double-stranded breaks (DSB) via homology-directed repair (HDR). We have a strong interest in developing CRISPR approaches with enhanced precision for ex vivo and in vivo gene editing therapies. I will first present a novel CRISPR system, in which we co-localized the DNA repair template to the Cas9 nuclease via covalent linkage. Using this system we can increase HDR rates up to 24-fold in cell lines and dividing primary cells, supporting potential application in ex vivo gene therapies. I will then provide insights into our efforts of developing in vivo gene editing approaches. Precise gene editing in vivo in adult organisms is challenging, since most adult tissues primarily consist of non-dividing cells in which HDR is inactive. In the study I will present, we circumvented this problem by applying CRISPR-associated base editors, which enable direct conversion of C∙G to T∙A base pairs and vice versa independent of DNA break formation and HDR. When targeting a mouse model for the metabolic liver disease Phenylketonuria, systemic delivery of base editors via AAV resulted in gene correction rates that fully restored physiological blood phenylalanine levels. We observed mRNA correction rates up to 63%, restoration of the phenylalanine hydroxylase enzyme activity, and a reversion of the light fur phenotype. Our findings suggest the feasibility of using CRISPR-associated base editors to repair genetic diseases in vivo in adult patients.