01/01/2020 → 31/12/2022
Centre for Eye Research Australia
Engineering of molecular tools to correct disease-causing mutations in mitochondrial DNA for Leber's Hereditary Optic Neuropathy
Leber’s hereditary optic neuropathy (LHON) is the most common mitochondrial DNA
disease, causing optic nerve degeneration and devastating blindness in patients.
Currently there is no cure for this disease. Recent revolutionary discoveries in the genetic engineering field has greatly improve our ability to modify and edit DNA. This project aims to develop and adapt new gene editing technology to correct the three most common LHON genetic changes (mutations), providing a novel strategy for gene therapy to cure LHON.
Leber’s Hereditary Optic Neuropathy (LHON) is a currently untreatable mitochondrial disease characterized by loss of retinal ganglion cells (RGCs) and sudden blindness. In approximately 95% of cases, LHON is caused by one of three point mutations in the mitochondrial DNA (mtDNA) genes (m.11778G>A, m.14484T>C, m.3460G>A) that code for mitochondrial Complex I subunits.
This forms part of a multi-enzyme assembly that generates ATP as a cellular energy source through oxidative phosphorylation (OXPHOS). Dysfunction of Complex I result in decreased ATP production, increased level of oxidative stress and impaired glutamate transport, ultimately leading to RGC apoptosis.
Despite the identification of the underlying genetic mutations that cause LHON, effective treatment options are currently very limited. Studies currently in clinical trials includes gene therapy to replace the faulty NADH dehydrogenase subunit 4 (ND4) as well as in vivo preclinical studies in mice using programmable nucleases to specifically target mutant mtDNA. However, for gene augmentation therapy approaches continued stable expression of the transgene would be essential, conversely mtDNA cleavage-based methods will only be beneficial for heteroplasmic mtDNA diseases, where copies of both the mutant and non-mutant mtDNA are present. LHON is typically a homoplasmic disease, where only mutant copies of the mtDNA are present. In this regard, gene therapy to permanently correct the underlying LHON mutations provides a real possibility to cure LHON disease and to prevent blindness in patients. Therefore, engineering new molecular tools to specifically modify mutant mtDNA is a very appealing approach for treatment of LHON disease.
With the advent of new advances in genetic engineering tools including developments in Transcription Activator-Like Effector (TALE) and Clustered Regularly Interspersed Short Palindromic Repeat (CRISPR) gene editing technologies open up the prospect of anticipatory cures to well-defined inherited genetic diseases. This project will engineer and interrogate the use of programmable base editing tools to correct mtDNA mutations that specifically cause LHON. Furthermore the development of mitochondrial gene editing tools will open prospects of utilising the vast CRISPR molecular toolbox for modification of other mitochondrial genes.