The Journal Club returns on 25th July at 12:00 Eastern time to the Lifespan.io Facebook channel. Editing mitochondrial DNA (mtDNA) has long been a challenge and systems such as CRISPR, which make editing regular DNA faster and easier, are very difficult to use when it comes to mtDNA. This month we are going to take a look at a new paper where researchers have used a different approach to edit the mtDNA.
A number of mitochondrial diseases in humans are caused by point mutations that could be corrected by base editors, but delivery of CRISPR guide RNAs into the mitochondria is difficult. In this study, we present mitochondrial DNA base editors (mitoBEs), which combine a transcription activator-like effector (TALE)-fused nickase and a deaminase for precise base editing in mitochondrial DNA. Combining mitochondria-localized, programmable TALE binding proteins with the nickase MutH or Nt.BspD6I(C) and either the single-stranded DNA-specific adenine deaminase TadA8e or the cytosine deaminase ABOBEC1 and UGI, we achieve A-to-G or C-to-T base editing with up to 77% efficiency and high specificity. We find that mitoBEs are DNA strand-selective mitochondrial base editors, with editing results more likely to be retained on the nonnicked DNA strand. Furthermore, we correct pathogenic mitochondrial DNA mutations in patient-derived cells by delivering mitoBEs encoded in circular RNAs. mitoBEs offer a precise, efficient DNA editing tool with broad applicability for therapy in mitochondrial genetic diseases.
Yi, Z., Zhang, X., Tang, W. et al. Strand-selective base editing of human mitochondrial DNA using mitoBEs. Nat Biotechnol (2023)