Precision modeling of mitochondrial diseases in zebrafish via DdCBE-mediated mtDNA base editing

Abstract

Mitochondrial diseases are a group of heterogeneous genetic disorders that are characterized by dysfunctional mitochondria and often manifest as severe even lethal condition 1 . Mitochondrial diseases can arise from mutations affecting either the nuclear gene or the mitochondrial DNA (mtDNA), whereas pathogenic mutations in mtDNA more commonly cause mitochondrial disease than mutations in nuclear genes do 2 . Up to now, more than 270 pathogenic variants of mtDNA have been reported 3 . Animal models which precisely install these variants are urgently needed both to deepen our understanding for the etiology of mitochondrial diseases and to develop therapeutic strategies. The development of such models, however, has been hindered by the technical challenge of editing mtDNA in a programmable fashion. In recent years, some progresses have been made for mitochondrial genome engineering. Re-engineered RNA-free programmable nucleases such as mtZFN and mitoTALEN function effectively in mitochondria 4 , 5 . In a recent work, researchers harnessed a bacterial cytidine deaminase, DddA, to archive precise manipulation of mtDNA sequences 6 . In this system, the domain containing 1264–1427 amino acids of DddA (DddAtox) was split into two inactive halves, which were fused with transcription activator-like effector (TALE) and a uracil glycosylase inhibitor, resulting in DddA-derived cytosine base editors (DdCBEs). Besides the study in tissue culture system, installation of disease-associated mtDNA variants in mouse with this DddA tox -TALE strategy has been reported lately 7 . Acclaimed for multiple research advantages and flexibility of manipulation, zebrafish is an attractive animal model for studying human disease 8 . The ability to generate pathogenic mtDNA mutations in zebrafish could accelerate the researches ranging from mitochondrial biology, drug discovery to therapeutic approaches development.

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