The FusX TALE Base Editor (FusXTBE) for Rapid Mitochondrial DNA Programming of Human Cells In Vitro and Zebrafish Disease Models In Vivo

CRISPR J. 2021 Dec;4(6):799-821. doi: 10.1089/crispr.2021.0061. Epub 2021 Nov 30.


Functional analyses of mitochondria have been hampered by few effective approaches to manipulate mitochondrial DNA (mtDNA) and a lack of existing animal models. Recently a TALE-derived base editor was shown to induce C-to-T (or G-to-A) sequence changes in mtDNA. We report here the FusX TALE Base Editor (FusXTBE) to facilitate broad-based access to TALE mitochondrial base editing technology. TALE Writer is a de novo in silico design tool to map potential mtDNA base editing sites. FusXTBE was demonstrated to function with comparable activity to the initial base editor in human cells in vitro. Zebrafish embryos were used as a pioneering in vivo test system, with FusXTBE inducing 90+% editing efficiency in mtDNA loci as an example of near-complete induction of mtDNA heteroplasmy in vivo. Gene editing specificity as precise as a single nucleotide was observed for a protein-coding gene. Nondestructive genotyping enables single-animal mtDNA analyses for downstream biological functional genomic applications. FusXTBE is a new gene editing toolkit for exploring important questions in mitochondrial biology and genetics.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CRISPR-Cas Systems
  • DNA, Mitochondrial* / genetics
  • Gene Editing
  • Humans
  • Mitochondria / genetics
  • Zebrafish* / genetics


  • DNA, Mitochondrial