Stable expression of hCas9 allowed us to efficiently target a human disease gene in iPSCs. We targeted Tafazzin (TAZ), a gene on the X chromosome that is mutated in Barth syndrome (BTHS), a mitochondrial cardiomyopathy13. We designed a gRNA and a homology directed repair (HDR) template to introduce a known BTHS mutation (c.517delG)14 into TAZ exon 6 and co-transfected them into PGP1-hCas9-PB with Dox treatment. The surveyor mutation detection assay suggested efficient TAZ gene modification with Dox treatment, and no detectable modification in the absence of Dox (Fig. 2a). High throughput sequencing of the targeted locus from pooled genomic DNA9 showed that 30% of cells had an indel near the engineered double strand break, while 50% had undergone HDR and harbored the sequence variant programmed by the HDR donor (Fig. 2b).
