Specificity and editing efficiency of the nCas9 ^ERT2 system. (A) Schematics of experimental procedures. Tg(piwil1:nCas9^ERT2-n3U) (left) or Tg(piwil1:nCas9-n3U) (right) transgenic females were crossed to WT males, which produced embryos with maternal expression of inducible nCas9^ERT2 or non-inducible nCas9, respectively. (B) Left, bar chart showing the ratio of different morphological types of tbxta-gRNA–injected 4-OHT– or DMSO-treated nCas9^ERT2 embryos and nCas9 embryos at 24 hpf. n, the number of embryos. Right, morphology of representative embryos in each class. The boxed areas of notochord were enlarged. (C) Mutation rate of the tbxta locus in mCherry-positive PGCs or mCherry-negative SCs in different groups at 24 hpf. A region in the tbxta locus was amplified and cloned, followed by sequencing individual clones. N, number of sequenced clones. (D) Bar chart showing the mutation rate of the tbxta locus in mCherry-positive PGCs or mCherry-negative SCs in tbxta-gRNA–injected 4-OHT– or DMSO-treated nCas9^ERT2 embryos at 24 hpf, calculated with NGS results. No. reads, the number of aligned reads per target site. Source data are available for this figure: SourceData F3.