Figure 4.

Integration and HDR Analysis of CRISPR/Cas9-Edited EBS hKc

After co-transfection of the respective Cas9/sgRNA combinations (spCas9-sgRNA1, spCas9-sgRNA2, or both Cas9n-sgRNA1 and Cas9n-sgRNA2) and the MC donor plasmid into EBS hKc, we performed two rounds of blasticidin selection. The resulting blasticidin-resistant cells were then analyzed for site-specific integration of the donor template at the genomic level. (A) Integration-specific PCR using a forward primer binding the restriction sites EcoRI and NheI (white box) provided by the MC and a reverse primer binding downstream to the 3′ UTR of the KRT14 gene resulted in a PCR product of 893 bp. (B) EcoRI digestion to estimate the relative recombination efficiency in the treated cell pool. We performed a PCR using a forward primer binding to exon 6 and a reverse primer binding a sequence downstream of KRT14 3′ UTR. The PCR resulted in a specific product of 1,189 bp. EcoRI digestion generated the expected fragments of 874 and 315 bp, only visible in the Cas9n 1- and 2-treated EBS hKc. (C) Schematic depiction of the primer binding sites used for amplification of the integration-specific PCR fragments. Gray arrows indicate a forward primer binding to the restriction sites EcoRI and NheI integrated via HDR. Black arrows indicate forward and reverse primers binding to endogenous KRT14. Black star: missense mutation (c.1231G>A) in exon 6; gray stars: silent mutations.