Fig. 1.

Schematic representation of the CRISPR targeting strategy. a A c.403C>T mutation was introduced into exon 3 of PTCH1. The scissors represent Cas9/sgRNA targeting the sequence of intron 3 near the mutation site, resulting in DNA double-stranded breaks. The donor vector contained the inverted drug selection cassette PuroR, flanked by a 1.3-kb 5′ homologous arm carrying the c.403C>T point mutation and a 1-kb 3′ homologous arm. b The c.403C>T point mutation was predicted to be knocked into the hESC genome by homologous recombination. Primers P1, P2, P3 and P4 were used to screen the positive clones