Sequence upstream of exon 1 and in intron 8 were targeted with a pair of sgRNAs (targeting (1) TCCACTTCTCTAGTGCTAGG and (3) AGGCAGCTACACCACCCTCC), resulting in the deletion between sgRNA targets 1 and 3 containing exons 1-8. The ESCs used for the creation of this allele also contain the Tg(CAG-EGFP,Acr-EGFP)2Osb double transgene.