CRISPR/cas9 genome editing uses guide RNAs to target upstream [CACCACGTTAAAGCACAGGG; GCTCCCACCACTAAGGTCAG] and downstream [GCTTGTGGCAGCTTACTGAG; GCTCAACTGTAGTATCACGC] of exon 4. Il4ra transcript Il4ra-201 was used as reference for the exon number and the guide sequences (J:341579)