CRISPR/cas9 mediated recombination using two sgRNAs (targeting GCAGTCGGATAGCATGGATACGG and GGCTCCACCAGCTTCTCGGATGG) created a 3 bp insertion (GGT) and 9 bp deletion (TCCATCCGA) in exon 2. Western blot analysis confirmed the absence of expression in spleens from homozygous mice.