Two sgRNAs (5'-GGTCCGCACCATCGACGGCTCC-3' and 5'-GGAGCTGCGCGAGCGGGTCT-3') were used to target the start of the coding region of exon 1 with CRISPR/Cas9. A number of different deletions were found, with this allele, number 10, representing a 277 bp deletion removing part of the 5' UTR and the start of the coding region (-180 to +97). The absence of transcripts from this allele was confirmed by qPCR and the absence of peptides by Western blot analysis of thymus and brain samples.