The CRISPR/Cas9 system and sgRNA 5'-ACAGTGAGATTGAGCGGCGC-3' was used to generate the mice. The CRISPR/Cas9 system generated a one-base pair replacement at c.373T>C (NM_007488.3). The mutation results in an arginine to cysteine change at amino acid 74 (p.R74C).