CRISPR/Cas9 technology was used with sgRNA 5'-TAGGGCTATGTCTGAGCCAG-3' and a donor oligonucleotide to generate a T>C mutation changing cysteine codon 14 (TGT) to an arginine codon (CGT) (p.C14R). This mutation has spontaneously arisen in some Ly5.1 (B6.SJL-Ptprca Pepcb/BoyJ) colonies. (J:278854)