Arginine codons 80 (AGG) and 81 (AGG) in exon 4 were changed to alanine (GCC, GCA) (p.R80_R81delinsAA) using sgRNAs (targeting GAGGAGGATAAAGCCCGAAG and TGACTCACAGCAAGTCTGGG) and an ssODN template with CRISPR/Cas9 technology. R80 is essential for matriptase-mediated cleavage of the encoded peptide. (J:340720)