Arginine codons 276 (AGG) and 279 (AGG) in exon 8 were changed to alanine (GCG) (p.R276A, p.R279A) using an sgRNA and an ssODN template with CRISPR/Cas9 technology. These mutations block processing of the encoded peptide by FURIN (paired basic amino acid cleaving enzyme) and site 1 membrane-bound transcription factor peptidase (MBTPS1). (J:324587)