Aspartic acid codon 387 (GAT) was targeted for change to an alanine codon (GCC)(p.D387A) with an sgRNA (targeting ACAGAACCACACTTTAGAAG) and an ssODN template (TTGCCTCATCATCTCACAAGAACTATATTCCGGATGAGGCAGAT) using CRISPR/Cas9 technology. This mutation prevents autoprocessing of the encoded peptide. (J:245476)