A K1259T (nucleotide AAA to ACC) missense mutation that is homologous to the human K1270T mutation was introduced to exon 19 using CRISPR/Cas9 methodologies. A silent EcoRV site mutation used for genotyping was introduced downstream of K1270T, and 2 additional silent insertional mutations flank the K1270T mutation to prevent Cas9 activity on the repaired allele. (J:320991)