Using an sgRNA and an ssODN template (gctcccaagggactatcctggcctagccctgctaaacacaaaacacttcctttctatgttgtagGcGgcttcccgccgggtaggcctctcctgtgccaactgccagactaccaccaccacg) with CRISPR/Cas9 technology, serine codon 261 (TCC) was changed to alanine (GCG) (p.S261A). This mutation blocks the phosphorylation of the residue.