Serine codon 533 (TCA) was targeted with an sgRNA (targeting CTCTGGAGGCAGGAATCAAT) and ssODN templates using CRISPR/Cas9 technology, changing it to alanine codon GCA (p.S533A). This mutation renders the encoded peptide nonphosphorylatable at this residue. Western blot experiments confirmed the expression of peptides from this allele.