Nucleotide substitution resulted in the amino acid substitution of serine with alanine at positions 231 and 234 (p.S231A, p.S234A), abolishing phosphorylation potential at those residues. Serine codon 218 was changed from TCA to AGC as a silent mutation to create a diagnostic SacI restriction site. Cre-mediated recombination removed a loxP site flanked neomycin resistance gene cassette that was inserted downstream of the gene.