Serine codons 435 (TCA) and 439 (TCC) in exon 6 were changed to alanine (GCA, GCC) (p.S435A, p.S439A) and a loxP site flanked neomycin resistance gene cassette was inserted into intron 5. The neo cassette was removed through subsequent Cre-mediated recombination. The mutations block phosphorylation of the affected residues in the encoded peptide. (J:277918)