An FRT site flanked neomycin resistance gene cassette was inserted into intron 1. Exon 1 was targeted with two codon changes: a silent mutation of L54 (CTT to CTG) and an S55A (TCA to GCC) mutation. These mutations create a diagnostic MscI restriction site and changes serine 55 to an alanine, thus preventing phosphorylation of the peptide at that position. (J:238996)