A mutation was engineered in exon 2 to change arginine codon 46 (AGG) to a glutamine codon (CAG)(p.R46Q) and an FRT site flanked neomycin resistance gene cassette was inserted into intron 1. The neo cassette was removed through subsequent flp-mediated recombination. The mutation prevents cleavage at that residue by activated protein C (APC). (J:261560)