Threonine codon 115 (ACC) in exon 3 was changed to asparagine (AAC)(p.T115N) and a loxP site was inserted into intron 2 and an FRT site flanked neomycin resistance gene cassette and a second loxP site into intron 3. The neo cassette was removed through subsequent flp-mediated recombination and exon 3 deleted through cre-mediated recombination. Immunoblot experiments on MEFs confirmed absence of protein expression from this allele. (J:314784)