A c.419G>A mutation was engineered in exon 4, changing arginine codon 140 into a glutamine codon (p.Arg140Gln). This mutation is found in tumors from human accute myeloid leukemia (AML) patients. A loxP site flanked neomycin resistance gene and stop cassette was inserted into intron 3. This creates a conditional-ready null allele that expresses the mutated protein only after cre-mediated recombination. (J:241017)