CRISPR-targeting floxed the endogenous exon 2 and inserted an exon 2 with a point mutations encoding the amino acid substitution lysine to threonine at position 71 (K71T). This mutation produces a protein with hyper-accurate translation (ha). Flp-mediated recombination removed the FRT-flanked neomycin resistance cassette. Cre-mediated recombination removed the endogenous exon 2.