A floxed neomycin resistance cassette was inserted into intron 10 and sequence in exon 11 encoding amino-acid residue 393 was mutated from Thr to Ala (ACA to GCA) preventing phosphorylation of this residue. Heterozygotes were crossed with carriers of Meox2tm1(cre)Sor, excising the neomycin resistance cassette and leaving the T393A point mutation.