A cassette containing Camk2a-exon2 fused to tdTomato, followed by the woodchuck hepatitis virus post-transcriptional regulatory element (WPRE), flanked by LoxP sites, and a neomycin cassette for positive selection, flanked by Frt sites was inserted upstream of Camk2a exon2. This results in a KO first mutant mouse line expressing tdTomato from the endogenous Camk2a promoter. Crossing this line with a cre line restores CAKM2A expression. (J:321822)