A loxP site was inserted upstream of the CArG (CC(A/T)6GG) regulatory element in exon 15. An FRT- and loxP-flanked neomycin resistance cassette was inserted downstream of the CArG element. Flp-mediated recombination removed the selection cassette and left the CArG element floxed. Cre-mediated recombination removed the CArG element. This allele targets the smMLCK isoform without affecting full-length Mylk or telokin. (J:204964)