The targeting construct contained the CAG promoter (chicken beta actin promoter with CMV enhancers), a floxed neomycin-Westphal stop sequence (WSS) cassette, a modified Kcnj11 gene, an IRES and GFP sequence. Kcnj11 has been modified by a 30 amino acid N-terminal truncation and by a modification of the codon for amino acid residue 185 causing a lysine to glutamine substitution. Cre mediated excision of the neo-WSS cassette permits expression of the mutated Kcnj11 and GFP under the control of the CAG promoter. (J:146650)