The targeting vector contains from (5' to 3'): CAG promoter, a loxP STOP loxP cassette, Epac cAMP sensor, WPRE, polyadenylation signal sequence and is inserted between exons 1 and 2 of the Gt(ROSA)26Sor Ai9 targeting vector. The Epac sensor reports cAMP binding by changes in fluorescence energy transfer (FRET). The sensor consists of an mTurqoise donor, a monomeric variant of the cyan fluorescent protein, and a circularly permutated Venus enhanced yellow fluorescent protein, Venus-Venus, acceptor sandwiching the cAMP-binding protein Rapgef3. (J:263913)