Schematic representation of the generation of cardiac‐specific conditional CCR9‐KO mice and their identification. A, Schematic illustration of cardiac‐specific conditional CCR9‐KO generation. B, Amplification of the entire region covering the floxed exon 1, exon 2, and homology arm using the F1/R1 primer (left) and the circle excised by Cre using the F2/R2 primer (right). C, DNA sequence of the truncated fragment amplified by the F1/R1 primer (upper) and the circular PCR products amplified by the F2/R2 primer (lower). D, Western blot and quantitative results for CCR9 expression levels in different tissues of CCR9‐KO and CCR9‐floxed/MEM‐Cre mice (n=6 per group; *P<0.05 vs CCR9‐floxed group). CCR9, C‐C motif chemokine receptor 9; CDS, coding sequence; HR, heart rate; KO, knockout; LA, left atrium; MCS, multiple cloning site; PCR, polymerase chain reaction; RA, right atrium; sgRNA, single‐guide RNA; UTR, untranslated region; WT, wild type.