The molecular clock is disrupted in cardiac-specific inducible Bmal1−/− (iCSΔBmal1−/−) mouse hearts. A: representative gels of PCR products showing that recombination at the Bmal1 locus occurs specifically in the heart of the iCSΔBmal1−/− mice but not in other tissues. No recombination was seen in iCSΔBmal1+/+. The recombined gene product shows a band at 571 bp, whereas the nonrecombined product shows a band at 431 bp. Dia, diaphragm; Sol, soleus; Gtn, gastrocnemius; Liv, liver; AA, abdominal aorta; Br, brain. B: the circadian expression profile of Bmal1 and Dbp is significantly blunted specifically in the heart of iCSΔBmal1−/− mice. Dark and light bars represent subjective night and day extrapolated from their prior light:dark (L:D) cycle before release in constant darkness (DD). Bar graphs show average amplitude values with 95% confidence intervals as error bars. n = 4/time point; *P < 0.05.