Intercellular coupling between peripheral circadian oscillators by TGF-beta signaling [RNA-seq]

Intercellular coupling is crucial to prevent desynchronization of cell-autonomous oscillator networks and thus, the disruption of circadian tissue functions. While, neuronal oscillators within the mammalian central clock, the suprachiasmatic nucleus (SCN), couple intercellularly via the exchange of secreted neurotransmitters, intercellular coupling among peripheral oscillators is highly debated and molecular mechanisms are unknown. In our study, we show that peripheral circadian oscillators couple intercellularly via the exchange of secreted signaling molecules and identify TGF-beta as peripheral coupling factor. TGF-beta signaling induces the cAMP response element dependent, immediate-early expression of the clock gene PER2, thereby phase-adjusting the molecular circadian oscillator. Genetic or pharmacologic disruption of TGF-beta signaling causes desynchronization of cellular oscillators resulting in amplitude reduction and increased sensitivity towards Zeitgeber cues. Our findings reveal a previously unknown mechanism of peripheral coupling and open a new perspective on the importance of peripheral clock synchrony for rhythmic organ functions and circadian health. Examination of transcriptome changes in densely and sparsely cultured U-2 OS cells following a 2 hs stimulation pulse with U-2 OS conditioned and control medium 16-18 hs after dexamethasone synchronization.