Oscillating on Borrowed Time: Diffusible Signals from Immortalized Suprachiasmatic Nucleus Cells Regulate Circadian Rhythmicity in Cultured Fibroblasts

Only SCN2.2 cells were capable of endogenously generating circadian rhythms in 2-deoxyglucose uptake and Per gene expression.

• SCN2.2 cells can impose metabolic activity rhythms on NIH/3T3 fibroblasts through a diffusible signal.
• The rhythms conferred to NIH/3T3 cells were phase delayed by 4-12 hours compared to SCN2.2 patterns.
• Sustained metabolic rhythmicity in NIH/3T3 cells required ongoing exposure to SCN2.2 outputs.
• Serum-shocked NIH/3T3 fibroblasts showed oscillations in clock gene expression but not in metabolic activity.
• In serum-shocked fibroblasts, peak expression of Per1 and Per2 mRNA occurred 4 hours before Cry1 and Cry2 mRNA levels.

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