Transcriptional control of synaptic components by the clock machinery.

Circadian rhythms are generated in mammals by a central clock located in the suprachiasmatic nucleus of the hypothalamus, which regulates the homeostasis of many biological processes. At the molecular level, the regulation of circadian rhythms is under the control of transcriptional-translational feedback loops composed of clock factors, including transcription factors. In the brain, synaptic plasticity has been shown to vary with a 24-h rhythm. Also, when measured at a given time-of-day, synaptic plasticity has been observed to be disrupted by dysregulation of clock factors. This could suggest a regulation of synaptic functions by the clock machinery. Interestingly, many studies provide support for direct and indirect transcriptional regulation by core clock factors, including rhythmic gene expression, for a variety of synaptic components. Indeed, the gene of several neuropeptides, neurotransmitter regulators, receptors and transporters, ion channels, vesicle proteins, and adhesion and scaffolding molecules present evidence to be clock-controlled. We here present, while considering different regions of the mammalian brain, an overview of the extent of the transcriptional control of synaptic components by the clock machinery.