Uncovering the hidden 12-hour biological rhythms in mammals

The majority of 12-h rhythms may be regulated by a distinct and cell-autonomous pacemaker involving the spliced form of the XBP1 transcription factor.

• Biological oscillations can cycle at different harmonics of the 24-h circadian rhythms, including a robust 12-h cycle.
• Recent evidence suggests that the 12-h oscillation operates independently of the circadian clock and environmental cues.
• The spliced form of the XBP1 transcription factor (XBP1s) is implicated in the regulation of 12-h rhythms.
• XBP1s levels exhibit a 12-h cycle that is associated with the transcriptional generation of gene expression rhythms in the central dogma information flow pathway.
• The review highlights the evolutionary origin, regulatory mechanisms, and functional roles of the mammalian 12-h pacemaker in various physiological and pathological processes.

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