Data from: Differential phasing between circadian clocks in the brain and peripheral organs in humans

The daily timing of mammalian physiology is coordinated by circadian clocks throughout the body. Although measurements of clock gene expression indicate that these clocks in mice are normally in phase with each other, the situation in humans remains unclear. We used publicly available data from five studies, comprising over 1000 samples, to compare the phasing of circadian gene expression in human brain and human blood. Surprisingly, after controlling for age, clock gene expression in brain was phase-delayed by ~8.5 h relative to that of blood. We then examined clock gene expression in two additional human organs and in organs from nine other mammalian species, as well as in the suprachiasmatic nucleus (SCN). In most tissues outside the SCN, the expression of clock gene orthologs showed a phase difference of ~12 h between diurnal and nocturnal species. The exception to this pattern was human brain, whose phasing resembled that of the SCN. Our results highlight the value of a multi-tissue, multi-species meta-analysis, and have implications for our understanding of the human circadian system.哺乳动物的生理日常节律由全身各处的昼夜节律钟（circadian clocks）协同调控。尽管针对时钟基因表达（clock gene expression）的检测结果显示，小鼠体内的此类节律钟通常彼此保持同相位，但人类的相关状况仍未明确。本研究借助五项已公开研究的数据集（涵盖超1000个样本），对比了人类大脑与血液中昼夜节律基因表达的相位特征。令人意外的是，在控制年龄变量后，大脑的时钟基因表达相较于血液出现了约8.5小时的相位延迟。随后，我们分析了另外两类人体器官、其余9种哺乳动物的器官组织，以及视交叉上核（suprachiasmatic nucleus, SCN）的时钟基因表达数据。在视交叉上核之外的多数组织中，时钟基因同源物（orthologs）的表达在昼行性与夜行性物种间存在约12小时的相位差。该模式的唯一例外是人类大脑，其相位特征与视交叉上核高度相似。本研究结果凸显了多组织、多物种荟萃分析的研究价值，同时为人类昼夜节律系统的相关研究提供了新的启示。