Noninvasive method for assessing the human circadian clock using hair follicle cells

A thorough understanding of the circadian clock requires qualitative evaluation of circadian clock gene expression. Thus far, no simple and effective method for detecting human clock gene expression has become available. This limitation has greatly hampered our understanding of human circadian rhythm. Here we report a convenient, reliable, and less invasive method for detecting human clock gene expression using biopsy samples of hair follicle cells from the head or chin. We show that the circadian phase of clock gene expression in hair follicle cells accurately reflects that of individual behavioral rhythms, demonstrating that this strategy is appropriate for evaluating the human peripheral circadian clock. Furthermore, using this method, we indicate that rotating shift workers suffer from a serious time lag between circadian gene expression rhythms and lifestyle. Qualitative evaluation of clock gene expression in hair follicle cells, therefore, may be an effective approach for studying the human circadian clock in the clinical setting.     

Glucocorticoid regulation of the circadian clock modulates glucose homeostasis

Circadian clock genes are regulated by glucocorticoids; however, whether this regulation is a direct or secondary effect and the physiological consequences of this regulation were unknown. Here, we identified glucocorticoid response elements (GREs) at multiple clock genes and showed that 3 were directly regulated by the glucocorticoid receptor. We determined that a GRE within the core clock gene Per2 was continuously occupied during rhythmic expression and essential for glucocorticoid regulation of that gene in vivo. We further demonstrated that mice with a genomic deletion spanning this GRE expressed elevated leptin levels and were protected from glucose intolerance and insulin resistance on glucocorticoid treatment but not from muscle wasting. We conclude that Per2 is an integral component of a particular glucocorticoid regulatory pathway and that glucocorticoid regulation of the peripheral clock is selectively required for some actions of glucocorticoids.     

Peripheral circadian clock for the cuticle deposition rhythm in Drosophila melanogaster

Insect endocuticle thickens after adult emergence by daily alternating deposition of two chitin layers with different orientation. Although the cuticle deposition rhythm is known to be controlled by a circadian clock in many insects, the site of the driving clock, the photoreceptor for entrainment, and the oscillatory mechanism remain elusive. Here, we show that the cuticle deposition rhythm is regulated by a peripheral oscillator in the epidermis in Drosophila melanogaster. Free-running and entrainment experiments in vitro reveal that the oscillator for the cuticle deposition rhythm is independent of the central clock in the brain driving the locomotor rhythms. The cuticle deposition rhythm is absent in null and dominant-negative mutants of clock genes (i.e., period, timeless, cycle, and Clock), indicating that this oscillator is composed of the same clock genes as the central clock. Entrainment experiments with monochromatic light-dark cycles and cry(b) flies reveal that a blue light-absorbing photoreceptor, cryptochrome (CRY), acts as a photoreceptor pigment for the entrainment of the cuticle deposition rhythm. Unlike other peripheral rhythms in D. melanogaster, the cuticle deposition rhythm persisted in cry(b) and cry(OUT) mutant flies, indicating that CRY does not play a core role in the rhythm generation in the epidermal oscillator.     

昼夜节律变化对动脉粥样硬化形成的影响及其相关通路的研究进展

地球上几乎所有的生命都存在昼夜节律,控制昼夜节律的生物钟具有重要的生理功能,同时也是疾病的重要调节器.昼夜节律与动脉粥样硬化关系密切.研究表明受损的生物钟会影响造血过程和糖脂代谢,并改变局部斑块病变中的细胞功能.在分子水平上,昼夜节律可以通过Toll样受体(TLR)通路调节动脉粥样硬化炎症状态和血管重塑,通过蛋白激酶B...     

The melatonin-sensitive circadian clock of the enteric bacterium Enterobacter aerogenes

Circadian clocks are fundamental properties of all eukaryotic organisms and at least some prokaryotic organisms. Recent studies in our laboratory have shown that the gastrointestinal system contains a circadian clock that controls many, if not all, aspects of gastrointestinal function. We now report that at least one species of intestinal bacteria, Enterobacter aerogenes, responds to the pineal and gastrointestinal hormone melatonin by an increase in swarming activity. This swarming behavior is expressed rhythmically, with a period of approximately 24 hrs. Transformation of E. aerogenes to express luciferase with a MotA promoter reveals circadian patterns of bioluminescence that are synchronized by melatonin and whose periods are temperature compensated from 26°C to 40°C. Bioinformatics suggest similarities between the E. aerogenes and cyanobacterial clocks, suggesting the circadian clock may have evolved very early in the evolution of life. They also point to a coordination of host circadian clocks with those residing in the microbiota themselves.     

Effects of dietary protein alterations on circadian rhythms of gastrointestinal peptides in rats

Altered protein diets and circadian rhythms of gastrin and cholecystokinin (CCK) were investigated in 126 male and 126 female Sprague-Dawley rats acclimated for two weeks to a 1212 hr lightdark cycle. Rats were divided equally and fed low-protein (8%), high-protein (64%) or normal protein (27%) diets for four weeks. All animals were fasted for 24 hr prior to blood collections. Blood samples were collected at 4-hr intervals for 24 hr for determination of plasma gastrin and CCK using specific radioimmunoassays. A significant rhythm for gastrin was detected in males on normal and lowprotein diets (P < 0.03) and in females on lowprotein diets (P < .02). A significant rhythm for CCK was detected (P < 0.05) in rats of both sexes fed normal and highprotein diets. Mean plasma levels of both peptides were lower in females than males. In a separate study, food intake and body weight were monitored in male rats receiving the three diets over 21 days. Animals on the lowprotein diet exhibited reduced food intake and body weight compared to rats fed the normal or high-protein diets.Presented in part at the Eighteenth International Conference on Chronobiology, Leiden, The Netherlands, July 12–17, 1987.Supported by a grant from the National Institutes of Health PO1 DK35608.     

Coincident light and clock regulation of pseudoresponse regulator protein 37 (PRR37) controls photoperiodic flowering in sorghum

Optimal flowering time is critical to the success of modern agriculture. Sorghum is a short-day tropical species that exhibits substantial photoperiod sensitivity and delayed flowering in long days. Genotypes with reduced photoperiod sensitivity enabled sorghum's utilization as a grain crop in temperate zones worldwide. In the present study, Ma(1), the major repressor of sorghum flowering in long days, was identified as the pseudoresponse regulator protein 37 (PRR37) through positional cloning and analysis of SbPRR37 alleles that modulate flowering time in grain and energy sorghum. Several allelic variants of SbPRR37 were identified in early flowering grain sorghum germplasm that contain unique loss-of-function mutations. We show that in long days SbPRR37 activates expression of the floral inhibitor CONSTANS and represses expression of the floral activators Early Heading Date 1, FLOWERING LOCUS T, Zea mays CENTRORADIALIS 8, and floral induction. Expression of SbPRR37 is light dependent and regulated by the circadian clock, with peaks of RNA abundance in the morning and evening in long days. In short days, the evening-phase expression of SbPRR37 does not occur due to darkness, allowing sorghum to flower in this photoperiod. This study provides insight into an external coincidence mechanism of photoperiodic regulation of flowering time mediated by PRR37 in the short-day grass sorghum and identifies important alleles of SbPRR37 that are critical for the utilization of this tropical grass in temperate zone grain and bioenergy production.     

Ordered changes in histone modifications at the core of the Arabidopsis circadian clock

Circadian clock function in Arabidopsis thaliana relies on a complex network of reciprocal regulations among oscillator components. Here, we demonstrate that chromatin remodeling is a prevalent regulatory mechanism at the core of the clock. The peak-to-trough circadian oscillation is paralleled by the sequential accumulation of H3 acetylation (H3K56ac, K9ac), H3K4 trimethylation (H3K4me3), and H3K4me2. Inhibition of acetylation and H3K4me3 abolishes oscillator gene expression, indicating that both marks are essential for gene activation. Mechanistically, blocking H3K4me3 leads to increased clock-repressor binding, suggesting that H3K4me3 functions as a transition mark modulating the progression from activation to repression. The histone methyltransferase SET DOMAIN GROUP 2/ARABIDOPSIS TRITHORAX RELATED 3 (SDG2/ATXR3) might contribute directly or indirectly to this regulation because oscillator gene expression, H3K4me3 accumulation, and repressor binding are altered in plants misexpressing SDG2/ATXR3. Despite divergences in oscillator components, a chromatin-dependent mechanism of clock gene activation appears to be common to both plant and mammal circadian systems.     

Individuality in gut microbiota composition is a complex polygenic trait shaped by multiple environmental and host genetic factors

In vertebrates, including humans, individuals harbor gut microbial communities whose species composition and relative proportions of dominant microbial groups are tremendously varied. Although external and stochastic factors clearly contribute to the individuality of the microbiota, the fundamental principles dictating how environmental factors and host genetic factors combine to shape this complex ecosystem are largely unknown and require systematic study. Here we examined factors that affect microbiota composition in a large (n = 645) mouse advanced intercross line originating from a cross between C57BL/6J and an ICR-derived outbred line (HR). Quantitative pyrosequencing of the microbiota defined a core measurable microbiota (CMM) of 64 conserved taxonomic groups that varied quantitatively across most animals in the population. Although some of this variation can be explained by litter and cohort effects, individual host genotype had a measurable contribution. Testing of the CMM abundances for cosegregation with 530 fully informative SNP markers identified 18 host quantitative trait loci (QTL) that show significant or suggestive genome-wide linkage with relative abundances of specific microbial taxa. These QTL affect microbiota composition in three ways; some loci control individual microbial species, some control groups of related taxa, and some have putative pleiotropic effects on groups of distantly related organisms. These data provide clear evidence for the importance of host genetic control in shaping individual microbiome diversity in mammals, a key step toward understanding the factors that govern the assemblages of gut microbiota associated with complex diseases.