The role of circadian gene CLOCK in cancer.

Circadian Locomotor Output Cycles Kaput (CLOCK) is one of the circadian clock genes and is considered to be a fundamental regulatory gene in the circadian rhythm, responsible for mediating several biological processes. Therefore, abnormal expression of CLOCK affects its role in the circadian clock and its more general function as a direct regulator of gene expression. This dysfunction can lead to severe pathological effects, including cancer. To better understand the role of CLOCK in cancer, we compiled this review to describe the biological function of CLOCK, and especially highlighted its function in cancer development, progression, tumor microenvironment, cancer cell metabolism, and drug resistance.

Epigenetic/circadian clocks and PCOS.

Polycystic ovary syndrome (PCOS) affects 6-20% of reproductive-aged women. It is associated with increased risks of metabolic syndrome, Type 2 diabetes, cardiovascular diseases, mood disorders, endometrial cancer and non-alcoholic fatty liver disease. Although various susceptibility loci have been identified through genetic studies, they account for ∼10% of PCOS heritability. Therefore, the etiology of PCOS remains unclear. This review explores the role of epigenetic changes and modifications in circadian clock genes as potential contributors to PCOS pathogenesis. Epigenetic alterations, such as DNA methylation, histone modifications, and non-coding RNA changes, have been described in diseases related to PCOS, such as diabetes, cardiovascular diseases, and obesity. Furthermore, several animal models have illustrated a link between prenatal exposure to androgens or anti-Müllerian hormone and PCOS-like phenotypes in subsequent generations, illustrating an epigenetic programming in PCOS. In humans, epigenetic changes have been reported in peripheral blood mononuclear cells (PBMC), adipose tissue, granulosa cells (GC), and liver from women with PCOS. The genome of women with PCOS is globally hypomethylated compared to healthy controls. However, specific hypomethylated or hypermethylated genes have been reported in the different tissues of these women. They are mainly involved in hormonal regulation and inflammatory pathways, as well as lipid and glucose metabolism. Additionally, sleep disorders are present in women with PCOS and disruptions in clock genes' expression patterns have been observed in their PBMC or GCs. While epigenetic changes hold promise as diagnostic biomarkers, the current challenge lies in distinguishing whether these changes are causes or consequences of PCOS. Targeting epigenetic modifications potentially opens avenues for precision medicine in PCOS, including lifestyle interventions and drug therapies. However, data are still lacking in large cohorts of well-characterized PCOS phenotypes. In conclusion, understanding the interplay between genetics, epigenetics, and circadian rhythms may provide valuable insights for early diagnosis and therapeutic strategies in PCOS in the future.

The circadian clock gene, BMAL1, promotes radiosensitization in nasopharyngeal carcinoma by inhibiting the epithelial-to-mesenchymal transition via the TGF-ß1/Smads/Snail1 axis.

Acquired radio-resistance is thought to be one of the main causes of recurrent metastasis after failure of nasopharyngeal carcinoma (NPC) radiotherapy, which may be related to X-ray-induced epithelial-mesenchymal transition (EMT) activation. The circadian clock gene, BMAL1, has been shown to correlate with the sensitivity of NPCs to radiotherapy, but the specific mechanism has not been reported. NPC cells were irradiated by conventional fractionation to generate radiotherapy-resistant cells. NPC cells with BMAL1 gene stabilization/overexpression and interference were obtained by lentiviral transfection. Western blotting, colony formation analysis, cell counting kit-8 assays, wound-healing tests, Transwell assays, flow cytometry, the EDU method, nuclear plasma separation experiments, HE staining, immunohistochemical staining and TUNEL staining were performed to explore the influence and molecular mechanism of the circadian clock gene, BMAL1, on NPC-acquired radio-resistance and EMT through in vitro and in vivo experiments. The results indicated that there was a gradual downregulation of BMAL1 gene protein expression during the routine dose induction of radio-resistance in NPC cells. EMT activation was present in the radiation-resistant cell line 5-8FR, and was accompanied by the significant enhancement of proliferation, migration and invasion. The BMAL1 gene significantly increased the radiosensitivity of the radiation-resistant cell line 5-8FR and reversed the acquired radio-resistance of NPCs, which was accomplished by inhibiting the TGF-ß1/Smads/Snail1 axis-mediated EMT.

The skin circadian clock gene F3 as a potential marker for psoriasis severity and its bidirectional relationship with IL-17 signaling in keratinocytes.

OBJECTIVE: Psoriasis is an immune-mediated skin disease where the IL-17 signaling pathway plays a crucial role in its development. Chronic circadian rhythm disorder in psoriasis pathogenesis is gaining more attention. The relationship between IL and 17 signaling pathway and skin clock genes remains poorly understood. METHODS: GSE121212 with psoriatic lesion and healthy controls was used as the exploration cohort for searching analysis. Datasets GSE54456, GSE13355, GSE14905, GSE117239, GSE51440, and GSE137218 were applied to validation analysis. Single-cell RNA sequencing (scRNA-seq) dataset GSE173706 was used to explore the F3 expression and related pathway activities in single-cell levels. Through intersecting with high-expression DEGs, F3 was selected as the signature skin circadian gene in psoriasis for further investigation. Functional analyses, including correlation analyses, prediction of transcription factors, protein-protein interaction, and single gene GSEA to explore the potential roles of F3. ssGSEA algorithm was performed to uncover the immune-related characteristics of psoriasis. We further explored F3 expression in the specific cell population in scRNA-seq dataset, besides this, AUCell analysis was performed to explore the pathway activities and the results were further compared between the specific cell cluster. Immunohistochemistry experiment, RT-qPCR was used to validate the location and expression of F3, small interfering RNA (siRNA) transfection experiment in HaCaT, and transcriptome sequencing analysis were applied to explore the potential function of F3. RESULTS: F3 was significantly down-regulated in psoriasis and interacted with IL-17 signaling pathway. Low expression of F3 could upregulate the receptor of JAK-STAT signaling, thereby promoting keratinocyte inflammation. CONCLUSION: Our research revealed a bidirectional link between the skin circadian gene F3 and the IL-17 signaling pathway in psoriasis, suggesting that F3 may interact with the IL-17 pathway by activating JAK-STAT within keratinocytes and inducing abnormal intracellular inflammation.

Identification and characterization of circadian clock genes in the head transcriptome of Conopomorpha sinensis Bradley.

Conopomorpha sinensis Bradley is the most detrimental pest to litchi and longan in China. Adult eclosion, locomotion, mating and oviposition of C. sinensis usually occur at night, regulated by a circadian rhythm. Nevertheless, our understanding of the linkages between adult circadian rhythms and clock genes remains inadequate. To address this gap, transcriptomic analysis was conducted on female and male heads (including antennae) of C. sinensis using the Illumina HiSeq 6000 platform to identify major circadian clock-related genes. The annotated sequences were analyzed by BLASTx, and candidate clock genes were classified based on conservation, predicted domain architectures, and phylogenetic analysis. The analysis revealed a higher conservation of these genes among the compared moths. Further, the expression profile analysis showed a significant spatiotemporal and circadian rhythmic accumulation of some clock genes during development. The candidate clock genes were predominantly expressed in the head, highlighting their crucial function in circadian rhythm regulation. Moreover, CsinPer, CsinTim1, and CsinCry1 displayed similar dynamic expressions with a peak expression level in the 4th age adults, suggesting their involvement in regulation of courtship and mating behaviors. The CsinPer and CsinTim1 mRNA oscillated strongly with a similar phase, containing a peak expression just before the female mating peak. This work will greatly contribute to understanding the circadian clock system of C. sinensis and provide valuable information for further studies of the molecular mechanisms involved in rhythmicity in fruit-boring pests.

Sleep and circadian rhythm disturbance in kidney stone disease: a narrative review.

The circadian rhythm generated by circadian clock genes functions as an internal timing system. Since the circadian rhythm controls abundant physiological processes, the circadian rhythm evolved in organisms is salient for adaptation to environmental change. A disturbed circadian rhythm is a trigger for numerous pathological events. Recently, accumulated data have indicated that kidney stone disease (KSD) is related to circadian rhythm disturbance. However, the mechanism between them has not been fully elucidated. In this narrative review, we summarized existing evidence to illustrate the possible association between circadian rhythm disturbance and KSD based on the epidemiological studies and risk factors that are linked to circadian rhythm disturbance and discuss some chronotherapies for KSD. In summary, KSD is associated with systemic disorders. Metabolic syndrome, inflammatory bowel disease, and microbiome dysbiosis are the major risk factors supported by sufficient data to cause KSD in patients with circadian rhythm disturbance, while others including hypertension, vitamin D deficiency, parathyroid gland dysfunction, and renal tubular damage/dysfunction need further investigation. Then, some chronotherapies for KSD were confirmed to be effective, but the molecular mechanism is still unclear.

Research progresses on the effects of heavy metals on the circadian clock system.

Environmental pollution with heavy metals is widespread, thus increasing attention has been paid to their toxic effects. Recent studies have suggested that heavy metals may influence the expression of circadian clock genes. Almost all organs and tissues exhibit circadian rhythms. The normal circadian rhythm of an organism is maintained by the central and peripheral circadian clock. Thus, circadian rhythm disorders perturb normal physiological processes. Here, we review the effects of heavy metals, including manganese, copper, cadmium, and lead, on four core circadian clock genes, i.e., ARNTL, CLOCK, PER, and CRY genes.

Gegen Qinlian Decoction treatment of asymptomatic hyperuricemia by targeting circadian immune function.

BACKGROUND: The Gegen Qinlian Decoction (GGQLD) is a renowned traditional Chinese medicinal formula that has been used for centuries to effectively treat asymptomatic Hyperuricemia (HUA). This study aims to investigate the underlying mechanism of GGQLD's therapeutic effects on HUA. METHODS: The study enrolled a total of 25 healthy participants and 32 middle-aged and elderly individuals with asymptomatic HUA. All asymptomatic HUA participants were treated with GGQLD. Venous blood samples were collected from all participants to isolate peripheral blood mononuclear cells (PBMCs), which were then analyzed for biological profiles using flow cytometry. Network pharmacology analysis was utilized to identify the potential pathways involved in the therapeutic effects of GGQLD. Transcriptomic patterns of cultured proximal tubule epithelial cells (PTECs) were evaluated via bulk RNA-seq, and critical differentially expressed genes (DEGs) were identified and verified through ELISA. Molecular docking and molecular dynamics (MD) simulation were employed to investigate the potential compounds in GGQLD that may be involved in treating HUA. RESULTS: Network pharmacology analysis revealed that immune-related pathways might be involved in the therapeutic mechanism of GGQLD. RNA-seq analysis confirmed the involvement of innate lymphoid cell (ILC) development-related genes and clock genes. Polychromatic flow cytometric analysis demonstrated that GGQLD treatment reduced the proportion of ILC3s in total ILCs in asymptomatic HUA patients. ELISA results showed that GGQLD treatment reduced the levels of activating factors, such as ILC3-IL-18 and IL-1ß, in the plasma of HUA patients. GGQLD was also found to regulate circadian clock gene expression in PBMCs to treat asymptomatic HUA. Furthermore, the interaction between 40 compounds in GGQLD and HDAC3 (Histone Deacetylase 3), NLRP3 (NOD-like receptor protein 3), RORA (RAR-related orphan receptor A), and REV-ERBα (nuclear receptor subfamily 1) revealed that GGQLD may regulate ILCs and clock genes to treat asymptomatic HUA. CONCLUSIONS: The regulation of circadian clock gene expression and the proportion of ILC cells may be involved in the therapeutic effects of GGQLD on asymptomatic HUA patients.

Clock gene NR1D1 might be a novel target for the treatment of bladder cancer.

PURPOSE: To explore the role of circadian clock gene NR1D1 (REV-erbα) in bladder cancer (BC). METHODS: Firstly, the association of NR1D1 level with clinical characteristics and prognosis was investigated among patients diagnosed with BC. Secondly, CCK-8, transwell, and colony formation experiments were performed among BC cells treated with Rev-erbα agonist (SR9009), as well as lentivirus and siRNA, for which NR1D1 were overexpressed (OE) and knocked down (KD), respectively. Thirdly, cell cycle and apoptosis were tested by flowcytometry. PI3K/AKT/mTOR pathway proteins were determined in OE-NR1D1 cells. Finally, OE-NR1D1 and OE-Control BC cells were subcutaneously implanted in BALB/c nude mice. The tumor size and protein levels were compared between groups. A P < 0.05 was considered as statistically significant. RESULTS: Patients with NR1D1 positive status had a longer disease-free survival than those with negative expression. The cell viability, migration, and colony formation of BC cells after treated with SR9009 were significantly suppressed. OE-NR1D1 cells had obviously inhibited cell viability, migration, and colony formation, while those were found strengthened in KD-NR1D1 cells. Besides, KD-NR1D1 cells were observed with a lower proportion of dead cells and G0/G1 cells, but a higher ratio of G2/M. The changes of p-AKT, p-S6, p-4EBP1, and FASN involved in PI3K/AKT/mTOR pathway were detected in OE- and KD-NR1D1 BC cells. Finally, in vivo data demonstrated that overexpression of NR1D1 suppressed the tumorigenicity of BC cells. CONCLUSION: NR1D1 played a role of tumor suppressor and it might become a novel target for the treatment of BC.

Circadian clock genes as promising therapeutic targets for bone loss.

The circadian clock regulates many key physiological processes such as the sleep-wake cycle, hormone release, cardiovascular health, glucose metabolism and body temperature. Recent evidence has suggested a critical role of the circadian system in controlling bone metabolism. Here we review the connection between bone metabolism and the biological clock, and the roles of these mechanisms in bone loss. We also analyze the regulatory effects of clock-related genes on signaling pathways and transcription factors in osteoblasts and osteoclasts. Additionally, osteocytes and endothelial cells (ECs) regulated by the circadian clock are also discussed in our review. Furthermore, we also summarize the regulation of circadian clock genes by some novel modulators, which provides us with a new insight into a potential strategy to prevent and treat bone diseases such as osteoporosis by targeting circadian genes.

Expression of the Circadian Clock Gene ARNTL associated with DNA repair gene and prognosis of patient with osteosarcoma.

PURPOSE: The study objects were to explore the correlation between the biological role of clock genes and clinical indicators in patients with osteosarcoma (OS). METHODS: We acquired the clinical information and RNA sequencing data of OS samples from the TARGET database. The protein-protein interaction (PPI) network and expression correlation analysis of clock genes were performed. Then, the functional enrichment analysis of clock genes was analyzed. The survival analysis of clock genes in patients of OS was carried out by univariate cox regression, Kaplan-Meier (KM) curve and multivariate cox regression methods. Moreover, the spearmen correlation analysis was performed to explore the correlation between clock genes and DNA repair genes in patients with OS. RESULTS: The PPI network and expression correlation analysis of clock genes indicated that the clock genes were highly correlated with each other. The survival analysis of clock genes found that clock gene ARNTL is a protective factor for the prognosis of patients with OS. We found that ARNTL was positively related to DNA repair genes and was involved in the biological process of DNA damage repair in patients with OS. CONCLUSIONS: ARNTL may affect the prognosis and chemotherapy response of patients with OS by regulating DNA repair pathways.

RTN2, a new member of circadian clock genes identified by database mining and bioinformatics prediction, is highly expressed in ovarian cancer.

Increasing evidence suggests that core circadian genes have major roles in the carcinogenic mechanisms of multiple human malignancies. Among these genes, the role of reticulon 2 (RTN2) in ovarian cancer (OV) has so far remained elusive. In the present study, circadian clock gene (CCG) aberrations were systematically assessed across malignancies by using Gene Expression Omnibus and The Cancer Genome Atlas data. The results indicated that various core clock genes (ULK1, ATF3, CRY2, CSF3R, DAAM2, GAS7, NPTXR, PPPIR15A and RTN2) had elevated levels in tumors in comparison with normal tissues and their low expression levels were associated with a better prognosis in OV, indicating that they may be potential candidates for novel investigational approaches. The mRNA and protein expression levels of RTN2 in OV were then further analyzed by reverse transcription­quantitative PCR and immunohistochemistry, respectively. The results indicated that RTN2 mRNA and protein levels were increased in OV specimens in comparison with control samples. Differentially expressed CCGs, such as RTN2, were suggested as indicators of asynchronous circadian rhythms in cancer, which may provide a theoretical basis for chrono­therapy.

Influences of the Interactions of Genetic Variations of Seven Core Circadian Clock Genes with Lifestyle Factors on Metabolic Parameters.

INTRODUCTION: In mammals, circadian rhythms regulate many behavioral and physiological processes. Genetic and epidemiological studies have shown that dysregulation of the circadian rhythm induces chronic metabolic diseases, such as obesity, diabetes, and dyslipidemia. We aimed to know the interactions of genetic variations of seven core circadian clock genes with lifestyle factors on the determination of metabolic parameters. METHODS: We have analyzed the impacts of genotype of seven core circadian clock genes (i.e., CLOCK, BMAL1, PER1, PER2, PER3, CRY1, and CRY2) and lifestyle factors (i.e., physical activity and sleep duration) in 575 Japanese males on the determination of metabolic parameters (i.e., body mass index [BMI], serum glucose, glycated hemoglobin [HbA1c], low-density lipoprotein cholesterol [LDL-C], and high-density lipoprotein cholesterol [HDL-C] levels). RESULTS: We have detected the associations between genotypes of PER3 and serum HbA1c level and genotypes of CRY1 and serum LDL-C level. Additionally, the interactions of the genotypes of PER1 and PER3 with physical activity for determining BMI, the genotypes of CLOCK with physical activity for determining serum HbA1c levels were observed. Furthermore, for determining serum HDL-C levels, the interactions of the genotypes of CRY2 with physical activity or sleep duration were observed. DISCUSSION/CONCLUSION: Our findings indicate that the interactions of genotypes for core circadian clock genes and lifestyle factors (i.e., physical activity and sleep duration) are important for determining metabolic parameters.

Gene-environment interaction between circadian clock gene polymorphisms and job stress on the risk of sleep disturbances.

RATIONALE: Sleep disturbances was associated with numerous adverse health outcomes. Many studies have reported that long-term exposure to job stress can lead to sleep disturbances, which may be influenced by genetic and environmental factors. OBJECTIVES: This cross-sectional study investigated whether circadian clock gene polymorphisms modulated the influence of job stress on sleep disturbances in a Chinese Han population, which to our best knowledge has not been explored. METHODS: The Effort-Reward Imbalance (ERI) scale and the Pittsburgh Sleep Quality Index (PSQI) were both used to access job stress and sleep disturbances. The SNaPshot SNP assay was carried out by screening for circadian clock gene polymorphisms in every participant. Interactions associated with sleep disturbances were assessed by linear hierarchical regression analysis and SPSS macros (PROCESS). RESULTS: Linear hierarchical regression analysis showed that job stress was significantly related to sleep disturbances. Likewise, our study found a significant effect of PER2 rs2304672 polymorphisms on sleep disturbances (p < 0.01), after controlling for confounding factors. In addition, the PER2 rs2304672 genotype modulated the relationship between job stress and sleep disturbances (ß = 0.414, p = 0.007). Interestingly, further analysis of the results of the PER2 gene rs2304672 × job stress interaction showed that rs2304672 G-allele carriers had a high-risk effect on sleep disturbances under high job stress. CONCLUSIONS: Our results suggest that the PER2 rs2304672 polymorphism may modulate the influence of job stress on sleep disturbances. These findings contribute to the field of sleep disturbances prevention and treatment.

Co-regulation of circadian clock genes and microRNAs in bone metabolism.

Mammalian bone is constantly metabolized from the embryonic stage, and the maintenance of bone health depends on the dynamic balance between bone resorption and bone formation, mediated by osteoclasts and osteoblasts. It is widely recognized that circadian clock genes can regulate bone metabolism. In recent years, the regulation of bone metabolism by non-coding RNAs has become a hotspot of research. MicroRNAs can participate in bone catabolism and anabolism by targeting key factors related to bone metabolism, including circadian clock genes. However, research in this field has been conducted only in recent years and the mechanisms involved are not yet well established. Recent studies have focused on how to target circadian clock genes to treat some diseases, such as autoimmune diseases, but few have focused on the co-regulation of circadian clock genes and microRNAs in bone metabolic diseases. Therefore, in this paper we review the progress of research on the co-regulation of bone metabolism by circadian clock genes and microRNAs, aiming to provide new ideas for the prevention and treatment of bone metabolic diseases such as osteoporosis.

Identification and Characterization of PSEUDO-RESPONSE REGULATOR (PRR) 1a and 1b Genes by CRISPR/Cas9-Targeted Mutagenesis in Chinese Cabbage (Brassica rapa L.).

The CRISPR/Cas9 site-directed gene-editing system offers great advantages for identifying gene function and crop improvement. The circadian clock measures and conveys day length information to control rhythmic hypocotyl growth in photoperiodic conditions, to achieve optimal fitness, but operates through largely unknown mechanisms. Here, we generated core circadian clock evening components, Brassica rapa PSEUDO-RESPONSE REGULATOR (BrPRR) 1a, 1b, and 1ab (both 1a and 1b double knockout) mutants, using CRISPR/Cas9 genome editing in Chinese cabbage, where 9-16 genetic edited lines of each mutant were obtained. The targeted deep sequencing showed that each mutant had 2-4 different mutation types at the target sites in the BrPRR1a and BrPRR1b genes. To identify the functions of BrPRR1a and 1b genes, hypocotyl length, and mRNA and protein levels of core circadian clock morning components, BrCCA1 (CIRCADIAN CLOCK-ASSOCIATED 1) and BrLHY (LATE ELONGATED HYPOCOTYL) a and b were examined under light/dark cycles and continuous light conditions. The BrPRR1a and 1ab double mutants showed longer hypocotyls, lower core circadian clock morning component mRNA and protein levels, and a shorter circadian rhythm than wildtype (WT). On the other hand, the BrPRR1b mutant was not significantly different from WT. These results suggested that two paralogous genes may not be associated with the same regulatory function in Chinese cabbage. Taken together, our results demonstrated that CRISPR/Cas9 is an efficient tool for achieving targeted genome modifications and elucidating the biological functions of circadian clock genes in B. rapa, for both breeding and improvement.

Circadian clock gene BMAL1 inhibits the proliferation and tumor-formation ability of nasopharyngeal carcinoma cells and increases the sensitivity of radiotherapy.

BMAL1 is a core circadian clock gene that is expressed rhythmically in a variety of tumor cells and is related to cancer cell proliferation and chemoradiotherapy sensitivity. Radiotherapy plays an important role in the treatment of nasopharyngeal carcinoma (NPC). However, the rhythmicity of BMAL1 in NPC, as well as its precise role in radiotherapy, remains unclear. We assessed changes in BMAL1 expression over 48 h in NPC cells and normal nasopharyngeal epithelial cells NP69 using real-time quantitative polymerase chain reaction (RT-PCR) and western blotting (WB). Then, we induced the overexpression and knocked-down the levels of BMAL1 in NPC cells, and subsequently used Cell Counting Kit-8 assays to assess the proliferation of NPC cells. Xenograft tumour growth was used to evaluate the effect of BMAL1 in vivo. Immunohistochemical staining was used to detect the expression of BMAL1 protein in transplanted tumors. Gene Set Enrichment Analysis (GSEA) was performed to explore the biological signaling pathway. Finally, RT-PCR and WB were used to detect the expressions of BMAL1, p53 and p21. The results showed that the mRNA expression levels of circadian clock gene BMAL1 fluctuated rhythmically with time, and the expression levels of BMAL1 also changed depending on the protein levels in NPC and NP69 cells. Overexpression of BMAL1 inhibited the proliferation of NPC cells, while knockdown BMAL1 had the opposite effects. In a xenograft model, we observed that the upregulation of BMAL1 inhibited tumor growth and enhanced the sensitivity of NPC cells to radiotherapy. Ultimately, the downregulation of BMAL1 promoted tumor growth and decreased radiosensitivity. GSEA analysis suggested that BMAL1 significantly affected the p53 pathway. Overexpression of BMAL1 promoted the expression of p53 and p21, while the knockdown of BMAL1 inhibited the expression of p53 and p21. We speculate that BMAL1 has the potential to be a prognostic biomarker and therapeutic target for NPC.

Co-regulation of circadian clock genes and microRNAs in bone metabolism / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Mammalian bone is constantly metabolized from the embryonic stage, and the maintenance of bone health depends on the dynamic balance between bone resorption and bone formation, mediated by osteoclasts and osteoblasts. It is widely recognized that circadian clock genes can regulate bone metabolism. In recent years, the regulation of bone metabolism by non-coding RNAs has become a hotspot of research. MicroRNAs can participate in bone catabolism and anabolism by targeting key factors related to bone metabolism, including circadian clock genes. However, research in this field has been conducted only in recent years and the mechanisms involved are not yet well established. Recent studies have focused on how to target circadian clock genes to treat some diseases, such as autoimmune diseases, but few have focused on the co-regulation of circadian clock genes and microRNAs in bone metabolic diseases. Therefore, in this paper we review the progress of research on the co-regulation of bone metabolism by circadian clock genes and microRNAs, aiming to provide new ideas for the prevention and treatment of bone metabolic diseases such as osteoporosis.

Circadian Clock Gene Polymorphisms and Sleep-Onset Problems in a Population-Based Cohort Study: The Yamagata Study.

A number of genome-wide association studies have investigated sleep phenotypes and disorders in humans. However, the contribution of genetic variation to sleep problems in Japanese populations has remained unclear. Sleep-onset problems are the most common symptom of insomnia. Here, we examined the relationship between single nucleotide polymorphisms (SNPs) of BMAL1 (ARNTL1), CLOCK, CRY1, CRY2, and PER2, which are genes involved in the clock mechanism, and sleep-onset problems in a Japanese general population. This study included 1,397 subjects aged ≥ 40 years who participated in an annual health check-up in Yamagata Prefecture. A total of 80 SNPs of 5 circadian clock genes were analyzed. Multivariate logistic regression analyses identified variant rs11113179 in CRY1 and variants rs1026071 and rs1562438 in BMAL1 as genetic risk factors for sleep induction disorder. These findings suggest that CRY1 and BMAL1 polymorphisms are related to sleep-onset problems in a Japanese general population. However, none of the SNPs remained significant at a stringent level of multiple correction.

Enhanced Circadian Clock in MSCs-Based Cytotherapy Ameliorates Age-Related Temporomandibular Joint Condyle Degeneration.

Aging has been proven to be one of the major causes of temporomandibular joint (TMJ) disability and pain in older people. Peripheral circadian rhythms play a crucial role in endochondral ossification and chondrogenesis. However, the age-related alterations of circadian clock in TMJ structures are seldom reported. In the current study, TMJ condyles were extracted from young (4-month-old), middle-aged (10-month-old), and old-aged (20-month-old) adults to detect the morphology and circadian oscillation changes in TMJ condyles with aging. The transcriptome profile of Bmal1-deleted bone-marrow mesenchymal stem cells (BMSCs) and controls were explored to reveal the circadian-related differences at the molecular level. Furthermore, the reparative effects of Bmal1-overexpressed BMSCs-based cytotherapy in aged TMJ condyles were investigated in vitro and in vivo. Aged TMJ condyles displayed damaged tissue structure and an abolished circadian rhythm, accompanied by a progressively decreasing chondrogenesis capability and bone turnover activities. The deletion of Bmal1 significantly down-regulated chondrogenesis-related genes Prg4, Sox9, and Col7a1. Bmal1-overexpressed BMSCs presented improved migration capability ex vivo and attenuated age-related TMJ condylar degeneration in vivo. These data demonstrate the crucial role of circadian timing in the maintenance of osteochondral homeostasis, and indicate the potential clinical prospects of circadian-modified MSCs therapy in tissue regeneration.