Dnmt3a Regulates Proliferation of Muscle Satellite Cells via p57Kip2

Dnmt3a overexpression disrupts skeletal muscle homeostasis, promotes an aging-like phenotype, and reduces metabolic elasticity

Mammalian aging is reportedly driven by the loss of epigenetic information; however, its impact on skeletal muscle aging remains unclear. This study shows that aging mouse skeletal muscle exhibits increased DNA methylation, and overexpression of DNA methyltransferase 3a (Dnmt3a) induces an aging-like phenotype. Muscle-specific Dnmt3a overexpression leads to an increase in central nucleus-positive myofibers, predominantly in fast-twitch fibers, a shift toward slow-twitch fibers, elevated inflammatory and senescence markers, mitochondrial OXPHOS complex I reduction, and decreased basal autophagy. Dnmt3a overexpression resulted in reduced muscle mass and strength and impaired endurance exercise capacity with age, accompanied by an enhanced inflammatory signature. In addition, Dnmt3a overexpression reduced not only sensitivity to starvation-induced muscle atrophy but also the restorability from muscle atrophy. These findings suggest that increased DNA methylation disrupts skeletal muscle homeostasis, promotes an aging-like phenotype, and reduces muscle metabolic elasticity.

Metabolic regulation in adult and aging skeletal muscle stem cells

Adult stem cells maintain homeostasis and enable regeneration of most tissues. Quiescence, proliferation, and differentiation of stem cells and their progenitors are tightly regulated processes governed by dynamic transcriptional, epigenetic, and metabolic programs. Previously thought to merely reflect a cell's energy state, metabolism is now recognized for its critical regulatory functions, controlling not only energy and biomass production but also the cell's transcriptome and epigenome. In this review, we explore how metabolic pathways, metabolites, and transcriptional and epigenetic regulators are functionally interlinked in adult and aging skeletal muscle stem cells.

Tissue-specific roles of de novo DNA methyltransferases

DNA methylation, catalyzed by DNA methyltransferases (DNMT), plays pivotal role in regulating embryonic development, gene expression, adaption to environmental stress, and maintaining genome integrity. DNMT family consists of DNMT1, DNMT3A, DNMT3B, and the enzymatically inactive DNMT3L. DNMT3A and DNMT3B establish novel methylation patterns maintained by DNMT1 during replication. Genetic variants of DNMT3A and DNMT3B cause rare diseases such as Tatton-Brown-Rahman and ICF syndromes. Additionally, somatic mutations cause common conditions such as osteoarthritis, osteoporosis, clonal hematopoiesis of indeterminate potential (CHIP), hematologic malignancies, and cancer. While DNMTs have been extensively studied in vitro, in early development and in disease, their detailed physiologic roles remain less understood as in vivo investigations are hindered by the embryonic or perinatal lethality of the knockout mice. To circumvent this problem, tissue-specific Dnmt3a and Dnmt3b knockouts were engineered. This review explores their diverse molecular roles across various organs and cell types and characterizes the phenotype of the knockout mice. We provide a comprehensive collection of over forty tissue-specific knockout models generated by cre recombinase. We highlight the distinct functions of DNMT3A and DNMT3B in germ cells, early development, uterus, hematopoietic differentiation, musculoskeletal development, visceral organs, and nervous system. Our findings indicate that DNMT3A primarily regulates hematopoietic differentiation, while DNMT3B is crucial for cartilage homeostasis and ossification. We emphasize the context-dependent roles of DNMT3A and DNMT3B and demonstrate that they also complement DNMT1 maintenance methyltransferase activity. Overall, the expression patterns of DNMTs across tissues provide insights into potential therapeutic applications for treating neurologic diseases, cancer, and osteoporosis.

Epigenetic regulation of myogenesis by vitamin C

The micronutrient vitamin C is essential for the maintenance of skeletal muscle health and homeostasis. The pro-myogenic effects of vitamin C have long been attributed to its role as a general antioxidant agent, as well as its role in collagen matrix synthesis and carnitine biosynthesis. Here, we show that vitamin C also functions as an epigenetic compound, facilitating chromatin landscape transitions during myogenesis through its activity as an enzymatic cofactor for histone H3 and DNA demethylation. Utilizing C2C12 myoblast cells to investigate the epigenetic effects of vitamin C on myogenesis, we observe that treatment of cells with vitamin C decreases global H3K9 methylation and increases 5-hmC levels. Furthermore, vitamin C treatment enhances myoblast marker gene expression and myotube formation during differentiation. We identify KDM7A as a histone lysine demethylase markedly upregulated during myogenesis. Accordingly, knockdown of Kdm7a prevents the pro-myogenic effects of vitamin C. Chromatin immunoprecipitation analysis showed that KDM7A occupies the promoter region of the myogenic transcription factor MyoD1 where it facilitates histone demethylation. We also confirm that the methylcytosine dioxygenases TET1 and TET2 are required for myogenic differentiation and that their loss blunts stimulation of myogenesis by vitamin C. In conclusion, our data suggest that an epigenetic mode of action plays a major role in the myogenic effects of vitamin C.

E-box independent chromatin recruitment turns MYOD into a transcriptional repressor

MYOD is an E-box sequence-specific basic Helix-Loop-Helix (bHLH) transcriptional activator that, when expressed in non-muscle cells, induces nuclear reprogramming toward skeletal myogenesis by promoting chromatin accessibility at previously silent loci. Here, we report on the identification of a previously unrecognized property of MYOD as repressor of gene expression, via E-box-independent chromatin binding within accessible genomic elements, which invariably leads to reduced chromatin accessibility. MYOD-mediated repression requires the integrity of functional domains previously implicated in MYOD-mediated activation of gene expression. Repression of mitogen- and growth factor-responsive genes occurs through promoter binding and requires a highly conserved domain within the first helix. Repression of cell-of-origin/alternative lineage genes occurs via binding and decommissioning of distal regulatory elements, such as super-enhancers (SE), which requires the N-terminal activation domain as well as two chromatin-remodeling domains and leads to reduced strength of CTCF-mediated chromatin interactions. Surprisingly, MYOD-mediated chromatin compaction and repression of transcription do not associate with reduction of H3K27ac, the conventional histone mark of enhancer or promoter activation, but with reduced levels of the recently discovered histone H4 acetyl-methyl lysine modification (Kacme). These results extend MYOD biological properties beyond the current dogma that restricts MYOD function to a monotone transcriptional activator and reveal a previously unrecognized functional versatility arising from an alternative chromatin recruitment through E-box or non-E-box sequences. The E-box independent repression of gene expression by MYOD might provide a promiscuous mechanism to reduce chromatin accessibility and repress cell-of-origin/alternative lineage and growth factor/mitogen-responsive genes to safeguard the integrity of cell identity during muscle progenitor commitment toward the myogenic lineage.

Epigenetic control of skeletal muscle atrophy

Skeletal muscular atrophy is a complex disease involving a large number of gene expression regulatory networks and various biological processes. Despite extensive research on this topic, its underlying mechanisms remain elusive, and effective therapeutic approaches are yet to be established. Recent studies have shown that epigenetics play an important role in regulating skeletal muscle atrophy, influencing the expression of numerous genes associated with this condition through the addition or removal of certain chemical modifications at the molecular level. This review article comprehensively summarizes the different types of modifications to DNA, histones, RNA, and their known regulators. We also discuss how epigenetic modifications change during the process of skeletal muscle atrophy, the molecular mechanisms by which epigenetic regulatory proteins control skeletal muscle atrophy, and assess their translational potential. The role of epigenetics on muscle stem cells is also highlighted. In addition, we propose that alternative splicing interacts with epigenetic mechanisms to regulate skeletal muscle mass, offering a novel perspective that enhances our understanding of epigenetic inheritance's role and the regulatory network governing skeletal muscle atrophy. Collectively, advancements in the understanding of epigenetic mechanisms provide invaluable insights into the study of skeletal muscle atrophy. Moreover, this knowledge paves the way for identifying new avenues for the development of more effective therapeutic strategies and pharmaceutical interventions.

Higher dietary methyl donor micronutrient consumption is associated with higher muscle strength in adults: a cross-sectional study

Methyl donor micronutrients might affect muscle strength via DNA methylation. We aimed to evaluate the combined relationship of dietary methyl donor micronutrients containing betaine, choline, methionine, vitamin B12, vitamin B6 and folate on muscle strength. This cross-sectional study was conducted on 267 subjects including 113 men and 154 women. Dietary intake of micronutrients was assessed utilising a validated 168-item semi-quantitative FFQ, and methyl donor micronutrient score (MDMS) was calculated. The muscle strength of the participants was measured using a digital handgrip dynamometer. The association was determined using linear regression analysis. The mean age of participants was 36·8 ± 13·2 years. After taking into account potential confounding variables, there was no significant association between dietary methyl donor micronutrient score (MDMS) and the mean left-hand muscle strength (β: 0·07, se: 0·05, P = 0·07); however, the changes were significant in the mean right-hand muscle strength (β: 0·09, se: 0·04, P = 0·03). There was also a significant positive relationship between mean muscle strength and methyl donors' intake after fully adjusting for potential confounders (β: 0·08, se: 0·04, P = 0·04). In conclusion, our findings revealed that higher dietary methyl donor micronutrient consumption is associated with enhanced muscle strength. As a result, advice on a higher intake of methyl donor-rich foods including grains, nuts, dairy products and seafood might be recommended by dietitians as a general guideline to adhere to. Additional prospective studies are needed to confirm the findings.

CIP/KIP and INK4 families as hostages of oncogenic signaling

CIP/KIP and INK4 families of Cyclin-dependent kinase inhibitors (CKIs) are well-established cell cycle regulatory proteins whose canonical function is binding to Cyclin-CDK complexes and altering their function. Initial experiments showed that these proteins negatively regulate cell cycle progression and thus are tumor suppressors in the context of molecular oncology. However, expanded research into the functions of these proteins showed that most of them have non-canonical functions, both cell cycle-dependent and independent, and can even act as tumor enhancers depending on their posttranslational modifications, subcellular localization, and cell state context. This review aims to provide an overview of canonical as well as non-canonical functions of CIP/KIP and INK4 families of CKIs, discuss the potential avenues to promote their tumor suppressor functions instead of tumor enhancing ones, and how they could be utilized to design improved treatment regimens for cancer patients.

Expanding the phenotype of DNMT3A as a cause a congenital myopathy with rhabdomyolysis

Pathogenic variants in DNMT3A are most commonly associated with Tatton-Brown-Rahman Syndrome (TBRS), but includes other phenotypes such as Heyn-Sproul-Jackson syndrome and acute myeloid leukemia (AML). We describe a patient presenting to the neuromuscular clinic with a de novo missense variant in DNMT3A where the striking clinical feature is that of a congenital myopathy with associated episodes of rhabdomyolysis, severe myalgias and chest pain along with phenotypic features associated with TBRS. Muscle biopsy showed minor myopathic features and cardiac investigations revealed mildly impaired bi-ventricular systolic function. We confirmed the DNA methylation profile matched haplo-insufficient TBRS cases, consistent with a loss of methyltransferase activity. Our report emphasizes the phenotypic overlap of patients with syndromic disorders presenting to neuromuscular clinics and limitations of gene panels in establishing a molecular diagnosis.

Muscle injury causes long-term changes in stem-cell DNA methylation

Injury to muscle brings about the activation of stem cells, which then generate new myocytes to replace damaged tissue. We demonstrate that this activation is accompanied by a dramatic change in the stem-cell methylation pattern that prepares them epigenetically for terminal myocyte differentiation. These de- and de novo methylation events occur at regulatory elements associated with genes involved in myogenesis and are necessary for activation and regeneration. Local injury of one muscle elicits an almost identical epigenetic change in satellite cells from other muscles in the body, in a process mediated by circulating factors. Furthermore, this same methylation state is also generated in muscle stem cells (MuSCs) of female animals following pregnancy, even in the absence of any injury. Unlike the activation-induced expression changes, which are transient, the induced methylation profile is stably maintained in resident MuSCs and thus represents a molecular memory of previous physiological events that is probably programmed to provide a mechanism for long-term adaptation.

MicroRNA-381 Regulates Proliferation and Differentiation of Caprine Skeletal Muscle Satellite Cells by Targeting PTEN and JAG2

In our previous study, microRNA (miR)-381 was found to be the most down-regulated miRNA in skeletal muscle of Liaoning cashmere goats with higher skeletal muscle mass, but the molecular mechanism involved remains unclear. In this study, primary caprine skeletal muscle satellite cells (SMSCs) were isolated and identified. We investigated the effect of miR-381 on the viability, proliferation and differentiation of caprine SMSCs, and the target relationships of miR-381 with jagged canonical Notch ligand 2 (JAG2) and phosphatase and tensin homolog (PTEN). Cells isolated were positive for SMSC-specific marker protein Pax7. This suggests that purified SMSCs were obtained. The expression level of miR-381 achieved a peak value on day 4 after SMSC differentiation, and miR-381 also significantly increased the expression levels of myogenic differentiation marker genes: myosin heavy chain (MyHC), myogenin (MyoG) and myocyte enhancer factor 2C (MEF2C) in differentiated SMSCs, the area of MyHC-positive myotubes and the myogenic index. These findings suggest that miR-381 promoted myogenic differentiation of caprine SMSCs. The CCK8 assay and EDU staining analysis showed that miR-381 mimic both inhibited the viability of SMSCs and decreased the percentage of EDU-labeled positive SMSCs. In contrast, miR-381 inhibitor had the opposite effect with miR-381 mimic. A dual luciferase reporter assay verified that miR-381 can target JAG2 and PTEN by binding to the 3′-untranslated regions (3′-UTR) of the genes. The transfection of miR-381 mimic into caprine SMSCs resulted in decreases in expression levels of JAG2 and PTEN, while miR-381 inhibitor increased the two target genes in expression. This is the first study to reveal the biological mechanisms by which miR-381 regulates caprine SMSC activities.

Skeletal Muscle Regeneration in Cardiotoxin-Induced Muscle Injury Models

Skeletal muscle injuries occur frequently in daily life and exercise. Understanding the mechanisms of regeneration is critical for accelerating the repair and regeneration of muscle. Therefore, this article reviews knowledge on the mechanisms of skeletal muscle regeneration after cardiotoxin-induced injury. The process of regeneration is similar in different mouse strains and is inhibited by aging, obesity, and diabetes. Exercise, microcurrent electrical neuromuscular stimulation, and mechanical loading improve regeneration. The mechanisms of regeneration are complex and strain-dependent, and changes in functional proteins involved in the processes of necrotic fiber debris clearance, M1 to M2 macrophage conversion, SC activation, myoblast proliferation, differentiation and fusion, and fibrosis and calcification influence the final outcome of the regenerative activity.

D. P, C. M, M. LI, C. D, G. P, D. C, A. T, M. G, S. DF, M. T, V. V, G. S. Targeting epigenetic alterations in cancer stem cells

Oncogenes or tumor suppressor genes are rarely mutated in several pediatric tumors and some early stage adult cancers. This suggests that an aberrant epigenetic reprogramming may crucially affect the tumorigenesis of these tumors. Compelling evidence support the hypothesis that cancer stem cells (CSCs), a cell subpopulation within the tumor bulk characterized by self-renewal capacity, metastatic potential and chemo-resistance, may derive from normal stem cells (NSCs) upon an epigenetic deregulation. Thus, a better understanding of the specific epigenetic alterations driving the transformation from NSCs into CSCs may help to identify efficacious treatments to target this aggressive subpopulation. Moreover, deepening the knowledge about these alterations may represent the framework to design novel therapeutic approaches also in the field of regenerative medicine in which bioengineering of NSCs has been evaluated. Here, we provide a broad overview about: 1) the role of aberrant epigenetic modifications contributing to CSC initiation, formation and maintenance, 2) the epigenetic inhibitors in clinical trial able to specifically target the CSC subpopulation, and 3) epigenetic drugs and stem cells used in regenerative medicine for cancer and diseases.

From cyclins to CDKIs: Cell cycle regulation of skeletal muscle stem cell quiescence and activation

After extensive proliferation during development, the adult skeletal muscle cells remain outside the cell cycle, either as post-mitotic myofibers or as quiescent muscle stem cells (MuSCs). Despite its terminally differentiated state, adult skeletal muscle has a remarkable regeneration potential, driven by MuSCs. Upon injury, MuSC quiescence is reversed to support tissue growth and repair and it is re-established after the completion of muscle regeneration. The distinct cell cycle states and transitions observed in the different myogenic populations are orchestrated by elements of the cell cycle machinery. This consists of i) complexes of cyclins and Cyclin-Dependent Kinases (CDKs) that ensure cell cycle progression and ii) their negative regulators, the Cyclin-Dependent Kinase Inhibitors (CDKIs). In this review we discuss the roles of these factors in developmental and adult myogenesis, with a focus on CDKIs that have emerging roles in stem cell functions.

Integrated Analyses of DNA Methylation and Gene Expression of Rainbow Trout Muscle under Variable Ploidy and Muscle Atrophy Conditions

Rainbow trout, Oncorhynchus mykiss, is an important cool, freshwater aquaculture species used as a model for biological research. However, its genome reference has not been annotated for epigenetic markers affecting various biological processes, including muscle growth/atrophy. Increased energetic demands during gonadogenesis/reproduction provoke muscle atrophy in rainbow trout. We described DNA methylation and its associated gene expression in atrophying muscle by comparing gravid, diploid females to sterile, triploid females. Methyl Mini-seq and RNA-Seq were simultaneously used to characterize genome-wide DNA methylation and its association with gene expression in rainbow trout muscle. Genome-wide enrichment in the number of CpGs, accompanied by depleted methylation levels, was noticed around the gene transcription start site (TSS). Hypermethylation of CpG sites within ±1 kb on both sides of TSS (promoter and gene body) was weakly/moderately associated with reduced gene expression. Conversely, hypermethylation of the CpG sites in downstream regions of the gene body +2 to +10 kb was weakly associated with increased gene expression. Unlike mammalian genomes, rainbow trout gene promotors are poor in CpG islands, at <1% compared to 60%. No signs of genome-wide, differentially methylated (DM) CpGs were observed due to the polyploidy effect; only 1206 CpGs (0.03%) were differentially methylated, and these were primarily associated with muscle atrophy. Twenty-eight genes exhibited differential gene expression consistent with methylation levels of 31 DM CpGs. These 31 DM CpGs represent potential epigenetic markers of muscle atrophy in rainbow trout. The DM CpG-harboring genes are involved in apoptosis, epigenetic regulation, autophagy, collagen metabolism, cell membrane functions, and Homeobox proteins. Our study also identified genes explaining higher water content and modulated glycolysis previously shown as characteristic biochemical signs of rainbow trout muscle atrophy associated with sexual maturation. This study characterized DNA methylation in the rainbow trout genome and its correlation with gene expression. This work also identified novel epigenetic markers associated with muscle atrophy in fish/lower vertebrates.

DNMT1-Mediated DNA Methylation Targets CDKN2B to Promote the Repair of Retinal Ganglion Cells in Streptozotocin-Induced Mongolian Gerbils during Diabetic Retinopathy

Objective

DNA methylation played a vital role in the progression of diabetic retinopathy. In this study, we aimed to explore the role of DNA cytosine-5-methyltransferase 1 (DNMT1) in the development of early diabetic retinopathy and its potential underlying mechanism.

Methods

Eight-week-old healthy Mongolian gerbils were used to establish type 1 diabetes using streptozotocin (STZ). Alteration of weight, fasting blood glucose, density of RGCs (Tuj1-labeled), and H&E-stained retinal cross sections were applied to evaluate the diabetic retinopathy mouse model. The global DNA methylation level of the retina at different time points after STZ injection was measured using the global methylation assay. Western blot was used to detect the protein expression of DNMT1, DNA methyltransferase 3A (DNMT3A), and 3B (DNMT3B). Quantitative reverse transcription-polymerase chain reactions (qRT-PCR) and western blot were used to determine the expression of CDKN2B. Cell proliferation and cell cycle were evaluated by the MTS assay and flow cytometry.

Results

STZ injection caused the increased global DNA methylation level, which reached a maximum at 6 weeks after injection. Moreover, STZ injection caused the damage of RGCs. At 6 weeks after STZ injection, the expression levels of DNMT1 and DNMT3B were significantly increased in the STZ group. DNMT1-induced DNA hypermethylation inhibited the expression of CDKN2B (a negative regulator of cell cycle). DNMT1-mediated DNA methylation facilitated RGC proliferation via regulating the expression of CDKN2B.

Conclusion

DNMT1-mediated DNA methylation played an important role in STZ-induced diabetic retinopathy via modulating CDKN2B expression.

Uhrf1 governs the proliferation and differentiation of muscle satellite cells

DNA methylation is an essential form of epigenetic regulation responsible for cellular identity. In muscle stem cells, termed satellite cells, DNA methylation patterns are tightly regulated during differentiation. However, it is unclear how these DNA methylation patterns affect the function of satellite cells. We demonstrate that a key epigenetic regulator, ubiquitin like with PHD and RING finger domains 1 (Uhrf1), is activated in proliferating myogenic cells but not expressed in quiescent satellite cells or differentiated myogenic cells in mice. Ablation of Uhrf1 in mouse satellite cells impairs their proliferation and differentiation, leading to failed muscle regeneration. Uhrf1-deficient myogenic cells exhibited aberrant upregulation of transcripts, including Sox9, with the reduction of DNA methylation level of their promoter and enhancer region. These findings show that Uhrf1 is a critical epigenetic regulator of proliferation and differentiation in satellite cells, by controlling cell-type-specific gene expression via maintenance of DNA methylation.

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Uhrf1 is activated in proliferating myogenic cells

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Uhrf1 in satellite cells is required for muscle regeneration

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Ablation of Uhrf1 in satellite cells impairs their proliferation and differentiation

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Uhrf1 controls cell-type-specific transcripts via maintenance of DNA methylation

A Long Journey before Cycling: Regulation of Quiescence Exit in Adult Muscle Satellite Cells

Skeletal muscle harbors a pool of stem cells called muscle satellite cells (MuSCs) that are mainly responsible for its robust regenerative capacities. Adult satellite cells are mitotically quiescent in uninjured muscles under homeostasis, but they exit quiescence upon injury to re-enter the cell cycle to proliferate. While most of the expanded satellites cells differentiate and fuse to form new myofibers, some undergo self-renewal to replenish the stem cell pool. Specifically, quiescence exit describes the initial transition of MuSCs from quiescence to the first cell cycle, which takes much longer than the time required for subsequent cell cycles and involves drastic changes in cell size, epigenetic and transcriptomic profiles, and metabolic status. It is, therefore, an essential period indispensable for the success of muscle regeneration. Diverse mechanisms exist in MuSCs to regulate quiescence exit. In this review, we summarize key events that occur during quiescence exit in MuSCs and discuss the molecular regulation of this process with an emphasis on multiple levels of intrinsic regulatory mechanisms. A comprehensive understanding of how quiescence exit is regulated will facilitate satellite cell-based muscle regenerative therapies and advance their applications in various disease and aging conditions.

DNA methylation is associated with muscle loss in community-dwelling older men -the Yakumo study- : a preliminary experimental study

Frailty is a state of reduced muscle strength and activity in older people. DNA methylation is associated with osteoporosis and muscle loss in murine and other animal studies, but there are no epidemiological studies in humans. This study aimed to assess the association of osteoporosis and muscle loss with DNA methylation in community-dwelling older people. This cross-sectional study was performed in a rural part of Japan. We analyzed 204 subjects (98 men and 106 women). In univariate analysis, the two groups were compared according to the presence or absence of osteoporosis and of muscle loss. Logistic regression analysis was performed to determine predictors of frailty in the muscle loss group. We used age, sex, body mass index, smoking history, drinking history, serum albumin and C-reactive protein levels, diabetes, hypertension, hyperlipidemia, heart disease history, and LINE-1 DNA methylation as the factors. Probability values < 0.05 were considered to be statistically significant. The levels of LINE-1 DNA methylation in leukocytes were associated with muscle loss in men over the age of 60. LINE-1 DNA methylation levels were not associated with bone mineral density in either the men or women over the age of 60. LINE-1 DNA methylation levels in leukocytes correlated significantly with the risk of frailty in men over the age of 60. Promoting an understanding of DNA methylation may lead to a better understanding of the pathophysiology of muscle loss.

Tumor suppressor CEBPA interacts with and inhibits DNMT3A activity

DNA methyltransferases (DNMTs) catalyze DNA methylation, and their functions in mammalian embryonic development and diseases including cancer have been extensively studied. However, regulation of DNMTs remains under study. Here, we show that CCAAT/enhancer binding protein α (CEBPA) interacts with the long splice isoform DNMT3A, but not the short isoform DNMT3A2. CEBPA, by interacting with DNMT3A N-terminus, blocks DNMT3A from accessing DNA substrate and thereby inhibits its activity. Recurrent tumor-associated CEBPA mutations, such as preleukemic CEBPA^N321D mutation, which is particularly potent in causing AML with high mortality, disrupt DNMT3A association and cause aberrant DNA methylation, notably hypermethylation of PRC2 target genes. Consequently, leukemia cells with the CEBPA^N321D mutation are hypersensitive to hypomethylation agents. Our results provide insights into the functional difference between DNMT3A isoforms and the regulation of de novo DNA methylation at specific loci in the genome. Our study also suggests a therapeutic strategy for the treatment of CEBPA-mutated leukemia with DNA-hypomethylating agents.

Control of satellite cell function in muscle regeneration and its disruption in ageing

Skeletal muscle contains a designated population of adult stem cells, called satellite cells, which are generally quiescent. In homeostasis, satellite cells proliferate only sporadically and usually by asymmetric cell division to replace myofibres damaged by daily activity and maintain the stem cell pool. However, satellite cells can also be robustly activated upon tissue injury, after which they undergo symmetric divisions to generate new stem cells and numerous proliferating myoblasts that later differentiate to muscle cells (myocytes) to rebuild the muscle fibre, thereby supporting skeletal muscle regeneration. Recent discoveries show that satellite cells have a great degree of population heterogeneity, and that their cell fate choices during the regeneration process are dictated by both intrinsic and extrinsic mechanisms. Extrinsic cues come largely from communication with the numerous distinct stromal cell types in their niche, creating a dynamically interactive microenvironment. This Review discusses the role and regulation of satellite cells in skeletal muscle homeostasis and regeneration. In particular, we highlight the cell-intrinsic control of quiescence versus activation, the importance of satellite cell-niche communication, and deregulation of these mechanisms associated with ageing. The increasing understanding of how satellite cells are regulated will help to advance muscle regeneration and rejuvenation therapies.

The FOXM1/RNF26/p57 axis regulates the cell cycle to promote the aggressiveness of bladder cancer

Bladder cancer is one of the most lethal cancers in the world. Despite the continuous development of medical technologies and therapeutic strategies, the overall survival rate of bladder cancer has not changed significantly. Targeted therapy is a new promising method for bladder cancer treatment. Thus, an in-depth study of the molecular mechanism of the occurrence and development of bladder cancer is urgently needed to identify novel therapeutic candidates for bladder cancer. Here, bioinformatics analysis demonstrated that RNF26 was one of the risk factors for bladder cancer. Then, we showed that RNF26 is abnormally upregulated in bladder cancer cells and tissues and that higher RNF26 expression is an unfavorable prognostic factor for bladder cancer. Moreover, we found that RNF26 promotes bladder cancer progression. In addition, we showed that RNF26 expression is promoted by FOXM1 at the transcriptional level through MuvB complex. The upregulated RNF26 in turn degrades p57 (CDKN1C) to regulate the cell cycle process. Collectively, we uncovered a novel FOXM1/RNF26/p57 axis that modulates the cell cycle process and enhances the progression of bladder cancer. Thus, the FOXM1/RNF26/p57 signaling axis could be a candidate target for the treatment of bladder cancer.

Identification and Characterization of Novel circRNAs Involved in Muscle Growth of Blunt Snout Bream (Megalobrama amblycephala)

Circular RNAs (circRNAs), a novel class of endogenous RNAs, have been recognized to play important roles in the growth of animals. However, the regulatory mechanism of circRNAs on fish muscle growth is still unclear. In this study, we performed whole transcriptome analysis of skeletal muscles from two populations with different growth rates (fast-growing and slow-growing) of blunt snout bream (Megalobrama amblycephala), an important fish species for aquaculture. The selected circRNAs were validated by qPCR and Sanger sequencing. Pairs of circRNA–miRNA–mRNA networks were constructed with the predicted differentially expressed (DE) pairs, which revealed regulatory roles in muscle myogenesis and hypertrophy. As a result, a total of 445 circRNAs were identified, including 42 DE circRNAs between fast-growing (FG) and slow-growing (SG) groups. Many of these DE circRNAs were related with aminoglycan biosynthetic and metabolic processes, cytokinetic processes, and the adherens junction pathway. The functional prediction results showed that novel_circ_0001608 and novel_circ_0002886, competing to bind with dre-miR-153b-5p and dre-miR-124-6-5p, might act as competing endogenous RNAs (ceRNAs) to control MamblycephalaGene14755 (pik3r1) and MamblycephalaGene10444 (apip) level, respectively, thus playing an important regulatory role in muscle growth. Overall, these results will not only help us to further understand the novel RNA transcripts in M. amblycephala, but also provide new clues to investigate the potential mechanism of circRNAs regulating fish growth and muscle development.

Ablation of DNA-methyltransferase 3A in skeletal muscle does not affect energy metabolism or exercise capacity

In response to physical exercise and diet, skeletal muscle adapts to energetic demands through large transcriptional changes. This remodelling is associated with changes in skeletal muscle DNA methylation which may participate in the metabolic adaptation to extracellular stimuli. Yet, the mechanisms by which muscle-borne DNA methylation machinery responds to diet and exercise and impacts muscle function are unknown. Here, we investigated the function of de novo DNA methylation in fully differentiated skeletal muscle. We generated muscle-specific DNA methyltransferase 3A (DNMT3A) knockout mice (mD3AKO) and investigated the impact of DNMT3A ablation on skeletal muscle DNA methylation, exercise capacity and energy metabolism. Loss of DNMT3A reduced DNA methylation in skeletal muscle over multiple genomic contexts and altered the transcription of genes known to be influenced by DNA methylation, but did not affect exercise capacity and whole-body energy metabolism compared to wild type mice. Loss of DNMT3A did not alter skeletal muscle mitochondrial function or the transcriptional response to exercise however did influence the expression of genes involved in muscle development. These data suggest that DNMT3A does not have a large role in the function of mature skeletal muscle although a role in muscle development and differentiation is likely.

Skeletal muscle is a plastic tissue able to adapt to environmental stimuli such as exercise and diet in order to respond to energetic demand. One of the ways in which skeletal muscle can rapidly react to these stimuli is DNA methylation. This is when chemical groups are attached to DNA, potentially influencing the transcription of genes. We investigated the function of DNA methylation in skeletal muscle by generating mice that lacked one of the main enzymes responsible for de novo DNA methylation, DNA methyltransferase 3A (DNMT3A), specifically in muscle. We found that loss of DNMT3A reduced DNA methylation in muscle however this did not lead to differences in exercise capacity or energy metabolism. This suggests that DNMT3a is not involved in the adaptation of skeletal muscle to diet or exercise.

Epigenetic modifications in muscle regeneration and progression of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a multisystemic disorder that affects 1:5000 boys. The severity of the phenotype varies dependent on the mutation site in the DMD gene and the resultant dystrophin expression profile. In skeletal muscle, dystrophin loss is associated with the disintegration of myofibers and their ineffective regeneration due to defective expansion and differentiation of the muscle stem cell pool. Some of these phenotypic alterations stem from the dystrophin absence-mediated serine-threonine protein kinase 2 (MARK2) misplacement/downregulation in activated muscle stem (satellite) cells and neuronal nitric oxide synthase loss in cells committed to myogenesis. Here, we trace changes in DNA methylation, histone modifications, and expression of regulatory noncoding RNAs during muscle regeneration, from the stage of satellite cells to myofibers. Furthermore, we describe the abrogation of these epigenetic regulatory processes due to changes in signal transduction in DMD and point to therapeutic treatments increasing the regenerative potential of diseased muscles based on this acquired knowledge.

Epigenetic regulation of satellite cell fate during skeletal muscle regeneration

In response to muscle injury, muscle stem cells integrate environmental cues in the damaged tissue to mediate regeneration. These environmental cues are tightly regulated to ensure expansion of muscle stem cell population to repair the damaged myofibers while allowing repopulation of the stem cell niche. These changes in muscle stem cell fate result from changes in gene expression that occur in response to cell signaling from the muscle environment.

Integration of signals from the muscle environment leads to changes in gene expression through epigenetic mechanisms. Such mechanisms, including post-translational modification of chromatin and nucleosome repositioning, act to make specific gene loci more, or less, accessible to the transcriptional machinery. In youth, the muscle environment is ideally structured to allow for coordinated signaling that mediates efficient regeneration. Both age and disease alter the muscle environment such that the signaling pathways that shape the healthy muscle stem cell epigenome are altered. Altered epigenome reduces the efficiency of cell fate transitions required for muscle repair and contributes to muscle pathology. However, the reversible nature of epigenetic changes holds out potential for restoring cell fate potential to improve muscle repair in myopathies.

In this review, we will describe the current knowledge of the mechanisms allowing muscle stem cell fate transitions during regeneration and how it is altered in muscle disease. In addition, we provide some examples of how epigenetics could be harnessed therapeutically to improve regeneration in various muscle pathologies.

DNA maintenance methylation enzyme Dnmt1 in satellite cells is essential for muscle regeneration

Epigenetic transcriptional regulation is essential for the differentiation of various types of cells, including skeletal muscle cells. DNA methyltransferase 1 (Dnmt1) is responsible for maintenance of DNA methylation patterns via cell division. Here, we investigated the relationship between Dnmt1 and skeletal muscle regeneration. We found that Dnmt1 is upregulated in muscles during regeneration. To assess the role of Dnmt1 in satellite cells during regeneration, we performed conditional knockout (cKO) of Dnmt1 specifically in skeletal muscle satellite cells using Pax7CreERT2 mice and Dnmt1 flox mice. Muscle weight and the cross-sectional area after injury were significantly lower in Dnmt1 cKO mice than in control mice. RNA sequencing analysis revealed upregulation of genes involved in cell adhesion and apoptosis in satellite cells from cKO mice. Moreover, satellite cells cultured from cKO mice exhibited a reduced number of cells. These results suggest that Dnmt1 is an essential factor for muscle regeneration and is involved in positive regulation of satellite cell number.

Overexpression of Dnmt3a ameliorates diabetic muscle atrophy by modulating the Pten/Akt pathway

NEW FINDINGS

What is the central question of this study? Does Dnmt3a play a crucial role in regulating diabetic muscle atrophy? What is the main finding and its importance? Muscle atrophy is one of the major long-term complications of diabetes mellitus. However, little is known about the molecular mechanism involved. In this paper, we demonstrated that Dnmt3a overexpression effectively improves the diabetic muscle health in mice and documented the underlying mechanisms. DNMT3A might become a promising target to prevent muscle atrophy in patients with diabetes.

ABSTRACT

Muscle atrophy is one of the major long-term complications of diabetes mellitus, which greatly affects the mobility of patients. Epigenetic processes mediated by DNA methyltransferases (DNMTs) play crucial roles in the locomotor system, but little is known about the functions of DNMTs in diabetic muscle atrophy. Here, we investigated the function of Dnmt3a in diabetic muscle atrophy and explored the mechanisms involved. Adeno-associated virus AAV2 overexpressing Dnmt3a or its vector control was injected into the tibialis anterior muscle of streptozotocin-induced diabetic mice. Muscle mass and muscle cross-sectional area were used to evaluate muscle atrophy. In vitro, adeno-associated virus AAV2 overexpressing Dnmt3a or its vector control was transfected into C2C12 myoblasts. Horse serum was used to induce differentiation and palmitate to stimulate the C2C12 myoblasts. The expressions of myogenic regulatory factors were examined by real-time PCR and western blot analysis. Overexpression of Dnmt3a attenuated muscle atrophy in diabetic mice and promoted myotube formation of C2C12 myoblasts. Overexpression of Dnmt3a restored the expressions of myogenic regulatory factors atrogin-1, MuRF1, Pax7, Myod1 and myogenin, both in vivo and in vitro. Moreover, overexpression of Dnmt3a activated the phosphorylation of Akt by inhibiting the activation of Pten. This study demonstrates that overexpression of Dnmt3a prevents diabetic muscle atrophy by modulating the Pten/Akt pathway.

Comprehensive analysis of circular RNA profiles in skeletal muscles of aging mice and after aerobic exercise intervention

Aging induces gradual accumulation of damages in cells and tissues, which leads to physiological dysfunctions. Aging-associated muscle dysfunction is commonly seen in aged population and severely affects their physical activity and life quality, against which aerobic training has been shown to exert antagonizing or alleviating effects. Circular RNAs (circRNAs) play important roles in various physiological processes, yet their involvement in aging-associated muscle dysfunction is not well understood. In this study, we performed comprehensive analysis of circRNAs profiles in quadriceps muscles in sedentary young and aging mice, as well as aging mice with aerobic exercise using RNA sequencing. Our results identified circRNAs altered by factors of aging and aerobic exercise. Their host genes were then predicted and analyzed by gene ontology enrichment analysis. Importantly, we found that circBBS9 featured decreased levels in aging compared to young mice and elevated expression in exercise versus sedentary aging mice. Besides, we performed GO and KEGG analysis on circBBS9 target genes, as well as established the circBBS9-miRNA-mRNAs interaction network. Our results indicate that circBBS9 may play active roles in muscle aging by mediating the benefits of aerobic training intervention, thus may serve as a novel therapeutic target combating aging-associated muscle dysfunction.

Prognostic value of lncRNA FEZF1 antisense RNA 1 over-expression in oncologic outcomes of patients with solid tumors

BACKGROUND

FEZ family zinc finger 1 antisense RNA 1 (FEZF1-AS1), as a novel lncRNA, was reported to be up-regulated in various cancers and involved in tumor progression. This study systematically assessed the prognostic value of FEZF1-AS1 in solid tumors.

METHODS

Web of Science, PubMed, EMBASE, Chinese National Knowledge Infrastructure, and Wanfang databases were searched for eligible studies that evaluated the prognostic role of FEZF1-AS1 expression in cancer patients. Pooled hazard ratios (HRs) and combined odds ratios (ORs) with their 95% confidence intervals (CIs) were calculated. The meta-analysis was conducted using Stata/SE 14.1.

RESULTS

Fifteen original studies involving 1378 patients were enrolled. Pooled results showed that increased expression of FEZF1-AS1 significantly correlated with shorter overall survival (OS) in cancer patients (HR 2.04, 95% CI 1.60-2.47), and also shorter disease-free survival (DFS) (HR 2.08, 95% CI 1.27-2.89). Additionally, the combined ORs indicated that increased FEZF1-AS1 expression was significantly associated with lymph node metastasis (OR 3.35, 95% CI 1.98-5.67), distant metastasis (OR 3.10, 95% CI 1.86-5.15), poor tumor differentiation (OR 2.90, 95% CI 1.45-5.80), high depth of tumor invasion (OR 2.72, 95% CI 1.36-5.43), and advanced clinical stage (OR 2.76, 95% CI 1.75-4.35). Expression analysis using the Gene Expression Profiling Interactive Analysis database indicated that the expression of FEZF1-AS1 was higher in tumor tissues than that in the corresponding normal tissues. The results of survival analysis revealed that increased FEZF1-AS1 expression was correlated with poor OS and DFS in cancer patients.

CONCLUSIONS

LncRNA FEZF1-AS1 may serve as a valuable prognostic biomarker for clinical outcomes in various solid tumors.

Tailored chromatin modulation to promote tissue regeneration

Epigenetic regulation of gene expression is fundamental in the maintenance of cellular identity and the regulation of cellular plasticity during tissue repair. In fact, epigenetic modulation is associated with the processes of cellular de-differentiation, proliferation, and re-differentiation that takes place during tissue regeneration. In here we explore the epigenetic events that coordinate tissue repair in lower vertebrates with high regenerative capacity, and in mammalian adult stem cells, which are responsible for the homeostasis maintenance of most of our tissues. Finally we summarize promising CRISPR-based editing technologies developed during the last years, which look as promising tools to not only study but also promote specific events during tissue regeneration.

DNA Methylation Regulates Corneal Epithelial Wound Healing by Targeting miR-200a and CDKN2B

Purpose

DNA methylation is a key epigenetic modification involved in various biological processes and diseases. Corneal epithelial wound healing (CEWH) is essential for restoring corneal integrity and transparency after injury. However, the role of DNA methylation in CEWH remains elusive. Here, we investigate the function and underlying mechanism of DNA methylation in regulating CEWH.

Methods

Dot blots and global methylation assays determined DNA methylation levels during CEWH. Quantitative RT-PCR and Western blot analysis examined the expression of DNA methyltransferases (DNMTs), cyclin-dependent kinase inhibitor 2B (CDKN2B), and miR-200a during CEWH, respectively. MTS assays and flow cytometry were used to analyze human corneal epithelial cell (HCEC) proliferation and cell cycle, respectively. The in vitro scratch wound assay assessed HCEC migration and an in vivo murine corneal epithelial debridement model evaluated wound healing. Using bisulfite sequencing PCR, we determined the DNA methylation status of the candidate genes. Transfection of miR-200a mimic or inhibitor assessed the function of miR-200a in HCECs. Rescue experiments were performed to clarify the correlation between DNMT1 and miR-200a/CDKN2B during CEWH.

Results

DNMT1 and DNMT3B expression was significantly upregulated during CEWH, resulting in a significant global DNA hypermethylation. DNMT1 downregulation dramatically delayed CEWH in vivo, and suppressed HCEC proliferation and migration. MiR-200a inhibited HCEC migration. Furthermore, miR-200a and CDKN2B were identified as molecular targets of DNA methylation and as having a causal connection with DNMT1.

Conclusions

DNMT1-mediated DNA hypermethylation can enhance the process of CEWH by directly targeting miR-200a and CDKN2B. This insight pinpoints novel potential drug targets for promoting CEWH.

Cellular localization of the cell cycle inhibitor Cdkn1c controls growth arrest of adult skeletal muscle stem cells

Adult skeletal muscle maintenance and regeneration depend on efficient muscle stem cell (MuSC) functions. The mechanisms coordinating cell cycle with activation, renewal, and differentiation of MuSCs remain poorly understood. Here, we investigated how adult MuSCs are regulated by CDKN1c (p57^kip2), a cyclin-dependent kinase inhibitor, using mouse molecular genetics. In the absence of CDKN1c, skeletal muscle repair is severely impaired after injury. We show that CDKN1c is not expressed in quiescent MuSCs, while being induced in activated and proliferating myoblasts and maintained in differentiating myogenic cells. In agreement, isolated Cdkn1c-deficient primary myoblasts display differentiation defects and increased proliferation. We further show that the subcellular localization of CDKN1c is dynamic; while CDKN1c is initially localized to the cytoplasm of activated/proliferating myoblasts, progressive nuclear translocation leads to growth arrest during differentiation. We propose that CDKN1c activity is restricted to differentiating myoblasts by regulated cyto-nuclear relocalization, coordinating the balance between proliferation and growth arrest.

Developmentally linked human DNA hypermethylation is associated with down-modulation, repression, and upregulation of transcription

DNA methylation can affect tissue-specific gene transcription in ways that are difficult to discern from studies focused on genome-wide analyses of differentially methylated regions (DMRs). To elucidate the variety of associations between differentiation-related DNA hypermethylation and transcription, we used available epigenomic and transcriptomic profiles from 38 human cell/tissue types to focus on such relationships in 94 genes linked to hypermethylated DMRs in myoblasts (Mb). For 19 of the genes, promoter-region hypermethylation in Mb (and often a few heterologous cell types) was associated with gene repression but, importantly, DNA hypermethylation was absent in many other repressed samples. In another 24 genes, DNA hypermethylation overlapped cryptic enhancers or super-enhancers and correlated with down-modulated, but not silenced, gene expression. However, such methylation was absent, surprisingly, in both non-expressing samples and highly expressing samples. This suggests that some genes need DMR hypermethylation to help repress cryptic enhancer chromatin only when they are actively transcribed. For another 11 genes, we found an association between intergenic hypermethylated DMRs and positive expression of the gene in Mb. DNA hypermethylation/transcription correlations similar to those of Mb were evident sometimes in diverse tissues, such as aorta and brain. Our findings have implications for the possible involvement of methylated DNA in Duchenne's muscular dystrophy, congenital heart malformations, and cancer. This epigenomic analysis suggests that DNA methylation is not simply the inevitable consequence of changes in gene expression but, instead, is often an active agent for fine-tuning transcription in association with development.

Forkhead Box M1 Transcriptionally Regulates the Expression of Long Noncoding RNAs Snhg8 and Gm26917 to Promote Proliferation and Survival of Muscle Satellite Cells

Multiple functions have been proposed for transcription factor FoxM1, including the regulation of cell proliferation, differentiation, senescence, apoptosis, and tissue homeostasis. However, the role of FoxM1 in muscle satellite cells (SCs) remains unclear. In the present study, we demonstrated that FoxM1 was essential for the proliferation and survival of SCs. Crucially, we found that long noncoding RNAs (lncRNAs) Snhg8 and Gm26917 significantly regulated the proliferation and apoptosis of SCs, respectively, and these lncRNAs were directly regulated by FoxM1 in SCs. Mechanistically, Snhg8 sustained SCs proliferation by promoting the transcription of ribosomal proteins, while Gm26917 acted as a competing endogenous RNA for microRNA-29b, which accelerated apoptosis of SCs. In mice, conditional knockout of FoxM1 in skeletal muscle resulted in decreased proliferation and increased apoptosis of SCs. Thus, our studies revealed a previously unrecognized role of FoxM1 in SCs and uncovered two lncRNAs, Snhg8 and Gm26917, which function as novel targets of FoxM1 in the regulation of SCs proliferation and survival. Stem Cells 2018;36:1097-1108.

Genetic and Epigenetic Control of CDKN1C Expression: Importance in Cell Commitment and Differentiation, Tissue Homeostasis and Human Diseases

The CDKN1C gene encodes the p57^Kip2 protein which has been identified as the third member of the CIP/Kip family, also including p27^Kip1 and p21^Cip1. In analogy with these proteins, p57^Kip2 is able to bind tightly and inhibit cyclin/cyclin-dependent kinase complexes and, in turn, modulate cell division cycle progression. For a long time, the main function of p57^Kip2 has been associated only to correct embryogenesis, since CDKN1C-ablated mice are not vital. Accordingly, it has been demonstrated that CDKN1C alterations cause three human hereditary syndromes, characterized by altered growth rate. Subsequently, the p57^Kip2 role in several cell phenotypes has been clearly assessed as well as its down-regulation in human cancers. CDKN1C lies in a genetic locus, 11p15.5, characterized by a remarkable regional imprinting that results in the transcription of only the maternal allele. The control of CDKN1C transcription is also linked to additional mechanisms, including DNA methylation and specific histone methylation/acetylation. Finally, long non-coding RNAs and miRNAs appear to play important roles in controlling p57^Kip2 levels. This review mostly represents an appraisal of the available data regarding the control of CDKN1C gene expression. In addition, the structure and function of p57^Kip2 protein are briefly described and correlated to human physiology and diseases.

Epigenetic Regulation of Adult Myogenesis

Skeletal muscle regeneration is an efficient stem cell-based repair system that ensures healthy musculature. For this repair system to function continuously throughout life, muscle stem cells must contribute to the process of myofiber repair as well as repopulation of the stem cell niche. The decision made by the muscle stem cells to commit to the muscle repair or to remain a stem cell depends upon patterns of gene expression, a process regulated at the epigenetic level. Indeed, it is well accepted that dynamic changes in epigenetic landscapes to control DNA accessibility and expression is a critical component during myogenesis for the effective repair of damaged muscle. Changes in the epigenetic landscape are governed by various posttranslational histone tail modifications, nucleosome repositioning, and DNA methylation events which collectively allow the control of changes in transcription networks during transitions of satellite cells from a dormant quiescent state toward terminal differentiation. This chapter focuses upon the specific epigenetic changes that occur during muscle stem cell-mediated regeneration to ensure myofiber repair and continuity of the stem cell compartment. Furthermore, we explore open questions in the field that are expected to be important areas of exploration as we move toward a more thorough understanding of the epigenetic mechanism regulating muscle regeneration.

LincRNA FEZF1-AS1 contributes to the proliferation of LAD cells by silencing p57 expression

LincRNA FEZF1-AS1 has been identified to exert oncogenic functions in various biological processes of tumorigenesis. However, the function of FEZF1-AS1 in lung adenocarcinoma still remains unclear. Our findings revealed that FEZF1-AS1 was increased in lung adenocarcinoma tissues and cell lines and high level of FEZF1-AS1 was associated with poor prognosis of lung adenocarcinoma. Functional experiments and mechanistic investigations demonstrated that knockdown of FEZF1-AS1 significantly repressed proliferation through influencing the distribution of cell cycle. Besides, we also uncovered that FEZF1-AS1 could suppress p57 expression through recruiting EZH2 and LSD1 to the promoter of p57, thus influenced the cell cycle and proliferation. Collectively, our results suggested that FEZF1-AS1 was involved in the progression of lung adenocarcinoma and might be as a potential therapy target for human lung adenocarcinoma.

Tendons and Ligaments: Connecting Developmental Biology to Musculoskeletal Disease Pathogenesis

Tendons and ligaments provide connections between muscle and bone or bone and bone to enable locomotion. Damage to tendons and ligaments caused by acute or chronic injury or associated with aging and arthritis is a prevalent cause of disability. Improvements in approaches for the treatment of these conditions depend on a better understanding of tendon and ligament development, cell biology, and pathophysiology. This review focuses on recent advances in the discovery of transcription factors that control ligament and tendon cell differentiation, how cell and extracellular matrix homeostasis are altered in disease, and how this new insight can lead to novel therapeutic approaches. © 2017 American Society for Bone and Mineral Research.

Decreased mRNA expression levels of DNA methyltransferases type 1 and 3A in systemic lupus erythematosus

OBJECTIVES

Systemic lupus erythematosus (SLE) is a chronic relapsing autoimmune disease characterized by the presence of autoantibodies directed against nuclear antigens and by chronic inflammation. Although the etiology of SLE remains unclear, the influence of environment factors, which is largely reflected by the epigenetic mechanisms, with DNA methylation changes in particular, is generally considered as main players in the pathogenesis of SLE. We studied DNA methyltransferases' (DNMTs) type 1, 3A and 3B transcript levels in peripheral blood mononuclear cells from patients diagnosed with systemic lupus erythematosus and from the healthy control subjects. Furthermore, the association of DNMT1, DNMT3A, and DNMT3B mRNA levels with gender, age, and major clinical manifestations was analyzed.

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from 32 SLE patients and 40 healthy controls. Reverse transcription and real-time quantitative polymerase chain reaction (RT-qPCR) analyses were used to determine DNMT1, DNMT3A, and DNMT3B mRNA expression levels.

RESULTS

Significantly lower DNMT1 (p = 0.015543) and DNMT3A (p = 0.003652) transcript levels in SLE patients were observed compared with healthy controls. Nevertheless, the DNMT3B mRNA expression levels were markedly lower compared with DNMT1 and DNMT3A, both in PBMCs from affected patients and those from control subjects. Furthermore, the DNMT1 transcript levels were positively correlated with SLE disease activity index (SLEDAI) (r s = 0.4087, p = 0.020224), while the DNMT3A transcript levels were negatively correlated with patients age (r s = -0.3765, p = 0.03369).

CONCLUSIONS

Our analyses confirmed the importance of epigenetic alterations in SLE etiology. Moreover, our results suggest that the presence of some clinical manifestations, such as phototosensitivity and arthritis, might be associated with the dysregulation of DNA methyltransferases' mRNA expression levels.

Complementary Critical Functions of Zfy1 and Zfy2 in Mouse Spermatogenesis and Reproduction

The mammalian Y chromosome plays a critical role in spermatogenesis. However, the exact functions of each gene in the Y chromosome have not been completely elucidated, partly owing to difficulties in gene targeting analysis of the Y chromosome. Zfy was first proposed to be a sex determination factor, but its function in spermatogenesis has been recently elucidated. Nevertheless, Zfy gene targeting analysis has not been performed thus far. Here, we adopted the highly efficient CRISPR/Cas9 system to generate individual Zfy1 or Zfy2 knockout (KO) mice and Zfy1 and Zfy2 double knockout (Zfy1/2-DKO) mice. While individual Zfy1 or Zfy2-KO mice did not show any significant phenotypic alterations in fertility, Zfy1/2-DKO mice were infertile and displayed abnormal sperm morphology, fertilization failure, and early embryonic development failure. Mass spectrometric screening, followed by confirmation with western blot analysis, showed that PLCZ1, PLCD4, PRSS21, and HTT protein expression were significantly deceased in spermatozoa of Zfy1/2-DKO mice compared with those of wild-type mice. These results are consistent with the phenotypic changes seen in the double-mutant mice. Collectively, our strategy and findings revealed that Zfy1 and Zfy2 have redundant functions in spermatogenesis, facilitating a better understanding of fertilization failure and early embryonic development failure.

Long Intergenic Noncoding RNA 00511 Acts as an Oncogene in Non-small-cell Lung Cancer by Binding to EZH2 and Suppressing p57

Long noncoding RNAs (lncRNAs) play crucial roles in carcinogenesis. However, the function and mechanism of lncRNAs in human non–small-cell lung cancer (NSCLC) are still remaining largely unknown. Long intergenic noncoding RNA 00511 (LINC00511) has been found to be upregulated and acts as an oncogene in breast cancer, but little is known about its expression pattern, biological function and underlying mechanism in NSCLC. Herein, we identified LINC00511 as an oncogenic lncRNA by driving tumorigenesis in NSCLC. We found LINC00511 was upregulated and associated with oncogenesis, tumor size, metastasis, and poor prognosis in NSCLC. Moreover, LINC00511 affected cell proliferation, invasiveness, metastasis, and apoptosis in multiple NSCLC cell lines. Mechanistically, LINC00511 bound histone methyltransferase enhancer of zeste homolog 2 ((EZH2, the catalytic subunit of the polycomb repressive complex 2 (PRC2), a highly conserved protein complex that regulates gene expression by methylating lysine 27 on histone H3), and acted as a modular scaffold of EZH2/PRC2 complexes, coordinated their localization, and specified the histone modification pattern on the target genes, including p57, and consequently altered NSCLC cell biology. Thus, LINC00511 is mechanistically, functionally, and clinically oncogenic in NSCLC. Targeting LINC00511 and its pathway may be meaningful for treating patients with NSCLC.