MEF2D Functions as a Tumor Suppressor in Breast Cancer

The myocyte enhancer factor 2 (MEF2) gene family play fundamental roles in the genetic programs that control cell differentiation, morphogenesis, proliferation, and survival in a wide range of cell types. More recently, these genes have also been implicated as drivers of carcinogenesis, by acting as oncogenes or tumor suppressors depending on the biological context. Nonetheless, the molecular programs they regulate and their roles in tumor development and progression remain incompletely understood. The present study evaluated whether the MEF2D transcription factor functions as a tumor suppressor in breast cancer. The knockout of the MEF2D gene in mouse mammary epithelial cells resulted in phenotypic changes characteristic of neoplastic transformation. These changes included enhanced cell proliferation, a loss of contact inhibition, and anchorage-independent growth in soft agar, as well as the capacity for tumor development in mice. Mechanistically, the knockout of MEF2D induced the epithelial-to-mesenchymal transition (EMT) and activated several oncogenic signaling pathways, including AKT, ERK, and Hippo-YAP. Correspondingly, a reduced expression of MEF2D was observed in human triple-negative breast cancer cell lines, and a low MEF2D expression in tissue samples was found to be correlated with a worse overall survival and relapse-free survival in breast cancer patients. MEF2D may, thus, be a putative tumor suppressor, acting through selective gene regulatory programs that have clinical and therapeutic significance.

MEF2D facilitates liver metastasis of gastric cancer cells through directly inducing H1X under IL-13 stimulation

Liver metastasis is the most common metastatic occurrence in gastric cancer patients, although the precise mechanism behind it remains unclear. Through a combination of proteomics and quantitative RT-PCR, our study has revealed a significant correlation between the upregulation of myocyte enhancer factor-2D (MEF2D) and both distant metastasis and poor prognosis in gastric cancer patients. In mouse models, we observed that overexpressing or knocking down MEF2D in gastric cancer cells respectively promoted or inhibited liver metastasis. Furthermore, our research has demonstrated that MEF2D regulates the transcriptional activation of H1X by binding to the H1X promoter. This regulation leads to the upregulation of H1X, which, in turn, promotes the in vivo metastasis of gastric cancer cells along with the upregulation of the downstream gene β-CATENIN. Additionally, we found that the expression of MEF2D and H1X at both mRNA and protein levels can be induced by the inflammatory factor IL-13, and this induction exhibits a time gradient dependence. In human gastric cancer tissues, the expression of IL13RA1, the receptor for IL-13, positively correlates with the expression of MEF2D and H1X. IL13RA1 has been identified as an intermediate receptor through which IL-13 regulates MEF2D. In conclusion, our findings suggest that MEF2D plays a crucial role in promoting liver metastasis of gastric cancer by upregulating H1X and downstream target β-CATENIN in response to IL-13 stimulation. Targeting MEF2D could therefore be a promising therapeutic strategy for the clinical management of gastric cancer. STATEMENT OF SIGNIFICANCE: MEF2D promotes its transcriptional activation in gastric cancer cells by binding to the H1X promoter and is upregulated by IL-13-IL13RA1, thereby promoting distant metastasis of gastric cancer.

Association between MEF2 family gene polymorphisms and susceptibility to multiple sclerosis in Chinese population

PURPOSE

Multiple sclerosis (MS) is an autoimmune disease characterized by inflammatory demyelinating lesions in the white matter of the central nervous system. Myocyte enhancer factor 2 (MEF2) family genes play important roles in the immune response. This study focuses on the relationship between MEF2 family gene polymorphisms and MS.

METHODS

A total of 174 MS patients and 120 healthy controls were recruited. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to analyze the gene polymorphisms of MEF2D and MEF2C. In addition, peripheral blood was collected and leukocytes were isolated. The transcription level of MEF2D in the two groups of samples was detected with quantitative real time polymerase chain reaction (qRT-PCR).

RESULTS

We found that the C allele frequency and CC genotype frequency of rs2274316 in MEF2D were significantly higher in MS patients. The C allele and CT genotype distribution for rs3790455 were significantly more frequent in MS patients. Female patients showed higher CC genotype frequency of rs2274316. The genotype frequency distribution of rs2274316 and rs3790455 were not related to onset age and phenotype of MS patients. In addition, this study also proved that MEF2D was significantly overexpressed in the peripheral blood leukocytes of MS patients. The transcription level of MEF2D was significantly higher in patients with CC genotype of rs2274316.

CONCLUSION

These findings suggest rs2274316 and rs3790455 of MEF2D gene are potential genetic risk factors for MS in Chinese population. The transcription level of MEF2D is also associated with susceptibility to MS and MEF2D gene polymorphisms.

Myxoid epithelioid smooth muscle tumor of the vulva: A distinct entity with MEF2D::NCOA2 gene fusion

Smooth muscle tumors are the most common mesenchymal tumors of the female genital tract, including the vulva. Since vulvar smooth muscle tumors are rare, our understanding of them compared to their uterine counterparts continues to evolve. Herein, we present two cases of morphologically distinct myxoid epithelioid smooth muscle tumors of the vulva with novel MEF2D::NCOA2 gene fusion. The tumors involved 24 and 37-year-old women. Both tumors presented as palpable vulvar masses that were circumscribed, measuring 2.8 and 5.1 cm in greatest dimension. Histologically, they were composed of epithelioid to spindle-shaped cells with minimal cytologic atypia and prominent myxoid matrix. Rare mitotic figures were present (1-3 mitotic figures per 10 high-power field (HPF)), and no areas of tumor necrosis were identified. By immunohistochemistry, the neoplastic cells strongly expressed smooth muscle actin, calponin, and desmin, confirming smooth muscle origin. Next-generation sequencing identified identical MEF2D::NCOA2 gene fusions. These two cases demonstrate that at least a subset of myxoid epithelioid smooth muscle tumors of the vulva represent a distinct entity characterized by a novel MEF2D::NCOA2 gene fusion. Importantly, recognition of the distinct morphologic and genetic features of these tumors is key to understanding the biological potential of these rare tumors.

A Ubiquitin-Dependent Switch on MEF2D Senses Pro-Metastatic Niche Signals to Facilitate Intrahepatic Metastasis of Liver Cancer

Effective treatment for metastasis, a leading cause of cancer-associated death, is still lacking. To seed on a distal organ, disseminated cancer cells (DCCs) must adapt to the local tissue microenvironment. However, it remains elusive how DCCs respond the pro-metastatic niche signals. Here, systemic motif-enrichment identified myocyte enhancer factor 2D (MEF2D) as a critical sensor of niche signals to regulate DCCs adhesion and colonization, leading to intrahepatic metastasis and recurrence of liver cancer. In this context, MEF2D transactivates Itgb1 (coding β1-integrin) and Itgb4 (coding β4-integrin) to execute temporally unique functions, where ITGB1 recognizes extracellular matrix for early seeding, and ITGB4 acts as a novel sensor of neutrophil extracellular traps-DNA (NETs-DNA) for subsequent chemotaxis and colonization. In turn, an integrin-FAK circuit promotes a phosphorylation-dependent USP14-orchastrated deubiquitination switch to stabilize MEF2D via circumventing degradation by the E3-ubiquitin-ligase MDM2. Clinically, the USP14(pS432)-MEF2D-ITGB1/4 feedback loop is often hyper-active and indicative of inferior outcomes in human malignancies, while its blockade abrogated intrahepatic metastasis of DCCs. Together, DCCs exploit a deubiquitination-dependent switch on MEF2D to integrate niche signals in the liver mesenchyme, thereby amplifying the pro-metastatic integrin-FAK signaling. Disruption of this feedback loop is clinically applicable with fast-track potential to block microenvironmental cues driving metastasis.

The Dual Functions of Andrographolide in the Epstein-Barr Virus-Positive Head-and-Neck Cancer Cells: The Inhibition of Lytic Reactivation of the Epstein-Barr Virus and the Induction of Cell Death

Andrographolide, a medicinal compound, exhibits several pharmacological activities, including antiviral and anticancer properties. Previously, we reported that andrographolide inhibits Epstein-Barr virus (EBV) lytic reactivation, which is associated with viral transmission and oncogenesis in epithelial cancers, including head-and-neck cancer (HNC) cells. However, the underlying mechanism through which andrographolide inhibits EBV lytic reactivation and affects HNC cells is poorly understood. Therefore, we investigated these mechanisms using EBV-positive HNC cells and the molecular modeling and docking simulation of protein. Based on the results, the expression of EBV lytic genes and viral production were significantly inhibited in andrographolide-treated EBV-positive HNC cells. Concurrently, there was a reduction in transcription factors (TFs), myocyte enhancer factor-2D (MEF2D), specificity protein (SP) 1, and SP3, which was significantly associated with a combination of andrographolide and sodium butyrate (NaB) treatment. Surprisingly, andrographolide treatment also significantly induced the expression of DNA Methyltransferase (DNMT) 1, DNMT3B, and histone deacetylase (HDAC) 5 in EBV-positive cells. Molecular modeling and docking simulation suggested that HDAC5 could directly interact with MEF2D, SP1, and SP3. In our in vitro study, andrographolide exhibited a stronger cytotoxic effect on EBV-positive cells than EBV-negative cells by inducing cell death. Interestingly, the proteome analysis revealed that the expression of RIPK1, RIPK3, and MLKL, the key molecules for necroptosis, was significantly greater in andrographolide-treated cells. Taken together, it seems that andrographolide exhibits concurrent activities in HNC cells; it inhibits EBV lytic reactivation by interrupting the expression of TFs and induces cell death, probably via necroptosis.

Dexmedetomidine abates myocardial ischemia reperfusion injury through inhibition of pyroptosis via regulation of miR-665/MEF2D/Nrf2 axis

The current study intended to delve into the mechanisms of dexmedetomidine (Dex) in regulating myocardial pyroptosis against myocardial ischemia/reperfusion injury (MIRI). The rat MIRI models were induced by ligation/release of the coronary artery in vivo and Langendorff perfusion ex vivo. Hemodynamic parameters, infarction sizes, and histopathological changes were assessed to understand the effects of Dex on MIRI. We explored the mechanisms through functional experiments on an H9c2 cell hypoxia/reoxygenation (H/R) model. Cell viability and apoptosis were evaluated using cell counting kit 8 (CCK-8) and AV/PI dual staining respectively. The expressions of miR-665 and MEF2D mRNA were detected by qRT-PCR. Western blot was employed to determine the expression levels of pyroptosis- and signaling pathway- related proteins. The interplays between miR-665 and MEF2D were validated by Dual-luciferase reporter assays. Our findings indicated that Dex preconditioning dramatically attenuated hemodynamic derangements, infarct size, and histopathological damage in rats undergoing MIRI. Dex markedly augmented cell viability, while suppressing cell apoptosis and expressions of NLRP3, cleaved-caspase-1, ASC, GSDMD, IL-1β, and IL-18 in H9c2 cells subjected to H/R injury. MiR-665 was significantly upregulated, MEF2D and Nrf2 downregulated following H/R, whereas Dex preconditioning reversed these changes. MEF2D was validated to be a target gene of miR-665. Overexpression of miR-665 decreased the expression of MEF2D and blunted the protective effects of Dex in H9c2 cells. Moreover, the functional rescue experiment further verified that Dex regulated MEF2D/Nrf2 pathway via miR-665. In conclusion, Dex mitigates MIRI through inhibiting pyroptosis via regulating miR-665/MEF2D/Nrf2 axis.

[Expression of MEF2D in Lung Adenocarcinoma and Its Correlation with Prognosis]

BACKGROUND

Myocyte enhancer factor 2D (MEF2D) can participate in the process of tumor lesions by regulating the transcription of oncogenes. In a previous study, MEF2D was demonstrated to enhance the proliferation and metastasis of lung adenocarcinoma cells A549 and H1299 by promoting the transcription of NUSAP1. The research aimed to explore the expression level and clinical significance of MEF2D in lung adenocarcinoma.

METHODS

A total of 199 patients with lung adenocarcinoma were collected. Immunohistochemical staining was used to detect MEF2D expression levels in cancer and adjacent tissues. After the clinical and follow-up data were collated, the correlation between MEF2D expression level and clinical characteristics and prognosis of the patients was analyzed.

RESULTS

In the lung adenocarcinoma, the high expression rate of MEF2D in cancer tissues was significantly higher than that in adjacent tissues (P<0.05). According to immunohistochemical score, MEF2D expression level in lung adenocarcinoma tissues was correlated with tumor differentiation, N stage, M stage and intrapulmonary metastasis (P<0.05). Kaplan-Meier analysis showed that patients with low MEF2D expression had significantly better prognosis than patients with high MEF2D expression (P<0.05). Cox multivariate analysis showed that MEF2D expression level, M stage, N stage and bone metastasis of lung cancer were independent risk factors for prognosis of lung adenocarcinoma patients.

CONCLUSIONS

MEF2D expression level is closely related to the metastasis of lung adenocarcinoma and other clinical characteristics, and can be used as an independent risk factor for the prognosis of patients with lung adenocarcinoma, which has the potential to be developed as a clinical diagnosis and treatment target of lung adenocarcinoma.

p38γ and p38δ modulate innate immune response by regulating MEF2D activation

Evidence implicating p38γ and p38δ (p38γ/p38δ) in inflammation are mainly based on experiments using Mapk12/Mapk13-deficient (p38γ/δKO) mice, which show low levels of TPL2, the kinase upstream of MKK1-ERK1/2 in myeloid cells. This could obscure p38γ/p38δ roles, since TPL2 is essential for regulating inflammation. Here, we generated a Mapk12D171A/D171A/Mapk13-/- (p38γ/δKIKO) mouse, expressing kinase-inactive p38γ and lacking p38δ. This mouse exhibited normal TPL2 levels, making it an excellent tool to elucidate specific p38γ/p38δ functions. p38γ/δKIKO mice showed a reduced inflammatory response and less susceptibility to lipopolysaccharide (LPS)-induced septic shock and Candida albicans infection than wild-type (WT) mice. Gene expression analyses in LPS-activated wild-type and p38γ/δKIKO macrophages revealed that p38γ/p38δ-regulated numerous genes implicated in innate immune response. Additionally, phospho-proteomic analyses and in vitro kinase assays showed that the transcription factor myocyte enhancer factor-2D (MEF2D) was phosphorylated at Ser444 via p38γ/p38δ. Mutation of MEF2D Ser444 to the non-phosphorylatable residue Ala increased its transcriptional activity and the expression of Nos2 and Il1b mRNA. These results suggest that p38γ/p38δ govern innate immune responses by regulating MEF2D phosphorylation and transcriptional activity.

[Clinical characteristics and outcomes of childhood B-ALL with ZNF384 and MEF2D rearrangements]

B-cell precursor acute lymphoblastic leukemia (BCP-ALL) has many subtypes with diverse clinical and biological features and outcomes. Next generation sequencing has revealed several novel subtypes, including the ZNF384 and MEF2D rearrangements. The clinical characteristics and outcomes of the largest series of BCP-ALL cases with ZNF384 and MEF2D rearrangements in an international collaborative study are described here. Patients with ZNF384 rearrangements appear to express various leukemic phenotypes, including BCP-ALL (with or without abnormal expression of myeloid markers) and B/myeloid mixed phenotype acute leukemia. We provide strong evidence that among BCP-ALL patients with a ZNF384 fusion, the partner gene is associated with demographic features and influences the outcome; particularly the EP300-ZNF384 fusion is associated with a low risk of relapse. MEF2D rearrangements have been primarily described in children and young adults with BCP-ALL. Previous research has suggested that patients with MEF2D-BCL9 fusion have a high risk of relapse. Despite having the MEF2D-HNRNPUL1 fusion gene, the prognosis was favorable. Improved diagnostic genomic testing will enable future prospective studies to clarify the clinical significance of the ZNF384 and MEF2D rearrangements in childhood and young adult BCP-ALL.

Sevoflurane activates MEF2D-mediated Wnt/β-catenin signaling pathway via microRNA-374b-5p to affect renal ischemia/reperfusion injury

BACKGROUND

The inhaled sevoflurane (Sev) has been demonstrated to protect multiple organs against ischemia/reperfusion injury (IRI). However, the mechanisms of Sev in renal IRI remain largely unknown. This study intends to explore the effect of Sev on renal IRI and the molecular mechanism behind.

METHODS

Following Sev preconditioning, a mouse model with renal IRI was established. The effects of Sev on IRI in mice were assessed by BUN, Scr, MDA and SOD kits, Western blot, HE staining, and TUNEL. Subsequently, we performed microarray analysis on renal tissues from mice with Sev to identify differentially expressed microRNAs (miRNAs). Then, the mice were treated with agomiR-374b-5p combined with Sev to observe the renal histopathology after IRI. The targeting mRNA of miR-374b-5p was verified using bioinformatics analysis and dual-luciferase assay, followed by KEGG enrichment analysis. Rescue experiments were implemented with simultaneous miR-374b-5p and MEF2D overexpression to detect renal histopathology and Wnt/β-catenin pathway activity in the mice.

RESULTS

Sev significantly reduced the levels of BUN and Scr in mouse serum, prevented cell apoptosis, decreased MDA content and increased SOD levels in renal tissues. Moreover, Sev downregulated the miR-374b-5p expression in the renal tissues. Overexpression of miR-374b-5p attenuated the protective effects of Sev on mouse renal tissues. miR-374b-5p targeted MEF2D and blocked the Wnt/β-catenin pathway. Overexpression of MEF2D activated the Wnt/β-catenin pathway and attenuated the supporting effects of miR-374b-5p on renal IRI.

CONCLUSION

Sev promotes MEF2D and activates the Wnt/β-catenin pathway through inhibition of miR-374b-5p expression to affect renal IRI.

LncRNA CASC15 regulates breast cancer cell stemness via the miR-654-5p/MEF2D axis

Emerging evidence has demonstrated the prognostic and diagnostic potential of long noncoding RNA (lncRNA) cancer susceptibility candidate 15 (lncRNA CASC15) for the progression and tumorigenesis of human cancer. However, how CASC15 modulates the stemness of breast cancer stem cells (BCSCs) is not well understood. In this study, high expression of CASC15 in MCF-7 CSCs was reported, relative to MCF-7 cells, and this phenomenon was associated with metastatic lymph nodes, higher TNM stage, and shorter breast cancer survival rates. Further experiments revealed that CASC15 promoted the acquisition of stemness properties of breast cancer cells (BSCCs) by competing with endogenous RNA for miR-654-5p, resulting in overexpression of MEF2D in BCSCs. Overall, breast cancer stemness and tumor development are regulated via the CASC15/miR-654-5p/MEF2D axis. Accordingly, this pathway can be explored for breast cancer therapy.

A distinct core regulatory module enforces oncogene expression in KMT2A-rearranged leukemia

In this study, Harada et al. identified the transcription factors MEF2D and IRF8 as selective transcriptional dependencies of KMT2A-rearranged AML, where MEF2D displays partially redundant functions with its paralog, MEF2C. This study illustrates a mechanism of context-specific transcriptional addiction whereby a specific AML subclass depends on a highly specialized core regulatory module to directly enforce expression of common leukemia oncogenes.

Acute myeloid leukemia with KMT2A (MLL) rearrangements is characterized by specific patterns of gene expression and enhancer architecture, implying unique core transcriptional regulatory circuitry. Here, we identified the transcription factors MEF2D and IRF8 as selective transcriptional dependencies of KMT2A-rearranged AML, where MEF2D displays partially redundant functions with its paralog, MEF2C. Rapid transcription factor degradation followed by measurements of genome-wide transcription rates and superresolution microscopy revealed that MEF2D and IRF8 form a distinct core regulatory module with a narrow direct transcriptional program that includes activation of the key oncogenes MYC, HOXA9, and BCL2. Our study illustrates a mechanism of context-specific transcriptional addiction whereby a specific AML subclass depends on a highly specialized core regulatory module to directly enforce expression of common leukemia oncogenes.

Andrographolide Inhibits Lytic Reactivation of Epstein-Barr Virus by Modulating Transcription Factors in Gastric Cancer

Andrographolide is the principal bioactive chemical constituent of Andrographis paniculata and exhibits activity against several viruses, including Epstein–Barr virus (EBV). However, the particular mechanism by which andrographolide exerts an anti-EBV effect in EBV-associated gastric cancer (EBVaGC) cells remains unclear. We investigated the molecular mechanism by which andrographolide inhibits lytic reactivation of EBV in EBVaGC cells (AGS-EBV cell line) using proteomics and bioinformatics approaches. An andrographolide treatment altered EBV protein-expression patterns in AGS-EBV cells by suppressing the expression of EBV lytic protein. Interestingly cellular transcription factors (TFs), activators for EBV lytic reactivation, such as MEF2D and SP1, were significantly abolished in AGS-EBV cells treated with andrographolide and sodium butyrate (NaB) compared with NaB-treated cells. In contrast, the suppressors of EBV lytic reactivation, such as EZH2 and HDAC6, were significantly up-regulated in cells treated with both andrographolide and NaB compared with NaB treatment alone. In addition, bioinformatics predicted that HDAC6 could interact directly with MEF2D and SP1. Furthermore, andrographolide significantly induced cell cytotoxicity and apoptosis of AGS-EBV cells by induction of apoptosis-related protein expression. Our results suggest that andrographolide inhibits EBV lytic reactivation by inhibition of host TFs, partially through the interaction of HDAC6 with TFs, and induces apoptosis of EBVaGC cells.

FAM83H-AS1/miR-485-5p/MEF2D axis facilitates proliferation, migration and invasion of hepatocellular carcinoma cells

Background

Abundant evidence has manifested that long noncoding RNAs (lncRNAs) are closely implicated in human cancers, including hepatocellular carcinoma (HCC). Remarkably, lncRNA FAM83H antisense RNA 1 (FAM83H-AS1) has been reported to be a tumor-propeller in multiple cancers. However, its effect on HCC progression remains unknown.

Methods

FAM83H-AS1 expression was analyzed by RT-qPCR. Colony formation, EdU, and flow cytometry as well as transwell assays were implemented to analyze the biological functions of FAM83H-AS1 on HCC progression. Luciferase reporter, RIP and RNA pull-down assays were implemented to detect the interaction among FAM83H-AS1, microRNA-485-5p (miR-485-5p), and myocyte enhancer factor 2D (MEF2D) in HCC cells.

Results

FAM83H-AS1 expression in HCC cells was markedly elevated. FAM83H-AS1 accelerated cell proliferation, migration and invasion whereas inhibiting cell apoptosis in HCC. Besides, we confirmed that FAM83H-AS1 acts as a miR-485-5p sponge in HCC cells. Additionally, MEF2D was verified to be a direct target of miR-485-5p. FAM83H-AS1 could upregulate MEF2D expression via sponging miR-485-5p. Further, rescue experiments testified that MEF2D upregulation or miR-485-5p downregulation offset the repressive effect of FAM83H-AS1 depletion on HCC cell progression.

Conclusions

FAM83H-AS1 facilitates HCC malignant progression via targeting miR-485-5p/MEF2D axis, suggesting that FAM83H-AS1 may be a promising biomarker for HCC treatment in the future.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08923-0.

MEF2D-NR4A1-FAM134B2-mediated reticulophagy contributes to amino acid homeostasis

We recently identified FAM134B2, which is an N-terminal truncated reticulophagy receptor highly induced by starvation such as fasting of mice and treatment of mammalian cells with a starvation medium that does not contain amino acids, glucose and growth factors. However, which starvation signal mediates the induction of FAM134B2 is still obscure. In this study, we found that amino acid deficiency (AAD) could mimic the starvation condition to induce FAM134B2 expression. Unexpectedly, EIF2AK4/GCN2-mediated integrated signal response (ISR) and MTOR (mechanistic target of rapamycin kinase) signals, which constitute two major signaling pathways that respond to AAD, did not contribute to AAD-induced FAM134B2 induction. mRNA-seq and siRNA screenings identified two ISR-independent transcription factors, MEF2D (myocyte enhancer factor 2D) and NR4A1 (nuclear receptor subfamily 4 group A member 1), involved in AAD-induced FAM134B2 expression. AAD induces MEF2D, resulting in the induction of NR4A1, which in turn induces FAM134B2-mediated reticulophagy to maintain intracellular amino acid levels. In conclusion, the MEF2D-NR4A1-FAM134B2 cascade is a critical signal in amino acid homeostasis.

Promising tacrine/huperzine A-based dimeric acetylcholinesterase inhibitors for neurodegenerative disorders: From relieving symptoms to modifying diseases through multitarget

Neurodegenerative disorders, such as Alzheimer's disease and Parkinson's disease, are devastating diseases in the elderly world, which are closely associated with progressive neuronal loss induced by a variety of genetic and/or environmental factors. Unfortunately, currently available treatments for neurodegenerative disorders can only relieve the symptoms but not modify the pathological processes. Over the past decades, our group by collaborating with Profs. Yuan-Ping Pang and Paul R. Carlier has developed three series of homo/hetero dimeric acetylcholinesterase inhibitors derived from tacrine and/or huperzine A. The representative dimers bis(3)-Cognitin (B3C), bis(12)-hupyridone, and tacrine(10)-hupyridone might possess disease-modifying effects through the modulation of N-methyl-d-aspartic acid receptors, the activation of myocyte enhancer factor 2D gene transcription, and the promotion of neurotrophic factor secretion. In this review, we summarize that the representative dimers, such as B3C, provide neuroprotection against a variety of neurotoxins via multiple targets, including the inhibitions of N-methyl-d-aspartic acid receptor with pathological-activated potential, neuronal nitric oxide synthase, and β-amyloid cascades synergistically. More importantly, B3C might offer disease-modifying potentials by activating myocyte enhancer factor 2D transcription, inducing neuritogenesis, and promoting the expressions of neurotrophic factors in vitro and in vivo. Taken together, the novel dimers might offer synergistic disease-modifying effects, proving that dimerization might serve as one of the strategies to develop new generation of therapeutics for neurodegenerative disorders.

LGI1 governs neuritin-mediated resilience to chronic stress

Depression is accompanied by neuronal atrophy and decreased neuroplasticity. Leucine-rich glioma-inactivated protein 1 (LGI1), a metastasis suppressor, plays an important role in the development of CNS synapses. We found that LGI1 expression was reduced in the hippocampi of mice that underwent chronic unpredictable stress (CUS), and could be rescued by the antidepressant, fluoxetine. Recombinant soluble neuritin, an endogenous protein previously implicated in antidepressant-like behaviors, elevated hippocampal LGI1 expression in a manner dependent on histone deacetylase 5 (HDAC5) phosphorylation. Accordingly, Nrn1 ^flox/flox ;Pomc-cre (Nrn1 cOE) mice, which conditionally overexpress neuritin, displayed increases in hippocampal LGI1 level under CUS and exhibited resilience to CUS that were blocked by hippocampal depletion of LGI1. Interestingly, neuritin-mediated LGI1 expression was inhibited by HNMPA-(AM)₃, an insulin receptor inhibitor, as was neuritin-mediated HDAC5 phosphorylation. We thus establish hippocampal LGI1 as an effector of neurite outgrowth and stress resilience, and suggest that HDAC5-LGI1 plays a critical role in ameliorating pathological depression.

Coupling HDAC4 with transcriptional factor MEF2D abrogates SPRY4-mediated suppression of ERK activation and elicits hepatocellular carcinoma drug resistance

Hepatocellular carcinoma (HCC) lacks effective treatment, and the patients rapidly develop the acquired resistance to sorafenib with less defined mechanisms. Here, we demonstrate that transcriptional factor myocyte enhancer factor 2D (MEF2D) overexpression is detected in sorafenib-resistant HCC specimens and HCC cell lines and predicts poor prognosis of sorafenib-treated HCC patients. Mechanistically, MEF2D in complex with histone deacetylase HDAC4 directly binds to the SPRY4 promoter regions and suppresses the transcriptional expression of SPRY4, which is a negative regulator of MAPK/ERK signaling pathway. Inhibition of HDAC4 with its clinically used inhibitor induces SPRY4 expression and inhibition of ERK activity, resulting in sensitization of HCC cells to sorafenib-induced apoptosis and greatly improved inhibition of liver tumor growth in mice with sorafenib treatment. These findings highlight the critical role of coupling HDAC4 with MEF2D in activation of ERK by suppressing SPRY4 and underscore the great potential to improve HCC treatment by combined administration of sorafenib with HDAC4 inhibitors.

ZMYND8-regulated IRF8 transcription axis is an acute myeloid leukemia dependency

The transformed state in acute leukemia requires gene regulatory programs involving transcription factors and chromatin modulators. Here, we uncover an IRF8-MEF2D transcriptional circuit as an acute myeloid leukemia (AML)-biased dependency. We discover and characterize the mechanism by which the chromatin "reader" ZMYND8 directly activates IRF8 in parallel with the MYC proto-oncogene through their lineage-specific enhancers. ZMYND8 is essential for AML proliferation in vitro and in vivo and associates with MYC and IRF8 enhancer elements that we define in cell lines and in patient samples. ZMYND8 occupancy at IRF8 and MYC enhancers requires BRD4, a transcription coactivator also necessary for AML proliferation. We show that ZMYND8 binds to the ET domain of BRD4 via its chromatin reader cassette, which in turn is required for proper chromatin occupancy and maintenance of leukemic growth in vivo. Our results rationalize ZMYND8 as a potential therapeutic target for modulating essential transcriptional programs in AML.

DYRK1A phosphorylates MEF2D and decreases its transcriptional activity

Myocyte enhancer factor 2D (MEF2D) is predominantly expressed in the nucleus and associated with cell growth, differentiation, survival and apoptosis. Previous studies verified that phosphorylation at different amino acids determined MEF2's transcriptional activity which was essential in regulating downstream target genes expression. What regulates phosphorylation of MEF2D and affects its function has not been fully elucidated. Here, we uncovered that dual-specificity tyrosine phosphorylation regulated kinase 1A (DYRK1A), a kinase critical in Down's syndrome pathogenesis, directly bound to and phosphorylated MEF2D at Ser251 in vitro. Phosphorylation of MEF2D by DYRK1A significantly increased MEF2D protein level but attenuated its transcriptional activity, which resulted in decreased transcriptions of MEF2D target genes. Phosphorylation mutated Ser251A MEF2D exhibited enhanced transcriptional activity compared with wild type MEF2D. MEF2D and DYRK1A were observed co-localized in HEK293 and U87MG cells. Moreover, DYRK1A-mediated MEF2D phosphorylation in vitro might influence its nuclear export upon subcellular fractionation, which partially explained the reduction of MEF2D transcriptional activity by DYRK1A. Our results indicated that DYRK1A might be a regulator of MEF2D transcriptional activity and indirectly get involved in regulation of MEF2D target genes.

Regulation of IFN-Is by MEF2D Promotes Inflammatory Homeostasis in Microglia

Background

Microglia play an essential role in the central nervous system immune response. The transcription factor myocyte enhancer factor-2 D (MEF2D) is known to participate in stress regulation in various cell types and is easily activated in microglia. MEF2D has been shown to transcriptionally regulate several cytokine genes in immune cells and directly regulates the inflammatory response, suggesting that MEF2D may act as a key stimulus response regulator of microglia and is involved in the regulation of brain microhomeostasis. To uncover the molecular mechanism of MEF2D in the inflammatory system, in the present study, we investigated the global effect of MEF2D in activated microglia and explored its potential regulatory network.

Methods

Experiments with a recombinant lentiviral vector containing either shRNA or overexpressing MEF2D were performed in the murine microglial BV2 cell line. Transcriptome sequencing and global gene expression patterns were analysed in lipopolysaccharide-stimulated shMEF2D BV2 cells. Pro- and anti-inflammatory factors were assessed by Western blot, qPCR or ELISA, and microglial activity was assessed by phagocytosis and morphologic analysis. The direct binding of MEF2D to the promoter region of interferon regulatory factor 7 (IRF7) was tested by ChIP-qPCR. The interferon-stimulated genes (ISGs) were tested by qPCR.

Results

MEF2D actively participated in the inflammatory response of BV2 microglial cells. Stably expressed RNAi-induced silencing of MEF2D disrupted the microglial immune balance in two ways: (1) the expression of proinflammatory factors, such as NLRP3, IL-1β, and iNOS was promoted; and (2) the type-I interferon signalling pathway was markedly inhibited by directly modulating IRF7 transcription. In contrast, overexpression of MEF2D significantly reduced the expression of NLRP3 and iNOS under LPS stimulation and alleviated the level of immune stress in microglia.

Conclusion

These findings demonstrate that MEF2D plays an important role in regulating inflammatory homeostasis partly through transcriptional regulation of the type-I interferon signalling pathway.

Isoflurane post-conditioning contributes to anti-apoptotic effect after cerebral ischaemia in rats through the ERK5/MEF2D signaling pathway

The mechanisms of brain protection during ischaemic reperfusion injury induced by isoflurane (ISO) post‐conditioning are unclear. Myocyte enhancement factor 2 (MEF2D) has been shown to promote neural survival in a variety of models, in which multiple survival and death signals converge on MEF2D and modulate its activity. Here, we investigated the effect of MEF2D on the neuroprotective effects of ISO post‐conditioning on rats after cerebral ischaemia/reperfusion (I/R) injury. Rats underwent middle cerebral artery occlusion (MCAO) surgery with ischaemia for 90 minutes and reperfusion for 24‐48 hours. After MCAO, neurological status was assessed at 12, 24 and 48 hours by the Modified Neurological Severity Score (mNSS) test. The passive avoidance test (PAT) was used to assess cognition function. Histological and neuropathological evaluations were performed with HE staining and Nissl's staining, respectively. We measured the expression of MEF2D, ERK5, GFAP and caspase‐3 by immunofluorescent staining and Western blotting, and TUNEL staining to assess the severity of apoptosis in hippocampal CA1 area. We found that MEF2D was involved in nerve protection after I/R injury, and post‐treatment of ISO significantly promoted the phosphorylation of ERK5, increased MEF2D transcriptional activity, inhibited the expression of caspase‐3 and played a role of brain protection.

MiR-421 Aggravates Neurotoxicity and Promotes Cell Death in Parkinson's Disease Models by Directly Targeting MEF2D

Parkinson's disease (PD) is a severe neurodegenerative disease characterized by selective loss of dopaminergic neurons, which reduces quality of life of patients and poses a heavy burden to the society. The pathological mechanism of PD remains unclear, and increasing efforts are aimed to solve this problem. MiRNAs are a kind of small noncoding RNA regulating target gene expression. Previous studies have shown that dysregulation of miRNAs is involved in the development of PD. In the present study, we determined that miR-421 and MEF2D are increased and decreased, respectively, in a cellular model of PD. The data on the mechanism of action indicate that miR-421 directly binds to MEF2D mRNA and negatively regulates MEF2D expression. An increase in miR-421 disrupted the Bcl2/Bax system. Functional assays indicated that enhanced miR-421 promotes cell death by negative modulation of MEF2D expression. Inhibition of miR-421 or restoration of MEF2D protected neurons from neurotoxicity in cellular and animal models of PD. Our study is the first to demonstrate that miR-421 is decreased in PD models and to determine a novel putative mechanism of PD pathogenesis.

Quis Custodiet Ipsos Custodes (Who Controls the Controllers)? Two Decades of Studies on HDAC9

Understanding how an epigenetic regulator drives different cellular responses can be a tricky task. Very often, their activities are modulated by large multiprotein complexes, the composition of which is context- and time-dependent. As a consequence, experiments aimed to unveil the functions of an epigenetic regulator can provide different outcomes and conclusions, depending on the circumstances. HDAC9 (histone deacetylase), an epigenetic regulator that influences different differentiating and adaptive responses, makes no exception. Since its discovery, different phenotypes and/or dysfunctions have been observed after the artificial manipulation of its expression. The cells and the microenvironment use multiple strategies to control and monitor HDAC9 activities. To date, some of the genes under HDAC9 control have been identified. However, the exact mechanisms through which HDAC9 can achieve all the different tasks so far described, remain mysterious. Whether it can assemble into different multiprotein complexes and how the cells modulate these complexes is not clearly defined. In summary, despite several cellular responses are known to be affected by HDAC9, many aspects of its network of interactions still remain to be defined.

Protein kinase D participates in cardiomyocyte hypertrophy by regulating extracellular signal-regulated and myocyte enhancer factor 2D

OBJECTIVE

Cardiomyocyte hypertrophy is an important feature of hypertension. However, its molecular underpinnings, especially the signaling cascades, remain unclear. Here we hypothesized that a protein kinase D (PKD)-dependent extracellular signal-regulated kinase 5 (ERK5) pathway was able to regulate downstream myocyte enhancer factor 2D (MEF2D), affecting prohypertrophic responses to angiotensin II (Ang II).

METHODS

Neonatal rat cardiomyocytes from 2- to 3-day-old Sprague-Dawley rats were prepared and Western blot, real-time quantitative PCR and immunofluorescence staining were used to assess the activation and translocation of pathway signaling molecules. Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) expression and [3H]-leucine (Leu) incorporation were measured to determine cell hypertrophy.

RESULTS

Elevated levels of phosphorylated PKD (p-PKD) and ERK5 (p-ERK5) were observed in cardiomyocytes stimulated with Ang II, while silencing protein kinase C epsilon (PKCɛ) resulted in significantly lower levels of p-PKD. Furthermore, Ang II-induced ERK5 activated translocation was mediated by the PKD pathway. Consequently, inhibiting PKCɛ, PKD and ERK5 by siRNA significantly attenuated Ang II-induced MEF2D activation, ANP and BNP mRNA expression, and [3H]-Leu incorporation.

CONCLUSIONS

Our studies are the first to show that the PKCɛ/PKD/ERK5/MEF2D pathway plays an important role in the cardiomyocyte hypertrophy response to Ang II.

Silencing of MEF2D by siRNA Loaded Selenium Nanoparticles for Ovarian Cancer Therapy

BACKGROUND

Delivery of therapeutic small interfering RNA (siRNA) via functionalized nanoparticles holds great promise for cancer therapy. However, developing a safe and efficient delivery carrier of siRNA is a challenging issue.

METHODS

RGDfC peptide was used to modify the surface of selenium nanoparticles (SeNPs) to synthesize a biocompatible siRNA delivery vehicle (R-SeNPs), and MEF2D-siRNA was loaded onto R-SeNPs to prepare a functionalized selenium nanoparticle R-Se@MEF2D-siRNA. The chemical properties of R-SeNPs were characterized, and the anticancer efficacy as well as related mechanisms of R-Se@MEF2D-siRNA were further explored.

RESULTS

R-Se@MEF2D-siRNA was significantly taken up by SKOV3 cells and could enter SKOV3 cells mainly in the clathrin-associated endocytosis way. The result of in vitro siRNA release demonstrated that R-Se@MEF2D-siRNA could release MEF2D-siRNA quicker in a microenvironment simulating a lysosomal environment in tumor cells compared to a normal physiological environment. The results of qRT-PCR assay proved that R-Se@MEF2D-siRNA could effectively silence the expression of the MEF2D gene in SKOV3 cells. R-Se@MEF2D-siRNA remarkably suppressed the proliferation of SKOV3 cells and further triggered its apoptosis. In addition, R-Se@MEF2D-siRNA had the capability to disrupt mitochondrial membrane potential (MMP) in SKOV3 cells and resulted in the overproduction of reactive oxygen species (ROS), indicating that mitochondrial dysfunction and ROS generation played an important role in the apoptosis of SKOV3 cells induced by R-Se@MEF2D-siRNA. In vivo, R-Se@MEF2D-siRNA also exhibited excellent antitumor activity mainly through decreasing tumor cells proliferation and triggering their apoptosis in tumor-bearing nude mice.

CONCLUSION

R-Se@MEF2D-siRNA provides an alternative strategy for ovarian cancer treatment in the clinic.

Molecular markers in ALL: Clinical implications

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer and remains a main cause of death in children despite recent improvements in cure rates. In the past decade, development of massively parallel sequencing has enabled large scale genome profiling studies of ALL, which not only led to identification of new subtypes in both B-cell precursor ALL (BCP-ALL) and T-cell ALL (T-ALL), but has also identified potential new therapeutic approaches to target vulnerabilities of many subtypes. Several of these approaches have been validated in preclinical models and are now being formally evaluated in prospective clinical trials. In this review, we provide an overview of the recent advances in our knowledge of genomic bases of BCP-ALL, T-ALL, and relapsed ALL, and discuss their clinical implications.

Staurosporine and venetoclax induce the caspase-dependent proteolysis of MEF2D-fusion proteins and apoptosis in MEF2D-fusion (+) ALL cells

MEF2D-fusion (M-fusion) genes are newly discovered recurrent gene abnormalities that are detected in approximately 5 % of acute lymphoblastic leukemia (ALL) cases. Their introduction to cells has been reported to transform cell lines or increase the colony formation of bone marrow cells, suggesting their survival-supporting ability, which prompted us to examine M-fusion-targeting drugs. To identify compounds that reduce the protein expression level of MEF2D, we developed a high-throughput screening system using 293T cells stably expressing a fusion protein of MEF2D and luciferase, in which the protein expression level of MEF2D was easily measured by a luciferase assay. We screened 3766 compounds with known pharmaceutical activities using this system and selected staurosporine as a potential inducer of the proteolysis of MEF2D. Staurosporine induced the proteolysis of M-fusion proteins in M-fusion (+) ALL cell lines. Proteolysis was inhibited by caspase inhibitors, not proteasome inhibitors, suggesting caspase dependency. Consistent with this result, the growth inhibitory effects of staurosporine were stronger in M-fusion (+) ALL cell lines than in negative cell lines, and caspase inhibitors blocked apoptosis induced by staurosporine. We identified the cleavage site of MEF2D-HNRNPUL1 by caspases and confirmed that its caspase cleavage-resistant mutant was resistant to staurosporine-induced proteolysis. Based on these results, we investigated another Food and Drug Administration-approved caspase activator, venetoclax, and found that it exerted similar effects to staurosporine, namely, the proteolysis of M-fusion proteins and strong growth inhibitory effects in M-fusion (+) ALL cell lines. The present study provides novel insights into drug screening strategies and the clinical indications of venetoclax.

MEF2D upregulation protects neurons from oxygen-glucose deprivation/re-oxygenation-induced injury by enhancing Nrf2 activation

Accumulating evidence suggests that myocyte enhancer factor 2D (MEF2D) is a pro-survival factor for neurons. However, whether MEF2D is involved in protecting neurons from cerebral ischemia/reperfusion injury remains unknown. The current study was designed to investigate the exact role and mechanism of MEF2D in regulating oxygen-glucose deprivation/re-oxygenation (OGD/R)-induced neuronal injury, an in vitro model used to study cerebral ischemia/reperfusion injury. MEF2D expression was significantly induced in neurons in response to OGD/R injury. Functional analysis demonstrated that MEF2D upregulation significantly rescued the decreased viability of OGD/R-injured neurons and suppressed OGD/R-induced apoptosis and reactive oxygen species (ROS) production. By contrast, MEF2D knockdown increased the sensitivity of neurons to OGD/R-induced injury. Moreover, MEF2D overexpression increased the expression of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and enhanced the activation of Nrf2 antioxidant signaling. However, Nrf2 knockdown partially blocked the MEF2D-mediated neuroprotective effect in OGD/R-exposed neurons. Overall, these results reveal that MEF2D overexpression attenuates OGD/R-induced injury by enhancing Nrf2-mediated antioxidant signaling. These findings suggest that MEF2D may serve as a neuroprotective target with a potential application for treatment of cerebral ischemia/reperfusion injury.

miR-217-regulated MEF2D-HDAC5/ND6 signaling pathway participates in the oxidative stress and inflammatory response after cerebral ischemia

Multiple factors are known to contribute to the pathogenesis of cerebral ischemic injury, including microRNAs (miRNAs). However, the precise mechanism of miRNAs involvement in cerebral ischemia remains largely unclear. In the current study, we found that miR-217 was significantly upregulated in ischemic stroke models, and the upregulation of miR-217 was associated with the development of post-stroke cognitive impairment. Further investigation revealed that myocyte enhancer factor 2D (MEF2D) was the direct target of miR-217. In vitro experiments showed that miR-217 promoted aggregation of histone deacetylase 5 (HDAC5) in cell nuclei by targeting MEF2D, which led to decreased expression of interleukin (IL)-10. In addition, miR-217 inhibited the expression of NADH dehydrogenase subunit 6 (ND6) in a MEF2D-dependent manner. Overexpression of MEF2D can reverse oxygen-glucose deprivation (OGD)-induced downregulation of ND6 and OGD-mediated neuronal apoptosis, and also reduce the elevated generation of reactive oxygen species (ROS) induced by OGD. Additionally, we found that in vivo administration of MEF2D overexpression plasmids increased IL-10 production and ameliorated cognitive impairment after cerebral ischemia. Taken together, these findings reveal a novel pathogenetic mechganism of cerebral ischemia-related brain injury involving the miR-217/MEF2D/HDAC5 axis and the miR-217/MEF2D/ND6 axis.

FGF22 promotes generation of ribbon synapses through downregulating MEF2D

Cochlear ribbon synapses play a pivotal role in the prompt and precise acoustic signal transmission from inner hair cells (IHCs) to the spiral ganglion neurons, while noise and aging can damage ribbon synapses, resulting in sensorineural hearing loss. Recently, we described reduced fibroblast growth factor 22 (FGF22) and augmented myocyte enhancer factor 2D (MEF2D) in an ototoxicity mouse model with impaired ribbon synapses. Here, we investigated the mechanisms that underlie the FGF22/MEF2D- regulated impairment of ribbon synapses. We generated adeno-associated virus (AAV) carrying FGF22, shFGF22, MEF2D, shMEF2D, calcineurin (CalN), shCalN or corresponding scramble controls for transduction of cultured mouse hair cells. We found that FGF22 was a suppressor for MEF2D, but not vice versa. Moreover, FGF22 likely induced increases in the calcium influx into IHCs to activate CalN, which subsequently inhibited MEF2D. Cochlear infusion of AAV-shFGF22 activated MEF2D, reduced ribbon synapse number and impaired hearing function, which were all abolished by co-infusion of AAV-shMEF2D. Hence, our data suggest that the ribbon synapses may be regulated by FGF22/calcium/CalN/MEF2D signaling, which implied novel therapeutic targets for hearing loss.

A novel transcript of MEF2D promotes myoblast differentiation and its variations associated with growth traits in chicken

Background

Development of skeletal muscle is closely related to broiler production traits. The myocyte-specific enhancer binding factor (MEF) 2D gene (MEF2D) and its variant transcripts play important parts in myogenesis.

Methods

To identify the transcript variants of chicken MEF2D gene and their function, this study cloned chicken MEF2D gene and identified its transcript variants from different tissue samples. The expression levels of different transcripts of MEF2D gene in different tissues and different periods were measured, and their effects on myoblast proliferation and differentiation were investigated. Variations in MEF2D were identified and association analysis with chicken production traits carried out.

Results

Four novel transcript variants of MEF2D were obtained, all of which contained highly conserved sequences, including MADS-Box and MEF2-Domain functional regions. Transcript MEF2D-V4 was expressed specifically in muscle, and its expression was increased during embryonic muscle development. The MEF2D-V4 could promote differentiation of chicken myoblasts and its expression was regulated by RBFOX2. The single nucleotide polymorphism g.36186C > T generated a TAG stop codon, caused MEF2D-V4 to terminate translation early, and was associated with several growth traits, especially on early body weight.

Conclusion

We cloned the muscle-specific transcript of MEF2D and preliminarily revealed its role in embryonic muscle development.

ZEB1 activated-VPS9D1-AS1 promotes the tumorigenesis and progression of prostate cancer by sponging miR-4739 to upregulate MEF2D

Prostate cancer (PCa) is a destructive malignancy with a bad prognosis. LncRNA VPS9D1-AS1 has recently been delineated as an oncogene in some kinds of tumor, whereas, the function of VPS9D1-AS1 in PCa remains to be clarified. In this study, we researched its underlying role in PCa. The expression of VPS9D1-AS1 was conspicuously upregulated in PCa tissues and cells. And absence of VPS9D1-AS1 inhibited cell proliferation, migration and invasion, and promoted cell apoptosis in PCa. In addition, VPS9D1-AS1 overexpression led to opposite results. Furthermore, VPS9D1-AS1/MEF2D could sponge with miR-4739. VPS9D1-AS1/MEF2D and miR-4739 were inversely correlated in tumor cells. And the expression of miR-4739 is markedly downregulated in PCa, meanwhile, that of MEF2D exhibited the opposite tendency. However, MEF2D was positively regulated by VPS9D1-AS1. Moreover, MEF2D upregulation offset the suppressive effects of VPS9D1-AS1 deficiency on cell proliferation, migration and invasion in PCa. Additionally, ZEB1 contained the binding sites of VPS9D1-AS1 promoter, and there existed positive relation between them. Taken together, above results illustrated that ZEB1 activated-VPS9D1-AS1 promotes the tumorigenesis and progression of PCa by sponging miR-4739 to upregulate MEF2D, which offering a new useful reference for studying the development process of PCa.

SORBS2, mediated by MEF2D, suppresses the metastasis of human hepatocellular carcinoma by inhibitiing the c-Abl-ERK signaling pathway

The RBP sorbin and SH3 domain-containing 2 (SORBS2) has been reported to be a tumor suppressor and is dysregulated in several cancer types. Nonetheless, the exact function and mechanism of action of SORBS2 in hepatocellular carcinoma (HCC) remain unclear. In this study, we found that expression levels of SORBS2 were significantly lower in HCC tissues than that in normal tissue samples, and underexpression of SORBS2 was associated with lower overall survival tates of patients with HCC. In HCC cell lines, SORBS2 overexpression inhibited cell migration, invasion, and epithelial-mesenchymal transition, whereas SORBS2 inhibition yielded the opposite results. In vivo metastasis assays confirmed that overexpression of SORBS2 markedly inhibited HCC metastasis. Mechanistically, SORBS2 exerted tumor-suppressive effects on HCC by inhibiting the c-Abl/ERK signaling pathway. Furthermore, MEF2D, which binds to the promoter of SORBS2, was identified as an upstream regulator of SORBS2 and reduced SORBS2 expression. Our data suggest that SORBS2, downregulated by MEF2D, suppresses HCC metastasis through the c-Abl/ERK signaling pathway and has the potential to serve as a novel prognostic marker or therapeutic target in HCC.

Recovery in the Myogenic Program of Congenital Myotonic Dystrophy Myoblasts after Excision of the Expanded (CTG)n Repeat

The congenital form of myotonic dystrophy type 1 (cDM) is caused by the large-scale expansion of a (CTG•CAG)n repeat in DMPK and DM1-AS. The production of toxic transcripts with long trinucleotide tracts from these genes results in impairment of the myogenic differentiation capacity as cDM’s most prominent morpho-phenotypic hallmark. In the current in vitro study, we compared the early differentiation programs of isogenic cDM myoblasts with and without a (CTG)2600 repeat obtained by gene editing. We found that excision of the repeat restored the ability of cDM myoblasts to engage in myogenic fusion, preventing the ensuing myotubes from remaining immature. Although the cDM-typical epigenetic status of the DM1 locus and the expression of genes therein were not altered upon removal of the repeat, analyses at the transcriptome and proteome level revealed that early abnormalities in the temporal expression of differentiation regulators, myogenic progression markers, and alternative splicing patterns before and immediately after the onset of differentiation became normalized. Our observation that molecular and cellular features of cDM are reversible in vitro and can be corrected by repeat-directed genome editing in muscle progenitors, when already committed and poised for myogenic differentiation, is important information for the future development of gene therapy for different forms of myotonic dystrophy type 1 (DM1).

How advanced are we in targeting novel subtypes of ALL? Best Pract Res Clin Haematol. 2019;32:101095. [PMID: 31779973 DOI: 10.1016/j.beha.2019.101095]

Despite high cure rates in children, acute lymphoblastic leukemia (ALL) remains a leading cause of cancer death in the young, and the likelihood of treatment failure increases with age. With the exception of tyrosine kinase inhibitors, there have been few advances in repurposing or developing new therapeutic approaches tailored to vulnerabilities of ALL subtypes or individual cases. Large-scale genome profiling studies conducted over the last decade promise to improve ALL outcomes by refining risk stratification and modulation of therapeutic intensity, and by identifying new targets and pathways for immunotherapy. Many of these approaches have been validated in preclinical models and now merit testing in clinical trials. This review discusses the advances in our understanding of the genomic taxonomy and ontogeny of B-progenitor ALL, with an emphasis on those discoveries of clinical importance.

Neuronal Myocyte-Specific Enhancer Factor 2D (MEF2D) Is Required for Normal Circadian and Sleep Behavior in Mice

The transcription factor, myocyte enhancer factor-2 (MEF2), is required for normal circadian behavior in Drosophila; however, its role in the mammalian circadian system has not been established. Of the four mammalian Mef2 genes, Mef2d is highly expressed in the suprachiasmatic nucleus (SCN) of the hypothalamus, a region critical for coordinating peripheral circadian clocks. Using both conventional and brain-specific Mef2d KO (Mef2d ^-/-) mouse lines, we demonstrate that MEF2D is essential for maintaining the length of the circadian free-running period of locomotor activity and normal sleep patterns in male mice. Crossing Mef2d ^-/- with Per2::luc reporter mice, we show that these behavioral changes are achieved without altering the endogenous period of the master circadian oscillator in the SCN. Together, our data suggest that alterations in behavior in Mef2d ^-/- mice may be the result of an effect on SCN output, rather than an effect on timekeeping within the SCN itself. These findings add to the growing body of evidence that MEF2 proteins play important roles in the brain.SIGNIFICANCE STATEMENT These studies are the first to show a role for MEF2 proteins in the brain outside of the hippocampus, and our findings suggest that these proteins may play diverse roles in the CNS. It is important to continue to build on our understanding of the roles of proteins acting in the SCN because SCN dysfunction underlies jet lag in humans and influences the response to shift work schedules, which are now known as risk factors for the development of cancer. Our work on MEF2D could be the basis for opening new lines of research in the development and regulation of circadian rhythms.

Long noncoding RNA DLEU1 aggravates glioma progression via the miR-421/MEF2D axis

Background

Long noncoding RNA (lncRNA) deleted in lymphocytic leukemia 1 (DLEU1) was reported to be involved in the development and progression of multiple cancers. However, the accurate expression pattern, biological function and potential molecular mechanism of DLEU1 in glioma are not yet known. The present study investigated the role of DLEU in the development and progression of glioma, as well as the potential mechanism played by DLEU1 in glioma.

Materials and methods

The levels of DLEUI in glioma tissues and cell lines were examined using quantitative real-time PCR. The potential effects of DLEU1 on the proliferation, mobility, invasion and apoptosis of glioma cells were evaluated using corresponding in vitro experiments. The association between DLEU1 and microRNA (miR)-421 was also determined using luciferase reporter activity and RNA immunoprecipitation (RIP) assays.

Results

The results revealed that DLEU1 was significantly upregulated in glioma tissues and cell lines. Increased DLEU1 was positively associated with the high-grade carcinoma (III-IV). Functional studies revealed that knockdown of DLEU1 expression by siRNA led to decreased proliferation, migration and invasion and increased apoptosis in human glioma cells. Furthermore, luciferase reporter activity and RIP assays confirmed that DLEUI could act as a competing endogenous RNA (ceRNA) for miR-421 that functioned as a tumor suppressor in glioma. Moreover, inhibition miR-421 partially restored the effect of DLEU1 knockdown on the glioma cells. DLEU1 could regulate myocyte enhancer factor 2D (MEF2D) expression, a known target of miR-421 in glioma cells.

Conclusion

Taken together, these findings suggested that DLEU1 regulated MEF2D expression to promote glioma progression by sponging miR-421 and that DLEU1 might be a potential therapeutic target for glioma.

Overexpression of MEF2D contributes to oncogenic malignancy and chemotherapeutic resistance in ovarian carcinoma

The transcription factor MEF2 promotes survival in various cell types and a number of studies indicate that abnormal regulation of MEF2 is linked to oncogenicity in several carcinomas. We have found that MEF2D, a member of the MEF2 family, is upregulated in Ovarian Cancer (OC). Immunohistochemistry analysis of tumor sections of 402 OC patients revealed that MEF2D is significantly elevated at the protein level. We have also found that the expression level of MEF2D is associated with cisplatin-resistance and poor prognosis by a retrospective analysis. Furthermore, Downregulation of MEF2D by siRNA reduces proliferation and invasiveness of OC cells SKOV3 and OVCAR3, induces apoptosis in vitro, and abolishes OVCAR3 tumorigenicity in xenograft model. Mechanistic study via ChIP analysis identified two of MEF2D-targeted genes, HPSE and IKBKE, which are associated with tumor invasion and chemotherapy-resistance, in accord with MEF2D expression in OC. Remarkably, knock-down of MEF2D invariably lead to the downregulation of IKBKE and reversed cisplatin (DDP)-resistance in cisplatin-resistant cells SKOV3-DDP. Our results suggest that MEF2D promotes malignant biological behaviors and cisplatin-resistance in OC and establish MEF2D as a new therapeutic target in OC treatment.

Long non-coding RNA EPIC1 inhibits viability and invasion of osteosarcoma cells by promoting MEF2D ubiquitylation

BACKGROUND

Long non-coding RNAs (lncRNAs) can modulate gene expression through different mechanisms, but the fundamental molecular mechanism behind EPIC1 and osteosarcoma (OS) was poorly understood.

METHODS

Bone tumor tissues and the matched normal tissues were obtained from 36 OS patients who received tumor resection from 2014 to 2018. The expression of EPIC1 and MEF2D was determined by quantitative real-Time PCR and western blotting. Cell viability and invasion were evaluated by MTT assay and transwell assay. The animal xenograft model was also established.

RESULTS

EPIC1 was down-regulated, but MEF2D was up-regulated in OS tissues and OS cell lines. Overexpression of EPIC1 inhibited cell viability and invasion of OS cells. Targeting relationship between EPIC1 and MEF2D was confirmed by RNA pull-down and RNA immunoprecipitation (RIP). The MEF2D protein binding to ubiquitin was significantly increased in OS cells overexpressing EPIC1. The co-transfection with pcDNA-EPIC1 and pcDNA-MEF2D rescued the inhibition of cell viability and invasion caused by the overexpression of EPIC1. Overexpression of EPIC1 suppressed tumor growth in the OS xenograft model.

CONCLUSION

Our findings indicated that overexpression of EPIC1 inhibited cell viability and invasion of OS cells by promoting MEF2D ubiquitylation, which provided innovative lncRNA and protein targets for treating OS.

Muscle A-kinase-anchoring protein-β-bound calcineurin toggles active and repressive transcriptional complexes of myocyte enhancer factor 2D

Myocyte enhancer factor 2 (MEF2) transcription factors are key regulators of the development and adult phenotype of diverse tissues, including skeletal and cardiac muscles. Controlled by multiple post-translational modifications, MEF2D is an effector for the Ca²⁺/calmodulin-dependent protein phosphatase calcineurin (CaN, PP2B, and PPP3). CaN-catalyzed dephosphorylation promotes the desumoylation and acetylation of MEF2D, increasing its transcriptional activity. Both MEF2D and CaN bind the scaffold protein muscle A-kinase-anchoring protein β (mAKAPβ), which is localized to the nuclear envelope, such that C2C12 skeletal myoblast differentiation and neonatal rat ventricular myocyte hypertrophy are inhibited by mAKAPβ signalosome targeting. Using immunoprecipitation and DNA-binding assays, we now show that the formation of mAKAPβ signalosomes is required for MEF2D dephosphorylation, desumoylation, and acetylation in C2C12 cells. Reduced MEF2D phosphorylation was coupled to a switch from type IIa histone deacetylase to p300 histone acetylase binding that correlated with increased MEF2D-dependent gene expression and ventricular myocyte hypertrophy. Together, these results highlight the importance of mAKAPβ signalosomes for regulating MEF2D activity in striated muscle, affirming mAKAPβ as a nodal regulator in the myocyte intracellular signaling network.

Neuroprotection Against MPP+-Induced Cytotoxicity Through the Activation of PI3-K/Akt/GSK3β/MEF2D Signaling Pathway by Rhynchophylline, the Major Tetracyclic Oxindole Alkaloid Isolated From Uncaria rhynchophylla

Rhynchophylline is a major tetracyclic oxindole alkaloid in Uncaria rhynchophylla, which has been extensively used as traditional herb medicine for the prevention of convulsions and hypertension. However, there is still little evidence about the neuroprotective effects of rhynchophylline for Parkinson’s disease (PD), a neurodegenerative condition currently without any effective cure. In this present study, the neuroprotective molecular mechanisms of rhynchophylline were investigated in a cellular model associated with PD. It is shown that rhynchophylline (10–50 μM) greatly prevented neurotoxicity caused by 1-methyl-4-phenylpyridinium ion (MPP⁺) in primary cerebellar granule neurons, as evidenced by the promotion of cell viability as well as the reversal of dysregulated protein expression of Bax/Bcl-2 ratio. Very encouragingly, we found that rhynchophylline markedly enhanced the activity of the transcription factor myocyte enhancer factor 2D (MEF2D) at both basal and pathological conditions using luciferase reporter gene assay, and reversed the inhibition of MEF2D caused by MPP⁺. Additionally, pharmacological inhibition of PI3-Kinase or short hairpin RNA-mediated gene down-regulation of MEF2D abrogated the protection provided by rhynchophylline. Furthermore, Western blot analysis revealed that rhynchophylline could potentiate PI3-K/Akt to attenuate GSK3β (the MEF2D inhibitor) in response to MPP⁺ insult. In conclusion, rhynchophylline inhibits MPP⁺-triggered neurotoxicity by stimulating MEF2D via activating PI3-K/Akt/GSK3β cascade. Rhynchophylline is served as a novel MEF2D enhancer and might be a potential candidate for further preclinical study in the prevention of PD.

The Long Noncoding RNA D63785 Regulates Chemotherapy Sensitivity in Human Gastric Cancer by Targeting miR-422a

Gastric cancer is one of the most prevalent tumor types in the world. Chemotherapy is the most common choice for cancer treatment. However, chemotherapy resistance and adverse side effects limit its clinical applications. Aberrant expression of long noncoding RNAs (lncRNAs) has been found in various stages of gastric cancer development and progression. In this study, we identified that an oncogenic lncRNA, long intergenic non-protein-coding RNA D63785 (lncR-D63785), is highly expressed in gastric cancer tissues and cells. Silencing of lncR-D63785 inhibited cell proliferation, cell migration and invasion in gastric cancer cell lines and reduced tumor volume and size in mice. We found that the expression of lncR-D63785 was inversely correlated with microRNA 422a (miR-422a) expression, which was involved in the downregulation of expression of myocyte enhancer factor-2D (MEF2D) and drug sensitivity. Knockdown of lncR-D63785 increased the expression of miR-422a and the sensitivity of gastric cancer cells to apoptosis induced by the anticancer drug doxorubicin (DOX). This indicates that lncR-D63785 acts as a competitive endogenous RNA (ceRNA) of miR-422a and promotes chemoresistance by blocking miR-422-dependent suppression of MEF2D. Together, our results suggest that the therapeutic suppression of lncR-D63785 alone or in combination with chemotherapeutic agents may be a promising strategy for treating gastric cancer.

[Adult acute lymphoblastic leukemia: update on pathophysiology and management]

For a long time, treatment for adult acute lymphoblastic leukemia (ALL) lacked significant improvements. Since 2000, new approaches, such as the treatments of adolescent and young adult ALL using pediatric-like protocols and Ph+ ALL treatments using tyrosine kinase inhibitor-combined chemotherapies. Further improvements are expected from the use of pediatric-like protocols to whole adults, and the use of newly approved anti-cancer drugs, such as inotuzumab ozogamicin and blinatumomab. Furthermore, comprehensive genetic analyses using next generation sequencing technology have recently discovered new recurrent fusion genes of ALL, such as DUX4 fusion genes, ZNF384 fusion genes, and MEF2D fusion genes. In this review, I will introduce these frontline studies and discuss about the treatment of patients with adult ALL.

MEF2 and the tumorigenic process, hic sunt leones

While MEF2 transcription factors are well known to cooperate in orchestrating cell fate and adaptive responses during development and adult life, additional studies over the last decade have identified a wide spectrum of genetic alterations of MEF2 in different cancers. The consequences of these alterations, including triggering and maintaining the tumorigenic process, are not entirely clear. A deeper knowledge of the molecular pathways that regulate MEF2 expression and function, as well as the nature and consequences of MEF2 mutations are necessary to fully understand the many roles of MEF2 in malignant cells. This review discusses the current knowledge of MEF2 transcription factors in cancer.

miR-30a suppresses osteosarcoma proliferation and metastasis by downregulating MEF2D expression

Many studies have revealed that microRNAs (miRNAs) play crucial roles in cancer development and progression. miRNA-30a (miR-30a), as a member of the miR-30 family, has been implicated in various cancers. However, the role of miR-30a in osteosarcoma remains unclear. In the current study, we found that miR-30a was significantly downregulated in osteosarcoma tissues and cell lines by using quantitative real-time polymerase chain reaction (qRT-PCR). In addition, miR-30a could inhibit cancer cell growth, migration, and invasion in vitro. Furthermore, bioinformatics of miRNA target prediction and luciferase reporter assay indicated that MEF2D is a direct target of miR-30a. miR-30a was able to reduce the mRNA and protein expression of MEF2D as assessed using RT-PCR and Western blotting assay. Interestingly, overexpression of MEF2D partially reversed the miR-30a-reduced cell proliferation, migration, and invasion of osteosarcoma cell, indicating that miR-30a suppresses osteosarcoma cell proliferation and metastasis partially mediated by inhibition of MEF2D. Overall, our study demonstrated that miR-30a functions as a tumor suppressor by targeting MEF2D in osteosarcoma, providing a promising prognostic biomarker and a therapeutic strategy for osteosarcoma.

Downregulation of miR-30a is associated with proliferation and invasion via targeting MEF2D in cervical cancer

Accumulating studies have revealed that microRNAs serve crucial roles in cancer development and progression. MicroRNA-30a (miR-30a) has been implicated in various cancer types. However, the role of miR-30a in cervical cancer remains unclear. In the current study, a reverse transcription-quantitative polymerase chain reaction (RT-qPCR) assay revealed that miR-30a was significantly downregulated in cervical cancer tissues compared with adjacent normal tissues, and in the cervical cancer cell lines HeLa, SiHa and Ca-Ski compared with GH329 normal cervical epithelial cells. A functional assay using miR-30a mimic demonstrated that miR-30a could inhibit the growth and invasion of cervical cancer cells. Additionally, bioinformatics-based prediction and luciferase reporter assays indicated that MEF2D is a direct target of miR-30a. Transfection with miR-30a reduced the mRNA expression and protein levels of MEF2D, as determined using RT-qPCR and western blot analyses. Furthermore, MEF2D expression was negatively correlated with that of miR-30a in cervical cancers. Overall, the present study demonstrated that miR-30a functions as a tumor suppressor by targeting MEF2D in cervical cancer, which may provide the basis for a prognostic biomarker or therapeutic strategy for cervical cancer.

MiR-665 regulates VSMCs proliferation via targeting FGF9 and MEF2D and modulating activities of Wnt/β-catenin signaling

Abnormal proliferation of vascular smooth muscle cells (VSMCs) contributes to the development of cardiovascular diseases. Studies have showed the great impact of microRNAs (miRNAs) on the cell proliferation in VSMCs. This study examined the in vitro functional roles of miR-665 in the VSMCs and explored the underlying molecular mechanisms. The mRNA and protein expression levels were determined by qRT-PCR and western blot assays, respectively. CCK-8, transwell invasion and wound healing assays were performed to measure VSMCs proliferation, invasion and migration, respectively. The miR-665 targeted-3'UTR of fibroblast growth factor 9 (FGF9) and myocyte enhancer factor 2D (MEF2D) was confirmed by luciferase reporter assay. Platelet-derived growth factor-bb (PDGF-bb) and 20% serum promoted cell proliferation and suppressed the expression of miR-665 in VSMCs. In vitro functional assays demonstrated that miR-665 inhibited VSMCs proliferation, invasion and migration. Bioinformatics analysis showed that FGF9 and MEF2D were found to be downstream targets of miR-665. Luciferase report assay confirmed that FGF9 and MEF2D 3'UTRs are direct targets of miR-665, and miR-665 overexpression suppressed both the mRNA and protein expression levels of FGF9 and MEF2D. Furthermore, rescue experiments showed that enforced expression of FGF9 or MEF2D attenuated the inhibitory effects of miR-665 on VSMCs proliferation. More importantly, overexpression of miR-665 also suppressed the mRNA and protein expression levels of β-catenin, c-myc and cyclin D1. In summary, miR-665 suppressed the VSMCs proliferation, invasion and migration via targeting FGF9 and MEF2D, and the in vitro effects of miR-665 on VSMCs may be associated with modulation of Wnt/β-catenin signaling activities.

Methylene blue attenuates neuroinflammation after subarachnoid hemorrhage in rats through the Akt/GSK-3β/MEF2D signaling pathway

Subarachnoid hemorrhage (SAH) is a serious medical problem with few effective pharmacotherapies available, and neuroinflammation has been identified as an important pathological process in early brain injury (EBI) after SAH. Methylene blue (MB) is an older drug that has been recently proven to exert extraordinary neuroprotective effects in several brain insults. However, no study has reported the beneficial effects of MB in SAH. In the current investigation, we studied the neuroprotective effects of MB in EBI after SAH and focused on its anti-inflammatory role. A total of 303 rats were subjected to an endovascular perforation process to produce an SAH model. We found that MB could significantly ameliorate brain edema secondary to BBB disruption and alleviate neurological dysfunction after SAH. MB administration also promoted the phosphorylation of Akt and GSK-3β, leading to an increased concentration of MEF2D in the nucleus. The cytokine IL-10 was up-regulated, and IL-1β, IL-6 and TNF-α were down-regulated after MB administration. MB administration could also alleviate neutrophil infiltration and microglia activation after SAH. MK2206, a selective inhibitor of Akt, abolished the neuroprotective effects of MB, inhibited the phosphorylation of Akt and prevented the nuclear localization of MEF2D. MK2206 also reduced the expression of IL-10 and increased the expression of pro-inflammatory cytokines. In conclusion, these data suggested that MB could ameliorate neuroinflammatory responses after SAH, and its anti-inflammatory effects might be exerted via activation of the Akt/GSK-3β/MEF2D pathway.