MEF2C Expression Research Articles

The unique functions of Runx1 in skeletal muscle maintenance and regeneration are facilitated by an ETS interaction domain.

The conserved Runt-related (RUNX) transcription factor family are master regulators of developmental and regenerative processes. Runx1 and Runx2 are expressed in satellite cells (SC) and in skeletal myotubes. Conditional deletion of Runx1 in adult SC negatively impacted self-renewal and impaired skeletal muscle maintenance even though Runx2 expression persisted. Runx1 deletion in C2C12 cells that retain Runx2 expression identified unique molecular functions of Runx1 that cannot be compensated by Runx2. The reduced myoblast fusion in vitro caused by Runx1 loss was due in part to ectopic expression of Mef2c, a target repressed by Runx1. Structure-function analysis demonstrated that the Ets-interacting MID/EID region of Runx1, absent from Runx2, is critical to Runx1 myoblast function and for Etv4 binding. Analysis of ChIP-seq datasets from Runx1 (T-cells, muscle) versus Runx2 (preosteoblasts) dependent tissues identified a composite Ets:Runx motif enriched in Runx1-dependent tissues. The Ets:Runx composite motif was enriched in peaks open exclusively in ATAC-seq datasets from WT cells compared to ATAC peaks unique to Runx1KO cells. Thus, engagement of a set of targets by the RUNX1/ETS complex define the non-redundant functions of Runx1.

The circular RNA circNFIX regulates MEF2C expression in muscle satellite cells in spastic cerebral palsy.

Cerebral palsy (CP) is a pediatric onset disorder with poorly understood molecular causes and progression, making early diagnosis difficult. Circular RNAs (circRNAs) are regulatory RNAs that show promise as biomarkers in various diseases but the role of circRNAs in CP is beginning to be understood. This study identified the role of circNFIX in regulating the expression of MEF2C, an important transcription factor for sarcomere development. We found that circNFIX is downregulated in the muscle cells of individuals with CP, and its localization shifts towards the nucleus as visualized using single molecule resolution imaging. The decreased expression of circNFIX, MEF2C, and MEF2C targets persisted throughout myoblasts to myotubes differentiation, and in the skeletal muscle tissue. Bioinformatic and experimental validation confirmed that circNFIX acts as a sponge for miR373-3p, a microRNA that represses MEF2C translation. In normal muscle, circNFIX de-represses MEF2C translation by sponging miR373-3p, allowing for normal sarcomere generation. In CP, reduced circNFIX expression results in loss of miRNA sponging, leading to lower MEF2C expression and downregulation of sarcomere genes, potentially causing shortened and dysfunctional muscle fibers. Knockdown of circNFIX (KD) reduced myogenic capacity of myoblasts to fuse and form myotubes similar to CP cells evident from the lower fusion index in CP and KD as compared to control myotubes. This the first study reporting reduction of MEF2C in CP and single molecule resolution imaging of circNFIX's subcellular distribution and its role in CP, suggesting circNFIX as a potential therapeutic target and biomarker for early CP diagnosis.

Abstract We083: A new mouse model for the study of cardiogenic TFs Tbx5 , Gata4 , and Mef2c during cardiogenesis

Congenital heart defects (CHDs) are be caused by mutations in genes that drive cardiac development, such as Tbx5 , Gata4 , and Mef2c . Cardiac development, and its transcriptional regulators are also regulated by microRNAs (miRs). These small RNAs target the transcripts of genes in numerous cardiac cell types during embryonic development. We and others have shown that the miR-200 family modulates the transcripts of cardiogenic transcription factors (TFs) Tbx5 , Gata4 , and Mef3c. However, the relationship between these miRs and cardiogenic TFs during in vivo cardiac development is poorly understood. During cardiogenesis, miR-200 family members are highly expressed (E14.5) but reduced in adults (3mo) (Ct Value: miR-200a : 24.3 ± 0.59 v 38.3 ± 0.21; miR-200c : 25.0 ± 0.64 v 32.5 ± 0.16). Using our miR-200 family inhibitor mice models (PMIS), we have found these miRs are required for cardiac development. PMIS-miR-200 embryos are found with a ventral septal defect and poor ventricle wall development, which is lethal by e16.5. At e14.5, PMIS-miR-200 hearts have a significant increase in expression of Tbx5, Gata4, and Mef2c compared to Wild-Type. This induced expression of these TFs is seen within CMs of the ventricle at E14.5. snMulti-Omics of WT and PMIS-miR-200 hearts found a population of CMs enriched in the PMIS-miR-200 hearts. These CMs are marked by expression of Tbx5 , Nppa , and Sox5 . RNA velocity analysis found these CMs to be “progenitor-like” and associated with an early pseudotime. Expression of Tbx5 , Nppa , and Sox5 correlated along the pseudotime with the “progenitor-like” CMs. ATAC-seq showed enrichment of Tbx5 and Mef2c motifs within this new CM cell state. Conclusions: The miR-200 family is a modulator of cardiogenic TFs expression and activity during development. Inhibition of miR-200 induces a CM cell state with “progenitor-like” qualities. Future directions will determine the role of miR- 200 in adult cardiac disease, such as ischemic injury. Our work provides new insights into gene dosage, modulated by miRs, that is required and necessary during cardiac development.

Abstract Mo106: Inhibition of microRNA-200c promotes regeneration of the ischemic injured myocardium through activation of developmental pathways

Ischemic injury and adverse post-infarction myocardial remodeling are major causes of heart failure worldwide. Strategies designed to offset cell death with cardiomyocyte regeneration have, to date, not translated to routine clinical practice. Mir-200c modulates the transcripts of cardiogenic transcription factors (TFs) Tbx5 , Gata4 , Mef2c to promote myocyte maturation. We hypothesized that inhibition of mir-200c activity would result in postnatal myocyte de-differentiation and replication sufficient to ameliorate post-infarction decompensation after ischemic injury. To test this hypothesis, we preformed left coronary ligation on Wild-Type (WT) and transgenic mice expressing an RNA inhibitor against miR-200c ( PMIS-C ). Echocardiographic left ventricular (LV) ejection fraction (EF) fell from 88.41 ± 1.08% (WT) and 90% ± 1.42% ( PMIS-C ) (p=NS) to 28% ± 11.55% (WT) and 36% ± 9.35% at 1 day post injury (DPI) (p =NS). At 21DPI, LVEF was 27% ± 4.31% (WT) and 64% ± 4.25% ( PMIS-C ) [p ≤ 0.0001]. Post-infarction LV chamber dilation was reversed in PMIS-C mice (1.136 ± 0.19 v 0.67 ± 0.06 p ≤ 0.004 LV Vol/mass). By 9 WPI, PMIS-C heart function within non-significantly levels of sham and function prior to injury. These results indicated that inhibiting miR-200c following ischemic injury can recover cardiac function and prevent LV dilation. Moreover, trichrome stain showed a decrease in fibrosis 3 WPI (WT: 57% ± 17.46 v PMIS-C : 12% ± 3.01 p ≤ 0.001) and 9 WPI. To understand the mechanism causing this phenomenon, we analyzed expression of cardiac progenitor markers. Fold change in expression of TFs Tbx5, Gata4, Mef2c, and Isl1 were increased at 1 and 3 DPI in PMIS-C . At 1 WPI, PMIS-C border zone CMs express markers of a “progenitor-like” cell state seen during cardiogenesis. Conclusions: Inhibiting miR-200c abrogates post-infarction LV remodeling and significantly restores LV systolic function. Ongoing studies are investigating the therapeutic use of PMIS-C through delivery via AAV and nanoparticles.

Abstract Mo093: Rescue of Desmin Insufficiency Restores Contractile Function in Cardiomyocytes with MYH7 E848G Dilated Cardiomyopathy Variant

Dilated cardiomyopathy (DCM), characterized by systolic dysfunction, is a significant cause of heart failure. Myosin heavy chain 7 ( MYH7 ) pathogenic variants are common causes of DCM; however, no specific disease-modifying therapy for MYH7 DCM exists. Using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) expressing the pathogenic MYH7 E848G DCM variant, we confirmed hypocontractility at the single cell level as assessed with traction force microscopy. hiPSC-CMs were cultured on polyacrylamide hydrogels with physiological stiffness in 15x100 µm patterned Matrigel-coated rectangles, each containing one cell. Upon 1 Hz electrical stimulation, contracting cells displaced fluorescent beads embedded within the gel, which were measured to estimate twitch force. MYH7 E848G/+ hiPSC-CMs had reduced maximum twitch force (97 ± 11 nN, n=46 cells) compared to MYH7 +/+ hiPSC-CMs (179 ± 18 nN, n=49 cells), recapitulating the disease phenotype. RNAseq analysis of MYH7 E848G/+ hiPSC-CMs compared to isogenic control MYH7 +/+ hiPSC-CMs found significant downregulation of desmin ( DES) (76.4 ± 8.2% reduction, n=4 bio reps), which encodes a muscle-specific type III intermediate filament. Desmin protein expression in MYH7 E848G/+ hiPSC-CMs was significantly attenuated relative to MYH7 +/+ hiPSC-CMs (90.9 ± 1.8% reduction, n=4 bio reps), matching gene expression data. Gene expression of the transcription factor MEF2C , a known transactivator of DES, was also reduced (40.4 ± 7.0% reduction, n=4 bio reps), suggesting MYH7 E848G/+ suppresses the MEF2C - DES signaling axis. We hypothesized restoring desmin protein levels may improve contractility in MYH7 E848G/+ hiPSC-CMs. To test this, we created an adeno-associated virus (AAV9) packaged with full-length desmin cDNA fused with a T2A self-cleaving peptide and mApple fluorescent reporter. hiPSC-CMs were transfected with this mApple-T2A-DES AAV at 1 MOI and contractility was assessed via traction force microscopy. mApple + MYH7 E848G/+ hiPSC-CMs had increased maximum twitch force (141 ± 11 nN, n=75 cells) relative to mApple - MYH7 E848G/+ hiPSC-CMs (65 ± 20 nN, n=21 cells), approaching the maximum twitch force of mApple + MYH7 +/+ hiPSC-CMs (165 ± 10 nN, n=87 cells). In conclusion, suppression of the MEF2C - DES signaling axis is a potential novel mechanism by which pathogenic MYH7 variants cause DCM. By leveraging this mechanistic insight, we found that rescuing desmin insufficiency can partially restore contractile function.

Analysis of LRRN3, MEF2C, SLC22A, and P2RY12 Gene Expression in the Peripheral Blood of Patients in the Early Stages of Parkinson's Disease.

Parkinson's disease (PD) is one of the most common human neurodegenerative diseases. Belated diagnoses of PD and late treatment are caused by its elongated prodromal phase. Thus, searching for new candidate genes participating in the development of the pathological process in the early stages of the disease in patients who have not yet received therapy is relevant. Changes in mRNA and protein levels have been described both in the peripheral blood and in the brain of patients with PD. Thus, analysis of changes in the mRNA expression in peripheral blood is of great importance in studying the early stages of PD. This work aimed to analyze the changes in MEF2C, SLC22A4, P2RY12, and LRRN3 gene expression in the peripheral blood of patients in the early stages of PD. We found a statistically relevant and PD-specific change in the expression of the LRRN3 gene, indicating a disruption in the processes of neuronal regeneration and the functioning of synapses. The data obtained during the study indicate that this gene can be considered a potential biomarker of the early stages of PD.

MiR-1 modulates HDAC4, calmodulin and MAPK1/Erk2 during early atrial differentiation

Abstract Funding Acknowledgements None. Introduction A large diversity of epigenetic factors, such as microRNAs and histones modifications, are known to be capable of regulating gene expression without altering DNA sequence itself. In particular, miR-1 is considered the first essential microRNA in cardiac development. Purpose The aim of this work is to analyze the miR-1 modulation role in cardiac chamber differentiation through specific signaling pathways. Methods By means of microinjections in both primitive endocardial tubes of chick embryo culture, gain- and loss-of-function experiments were performed with premiR-1 and anti-miR-1, respectively. Subsequently, embryos were subjected to whole mount in situ hybridization with Tbx5, Gata4 and AMHC1 probes, as well as immunohistochemistry with Mef2c, HDAC4, Calmodulin/Calm1 and MAPK1/Erk2 antibodies. Also, we carried out RT-qPCR analysis of control and experimental embryos, including CRABPI, CRABPII and retinoic acid receptors (RAR and RXR). Results Our results reveal that miR-1 increases specific atrial gene expression such as Tbx5, Gata4 and AMHC1, while this microRNA diminishes Mef2c expression. Furthermore, we observed that miR-1 upregulates CRABPII and RARß, and downregulates CRABPI, which are three crucial factors in retinoic acid signaling pathway. Interestingly, we also observed that miR-1 actively interacts with HDAC4, Calmodulin and Erk2/MAPK1, key factors involved in Mef2c regulation. Conclusion All these data suggest that miR-1 functions as an epigenetic factor modulating complementary actions performed by retinoic acid and Mef2c, which are required to properly assign cells as sinoatrial precursors.

Aberrant ecotropic viral integration site-1 (EVI-1) and myocyte enhancer factor 2 C gene (MEF2C) in adult acute myeloid leukemia are associated with adverse t (9:22) & 11q23 rearrangements

Acute myeloid leukemia (AML) shows multiple chromosomal translocations & point mutations which can be used to refine risk-adapted therapy in AML patients. Ecotropic viral integration site-1 (EVI-1) & myocyte enhancer factor 2 C gene (MEF2C) are key regulatory transcription factors in hematopoiesis and leukemogenesis & both drive immune escape.This prospective study involved 80 adult de novo AML patients recruited from Oncology Center, Mansoura University, between March 2019 and July 2021. The MEF2C and EVI1 expression were measured using a Taqman probe-based qPCR assay.The results revealed that EVI1 and MEF2C expression were significantly elevated in AML patients as compared to control subjects (p = 0.001. 0.007 respectively). Aberrant expressions of EVI1 and MEF2C showed a significant negative correlation with hemoglobin levels (p = 0.034, 0.025 respectively), & bone marrow blasts (p = 0.007, 0.002 respectively). 11q23 translocation was significantly associated with EVI1 and MEF2C (p = 0.004 and 0.02 respectively). Also, t (9;22) was significantly associated with EVI1 and MEF2C (p = 0.01 and 0.03 respectively), higher expression of EVI1 and MEF2C were significantly associated with inferior outcome after induction therapy (p = 0.001 and 0.018 respectively) and shorter overall survival (p = 0.001, 0.014 respectively).In conclusion, EVI1 & MEF2C were significantly expressed in AML cases. EVI1 & MEF2C overexpression were significantly associated with 11q23 rearrangements and t (9;22) and were indicators for poor outcome in adult AML patients; These results could be a step towards personalized therapy in those patients.

MEF2C contributes to axonal branching by regulating Kif2c transcription.

Neurons are post-mitotic cells, with microtubules playing crucial roles in axonal transport and growth. Kinesin family member 2c (KIF2C), a member of the Kinesin-13 family, possesses the ability to depolymerize microtubules and is involved in remodelling the microtubule lattice. Myocyte enhancer factor 2c (MEF2C) was initially identified as a regulator of muscle differentiation but has recently been associated with neurological abnormalities such as severe cognitive impairment, stereotyping, epilepsy and brain malformations when mutated or deleted. However, further investigation is required to determine which target genes MEF2C acts upon to influence neuronal function as a transcription regulator. Our data demonstrate that knockdown of both Mef2c and Kif2c significantly impacts spinal motor neuron development and behaviour in zebrafish. Luciferase reporter assays and chromosome immunoprecipitation assays, along with down/upregulated expression analysis, revealed that MFE2C functions as a novel transcription regulator for the Kif2c gene. Additionally, the knockdown of either Mef2c or Kif2c expression in E18 cortical neurons substantially reduces the number of primary neurites and axonal branches during neuronal development in vitro without affecting neurite length. Finally, depletion of Kif2c eliminated the effects of overexpression of Mef2c on the neurite branching. Based on these findings, we provided novel evidence demonstrating that MEF2C regulates the transcription of the Kif2c gene thereby influencing the axonal branching.

CircMEF2C(2, 3) modulates proliferation and adipogenesis of porcine intramuscular preadipocytes by miR-383/671-3p/MEF2C axis

Circular RNA is a special category of non-coding RNA that has emerged as epigenetic regulator of adipose tissue development. However, the mechanism governing intramuscular adipogenesis of circRNA remains largely uncharted. In this study, circMEF2C(2, 3), looped by MEF2C exons 2 and 3, was identified from thepig MEF2C gene. Expression of circMEF2C(2, 3) is upregulated in early stage of intramuscular adipogenesis and muscular tissue of lean pigs (DLY pig). Subsequently, overexpression or knockdown of circMEF2C(2, 3) reflected that it participates in promoting proliferation and inhibiting adipogenic differentiation in porcine intramuscular preadipocytes and murine C3H10T1/2 cells. Mechanically, circMEF2C(2, 3) competitively combined with miR-383 and miR-671-3p to the 3'-UTR of MEF2C, which maintains MEF2C expression in regulating proliferation and adipogenesis. In summary, circMEF2C(2, 3) is a key regulator in the proliferation and adipogenic differentiation of intramuscular adipogenesis, suggesting its potential as a multi-target strategy for adipose development and associated diseases.

Abstract 1227: Novel combination therapies to overcome non-genetic/adaptive menin inhibitor resistance in AML with MLL1r or mtNPM1

Abstract In AML with MLL1 rearrangement or MLL1 fusion proteins (FP), the N-terminus of MLL1 becomes fused to over 80 partner proteins resulting in an aberrant leukemic transcriptional program including dysregulated expression of HOXA9, MEIS1, PBX3, FLT3, MEF2C and CDK6. On the other hand, in mutant NPM1 AML cells, wild type MLL1 is the main regulator of HOXA9, MEIS1 and FLT3, promoting self-renewal of myeloid progenitor cells. Menin inhibitors have been developed that disrupt the binding of Menin to MLL1 leading to reduced activity of HOXA9 and MEIS1 and repression of MLL1 or MLL1-FP target genes. Clinical trials have demonstrated that Menin inhibitors (MI) are well-tolerated and clinical remissions have been observed in patients with relapsed/refractory AML harboring MLLr. Unfortunately, most patients either fail to respond or eventually relapse. MI-resistance in AML with MLL1r or mtNPM1 is either due to recently described mutations in the MI-binding domain of Menin or is non-genetic/adaptive, due to dysregulated epigenome/transcriptome/proteome. In the present studies, through repeated shocks with LD90 dosing of MI, followed by drug washout and recovery, we have generated MLL1r (MV4-11-MITR) and mtNPM1 (OCI-AML3-MITR) AML cell lines that are tolerant/resistant (TR) to MI with LD50 values greater than 1 μM. Whole exome sequencing confirmed that these cells were lacking in new driver mutations. We determined that resistance in the MITR cells was not due to presence of hotspot mutations in Menin. ChIP-Seq analysis of H3K27Ac showed that the activities of super enhancers and core transcriptional regulatory circuitry was altered in both MITR cell types. Non-genetic/adaptive resistance to MI also concordantly reduced genome wide ATAC-Seq and RNA-Seq peaks in the OCI-AML3-MITR cells with significant depletion of MEIS1, IGF2BP2, BCL2, and PBX3, with concomitant induction of leukemia stem cell associated CLEC12A and CD244 expressions. A domain-specific CRISPR screen in MV4-11-MITR cells identified several druggable co-dependencies (e.g. EP300 and MOZ) and co-enrichments (SMARCA4, CREBBP and BRD4) with MI, suggesting them as potential mechanisms of non-genetic/adaptive MI resistance. Consistent with these findings, co-treatment with SMARCA2/SMARCA4 (chromatin remodeler ATPases) inhibitor FHD-286 and the BETi OTX015 or the MI SNDX-50469 exerted synergistic lethality in MV4-11-MITR and OCI-AML3-MITR cells as well as in PD MITR AML cells with MLL1r or mtNPM1. Co-treatment with CBP/p300 inhibitor GNE049 or GNE781 was also synergistic with MI in these cells. In vivo treatment with FHD-286 and OTX015 or SNDX-5613 significantly reduced the AML burden in mice bearing OCI-AML3-MITR xenografts. These findings underscore preclinical activity of epigenetically-targeted agent-based combinations and highlight their promise in overcoming MI resistance in AML with MLL1r or mtNPM1. Citation Format: Warren C. Fiskus, Christopher P. Mill, Jessica Piel, Murphy Hentemann, Christine E. Birdwell, Kaberi Das, John A. Davis, Hanxi Hou, Tapan M. Kadia, Naval Daver, Sanam Loghavi, Branko Cuglievan, Courtney D. DiNArdo, Kapil N. Bhalla. Novel combination therapies to overcome non-genetic/adaptive menin inhibitor resistance in AML with MLL1r or mtNPM1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1227.

Molecular profiling of the hippocampus of children with autism spectrum disorder

Several lines of evidence point to a key role of the hippocampus in Autism Spectrum Disorders (ASD). Altered hippocampal volume and deficits in memory for person and emotion related stimuli have been reported, along with enhanced ability for declarative memories. Mouse models have demonstrated a critical role of the hippocampus in social memory dysfunction, associated with ASD, together with decreased synaptic plasticity. Chondroitin sulfate proteoglycans (CSPGs), a family of extracellular matrix molecules, represent a potential key link between neurodevelopment, synaptic plasticity, and immune system signaling. There is a lack of information regarding the molecular pathology of the hippocampus in ASD. We conducted RNAseq profiling on postmortem human brain samples containing the hippocampus from male children with ASD (n = 7) and normal male children (3–14 yrs old), (n = 6) from the NIH NeuroBioBank. Gene expression profiling analysis implicated molecular pathways involved in extracellular matrix organization, neurodevelopment, synaptic regulation, and immune system signaling. qRT-PCR and Western blotting were used to confirm several of the top markers identified. The CSPG protein BCAN was examined with multiplex immunofluorescence to analyze cell-type specific expression of BCAN and astrocyte morphology. We observed decreased expression of synaptic proteins PSD95 (p < 0.02) and SYN1 (p < 0.02), increased expression of the extracellular matrix (ECM) protease MMP9 (p < 0.03), and decreased expression of MEF2C (p < 0.03). We also observed increased BCAN expression with astrocytes in children with ASD, together with altered astrocyte morphology. Our results point to alterations in immune system signaling, glia cell differentiation, and synaptic signaling in the hippocampus of children with ASD, together with alterations in extracellular matrix molecules. Furthermore, our results demonstrate altered expression of genes implicated in genetic studies of ASD including SYN1 and MEF2C.

Decoding the genetic symphony: Profiling protein-coding and long noncoding RNA expression in T-acute lymphoblastic leukemia for clinical insights.

T-acute lymphoblastic leukemia (T-ALL) is a heterogeneous malignancy characterized by the abnormal proliferation of immature T-cell precursors. Despite advances in immunophenotypic classification, understanding the molecular landscape and its impact on patient prognosis remains challenging. In this study, we conducted comprehensive RNA sequencing in a cohort of 35 patients with T-ALL to unravel the intricate transcriptomic profile. Subsequently, we validated the prognostic relevance of 23 targets, encompassing (i) protein-coding genes-BAALC, HHEX, MEF2C, FAT1, LYL1, LMO2, LYN, and TAL1; (ii) epigenetic modifiers-DOT1L, EP300, EML4, RAG1, EZH2, and KDM6A; and (iii) long noncoding RNAs (lncRNAs)-XIST, PCAT18, PCAT14, LINC00202, LINC00461, LINC00648, ST20, MEF2C-AS1, and MALAT1 in an independent cohort of 99 patients with T-ALL. Principal component analysis revealed distinct clusters aligning with immunophenotypic subtypes, providing insights into the molecular heterogeneity of T-ALL. The identified signature genes exhibited associations with clinicopathologic features. Survival analysis uncovered several independent predictors of patient outcomes. Higher expression of MEF2C, BAALC, HHEX, and LYL1 genes emerged as robust indicators of poor overall survival (OS), event-free survival (EFS), and relapse-free survival (RFS). Higher LMO2 expression was correlated with adverse EFS and RFS outcomes. Intriguingly, increased expression of lncRNA ST20 coupled with RAG1 demonstrated a favorable prognostic impact on OS, EFS, and RFS. Conclusively, several hitherto unreported associations of gene expression patterns with clinicopathologic features and prognosis were identified, which may help understand T-ALL's molecular pathogenesis and provide prognostic markers.

LncRNA GPRC5D-AS1 as a ceRNA inhibits skeletal muscle aging by regulating miR-520d-5p.

Sarcopenia induced by muscle aging is associated with negative outcomes in a variety of diseases. Long non-coding RNAs are a class of RNAs longer than 200 nucleotides with lower protein coding potential. An increasing number of studies have shown that lncRNAs play a vital role in skeletal muscle development. According to our previous research, lncRNA GPRC5D-AS1 is selected in the present study as the target gene to further study its effect on skeletal muscle aging in a dexamethasone-induced human muscle atrophy cell model. As a result, GPRC5D-AS1 functions as a ceRNA of miR-520d-5p to repress cell apoptosis and regulate the expression of muscle regulatory factors, including MyoD, MyoG, Mef2c and Myf5, thus accelerating myoblast proliferation and differentiation, facilitating development of skeletal muscle. In conclusion, lncRNA GPRC5D-AS1 could be a novel therapeutic target for treating sarcopenia.

A Longitudinal Single-Cell Atlas of Treatment Response in Pediatric AML

Introduction: Pediatric acute myeloid leukemia (pAML) is a heterogeneous disease in terms of driver alterations, treatment response and patient outcomes. Although approximately 90% of pAML patients respond to initial treatment, tumours relapse frequently. Despite large-scale genomic sequencing efforts, it remains elusive why tumors relapse. Previously, mutations have been identified that affect transcriptional regulation, indicating that epigenetic processes may contribute to treatment resistance in pAML. We therefore studied how tumor epigenetic patterns, transcriptional regulation and cell populations change over the course of treatment using single-cell ATAC sequencing (scATAC-seq) and single-cell RNA sequencing (scRNA-seq) in pediatric populations. Methods: We profiled 330,047 cells using scRNA-seq and 353,984 cells using scATAC-seq derived from 28 uniformly treated pAML patients, driven by either MLL fusions, CBFB fusions, RUNX1 fusions, FLT3-ITD or other aberrations (i.e. CEBPA mutations). All patients were enrolled in the AAML1031 trial (https://childrensoncologygroup.org/aaml1031), a randomized phase 3 clinical trial that investigated the addition of Bortezomib (BTZ) and Sorafenib to standard treatment modalities. Samples were obtained serially at diagnosis, at remission and at relapse and single-cell profiles were compared between these stages. Results: We identified malignant and non-malignant populations in the scATAC-seq and scRNA-seq data, showing that in all cases, malignant cells from patients at diagnosis were distinct from those taken at relapse. Major differences between diagnosis and relapse were associated with differentiation, and by inferring distinct cell populations we identified that relapsed cell populations appeared to shift towards a more primitive state. The extent of this shift was dependent on the genetic subtype and the effects were more pronounced in MLL-rearranged tumors. To identify the candidate mechanisms and transcription factors involved in this shift we studied the monocytic, lymphocytic and erythrocytic lineages in non-malignant cells and compared these to the tumor at diagnosis and relapse. Based on motif enrichment we found that across all different subgroups, transcription factors (TFs) that drive monocytic differentiation (i.e. CEBPA) have a lower activity while TFs driving erythrocytic and lymphocytic differentiation (i.e. TCF3) have a higher activity. Analysis of hematopoietic stem-like and progenitor-like cells (HSPC-like) confirmed this change, indicating that the “priming” towards other lineages is not only a result of shifts in cell populations but also a result of rewiring of early progenitors. To investigate this rewiring, we analysed regions of open chromatin that were enriched in malignant HSPCs compared to normal HSPCs across different subgroups. We found that those regions were highly specific to the driving alteration and were enriched for MEF2C binding sites in MLL-driven tumors and AP-1 binding sites in other tumors. Overall, upon relapse MEF2C expression and inferred TF activity appeared to increase, coinciding with an apparent increase in lymphoid priming and early lymphoid factors including LMO2, LYL1 and TCF3, among others. Two cases in the cohort appeared to switch lineage from a monocytic to lymphocytic phenotype and were enriched in CD19 and CD79A positive malignant cells upon relapse. Both cases shared the characteristic that MEF2C was upregulated upon relapse and showed upregulation of typical B-lymphoid transcription factors such as PAX5. Discussion: By generating a large dataset of pediatric AML patient samples collected at diagnosis, remission and relapse, we have identified changes in cellular hierarchies and transcriptional networks that occur upon relapse. Our study shows that shifts in cell populations readily occur upon treatment and are dependent on subgroup-defining alterations. Particularly MLL-rearranged tumors show a high level of plasticity that could explain the poor outcome of this group. Furthermore, we show that tumors appear to adapt their transcriptional programs towards a more “stem-like” state, with a likely higher propensity to differentiate towards other lineages such as the lymphoid lineage. We have identified MEF2C as a possible regulator of these processes, opening a new perspective to target the plasticity of these tumors.

Transcatheter versus surgical aortic valve replacement in patients with aortic stenosis: molecular pathways and correlation with clinical and echocardiographic parameters

Abstract Background Transcatheter aortic valve replacement (TAVR) has reformed the management of aortic stenosis (AS), being firstly approved in high-risk patients and becoming progressively a therapeutic alternative to surgery (surgical aortic valve replacement, SAVR) for all the risk categories. Several data pointed out the role of inflammation, oxidative stress, and pathological remodeling in AS natural history. The aim of our study is to investigate the molecular pathways involved in the AS pathophysiology and in the early response to AV replacement in patients subjected to percutaneous or surgical approach. Secondary aims are to evaluate the variation in clinical and echocardiographic parameters of left ventricular (LV) function before and after procedure. Methods We enrolled 36 consecutive patients with a diagnosis of severe AS and preserved ejection fraction (17 SAVR patients and 19 TAVR patients). Biological samples, clinical and echocardiographic evaluation were gained before (T0) and 72 hours after the procedure (T1). We performed 3 gene expression arrays on pooled cDNA from peripheral blood mononuclear cells of the 2 study groups. Results SAVR patients were significantly younger (p=0.0003) and with a lower STS score (p=0.0004). After the procedure, SAVR showed a longer ICU stay (p=0.0019) and a more frequent need of inotropes/vasopressors (p=0.006). Gene expression analysis revealed a reduction of the pro-apoptotic gene CASP3 (n=13; median, IQR: 1.01, 0..89-1.62 for T0 vs 0.68, 0.58-0.85 for T1; p=0.019) and of the transcription factor MEF2C (n=13; 1.00, 0.57-1.31 for T0 vs 0.56, 0.42-0.87 for T1; p=0.028) in TAVR patients, together with significantly increased levels of the antioxidant molecule GPX1 (n=14; 1.04, 0..71-1.34 for T0 vs 1.37, 1.23-1.85 for T1;p=0.030). In SAVR patients, our data showed increased post-procedural levels of GPX1 (n=6; 0.99, 0.49-1.23 for T0 vs 1.81, 1.27-2.00 for T1; p=0.028), and of the oxidative markers CAT (n=10; 0.40, 0.27-0.69 for T0 vs 1.17, 0.59-2.06 for T1; p=0.022,) and NOX2 (n=8; 0.41, 0.31-0.63 for T0 vs 1.04, 0.73-1.54 for T1; p=0.012) (Fig.1). TAVR patients displayed a direct correlation between the gene expression of molecules involved in apoptosis (CASP3), myocardial remodeling (GTF2I, MEF2C) and oxidative stress (MPO, CAT, TXNIP) and indexed left ventricular volumes (Fig.2A), while SAVR patients showed an inverse correlation with LVEF for GTF2I, MEF2C, CAT and MPO gene expression levels (Fig.2B). Conclusions By demonstrating 1) a significant post-procedural downregulation in the expression of genes involved in oxidative stress pathways for TAVR patients if compared with SAVR patients, and 2) a significant correlation of the basal levels of genes involved in apoptosis, myocardial remodeling, and oxidative stress with post-procedural ventricular volumes and LVEF, our study provides a biological rationale to support the percutaneous approach for AS patients, independently from their class of risk.Figure 1Figure 2

Conditional Loss of MEF2C Expression in Osteoclasts Leads to a Sex-Specific Osteopenic Phenotype.

Myocyte enhancement factor 2C (MEF2C) is a transcription factor studied in the development of skeletal and smooth muscles. Bone resorption studies have exhibited that the reduced expression of MEF2C contributes to osteopetrosis and the dysregulation of pathological bone remodeling. Our current study aims to determine how MEF2C contributes to osteoclast differentiation and to analyze the skeletal phenotype of Mef2c-cKO mice (Cfms-cre; Mef2cfl/fl). qRT-PCR and Western blot demonstrated that Mef2c expression is highest during the early days of osteoclast differentiation. Osteoclast genes, including c-Fos, c-Jun, Dc-stamp, Cathepsin K, and Nfatc1, had a significant reduction in expression, along with a reduction in osteoclast size. Despite reduced CTX activity, female Mef2c cKO mice were osteopenic, with decreased bone formation as determined via a P1NP ELISA, and a reduced number of osteoblasts. There was no difference between male WT and Mef2c-cKO mice. Our results suggest that Mef2c is critical for osteoclastogenesis, and that its dysregulation leads to a sex-specific osteopenic phenotype.

Ascorbic acid and salvianolic acid B enhance the valproic acid and 5-azacytidinemediated cardiac differentiation of mesenchymal stem cells.

Cardiovascular diseases remain a major cause of death globally. Cardiac cells once damaged, cannot resume the normal functioning of the heart. Bone marrow derived mesenchymal stem cells (BM-MSCs) have shown the potential to differentiate into cardiac cells. Epigenetic modifications determine cell identity during embryo development via regulation of tissue specific gene expression. The major epigenetic mechanisms that control cell fate and biological functions are DNA methylation and histone modifications. However, epigenetic modifiers alone are not sufficient to generate mature cardiac cells. Various small molecules such as ascorbic acid (AA) and salvianolic acid B (SA) are known for their cardiomyogenic potential. Therefore, this study is aimed to examine the synergistic effects of epigenetic modifiers, valproic acid (VPA) and 5-azacytidine (5-aza) with cardiomyogenic molecules, AA and SA in the cardiac differentiation of MSCs. BM-MSCs were isolated, propagated, characterized, and then treated with an optimized dose of VPA or 5-aza for 24h. MSCs were maintained in a medium containing AA and SA for 21 days. All groups were assessed for the expression of cardiac genes and proteins through q-PCR and immunocytochemistry, respectively. Results show that epigenetic modifiers VPA or 5-aza in combination with AA and SA significantly upregulate the expression of cardiac genes MEF2C, Nkx2.5, cMHC, Tbx20, and GATA-4. In addition, VPA or 5-aza pretreatment along with AA and SA enhanced the expression of the cardiac proteins connexin-43, GATA-4, cTnI, and Nkx2.5. These findings suggest that epigenetic modifiers valproic acid and 5-azacytidine in combination with ascorbic acid and salvianolic acid B promote cardiac differentiation of MSCs. This pretreatment strategy can be exploited for designing future stem cell based therapeutic strategies for cardiovascular diseases.

LKB1 signaling is altered in skeletal muscle of a Duchenne muscular dystrophy mouse model.

The potential role of liver kinase B1 (LKB1) in the altered activation of the master metabolic and epigenetic regulator adenosine monophosphate-activated protein kinase (AMPK) in Duchenne muscular dystrophy has not been investigated so far. Hence, we analyzed both gene and protein levels of LKB1 and its related targets in gastrocnemius muscles of adult C57BL/10 mdx mice and D2 mdx mice, a model with a more severe dystrophic phenotype, as well as the sensitivity of the LKB1-AMPK pathway to AMPK activators, such as chronic exercise. Our data show, for the first time, a reduction in the levels of LKB1 and accessory proteins, MO25 and STRADα, in both mdx strains versus the respective wild type, which was further impaired by exercise, in parallel with a lack of further phosphorylation of AMPK. The AMPK-like kinase salt-inducible kinase (SIK) and class II histone deacetylases, along with expression of the HDAC target gene Mef2c, were also altered, supporting an impairment of LKB1-SIK-class II histone deacetylase signaling. Our results demonstrate that LKB1 may be involved in dystrophic progression, paving the way for future preclinical studies.

LncRNA MCM3AP-AS1 is downregulated in atherosclerosis and sponges miR-448 to suppress vascular smooth muscle cell proliferation.

Long noncoding RNA MCM3AP-AS1 plays critical roles in cancers, but its role in atherosclerosis is yet to be elucidated. The expression of MCM3AP-AS1 in atherosclerosis and control plasma samples were measured by RT-qPCR. IntaRNA was used to predict potential base pairings between MCM3AP-AS1 and miR-448, and the results were confirmed by a dual luciferase activity assay. Cell proliferation assay was performed to explore the role of overexpression of MCM3AP-AS1, miR-448, and myocyte enhancer factor 2 (MEF2)-C in the proliferation of human aortic smooth muscle cells (HAOSMCs). MCM3AP-AS1 was downregulated in atherosclerosis and directly interacted with miR-448, which is a critical player in the proliferation of HAOSMCs, indicating its involvement in atherosclerosis. However, MCM3AP-AS1 and miR-448 showed no role in regulating the expression of each other. In contrast, overexpression of MCM3AP-AS1 increased the expression levels of MEF2-C, which can be targeted by miR-448. Moreover, MCM3AP-AS1 was found to inhibit the effects of miR-448 overexpression on both HAOSMC proliferation and MEF2-C expression. MCM3AP-AS1 is downregulated in atherosclerosis and sponges miR-448 to suppress the proliferation of HAOSMCs.