Linking actin dynamics and gene transcription to drive cellular motile functions

Breast cancer cells promote osteoclast differentiation in an MRTF-dependent paracrine manner

Bone is a frequent site for breast cancer metastasis. The vast majority of breast cancer-associated metastasis is osteolytic in nature, and RANKL (receptor activator for nuclear factor κB)-induced differentiation of bone marrow-derived macrophages to osteoclasts (OCLs) is a key requirement for osteolytic metastatic growth of cancer cells. In this study, we demonstrate that Myocardin-related transcription factor (MRTF) in breast cancer cells plays an important role in paracrine modulation of RANKL-induced OCL differentiation. This is partly attributed to MRTFs' critical role in maintaining the basal cellular expression of connective tissue growth factor (CTGF), findings that align with a strong positive correlation between CTGF expression and MRTF-A gene signature in the human disease context. Luminex analyses reveal that MRTF depletion in breast cancer cells has a broad impact on OCL-regulatory cell-secreted factors that extend beyond CTGF. Experimental metastasis studies demonstrate that MRTF depletion diminishes OCL abundance and bone colonization of breast cancer cells in vivo, suggesting that MRTF inhibition could be an effective strategy to diminish OCL formation and skeletal involvement in breast cancer. In summary, this study highlights a novel tumor-extrinsic function of MRTF relevant to breast cancer metastasis.

Claudin 7 suppresses invasion and metastasis through repression of a smooth muscle actin program

Metastasis initiates when cancer cells escape from the primary tumor, which requires changes to intercellular junctions. Claudins are transmembrane proteins that form the tight junction, and their expression is reduced in aggressive breast tumors. However, claudins' roles during breast cancer metastasis remain unclear. We used gain- and loss-of-function genetics in organoids isolated from murine breast cancer models to establish that Cldn7 suppresses invasion and metastasis. Transcriptomic analysis revealed that Cldn7 knockdown induced smooth muscle actin (SMA)-related genes and a broader mesenchymal phenotype. We validated our results in human cell lines, fresh human tumor tissue, bulk RNA-seq, and public single-cell RNA-seq data. We consistently observed an inverse relationship between Cldn7 expression and expression of SMA-related genes. Furthermore, knockdown and overexpression of SMA-related genes demonstrated that they promote breast cancer invasion. Our data reveal that Cldn7 suppresses breast cancer invasion and metastasis through negative regulation of SMA-related and mesenchymal gene expression.

New insights into the pharmacological inhibition of SRF activity: Key inhibitory targets and mechanisms

Serum Response Factor (SRF) is a critical regulatory transcription factor widely expressed across cell types and is essential for animal survival. Excessive SRF activity has been linked to various pathological conditions and diseases, including cardiovascular diseases, cancers and neurodegenerative disorders, making the inhibition of SRF hyperactivity a promising therapeutic strategy. This review summarizes recent advancements in the discovery and development of SRF inhibitors, their regulatory mechanisms, and their respective molecular foundations. These insights deepen our understanding of current therapeutic potentials, paving the way for novel approaches to treat diseases associated with SRF hyperactivity.

Regulation of formin INF2 and its alteration in INF2-linked inherited disorders

Formins are proteins that catalyze the formation of linear filaments made of actin. INF2, a formin, is crucial for correct vesicular transport, microtubule stability and mitochondrial division. Its activity is regulated by a complex of cyclase-associated protein and lysine-acetylated G-actin (KAc-actin), which helps INF2 adopt an inactive conformation through the association of its N-terminal diaphanous inhibitory domain (DID) with its C-terminal diaphanous autoinhibitory domain. INF2 activation can occur through calmodulin binding, KAc-actin deacetylation, G-actin binding, or association with the Cdc42 GTPase. Mutations in the INF2 DID are linked to focal segmental glomerulosclerosis (FSGS), affecting podocytes, and Charcot-Marie-Tooth disease, which affects Schwann cells and leads to axonal loss. At least 80 pathogenic DID variants of INF2 have been identified, with potential for many more. These mutations disrupt INF2 regulation, leading to excessive actin polymerization. This in turn causes altered intracellular trafficking, abnormal mitochondrial dynamics, and profound transcriptional reprogramming via the MRTF/SRF complex, resulting in mitotic abnormalities and p53-mediated cell death. This sequence of events could be responsible for progressive podocyte loss during glomerular degeneration in FSGS patients. Pharmacological targeting of INF2 or actin polymerization could offer the therapeutic potential to halt the progression of FSGS and improve outcomes for patients with INF2-linked disease.

Mechanistic insights into the treatment of pulmonary fibrosis with bioactive components from traditional chinese medicine via matrix stiffness-mediated EMT

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease with limited therapeutic options. Our previous research has shown that the Jinshui Huanxian formula (JHF) is effective in treating IPF. However, the biomechanical mechanisms of its refined components, known as the effective-component compatibility of JHF II (ECC-JHF II), are not well understood.

PURPOSE

This study aims to explore how bioactive components from traditional Chinese medicine (TCM) impact the biomechanical progression of pulmonary fibrosis.

STUDY DESIGN AND METHODS

A mouse model of pulmonary fibrosis was established by a single intratracheal instillation of bleomycin (Bleomycin). Pulmonary function, pathological changes, collagen deposition, lung tissue stiffness, and EMT markers were evaluated at the end of the study. Polyethylene glycol hydrogels with adjustable stiffness were used to mimic both normal and pathological lung conditions. The effects of ECC-JHF II on matrix stiffness-mediated EMT were assessed by quantitative real-time PCR, western blot, and immunofluorescence. The biomechanical mechanisms underlying ECC-JHF II on EMT and pulmonary fibrosis were verified both in vivo and in vitro.

RESULTS

ECC-JHF II significantly improved bleomycin (Bleomycin)-induced pulmonary fibrosis in mice, manifested as increased tidal volume and 50 % tidal volume expiratory flow, reduced lung tissue stiffness, and decreased EMT markers. Histopathological analysis showed reduced inflammation, alveolar damage, and collagen deposition. In vitro, ECC-JHF II reversed the EMT phenotypic transition induced by substrate stiffness, demonstrated by the upregulation of E-cadherin, occludin, and zonula occluden-1, and the downregulation of N-cadherin, vimentin, caldesmon 1 and tropomyosin 1. Moreover, ECC-JHF II could inhibit integrin/ROCK/MRTF signaling in vitro and in vivo. Silencing integrin β1 or activating it with pyrintegrin further confirmed the role of integrin β1 in the mechanotransduction pathway and the efficacy of ECC-JHF II.

CONCLUSION

Taken together, the findings of this study indicate that ECC-JHF II exerts a therapeutic effect on pulmonary fibrosis through the attenuation of lung tissue stiffness and inhibition of EMT, potentially via the integrin/ROCK/MRTF signaling pathway.

Breast cancer cells promote osteoclast differentiation in an MRTF-dependent paracrine manner

Bone is a frequent site for breast cancer metastasis. The vast majority of breast cancer-associated metastasis is osteolytic in nature, and RANKL (receptor activator for nuclear factor κB)-induced differentiation of bone marrow-derived macrophages (BMDMs) to osteoclasts (OCLs) is a key requirement for osteolytic metastatic growth of cancer cells. In this study, we demonstrate that Myocardin-related transcription factor (MRTF) in breast cancer cells plays an important role in paracrine modulation of RANKL-induced osteoclast differentiation. This is partly attributed to MRTF's critical role in maintaining the basal cellular expression of connective tissue growth factor (CTGF), findings that align with a strong positive correlation between CTGF expression and MRTF-A gene signature in the human disease context. Luminex analyses reveal that MRTF depletion in breast cancer cells has a broad impact on OCL-regulatory cell-secreted factors that extend beyond CTGF. Experimental metastasis studies demonstrate that MRTF depletion diminishes OCL abundance and bone colonization breast cancer cells in vivo , suggesting that MRTF inhibition could be an effective strategy to diminish OCL formation and skeletal involvement in breast cancer. In summary, this study highlights a novel tumor-extrinsic function of MRTF relevant to breast cancer metastasis.

SIGNIFICANCE STATEMENT

MRTF, a transcriptional coactivator of SRF, is known to promote breast cancer progression through its tumor-cell-intrinsic function. Whether and how MRTF activity in tumor cells modulates other types of cells in the tumor microenvironment are not clearly understood.This study uncovers a novel tumor-cell-extrinsic function of MRTF in breast cancer cells in promoting osteoclast differentiation partly through CTGF regulation, and further demonstrates MRTF's requirement for bone colonization of breast cancer cells in vivo.Our studies suggest that MRTF inhibition could be an effective strategy to diminish osteoclast formation and skeletal involvement in metastatic breast cancer.

Novel insights into the ROCK-JAK-STAT signaling pathway in upper respiratory tract infections and neurodegenerative diseases

Acute upper respiratory tract infections are a major public health issue, with uncontrolled inflammation triggered by upper respiratory viruses being a significant cause of patient deterioration or death. This study focuses on the Janus kinase-signal transducer and activator of transcription Rho-associated coiled-coil containing protein kinase (JAK-STAT-ROCK) signaling pathway, providing an in-depth analysis of the interplay between uncontrolled inflammation after upper respiratory tract infections and the development of neurodegenerative diseases. It offers a conceptual framework for understanding the lung-brain-related immune responses and potential interactions. The relationship between the ROCK-JAK-STAT signaling pathway and inflammatory immunity is a complex and multi-layered research area and exploring potential common targets could open new avenues for the prevention and treatment of related inflammation.

Can Physicochemical Properties Alter the Potency of Aeroallergens? Part 1 - Aeroallergen Protein Families

PURPOSE OF REVIEW

Respiratory allergies are non-communicable diseases caused by the hypersensitivity of the immune system to environmental aeroallergens. The culprits are aero-transported proteins eliciting respiratory symptoms in sensitized/allergic individuals. This review intends to provide a holistic overview on the categorization of aeroallergens into protein families (Part 1) and to exploit the impact of physicochemical properties on inhalant protein allergenicity (Part 2). This first part will focus particularly on aeroallergen organization into families and how this classification fits their physicochemical properties.

RECENT FINDINGS

Aeroallergen classification into protein families facilitates the identification of common physicochemical properties, thus aiding a better comprehension of known allergens, while predicting the behavior of novel ones. The available online databases gathering important features of aeroallergens are currently scarce. Information on distinct aeroallergen classification is still lacking, as data is dispersed and often outdated, hampering an efficient evaluation of new aeroallergens.

Mediator Subunit Med4 Enforces Metastatic Dormancy in Breast Cancer

Long term survival of breast cancer patients is limited due to recurrence from metastatic dormant cancer cells. However, the mechanisms by which these dormant breast cancer cells survive and awaken remain poorly understood. Our unbiased genome-scale genetic screen in mice identified Med4 as a novel cancer-cell intrinsic gatekeeper in metastatic reactivation. MED4 haploinsufficiency is prevalent in metastatic breast cancer patients and correlates with poorer prognosis. Syngeneic xenograft models revealed that Med4 enforces breast cancer dormancy. Contrary to the canonical function of the Mediator complex in activating gene expression, Med4 maintains 3D chromatin compaction and enhancer landscape, by preventing enhancer priming or activation through the suppression of H3K4me1 deposition. Med4 haploinsufficiency disrupts enhancer poise and reprograms the enhancer dynamics to facilitate extracellular matrix (ECM) gene expression and integrin-mediated mechano-transduction, driving metastatic growth. Our findings establish Med4 as a key regulator of cellular dormancy and a potential biomarker for high-risk metastatic relapse.

Carbon quantum dots in breast cancer modulate cellular migration via cytoskeletal and nuclear structure

Carbon nanomaterials have been widely applied for cutting edge therapeutic applications as they offer tunable physio-chemical properties with economic scale-up options. Nuclear delivery of cancer drugs has been of prime focus since it controls important cellular signaling functions leading to greater anti-cancer drug efficacies. Better cellular drug uptake per unit drug injection drastically reduces severe side-effects of cancer therapies. Similarly, carbon dots (CDs) uptaken by the nucleus can also be used to set-up cutting edge nano delivery systems. In an earlier paper, we showed the cellular uptake and plasma membrane impact of combustion generated yellow luminescing CDs produced by our group from fuel rich combustion reactors in a one-step tunable production. In this paper, we aim to specifically study the nucleus by establishing the uptake kinetics of these combustion-generated yellow luminescing CDs. At sub-lethal doses, after crossing the plasma membrane, they impact the actin and microtubule mesh, affecting cell adhesion and migration; enter nucleus by diffusion processes; modify the overall appearance of the nucleus in terms of morphology; and alter chromatin condensation. We thus establish how this one-step produced, cost and bulk production friendly carbon dots from fuel rich combustion flames can be innovatively repurposed as potential nano delivery agents in cancer cells.

SRF promotes long-range chromatin loop formation and stem cell pluripotency

Serum response factor (SRF) is a transcription factor essential for cell proliferation, differentiation, and migration and is required for primitive streak and mesoderm formation in the embryo. The canonical roles of SRF are mediated by a diverse set of context-dependent cofactors. Here, we show that SRF physically interacts with CTCF and cohesin subunits at topologically associating domain (TAD) boundaries and loop anchors. SRF promotes long-range chromatin loop formation and contributes to TAD insulation. In embryonic stem cells (ESCs), SRF associates with SOX2 and NANOG and contributes to the formation of three-dimensional (3D) pluripotency hubs. Our findings reveal additional roles of SRF in higher-order chromatin organization.

Galectin 3-binding protein (LGALS3BP) depletion attenuates hepatic fibrosis by reducing transforming growth factor-β1 (TGF-β1) availability and inhibits hepatocarcinogenesis

BACKGROUND

Increased Galectin 3-binding protein (LGALS3BP) serum levels have been used to assess hepatic fibrosis stages and the severity of hepatocellular carcinoma (HCC). Considering the crucial role of transforming growth factor-β1 (TGF-β1) in the emergence of these diseases, the present study tested the hypothesis that LGALS3BP regulates the TGF-β1 signaling pathway.

METHODS

The expression levels of LGALS3BP and TGFB1 were analyzed in patients with metabolic dysfunction-associated steatohepatitis (MASH) and HCC. Multiple omics techniques, such as RNA-sequencing, transposase-accessible chromatin-sequencing assay, and liquid chromatography-tandem mass spectrometry proteomics, were used to identify the regulatory mechanisms for the LGALS3BP-TGF-β1 axis. The effects of altered TGF-β1 signaling by LGALS3BP were investigated in conditional LGALS3BP-knockin and LGALS3BP-knockout mice.

RESULTS

In patients with MASH and HCC, the levels of LGALS3BP and TGFB1 exhibited positive correlations. Stimulation of LGALS3BP by the inflammatory cytokine interferon α in HCC cells or ectopic overexpression of LGALS3BP in hepatocytes promoted the expression levels of TGFB1. Aggravated fibrosis was observed in the livers of hepatocyte-specific LGALS3BP-knockin mice, with increased TGFB1 levels. LGALS3BP directly bound to and assembled integrin αV, an integral mediator required for releasing active TGF-β1 from extracellular latent complex with the rearranged F-actin cytoskeleton. The released TGF-β1 activated JunB transcription factor, which in turn promoted the TGF-β1 positive feedback loop. LGALS3BP deletion in the hepatocytes downregulated TGF-β1 signaling and CCl4 induced fibrosis. Moreover, LGALS3BP depletion hindered hepatocarcinogenesis by limiting the availability of fibrogenic TGF-β1.

CONCLUSION

LGALS3BP plays a crucial role in hepatic fibrosis and carcinogenesis by controlling the TGF-β1 signaling pathway, making it a promising therapeutic target in TGF-β1-related diseases.

WISP1 and Macrophage Migration Inhibitory Factor in Respiratory Inflammation: Novel Insights and Therapeutic Potentials for Asthma and COPD

Recent advancements highlight the intricate interplay between the extracellular matrix (ECM) and immune responses, notably in respiratory diseases such as asthma and Chronic Obstructive Pulmonary Disease (COPD). The ECM, a dynamic structural framework within tissues, orches-trates a plethora of cellular processes, including immune cell behavior and tissue repair mecha-nisms. WNT1-inducible-signaling pathway protein 1 (WISP1), a key ECM regulator, controls immune cell behavior, cytokine production, and tissue repair by modulating integrins, PI3K, Akt, β-catenin, and mTOR signaling pathways. WISP1 also induces macrophage migration inhibitory factor (MIF) expression via Src kinases and epidermal growth factor receptor (EGFR) activation. MIF, through its wide range of activities, enhances inflammation and tissue restructuring. Rec-ognized for its versatile roles in regulating the immune system, MIF interacts with multiple immune components, such as the NLRP3 inflammasome, thereby sustaining inflammatory pro-cesses. The WISP1-MIF axis potentially unveils complex molecular mechanisms governing im-mune responses and inflammation. Understanding the intricate roles of WISP1 and MIF in the pathogenesis of chronic respiratory diseases such as asthma and COPD could lead to the identi-fication of novel targets for therapeutic intervention to alleviate disease severity and enhance patient outcomes.

Leiomodin 2 neonatal dilated cardiomyopathy mutation results in altered actin gene signatures and cardiomyocyte dysfunction

Neonatal dilated cardiomyopathy (DCM) is a poorly understood muscular disease of the heart. Several homozygous biallelic variants in LMOD2, the gene encoding the actin-binding protein Leiomodin 2, have been identified to result in severe DCM. Collectively, LMOD2-related cardiomyopathies present with cardiac dilation and decreased heart contractility, often resulting in neonatal death. Thus, it is evident that Lmod2 is essential to normal human cardiac muscle function. This study aimed to understand the underlying pathophysiology and signaling pathways related to the first reported LMOD2 variant (c.1193 G > A, p.Trp398*). Using patient-specific human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and a mouse model harboring the homologous mutation to the patient, we discovered dysregulated actin-thin filament lengths, altered contractility and calcium handling properties, as well as alterations in the serum response factor (SRF)-dependent signaling pathway. These findings reveal that LMOD2 may be regulating SRF activity in an actin-dependent manner and provide a potential new strategy for the development of biologically active molecules to target LMOD2-related cardiomyopathies.

IL-2 delivery to CD8+ T cells during infection requires MRTF/SRF-dependent gene expression and cytoskeletal dynamics

Paracrine IL-2 signalling drives the CD8 + T cell expansion and differentiation that allow protection against viral infections, but the underlying molecular events are incompletely understood. Here we show that the transcription factor SRF, a master regulator of cytoskeletal gene expression, is required for effective IL-2 signalling during L. monocytogenes infection. Acting cell-autonomously with its actin-regulated cofactors MRTF-A and MRTF-B, SRF is dispensible for initial TCR-mediated CD8+ T cell proliferation, but is required for sustained IL-2 dependent CD8+ effector T cell expansion, and persistence of memory cells. Following TCR activation, Mrtfab-null CD8+ T cells produce IL-2 normally, but homotypic clustering is impaired both in vitro and in vivo. Expression of cytoskeletal structural and regulatory genes, most notably actins, is defective in Mrtfab-null CD8+ T cells. Activation-induced cell clustering in vitro requires F-actin assembly, and Mrtfab-null cell clusters are small, contain less F-actin, and defective in IL-2 retention. Clustering of Mrtfab-null cells can be partially restored by exogenous actin expression. IL-2 mediated CD8+ T cell proliferation during infection thus depends on the control of cytoskeletal dynamics and actin gene expression by MRTF-SRF signalling.

The Function of RhoA/ROCK Pathway and MYOCD in Airway Remodeling in Asthma

INTRODUCTION

Asthma is a common chronic respiratory disease characterized by chronic airway inflammation and abnormal airway remodeling. The RhoA/ROCK pathway and myocardin-related transcription factor A (MRTF-A) demonstrate significant associations with the proliferation of airway smooth muscle cells (ASCMs), which tightly correlates with the process of airway remodeling. MYOCD, which is homologous to MRTF-A but specifically expressed in smooth muscle cells, potentially regulates RhoA/ROCK activated cell proliferation and subsequent airway remodeling.

METHODS

The RhoA/ROCK overexpression and silencing cell lines were constructed in vitro, as well as MYOCD overexpression/silencing. The cytoskeleton alterations induced by RhoA/ROCK pathway were identified by the measuring of globular actin and filamentous actin.

RESULTS

The comparison between controls for overexpression/silencing and ROCK overexpression/silencing revealed that MYOCD presented consistent change trends with cytoskeleton and RhoA/ROCK pathway. The ROCK1 facilitates the proliferation and migration of ASCMs. The MYOCD enhanced the proliferation and migration of HASMCs.

CONCLUSION

Our study indicates that Rho/ROCK/MYOCD is a key pathway involved in the migration and proliferation of airway smooth muscle cells. Inhibition of Rho/ROCK may be an effective approach to breaking the vicious cycle of asthmatic ASCMs proliferation, providing a novel strategy in treating asthma airway remodeling.

The SIX2/PFN2 feedback loop promotes the stemness of gastric cancer cells

BACKGROUND

The roles of the transcriptional factor SIX2 have been identified in several tumors. However, its roles in gastric cancer (GC) progression have not yet been revealed. Our objective is to explore the impact and underlying mechanisms of SIX2 on the stemness of GC cells.

METHODS

Lentivirus infection was employed to establish stable expression SIX2 or PFN2 in GC cells. Gain- and loss-of-function experiments were conducted to detect changes of stemness markers, flow cytometry profiles, tumor spheroid formation, and tumor-initiating ability. ChIP, RNA-sequencing, tissue microarray, and bioinformatics analysis were performed to reveal the correlation between SIX2 and PFN2. The mechanisms underlying the SIX2/PFN2 loop-mediated effects were elucidated through tissue microarray analysis, RNA stability assay, IP-MS, Co-Immunoprecipitation, and inhibition of the JNK signaling pathway.

RESULTS

The stemness of GC cells was enhanced by SIX2. Mechanistically, SIX2 directly bound to PFN2's promoter and promoted PFN2 activity. PFN2, in turn, promoted the mRNA stability of SIX2 by recruiting RNA binding protein YBX-1, subsequently activating the downstream MAPK/JNK pathway.

CONCLUSION

This study unveils the roles of SIX2 in governing GC cell stemness, defining a novel SIX2/PFN2 regulatory loop responsible for this regulation. This suggests the potential of targeting the SIX2/PFN2 loop for GC treatment (Graphical Abstracts).

The benzoylphenylurea derivative BPU17 acts as an inhibitor of prohibitin and exhibits antifibrotic activity

Inflammation-induced choroidal neovascularization followed by the epithelial-mesenchymal transition (EMT) of retinal pigment epithelial cells (RPEs) is a cause of neovascular age-related macular degeneration (nAMD). RPE-derived myofibroblasts overproduce extracellular matrix, leading to subretinal fibrosis. We already have demonstrated that benzylphenylurea (BPU) derivatives inhibit the function of cancer-associated fibroblasts. Here, we investigated the anti-myofibroblast effects of BPU derivatives and examined such BPU activity on subretinal fibrosis. A BPU derivative, BPU17, exhibits the most potent anti-myofibroblast activity among dozens of BPU derivatives and inhibits subretinal fibrosis in a mouse model of retinal degeneration. Investigations with primary cultured RPEs reveal that BPU17 suppresses cell motility and collagen synthesis in RPE-derived myofibroblasts. These effects depend on repressing the serum response factor (SRF)/CArG-box-dependent transcription. BPU17 inhibits the expression of SRF cofactor, cysteine and glycine-rich protein 2 (CRP2), which activates the SRF function. Proteomics analysis reveals that BPU17 binds to prohibitin 1 (PHB1) and inhibits the PHB1-PHB2 interaction, resulting in mild defects in mitochondrial function. This impairment causes a decrease in the expression of CRP2 and suppresses collagen synthesis. Our findings suggest that BPU17 is a promising agent against nAMD and the close relationship between PHB function and EMT.

Substrate Curvature Influences Cytoskeletal Rearrangement and Modulates Macrophage Phenotype

Inflammation serves as a critical defense mechanism against pathogens and tissue damage but can lead to chronic diseases, such as cardiovascular disease and diabetes, when dysregulated. Macrophages play a pivotal role in orchestrating inflammatory responses, transitioning from pro-inflammatory M1 to anti-inflammatory M2 phenotypes to resolve inflammation and promote tissue repair. Current approaches to modulate macrophage phenotype predominantly rely on biochemical cues, which may induce systemic side effects. Given the mechanosensitivity of macrophages, this study investigates biophysical cues, specifically substrate curvature, as a localized strategy to regulate macrophage phenotype and minimize systemic repercussions. We hypothesized that substrate curvature influences macrophage immunophenotype by modulating F-actin polymerization. To test this hypothesis, we fabricated spherical microgels with tunable curvatures and characterized their biophysical properties. Our findings indicate that macrophages adhere to microgel surfaces irrespective of curvature, but the curvature significantly alters F-actin dynamics. Furthermore, manipulating cytoskeletal dynamics via selective actin inhibition partially reversed curvature-induced changes in macrophage phenotype. These results underscore the pivotal role of substrate curvature in modulating macrophage behavior and immunophenotype. Overall, our study demonstrates that substrate curvature significantly influences macrophage cytoskeletal dynamics and resulting immunophenotype. This simple approach can be utilized as a localized immunomodulatory treatment for inflammatory diseases.

Endothelial LATS2 is a suppressor of bone marrow fibrosis

Myelofibrosis and osteosclerosis are fibrotic diseases disrupting bone marrow function that occur in various leukemias but also in response to non-malignant alterations in hematopoietic cells. Here we show that endothelial cell-specific inactivation of the Lats2 gene, encoding Hippo kinase large tumor suppressor kinase 2, or overexpression of the downstream effector YAP1 induce myofibroblast formation and lead to extensive fibrosis and osteosclerosis, which impair bone marrow function and cause extramedullary hematopoiesis in the spleen. Mechanistically, loss of LATS2 induces endothelial-to-mesenchymal transition, resulting in increased expression of extracellular matrix and secreted signaling molecules. Changes in endothelial cells involve increased expression of serum response factor target genes, and, strikingly, major aspects of the LATS2 mutant phenotype are rescued by inactivation of the Srf gene. These findings identify the endothelium as a driver of bone marrow fibrosis, which improves understanding of myelofibrotic and osteosclerotic diseases, for which drug therapies are currently lacking.

INF2 formin variants linked to human inherited kidney disease reprogram the transcriptome, causing mitotic chaos and cell death

Mutations in the human INF2 gene cause autosomal dominant focal segmental glomerulosclerosis (FSGS)-a condition characterized by podocyte loss, scarring, and subsequent kidney degeneration. To understand INF2-linked pathogenicity, we examined the effect of pathogenic INF2 on renal epithelial cell lines and human primary podocytes. Our study revealed an increased incidence of mitotic cells with surplus microtubule-organizing centers fostering multipolar spindle assembly, leading to nuclear abnormalities, particularly multi-micronucleation. The levels of expression of exogenous pathogenic INF2 were similar to those of endogenous INF2. The aberrant nuclear phenotypes were observed regardless of the expression method used (retrovirus infection or plasmid transfection) or the promoter (LTR or CMV) used, and were absent with exogenous wild type INF2 expression. This indicates that the effect of pathogenic INF2 is not due to overexpression or experimental cell manipulation, but instead to the intrinsic properties of pathogenic INF2. Inactivation of the INF2 catalytic domain prevented aberrant nuclei formation. Pathogenic INF2 triggered the translocation of the transcriptional cofactor MRTF into the nucleus. RNA sequencing revealed a profound alteration in the transcriptome that could be primarily attributed to the sustained activation of the MRTF-SRF transcriptional complex. Cells eventually underwent mitotic catastrophe and death. Reducing MRTF-SRF activation mitigated multi-micronucleation, reducing the extent of cell death. Our results, if validated in animal models, could provide insights into the mechanism driving glomerular degeneration in INF2-linked FSGS and may suggest potential therapeutic strategies for impeding FSGS progression.

Direct GPCR-EGFR interaction enables synergistic membrane-to-nucleus information transfer

We addressed the heteromerization of the epidermal growth factor receptor (EGFR) with G-protein coupled receptors (GPCR) on the basis of angiotensin-II-receptor-subtype-1(AT1R)-EGFR interaction as proof-of-concept and show its functional relevance during synergistic nuclear information transfer, beyond ligand-dependent EGFR transactivation. Following in silico modelling, we generated EGFR-interaction deficient AT1R-mutants and compared them to AT1R-wildtype. Receptor interaction was assessed by co-immunoprecipitation (CoIP), Förster resonance energy transfer (FRET) and fluorescence-lifetime imaging microscopy (FLIM). Changes in cell morphology, ERK1/2-phosphorylation (ppERK1/2), serum response factor (SRF)-activation and cFOS protein expression were determined by digital high content microscopy at the single cell level. FRET, FLIM and CoIP confirmed the physical interaction of AT1R-wildtype with EGFR that was strongly reduced for the AT1R-mutants. Responsiveness of cells transfected with AT1R-WT or -mutants to angiotensin II or EGF was similar regarding changes in cell circularity, ppERK1/2 (direct and by ligand-dependent EGFR-transactivation), cFOS-expression and SRF-activity. By contrast, the EGFR-AT1R-synergism regarding these parameters was completely absent for in the interaction-deficient AT1R mutants. The results show that AT1R-EGFR heteromerisation enables AT1R-EGFR-synergism on downstream gene expression regulation, modulating the intensity and the temporal pattern of nuclear AT1R/EGFR-information transfer. Furthermore, remote EGFR transactivation, via ligand release or cytosolic tyrosine kinases, is not sufficient for the complete synergistic control of gene expression.

Suppression of smooth muscle cell inflammation by myocardin-related transcription factors involves inactivation of TANK-binding kinase 1

Myocardin-related transcription factors (MRTFs: myocardin/MYOCD, MRTF-A/MRTFA, and MRTF-B/MRTFB) suppress production of pro-inflammatory cytokines and chemokines in human smooth muscle cells (SMCs) through sequestration of RelA in the NF-κB complex, but additional mechanisms are likely involved. The cGAS-STING pathway is activated by double-stranded DNA in the cytosolic compartment and acts through TANK-binding kinase 1 (TBK1) to spark inflammation. The present study tested if MRTFs suppress inflammation also by targeting cGAS-STING signaling. Interrogation of a transcriptomic dataset where myocardin was overexpressed using a panel of 56 cGAS-STING cytokines showed the panel to be repressed. Moreover, MYOCD, MRTFA, and SRF associated negatively with the panel in human arteries. RT-qPCR in human bronchial SMCs showed that all MRTFs reduced pro-inflammatory cytokines on the panel. MRTFs diminished phosphorylation of TBK1, while STING phosphorylation was marginally affected. The TBK1 inhibitor amlexanox, but not the STING inhibitor H-151, reduced the anti-inflammatory effect of MRTF-A. Co-immunoprecipitation and proximity ligation assays supported binding between MRTF-A and TBK1 in SMCs. MRTFs thus appear to suppress cellular inflammation in part by acting on the kinase TBK1. This may defend SMCs against pro-inflammatory insults in disease.

The Mediator Med23 controls a transcriptional switch for muscle stem cell proliferation and differentiation in muscle regeneration

Muscle stem cells (MuSCs) contribute to a robust muscle regeneration process after injury, which is highly orchestrated by the sequential expression of multiple key transcription factors. However, it remains unclear how key transcription factors and cofactors such as the Mediator complex cooperate to regulate myogenesis. Here, we show that the Mediator Med23 is critically important for MuSC-mediated muscle regeneration. Med23 is increasingly expressed in activated/proliferating MuSCs on isolated myofibers or in response to muscle injury. Med23 deficiency reduced MuSC proliferation and enhanced its precocious differentiation, ultimately compromising muscle regeneration. Integrative analysis revealed that Med23 oppositely impacts Ternary complex factor (TCF)-targeted MuSC proliferation genes and myocardin-related transcription factor (MRTF)-targeted myogenic differentiation genes. Consistently, Med23 deficiency decreases the ETS-like transcription factor 1 (Elk1)/serum response factor (SRF) binding at proliferation gene promoters but promotes MRTF-A/SRF binding at myogenic gene promoters. Overall, our study reveals the important transcriptional control mechanism of Med23 in balancing MuSC proliferation and differentiation in muscle regeneration.

Structural anisotropy results in mechano-directional transport of proteins across nuclear pores

The nuclear pore complex regulates nucleocytoplasmic transport by means of a tightly synchronized suite of biochemical reactions. The physicochemical properties of the translocating cargos are emerging as master regulators of their shuttling dynamics. As well as being affected by molecular weight and surface-exposed amino acids, the kinetics of the nuclear translocation of protein cargos also depend on their nanomechanical properties, yet the mechanisms underpinning the mechanoselectivity of the nuclear pore complex are unclear. Here we show that proteins with locally soft regions in the vicinity of the nuclear-localization sequence exhibit higher nuclear-import rates, and that such mechanoselectivity is specifically impaired upon knocking down nucleoporin 153, a key protein in the nuclear pore complex. This allows us to design a short, easy-to-express and chemically inert unstructured peptide tag that accelerates the nuclear-import rate of stiff protein cargos. We also show that U2OS osteosarcoma cells expressing the peptide-tagged myocardin-related transcription factor import this mechanosensitive protein to the nucleus at higher rates and display faster motility. Locally unstructured regions lower the free-energy barrier of protein translocation and might offer a control mechanism for nuclear mechanotransduction.

The actin-binding protein CAP1 represses MRTF-SRF-dependent gene expression in mouse cerebral cortex

Serum response factor (SRF) is an essential transcription factor for brain development and function. Here, we explored how an SRF cofactor, the actin monomer-sensing myocardin-related transcription factor MRTF, is regulated in mouse cortical neurons. We found that MRTF-dependent SRF activity in vitro and in vivo was repressed by cyclase-associated protein CAP1. Inactivation of the actin-binding protein CAP1 reduced the amount of actin monomers in the cytoplasm, which promoted nuclear MRTF translocation and MRTF-SRF activation. This function was independent of cofilin1 and actin-depolymerizing factor, and CAP1 loss of function in cortical neurons was not compensated by endogenous CAP2. Transcriptomic and proteomic analyses of cerebral cortex lysates from wild-type and Cap1 knockout mice supported the role of CAP1 in repressing MRTF-SRF-dependent signaling in vivo. Bioinformatic analysis identified likely MRTF-SRF target genes, which aligned with the transcriptomic and proteomic results. Together with our previous studies that implicated CAP1 in axonal growth cone function as well as the morphology and plasticity of excitatory synapses, our findings establish CAP1 as a crucial actin regulator in the brain relevant for formation of neuronal networks.

IQGAP1 and NWASP promote human cancer cell dissemination and metastasis by regulating β1-integrin via FAK and MRTF/SRF

Attachment of circulating tumor cells to the endothelial cells (ECs) lining blood vessels is a critical step in cancer metastatic colonization, which leads to metastatic outgrowth. Breast and prostate cancers are common malignancies in women and men, respectively. Here, we observe that β1-integrin is required for human prostate and breast cancer cell adhesion to ECs under shear-stress conditions in vitro and to lung blood vessel ECs in vivo. We identify IQGAP1 and neural Wiskott-Aldrich syndrome protein (NWASP) as regulators of β1-integrin transcription and protein expression in prostate and breast cancer cells. IQGAP1 and NWASP depletion in cancer cells decreases adhesion to ECs in vitro and retention in the lung vasculature and metastatic lung nodule formation in vivo. Mechanistically, NWASP and IQGAP1 act downstream of Cdc42 to increase β1-integrin expression both via extracellular signal-regulated kinase (ERK)/focal adhesion kinase signaling at the protein level and by myocardin-related transcription factor/serum response factor (SRF) transcriptionally. Our results identify IQGAP1 and NWASP as potential therapeutic targets to reduce early metastatic dissemination.

SRRM2 splicing factor modulates cell fate in early development

Embryo development is an orchestrated process that relies on tight regulation of gene expression to guide cell differentiation and fate decisions. The Srrm2 splicing factor has recently been implicated in developmental disorders and diseases, but its role in early mammalian development remains unexplored. Here, we show that Srrm2 dosage is critical for maintaining embryonic stem cell pluripotency and cell identity. Srrm2 heterozygosity promotes loss of stemness, characterised by the coexistence of cells expressing naive and formative pluripotency markers, together with extensive changes in gene expression, including genes regulated by serum-response transcription factor (SRF) and differentiation-related genes. Depletion of Srrm2 by RNA interference in embryonic stem cells shows that the earliest effects of Srrm2 heterozygosity are specific alternative splicing events on a small number of genes, followed by expression changes in metabolism and differentiation-related genes. Our findings unveil molecular and cellular roles of Srrm2 in stemness and lineage commitment, shedding light on the roles of splicing regulators in early embryogenesis, developmental diseases and tumorigenesis.

Characterization of peptide-fused protein assemblies in living cells

Assembly of de novo peptides designed from scratch is in a semi-rational manner and creates artificial supramolecular structures with unique properties. Considering that the functions of various proteins in living cells are highly regulated by their assemblies, building artificial assemblies within cells holds the potential to simulate the functions of natural protein assemblies and engineer cellular activities for controlled manipulation. How can we evaluate the self-assembly of designed peptides in cells? The most effective approach involves the genetic fusion of fluorescent proteins (FPs). Expressing a self-assembling peptide fused with an FP within cells allows for evaluating assemblies through fluorescence signal. When µm-scale assemblies such as condensates are formed, the peptide assemblies can be directly observed by imaging. For sub-µm-scale assemblies, fluorescence correlation spectroscopy analysis is more practical. Additionally, the fluorescence resonance energy transfer (FRET) signal between FPs is valuable evidence of proximity. The decrease in fluorescence anisotropy associated with homo-FRET reveals the properties of self-assembly. Furthermore, by combining two FPs, one acting as a donor and the other as an acceptor, the heteromeric interaction between two different components can be studied through the FRET signal. In this chapter, we provide detailed protocols, from designing and constructing plasmid DNA expressing the peptide-fused protein to analysis of self-assembly in living cells.

ROCK and the actomyosin network control biomineral growth and morphology during sea urchin skeletogenesis

Biomineralization had apparently evolved independently in different phyla, using distinct minerals, organic scaffolds, and gene regulatory networks (GRNs). However, diverse eukaryotes from unicellular organisms, through echinoderms to vertebrates, use the actomyosin network during biomineralization. Specifically, the actomyosin remodeling protein, Rho-associated coiled-coil kinase (ROCK) regulates cell differentiation and gene expression in vertebrates' biomineralizing cells, yet, little is known on ROCK's role in invertebrates' biomineralization. Here, we reveal that ROCK controls the formation, growth, and morphology of the calcite spicules in the sea urchin larva. ROCK expression is elevated in the sea urchin skeletogenic cells downstream of the Vascular Endothelial Growth Factor (VEGF) signaling. ROCK inhibition leads to skeletal loss and disrupts skeletogenic gene expression. ROCK inhibition after spicule formation reduces the spicule elongation rate and induces ectopic spicule branching. Similar skeletogenic phenotypes are observed when ROCK is inhibited in a skeletogenic cell culture, indicating that these phenotypes are due to ROCK activity specifically in the skeletogenic cells. Reduced skeletal growth and enhanced branching are also observed under direct perturbations of the actomyosin network. We propose that ROCK and the actomyosin machinery were employed independently, downstream of distinct GRNs, to regulate biomineral growth and morphology in Eukaryotes.

The structure and function of lamin A/C: Special focus on cardiomyopathy and therapeutic interventions

Lamins are inner nuclear membrane proteins that belong to the intermediate filament family. Lamin A/C lie adjacent to the heterochromatin structure in polymer form, providing skeletal to the nucleus. Based on the localization, lamin A/C provides nuclear stability and cytoskeleton to the nucleus and modulates chromatin organization and gene expression. Besides being the structural protein making the inner nuclear membrane in polymer form, lamin A/C functions as a signalling molecule involved in gene expression as an enhancer inside the nucleus. Lamin A/C regulates various cellular pathways like autophagy and energy balance in the cytoplasm. Its expression is highly variable in differentiated tissues, higher in hard tissues like bone and muscle cells, and lower in soft tissues like the liver and brain. In muscle cells, including the heart, lamin A/C must be expressed in a balanced state. Lamin A/C mutation is linked with various diseases, such as muscular dystrophy, lipodystrophy, and cardiomyopathies. It has been observed that a good number of mutations in the LMNA gene impact cardiac activity and its function. Although several works have been published, there are still several unexplored areas left regarding the lamin A/C function and structure in the cardiovascular system and its pathological state. In this review, we focus on the structural organization, expression pattern, and function of lamin A/C, its interacting partners, and the pathophysiology associated with mutations in the lamin A/C gene, with special emphasis on cardiovascular diseases. With the recent finding on lamin A/C, we have summarized the possible therapeutic interventions to treat cardiovascular symptoms and reverse the molecular changes.

Mechanosensing regulates tissue repair program in macrophages

Tissue-resident macrophages play important roles in tissue homeostasis and repair. However, how macrophages monitor and maintain tissue integrity is not well understood. The extracellular matrix (ECM) is a key structural and organizational component of all tissues. Here, we find that macrophages sense the mechanical properties of the ECM to regulate a specific tissue repair program. We show that macrophage mechanosensing is mediated by cytoskeletal remodeling and can be performed in three-dimensional environments through a noncanonical, integrin-independent mechanism analogous to amoeboid migration. We find that these cytoskeletal dynamics also integrate biochemical signaling by colony-stimulating factor 1 and ultimately regulate chromatin accessibility to control the mechanosensitive gene expression program. This study identifies an "amoeboid" mode of ECM mechanosensing through which macrophages may regulate tissue repair and fibrosis.

Matrix Nonlinear Viscoelasticity Regulates Skeletal Myogenesis through MRTF Nuclear Localization and Nuclear Mechanotransduction

Mechanically sensitive tissues (e.g., skeletal muscles) greatly need mechanical stimuli during the development and maturation. The extracellular matrix (ECM) mediates these signals through nonlinear viscoelasticity of collagen networks that are predominant components of the ECM. However, the interactions between cells and ECM form a feedback loop, and it has not yet been possible to determine the degree to which, if any, of the features of matrix nonlinear viscoelasticity affect skeletal muscle development and regeneration. In this study, a nonlinear viscoelastic feature (i.e., strain-enhanced stress relaxation (SESR)) in normal skeletal muscles is observed, which however is almost absent in diseased muscles from Duchenne muscular dystrophy mice. It is recapitulated such SESR feature in vitro and separated the effects of mechanical strain and ECM viscoelasticity on myoblast response by developing a collagen-based hydrogel platform. Both strain and stress relaxation induce myogenic differentiation and myotube formation by C2C12 myoblasts, and myogenesis is more promoted by applying SESR. This promotion can be explained by the effects of SESR on actin polymerization-mediated myocardin related transcription factor (MRTF) nuclear localization and nuclear mechanotransduction. This study represents the first attempt to investigate the SESR phenomenon in skeletal muscles and reveal underlying mechanobiology, which will provide new opportunities for the tissue injury treatments.

The potential of graphene coatings as neural interfaces

Recent advances in nanotechnology design and fabrication have shaped the landscape for the development of ideal cell interfaces based on biomaterials. A holistic evaluation of the requirements for a cell interface is a highly complex task. Biocompatibility is a crucial requirement which is affected by the interface's properties, including elemental composition, morphology, and surface chemistry. This review explores the current state-of-the-art on graphene coatings produced by chemical vapor deposition (CVD) and applied as neural interfaces, detailing the key properties required to design an interface capable of physiologically interacting with neural cells. The interfaces are classified into substrates and scaffolds to differentiate the planar and three-dimensional environments where the cells can adhere and proliferate. The role of specific features such as mechanical properties, porosity and wettability are investigated. We further report on the specific brain-interface applications where CVD graphene paved the way to revolutionary advances in biomedicine. Future studies on the long-term effects of graphene-based materials in vivo will unlock even more potentially disruptive neuro-applications.

Single molecule imaging of the central dogma reveals myosin-2A gene expression is regulated by contextual translational buffering

While protein homeostasis is a hallmark of gene regulation, unraveling the hidden regulatory mechanisms that maintain homeostasis is difficult using traditional methods. To confront this problem, we CRISPR engineered a human cell line with multiple tags in the endogenous MYH9 gene, which encodes the essential and ubiquitous myosin-2A cytoskeletal motor. Using these cells, we imaged MYH9 transcription, translation, and mature mRNA and protein in distinct colors, enabling a full dissection of the central dogma. Our data show that MYH9 transcription is upregulated in an SRF-dependent manner in response to cytoskeletal cues and that MYH9 translation can either buffer or match the transcriptional response depending on context. Upon knockdown of actin-depolymerizing proteins like cofilin, translation efficiency drops by a factor of two to buffer strong transcriptional upregulation, likely to help prevent excessive myosin activity. In contrast, following serum stimulation, translation matches the transcriptional response to readily reestablish steady state. Our results identify contextual translational buffering as an important regulatory mechanism driving stable MYH9 expression. They also demonstrate the power and broad applicability of our cell line, which can now be used to accurately quantify central dogma dynamics in response to diverse forms of cellular perturbations.

Myeloid-derived growth factor suppresses VSMC dedifferentiation and attenuates postinjury neointimal formation in rats by activating S1PR2 and its downstream signaling

Restenosis after angioplasty is caused usually by neointima formation characterized by aberrant vascular smooth muscle cell (VSMC) dedifferentiation. Myeloid-derived growth factor (MYDGF), secreted from bone marrow-derived monocytes and macrophages, has been found to have cardioprotective effects. In this study we investigated the effect of MYDGF to postinjury neointimal formation and the underlying mechanisms. Rat carotid arteries balloon-injured model was established. We found that plasma MYDGF content and the level of MYDGF in injured arteries were significantly decreased after balloon injury. Local application of exogenous MYDGF (50 μg/mL) around the injured vessel during balloon injury markedly ameliorated the development of neointimal formation evidenced by relieving the narrow endovascular diameter, improving hemodynamics, and reducing collagen deposition. In addition, local application of MYDGF inhibited VSMC dedifferentiation, which was proved by reversing the elevated levels of osteopontin (OPN) protein and decreased levels of α-smooth muscle actin (α-SMA) in the left carotid arteries. We showed that PDGF-BB (30 ng/mL) stimulated VSMC proliferation, migration and dedifferentiation in vitro; pretreatment with MYDGF (50-200 ng/mL) concentration-dependently eliminated PDGF-BB-induced cell proliferation, migration and dedifferentiation. Molecular docking revealed that MYDGF had the potential to bind with sphingosine-1-phosphate receptor 2 (S1PR2), which was confirmed by SPR assay and Co-IP analysis. Pretreatment with CCG-1423 (Rho signaling inhibitor), JTE-013 (S1PR2 antagonist) or Ripasudil (ROCK inhibitor) circumvented the inhibitory effects of MYDGF on VSMC phenotypic switching through inhibiting S1PR2 or its downstream RhoA-actin monomers (G-actin) /actin filaments (F-actin)-MRTF-A signaling. In summary, this study proves that MYDGF relieves neointimal formation of carotid arteries in response to balloon injury in rats, and suppresses VSMC dedifferentiation induced by PDGF-BB via S1PR2-RhoA-G/F-actin-MRTF-A signaling pathway. In addition, our results provide evidence for cross talk between bone marrow and vasculature.

Phosphatidic acid-enabled MKL1 contributes to liver regeneration: Translational implication in liver failure

Liver regeneration following injury aids the restoration of liver mass and the recovery of liver function. In the present study we investigated the contribution of megakaryocytic leukemia 1 (MKL1), a transcriptional modulator, to liver regeneration. We report that both MKL1 expression and its nuclear translocation correlated with hepatocyte proliferation in cell and animal models of liver regeneration and in liver failure patients. Mice with MKL1 deletion exhibited defective regenerative response in the liver. Transcriptomic analysis revealed that MKL1 interacted with E2F1 to program pro-regenerative transcription. MAPKAPK2 mediated phosphorylation primed MKL1 for its interaction with E2F1. Of interest, phospholipase d2 promoted MKL1 nuclear accumulation and liver regeneration by catalyzing production of phosphatidic acid (PA). PA administration stimulated hepatocyte proliferation and enhanced survival in a MKL1-dependent manner in a pre-clinical model of liver failure. Finally, PA levels was detected to be positively correlated with expression of pro-regenerative genes and inversely correlated with liver injury in liver failure patients. In conclusion, our data reveal a novel mechanism whereby MKL1 contributes to liver regeneration. Screening for small-molecule compounds boosting MKL1 activity may be considered as a reasonable approach to treat acute liver failure.

LncRNA NONHSAT227443.1 Confers Esophageal Squamous Cell Carcinoma Chemotherapy Resistance by Activating PI3K/AKT Signaling via Targeting MRTFB

INTRODUCTION

Esophageal cancer presents significant challenges due to limited treatment options and poor prognosis, particularly in advanced stages. Dysregulated long non-coding RNAs (lncRNAs) are implicated in cancer progression and treatment resistance. This study investigated the roles of dysregulated lncRNA NONHSAT227443.1, identified through lncRNA-seq, and its downstream target gene MRTFB in esophageal squamous cell carcinoma (ESCC).

METHODS

Dysregulated lncRNAs were identified through lncRNA-seq in esophageal cancer tissues with varying chemotherapy response. The regulatory interaction of overexpressed NONHSAT227443.1 was assessed using quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting. Functional assays, including cell viability, cell proliferation, and flow cytometry analyses, were performed to comprehensively investigate the influence of NONHSAT227443.1 and its downstream molecules on ESCC.

RESULTS

NONHSAT227443.1 was significantly overexpressed in paclitaxel plus platinum chemotherapy non-responders and esophageal cancer cell lines. Chemotherapy exposure led to diminished NONHSAT227443.1 expression. NONHSAT227443.1 negatively regulated MRTFB expression, and their combined dysregulation correlated with increased cancer activity, proliferation, and suppressed apoptosis. Diminished MRTFB expression was associated with PI3K/AKT pathway activation.

CONCLUSION

Our study provides insights into NONHSAT227443.1 and MRTFB roles in esophageal cancer, contributing to aggressive traits and treatment resistance. NONHSAT227443.1 and MRTFB may serve as potential therapeutic targets to enhance the response to paclitaxel plus platinum chemotherapy in non-responsive cases.

WAVE2 Is a Vital Regulator in Myogenic Differentiation of Progenitor Cells through the Mechanosensitive MRTFA-SRF Axis

Skeletal myogenesis is an intricate process involving the differentiation of progenitor cells into myofibers, which is regulated by actin cytoskeletal dynamics and myogenic transcription factors. Although recent studies have demonstrated the pivotal roles of actin-binding proteins (ABPs) as mechanosensors and signal transducers, the biological significance of WAVE2 (Wiskott-Aldrich syndrome protein family member 2), an ABP essential for actin polymerization, in myogenic differentiation of progenitor cells has not been investigated. Our study provides important insights into the regulatory roles played by WAVE2 in the myocardin-related transcription factor A (MRTFA)-serum response factor (SRF) signaling axis and differentiation of myoblasts. We demonstrate that WAVE2 expression is induced during myogenic differentiation and plays a pivotal role in actin cytoskeletal remodeling in C2C12 myoblasts. Knockdown of WAVE2 in C2C12 cells reduced filamentous actin levels, increased globular actin accumulation, and impaired the nuclear translocation of MRTFA. Furthermore, WAVE2 depletion in myoblasts inhibited the expression and transcriptional activity of SRF and suppressed cell proliferation in myoblasts. Consequently, WAVE2 knockdown suppressed myogenic regulatory factors (i.e., MyoD, MyoG, and SMYD1) expressions, thereby hindering the differentiation of myoblasts. Thus, this study suggests that WAVE2 is essential for myogenic differentiation of progenitor cells by modulating the mechanosensitive MRTFA-SRF axis.

Transcription factors in fibroblast plasticity and CAF heterogeneity

In recent years, research focused on the multifaceted landscape and functions of cancer-associated fibroblasts (CAFs) aimed to reveal their heterogeneity and identify commonalities across diverse tumors for more effective therapeutic targeting of pro-tumoral stromal microenvironment. However, a unified functional categorization of CAF subsets remains elusive, posing challenges for the development of targeted CAF therapies in clinical settings.The CAF phenotype arises from a complex interplay of signals within the tumor microenvironment, where transcription factors serve as central mediators of various cellular pathways. Recent advances in single-cell RNA sequencing technology have emphasized the role of transcription factors in the conversion of normal fibroblasts to distinct CAF subtypes across various cancer types.This review provides a comprehensive overview of the specific roles of transcription factor networks in shaping CAF heterogeneity, plasticity, and functionality. Beginning with their influence on fibroblast homeostasis and reprogramming during wound healing and fibrosis, it delves into the emerging insights into transcription factor regulatory networks. Understanding these mechanisms not only enables a more precise characterization of CAF subsets but also sheds light on the early regulatory processes governing CAF heterogeneity and functionality. Ultimately, this knowledge may unveil novel therapeutic targets for cancer treatment, addressing the existing challenges of stromal-targeted therapies.

RGMa collapses the neuronal actin barrier against disease-implicated protein and exacerbates ALS

Repulsive guidance molecule A (RGMa) was originally identified as a neuronal growth cone-collapsing factor. Previous reports have demonstrated the multifunctional roles of RGMa mediated by neogenin1. However, the pathogenic involvement of RGMa in amyotrophic lateral sclerosis (ALS) remains unclear. Here, we demonstrated that RGMa concentration was elevated in the cerebrospinal fluid of both patients with ALS and transgenic mice overexpressing the mutant human superoxide dismutase1 (mSOD1 mice). Treatment with humanized anti-RGMa monoclonal antibody ameliorated the clinical symptoms in mSOD1 mice. Histochemical analysis revealed that the anti-RGMa antibody significantly decreased mutant SOD1 protein accumulation in the motor neurons of mSOD1 mice via inhibition of actin depolymerization. In vitro analysis revealed that the anti-RGMa antibody inhibited the cellular uptake of the mutant SOD1 protein, presumably by reinforcing the neuronal actin barrier. Collectively, these data suggest that RGMa leads to the collapse of the neuronal actin barrier and promotes aberrant protein deposition, resulting in exacerbation of the ALS pathology.

Differential regulation of hair cell actin cytoskeleton mediated by SRF and MRTFB

The MRTF-SRF pathway has been extensively studied for its crucial role in driving the expression of a large number of genes involved in actin cytoskeleton of various cell types. However, the specific contribution of MRTF-SRF in hair cells remains unknown. In this study, we showed that hair cell-specific deletion of Srf or Mrtfb, but not Mrtfa, leads to similar defects in the development of stereocilia dimensions and the maintenance of cuticular plate integrity. We used fluorescence-activated cell sorting-based hair cell RNA-Seq analysis to investigate the mechanistic underpinnings of the changes observed in Srf and Mrtfb mutants, respectively. Interestingly, the transcriptome analysis revealed distinct profiles of genes regulated by Srf and Mrtfb, suggesting different transcriptional regulation mechanisms of actin cytoskeleton activities mediated by Srf and Mrtfb. Exogenous delivery of calponin 2 using Adeno-associated virus transduction in Srf mutants partially rescued the impairments of stereocilia dimensions and the F-actin intensity of cuticular plate, suggesting the involvement of Cnn2, as an Srf downstream target, in regulating the hair bundle morphology and cuticular plate actin cytoskeleton organization. Our study uncovers, for the first time, the unexpected differential transcriptional regulation of actin cytoskeleton mediated by Srf and Mrtfb in hair cells, and also demonstrates the critical role of SRF-CNN2 in modulating actin dynamics of the stereocilia and cuticular plate, providing new insights into the molecular mechanism underlying hair cell development and maintenance.

Ephexin3/ARHGEF5 Together with Cell Migration Signaling Partners within the Tumor Microenvironment Define Prognostic Transcriptional Signatures in Multiple Cancer Types

Cancer cell migration involves a repertoire of signaling proteins that lead cytoskeleton reorganization as a critical step in metastatic dissemination. RhoGEFs are multidomain effectors that integrate signaling inputs to activate the molecular switches that orchestrate actin cytoskeleton reorganization. Ephexins, a group of five RhoGEFs, play oncogenic roles in invasive and metastatic cancer, leading to a mechanistic hypothesis about their function as signaling nodes assembling functional complexes that guide cancer cell migration. To identify clinically significant Ephexin signaling partners, we applied three systematic data mining strategies, based on the screening of essential Ephexins in multiple cancer cell lines and the identification of coexpressed signaling partners in the TCGA cancer patient datasets. Based on the domain architecture of encoded proteins and gene ontology criteria, we selected Ephexin signaling partners with a role in cytoskeletal reorganization and cell migration. We focused on Ephexin3/ARHGEF5, identified as an essential gene in multiple cancer cell types. Based on significant coexpression data and coessentiality, the signaling repertoire that accompanies Ephexin3 corresponded to three groups: pan-cancer, cancer-specific and coessential. To further select the Ephexin3 signaling partners likely to be relevant in clinical settings, we first identified those whose high expression was statistical linked to shorter patient survival. The resulting Ephexin3 transcriptional signatures represent significant accumulated risk, predictive of shorter survival, in 17 cancer types, including PAAD, LUAD, LGG, OSC, AML, KIRC, THYM, BLCA, LIHC and UCEC. The signaling landscape that accompanies Ephexin3 in various cancer types included the tyrosine kinase receptor MET and the tyrosine phosphatase receptor PTPRF, the serine/threonine kinases MARK2 and PAK6, the Rho GTPases RHOD, RHOF and RAC1, and the cytoskeletal regulator DIAHP1. Our findings set the basis to further explore the role of Ephexin3/ARHGEF5 as an essential effector and signaling hub in cancer cell migration.

Heterogeneous anomalous transport in cellular and molecular biology

It is well established that a wide variety of phenomena in cellular and molecular biology involve anomalous transport e.g. the statistics for the motility of cells and molecules are fractional and do not conform to the archetypes of simple diffusion or ballistic transport. Recent research demonstrates that anomalous transport is in many cases heterogeneous in both time and space. Thus single anomalous exponents and single generalised diffusion coefficients are unable to satisfactorily describe many crucial phenomena in cellular and molecular biology. We consider advances in the field ofheterogeneous anomalous transport(HAT) highlighting: experimental techniques (single molecule methods, microscopy, image analysis, fluorescence correlation spectroscopy, inelastic neutron scattering, and nuclear magnetic resonance), theoretical tools for data analysis (robust statistical methods such as first passage probabilities, survival analysis, different varieties of mean square displacements, etc), analytic theory and generative theoretical models based on simulations. Special emphasis is made on high throughput analysis techniques based on machine learning and neural networks. Furthermore, we consider anomalous transport in the context of microrheology and the heterogeneous viscoelasticity of complex fluids. HAT in the wavefronts of reaction-diffusion systems is also considered since it plays an important role in morphogenesis and signalling. In addition, we present specific examples from cellular biology including embryonic cells, leucocytes, cancer cells, bacterial cells, bacterial biofilms, and eukaryotic microorganisms. Case studies from molecular biology include DNA, membranes, endosomal transport, endoplasmic reticula, mucins, globular proteins, and amyloids.

Unraveling the interplay between RAS/RAF/MEK/ERK signaling pathway and autophagy in cancer: From molecular mechanisms to targeted therapy

RAS/RAF/MEK/ERK signaling pathway is one of the most important pathways of Mitogen-activated protein kinases (MAPK), which widely participate in regulating cell proliferation, differentiation, apoptosis and signaling transduction. Autophagy is an essential mechanism that maintains cellular homeostasis by degrading aged and damaged organelles. Recently, some studies revealed RAS/RAF/MEK/ERK signaling pathway is closely related to autophagy regulation and has a dual effect in tumor cells. However, the specific mechanism by which RAS/RAF/MEK/ERK signaling pathway participates in autophagy regulation is not fully understood. This article provides a comprehensive review of the research progress with regard to the RAS/RAF/MEK/ERK signaling pathway and autophagy, as well as their interplay in cancer therapy. The impact of small molecule inhibitors that target the RAS/RAF/MEK/ERK signaling pathway on autophagy is discussed in this study. The advantages and limitations of the clinical combination of these small molecule inhibitors with autophagy inhibitors are also explored. The findings from this study may provide additional perspectives for future cancer treatment strategies.

Nuclear Import and Export of YAP and TAZ

Yes-associated Protein (YAP) and its paralog Transcriptional Coactivator with PDZ-binding Motif (TAZ) are major regulators of gene transcription/expression, primarily controlled by the Hippo pathway and the cytoskeleton. Integrating an array of chemical and mechanical signals, they impact growth, differentiation, and regeneration. Accordingly, they also play key roles in tumorigenesis and metastasis formation. Their activity is primarily regulated by their localization, that is, Hippo pathway- and/or cytoskeleton-controlled cytosolic or nuclear sequestration. While many details of such prevailing retention models have been elucidated, much less is known about their actual nuclear traffic: import and export. Although their size is not far from the cutoff for passive diffusion through the nuclear pore complex (NPC), and they do not contain any classic nuclear localization (NLS) or nuclear export signal (NES), evidence has been accumulating that their shuttling involves mediated and thus regulatable/targetable processes. The aim of this review is to summarize emerging information/concepts about their nucleocytoplasmic shuttling, encompassing the relevant structural requirements (NLS, NES), nuclear transport receptors (NTRs, karyophererins), and NPC components, along with the potential transport mechanisms and their regulation. While dissecting retention vs. transport is often challenging, the emerging picture suggests that YAP/TAZ shuttles across the NPC via multiple, non-exclusive, mediated mechanisms, constituting a novel and intriguing facet of YAP/TAZ biology.

Myocardin-related transcription factors regulate morphogenetic events in vertebrate embryos by controlling F-actin organization and apical constriction

Myocardin-related transcription factors (Mrtfa and Mrtfb), also known as megakaryoblastic leukemia proteins (Mkl1/MAL and Mkl2), associate with serum response factor (Srf) to regulate transcription in response to actin dynamics, however, the functions of Mrtfs in early vertebrate embryos remain largely unknown. Here we document the requirement of Mrtfs for blastopore closure at gastrulation and neural plate folding in Xenopus early embryos. Both stimulation and inhibition of Mrtf activity caused similar gross morphological phenotypes, yet the effects on F-actin distribution and cell behavior were different. Suppressing Mrtf-dependent transcription reduced overall F-actin levels and inhibited apical constriction during gastrulation and neurulation. By contrast, constitutively active Mrtf caused tricellular junction remodeling and induced apical constriction in superficial ectoderm. The underlying mechanism appeared distinct from the one utilized by known apical constriction inducers. We propose that the regulation of apical constriction is among the primary cellular responses to Mrtf. Our findings highlight a dedicated role of specific transcription factors, Mrtfs, in early morphogenetic processes.

MRTF-A gain-of-function in mice impairs homeostatic renewal of the intestinal epithelium

The actin-regulated transcription factor MRTF-A represents a central relay in mechanotransduction and controls a subset of SRF-dependent target genes. However, gain-of-function studies in vivo are lacking. Here we characterize a conditional MRTF-A transgenic mouse model. While MRTF-A gain-of-function impaired embryonic development, induced expression of constitutively active MRTF-A provoked rapid hepatocyte ballooning and liver failure in adult mice. Specific expression in the intestinal epithelium caused an erosive architectural distortion, villus blunting, cryptal hyperplasia and colonic inflammation, resulting in transient weight loss. Organoids from transgenic mice repeatedly induced in vitro showed impaired self-renewal and defective cryptal compartments. Mechanistically, MRTF-A gain-of-function decreased proliferation and increased apoptosis, but did not induce fibrosis. MRTF-A targets including Acta2 and Pai-1 were induced, whereas markers of stem cells and differentiated cells were reduced. Our results suggest that activated MRTF-A in the intestinal epithelium shifts the balance between proliferation, differentiation and apoptosis.

Cell contractility in early animal evolution

Tissue deformation mediated by collective cell contractility is a signature characteristic of animals. In most animals, fast and reversible contractions of muscle cells mediate behavior, while slow and irreversible contractions of epithelial or mesenchymal cells play a key role in morphogenesis. Animal tissue contractility relies on the activity of the actin/myosin II complex (together referred to as 'actomyosin'), an ancient and versatile molecular machinery that performs a broad range of functions in development and physiology. This review synthesizes emerging insights from morphological and molecular studies into the evolutionary history of animal contractile tissue. The most ancient functions of actomyosin are cell crawling and cytokinesis, which are found in a wide variety of unicellular eukaryotes and in individual metazoan cells. Another contractile functional module, apical constriction, is universal in metazoans and shared with choanoflagellates, their closest known living relatives. The evolution of animal contractile tissue involved two key innovations: firstly, the ability to coordinate and integrate actomyosin assembly across multiple cells, notably to generate supracellular cables, which ensure tissue integrity but also allow coordinated morphogenesis and movements at the organism scale; and secondly, the evolution of dedicated contractile cell types for adult movement, belonging to two broad categories respectively defined by the expression of the fast (striated-type) and slow (smooth/non-muscle-type) myosin II paralogs. Both contractile cell types ancestrally resembled generic contractile epithelial or mesenchymal cells and might have played a versatile role in both behavior and morphogenesis. Modern animal contractile cells span a continuum between unspecialized contractile epithelia (which underlie behavior in modern placozoans), epithelia with supracellular actomyosin cables (found in modern sponges), epitheliomuscular tissues (with a concentration of actomyosin cables in basal processes, for example in sea anemones), and specialized muscle tissue that has lost most or all epithelial properties (as in ctenophores, jellyfish and bilaterians). Recent studies in a broad range of metazoans have begun to reveal the molecular basis of these transitions, powered by the elaboration of the contractile apparatus and the evolution of 'core regulatory complexes' of transcription factors specifying contractile cell identity.

Age-Associated Changes in Endothelial Transcriptome and Epigenetic Landscapes Correlate With Elevated Risk of Cerebral Microbleeds

Background Stroke is a leading global cause of human death and disability, with advanced aging associated with elevated incidences of stroke. Despite high mortality and morbidity of stroke, the mechanisms leading to blood-brain barrier dysfunction and development of stroke with age are poorly understood. In the vasculature of brain, endothelial cells (ECs) constitute the core component of the blood-brain barrier and provide a physical barrier composed of tight junctions, adherens junctions, and basement membrane. Methods and Results We show, in mice, the incidents of intracerebral bleeding increases with age. After isolating an enriched population of cerebral ECs from murine brains at 2, 6, 12, 18, and 24 months, we studied age-associated changes in gene expression. The study reveals age-dependent dysregulation of 1388 genes, including many involved in the maintenance of the blood-brain barrier and vascular integrity. We also investigated age-dependent changes on the levels of CpG methylation and accessible chromatin in cerebral ECs. Our study reveals correlations between age-dependent changes in chromatin structure and gene expression, whereas the dynamics of DNA methylation changes are different. Conclusions We find significant age-dependent downregulation of the Aplnr gene along with age-dependent reduction in chromatin accessibility of promoter region of the Aplnr gene in cerebral ECs. Aplnr is associated with positive regulation of vasodilation and is implicated in vascular health. Altogether, our data suggest a potential role of the apelinergic axis involving the ligand apelin and its receptor to be critical in maintenance of the blood-brain barrier and vascular integrity.