Nesprin-2 is a novel scaffold protein for telethonin and FHL-2 in the cardiomyocyte sarcomere.

Nesprins comprise a family of multi-isomeric scaffolding proteins, forming the linker of nucleoskeleton-and-cytoskeleton complex with lamin A/C, emerin and SUN1/2 at the nuclear envelope. Mutations in nesprin-1/-2 are associated with Emery-Dreifuss muscular dystrophy (EDMD) with conduction defects and dilated cardiomyopathy (DCM). We have previously observed sarcomeric staining of nesprin-1/-2 in cardiac and skeletal muscle, but nesprin function in this compartment remains unknown. In this study, we show that specific nesprin-2 isoforms are highly expressed in cardiac muscle and localize to the Z-disc and I band of the sarcomere. Expression of GFP-tagged nesprin-2 giant spectrin repeats 52 to 53, localized to the sarcomere of neonatal rat cardiomyocytes. Yeast two-hybrid screening of a cardiac muscle cDNA library identified telethonin and four-and-half LIM domain (FHL)-2 as potential nesprin-2 binding partners. GST pull-down and immunoprecipitation confirmed the individual interactions between nesprin-2/telethonin and nesprin-2/FHL-2, and showed that nesprin-2 and telethonin binding was dependent on telethonin phosphorylation status. Importantly, the interactions between these binding partners were impaired by mutations in nesprin-2, telethonin, and FHL-2 identified in EDMD with DCM and hypertrophic cardiomyopathy patients. These data suggest that nesprin-2 is a novel sarcomeric scaffold protein that may potentially participate in the maintenance and/or regulation of sarcomeric organization and function.

Low-Protein Diets Composed of Protein Recovered from Food Processing Supported Growth, but Induced Mild Hepatic Steatosis Compared with a No-Protein Diet in Young Female Rats.

BACKGROUND: Living in low-income countries often restricts the consumption of adequate protein and animal protein. OBJECTIVES: This study aimed to investigate the effects of feeding low-protein diets on growth and liver health using proteins recovered from animal processing. METHODS: Female Sprague-Dawley rats (aged 28 d) were randomly assigned (n = 8 rats/group) to be fed standard purified diets with 0% or 10% kcal protein that was comprised of either carp, whey, or casein. RESULTS: Rats that were fed low-protein diets showed higher growth but developed mild hepatic steatosis compared to rats that were fed a no-protein diet, regardless of the protein source. Real-time quantitative polymerase chain reactions targeting the expression of genes involved in liver lipid homeostasis were not significantly different among groups. Global RNA-sequencing technology identified 9 differentially expressed genes linked to folate-mediated 1-carbon metabolism, endoplasmic reticulum (ER) stress, and metabolic diseases. Canonical pathway analysis revealed that mechanisms differed depending on the protein source. ER stress and dysregulated energy metabolism were implicated in hepatic steatosis in carp- and whey-fed rats. In contrast, impaired liver one-carbon methylations, lipoprotein assembly, and lipid export were implicated in casein-fed rats. CONCLUSIONS: Carp sarcoplasmic protein showed comparable results to commercially available casein and whey protein. A better understanding of the molecular mechanisms in hepatic steatosis development can assist formulation of proteins recovered from food processing into a sustainable source of high-quality protein.

RNA-sequencing revealed apple pomace ameliorates expression of genes in the hypothalamus associated with neurodegeneration in female rats fed a Western diet during adolescence to adulthood.

OBJECTIVES: Apple pomace, a waste byproduct of apple processing, is rich in nutrients (e.g. polyphenols and soluble fiber) with the potential to be neuroprotective. The aim of this study was to employ RNA-sequencing (RNASeq) technology to investigate diet-gene interactions in the hypothalamus of rats after feeding a Western diet calorically substituted with apple pomace. METHODS: Adolescent (age 21-29 days) female Sprague-Dawley rats were randomly assigned (n = 8 rats/group) to consume either a purified standard diet, Western (WE) diet, or Western diet calorically substituted with 10% apple pomace (WE/AP) for 8 weeks. RNA-seq was performed (n = 5 rats/group) to determine global differentially expressed genes in the hypothalamus. RESULTS: RNA-seq results comparing rats fed WE to WE/AP revealed 15 differentially expressed genes in the hypothalamus. Caloric substitution of WE diet with 10% apple pomace downregulated (q < 0.06) five genes implicated in brain aging and neurodegenerative disorders: synuclein alpha, phospholipase D family member 5, NADH dehydrogenase Fe-S protein 6, choline O-acetyltransferase, and frizzled class receptor 6. DISCUSSION: Altered gene expression of these five genes suggests that apple pomace ameliorated synthesis of the neurotransmitter, acetylcholine, in rats fed a WE diet. Apple pomace, a rich source of antioxidant polyphenols and soluble fiber, has been shown to reverse nonalcoholic fatty liver disease (NAFLD). Diet-induced NAFLD decreases hepatic de novo synthesis of choline, a precursor to acetylcholine. Based on preclinical evidence, apple pomace has the potential to be a sustainable functional food for maintaining brain function and for reducing the risk of neurodegeneration.

Novel nesprin-1 mutations associated with dilated cardiomyopathy cause nuclear envelope disruption and defects in myogenesis.

Nesprins-1 and -2 are highly expressed in skeletal and cardiac muscle and together with SUN (Sad1p/UNC84)-domain containing proteins and lamin A/C form the LInker of Nucleoskeleton-and-Cytoskeleton (LINC) bridging complex at the nuclear envelope (NE). Mutations in nesprin-1/2 have previously been found in patients with autosomal dominant Emery-Dreifuss muscular dystrophy (EDMD) as well as dilated cardiomyopathy (DCM). In this study, three novel rare variants (R8272Q, S8381C and N8406K) in the C-terminus of the SYNE1 gene (nesprin-1) were identified in seven DCM patients by mutation screening. Expression of these mutants caused nuclear morphology defects and reduced lamin A/C and SUN2 staining at the NE. GST pull-down indicated that nesprin-1/lamin/SUN interactions were disrupted. Nesprin-1 mutations were also associated with augmented activation of the ERK pathway in vitro and in hearts in vivo. During C2C12 muscle cell differentiation, nesprin-1 levels are increased concomitantly with kinesin light chain (KLC-1/2) and immunoprecipitation and GST pull-down showed that these proteins interacted via a recently identified LEWD domain in the C-terminus of nesprin-1. Expression of nesprin-1 mutants in C2C12 cells caused defects in myoblast differentiation and fusion associated with dysregulation of myogenic transcription factors and disruption of the nesprin-1 and KLC-1/2 interaction at the outer nuclear membrane. Expression of nesprin-1α2 WT and mutants in zebrafish embryos caused heart developmental defects that varied in severity. These findings support a role for nesprin-1 in myogenesis and muscle disease, and uncover a novel mechanism whereby disruption of the LINC complex may contribute to the pathogenesis of DCM.

Emerging regulators of vascular smooth muscle cell migration.

Vascular smooth muscle cells (VSMCs) are the predominant cell type in the blood vessel wall and normally adopt a quiescent, contractile phenotype. VSMC migration is tightly controlled, however, disease associated changes in the soluble and insoluble environment promote VSMC migration. Classically, studies investigating VSMC migration have described the influence of soluble factors. Emerging data has highlighted the importance of insoluble factors, including extracellular matrix stiffness and porosity. In this review, we will recap on the important signalling pathways that regulate VSMC migration and reflect on the potential importance of emerging regulators of VSMC function.

Mouse models of nesprin-related diseases.

Nesprins (nuclear envelope spectrin repeat proteins) are a family of multi-isomeric scaffolding proteins. Nesprins form the LInker of Nucleoskeleton-and-Cytoskeleton (LINC) complex with SUN (Sad1p/UNC84) domain-containing proteins at the nuclear envelope, in association with lamin A/C and emerin, linking the nucleoskeleton to the cytoskeleton. The LINC complex serves as both a physical linker between the nuclear lamina and the cytoskeleton and a mechanosensor. The LINC complex has a broad range of functions and is involved in maintaining nuclear architecture, nuclear positioning and migration, and also modulating gene expression. Over 80 disease-related variants have been identified in SYNE-1/2 (nesprin-1/2) genes, which result in muscular or central nervous system disorders including autosomal dominant Emery-Dreifuss muscular dystrophy, dilated cardiomyopathy and autosomal recessive cerebellar ataxia type 1. To date, 17 different nesprin mouse lines have been established to mimic these nesprin-related human diseases, which have provided valuable insights into the roles of nesprin and its scaffold LINC complex in a tissue-specific manner. In this review, we summarise the existing nesprin mouse models, compare their phenotypes and discuss the potential mechanisms underlying nesprin-associated diseases.

Vascular Stem/Progenitor Cell Migration Induced by Smooth Muscle Cell-Derived Chemokine (C-C Motif) Ligand 2 and Chemokine (C-X-C motif) Ligand 1 Contributes to Neointima Formation.

Recent studies have shown that Sca-1(+) (stem cell antigen-1) stem/progenitor cells within blood vessel walls may contribute to neointima formation, but the mechanism behind their recruitment has not been explored. In this work Sca-1(+) progenitor cells were cultivated from mouse vein graft tissue and found to exhibit increased migration when cocultured with smooth muscle cells (SMCs) or when treated with SMC-derived conditioned medium. This migration was associated with elevated levels of chemokines, CCL2 (chemokine (C-C motif) ligand 2) and CXCL1 (chemokine (C-X-C motif) ligand 1), and their corresponding receptors on Sca-1(+) progenitors, CCR2 (chemokine (C-C motif) receptor 2) and CXCR2 (chemokine (C-X-C motif) receptor 2), which were also upregulated following SMC conditioned medium treatment. Knockdown of either receptor in Sca-1(+) progenitors significantly inhibited cell migration. The GTPases Cdc42 and Rac1 were activated by both CCL2 and CXCL1 stimulation and p38 phosphorylation was increased. However, only Rac1 inhibition significantly reduced migration and p38 phosphorylation. After Sca-1(+) progenitors labeled with green fluorescent protein (GFP) were applied to the adventitial side of wire-injured mouse femoral arteries, a large proportion of GFP-Sca-1(+) -cells were observed in neointimal lesions, and a marked increase in neointimal lesion formation was seen 1 week post-operation. Interestingly, Sca-1(+) progenitor migration from the adventitia to the neointima was abrogated and neointima formation diminished in a wire injury model using CCL2(-/-) mice. These findings suggest vascular stem/progenitor cell migration from the adventitia to the neointima can be induced by SMC release of chemokines which act via CCR2/Rac1/p38 and CXCR2/Rac1/p38 signaling pathways. Stem Cells 2016;34:2368-2380.

Hyaluronan Is Crucial for Stem Cell Differentiation into Smooth Muscle Lineage.

Deciphering the extracellular signals that regulate SMC differentiation from stem cells is vital to further our understanding of the pathogenesis of vascular disease and for development of cell-based therapies and tissue engineering. Hyaluronan (HA) has emerged as an important component of the stem cell niche, however its role during stem cell differentiation is a complicated and inadequately defined process. This study aimed to investigate the role of HA in embryonic stem cell (ESC) differentiation toward a SMC lineage. ESCs were seeded on collagen-IV in differentiation medium to generate ESC-derived SMCs (esSMCs). Differentiation coincided with increased HA synthase (HAS) 2 expression, accumulation of extracellular HA and its assembly into pericellular matrices. Inhibition of HA synthesis by 4-methylumbelliferone (4MU), removal of the HA coat by hyaluronidase (HYAL) or HAS2 knockdown led to abrogation of SMC gene expression. HA activates ERK1/2 and suppresses EGFR signaling pathways via its principle receptor, CD44. EGFR inactivation coincided with increased binding to CD44, which was further augmented by addition of high molecular weight (HMW)-HA either exogenously or via HAS2 overexpression through adenoviral gene transfer. HMW-HA-stimulated esSMCs displayed a functional role in vascular tissue engineering ex vivo, vasculogenesis in a matrigel plug model and SMC accumulation in neointimal lesions of vein grafts in mice. These findings demonstrate that HAS2-induced HA synthesis and organization drives ESC-SMC differentiation. Thus, remodeling of the HA microenvironment is a critical step in directing stem cell differentiation toward a vascular lineage, highlighting HA as a potential target for treatment of vascular diseases. Stem Cells 2016;34:1225-1238.

N-terminal nesprin-2 variants regulate ß-catenin signalling.

The spatial compartmentalisation of biochemical signalling pathways is essential for cell function. Nesprins are a multi-isomeric family of proteins that have emerged as signalling scaffolds, herein, we investigate the localisation and function of novel nesprin-2 N-terminal variants. We show that these nesprin-2 variants display cell specific distribution and reside in both the cytoplasm and nucleus. Immunofluorescence microscopy revealed that nesprin-2 N-terminal variants colocalised with ß-catenin at cell-cell junctions in U2OS cells. Calcium switch assays demonstrated that nesprin-2 and ß-catenin are lost from cell-cell junctions in low calcium conditions whereas emerin localisation at the NE remained unaltered, furthermore, an N-terminal fragment of nesprin-2 was sufficient for cell-cell junction localisation and interacted with ß-catenin. Disruption of these N-terminal nesprin-2 variants, using siRNA depletion resulted in loss of ß-catenin from cell-cell junctions, nuclear accumulation of active ß-catenin and augmented ß-catenin transcriptional activity. Importantly, we show that U2OS cells lack nesprin-2 giant, suggesting that the N-terminal nesprin-2 variants regulate ß-catenin signalling independently of the NE. Together, these data identify N-terminal nesprin-2 variants as novel regulators of ß-catenin signalling that tether ß-catenin to cell-cell contacts to inhibit ß-catenin transcriptional activity.

A 28-kDa splice variant of NADPH oxidase-4 is nuclear-localized and involved in redox signaling in vascular cells.

OBJECTIVE: Reactive oxygen species-generating nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase proteins (Noxs) are involved in cell differentiation, migration, and apoptosis. Nox4 is unique among Noxs in being constitutively active, and its subcellular localization may therefore be particularly important. In this study, we identified and characterized a novel nuclear-localized 28-kDa splice variant of Nox4 in vascular cells. APPROACH AND RESULTS: Nox4 immunoreactivity was noted in the nucleus and nucleolus of vascular smooth muscle cells and multiple other cell types by confocal microscopy. Cell fractionation, sequence analyses, and siRNA studies indicated that the nuclear-localized Nox4 is a 28-kDa splice variant, Nox4D, which lacks putative transmembrane domains. Nox4D overexpression resulted in significant NADPH-dependent reactive oxygen species production as detected by several different methods and caused increased phosphorylation of extracellular-signal-regulated kinase1/2 and the nuclear transcription factor Elk-1. Overexpression of Nox4D could also induce DNA damage as assessed by γ-H2AX phosphorylation. These effects were inhibited by a single amino acid substitution in the Nox4D NADPH-binding region. CONCLUSIONS: Nox4D is a nuclear-localized and functionally active splice variant of Nox4 that may have important pathophysiologic effects through modulation of nuclear signaling and DNA damage.

The WD Domain of Atg16l1 Crucial for LC3-Associated Phagocytosis Is Not Required for Preserving Skin Barrier Function in Mice.

The skin is a multifunctional organ, forming a barrier between the external and internal environment, thereby functioning as a safeguard against extrinsic factors. Autophagy has been implicated in epidermal differentiation and in preserving skin homeostasis. LC3-associated phagocytosis (LAP) uses some but not all components of autophagy. The Atg16l1 (Δ WD) mouse model lacks the WD40 domain required for LAP and has been widely used to study the effects of LAP deficiency and autophagy on tissue homeostasis and response to infection. In this study, the Δ WD model was used to study the relationship between LAP and skin homeostasis by determining whether LAP-deficient mice display a cutaneous phenotype. Skin histology of wild-type and Δ WD mice aged 1 year revealed minor morphological differences in the tail skin dermal layer. RT-qPCR and western blot analysis showed no differences in key keratin expression between genotypes. Skin barrier formation, assessed by dye permeation assays, demonstrated full and proper formation of the skin barrier at embryonic day 18.5 in both genotypes. Biomechanical analysis of the skin showed decreased skin elasticity in aged Δ WD but not wild-type mice. In summary, the LAP-deficient Δ WD mice displayed subtle alterations in dermal histology and age-related biomechanical changes.

HGF/c-Met/ß1-integrin signalling axis induces tunneling nanotubes in A549 lung adenocarcinoma cells.

Tunneling nanotubes (TNTs) are thin cytoplasmic extensions involved in long-distance intercellular communication and can transport intracellular organelles and signalling molecules. In cancer cells, TNT formation contributes to cell survival, chemoresistance, and malignancy. However, the molecular mechanisms underlying TNT formation are not well defined, especially in different cancers. TNTs are present in non-small cell lung cancer (NSCLC) patients with adenocarcinoma. In NSCLC, hepatocyte growth factor (HGF) and its receptor, c-Met, are mutationally upregulated, causing increased cancer cell growth, survival, and invasion. This study identifies c-Met, ß1-integrin, and paxillin as novel components of TNTs in A549 lung adenocarcinoma cells, with paxillin localised at the protrusion site of TNTs. The HGF-induced TNTs in our study demonstrate the ability to transport lipid vesicles and mitochondria. HGF-induced TNT formation is mediated by c-Met and ß1-integrin in conjunction with paxillin, followed by downstream activation of MAPK and PI3K pathways and the Arp2/3 complex. These findings demonstrate a potential novel approach to inhibit TNT formation through targeting HGF/c-Met receptor and ß1-integrin signalling interactions, which has implications for multi-drug targeting in NSCLC.

Piezo1-mediated regulation of smooth muscle cell volume in response to enhanced extracellular matrix rigidity.

BACKGROUND AND PURPOSE: Decreased aortic compliance is a precursor to numerous cardiovascular diseases. Compliance is regulated by the rigidity of the aortic wall and the vascular smooth muscle cells (VSMCs). Extracellular matrix stiffening, observed during ageing, reduces compliance. In response to increased rigidity, VSMCs generate enhanced contractile forces that result in VSMC stiffening and a further reduction in compliance. Mechanisms driving VSMC response to matrix rigidity remain poorly defined. EXPERIMENTAL APPROACH: Human aortic-VSMCs were seeded onto polyacrylamide hydrogels whose rigidity mimicked either healthy (12 kPa) or aged/diseased (72 kPa) aortae. VSMCs were treated with pharmacological agents prior to agonist stimulation to identify regulators of VSMC volume regulation. KEY RESULTS: On pliable matrices, VSMCs contracted and decreased in cell area. Meanwhile, on rigid matrices VSMCs displayed a hypertrophic-like response, increasing in area and volume. Piezo1 activation stimulated increased VSMC volume by promoting calcium ion influx and subsequent activation of PKC and aquaporin-1. Pharmacological blockade of this pathway prevented the enhanced VSMC volume response on rigid matrices whilst maintaining contractility on pliable matrices. Importantly, both piezo1 and aquaporin-1 gene expression were up-regulated during VSMC phenotypic modulation in atherosclerosis and after carotid ligation. CONCLUSIONS AND IMPLICATIONS: In response to extracellular matrix rigidity, VSMC volume is increased by a piezo1/PKC/aquaporin-1 mediated pathway. Pharmacological targeting of this pathway specifically blocks the matrix rigidity enhanced VSMC volume response, leaving VSMC contractility on healthy mimicking matrices intact. Importantly, upregulation of both piezo1 and aquaporin-1 gene expression is observed in disease relevant VSMC phenotypes.

Extracellular vesicles stimulate smooth muscle cell migration by presenting collagen VI.

The extracellular matrix (ECM) supports blood vessel architecture and functionality and undergoes active remodelling during vascular repair and atherogenesis. Vascular smooth muscle cells (VSMCs) are essential for vessel repair and, via their secretome, are able to invade from the vessel media into the intima to mediate ECM remodelling. Accumulation of fibronectin (FN) is a hallmark of early vascular repair and atherosclerosis and here we show that FN stimulates VSMCs to secrete small extracellular vesicles (sEVs) by activating the ß1 integrin/FAK/Src pathway as well as Arp2/3-dependent branching of the actin cytoskeleton. Spatially, sEV were secreted via filopodia-like cellular protrusions at the leading edge of migrating cells. We found that sEVs are trapped by the ECM in vitro and colocalise with FN in symptomatic atherosclerotic plaques in vivo. Functionally, ECM-trapped sEVs induced the formation of focal adhesions (FA) with enhanced pulling forces at the cellular periphery. Proteomic and GO pathway analysis revealed that VSMC-derived sEVs display a cell adhesion signature and are specifically enriched with collagen VI. In vitro assays identified collagen VI as playing the key role in cell adhesion and invasion. Taken together our data suggests that the accumulation of FN is a key early event in vessel repair acting to promote secretion of collage VI enriched sEVs by VSMCs. These sEVs stimulate migration and invasion by triggering peripheral focal adhesion formation and actomyosin contraction to exert sufficient traction forces to enable VSMC movement within the complex vascular ECM network.

Using Polyacrylamide Hydrogels to Model Physiological Aortic Stiffness Reveals that Microtubules Are Critical Regulators of Isolated Smooth Muscle Cell Morphology and Contractility.

Vascular smooth muscle cells (VSMCs) are the predominant cell type in the medial layer of the aortic wall and normally exist in a quiescent, contractile phenotype where actomyosin-derived contractile forces maintain vascular tone. However, VSMCs are not terminally differentiated and can dedifferentiate into a proliferative, synthetic phenotype. Actomyosin force generation is essential for the function of both phenotypes. Whilst much is already known about the mechanisms of VSMC actomyosin force generation, existing assays are either low throughput and time consuming, or qualitative and inconsistent. In this study, we use polyacrylamide hydrogels, tuned to mimic the physiological stiffness of the aortic wall, in a VSMC contractility assay. Isolated VSMC area decreases following stimulation with the contractile agonists angiotensin II or carbachol. Importantly, the angiotensin II induced reduction in cell area correlated with increased traction stress generation. Inhibition of actomyosin activity using blebbistatin or Y-27632 prevented angiotensin II mediated changes in VSMC morphology, suggesting that changes in VSMC morphology and actomyosin activity are core components of the contractile response. Furthermore, we show that microtubule stability is an essential regulator of isolated VSMC contractility. Treatment with either colchicine or paclitaxel uncoupled the morphological and/or traction stress responses of angiotensin II stimulated VSMCs. Our findings support the tensegrity model of cellular mechanics and we demonstrate that microtubules act to balance actomyosin-derived traction stress generation and regulate the morphological responses of VSMCs.

A highly photostable and versatile two-photon fluorescent probe for the detection of a wide range of intracellular nitric oxide concentrations in macrophages and endothelial cells.

Nitric oxide (NO) is involved in many biological processes affecting the cardiovascular, nervous and immune systems. Intracellular NO can be monitored using fluorescent probes in combination with fluorescence imaging techniques. Most of the currently available NO fluorescent molecular probes are excited via one-photon excitation using UV or Vis light, which results in poor penetration and high photodamage to living tissues. Here, we report a two-photon fluorescent molecular probe, DANPY-NO, able to detect NO in live cells. The probe consists of an o-phenylenediamine linked to a naphthalimide core; and operates via photoinduced electron transfer. DANPY-NO exhibits good sensitivity (LOD of 77.8 nM) and high selectivity towards NO, and is stable over a broad range of pHs. The probe targeted acidic organelles within macrophages and endothelial cells, and demonstrated enhanced photostability over a commercially available NO probe. DANPY-NO was used to selectively detect endogenous NO in RAW264.7ϒ NO- macrophages, THP-1 human leukemic cells, primary mouse (bone marrow-derived) macrophages and endothelial cells. The probe was also able to detect exogenous NO in endothelial cells and distinguish between increasing concentrations of NO. The NO detection was evidenced using confocal laser scanning and two-photon microscopies, and flow cytometry. Further evidence was obtained by recording the changes in the intracellular fluorescence emission spectrum of the probe. Importantly, the probe displayed negligible toxicity to the analysed biological samples. The excellent sensitivity, selectivity, stability and versatility of DANPY-NO confirm its potential for in vitro and in vivo imaging of NO.

Enabling genomic island prediction and comparison in multiple genomes to investigate bacterial evolution and outbreaks.

Outbreaks of virulent and/or drug-resistant bacteria have a significant impact on human health and major economic consequences. Genomic islands (GIs; defined as clusters of genes of probable horizontal origin) are of high interest because they disproportionately encode virulence factors, some antimicrobial-resistance (AMR) genes, and other adaptations of medical or environmental interest. While microbial genome sequencing has become rapid and inexpensive, current computational methods for GI analysis are not amenable for rapid, accurate, user-friendly and scalable comparative analysis of sets of related genomes. To help fill this gap, we have developed IslandCompare, an open-source computational pipeline for GI prediction and comparison across several to hundreds of bacterial genomes. A dynamic and interactive visualization strategy displays a bacterial core-genome phylogeny, with bacterial genomes linearly displayed at the phylogenetic tree leaves. Genomes are overlaid with GI predictions and AMR determinants from the Comprehensive Antibiotic Resistance Database (CARD), and regions of similarity between the genomes are also displayed. GI predictions are performed using Sigi-HMM and IslandPath-DIMOB, the two most precise GI prediction tools based on nucleotide composition biases, as well as a novel blast-based consistency step to improve cross-genome prediction consistency. GIs across genomes sharing sequence similarity are grouped into clusters, further aiding comparative analysis and visualization of acquisition and loss of mobile GIs in specific sub-clades. IslandCompare is an open-source software that is containerized for local use, plus available via a user-friendly, web-based interface to allow direct use by bioinformaticians, biologists and clinicians (at https://islandcompare.ca).

Novel nuclear nesprin-2 variants tether active extracellular signal-regulated MAPK1 and MAPK2 at promyelocytic leukemia protein nuclear bodies and act to regulate smooth muscle cell proliferation.

Nuclear and cytoplasmic scaffold proteins have been shown to be essential for temporal and spatial organization, as well as the fidelity, of MAPK signaling pathways. In this study we show that nesprin-2 is a novel extracellular signal-regulated MAPK1 and 2 (ERK1/2) scaffold protein that serves to regulate nuclear signaling by tethering these kinases at promyelocytic leukemia protein nuclear bodies (PML NBs). Using immunofluorescence microscopy, GST pull-down and immunoprecipitation, we show that nesprin-2, ERK1/2, and PML colocalize and bind to form a nuclear complex. Interference of nesprin-2 function, by either siRNA-mediated knockdown or overexpression of a dominant negative nesprin-2 fragment, augmented ERK1/2 nuclear signaling shown by increased SP1 activity and ELK1 phosphorylation. The functional outcome of nesprin-2 disruption and the resultant sustained ERK1/2 signal was increased proliferation. Importantly, these activities were not induced by previously identified nuclear envelope (NE)-targeted nesprin-2 isoforms but rather were mediated by novel nuclear isoforms that lacked the KASH domain. Taken together, this study suggests that nesprin-2 is a novel intranuclear scaffold, essential for nuclear ERK1/2 signaling fidelity and cell cycle progression.

Prelamin A acts to accelerate smooth muscle cell senescence and is a novel biomarker of human vascular aging.

BACKGROUND: Hutchinson-Gilford progeria syndrome is a rare inherited disorder of premature aging caused by mutations in LMNA or Zmpste24 that disrupt nuclear lamin A processing, leading to the accumulation of prelamin A. Patients develop severe premature arteriosclerosis characterized by vascular smooth muscle cell (VSMC) calcification and attrition. METHODS AND RESULTS: To determine whether defective lamin A processing is associated with vascular aging in the normal population, we examined the profile of lamin A expression in normal and aged VSMCs. In vitro, aged VSMCs rapidly accumulated prelamin A coincidently with nuclear morphology defects, and these defects were reversible by treatment with farnesylation inhibitors and statins. In human arteries, prelamin A accumulation was not observed in young healthy vessels but was prevalent in medial VSMCs from aged individuals and in atherosclerotic lesions, where it often colocalized with senescent and degenerate VSMCs. Prelamin A accumulation correlated with downregulation of the lamin A processing enzyme Zmpste24/FACE1, and FACE1 mRNA and protein levels were reduced in response to oxidative stress. Small interfering RNA knockdown of FACE1 reiterated the prelamin A-induced nuclear morphology defects characteristic of aged VSMCs, and overexpression of prelamin A accelerated VSMC senescence. We show that prelamin A acts to disrupt mitosis and induce DNA damage in VSMCs, leading to mitotic failure, genomic instability, and premature senescence. CONCLUSIONS: This study shows that prelamin A is a novel biomarker of VSMC aging and disease that acts to accelerate senescence. It therefore represents a novel target to ameliorate the effects of age-induced vascular dysfunction.

Defective DNA-damage repair induced by nuclear lamina dysfunction is a key mediator of smooth muscle cell aging.

Accumulation of DNA damage is a major driving force of normal cellular aging and has recently been demonstrated to hasten the development of vascular diseases such as atherosclerosis. VSMCs (vascular smooth muscle cells) are essential for vessel wall integrity and repair, and maintenance of their proliferative capacity is essential for vascular health. The signalling pathways that determine VSMC aging remain poorly defined; however, recent evidence implicates persistent DNA damage and the A-type nuclear lamins as key regulators of this process. In the present review, we discuss the importance of the nuclear lamina in the spatial organization of nuclear signalling events, including the DNA-damage response. In particular, we focus on the evidence suggesting that prelamin A accumulation interferes with nuclear spatial compartmentalization by disrupting chromatin organization and DNA-damage repair pathways to promote VSMC aging and senescence.