A critical role for calponin 2 in vascular development

scRNA-seq reveals the diversity of the developing cardiac cell lineage and molecular players in heart rhythm regulation

We utilized scRNA-seq to delineate the diversity of cell types in the zebrafish heart. Transcriptome profiling of over 50,000 cells at 48 and 72 hpf defined at least 18 discrete cell lineages of the developing heart. Utilizing well-established gene signatures, we identified a population of cells likely to be the primary pacemaker and characterized the transcriptome profile defining this critical cell type. Two previously uncharacterized genes, atp1b3b and colec10, were found to be enriched in the sinoatrial cardiomyocytes. CRISPR/Cas9-mediated knockout of these two genes significantly reduced heart rate, implicating their role in cardiac development and conduction. Additionally, we describe other cardiac cell lineages, including the endothelial and neural cells, providing their expression profiles as a resource. Our results established a detailed atlas of the developing heart, providing valuable insights into cellular and molecular mechanisms, and pinpointed potential new players in heart rhythm regulation.

Mechanoregulation and function of calponin and transgelin

It is well known that chemical energy can be converted to mechanical force in biological systems by motor proteins such as myosin ATPase. It is also broadly observed that constant/static mechanical signals potently induce cellular responses. However, the mechanisms that cells sense and convert the mechanical force into biochemical signals are not well understood. Calponin and transgelin are a family of homologous proteins that participate in the regulation of actin-activated myosin motor activity. An isoform of calponin, calponin 2, has been shown to regulate cytoskeleton-based cell motility functions under mechanical signaling. The expression of the calponin 2 gene and the turnover of calponin 2 protein are both under mechanoregulation. The regulation and function of calponin 2 has physiological and pathological significance, as shown in platelet adhesion, inflammatory arthritis, arterial atherosclerosis, calcific aortic valve disease, post-surgical fibrotic peritoneal adhesion, chronic proteinuria, ovarian insufficiency, and tumor metastasis. The levels of calponin 2 vary in different cell types, reflecting adaptations to specific tissue environments and functional states. The present review focuses on the mechanoregulation of calponin and transgelin family proteins to explore how cells sense steady tension and convert the force signal to biochemical activities. Our objective is to present a current knowledge basis for further investigations to establish the function and mechanisms of calponin and transgelin in cellular mechanoregulation.

Loss of Calponin 2 causes premature ovarian insufficiency in mice

BACKGROUND

Premature ovarian insufficiency (POI) is a condition defined as women developing menopause before 40 years old. These patients display low ovarian reserve at young age and difficulties to conceive even with assisted reproductive technology. The pathogenesis of ovarian insufficiency is not fully understood. Genetic factors may underlie most of the cases. Actin cytoskeleton plays a pivotal role in ovarian folliculogenesis. Calponin 2 encoded by the Cnn2 gene is an actin associated protein that regulates motility and mechanical signaling related cellular functions.

RESULTS

The present study compared breeding of age-matched calponin 2 knockout (Cnn2-KO) and wild type (WT) mice and found that Cnn2-KO mothers had significantly smaller litter sizes. Ovaries from 4 weeks old Cnn2-KO mice showed significantly lower numbers of total ovarian follicles than WT control with the presence of multi-oocyte follicles. Cnn2-KO mice also showed age-progressive earlier depletion of ovarian follicles. Cnn2 expression is detected in the cumulus cells of the ovarian follicles of WT mice and colocalizes with actin stress fiber, tropomyosin and myosin II in primary cultures of cumulus cells.

CONCLUSIONS

The findings demonstrate that the loss of calponin 2 impairs ovarian folliculogenesis with premature depletion of ovarian follicles. The role of calponin 2 in ovarian granulosa cells suggests a molecular target for further investigations on the pathogenesis of POI and for therapeutic development.

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.

Evolution and function of calponin and transgelin

Calponin and transgelin (originally named SM22) are homologous cytoskeleton proteins that regulate actin-activated myosin motor functions in smooth muscle contraction and non-muscle cell motility during adhesion, migration, proliferation, phagocytosis, wound healing, and inflammatory responses. They are abundant cytoskeleton proteins present in multiple cell types whereas their physiological functions remain to be fully established. This focused review summarizes the evolution of genes encoding calponin and transgelin and their isoforms and discusses the structural similarity and divergence in vertebrate and invertebrate species in the context of functions in regulating cell motility. As the first literature review focusing on the evolution of the calponin-transgelin family of proteins in relevance to their structure-function relationship, the goal is to outline a foundation of current knowledge for continued investigations to understand the biological functions of calponin and transgelin in various cell types during physiological and pathological processes.

Loss of Calponin 2 causes age-progressive proteinuria in mice

Proteinuria is a major manifestation of kidney disease, reflecting injuries of glomerular podocytes. Actin cytoskeleton plays a pivotal role in stabilizing the foot processes of podocytes against the hydrostatic pressure of filtration. Calponin is an actin associated protein that regulates mechanical tension-related cytoskeleton functions and its role in podocytes has not been established. Here we studied the kidney phenotypes of calponin isoform 2 knockout (KO) mice. Urine samples were examined to quantify the ratio of albumin and creatinine. Kidney tissue samples were collected for histology and ultrastructural studies. A mouse podocyte cell line (E11) was used to study the expression and cellular localization of calponin 2. In comparison with wild-type (WT) controls, calponin 2 KO mice showed age-progressive high proteinuria and degeneration of renal glomeruli. High levels of calponin 2 are expressed in E11 podocytes and colocalized with actin stress fibers, tropomyosin and myosin IIA. Electron microscopy showed that aging calponin 2 KO mice had effacement of the podocyte foot processes and increased thickness of the glomerular basement membrane as compared to that of WT control. The findings demonstrate that deletion of calponin 2 aggravates age-progressive degeneration of the glomerular structure and function as filtration barrier. The critical role of calponin 2 in podocytes suggests a molecular target for understanding the pathogenesis of proteinuria and therapeutic development.

Changes in cardiac proteome and metabolome following exposure to the PAHs retene and fluoranthene and their mixture in developing rainbow trout alevins

Exposure to polycyclic aromatic hydrocarbons (PAHs) is known to affect developing organisms. Utilization of different omics-based technologies and approaches could therefore provide a base for the discovery of novel mechanisms of PAH induced development of toxicity. To this aim, we investigated how exposure towards two PAHs with different toxicity mechanisms: retene (an aryl hydrocarbon receptor 2 (Ahr2) agonist), and fluoranthene (a weak Ahr2 agonist and cytochrome P450 inhibitor (Cyp1a)), either alone or as a mixture, affected the cardiac proteome and metabolome in newly hatched rainbow trout alevins (Oncorhynchus mykiss). In total, we identified 65 and 82 differently expressed proteins (DEPs) across all treatments compared to control (DMSO) after 7 and 14 days of exposure. Exposure to fluoranthene altered the expression of 11 and 19 proteins, retene 29 and 23, while the mixture affected 44 and 82 DEPs by Days 7 and 14, respectively. In contrast, only 5 significantly affected metabolites were identified. Pathway over-representation analysis identified exposure-specific activation of phase II metabolic processes, which were accompanied with exposure-specific body burden profiles. The proteomic data highlights that exposure to the mixture increased oxidative stress, altered iron metabolism and impaired coagulation capacity. Additionally, depletion of several mini-chromosome maintenance components, in combination with depletion of several intermediate filaments and microtubules, among alevins exposed to the mixture, suggests compromised cellular integrity and reduced rate of mitosis, whereby affecting heart growth and development. Furthermore, the combination of proteomic and metabolomic data indicates altered energy metabolism, as per amino acid catabolism among mixture exposed alevins; plausibly compensatory mechanisms as to counteract reduced absorption and consumption of yolk. When considered as a whole, proteomic and metabolomic data, in relation to apical effects on the whole organism, provides additional insight into PAH toxicity and the effects of exposure on heart structure and molecular processes.

A rapid degradation of calponin 2 is required for cytokinesis

Calponin 2 is an actin cytoskeleton-associated protein and plays a role in regulating cell motility-related functions such as phagocytosis, migration, and division. We previously reported that overexpression of calponin 2 inhibits the rate of cell proliferation. To investigate the underlying mechanism, our present study found that the levels of endogenous calponin 2 in NIH3T3 and HEK293 cells rapidly decreased before cell division characterized by an absence at the actin contractile ring. In cells lacking endogenous calponin 2, transfective expression of GFP-fusion calponin 2 inhibited cell proliferation similar to that of nonfusion calponin 2. Fluorescent imaging studies of mitotic cells indicated that a proper level of calponin 2 expression and effective degradation during cytokinesis are necessary for normal cell division. Computer-assisted dynamic image analysis of dividing cells revealed that overexpression of calponin 2 significantly affects motility and shape behaviors of cells only on the interval from the start of anaphase to the start of cytokinesis, i.e., the pre-cytokinesis phase, but not on the interval from the start of cytokinesis to 50% completion of cytokinesis. The pre-cytokinesis degradation of calponin 2 was attenuated by MG132 inhibition of the ubiquitin proteasome and inhibitor of protein kinase C (PKC), suggesting that PKC phosphorylation-triggered degradation of calponin 2 could determine the rate of cytokinesis. The novel role of calponin 2 in regulating the rate of cytokinesis may be targeted for therapeutic applications such as in an inhibition of malignant tumor growth.

LncRNA NEAT1 Promotes Proliferation, Migration And Invasion Via Regulating miR-296-5p/CNN2 Axis In Hepatocellular Carcinoma Cells

Background

Emerging evidence has revealed that long noncoding RNA nuclear paraspeckle assembly transcript 1 (lncRNA NEAT1) is implicated in the development of various cancers. However, the underlying molecular mechanisms of NEAT1 in hepatocellular carcinoma (HCC) remain unclear.

Methods

The expression of NEAT1, miR-296-5p and Calponin 2 (CNN2) was detected by quantitative real-time polymerase chain reaction or Western blot, respectively. Cell proliferation and apoptosis were analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay or flow cytometry, respectively. Transwell assay was used to determine cell migration and invasion. The interaction between miR-296-5p and NEAT1 or CNN2 was analyzed by dual-luciferase reporter assay and RIP assay. Huh7 cells transfected with sh-NEAT1 were used to establish the murine xenograft model.

Results

NEAT1 was elevated in HCC tissues and cell lines. Knockdown of NEAT1 significantly inhibited proliferation, migration and invasion of HCC cells in vitro as well as tumor growth in vivo. NEAT1 was a sponge of miR-296-5p and remarkably reduced the level of miR-296-5p in HCC cells. Furthermore, NEAT1 silence significantly decreased the expression of CNN2, which was the direct target of miR-296-5p. Besides that, the tumor suppression caused by NEAT1 silence could be rescued by CNN2 restoration or miR-296-5p inhibition in vitro. Additionally, NEAT1 indirectly regulated CNN2 expression by competing to miR-296-5p in vitro and in vivo.

Conclusion

LncRNA NEAT1 contributes to HCC progression by regulating miR-296-5p/CNN2 axis, providing a novel regulatory mechanism for HCC development and a promising therapeutic target for the HCC treatment.

Downregulation of calponin 2 contributes to the quiescence of lung macrophages

Calponin 2 is an actin cytoskeleton-associated regulatory protein that inhibits the activity of myosin-ATPase and cytoskeleton dynamics. Recent studies have demonstrated that deletion of calponin 2 restricts the proinflammatory activation of macrophages in atherosclerosis and arthritis to attenuate the disease progression in mice. Here we demonstrate that the levels of calponin 2 vary among different macrophage populations, which may reflect their adaptation to specific tissue microenvironment corresponding to specific functional states. Interestingly, lung resident macrophages express significantly lower calponin 2 than peritoneal resident macrophages, which correlates with decreased substrate adhesion and reduced expression of proinflammatory cytokines and a proresolution phenotype. Deletion of calponin 2 in peritoneal macrophages also decreased substrate adhesion and downregulated the expression of proinflammatory cytokines. Providing the first line of defense against microbial invasion while receiving constant exposure to extrinsic antigens, lung macrophages need to maintain a necessary level of activity while limiting exaggerated inflammatory reaction. Therefore, their low level of calponin 2 may reflect an important physiological adaption. Downregulation of calponin 2 in macrophages may be targeted as a cytoskeleton-based novel mechanism, possibly via endoplasmic reticulum stress altering the processing and secretion of cytokines, to regulate immune response and promote quiescence for the treatment of inflammatory diseases.

Calponin-3 is critical for coordinated contractility of actin stress fibers

Contractile actomyosin bundles, stress fibers, contribute to morphogenesis, migration, and mechanosensing of non-muscle cells. In addition to actin and non-muscle myosin II (NMII), stress fibers contain a large array of proteins that control their assembly, turnover, and contractility. Calponin-3 (Cnn3) is an actin-binding protein that associates with stress fibers. However, whether Cnn3 promotes stress fiber assembly, or serves as either a positive or negative regulator of their contractility has remained obscure. Here, we applied U2OS osteosarcoma cells as a model system to study the function of Cnn3. We show that Cnn3 localizes to both NMII-containing contractile ventral stress fibers and transverse arcs, as well as to non-contractile dorsal stress fibers that do not contain NMII. Fluorescence-recovery-after-photobleaching experiments revealed that Cnn3 is a dynamic component of stress fibers. Importantly, CRISPR/Cas9 knockout and RNAi knockdown studies demonstrated that Cnn3 is not essential for stress fiber assembly. However, Cnn3 depletion resulted in increased and uncoordinated contractility of stress fibers that often led to breakage of individual actomyosin bundles within the stress fiber network. Collectively these results provide evidence that Cnn3 is dispensable for the assembly of actomyosin bundles, but that it is required for controlling proper contractility of the stress fiber network.

Lentivirus-mediated shRNA Targeting CNN2 Inhibits Hepatocarcinoma in Vitro and in Vivo

Objective: Hepatocellular carcinoma (HCC) is one of the most common malignant tumors with a high rate of mortality. Our previous study shows the expression of calponin 2 (CNN2) is up-regulated in hepatocellular carcinoma tissues, especially in metastatic ones. To better understand the role of CNN2 in HCC, RNA interference (RNAi) was used to explore its role in tumor growth and metastasis. Methods: Lentivirus-mediated CNN2-shRNA was transfected into SK-hep-1 cells, and the efficacy of CNN2 expression, cell migration, invasion, proliferation and cell cycles were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR), Western blot (WB), Transwell assay, methyl thiazol tetrazolium assay and flow cytometry, respectively. SK-hep-1 cells transfected with Lentivirus-CNN2 shRNA were xenografted in Balb/C nude mice to explore the effect of CNN2-shRNA in tumor growth. Xenograft tumor tissues were examined for their histopathology, cell apoptosis, the expression of total protein and their corresponding phosphorylated protein of MEK1/2, ERK1/2, AKT, by hematoxylin and eosin stain (H & E staining), TUNEL assay, immunohistochemical technique, respectively. Results: Our research shows it is evident that CNN2 shRNA can effectively down-regulate the expressions of CNN2 mRNA and protein, inhibit cell proliferations, arrest cell cycles at the S phase and reduce cell migration and invasion. SK-hep-1 cells with CNN2 down-regulation have markedly attenuated tumor growth in nude mice. Xenograft tumor tissues have displayed typical tumor characteristics and no apoptosis is detected in shRNA group or in control group. No metastatic tumor was found in any group of nude mice. With CNN2 protein down-regulation, the protein of pMEK1/2 and pERK1/2 are effectively down-regulated, except pAKT, AKT, MEK1/2 and ERK1/2. Conclusions: CNN2 plays an important role in tumor growth and metastasis, possibly through MEK1/2-ERK1/2 signaling pathway. Our study illustrate that CNN2 might be a potential target in HCC molecular target therapy.

Increased expression of calponin 2 is a positive prognostic factor in pancreatic ductal adenocarcinoma

Calponin 2 plays an important role in regulating actin cytoskeleton, which is critical for cell division and migration. Previous studies have demonstrated that calponin 2 inhibits prostate cancer cell proliferation and metastasis. However, the role of calponin 2 in pancreatic tumor growth, metastasis and patient survival remains unclear. Here, we demonstrate that the level of calponin 2 is a positive prognostic factor for patients with pancreatic ductal adenocarcinoma (PDAC). Patients with high calponin 2 expression in the tumor presented less lymph node metastasis and longer survival. Knockdown of calponin 2 facilitated pancreatic cancer cell proliferation and metastasis. Further experiments suggested that PI3K/AKT, NF-κB, Vimentin, Fibronectin, Snail and Slug were upregulated and E-cadherin was downregulated after calponin 2 was knocked down, implicating altered functions in PDAC proliferation and metastasis. In addition, we verified that calponin 2 functioned through inhibiting PI3K/AKT and NF-κB pathways. Our study suggests that the upregulation of calponin 2 in PDAC correlates to lower malignancy and presents a novel target for the development of new treatment.

Deletion of Calponin 2 in Mouse Fibroblasts Increases Myosin II-Dependent Cell Traction Force

Cell traction force (CTF) plays a critical role in controlling cell shape, permitting cell motility, and maintaining cellular homeostasis in many biological processes such as angiogenesis, development, wound healing, and cancer metastasis. Calponin is an actin filament-associated cytoskeletal protein in smooth muscles and multiple types of non-muscle cells. An established biochemical function of calponin is the inhibition of myosin ATPase in smooth muscle cells. Vertebrates have three calponin isoforms. Among them, calponin 2 is expressed in epithelial cells, endothelial cells, macrophages, myoblasts, and fibroblasts and plays a role in regulating cytoskeleton activities such as cell adhesion, migration, and cytokinesis. Knockout (KO) of the gene encoding calponin 2 (Cnn2) in mice increased cell motility, suggesting a function of calponin 2 in modulating CTF. In this study, we examined fibroblasts isolated from Cnn2 KO and wild-type (WT) mice using CTF microscopy. Primary mouse fibroblasts were cultured on polyacrylamide gel substrates embedded with fluorescent beads to measure root-mean-square traction, total strain energy, and net contractile movement. The results showed that calponin 2-null fibroblasts exhibit traction force greater than that of WT cells. Adherent calponin 2-null fibroblasts de-adhered faster than the WT control during mild trypsin treatment, consistent with an increased CTF. Blebbistatin, an inhibitor of myosin II ATPase, is more effective upon an alteration in cell morphology when calponin 2 is present in WT fibroblasts than that on Cnn2 KO cells, indicating their additive effects in inhibiting myosin motor activity. The novel finding that calponin 2 regulates myosin-dependent CTF in non-muscle cells demonstrates a mechanism for controlling cell motility-based functions.

Deletion of calponin 2 in macrophages alters cytoskeleton-based functions and attenuates the development of atherosclerosis

Arterial atherosclerosis is an inflammatory disease. Macrophages play a major role in the pathogenesis and progression of atherosclerotic lesions. Modulation of macrophage function is a therapeutic target for the treatment of atherosclerosis. Calponin is an actin-filament-associated regulatory protein that inhibits the activity of myosin-ATPase and dynamics of the actin cytoskeleton. Encoded by the gene Cnn2, calponin isoform 2 is expressed at significant levels in macrophages. Deletion of calponin 2 increases macrophage migration and phagocytosis. In the present study, we investigated the effect of deletion of calponin 2 in macrophages on the pathogenesis and development of atherosclerosis. The results showed that macrophages isolated from Cnn2 knockout mice ingested a similar level of acetylated low-density lipoprotein (LDL) to that of wild type (WT) macrophages but the resulting foam cells had significantly less hindered velocity of migration. Systemic or myeloid cell-specific Cnn2 knockouts effectively attenuated the development of arterial atherosclerosis lesions with less macrophage infiltration in apolipoprotein E knockout mice. Consistently, calponin 2-null macrophages produced less pro-inflammatory cytokines than that of WT macrophages, and the up-regulation of pro-inflammatory cytokines in foam cells was also attenuated by the deletion of calponin 2. Calponin 2-null macrophages and foam cells have significantly weakened cell adhesion, indicating a role of cytoskeleton regulation in macrophage functions and inflammatory responses, and a novel therapeutic target for the treatment of arterial atherosclerosis.

Deletion of calponin 2 in macrophages attenuates the severity of inflammatory arthritis in mice

Calponin is an actin cytoskeleton-associated protein that regulates motility-based cellular functions. Three isoforms of calponin are present in vertebrates, among which calponin 2 encoded by the Cnn2 gene is expressed in multiple types of cells, including blood cells from the myeloid lineage. Our previous studies demonstrated that macrophages from Cnn2 knockout (KO) mice exhibit increased migration and phagocytosis. Intrigued by an observation that monocytes and macrophages from patients with rheumatoid arthritis had increased calponin 2, we investigated anti-glucose-6-phosphate isomerase serum-induced arthritis in Cnn2-KO mice for the effect of calponin 2 deletion on the pathogenesis and pathology of inflammatory arthritis. The results showed that the development of arthritis was attenuated in systemic Cnn2-KO mice with significantly reduced inflammation and bone erosion than that in age- and stain background-matched C57BL/6 wild-type mice. In vitro differentiation of calponin 2-null mouse bone marrow cells produced fewer osteoclasts with decreased bone resorption. The attenuation of inflammatory arthritis was confirmed in conditional myeloid cell-specific Cnn2-KO mice. The increased phagocytotic activity of calponin 2-null macrophages may facilitate the clearance of autoimmune complexes and the resolution of inflammation, whereas the decreased substrate adhesion may reduce osteoclastogenesis and bone resorption. The data suggest that calponin 2 regulation of cytoskeleton function plays a novel role in the pathogenesis of inflammatory arthritis, implicating a potentially therapeutic target.

Calponin isoforms CNN1, CNN2 and CNN3: Regulators for actin cytoskeleton functions in smooth muscle and non-muscle cells

Calponin is an actin filament-associated regulatory protein expressed in smooth muscle and many types of non-muscle cells. Three homologous genes, CNN1, CNN2 and CNN3, encoding calponin isoforms 1, 2, and 3, respectively, are present in vertebrate species. All three calponin isoforms are actin-binding proteins with functions in inhibiting actin-activated myosin ATPase and stabilizing the actin cytoskeleton, while each isoform executes different physiological roles based on their cell type-specific expressions. Calponin 1 is specifically expressed in smooth muscle cells and plays a role in fine-tuning smooth muscle contractility. Calponin 2 is expressed in both smooth muscle and non-muscle cells and regulates multiple actin cytoskeleton-based functions. Calponin 3 participates in actin cytoskeleton-based activities in embryonic development and myogenesis. Phosphorylation has been extensively studied for the regulation of calponin functions. Cytoskeleton tension regulates the transcription of CNN2 gene and the degradation of calponin 2 protein. This review summarizes our knowledge learned from studies over the past three decades, focusing on the evolutionary lineage of calponin isoform genes, their tissue- and cell type-specific expressions, structure-function relationships, and mechanoregulation.

A Conditional Knockout Mouse Model Reveals That Calponin-3 Is Dispensable for Early B Cell Development

Calponins form an evolutionary highly conserved family of actin filament-associated proteins expressed in both smooth muscle and non-muscle cells. Whereas calponin-1 and calponin-2 have already been studied to some extent, little is known about the role of calponin-3 under physiological conditions due to the lack of an appropriate animal model. Here, we have used an unbiased screen to identify novel proteins implicated in signal transduction downstream of the precursor B cell receptor (pre-BCR) in B cells. We find that calponin-3 is expressed throughout early B cell development, localizes to the plasma membrane and is phosphorylated in a Syk-dependent manner, suggesting a putative role in pre-BCR signaling. To investigate this in vivo, we generated a floxed calponin-3-GFP knock-in mouse model that enables tracking of cells expressing calponin-3 from its endogenous promoter and allows its tissue-specific deletion. Using the knock-in allele as a reporter, we show that calponin-3 expression is initiated in early B cells and increases with their maturation, peaking in the periphery. Surprisingly, conditional deletion of the Cnn3 revealed no gross defects in B cell development despite this regulated expression pattern and the in vitro evidence, raising the question whether other components may compensate for its loss in lymphocytes. Together, our work identifies calponin-3 as a putative novel mediator downstream of the pre-BCR. Beyond B cells, the mouse model we generated will help to increase our understanding of calponin-3 in muscle and non-muscle cells under physiological conditions.

The potential role of DNA methylation in abdominal aortic aneurysms

Abdominal aortic aneurysm (AAA) is a complex disorder that has a significant impact on the aging population. While both genetic and environmental risk factors have been implicated in AAA formation, the precise genetic markers involved and the factors influencing their expression remain an area of ongoing investigation. DNA methylation has been previously used to study gene silencing in other inflammatory disorders and since AAA has an extensive inflammatory component, we sought to examine the genome-wide DNA methylation profiles in mononuclear blood cells of AAA cases and matched non-AAA controls. To this end, we collected blood samples and isolated mononuclear cells for DNA and RNA extraction from four all male groups: AAA smokers (n = 11), AAA non-smokers (n = 9), control smokers (n = 10) and control non-smokers (n = 11). Methylation data were obtained using the Illumina 450k Human Methylation Bead Chip and analyzed using the R language and multiple Bioconductor packages. Principal component analysis and linear analysis of CpG island subsets identified four regions with significant differences in methylation with respect to AAA: kelch-like family member 35 (KLHL35), calponin 2 (CNN2), serpin peptidase inhibitor clade B (ovalbumin) member 9 (SERPINB9), and adenylate cyclase 10 pseudogene 1 (ADCY10P1). Follow-up studies included RT-PCR and immunostaining for CNN2 and SERPINB9. These findings are novel and suggest DNA methylation may play a role in AAA pathobiology.

Transcriptional Response to Acute Thermal Exposure in Juvenile Chinook Salmon Determined by RNAseq

Thermal exposure is a serious and growing challenge facing fish species worldwide. Chinook salmon (Oncorhynchus tshawytscha) living in the southern portion of their native range are particularly likely to encounter warmer water due to a confluence of factors. River alterations have increased the likelihood that juveniles will be exposed to warm water temperatures during their freshwater life stage, which can negatively impact survival, growth, and development and pose a threat to dwindling salmon populations. To better understand how acute thermal exposure affects the biology of salmon, we performed a transcriptional analysis of gill tissue from Chinook salmon juveniles reared at 12° and exposed acutely to water temperatures ranging from ideal to potentially lethal (12° to 25°). Reverse-transcribed RNA libraries were sequenced on the Illumina HiSeq2000 platform and a de novo reference transcriptome was created. Differentially expressed transcripts were annotated using Blast2GO and relevant gene clusters were identified. In addition to a high degree of downregulation of a wide range of genes, we found upregulation of genes involved in protein folding/rescue, protein degradation, cell death, oxidative stress, metabolism, inflammation/immunity, transcription/translation, ion transport, cell cycle/growth, cell signaling, cellular trafficking, and structure/cytoskeleton. These results demonstrate the complex multi-modal cellular response to thermal stress in juvenile salmon.

A novel role of h2-calponin in regulating whole blood thrombosis and platelet adhesion during physiologic flow

Calponin is an actin filament-associated protein reported in platelets, although the specific isoform expressed and functional role were not identified. The h2-calponin isoform is expressed in myeloid-derived peripheral blood monocytes, where it regulates adhesion. Our objective was to characterize the presence and function of the h2 isoform of calponin in platelets. H2-calponin was detected in human and mouse platelets via Western blotting. Immunofluorescent staining demonstrated h2-calponin and actin colocalized in both human and wild-type mouse platelets at rest and following collagen activation. The kinetics of platelet adhesion and whole blood thrombosis during physiologic flow was evaluated in a microfluidic flow-based thrombosis assay. The time to initiation of rapid platelet/thrombus accumulation (lag time) was significantly longer in h2-calponin knockout versus wild-type mouse blood (130.02 ± 3.74 sec and 72.95 ± 16.23 sec, respectively, P < 0.05). There was no significant difference in the rate of platelet/thrombus accumulation during the rapid phase or the maximum platelet/thrombus accumulation. H2-calponin knockout mice also had prolonged bleeding time and blood loss. H2-calponin in platelets facilitates early interactions between platelets and collagen during physiologic flow, but does not significantly affect the rate or magnitude of platelet/thrombus accumulation. H2-calponin knockout mice take 2.3 times longer to achieve hemostasis compared to wild-type controls in a tail bleeding model. The ability to delay platelet accumulation without inhibiting downstream thrombotic potential would be of significant therapeutic value, thus h2-calponin may be a novel target for therapeutic platelet inhibition.

Calponin-h2: a potential serum marker for the early detection of human breast cancer?

Early diagnosis is the key for the successful treatment of breast cancer. A serum marker for the early detection of breast cancer could significantly reduce breast cancer morbidity and mortality by bringing the time of diagnosis at an earlier and therefore still curable stage. So far, no biomarker for the early detection is available for the clinical routine. The aim of the present study was to evaluate the use of calponin-h2 as a blood-based biomarker for the early diagnosis of this disease. Using two monoclonal antibodies against calponin-h2, we developed a sandwich ELISA to analyze the serum levels of calponin-h2. In order to evaluate the diagnostic potential of this biomarker, patients with breast cancer (n = 76), benign diseases of the breast (n = 51) and healthy females (n = 24) were analyzed. Serum levels above 10 ng/ml were only observed in patients with breast cancer (n = 8; 10.5%). Further large-scale studies and preanalytic evaluations are necessary to clarify the definite role of calponin-h2 as a biomarker in breast cancer management.

Diminished expression of h2-calponin in prostate cancer cells promotes cell proliferation, migration and the dependence of cell adhesion on substrate stiffness

•

Calponin is an actin filament-associated protein and its h2 isoform inhibits cell motility.

•

H2-calponin expression is strong in prostate epithelial cells and diminished in cancerous cells.

•

Low h2-calponin metastatic prostate cancer cells had faster rates of cell proliferation and migration.

•

Low h2-calponin metastatic prostate cancer cells showed reduced substrate adhesion.

•

Low h2-calponin prostate cancer cells had a higher dependence on substrate stiffness.

Calponin is an actin filament-associated protein and its h2 isoform inhibits cell motility. Here we report significant expression of h2-calponin in prostate epithelial cells, which is diminished in cancerous cells. Comparison between a prostate cancer cell line PC3 and its metastatic derivative PC3-M showed lower levels of h2-calponin in PC3-M, corresponding to faster rates of cell proliferation and migration. Substrate adhesion of PC3 and PC3-M cells was positively correlated to the level of h2-calponin and the adhesion of PC3-M exhibited a higher dependence on substrate stiffness. Such effects of h2-calponin on cell proliferation, migration and substrate adhesion were also seen in normal versus cancerous primary prostate cells. Further supporting the role of h2-calponin in inhibiting cell motility, fibroblasts isolated from h2-calponin knockout mice proliferated and migrated faster than that of wild type fibroblasts. Transfective over-expression of h2-calponin in PC3-M cells effectively inhibited cell proliferation and migration. The results suggest that the diminished expression of h2-calponin in prostate cancer cells increases cell motility, decreases substrate adhesion, and promotes adhesion on high stiffness substrates.

Mechanism of calponin stabilization of cross-linked actin networks

The actin-binding protein calponin has been previously implicated in actin cytoskeletal regulation and is thought to act as an actin stabilizer, but the mechanism of its function is poorly understood. To investigate this underlying physical mechanism, we studied an in vitro model system of cross-linked actin using bulk rheology. Networks with basic calponin exhibited a delayed onset of strain stiffening (10.0% without calponin, 14.9% with calponin) and were able to withstand a higher maximal strain before failing (35% without calponin, 56% with calponin). Using fluorescence microscopy to study the mechanics of single actin filaments, we found that calponin increased the flexibility of actin filaments, evident as a decrease in persistence length from 17.6 μm without to 7.7 μm with calponin. Our data are consistent with current models of affine strain behavior in semiflexible polymer networks, and suggest that calponin stabilization of actin networks can be explained purely by changes in single-filament mechanics. We propose a model in which calponin stabilizes actin networks against shear through a reduction of persistence length of individual filaments.

Mechanoregulation of h2-calponin gene expression and the role of Notch signaling

The essential role of mechanical signals in regulating the function of living cells is universally observed. However, how mechanical signals are transduced in cells to regulate gene expression is largely unknown. We previously demonstrated that the gene encoding h2-calponin (Cnn2) is sensitively regulated by mechanical tension. In the present study, mouse genomic DNA containing the Cnn2 promoter was cloned, and a nested set of 5' truncations was studied. Transcriptional activity of the Cnn2 promoter-reporter constructs was examined in transfected NIH/3T3, HEK293, and C2C12 cells for their responses to the stiffness of culture substrate. The results showed significant transcriptional activities of the -1.00- and -1.24-kb promoter constructs, whereas the -0.61-kb construct was inactive. The -1.38-, -1.57-, and -2.12-kb constructs showed higher transcriptional activity, whereas only the -1.57- and -2.12-kb constructs exhibited repression of expression when the host cells were cultured on low stiffness substrate. Internal deletion of the segment between -1.57 and -1.38 kb in the -2.12-kb promoter construct abolished the low substrate stiffness-induced repression. Site-specific deletion or mutation of an HES-1 transcription factor binding site in this region also abolished this repression effect. The level of HES-1 increased in cells cultured under a low tension condition, corresponding to the down-regulation of h2-calponin. h2-Calponin gene expression is further affected by the treatment of cells with Notch inhibitor and activator, suggesting an upstream signaling mechanism.

Calponin 3 regulates stress fiber formation in dermal fibroblasts during wound healing

Skin wound healing is an intricate process involving various cell types and molecules. In granulation tissue, fibroblasts proliferate and differentiate into myofibroblasts and generate mechanical tension for wound closure and contraction. Actin stress fibers formed in these cells, especially those containing α-smooth muscle actin (α-SMA), are the central machinery for contractile force generation. In the present study, calponin 3 (CNN3), which has a phosphorylation-dependent actin-binding property, was identified in the molecular mechanism underlying stress fiber formation. CNN3 was expressed by fibroblasts/myofibroblasts in the proliferation phase of wound healing, and was associated with α-SMA in stress fibers formed by cultured dermal fibroblasts. CNN3 expression was post-transcriptionally regulated by tension, as demonstrated by disruption of actin filament organization under floating culture or blebbistatin treatment. CNN3 knockdown in primary fibroblasts impaired stress fiber formation, resulting in a phenotype of decreased cellular dynamics such as cell motility and contractile ability. These findings indicate that CNN3 participates in actin stress fiber remodeling, which is required for cell motility and contraction of dermal fibroblasts in the wound healing process.

Differentiated markers in undifferentiated cells: expression of smooth muscle contractile proteins in multipotent bone marrow mesenchymal stem cells

In studying the differentiation of stem cells along smooth muscle lineage, smooth muscle cell (SMC) contractile proteins serve as markers for the relative state of maturation. Yet, recent evidence suggests that some SMC markers are probably expressed in multipotent mesenchymal stem cells (MSCs). Such a paradox necessitates investigations to re-examine their role as differentiated markers in MSCs. We tried to detect the expression of four widely used SMC markers including α-smooth muscle actin (α-SMA), h1-calponin, desmin and smooth muscle myosin heavy chain (SM-MHC), as well as the other isoforms of calponin family in resting MSCs. Then we used three different conditions to initiate MSCs differentiation along SMC lineage, and examined the alternation of SMC markers expression at both the transcript level and protein level. Desmin and h1-calponin are expressed in MSCs, in the presence or absence of SMC induction conditions. Moreover, MSCs are shown to express all known isoforms of calponin. Double-staining reveals that h1-calponin +/α-SMA - cells constitute the majority of resting MSCs. Under differentiated conditions, expression of SM-MHC was initiated and expression of α-SMA was promoted. The expression of SM-MHC and upregulation of α-SMA are relatively reliable indications of a mature smooth muscle phenotype in MSCs. Given that the cells are particularly rich in calponins expression, we postulate possible roles of these proteins in regulating cellular function by taking part in actin cytoskeleton and signaling. These findings imply that an extensive study of the cell physiology of MSCs should focus on the functional roles for these proteins, rather than simply regard them as differentiated markers.

Global Gene Expression Profiling Reveals Functional Importance of Sirt2 in Endothelial Cells under Oxidative Stress

The NAD+-dependent deacetylases Sirt1 and Sirt2 mediate cellular stress responses and are highly expressed in vascular endothelial cells. In contrast to the well-documented protective actions of Sirt1, the role of endothelial Sirt2 remains unknown. Using cDNA microarray and PCR validation, we examined global gene expression changes in response to Sirt2 knock down in primary human umbilical vein endothelial cells under oxidative stress. We found that Sirt2 knock down changed expression of 340 genes, which are mainly involved in cellular processes including actin binding, cellular amino acid metabolic process, transmembrane receptor protein serine/threonine kinase signaling, ferrous iron transport, protein transport and localization, cell morphogenesis, and functions associated with endosome membrane and the trans-Golgi network. These genes and associated functions were largely non-overlapping with those altered by Sirt1 knock down. Moreover, we showed that pharmacological inhibition of Sirt2 attenuated oxidant-induced cell toxicity in endothelial cells. These suggest that Sirt2 is functionally important in endothelial cells under oxidative stress, and may have a primarily distinct role as compared to Sirt1. Our results may provide a basis for future studies aiming to dissect the specific signaling pathway(s) that mediates specific Sirt2 functions in endothelial cells.

Characterization of the human smooth muscle cell secretome for regenerative medicine

Smooth muscle cells (SMC) play a central role in maintaining the structural and functional integrity of muscle tissue. Little is known about the early in vitro events that guide the assembly of 'bioartificial tissue' (constructs) and recapitulate the key aspects of smooth muscle differentiation and development before surgical implantation. Biomimetic approaches have been proposed that enable the identification of in vitro processes which allow standardized manufacturing, thus improving both product quality and the consistency of patient outcomes. One essential element of this approach is the description of the SMC secretome, that is, the soluble and deposited factors produced within the three-dimensional (3D) extracellular matrix (ECM) microenvironment. In this study, we utilized autologous SMC from multiple tissue types that were expanded ex vivo and generated with a rigorous focus on operational phenotype and genetic stability. The objective of this study was to characterize the spatiotemporal dynamics of the first week of organoid maturation using a well-defined in vitro-like, 3D-engineered scale model of our validated manufacturing process. Functional proteomics was used to identify the topological properties of the networks of interacting proteins that were derived from the SMC secretome, revealing overlapping central nodes related to SMC differentiation and proliferation, actin cytoskeleton regulation, and balanced ECM accumulation. The critical functions defined by the Ingenuity Pathway Analysis included cell signaling, cellular movement and proliferation, and cellular and organismal development. The results confirm the phenotypic and functional similarity of the SMC generated by our platform technology at the molecular level. Furthermore, these data validate the biomimetic approaches that have been established to maintain manufacturing consistency.

Effects of basic calponin on the flexural mechanics and stability of F-actin

The cellular actin cytoskeleton plays a central role in the ability of cells to properly sense, propagate, and respond to external stresses and other mechanical stimuli. Calponin, an actin-binding protein found both in muscle and non-muscle cells, has been implicated in actin cytoskeletal organization and regulation. In this work, we studied the mechanical and structural interaction of actin with basic calponin, a differentiation marker in smooth muscle cells, on a single filament level. We imaged fluorescently labeled thermally fluctuating actin filaments and found that at moderate calponin binding densities, actin filaments were more flexible, evident as a reduction in persistence length from 8.0 to 5.8 μm. When calponin-decorated actin filaments were subjected to shear, we observed a marked reduction of filament lengths after decoration with calponin, which we argue was due to shear-induced filament rupture rather than depolymerization. This increased shear susceptibility was exacerbated with calponin concentration. Cryo-electron microscopy results confirmed previously published negative stain electron microscopy results and suggested alterations in actin involving actin subdomain 2. A weakening of F-actin intermolecular association is discussed as the underlying cause of the observed mechanical perturbations.

Scaffolding proteins and non-proliferative functions of ERK1/2

Studies of ERK1/2 generally focus on the regulation of nuclear ERK1/2 function mainly related to proliferation, whereas less attention has been drawn to the role ERK1/2 plays in the cytosol. Scaffolding proteins for ERK1/2 have been shown to control the time point and also the intracellular location of ERK1/2 activation. Hence, by concentrating ERK1/2 within subcellular compartments, scaffolding proteins restrict the substrate specificity of ERK1/2 and thus optimize the cell response for specific signal transduction programs in order to manipulate specific cellular functions. We have presented evidence that the F-actin binding protein calponin represents a new type of ERK1/2 scaffold, controlling the activation of a subfraction of ERK1/2 which is connected solely to contractile and/or migratory events in a cell.

Proteomic changes in articular cartilage of human endemic osteoarthritis in China

Kashin-Beck disease (KBD) is a chronic endemic osteochondropathy with unclear pathogenesis. It is a degenerative disease similar to osteoarthritis, but with different manifestations of cartilage damage. The aim of this investigation was to show the protein changes in KBD cartilage and to identify the candidate proteins in order to understand the pathogenesis of the disease. Proteins were extracted from the media of primary cell cultures of KBD and normal chondrocytes, and separated by two-dimensional fluorescence difference gel electrophoresis (2-D DIGE). MALDI-TOF/TOF analysis revealed statistically significant differences in 27 proteins from KBD chondrocyte cultures, which consisted of 17 up-regulated and ten down-regulated proteins. The results were further validated by Western blot analysis. The proteins identified are mainly involved in cellular redox homeostasis and stress response (MnSOD, Hsp27, Peroxiredoxin-1, and Cofilin-1), glycolysis (PGK-1, PGM-1, α-enolase), and cell motility and cytoskeletal organization (Actin, Calponin-2, and Keratin). These KBD-associated proteins indicate that cytoskeletal remodeling, glycometabolism, and oxidative stress are abnormal in KBD articular cartilage.

Podocin-green fluorescence protein allows visualization and functional analysis of podocytes

Podocytes do not remain fully differentiated when cultured, and they are difficult to image in vivo, making the study of podocyte biology challenging. Zebrafish embryos are transparent and develop a single, midline, pronephric glomerulus accessible for imaging and systematic functional analysis. Here, we describe a transgenic zebrafish line that expresses green fluorescence protein (GFP) from the zebrafish podocin promoter. The line recapitulates the endogenous pronephric podocin expression pattern, showing GFP expression exclusively in podocytes starting 2 days postfertilization. Using the podocyte GFP signal as a guide for dissection, we examined the pronephric glomerulus by scanning electron microscopy; the surface ultrastructure exhibited fine, interdigitating podocyte foot processes surrounding glomerular capillaries. To determine whether the GFP signal could serve as a direct readout of developmental abnormalities or injury to the glomerulus, we knocked down the podocyte-associated protein crb2b; this led to a loss of GFP signal. Thus, podocin-GFP zebrafish provide a model for ultrastructural studies and in vivo visualization and functional analysis of glomerular podocytes. This model should also be useful for high-throughput genetic or chemical analysis of glomerular development and function.

Analysis of differentially expressed genes in human rectal carcinoma using suppression subtractive hybridization

The existence and treatment of rectal cancer are important for the function of defecation and the quality of life. However, the precise mechanisms of rectal carcinogenesis remain unclear. To screen the overexpressed gene in rectal carcinoma, we performed suppressive subtractive hybridization (SSH) on rectal carcinoma cells and the corresponding normal rectal cells. A total of 64 recombinant clones were subjected to DNA sequencing analysis, and 9 known genes were found to overexpressed in the tumors compared with those of the normal tissues. The genes are ST3 beta-galactoside alpha-2,3-sialyltransferase (ST3GAL5), interferon-induced transmembrane protein 3 (IFITM3), platelet-derived growth factor A-associated protein 1 (PDAP1), AlkB alkylating repair homolog 3 (ALKBH3), nucleoside diphosphate linked moiety X (Nudix)-type motif 14 (NUDT14), calponin 2 (CNN2), mitogen-activated protein kinase 14 (MAPK14), aconitase 1 (ACO1), and selenophosphate synthetase 1 (SEPHS1). The expression profiles of the genes were further confirmed in rectal carcinoma cells and the corresponding normal rectal cells of 12 patients by quantitative real-time RT-PCR. Our results revealed that ST3GAL5, IFITM3, PDAP1, ALKBH3, NUDT14, CNN2, MAPK14, ACO1, and SEPHS1 may be involved in rectal carcinogenesis.

Calponin 3 regulates actin cytoskeleton rearrangement in trophoblastic cell fusion

Cell-cell fusion is an intriguing differentiation process, essential for placental development and maturation. A proteomic approach identified a cytoplasmic protein, calponin 3 (CNN3), related to the fusion of BeWo choriocarcinoma cells. CNN3 was expressed in cytotrophoblasts in human placenta. CNN3 gene knockdown promoted actin cytoskeletal rearrangement and syncytium formation in BeWo cells, suggesting CNN3 to be a negative regulator of trophoblast fusion. Indeed, CNN3 depletion promoted BeWo cell fusion. CNN3 at the cytoplasmic face of cytoskeleton was dislocated from F-actin with forskolin treatment and diffused into the cytoplasm in a phosphorylation-dependent manner. Phosphorylation sites were located at Ser293/296 in the C-terminal region, and deletion of this region or site-specific disruption of Ser293/296 suppressed syncytium formation. These CNN3 mutants were colocalized with F-actin and remained there after forskolin treatment, suggesting that dissociation of CNN3 from F-actin is modulated by the phosphorylation status of the C-terminal region unique to CNN3 in the CNN family proteins. The mutant missing these phosphorylation sites displayed a dominant negative effect on cell fusion, while replacement of Ser293/296 with aspartic acid enhanced syncytium formation. These results indicated that CNN3 regulates actin cytoskeleton rearrangement which is required for the plasma membranes of trophoblasts to become fusion competent.

Connective tissue growth factor in regulation of RhoA mediated cytoskeletal tension associated osteogenesis of mouse adipose-derived stromal cells

Background

Cytoskeletal tension is an intracellular mechanism through which cells convert a mechanical signal into a biochemical response, including production of cytokines and activation of various signaling pathways.

Methods/Principal Findings

Adipose-derived stromal cells (ASCs) were allowed to spread into large cells by seeding them at a low-density (1,250 cells/cm²), which was observed to induce osteogenesis. Conversely, ASCs seeded at a high-density (25,000 cells/cm²) featured small cells that promoted adipogenesis. RhoA and actin filaments were altered by changes in cell size. Blocking actin polymerization by Cytochalasin D influenced cytoskeletal tension and differentiation of ASCs. To understand the potential regulatory mechanisms leading to actin cytoskeletal tension, cDNA microarray was performed on large and small ASCs. Connective tissue growth factor (CTGF) was identified as a major regulator of osteogenesis associated with RhoA mediated cytoskeletal tension. Subsequently, knock-down of CTGF by siRNA in ASCs inhibited this osteogenesis.

Conclusions/Significance

We conclude that CTGF is important in the regulation of cytoskeletal tension mediated ASC osteogenic differentiation.

h3/Acidic calponin: an actin-binding protein that controls extracellular signal-regulated kinase 1/2 activity in nonmuscle cells

Migration of fibroblasts is important in wound healing. Here, we demonstrate a role and a mechanism for h3/acidic calponin (aCaP, CNN3) in REF52.2 cell motility, a fibroblast line rich in actin filaments. We show that the actin-binding protein h3/acidic calponin associates with stress fibers in the absence of stimulation but is targeted to the cell cortex and podosome-like structures after stimulation with a phorbol ester, phorbol-12,13-dibutyrate (PDBu). By coimmunoprecipitation and colocalization, we show that extracellular signal-regulated kinase (ERK)1/2 and protein kinase C (PKC)alpha constitutively associate with h3/acidic calponin and are cotargeted with h3/acidic calponin in the presence of PDBu. This targeting can be blocked by a PKC inhibitor but does not require phosphorylation of h3/acidic calponin at the PKC sites S175 or T184. Knockdown of h3/acidic calponin results in a loss of PDBu-mediated ERK1/2 targeting, whereas PKCalpha targeting is unaffected. Caldesmon is an actin-binding protein that regulates actomyosin interactions and is a known substrate of ERK1/2. Both ERK1/2 activity and nonmuscle l-caldesmon phosphorylation are blocked by h3/acidic calponin knockdown. Furthermore, h3/acidic calponin knockdown inhibits REF52.2 migration in an in vitro wound healing assay. Our findings are consistent with a model whereby h3/acidic calponin controls fibroblast migration by regulation of ERK1/2-mediated l-caldesmon phosphorylation.

Calponin in non-muscle cells

Calponin is an actin filament-associated regulatory protein expressed in smooth muscle and non-muscle cells. Calponin is an inhibitor of the actin-activated myosin ATPase. Three isoforms of calponin have been found in the vertebrates. Whereas the role of calponin in regulating smooth muscle contractility has been extensively investigated, the function and regulation of calponin in non-muscle cells is much less understood. Based on recent progresses in the field, this review focuses on the studies of calponin in non-muscle cells, especially its regulation by cytoskeleton tension and function in cell motility. The ongoing research has demonstrated that calponin plays a regulatory role in non-muscle cell motility. Therefore, non-muscle calponin is an attractive target for the control of cell proliferation, migration and phagocytosis, and the treatment of cancer metastasis.

Role of H2-calponin in regulating macrophage motility and phagocytosis

The actin cytoskeleton plays a major role in cell motility that is essential for the function of phagocytes. Calponin is an actin-associated regulatory protein. Here we report the finding of significant levels of the h2 isoform of calponin in peripheral blood cells of myeloid lineage. To study the functional significance, h2-calponin gene (Cnn2) interrupted mice were constructed. Germ line transmission of the Cnn2-flox-neo allele was obtained in chimeras from two independent clones of targeted embryonic stem cells. The insertion of the neo(R) cassette into intron 2 of the Cnn2 gene resulted in a significant knockdown of h2-calponin expression. Removing the frt-flanked neo(R) cassette by FLP1 recombinase rescued the knockdown effect. Cre recombinase-induced deletion of the loxP-flanked exon 2 eliminated the expression of h2-calponin protein. H2-calponin-free mice showed reduced numbers of peripheral blood neutrophils and monocytes. H2-calponin-free macrophages demonstrated a higher rate of proliferation and faster migration than that of h2-calponin-positive cells, consistent with a faster diapedesis of peripheral monocytes and neutrophils. H2-calponin-free macrophages showed reduced spreading in adhesion culture together with decreased tropomyosin in the actin cytoskeleton. The lack of h2-calponin also significantly increased macrophage phagocytotic activity, suggesting a novel mechanism to regulate phagocyte functions.

Proteome alteration induced by hTERT transfection of human fibroblast cells

Background

Telomerase confers cellular immortality by elongating telomeres, thereby circumventing the Hayflick limit. Extended-life-span cells have been generated by transfection with the human telomerase reverse transcriptase (hTERT) gene. hTERT transfected cell lines may be of outstanding interest to monitor the effect of drugs targeting the telomerase activity. The incidence of hTERT gene transfection at the proteome level is a prerequisite to that purpose. The effect of the transfection has been studied on the proteome of human fibroblast (WI38). Cytosolic and nuclear fractions of WI38 cells, empty vector transfected WI38 (WI38-HPV) and hTERT WI38 cells were submitted to a 2D-DIGE (Two-Dimensional Differential In-Gel Electrophoresis) analysis. Only spots that had a similar abundance in WI38 and WI38-HPV, but were differentially expressed in WI38 hTERT were selected for MS identification. This method directly points to the proteins linked with the hTERT expression. Number of false positive differentially expressed proteins has been excluded by using control WI38-HPV cells. The proteome alteration induced by hTERT WI38 transfection should be taken into account in subsequent use of the cell line for anti-telomerase drugs evaluation.

Results

2D-DIGE experiment shows that 57 spots out of 2246 are significantly differentially expressed in the cytosolic fraction due to hTERT transfection, and 38 were confidently identified. In the nuclear fraction, 44 spots out of 2172 were selected in the differential proteome analysis, and 14 were identified. The results show that, in addition to elongating telomeres, hTERT gene transfection has other physiological roles, among which an enhanced ER capacity and a potent cell protection against apoptosis.

Conclusion

We show that the methodology reduces the complexity of the proteome analysis and highlights proteins implicated in other processes than telomere elongation. hTERT induced proteome changes suggest that telomerase expression enhances natural cell repair mechanisms and stress resistance probably required for long term resistance of immortalized cells. Thus, hTERT transfected cells can not be only consider as an immortal equivalent to parental cells but also as cells which are over-resistant to stresses. These findings are the prerequisite for any larger proteomics aiming to evaluate anti-telomerase drugs proteome alteration and thus therapeutics induced cell reactions.

Ultrastructure of zebrafish dorsal aortic cells

Expression of vascular smooth muscle cell (VSMC) markers such as serum response factor (SRF) is complicated in zebrafish because of the ill-defined histology of the dorsal aorta and the presence of perivascular pigment. We report the ultrastructure of aortic cells in 7-day, 1-month, and 3-month-old zebrafish and provide clear evidence for the presence of perivascular melanocytes harboring an abundance of melanin. In 7-day-old larvae, endothelial cells (EC) and synthetic mural cells that display little evidence of VSMC differentiation comprise the dorsal aorta. The latter mural cells appear to fully differentiate into VSMC by 1 month of age. In 3-month-old adult zebrafish, EC exhibit greater differentiation as evidenced by the accumulation of electron-dense bodies having a diameter of approximately 200 nm. Adult zebrafish aortae also exhibit at least one clear layer of VSMC with the characteristic array of membrane-associated dense plaques, myofilament bundles, and a basement membrane. Subjacent to VSMC are collagen-producing adventitial fibroblasts and melanocytes. These studies indicate that fully differentiated VSMC occur only after day 7 in zebrafish and that such cells are arranged in at least one lamellar unit circumscribing the endothelium. These findings provide new data about the timing and accumulation of VSMC around the zebrafish aorta, which will be useful in phenotyping mutant zebrafish that exhibit defects in blood circulation.

How to create the vascular tree? (Latest) help from the zebrafish

The cardiovascular system provides oxygen, nutrients and hormones to organs, it directs traffic of metabolites and it maintains tissue homeostasis. It is one of the first organs assembled during vertebrate development and it is essential to life from early stages to adult. For these reasons, the process of vessel formation has being studied for more than a century, but it is only in the late eighties that there has been an explosion of research in the field with the employment of various in vitro and in vivo model systems. The zebrafish (Danio rerio) offers several advantages for in vivo studies; it played a fundamental role in new discoveries and helped to refine our knowledge of the vascular system. This review recapitulates the zebrafish data on vasculogenesis and angiogenesis, including the specification of the haemangioblasts from the mesoderm, their migration to form the vascular cord followed by axial vessels specification, the primary and secondary sprouting of intersomitic vessels, the formation of the lumen, the arterial versus venous specification and patterning. To emphasize the strengths of the zebrafish system in the vascular field, we summarize main tools, such as gene expression and mutagenesis screens, knock down technologies, transgenic lines and imaging, which played a major role in the development of the field and allowed significant discoveries, for instance the recent visualization of the lymphatic system in zebrafish. This information contributes to the prospective of drug discovery to cure human diseases linked to angiogenesis, not last tumours.

CYP26A1 knockout embryonic stem cells exhibit reduced differentiation and growth arrest in response to retinoic acid

CYP26A1, a cytochrome P450 enzyme, metabolizes all-trans-retinoic acid (RA) into polar metabolites, e.g. 4-oxo-RA and 4-OH-RA. To determine if altering RA metabolism affects embryonic stem (ES) cell differentiation, we disrupted both alleles of Cyp26a1 by homologous recombination. CYP26a1(-/-) ES cells had a 11.0+/-3.2-fold higher intracellular RA concentration than Wt ES cells after RA treatment for 48 h. RA-treated CYP26A1(-/-) ES cells exhibited 2-3 fold higher mRNA levels of Hoxa1, a primary RA target gene, than Wt ES cells. Despite increased intracellular RA levels, CYP26a1(-/-) ES cells were more resistant than Wt ES cells to RA-induced proliferation arrest. Transcripts for parietal endodermal differentiation markers, including laminin, J6(Hsp 47), and J31(SPARC, osteonectin) were expressed at lower levels in RA-treated CYP26a1(-/-) ES cells, indicating that the lack of CYP26A1 activity inhibits RA-associated differentiation. Microarray analyses revealed that RA-treated CYP26A1(-/-) ES cells exhibited lower mRNA levels than Wt ES cells for genes involved in differentiation, particularly in neural (Epha4, Pmp22, Nrp1, Gap43, Ndn) and smooth muscle differentiation (Madh3, Nrp1, Tagln Calponin, Caldesmon1). In contrast, genes involved in the stress response (e.g. Tlr2, Stk2, Fcgr2b, Bnip3, Pdk1) were expressed at higher levels in CYP26A1(-/-) than in Wt ES cells without RA. Collectively, our results show that CYP26A1 activity regulates intracellular RA levels, cell proliferation, transcriptional regulation of primary RA target genes, and ES cell differentiation to parietal endoderm.

The H19 non-coding RNA is essential for human tumor growth

Background

Mutations and epigenetic aberrant signaling of growth factors pathways contribute to carcinogenesis. Recent studies reveal that non-coding RNAs are controllers of gene expression. H19 is an imprinted gene that demonstrates maternal monoallelic expression without a protein product; although its expression is shut off in most tissues postnatally, it is re-activated during adult tissue regeneration and tumorigenesis. Moreover, H19 is highly expressed in liver metastasis derived from a range of carcinomas. The objective of this study is to explore the role of H19 in carcinogenesis, and to determine its identification as an anti-tumor target.

Methodology/ Principle Findings

By controlling oxygen pressure during tumor cell growth and H19 expression levels, we investigated the role of H19 expression in vitro and in vivo in hepatocellular (HCC) and bladder carcinoma. Hypoxia upregulates the level of H19 RNA. Ablations of tumorigenicity of HCC and bladder carcinomas in vivo are seen by H19 knockdown which also significantly abrogates anchorage-independent growth after hypoxia recovery, while ectopic H19 expression enhances tumorigenic potential of carcinoma cells in vivo. Knocking-down H19 message in hypoxic stress severely diminishes p57^kip2 induction. We identified a number of potential downstream targets of H19 RNA, including angiogenin and FGF18.

Conclusions

H19 RNA harbors pro-tumorigenic properties, thus the H19 gene behaves as an oncogene and may serve as a potential new target for anti-tumor therapy.

Calponins: adaptable modular regulators of the actin cytoskeleton

Over 20 years ago Katsuhito Takahashi isolated a heat stable, calmodulin and actin binding protein from chicken gizzard smooth muscle. Considered initially as a mainly structural component of the vertebrate smooth muscle contractile machinery, the 34-kDa calcium- and calmodulin-binding troponin T-like protein, calponin quickly appeared to also be involved in a number of regulatory and signal transduction events in the actin cytoskeleton. Calponins regulate actomyosin contraction, and reduce metastatic cell motility and tissue invasion. From these various cellular functions the biological role of calponin is now slowly emerging, namely that of an actin filament-stabilizing molecule that contributes to physiological thin filament turnover rates in different cell types.

Trisomy 19 ependymoma, a newly recognized genetico-histological association, including clear cell ependymoma

Ependymal tumors constitute a clinicopathologically heterogeneous group of brain tumors. They vary in regard to their age at first symptom, localization, morphology and prognosis. Genetic data also suggests heterogeneity. We define a newly recognized subset of ependymal tumors, the trisomy 19 ependymoma. Histologically, they are compact lesions characterized by a rich branched capillary network amongst which tumoral cells are regularly distributed. When containing clear cells they are called clear cell ependymoma. Most trisomy 19 ependymomas are supratentorial WHO grade III tumors of the young. Genetically, they are associated with trisomy 19, and frequently with a deletion of 13q21.31-31.2, three copies of 11q13.3-13.4, and/or deletions on chromosome 9. These altered chromosomal regions are indicative of genes and pathways involved in trisomy 19 ependymoma tumorigenesis. Recognition of this genetico-histological entity allows better understanding and dissection of ependymal tumors.

Loss of smooth muscle calponin results in impaired blood vessel maturation in the tumor-host microenvironment

The interactions between malignant cells and the microenvironment of the local host tissue play a critical role in tumor growth, metastasis and their response to treatment modalities. We investigated the roles of smooth muscle calponin (Cnn1, also called calponin h1 or basic calponin) in the development of tumor vascul ature in vivo by analyzing mutant mice lacking the Cnn1 gene. Here we show that loss of Cnn1 in host mural cells prevents maturation of tumor vasculature. In vitro studies showed that platelet-derived growth factor B-induced vascular smooth muscle migration was downregulated by the Cnn1-deficiency, and forced expression of Cnn1 restored migration. Moreover, destruction of established tumor mass by treatment with an antivascular endothelial growth factor antibody was markedly enhanced in Cnn1-deficient mice. These data, coupled with the knowledge that structural fragility of normal blood vessels is caused by loss of the Cnn1 gene, suggest that Cnn1 plays an important role in the maturation of blood vessels, and may have implications for therapeutic strategies targeting tumor vasculature for treatment of human cancers.