Unpaired data training enables super-resolution confocal microscopy from low-resolution acquisitions.

Supervised deep-learning models have enabled super-resolution imaging in several microscopic imaging modalities, increasing the spatial lateral bandwidth of the original input images beyond the diffraction limit. Despite their success, their practical application poses several challenges in terms of the amount of training data and its quality, requiring the experimental acquisition of large, paired databases to generate an accurate generalized model whose performance remains invariant to unseen data. Cycle-consistent generative adversarial networks (cycleGANs) are unsupervised models for image-to-image translation tasks that are trained on unpaired datasets. This paper introduces a cycleGAN framework specifically designed to increase the lateral resolution limit in confocal microscopy by training a cycleGAN model using low- and high-resolution unpaired confocal images of human glioblastoma cells. Training and testing performances of the cycleGAN model have been assessed by measuring specific metrics such as background standard deviation, peak-to-noise ratio, and a customized frequency content measure. Our cycleGAN model has been evaluated in terms of image fidelity and resolution improvement using a paired dataset, showing superior performance than other reported methods. This work highlights the efficacy and promise of cycleGAN models in tackling super-resolution microscopic imaging without paired training, paving the path for turning home-built low-resolution microscopic systems into low-cost super-resolution instruments by means of unsupervised deep learning.

Porous Nano-Fiber Structure of Modified Electrospun Chitosan GBR Membranes Improve Osteoblast Calcium Phosphate Deposition in Osteoblast-Fibroblast Co-Cultures.

Desirable characteristics of electrospun chitosan membranes (ESCM) for guided bone regeneration are their nanofiber structure that mimics the extracellular fiber matrix and porosity for the exchange of signals between bone and soft tissue compartments. However, ESCM are susceptible to swelling and loss of nanofiber and porous structure in physiological environments. A novel post-electrospinning method using di-tert-butyl dicarbonate (tBOC) prevents swelling and loss of nanofibrous structure better than sodium carbonate treatments. This study aimed to evaluate the hypothesis that retention of nanofiber morphology and high porosity of tBOC-modified ESCM (tBOC-ESCM) would support more bone mineralization in osteoblast-fibroblast co-cultures compared to Na2CO3 treated membranes (Na2CO3-ESCM) and solution-cast chitosan solid films (CM-film). The results showed that only the tBOC-ESCM retained the nanofibrous structure and had approximately 14 times more pore volume than Na2CO3-ESCM and thousands of times more pore volume than CM-films, respectively. In co-cultures, the tBOC-ESCM resulted in a significantly greater calcium-phosphate deposition by osteoblasts than either the Na2CO3-ESCM or CM-film (p < 0.05). This work supports the study hypothesis that tBOC-ESCM with nanofiber structure and high porosity promotes the exchange of signals between osteoblasts and fibroblasts, leading to improved mineralization in vitro and thus potentially improved bone healing and regeneration in guided bone regeneration applications.

TEM study of chronic alcoholism effects on early carcinogenesis by probing the nanoscale structural alterations of cell nuclei.

Nanoscale structural alteration in the nuclei of cells with the progression of carcinogenesis is due to the rearrangements of the basic building blocks in the cell such as DNA, RNA, lipids, etc. Although epigenetic modifications underlie the development of cancer, exposure to carcinogenic chemicals such as alcohol also enhances the development of cancer. We report the effects of chronic alcoholism on early-carcinogenesis based on changes in the degree of nanoscale structural alterations (L d) in nuclei. For this, transmission electron microscopy (TEM) imaging of the nuclei of colonic cells is performed for the following four mouse models: control mice; chronic alcoholic mice treated with ethanol (i.e., EtOH mice); mice treated with colonic carcinogen azoxymethane (AOM) and dextran sulfate sodium (DSS) that induced colitis (i.e., AOM + DSS mice); and chronic alcoholic or EtOH treated mice, together with AOM and DSS treatment (i.e., AOM + DSS + EtOH mice). The disordered optical lattices are constructed from their respective TEM images of thin colonic cell nuclei and the L d values are calculated using the inverse participation ratio (IPR) technique from the spatially localized eigenfunctions of these lattices. Results show no significant difference in the average L d value of the colon cell nuclei of alcohol treated mice relative to its control [i.e., L d(C) ∼ L d(EtOH)]; however, an increase in the L d value of alcohol treated precancerous cells [i.e., L d(AOM + DSS + EtOH) > L d(AOM + DSS)], indicating that alcohol accelerates the early carcinogenic process.

Enhanced neurite outgrowth on electrically conductive carbon aerogel substrates in the presence of an external electric field.

Previous works from our laboratory have firmly established that aerogels are a suitable substrate to elicit accelerated neurite extension. On non-conducting aerogels, in the presence of an externally-applied DC bias, neurons extended neurites which were preferentially aligned towards the anode. In this investigation, we sought to determine whether electrically-conductive carbon aerogels elicited a more robust alignment of neurites toward the anode than non-conductive aerogels due to the capacity of conductive aerogels to sustain a current, thereby providing a direct interface between neurons and the external electrical stimulus. To determine if this was the case, we plated PC12 neuronal cells on electrically conductive carbon aerolges derived from acetic acid-catalized resorcinol formaldehyde aerogels (ARF-CA) and subjected them to an external electric field. The voltages applied at the electrodes of the custom-built electro-stimulation chamber were 0 V, 15 V, and 30 V. For each voltage, the directionality and length of the neurites extended by PC12 cells were determined and compared to those observed when PC12 cells were plated on non-conductive aerogels subjected to the same voltage. The results show that the directionality of neurite extension was similar between conductive and non-conductive aerogels. A higher neurite length difference was observed on conductive aerogels with increasing voltage, 43% and 106% for 0-15 V and 0-30 V respectively, compared to non-conductive aerogels, 12% and 20%. These findings indicate that conductive carbon aerogels have a greater potential as scaffolds for nerve regeneration than non-conductive ones.

Light localization properties of weakly disordered optical media using confocal microscopy: application to cancer detection.

We have developed a novel technique to quantify submicron scale mass density fluctuations in weakly disordered heterogeneous optical media using confocal fluorescence microscopy. Our method is based on the numerical evaluation of the light localization properties of an 'optical lattice' constructed from the pixel intensity distributions of images obtained with confocal fluorescence microscopy. Here we demonstrate that the technique reveals differences in the mass density fluctuations of the fluorescently labeled molecules between normal and cancer cells, and that it has the potential to quantify the degree of malignancy of cancer cells. Potential applications of the technique to other disease situations or characterizing disordered samples are also discussed.

Actinin-4 in keratinocytes regulates motility via an effect on lamellipodia stability and matrix adhesions.

During wound repair, epidermal cells at the edge of an injury establish front-rear polarity through orchestrated changes in their cytoskeleton and adhesion structures. The polarity and directed migration of such cells is determined by the assembly, extension, and stabilization of a lamellipodium. Actinin-4 associates with lamellipodia and has been implicated in regulating lamellipodial structure, function and assembly. To study the functions of actinin-4 in human keratinocytes, we used shRNA to generate knockdown cells and compared their motility behavior and matrix adhesion assembly to scrambled shRNA treated control keratinocytes. Actinin-4 knockdown keratinocytes lack polarity, assemble multiple lamellipodia with a 2× increased area over controls, display reduced activity of the actin remodeling protein cofilin, and fail to migrate in a directional manner. This motility defect is rescued by plating knockdown cells on preformed laminin-332 matrix. In actinin-4-knockdown keratinocytes, focal contact area is increased by 25%, and hemidesmosome proteins are mislocalized. Specifically, α6ß4 integrin localizes to large lamellipodial extensions, displays reduced dynamics, and fails to recruit its bullous pemphigoid antigen binding partners. Together, our data indicate a role for actinin-4 in regulating the steering mechanism of keratinocytes via profound effects on their matrix adhesion sites.

Regulation of microtubule nucleation in mouse bone marrow-derived mast cells by ARF GTPase-activating protein GIT2.

Aggregation of high-affinity IgE receptors (FcϵRIs) on granulated mast cells triggers signaling pathways leading to a calcium response and release of inflammatory mediators from secretory granules. While microtubules play a role in the degranulation process, the complex molecular mechanisms regulating microtubule remodeling in activated mast cells are only partially understood. Here, we demonstrate that the activation of bone marrow mast cells induced by FcϵRI aggregation increases centrosomal microtubule nucleation, with G protein-coupled receptor kinase-interacting protein 2 (GIT2) playing a vital role in this process. Both endogenous and exogenous GIT2 were associated with centrosomes and γ-tubulin complex proteins. Depletion of GIT2 enhanced centrosomal microtubule nucleation, and phenotypic rescue experiments revealed that GIT2, unlike GIT1, acts as a negative regulator of microtubule nucleation in mast cells. GIT2 also participated in the regulation of antigen-induced degranulation and chemotaxis. Further experiments showed that phosphorylation affected the centrosomal localization of GIT2 and that during antigen-induced activation, GIT2 was phosphorylated by conventional protein kinase C, which promoted microtubule nucleation. We propose that GIT2 is a novel regulator of microtubule organization in activated mast cells by modulating centrosomal microtubule nucleation.

A Self-Controlled and Self-Healing Model of Bacterial Cells.

A new kind of self-assembly model, morphogenetic (M) systems, assembles spatial units into larger structures through local interactions of simpler components and enables discovery of new principles for cellular membrane assembly, development, and its interface function. The model is based on interactions among three kinds of constitutive objects such as tiles and protein-like elements in discrete time and continuous 3D space. It was motivated by achieving a balance between three conflicting goals: biological, physical-chemical, and computational realism. A recent example is a unified model of morphogenesis of a single biological cell, its membrane and cytoskeleton formation, and finally, its self-reproduction. Here, a family of dynamic M systems (Mbac) is described with similar characteristics, modeling the process of bacterial cell formation and division that exhibits bacterial behaviors of living cells at the macro-level (including cell growth that is self-controlled and sensitive to the presence/absence of nutrients transported through membranes), as well as self-healing properties. Remarkably, it consists of only 20 or so developmental rules. Furthermore, since the model exhibits membrane formation and septic mitosis, it affords more rigorous definitions of concepts such as injury and self-healing that enable quantitative analyses of these kinds of properties. Mbac shows that self-assembly and interactions of living organisms with their environments and membrane interfaces are critical for self-healing, and that these properties can be defined and quantified more rigorously and precisely, despite their complexity.

Optimal structural and physical properties of aerogels for promoting robust neurite extension in vitro.

Cell behaviour is influenced by external factors including the physical properties of the substrate such as its surface topography and stiffness. Recent studies have demonstrated the potential of aerogels as biomaterials and specifically as neural scaffolds. The 3-D structure inherent to aerogels offers an advantage over other biocompatible substrates which lack the dimensionality needed to mimic the in vivo topography of tissues. Here, we used a variety of aerogel types to correlate the extension of neurites by neuronal cells with surface roughness ranging from 0 to 3 µm and stiffness 10 kPa-4 MPa. This investigation reveals that the optimal surface features for neurite extension are a surface roughness of 0.5 µm and a Young's modulus between 1 and 3.5 MPa. The significance of these findings to optimize materials for nerve repair is discussed.

Nematic Templated Complex Nanofiber Structures by Projection Display.

Oriented arrays of nanofibers are ubiquitous in nature and have been widely used in recreation of the biological functions such as bone and muscle tissue regenerations. However, it remains a challenge to produce nanofiber arrays with a complex organization by using current fabrication techniques such as electrospinning and extrusion. In this work, we propose a method to fabricate the complex organization of nanofiber structures templated by a spatially varying ordered liquid crystal host, which follows the pattern produced by a maskless projection display system. By programming the synchronization of the rotated polarizer and projected segments with different shapes, various configurations of nanofiber organization ranging from a single to two-dimensional lattice of arbitrary topological defects are created in a deterministic manner. The nanofiber arrays can effectively guide and promote neurite outgrowth. The application of nanofibers with arced profiles and topological defects on neural tissue organization is also demonstrated. This finding, combined with the versatility and programmability of nanofiber structures, suggests that they will help solve challenges in nerve repair, neural regeneration, and other related tissue engineering fields.

Na+/H+ exchangers and RhoA regulate acidic extracellular pH-induced lysosome trafficking in prostate cancer cells.

Acidic extracellular pH (pHe) is a common feature of the tumor microenvironment and has been implicated in tumor invasion through the induction of protease secretion.Since lysosomes constitute the major storehouse of cellular proteases, the trafficking of lysosomes to the cell periphery may be required in order to secrete proteases. We demonstrate that a pHe of 6.4-6.8 induced the trafficking of lysosomes to membrane protrusions in the cell periphery. This trafficking event depended upon the PI3K pathway, the GTPase RhoA and sodium-proton exchange activity, resulting in lysosomal exocytosis. Acidic pHe induced a cytoplasmic acidification (although cytoplasmic acidification was not sufficient for acidic pHe-induced lysosome trafficking and exocytosis) and inhibition of NHE activity with the amiloride derivative, EIPA or the anti-diabetic agent troglitazone prevented lysosome trafficking to the cell periphery. Interestingly, using the more specific NHE1 and NHE3 inhibitors, cariporide and s3226 respectively, we show that multiple NHE isoforms are involved in acidic pHe-induced lysosome trafficking and exocytosis. Moreover, in cells expressing NHE1 shRNA, although basal NHE activity was decreased, lysosomes still underwent acidic pHe-induced trafficking,suggesting compensation by other NHE family members.Together these data implicate proton exchangers, especially NHE1 and NHE3, in acidic pHe-induced lysosome trafficking and exocytosis.

Alpha-actinin 1 and alpha-actinin 4: contrasting roles in the survival, motility, and RhoA signaling of astrocytoma cells.

Alpha-actinin is a prominent actin filament associated protein for which different isoforms exist. Here, we have examined whether the two highly homologous non-muscle alpha-actinin isoforms 1 and 4 exhibit functional differences in astrocytoma cells. The protein levels of these isoforms were differentially regulated during the development and progression of astrocytomas, as alpha-actinin 1 was higher in astrocytomas compared to normal brains whereas alpha-actinin 4 was elevated in high-grade astrocytomas compared to normal brains and low grade astrocytomas. RNAi demonstrated contrasted contributions of alpha-actinin 1 and 4 to the malignant behavior of U-373, U-87 and A172 astrocytoma cells. While alpha-actinin 1 appeared to favor the expansion of U-373, U-87 and A172 astrocytoma cell populations, alpha-actinin 4 played this role only for U-373 cells. On the other hand, downregulation of alpha-actinin 4, but not 1, reduced cell motility, adhesion, cortical actin, and RhoA levels. Finally, in the three astrocytoma cell lines examined, alpha-actinin 1 and 4 had contrasted biochemical properties as alpha-actinin 4 was significantly more abundant in the actin cytoskeleton than alpha-actinin 1. Collectively, these findings suggest that alpha-actinin 1 and 4 are differentially regulated during the development and progression of astrocytomas because each of these isoforms uniquely contributes to distinct malignant properties of astrocytoma cells.

Cutaneous Effects of In Utero and Lactational Exposure of C57BL/6J Mice to 2,3,7,8-Tetrachlorodibenzo-p-dioxin.

To determine the cutaneous effects of in utero and lactational exposure to the AHR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), pregnant C57BL/6J mice were exposed by gavage to a vehicle or 5 µg TCDD/kg body weight at embryonic day 12 and epidermal barrier formation and function were studied in their offspring from postnatal day 1 (P1) through adulthood. TCDD-exposed pups were born with acanthosis. This effect was AHR-dependent and subsided by P6 with no evidence of subsequent inflammatory dermatitis. The challenge of adult mice with MC903 showed similar inflammatory responses in control and treated animals, indicating no long-term immunosuppression to this chemical. Chloracne-like sebaceous gland hypoplasia and cyst formation were observed in TCDD-exposed P21 mice, with concomitant microbiome dysbiosis. These effects were reversed by P35. CYP1A1 and CYP1B1 expression in the skin was increased in the exposed mice until P21, then declined. Both CYP proteins co-localized with LRIG1-expressing progenitor cells at the infundibulum. CYP1B1 protein also co-localized with a second stem cell niche in the isthmus. These results indicate that this exposure to TCDD causes a chloracne-like effect without inflammation. Transient activation of the AhR, due to the shorter half-life of TCDD in mice, likely contributes to the reversibility of these effects.

Expression profiles of nestin and synemin in reactive astrocytes and Müller cells following retinal injury: a comparison with glial fibrillar acidic protein and vimentin.

PURPOSE: To examine the expression patterns of the intermediate filament (IF) proteins nestin and synemin following retinal injury. METHODS: Wide-scale retinal injuries were created by experimental retinal detachment of 1, 3, 7, or 30 days' duration. Injuries were induced in the right eyes of Long Evans rats, while the left eyes served as internal controls. Vibratome sections of control and injured retinas were labeled with fluorescent probes using a combination of anti-glial fibrillary acidic protein, -vimentin, -nestin, -synemin, -bromodeoxyuridine, and the lectin probe, isolectin B4. Additionally, antibody specificity, as well as protein and mRNA levels of nestin and synemin were determined and quantified using standard western blotting and real time polymerase chain reaction (RT-PCR) techniques. RESULTS: Immunocytochemistry showed increased Müller cell labeling at 1, 3, and 7 days post injury for all four IFs, although the relative levels of nestin expression varied dramatically between individual Müller cells. Nestin was consistently observed in the foremost processes of those Müller cells that grew into the subretinal space, forming glial scars. Elevated levels of nestin expression were also observed in bromodeoxyuridine-labeled Müller cells following retinal insult. Quantitative polymerase chain reaction (qPCR) showed a twofold increase in nestin mRNA 1 day after injury, a level maintained at 3 and 7 days. Western blotting using anti-nestin showed a single band at 220 kDa and the intensity of this band increased following injury. Anti-synemin labeling of control retinas revealed faint labeling of astrocytes; this increased after injury, demonstrating an association with blood vessels. Additionally, there was an upregulation of synemin in Müller cells. qPCR and western blotting with anti-synemin showed a continuous increase in both gene and protein expression over time. CONCLUSIONS: Retinal injury induces an upregulation of a complement of four intermediate filament proteins, including synemin and nestin, in Müller cells. The latter provides suggestive support for the concept that these cells may revert to a more developmentally immature state, since these two IF proteins are developmentally regulated and expressed, and thus may serve as cell cycle reentry markers. Nestin and its differential expression patterns with glial fibrillary acidic protein and vimentin networks, as well as its association with proliferating Müller cells and those extending into the subretinal space, suggest a significant role of this protein in glial scar formation and perhaps gliogenesis. Synemin immunopositive astrocytes demonstrate a close relationship to the retinal vasculature, and illustrate a remarkable ability to reorganize their morphology in response to injury. Further examination of the changes in the cytoskeletal signatures of both of these glial cell types may lead to a more comprehensive understanding of mechanisms underway following retinal and other central nervous system injuries.

Mimicking aspects of frontotemporal lobar degeneration and Lou Gehrig's disease in rats via TDP-43 overexpression.

Since the discovery of neuropathological lesions made of TDP-43 and ubiquitin proteins in cases of frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS), there is a burst of effort on finding related familial mutations and developing animal models. We used an adeno-associated virus (AAV) vector for human TDP-43 expression targeted to the substantia nigra (SN) of rats. Though TDP-43 was expressed mainly in neuronal nuclei as expected, it was also expressed in the cytoplasm, and dotted along the plasma membrane of neurons. Cytoplasmic staining was both diffuse and granular, indicative of preinclusion lesions, over 4 weeks. Ubiquitin deposited in the cytoplasm, specifically in the TDP-43 group, and staining for microglia was increased dose-dependently by 1-2 logs in the TDP-43 group, while neurons were selectively obliterated. Neuronal death induced by TDP-43 was pyknotic and apoptotic. TDP-43 gene transfer caused loss of dopaminergic neurons in the SN and their axons in the striatum. Behavioral motor dysfunction resulted after TDP-43 gene transfer that was vector dose-dependent and progressive over time. The cytoplasmic expression, ubiquitination, and neurodegeneration mimicked features of the TDP-43 diseases, and the gliosis, apoptosis, and motor impairment may also be relevant to TDP-43 disease forms involving nigrostriatal degeneration.

Nerve Response to Superelastic Shape Memory Polyurethane Aerogels.

We have previously shown the suitability of aerogels as scaffolds for neuronal cells. Here, we report on the use of superelastic shape memory polyurethane aerogels (SSMPA). SSMPA have a distinctly different stiffness than previously reported aerogels. The soft and deformable nature of SSMPA allowed for radial compression of the aerogel induced by a custom designed apparatus. This radial compression changed the pore diameter and surface roughness (Sa) of SSMPA, while maintaining similar stiffness. Two varieties of SSMPA were used, Mix-14 and Mix-18, with distinctly different pore diameters and Sa. Radial compression led to a decreased pore diameter, which, in turn, decreased the Sa. The use of custom designed apparatus and two types of SSMPA allowed us to examine the influence of stiffness, pore size, and Sa on the extension of processes (neurites) by PC12 neuronal cells. PC12 cells plated on SSMPA with a higher degree of radial compression extended fewer neurites per cell when compared to other groups. However, the average length of the neurites was significantly longer when compared to the unrestricted group and to those extended by cells plated on SSMPA with less radial compression. These results demonstrate that SSMPA with 1.9 µm pore diameter, 1.17 µm Sa, and 203 kPa stiffness provides the optimum combination of physical parameters for nerve regeneration.

Advantages of Fresnel biprism-based digital holographic microscopy in quantitative phase imaging.

SIGNIFICANCE: The hallmarks of digital holographic microscopy (DHM) compared with other quantitative phase imaging (QPI) methods are high speed, accuracy, spatial resolution, temporal stability, and polarization-sensitivity (PS) capability. The above features make DHM suitable for real-time quantitative PS phase imaging in a broad number of biological applications aimed at understanding cell growth and dynamic changes occurring during physiological processes and/or in response to pharmaceutical agents. AIM: The insertion of a Fresnel biprism (FB) in the image space of a light microscope potentially turns any commercial system into a DHM system enabling QPI with the five desired features in QPI simultaneously: high temporal sensitivity, high speed, high accuracy, high spatial resolution, and PS. To the best of our knowledge, this is the first FB-based DHM system providing these five features all together. APPROACH: The performance of the proposed system was calibrated with a benchmark phase object. The PS capability has been verified by imaging human U87 glioblastoma cells. RESULTS: The proposed FB-based DHM system provides accurate phase images with high spatial resolution. The temporal stability of our system is in the order of a few nanometers, enabling live-cell studies. Finally, the distinctive behavior of the cells at different polarization angles (e.g., PS capability) can be observed with our system. CONCLUSIONS: We have presented a method to turn any commercial light microscope with monochromatic illumination into a PS QPI system. The proposed system provides accurate quantitative PS phase images in a new, simple, compact, and cost-effective format, thanks to the low cost (a few hundred dollars) involved in implementing this simple architecture, enabling the use of this QPI technique accessible to most laboratories with standard light microscopes.

Controlled Dynamics of Neural Tumor Cells by Templated Liquid Crystalline Polymer Networks.

The ability to control the alignment and organization of cell populations has great potential for tissue engineering and regenerative medicine. A variety of approaches such as nano/microtopographical patterning, mechanical loading, and nanocomposite synthesis have been developed to engineer scaffolds able to control cellular properties and behaviors. In this work, a patterned liquid crystal polymer network (LCN) film is synthesized by using a nematic liquid crystal template in which the molecular orientations are predesigned by photopatterning technique. Various configurations of polymer networks such as linear and circular patterns are created. When neural tumor cells are plated onto the templated LCN films, the cell alignment, migration, and proliferation are directed in both linear and curvilinear fashions following the pattern of the aligned polymer chains. A complex LCN pattern with zigzag geometry is also fabricated and found to be capable of controlling cell alignment and collective cellular organization. The demonstrated control of cell dynamics and organization by LCN films with various molecular alignments opens new opportunities to design scaffolds to control cultured cell organization in a manner resembling that found in tissues and to develop novel advanced materials for nerve repair, tissue engineering, and regenerative medicine applications.

Intermediate filament protein synemin contributes to the migratory properties of astrocytoma cells by influencing the dynamics of the actin cytoskeleton.

We have shown previously that, in astrocytoma cells, synemin is present at the leading edge, an unusual localization for an intermediate filament (IF) protein. Here, we report that synemin down-regulation with specific small hairpin RNAs (shRNAs) sharply decreased the migration of astrocytoma cells. The presence of synemin at the leading edge also correlated with a high migratory potential, as shown by comparing astrocytoma cells to carcinoma cells without synemin at the leading edge. Synemin-silenced astrocytoma cells were smaller and spread more slowly than controls. In addition, synemin silencing reduced proliferation without increasing apoptosis. The adhesion to substratum and distribution of vinculin in focal contacts of synemin-silenced astrocytoma cells were similar to those of controls. Synemin-silenced cells, however, exhibited a reduction in the amount of filamentous (F) -actin and of alpha-actinin, but not of vinculin, associated with F-actin. Altogether, these results demonstrate that synemin is important for the malignant behavior of astrocytoma cells and that it contributes to the high motility of these cells by modulating the dynamics of alpha-actinin and actin.