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Intermediate filaments were first described in muscle in 1968, and desmin was biochemically identified about 10 years afterwards. Its importance grew after the identification of desminopathies and desmin mutations that cause mostly cardiopathies. Since its characterization until recently, different functions have been attributed to desmin. Here, we use bibliometric tools to evaluate the articles published about desmin and to assess its several putative functions. We identified the most productive authors and the relationships between research groups. We studied the more frequent words among 9734 articles (September 2021) containing "desmin" on the title and abstract, to identify the major research focus. We generated an interactive spreadsheet with the 934 papers that contain "desmin" only on the title that can be used to search and quantify terms in the abstract. We further selected the articles that contained the terms "function" or "role" from the spreadsheet, which we then classified according to type of function, organelle, or tissue involved. Based on the bibliographic analysis, we assess comparatively the putative functions, and we propose an alternative explanation for the desmin function.

Olfactory ensheathing cells (OECs) are specialized glial cells of the olfactory system, believed to play a role in the continuous production of olfactory neurons and ensheathment of their axons. Although OECs are used in therapeutic applications, little is known about the cellular mechanisms underlying their migratory behavior. Recently, we showed that OEC migration is sensitive to ganglioside blockage through A2B5 and Jones antibody in OEC culture. Gangliosides are common components of lipid rafts, where they participate in several cellular mechanisms, including cell migration. Here, we characterized OEC lipid rafts, analyzing the presence of specific proteins and gangliosides that are commonly expressed in motile neural cells, such as young neurons, oligodendrocyte progenitors, and glioma cells. Our results showed that lipid rafts isolated from OECs were enriched in cholesterol, sphingolipids, phosphatidylcholine, caveolin-1, flotillin-1, gangliosides GM1 and 9-O-acetyl GD3, A2B5-recognized gangliosides, CNPase, α-actinin, and β1-integrin. Analysis of the actin cytoskeleton of OECs revealed stress fibers, membrane spikes, ruffled membranes and lamellipodia during cell migration, as well as the distribution of α-actinin in membrane projections. This is the first description of α-actinin and flotillin-1 in lipid rafts isolated from OECs and suggests that, together with β1-integrin and gangliosides, membrane lipid rafts play a role during OEC migration. This study provides new information on the molecular composition of OEC membrane microdomains that can impact on our understanding of the role of OEC lipid rafts under physiological and pathological conditions of the nervous system, including inflammation, hypoxia, aging, neurodegenerative diseases, head trauma, brain tumor, and infection. [ABSTRACT FROM AUTHOR]

The enormous amount of information available in cell biology has created a challenge in selecting the core concepts we should be teaching our undergraduates. One way to define a set of essential core ideas in cell biology is to analyze what a specific cell biology community is teaching their students. Our main objective was to analyze the cell biology content currently being taught in Brazilian universities. We collected the syllabi of cell biology courses from public universities in Brazil and analyzed the frequency of cell biology topics in each course. We also compared the Brazilian data with the contents of a major cell biology textbook. Our analysis showed that while some cell biology topics such as plasma membrane and cytoskeleton was present in ∼100% of the Brazilian curricula analyzed others such as cell signaling and cell differentiation were present in only ∼35%. The average cell biology content taught in the Brazilian universities is quite different from what is presented in the textbook. We discuss several possible explanations for these observations. We also suggest a list with essential cell biology topics for any biological or biomedical undergraduate course. The comparative discussion of cell biology topics presented here could be valuable in other educational contexts. [ABSTRACT FROM AUTHOR]

Actin-based structures play fundamental roles in cellular functions. However it remains controversial how cells cope with the absence of F-actin structures. This report focuses on short- and long-term effects of cytochalasin B (CB) on actin-complexes in fibroblasts and myoblasts. Thirty min of CB treatment dispersed subplasma actin cortices, lamellipodia, ruffled membranes, stress fibers and adhesion plaques into actin patches in fibroblasts and muscle cells. In contrast, 72 hrs CB treatment showed distinct morphological effects. Fibroblasts became giant multinucleated-finger shaped with 5 to 10 protrusions, 3–8 μm in width, and >200 μm in length. They lacked cortical actin, stress fibers, adhesion plaques and ruffled membranes but contained immense lamelliopodia with abnormal adhesion plaque protein complexes. Muscle cells transformed into multinucleated globular-shaped but contained normal I-Z-I and A-bands, indicating that CB did not interfere with the assembly of myofibrils. Within 30 min after CB removal, finger-shaped fibroblasts returned to their original shape and actin-containing structures rapidly reappeared, whereas muscle cells respond slowly to form elongated myotubes following CB washout. The capacity to grow, complete several nuclear cycles, assemble intermediate filaments and microtubules without a morphologically recognizable actin cytoskeleton raises interesting issues related to the role of the actin compartments in eukaryotic cells. [ABSTRACT FROM AUTHOR]

In vitro studies show that cholesterol is essential to myogenesis. We have been using zebrafish to overcome the limitations of the in vitro approach and to study the sub-cellular structures and processes involved during myogenesis. We use simvastatin—a drug widely used to prevent high levels of cholesterol and cardiovascular disease—during zebrafish skeletal muscle formation. Simvastatin is an efficient inhibitor of cholesterol synthesis that has various myotoxic consequences. Here, we employed simvastatin concentrations that cause either mild or severe morphological disturbances to observe changes in the cytoskeleton (intermediate filaments and microfilaments), extracellular matrix and adhesion markers by confocal microscopy. With low-dose simvastatin treatment, laminin was almost normal, and alpha-actinin was reduced in the myofibrils. With high simvastatin doses, laminin and vinculin were reduced and appeared discontinuous along the septa, with almost no myofibrils, and small amounts of desmin accumulating close to the septa. We also analyzed sub-cellular alterations in the embryos by electron microscopy, and demonstrate changes in embryo and somite size, septa shape, and in myofibril structure. These effects could be reversed by the addition of exogenous cholesterol. These results contribute to the understanding of the mechanisms of action of simvastatin in muscle cells in particular, and in the study of myogenesis in general. [ABSTRACT FROM AUTHOR]

To overcome the limitations of in vitro studies, we have been studying myogenesis in situ in zebrafish embryos, at a sub-cellular level. While in previous works we focused on myofibrillogenesis and some aspects of adhesion structures, here we describe in more detail cell adhesion structures and interactions among cytoskeletal components, membrane and extracellular matrix during zebrafish muscle development. We studied the intermediate filaments, and we describe the full range of desmin distribution in zebrafish development, from perinuclear to striated, until its deposition around the intersomite septa of older somites. This adhesion structure, positive for desmin and actin, has not been previously observed in myogenesis in vitro. We also show that actin is initially located in the intersomite septum region whereas it is confined to the myofibrils later on. While actin localization changes during development, the adhesion complex proteins vinculin, paxillin, talin, dystrophin, laminin and fibronectin always appear exclusively at the intersomite septa, and appear to be co-distributed, even though the extracellular proteins accumulates before the intracellular ones. Contrary to the adhesion proteins, that are continuously distributed, desmin and sarcomeric actin form triangular aggregates among the septa and the cytoskeleton. We studied the cytoskeletal linker plectin as well, and we show that it has a distribution similar to desmin and not to actin. We conclude that the in situ adhesion structures differ from their in vitro counterparts, and that the actual zebrafish embryo myogenesis is quite different than that which occurs in in vitro systems. Cell Motil. Cytoskeleton 65: 801-815, 2008. © 2008 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Hepatic stellate cells (HSCs) are intralobular connective tissue cells presenting myofibroblast or lipocyte phenotypes. They participate in the homeostasis of liver extracellular matrix, repair, regeneration and fibrosis under the former phenotype, and control retinol metabolism, storage and release under the latter one. Responding to systemic or local demands, they can convert into the required phenotype with deep modifications of their structures. Using immunofluorescence microscopy and Western blots, we investigated the expression and organisation of actin filaments and of two actin-binding proteins, α-actinin and tropomyosin, in the cloned GRX cell line representative of murine HSCs. GRX cells expressing the myofibroblast phenotype showed typical well-organised actin stress-fibres, anchored at the focal adhesions located at the cell periphery. Retinol treatment induced active reorganisation of the cytoskeleton. The major stress fibres were reduced in length, and frequently formed a polygonal meshwork. Subsequently, they fragmented and generated diffuse or granular actin in the perinuclear area, a thin continuous layer around lipid droplets and, in fully converted lipocytes, a peripheral layer of thin actin fibres. α-Actinin and tropomyosin were present only in lipocytes, co-distributed with actin in a granular form. Since the cytoskeleton reorganisation preceded lipid accumulation, we conclude that the induction of the lipocyte phenotype represents a full reprogramming of cell gene expression and function. We consider that both the lipocyte and the myofibroblast phenotypes should be considered "activated states" of HSCs, each responding to specific physiological or pathological modifications of liver functions. [ABSTRACT FROM AUTHOR]

Hepatic stellate cells are intralobular connective tissue cells expressing the myofibroblast or the lipocyte phenotypes. They participate in homeostasis of the liver extracellular matrix, repair, regeneration, and fibrosis under the former phenotype, and control the retinol metabolism, storage, and release under the latter one. They are heterogeneous in terms of their tissue distribution, function, and expression of cytoskeletal proteins. We have studied the expressions of intermediate filaments in the cloned GRX cell line representative of murine hepatic stellate cells, by immunolabeling, reverse transcription polymerase chain reaction (RT-PCR), immunoprecipitation and Western blots. GRX cells expressed vimentin, desmin, glial fibrillary acidic protein (GFAP), and smooth muscle α actin (SM-αA). Vimentin, desmin, and SM-αA were expressed in all cultures. GFAP showed a heterogeneous intensity of expression and did not form a filamentous cytoskeletal network, showing a distinct punctuate cytoplasmic distribution. When activated by inflammatory mediators, GRX cells increased expression of desmin and GFAP. Retinol-mediated induction of the lipocyte phenotype elicited a strong decrease of intermediate filament protein expression and the collapse of the filamentous structure of the cytoskeleton. Quiescent hepatic stellate precursors can respond to physiologic or pathologic stimuli, expressing activated myofibroblast or lipocyte phenotypes with distinct patterns of cytoskeleton structure, metabolic function, and interaction with the tissue environment.Key words: intermediate filaments, desmin, glial fibrillary acidic protein, GFAP, hepatic stellate cells, liver.Les cellules périsinusoïdales hépatiques sont des cellules conjonctives intralobulaires pouvant prendre la forme de myofibroblastes ou de lipocytes. Sous forme de myofibroblastes, elles participent à la régénération et au développement des fibroses hépatiques; sous forme de lipocytes, elles règlent le métabolisme, le stockage et la libération du rétinol. Elles sont hétérogènes quant à leur distribution tissulaire, leur fonction et leur expression de protéines du cytosquelette. Nous avons étudié l'expression de protéines des filaments intermédiaires dans la lignée cellulaire GRX, représentative de cellules périsinusoïdales hépatiques de souris, par immunomarquage, RT-PCR, immunoprécipitation et transfert Western. Les cellules GRX produisent la vimentine, la desmine, la protéine fibrillaire acide gliale (GFAP) et l'actine α de muscle lisse (SM-αA). La vimentine, la desmine et la SM-αA sont présentes dans toutes les cultures. Le taux d'expression de la GFAP varie. La GFAP ne forme pas de réseaux fibrillaires, mais elle a une distribution ponctuelle dans le cytoplasme. Sous l'influence de médiateurs de l'inflammation, l'expression de la desmine et de la GFAP augmente dans les cellules GRX. L'induction du phénotype lipocytaire par le rétinol est associée à une diminution des filaments intermédiaires et à une désorganisation de leur structure. Les cellules périsinusoïdales hépatiques résidentes peuvent donc répondre à des stimuli physiologiques et pathologiques par des modifications de l'organisation de leur cytosquelette, associées aux modifications de leur fonction métabolique et de leur interaction avec les tissus adjacents.Mots clés : filaments intermédiaires, desmine, protéine fibrillaire acide gliale, GFAP, cellules périsinusoïdales hépatiques, foie.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]