In this study, in a culture of renal epithelial cells, we identified those expressing nestin, a cytoskeletal protein associated with stem/progenitor/activated/proliferating cell states. A mouse expressing GFP under the nestin promoter was used, followed by cell isolation and culture. It is hypothesized that this can be used to assess the stem/progenitor/activated/proliferating cell level in a mixed kidney cell culture. Both nestin-positive and nestin-negative cells were demonstrated to be present in the culture. After visualization, cells were attached to a glass slide with a grid, fixed, and prepared for electron microscopy analysis, with each cell visually identified by light microscopy being analyzed. Electron microscopy revealed tight interactions between nestin-positive and nestin-negative cells. Significant differences in the ultrastructure of nestin-positive and nestin-negative cells were observed. Nestin-positive cells were distinguished by a high ribosome content, indicating high protein-synthesizing activity. In the nestin-GFP-high (sorted) population examined by electron microscopy, vesicle-containing protrusions were frequently observed. These cells could contain multiple nuclei of varying sizes and had a high content of lysosomes. No significant differences in mitochondrial ultrastructure were observed in nestin-positive and -negative cells, although functional characteristics evaluated by the membrane potential probe differed.

Olivetol (5-pentylresorcinol) is a naturally occurring alkylresorcinol whose cellular mechanism remains poorly understood. Here, we show that olivetol induces a non-genotoxic nucleolar DNA damage response (n-DDR) in human cells. Although moderately cytotoxic, olivetol did not cause detectable genomic DNA double-strand breaks. Instead, it triggered γH2AX accumulation at ribosomal DNA (rDNA), recruitment of TOPBP1 to Treacle, nucleolar disorganization, and repression of ribosomal RNA synthesis. Mechanistically, olivetol closely phenocopied hypotonic stress, inducing a rapid and reversible n-DDR associated with antisense RNA polymerase II transcription within the rRNA coding region and accumulation of R-loops, consistent with transcriptional interference between RNA polymerases I and II. Both olivetol and hypotonic stress also produced shared membrane-associated phenotypes, including reduced membrane lipid order, calcium redistribution, and plasma membrane blebbing. Importantly, this non-genotoxic nucleolar response depended on cholesterol-sensitive plasma membrane organization.

ETV6-related thrombocytopenia (ETV6-RT) is an inherited platelet disorder caused by germline ETV6 variants. Despite recent progress, the mechanisms underlying platelet dysfunction in ETV6-RT remain unclear. We investigated 12 patients from six families using functional assays, electron microscopy, quantitative proteomics and cytoskeletal imaging. Most patients exhibited mild-to-moderate thrombocytopenia with variable paediatric bleeding symptoms (median International Society on Thrombosis and Haemostasis Bleeding Assessment Tool 3, range 1-9) but consistently mild bleeding in adulthood (median 0, range 0-1). Ex vivo thrombus formation was reduced independent of platelet count. Electron microscopy revealed defective platelet shape maintenance, characterized by spheroid morphology, reduced Dmax/Dmin ratios and diminished alpha-granule pools. Flow cytometry and single-platelet total internal reflection fluorescence imaging demonstrated largely preserved calcium signalling but impaired activation-dependent shape change, dense-granule release and integrin activation. Proteomics showed reduced alpha-granule and lysosomal proteins alongside imbalanced regulators of actin remodelling and β-tubulin. Phalloidin staining confirmed impaired actin cytoskeletal remodelling with reduced lamellipodia formation, while immunofluorescence revealed abnormal β1-tubulin localization with disrupted marginal bands and reduced lysosome-associated membrane protein 1 (LAMP1) expression. Additionally, granulocyte recruitment and migration within thrombi were impaired, suggesting broader thromboinflammatory defects. These findings suggest that combined disruption of cytoskeletal integrity and granule biogenesis underlies impaired thrombus formation in ETV6-RT, providing mechanistic insight into the haemostatic defects associated with this disorder.

The surface structures of archaeal cells, many of which exist at high temperatures, high salinity and non-physiological pH, are key factors for their adaptation to extreme living conditions. In the haloarchaeon Haloarcula hispanica, we have discovered a thin filamentous surface appendage called tat-fimbriae ("tafi"), which were identified to be composed of three protein subunits, TafA, TafC, and TafE, among which TafA is the major fimbrial subunit. Molecular genetic evidence demonstrates TafA was transported through the twin-arginine translocation pathway (Tat-pathway). Based on protein structure prediction (including AlphaFold 3), tafi exhibits a linear structure: TafC at the tip, TafE acting as an adapter, TafA forming the core filament, and they link the fourth subunit TafF, anchoring tafi to the cell wall. To our knowledge, this is the first case that the Tat-pathway has been linked to the secretion of protein subunits forming prokaryotic filamentous structures.

We investigated the role of the nucleolar protein Treacle in organizing and regulating the nucleolus in human cells. Our results support Treacle’s ability to form liquid-like phase condensates through electrostatic interactions among molecules. The formation of these biomolecular condensates is crucial for segregating nucleolar fibrillar centers from the dense fibrillar component and ensuring high levels of ribosomal RNA (rRNA) gene transcription and accurate rRNA processing. Both the central and C-terminal domains of Treacle are required to form liquid-like condensates. The initiation of phase separation is attributed to the C-terminal domain. The central domain is characterized by repeated stretches of alternatively charged amino acid residues and is vital for condensate stability. Overexpression of mutant forms of Treacle that cannot form liquid-like phase condensates compromises the assembly of fibrillar centers, suppressing rRNA gene transcription and disrupting rRNA processing. These mutant forms also fail to recruit DNA topoisomerase II binding protein 1 (TOPBP1), suppressing the DNA damage response in the nucleolus.

Transmission electron microscopy (TEM) is a unique high-resolution method allowing to study the cell ultrastructure of normal and abnormal cells. One of the factors hindering wider application of TEM for diagnosis is the challenges associated with the collection of a sample that would be both enriched in cells of interest and suitable for TEM. The aim of this study was to develop a method for the purification of megakaryocytes from a bone marrow aspirate using antibodies to megakaryocyte surface antigens immobilized on slides as well as to describe a protocol for preparing such isolated cells for a TEM analysis. The study was approved by the Independent Ethics Committee and the Scientific Council of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology of the Ministry of Healthcare of the Russian Federation. For megakaryocyte purification, monafram (F(ab')2 – a fragment of a murine monoclonal antibody to glycoprotein IIb–IIIa) was adsorbed on a glass slide modified with dimethyldichlorosilane. A suspension of mononuclear cells purified from the bone marrow aspirate using the Histopaque 1077 gradient was incubated with the immobilized antibodies for 2 hours at 4°С with mixing every 20 min. The sample was then washed to remove nonspecifically bound cells, fixed with 2.5% glutaraldehyde, postfixed with 1% osmium tetroxide in water, consecutively dehydrated in 30, 50, 70, 90 and 100% acetone and embedded in a thin 0.3–0.5 mm layer of Epon 812 mixed with acetone at 1:2 and 2:1 ratios. After the polymerization of the first thin Epon 812 layer, a cylinder 8 mm in diameter and 10 mm in height was glued on top of the region with bound cells and was left to polymerize. The polymerized resin was then detached from the glass slide using a scalpel, cut using an ultramicrotome and analyzed using TEM. Using this protocol, we studied bone marrow aspirates of 3 patients with essential thrombocythemia. The donors, patients and/or their legal representatives gave consent to bone marrow aspiration and further biomedical research. The obtained electron photomicrographs show all the characteristic features of megakaryocytes including loose nucleus, granules and cisternae of the demarcation membrane system and are in agreement with corresponding images in the existing literature. The suggested protocol allows to obtain TEM samples enriched in rare blood or bone marrow cells using significantly less time and money on sample preparation and photomicrography. This approach is universal and can be used not only for megakaryocytes but for other cells as well, including erythroid precursors.

Electron microscopy (EM) is one of the most efficient methods for studying the fine structure of cells with a resolution thousands of times higher than that of visible light microscopy. The most advanced implementation of electron microscopy in biology is EM tomography of samples stabilized by freezing without water crystallization (cryoET). By circumventing the drawbacks of chemical fixation and dehydration, this technique allows investigating cellular structures in three dimensions at the molecular level, down to resolving individual proteins and their subdomains. However, the problem of efficient identification and localization of objects of interest has not yet been solved, thus limiting the range of targets to easily recognizable or abundant subcellular components. Labeling techniques provide the only way for locating the subject of investigation in microscopic images. CryoET imposes conflicting demands on the labeling system, including the need to introduce into a living cell the particles composed of substances foreign to the cellular chemistry that have to bind to the molecule of interest without disrupting its vital functions and physiology of the cell. This review examines both established and prospective methods for selective labeling of proteins and subcellular structures aimed to enable their localization in cryoET images.

Duchenne muscular dystrophy is caused by loss of the dystrophin protein. This pathology is accompanied by mitochondrial dysfunction contributing to muscle fiber instability. It is known that mitochondria-targeted in vivo therapy mitigates pathology and improves the quality of life of model animals. In the present work, we applied mitochondrial transplantation therapy (MTT) to correct the pathology in dystrophin-deficient mdx mice. Intramuscular injections of allogeneic mitochondria obtained from healthy animals into the hind limbs of mdx mice alleviated skeletal muscle injury, reduced calcium deposits in muscles and serum creatine kinase levels, and improved the grip strength of the hind limbs and motor activity of recipient mdx mice. We noted normalization of the mitochondrial ultrastructure and sarcoplasmic reticulum/mitochondria interactions in mdx muscles. At the same time, we revealed a decrease in the efficiency of oxidative phosphorylation in the skeletal muscle mitochondria of recipient mdx mice accompanied by a reduction in lipid peroxidation products (MDA products) and reduced calcium overloading. We found no effect of MTT on the expression of mitochondrial signature genes (Drp1, Mfn2, Ppargc1a, Pink1, Parkin) and on the level of mtDNA. Our results show that systemic MTT mitigates the development of destructive processes in the quadriceps muscle of mdx mice.

Platelets are the second most abundant human blood cells. They have an important function to form blood clots at sites of vascular injury to prevent bleeding. Abnormalities of platelet structure can lead to various dysfunctions and life-threatening situations. In some hereditary platelet disorders, morphological examination of platelets with transmission electron microscopy (TEM) may be required. TEM is technically complex, and its use is limited due to the need for expensive equipment and trained personnel. In our study, we assessed the morphometric parameters of platelets obtained from 20 healthy donors using TEM. The study was approved by the Independent Ethics Committee and the Scientific Council of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology.

The formation of specific cellular protrusions, plasma membrane blebs, underlies the amoeboid mode of cell motility, which is characteristic for free-living amoebae and leukocytes, and can also be adopted by stem and tumor cells to bypass unfavorable migration conditions and thus facilitate their long-distance migration. Not all cells are equally prone to bleb formation. We have previously shown that membrane blebbing can be experimentally induced in a subset of HT1080 fibrosarcoma cells, whereas other cells in the same culture under the same conditions retain non-blebbing mesenchymal morphology. Here we show that this heterogeneity is associated with the distribution of vimentin intermediate filaments (VIFs). Using different approaches to alter the VIF organization, we show that blebbing activity is biased toward cell edges lacking abundant VIFs, whereas the VIF-rich regions of the cell periphery exhibit low blebbing activity. This pattern is observed both in interphase fibroblasts, with and without experimentally induced blebbing, and during mitosis-associated blebbing. Moreover, the downregulation of vimentin expression or displacement of VIFs away from the cell periphery promotes blebbing even in cells resistant to bleb-inducing treatments. Thus, we reveal a new important function of VIFs in cell physiology that involves the regulation of non-apoptotic blebbing essential for amoeboid cell migration and mitosis.

The recent advances achieved in microscopy technology have led to a significant breakthrough in biological research. Super-resolution fluorescent microscopy now allows us to visualize subcellular structures down to the pin-pointing of the single molecules in them, while modern electron microscopy has opened new possibilities in the study of protein complexes in their native, intracellular environment at near-atomic resolution. Nonetheless, both fluorescent and electron microscopy have remained beset by their principal shortcomings: the reliance on labeling procedures and severe sample volume limitations, respectively. Soft X-ray microscopy is a candidate method that can compensate for the shortcomings of both technologies by making possible observation of the entirety of the cellular interior without chemical fixation and labeling with an isotropic resolution of 40-70 nm. This will thus bridge the resolution gap between light and electron microscopy (although this gap is being narrowed, it still exists) and resolve the issue of compatibility with the former, and possibly in the near future, the latter methods. This review aims to assess the current state of soft X-ray microscopy and its impact on our understanding of the subcellular organization. It also attempts to look into the future of X-ray microscopy, particularly as relates to its seamless integration into the cell biology toolkit.

Integration of the DNA copy of HIV-1 genome into the cellular genome results in series of damages, repair of which is critical for successful replication of the virus. We have previously demonstrated that the ATM and DNA-PK kinases, normally responsible for repairing double-strand breaks in the cellular DNA, are required to initiate the HIV-1 DNA postintegrational repair, even though integration does not result in DNA double-strand breaks. In this study, we analyzed changes in phosphorylation status of ATM (pSer1981), DNA-PK (pSer2056), and their related kinase ATR (pSer428), as well as their targets: Chk1 (pSer345), Chk2 (pThr68), H2AX (pSer139), and p53 (pSer15) during the HIV-1 DNA postintegrational repair. We have shown that ATM and DNA-PK, but not ATR, undergo autophosphorylation during postintegrational DNA repair and phosphorylate their target proteins Chk2 and H2AX. These data indicate common signaling mechanisms between the double-strand DNA break repair and postintegrational repair of HIV-1 DNA.

Cysteine cathepsins play an important role in tumor development and metastasis. The expression of these enzymes is often increased in many types of tumor cells. Cysteine cathepsins contribute to carcinogenesis through a number of mechanisms, including proteolysis of extracellular matrix and signaling molecules on the cell surface, as well as degradation of transcription factors and disruption of signaling cascades in the cell nucleus. Distinct oncogenic functions have been reported for several members of the cysteine cathepsin family in various types of cancer, but a comparative study of all eleven cysteine cathepsins in one experimental model is still missing. In this work, we assessed and compared the expression, localization, and maturation of all eleven cysteine cathepsins in embryonic kidney cells HEK293 and kidney cancer cell lines 769-P and A-498. We found that the expression of cathepsins V, B, Z, L, and S was 3- to 9-fold higher in kidney tumor cells than in embryonic cells. We also showed that all cysteine cathepsins were present in varying amounts in the nucleus of both embryonic and tumor cells. Notably, more than half of the cathepsin Z or K and over 88% of cathepsin F were localized in tumor cell nuclei. Moreover, mature forms of cysteine cathepsins were more prevalent in tumor cells than in embryonic cells. These results can be further used to develop novel diagnostic tools and may assist in the investigation of cysteine cathepsins as potential therapeutic targets.

The work shows the effect of the metabolic modulator uridine on the functioning and ultrastructure of heart mitochondria in dystrophin-deficient mdx mice. Intraperitoneal administration of uridine (30 mg/kg/day for 28 days) improved K + transport and increased its content in the heart mitochondria of mdx mice to the level of wild-type animals. This was accompanied by a significant decrease in the level of malondialdehyde and an increase in the number of mitochondria in the heart of mdx mice. At the same time, uridine did not affect the hyperfunctionality of mitochondria in mdx mice, which manifested in an increase in the calcium retention capacity. Nevertheless, we noted that uridine causes a significant decrease in the level of fibrosis in the heart of mdx mice, which attested to a positive effect of therapy.

Liquid-liquid phase separation (LLPS) and liquid-solid phase transition (LSPT) of amyloidogenic proteins are now being intensively studied as a potentially widespread mechanism of pathological amyloids formation. However, the possibility and importance of such a mechanism in living systems is still questionable. Here, we investigated the possibility of such LSPT for a series of yeast prion proteins-based constructs overproduced in yeast cells lacking any pre-existing amyloid template. By combining fluorescence and electron microscopy with biochemical and genetic approaches, we have shown that three such constructs (containing the prion domains (PDs) of either Sup35, Rnq1 or Mot3 proteins) form amyloid fibrils via the intermediate stage of liquid-like condensates, that age over time into the more solid-like hydrogels and amyloid bodies. In turn, LSPT of these constructs triggers prion conversion of the corresponding wild-type protein. Two other constructs studied (Ure2- and Sap30-based) are unable to phase separate in vivo and their amyloidogenesis is therefore strongly suppressed. Using PrK-resistant amyloid core mapping, we showed that Sup35PD amyloids formed via LSPT have a different molecular architecture compared to those formed via amyloid cross-seeding. Finally, we showed that physiological LLPS of wild-type Sup35 protein can increase its prion conversion in yeast.

An 11-year-old previously healthy girl presented with acute cerebral symptoms in the form of headache and vomiting two to three times a day, bringing relief. MRI of the brain revealed a pathological cystic formation in the left frontoparietal region, of an oval shape with clear, partly uneven outlines and a total size of 35 × 44 × 31 mm, intensively accumulating the contrast agent along the periphery. The lesion exerted a pronounced mass effect, displacing the median structures to the right by 9 mm and squeezing the left lateral ventricle (Figure 1). The patient underwent gross total resection. MRI of the brain and spinal cord showed no metastatic spread of the tumor. Cytological examination of the cerebrospinal fluid revealed no malignant cells. The patient received proton therapy on the resected tumor bed to a total focal dose of 59.4 Gy. Follow-up MRI and 11C-methionine PET/CT scans verified a remission of the main disease, lasting 1.6 years (Box 1). Access at https://isn-slidearchive.org/?col=ISN&fol=Archive&file=BPA-22-06-167.svs Morphological examination revealed a malignant tumor composed of ovoid cells with abundant eosinophilic cytoplasm, forming perivascular pseudorosettes and suggesting a differential diagnosis between ependymoma and astroblastoma. The tumor showed high mitotic activity (up to 5 mitotic figures in 10 visual fields at magnification 400×), microvascular proliferation and necrosis, Figure 2A. Immunohistochemically, the tumor cells tested positive for GFAP, S100, dot-like EMA, focal Synaptophysin and preserved INI1 expression, Figure 2B. Single nuclei were positive for Olig2. Immunohistochemical tests for Chromogranin A, Myelin Basic Protein, Neurofilament, Desmin, Myogenin, and MyoD1 were negative. The Ki67 proliferation index reached 20%. The morphological and immunohistochemical findings suggested a diagnosis of anaplastic ependymoma. The putative diagnosis of supratentorial ependymoma was questioned by genetic examination of the tumor tissue, which identified no ZFTA::RELA or YAP1::MAMLD1 fusions by PCR. High-throughput genomic sequencing revealed no mutations with established clinical or diagnostic significance in H3F3A, BRAF, IDH1/2, TP53, PDGFRA, TERT, or CDKN2A/B. DNA methylation profiling was thereafter performed, but results were of intermediate confidence; the tumor was classified as Neuroepithelial Tumor, PATZ1 fusion-positive with borderline score (0.79052) according to the DKFZ Brain Tumor Classifier version v12.5. The highly recurrent MN1::PATZ1 fusion was subsequently revealed by RNA sequencing (TruSeq RNA exome, Illumina), Figure 2D. The formation of the chimeric oncogene was related to copy number variations (chromothripsis) on Chromosome 22. Given the light microscopic appearance suggestive of ependymal differentiation, ultrastructural studies were performed. Transmission electron microscopy revealed loose arrangement of the cells in the abundant matrix containing dense collagen fibrils (Figure 2C). Even in hypercellular regions corresponding to perivascular pseudorosettes by light microscopy, cell-to-cell contacts/junctions were not observed. Lumina, cilia, and microvilli typical of ependymal differentiation were not present. Unusual neoplasm with glial (?) differentiation, harboring MN1::PATZ1 fusion, NEC. Neuroepithelial tumors PATZ1 fusion-positive (NET-PATZ1) are extremely rare, recently recognized, predominantly pediatric CNS tumors. Histologically, these tumors exhibit hypercellularity, rounded or spindle cell morphologies, variable nuclear shapes and eosinophilic cytoplasm. The mitotic activity is typically moderate and occasionally high. The majority of NET-PATZ1 present with endothelial proliferation and about one-third of them show pronounced necrosis recognized by formation of the perivascular astroblastoma-like pseudorosettes. Despite the range of histopathology, a common DNA methylation signature helps to identify NET-PATZ1 [1]. Chromosomal rearrangements involving PATZ1 are highly specific for NET-PATZ1. The 5′-partner genes in PATZ1 rearranged neoplasms (EWSR1 or MN1), which encode the transcription activation domain in the emerging chimeric oncoprotein, are also present in astroblastoma (MN1::BEND2, less frequently EWSR1::BEND2) and intracranial myxoid mesenchymal tumors with FET-CREB fusions (EWSR1::ATF1, EWSR1::CREB1, or EWSR1::CREM) [1, 2]. In contrast, the 3′-partner genes are disease-specific: BEND2 fusions are found in astroblastoma, whereas PATZ1 fusions act as oncogenic drivers in NET-PATZ1 regardless of the 5′-fusion partner. Identical PATZ1 fusions have been found in individual cases of extracranial spindle and round cell sarcomas, which may show variable coexpression of myogenic and neurogenic markers (S100, SOX10, and GFAP). Although PATZ1-fusion positive CNS and extra-CNS tumors may share common histopathological and immunohistochemical features, the cellular origin of NET-PATZ1 remains uncertain, wavering between glioneuronal and mesenchymal [2]. In our case, ultrastructural investigation revealed the absence of ependymal submicroscopic features and in addition showed tumor cells loosely embedded in a collagenous stroma, more typical of mesenchymal neoplasms, however myogenic immunohistochemical markers were negative. On the basis of the layered diagnostic information complying with WHO CNS5, involving high-throughput molecular technologies apart from the morphological examination, the primary diagnosis of anaplastic ependymoma in the studied clinical case was refined. At the time the integrated diagnosis of this unusual and puzzling case was completed, the patient had commenced radiotherapy in accordance with the primary diagnosis of anaplastic ependymoma. Given the limited information regarding the long-term prognosis of NET-PATZ1 tumors, it was decided to proceed with complete radiotherapy to the total focal dose of 59.4 Gy. Transmission electron microscopy studies were performed on the equipment supported by Nikon Center of Excellence at Belozersky Institute of Physico-Chemical Biology and Lomonosov Moscow State University Development program (PNR 5.13). The study was supported by Foundation for support and development in the field of Pediatric Hematology, Oncology and Immunology "Science for Children." Transmission electron microscopy investigations were supported by Russian Science Foundation grant 21-75-00109. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The Independent Ethics Committee and the Scientific Council of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology approved the study. Written voluntary consent to the patient participation in the study was obtained from legal representative. The authors confirm that the data supporting the findings of this study are available within the article. Raw data that support the findings of this study are available from the corresponding author, upon reasonable request (see Box 1).

SUMMARY In present study, we describe “ ta t- fi mbriae (tafi)” – a novel type of archaeal surface appendages isolated from haloarchaeon Haloarcula hispanica . These fi lamental structures are unique because they are formed of protein subunits secreted through the t win- a rginine translocation pathway (Tat-pathway), in contrast to well-known archaeal surface filamentous structures secreted by the general secretory pathway (Sec-pathway). No cases of the role of Tat-pathway in the assembly of archaeal and bacterial filamentous structures have been described to date. “Tafi” are the first example of such structures. The precursor of the major tafi protein subunit TafA contains the N-terminal signal peptide carrying a twin-arginine consensus motif and fimbria-forming mature TafA lacks this signal peptide. We analyzed the gene neighborhood of the tafA homologues in the known haloarchaeal genomes and found a conservative cluster of seven associated genes tafA, B, C, D, E, F, G . We assume that all of them take part in the tafi synthesis. TafC and TafE proteins, whose precursor sequences also contain twin-arginine motifs, were detected as minor components of tafi. TafE protein is structurally similar to TafA, while TafC contains a TafA-like N-terminal domain and a C-terminal “laminin G-like” domain capable of functioning as an adhesin. TafD is annotated as a signal peptidase I. The functions of TafB, TafF and TafG are not known yet. This study demonstrated that Δ tafA and Δ tafD deletion mutant strains synthesized archaella and not tafi, and only tafi were detected in Δ arlK (gene of common archaellin/pilin signal peptidase) deletion strain. It was shown that the expression of complete Har. hispanica taf -gene cluster in a heterologous host Haloferax volcanii that does not have similar genes leads to synthesis of recombinant tafi structures similar to the native ones. The tafi function remains elusive, but our preliminary data suggest that these structures may be involved in cell adhesion to different surfaces or substrates.

Dystrophin-deficient muscular dystrophy (Duchenne dystrophy) is characterized by impaired ion homeostasis, in which mitochondria play an important role. In the present work, using a model of dystrophin-deficient mdx mice, we revealed decrease in the efficiency of potassium ion transport and total content of this ion in the heart mitochondria. We evaluated the effect of chronic administration of the benzimidazole derivative NS1619, which is an activator of the large-conductance Ca 2+ -dependent K + channel (mitoBK Ca ), on the structure and function of organelles and the state of the heart muscle. It was shown that NS1619 improves K + transport and increases content of the ion in the heart mitochondria of mdx mice, but this is not associated with the changes in the level of mitoBK Ca protein and expression of the gene encoding this protein. The effect of NS1619 was accompanied by the decrease in the intensity of oxidative stress, assessed by the level of lipid peroxidation products (MDA products), and normalization of the mitochondrial ultrastructure in the heart of mdx mice. In addition, we found positive changes in the tissue manifested by the decrease in the level of fibrosis in the heart of dystrophin-deficient animals treated with NS1619. It was noted that NS1619 had no significant effect on the structure and function of heart mitochondria in the wild-type animals. The paper discusses mechanisms of influence of NS1619 on the function of mouse heart mitochondria in Duchenne muscular dystrophy and prospects for applying this approach to correct pathology.

This article discusses the role of electron microscopy in the diagnosis and study of morphological changes that cause platelet structural abnormalities in a variety of congenital diseases. Morphological abnormalities can be divided into the abnormalities of the platelet cytoskeleton, of alpha and dense granules, and membrane abnormalities. Our paper describes ultrastructural platelet defects in Wiskott–Aldrich syndrome, MYH9-associated syndromes, gray platelet syndrome, Hermansky–Pudlak syndrome, Paris–Trousseau syndrome, Chediak–Higashi syndrome.

Actin cytoskeleton is an essential component of living cells and plays a decisive role in many cellular processes. In mammals, β- and γ-actin are cytoplasmic actin isoforms in non-muscle cells. Despite minor differences in the amino acid sequence, β- and γ-actin localize in different cell structures and perform different functions. While cytoplasmic β-actin is involved in many intracellular processes including cell contraction, γ-actin is responsible for cell mobility and promotes tumor transformation. Numerous studies demonstrate that β- and γ-actin are spatially separated in the cytoplasm of fibroblasts and epithelial cells; this separation is functionally determined. The spatial location of β/γ-actin in endothelial cells is still a subject for discussion. Using super-resolution microscopy, we investigated the β/γ-actin colocalization in endotheliocytes and showed that the β/γ-actin colocalization degree varies widely between different parts of the marginal regions and near the cell nucleus. In the basal cytoplasm, β-actin predominates, while the ratio of isoforms evens out as it moves to the apical cytoplasm. Thus, our colocalization analysis suggests that β- and γ-actin are segregated in the endotheliocyte cytoplasm. The segregation is greatly enhanced during cell lamella activation in the nocodazole-induced endothelial barrier dysfunction, reflecting a different functional role of cytoplasmic actin isoforms in endothelial cells.