Podocyte infolding glomerulopathy (PIG) is a rare glomerular disease, with case reports and cohort studies lacking clear morphological diagnostic criteria. We aimed to establish transmission electron microscopy (TEM)–based diagnostic criteria for PIG and classify its morphological subtypes. This retrospective nationwide cohort study was conducted by the PIG Working Group of the Japanese Society of Nephrology. Clinical data and TEM findings were collected from patients diagnosed with or suspected of PIG at 69 institutions across Japan between 1991–2025. PIG was defined by TEM as podocyte infolding exceeding half the glomerular basement membrane (GBM) thickness at two or more sites within a single capillary loop or the presence of microspheres or microtubules within the GBM. Cases were classified into morphological subtypes, and their clinical characteristics were analyzed. Among 103 registered cases, 93 met diagnostic criteria. Four morphological subtypes were identified: Type A, primary podocyte infolding without prominent microspheres or microtubules (n = 21); Type B, predominant microspheres (n = 34); Type C, microtubules with or without microspheres (n = 38); and Type D, dense clusters of microspheres (n = 10). Types B and C were more common in younger females and frequently associated with systemic lupus erythematosus (58

Fibroblast growth factor-23 (FGF23) is a bone-derived hormone that promotes urinary phosphate excretion in response to phosphate loading. While essential for phosphate homeostasis, elevated FGF23 increases phosphate concentration in the renal tubular fluid, promoting calcium-phosphate crystal formation and tubular injury. Here we show that bone resorption mobilizes phosphate into the circulation and mimics the pathophysiology of dietary phosphate loading. Enhanced bone resorption, induced by soluble receptor activator of NF-κB ligand (sRANKL) administration or microgravity exposure on the International Space Station, increased circulating FGF23 levels and caused renal tubular injury in mice. Pre-treatment with bisphosphonate, an inducer of osteoclast apoptosis, prevented sRANKL-induced increases in FGF23 and tubular damage. These findings suggest that bone mineral loss may contribute to renal tubular injury in clinical settings, including immobilization, osteoporosis, and chronic kidney disease–mineral bone disorder. Enhanced bone resorption induced by sRANKL or microgravity releases phosphate into the circulation and causes crystal-induced tubular injury in mice, identifying bone-derived phosphate as a driver of kidney damage.

The molecular mechanisms underlying metastasis still remain unclear. We previously established a suspension culture using low-attachment culture dishes and demonstrated that cell lines adapted through 2 months suspension culture (termed FL sublines) exhibited higher metastatic potential than their parental counterparts. In this study, we identified the molecules involved in acquiring these phenotypes under low-adhesion conditions. We showed that detached tumor cells in suspension culture formed spheroids that recapitulated tumor cells in the spread-through-air space (STAS), and demonstrated that the anti-adhesion molecule mucin 21 was upregulated in detached lung cancer cells independent of driver mutations. Analyses of both cell lines and primary tumors revealed that mucin 21 is overexpressed in terminal respiratory unit-type lung adenocarcinomas. Mucin 21-knockout cells showed reduced viability and proliferation under adherent and low-attachment conditions, accompanied by enhanced anoikis. Transmission electron microscopy revealed that the intercellular spaces observed in FL sublines during suspension culture were reduced in mucin 21-knockout cells, suggesting impaired acquisition of low adhesive properties. Thus, mucin 21 appears crucial for the survival of terminal respiratory unit-type lung adenocarcinoma cells under both adherent and low-adhesion conditions.

Abstract CEP152 is essential for centriole function and neurodevelopment, and pathogenic recessive variants in CEP152 cause primary microcephaly. We identified new compound heterozygous CEP152 variants, c.314 G > A,p.(W105*) and c.2689 A > T,p.(K897*), in a microcephalic patient and analyzed them alongside a homozygous variant c.95 A > C,p.(Q32P) associated with severe microcephaly with marked gyral simplification. In vitro assays revealed distinct effects: p.K897* prevented centrosomal localization, p.W105* led to protein degradation, and p.Q32P retained centrosomal targeting but disrupted binding to Polo-like kinase 4, a key centriole biogenesis kinase and CEP152 partner. In vivo, both Cep152W105*/K897* and Cep152Q32P/Q32P knock-in mice displayed microcephaly; notably, Cep152Q32P/Q32P mice also exhibited severe cortical defects during brain development. Cellular analyses revealed centrosome dysfunction, mitotic errors, and increased apoptosis, which were exacerbated in Cep152Q32P/Q32P brains. Morphological examination, including electron microscopy, further demonstrated structural abnormalities of the centrosomes and centrioles in Cep152Q32P/Q32P brains. Electrophysiological and gene expression analyses confirmed variant-specific neuronal impairments, which correlate with clinical severity. Collectively, these findings demonstrate that distinct CEP152 variants disrupt neurodevelopment through different mechanisms, thereby explaining the spectrum of microcephaly severity and associated phenotypes.

The ventricular-subventricular zone (V-SVZ) is the largest neurogenic niche in the postnatal mammalian brain, but its organization and migratory dynamics remain poorly understood in gyrencephalic species. Here, we provide ultrastructural and three-dimensional characterization of the V-SVZ neuroblasts in postnatal microminipigs, the smallest pig strain with unique advantages for experimental neuroscience. Transmission electron microscopy revealed developmental changes in cell composition and cytoarchitecture, with migratory neuroblasts consistently associated with glial cells and vasculatures. Notably, serial block-face scanning electron microscopy revealed that tier 3 neuroblasts, a gyrencephalic-specific population, formed elongated, chain-like clusters aligned along vessels, with conserved intracellular features such as polarized organelle distributions and growth cone extension. Radial glial fibers were prominent in neonates but diminished with age, suggesting a developmental shift to vascular scaffolds as primary migration guides. These findings establish microminipigs as a tractable gyrencephalic model for studying postnatal neurogenesis, offering new opportunities for translational research on brain repair.

Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) develop as spatial pathologies in which neurons and glial cells are interconnected. TAR DNA-binding protein 43 (TDP-43) is a major pathological protein that is inextricably associated with ALS and FTLD. In this study, we investigated the roles of neuronal TDP-43 in neuron-oligodendrocyte interactions using neuron-specific TDP-43 knockout (TDP-43cKO) mice. TDP-43 depletion in neurons induced hypomyelination, which was confirmed by immunohistochemistry and ultrastructural analysis. In addition, conduction disturbance was revealed by electrophysiological analysis. The hypomyelination of TDP-43cKO mouse was restored by cytoplasmic TDP-43 supplementation in neurons. Neuron-specific transcriptome analysis revealed that neurexin 1 (NRXN1) is the regulatory target of TDP-43, which promotes myelin formation. The hypomyelination of TDP-43cKO mice was also restored by NRXN1b supplementation in neurons. We further confirmed that TDP-43 stabilizes Nrxn1 mRNA by binding to the Nrxn1 3'untranslated region (3'UTR). Although TDP-43cKO exhibited impaired recognition memory, the supplementation of NRXN1 in the hippocampus recovered the memory disturbances. In conclusion, this study demonstrates the neuron-oligodendrocyte interaction mediated by neuronal TDP-43 via NRXN1 mRNA stabilization. These findings shed light on neuron-oligodendrocyte interaction in the disease mechanisms of ALS/FTLD.

Mossy fiber (MF)-CA3 synapses in the hippocampus play vital roles in learning and memory. MFs have characteristic giant boutons with thorny excrescences on the dendrites of CA3 pyramidal neurons. The mechanisms underlying the development of this complex synaptic specialization remain unclear. In the present study, the loss of synaptosomal-associated protein 25 (SNAP25)-a protein essential for regulated synaptic vesicular release-increased the density but decreased the size of MF boutons and altered the postsynaptic distribution of homer scaffolding protein 1. Three-dimensional correlative light and electron microscopy revealed that although axon targeting and synapse formation were unaffected, excrescences failed to develop in MF boutons, resulting in a smaller contact area between MF boutons and CA3 dendrites. Moreover, SNAP25-deficient boutons displayed abnormal intracellular profiles, such as the accumulation of large synaptic vesicles. These findings indicate that presynaptic SNAP25 is essential for the maturation and maintenance of specialized hippocampal giant boutons.

White matter in the central nervous system comprises bundled nerve fibers myelinated by oligodendrocytes. White matter injury, characterized by the loss of oligodendrocytes and myelin, is common after ischemic brain injury, inflammatory demyelinating diseases including multiple sclerosis, and traumatic damage such as spinal cord injury. Currently, no therapies have been confirmed to promote remyelination in these diseases. Over the past decade, various reports have suggested that the anti-muscarinic drug clemastine can stimulate remyelination by oligodendrocytes. Consequently, the repurposing of clemastine as a potential treatment for a variety of neurological disorders has gained significant attention. The therapeutic effects of clemastine have been demonstrated in various animal models, and its mechanisms of action in various neurological disorders are currently being investigated. In this review, we summarize reports relating to clemastine administration for white matter injury and neurological disease and discuss the therapeutic potential of remyelination promotion.

White matter injury is caused by cerebral blood flow disturbances associated with stroke and demyelinating diseases such as multiple sclerosis. Remyelination is induced spontaneously after white matter injury, but progressive multiple sclerosis and white matter stroke are usually characterised by remyelination failure. However, the mechanisms underlying impaired remyelination in lesions caused by demyelination and stroke remain unclear. In the current study, we demonstrated that collagen fibres accumulated in the demyelinated lesions of multiple sclerosis patients (age range 23–80 years) and white matter lesions of stroke patients (age range 80–87 years), suggesting that the accumulation of collagen fibres correlates with remyelination failure in these lesions. To investigate the function of collagen fibres in the white matter lesions, we generated two types of white matter injury in mice. We induced focal demyelination by lysolecithin (LPC) injection and ischemic stroke by endothelin 1 (ET1) injection into the internal capsule. We found that type I collagen fibres were secreted in ET1-induced lesions with impaired white matter regeneration in the chronic phase of disease. We also showed that monocyte-derived macrophages that infiltrated into lesions from the peripheral blood produced type I collagen after white matter injury, and that type I collagen also exacerbated microglial activation, astrogliosis, and axonal injury. Finally, we demonstrated that oligodendrocyte differentiation and remyelination were inhibited in the presence of type I collagen after LPC-induced demyelination. These results suggest that type I collagen secreted by monocyte-derived macrophages inhibited white matter regeneration, and therefore, the modulation of type I collagen metabolism might be a novel therapeutic target for white matter injury.

A common feature of various postnatal stem cells is their close association with blood vessels. Postnatal neural stem cells (NSCs) in the ventricular-subventricular zone originate from fetal radial glia (RG), which possess NSC properties. Here, using live imaging and three-dimensional (3D) electron microscopy, we investigated how RG convert into postnatal NSCs and characterized the fine 3D morphology of the ventricular-subventricular zone. We found that preterm birth disrupts RG-endothelial cell interactions during this transformation, impairing both the structure and stemness of adult NSCs. These findings underscore the importance of a birth-dependent transformation. Our results indicate that RG fiber transection, which depends on the birth process, and endfoot formation on blood vessels, which depends on birth timing, are both critical steps in the conversion of RG into adult NSCs.

This study developed a three-dimensional ultrastructural analysis application using serial block-face scanning electron microscopy (SBF-SEM) to investigate surgically acquired human skin tissues containing the arrector pili muscle. We utilized the en bloc staining, including reduced osmium, thiocarbohydrazide, and lead aspartate, as well as the embedding using a carbon-based conductive resin. Next, we obtained serial images with SBF-SEM. The results revealed dense nerve fiber networks branching from nearby nerve fiber bundles outside the muscle and running among muscle fibers. Additionally, the dense nerve network running through and along arrector pili muscle fibers rarely penetrates the connective tissues between smooth muscle fibers and epithelial cells. Furthermore, in the observation area, no individual smooth muscle fibers formed adhesion structures with the epithelial cells of the hair follicle, ending in the dermal extracellular matrix near the epithelial cells. These results indicate the usefulness of this approach for three-dimensional ultrastructural analyses of human skin tissues comprising follicular units and revealing structural changes in skin tissues, especially the arrector pili muscle and nerve fibers with hair follicular epithelium, in aging and diseased conditions.

White matter injury is a cerebral pathology marked by the loss of oligodendrocytes and the resultant demyelination. Various mechanisms induce white matter injury, including ischemic stroke and multiple sclerosis. Oligodendrocytes regenerate white matter in the central nervous system in a process called remyelination, ensheathing demyelinated axons with new myelin. While failures of remyelination can be observed in progressive multiple sclerosis and after ischemic stroke, the mechanisms of impaired white matter regeneration remain unclear. In this review, we primarily focus on our recent work while summarizing studies reporting on mouse models of internal capsule demyelination and discuss inhibitory factors affecting white matter regeneration. In addition, we provide recent findings on the role of type I collagen as an inhibitory molecule of remyelination in white matter lesions.

Leukemia cells are consistently subjected to higher oxidative stress than normal cells. To mitigate reactive oxygen species (ROS) overload, which can trigger various forms of cell death, leukemia cells employ a robust antioxidant defense system and maintain redox homeostasis. Recent evidence suggests that dimethyl fumarate (DMF), a derivative of fumarate, inactivates the antioxidant glutathione (GSH), thereby inducing oxidative stress and metabolic dysfunction, eventually leading to cell death in cancer cells. In this study, we observed that DMF decreases the GSH/oxidated GSH ratio and increases intracellular ROS levels, the extent of which is closely correlated with cell death, in acute myeloid leukemia (AML) cell lines. DMF reduced the mitochondrial membrane potential and oxidative phosphorylation (OXPHOS), effects that were almost fully restored by the antioxidant N-acetylcysteine, suggesting that these responses are ROS-dependent. Electron microscopy and inhibition assays revealed that apoptosis, rather than necroptosis or ferroptosis, is the predominant form of cell death of AML cells following DMF treatment. Notably, the combination of DMF and the BCL-2 selective BH3-mimetic venetoclax induced marked cell death in AML cells, including venetoclax-refractory BCL-2 low expressing U937 and acquired venetoclax-resistant MOLM-14 cells. This combination also caused greater mitochondrial depolarization and a more profound reduction in OXPHOS activity than either agent alone. Collectively, our findings indicate that DMF exerts potent anti-leukemia activity in AML cells and sensitizes cells to venetoclax treatment by synergistically disrupting mitochondrial integrity through ROS accumulation.

Structural observations are essential for the advancement of life science. Volume electron microscopy has recently realized remarkable progress in the three-dimensional analyses of biological specimens for elucidating complex ultrastructures in several fields of life science. The advancements in volume electron microscopy technologies have led to improvements, including higher resolution, more stability and the ability to handle larger volumes. Although human applications of volume electron microscopy remain limited, the reported applications in various organs have already provided previously unrecognized features of human tissues and also novel insights of human diseases. Simultaneously, the application of volume electron microscopy to human studies faces challenges, including ethical and clinical hurdles, costs of data storage and analysis, and efficient and automated imaging methods for larger volume. Solutions including the use of residual clinical specimens and data analysis based on artificial intelligence would address those issues and establish the role of volume electron microscopy in human structural research. Future advancements in volume electron microscopy are anticipated to lead to transformative discoveries in basic research and clinical practice, deepening our understanding of human health and diseases for better diagnostic and therapeutic strategies.

Familial neurohypophysial diabetes insipidus (FNDI) is an autosomal dominant disorder caused by mutations in the arginine vasopressin (AVP) gene. In AVP neurons in a mouse model of FNDI, aggregates of mutant AVP precursors accumulate within a specific compartment of the endoplasmic reticulum (ER). However, as FNDI mice aged, or were exposed to repeated water deprivation, the ER lumen dilated and mutant aggregates dispersed throughout the ER. Meanwhile, autophagic isolation membranes, known as phagophores, emerged to envelop ER containing these aggregates, indicating induction of ER-phagy. Previous in vitro studies showed that phagophores originate from ER membranes, but the structural relationship between phagophores and the ER membrane in vivo remains unknown. In this study, we used serial block-face scanning electron microscopy to investigate the structural relationship between phagophores, ER membranes, and protein aggregates within dilated ER of AVP neurons from FNDI mice subjected to intermittent water deprivation for 4 weeks. Three-dimensional analysis revealed that phagophores enveloped aggregates located within the dilated ER. Serial imaging further demonstrated a physical connection between these phagophores and intact ER membranes. This study provides the first in vivo evidence of the structural continuity between phagophores and the ER membrane in AVP neurons in a mouse model of FNDI.

Myelin formation by oligodendrocytes is essential for the regulation of the conduction velocity and proper brain function. To ensure accurate information processing in response to experiences such as sensory stimuli and learning, oligodendrocytes adjust their number and morphology. In addition, oligodendrocyte morphology changes with senescence and in the presence of neurodegenerative diseases. Thus, visualizing oligodendrocytes and analyzing their morphology is crucial for understanding how our brains change under such conditions. Herein, we describe the methods for labeling and analyzing the morphologies of individual oligodendrocytes in mouse white matter at the light microscopic level. PDGFRa-CreERT2:Tau-mGFP and PLP-CreERT2:Tau-mGFP mice enable us to visualize and analyze later-born or early-born oligodendrocyte morphology. In addition, sparse oligodendrocyte labeling with attenuated rabies virus expressing GFP enables the visualization and morphological analysis of individual oligodendrocytes in various brain white matter regions without the need for transgenic animals. Furthermore, the combination with immunostaining in thick tissues enables the identification of labeled oligodendrocytes and myelin sheaths, as well as their interactions with neuronal axons. These methods are suitable for revealing how oligodendrocytes adapt their morphologies depending on environmental stimuli or pathological conditions. ### Competing Interest Statement The authors have declared no competing interest. KAKENHI Grants from the Japan Society for the Promotion of Science, 20KK0170, 21H04786, 21H05241, 21K15197, 23K14432, 24H00583, 24K09670, 25K02967, 25K23758. National Center of Neurology and Psychiatry, 3–5 The Uehara Memorial Foundation, 202210148 Takeda Science Foundation Kobayashi Foundation Jichi Medical University Japan Multiple Sclerosis Society Japan Association for Chemical Innovation