Biology subjects

Katsuno, T.

Publications and source records attributed to Katsuno, T..

8 recordsLinked to original sources

bioRxiv2026

A visualization framework for cell division activity and orientation in pre-anthesis ovaries of Prunus species

Fruit size and shape, which influence horticultural quality, are determined by the number and the size of the cells in the local region. In fruit trees, however, the difficulty of applying molecular genetic approaches has hindered a detailed understanding of the localization and orientation of cell division in developing fruit tissues. In this study, we established a novel framework to visualize cell division in pre-anthesis ovaries of three drupe crops, peach (Prunus persica), Japanese apricot (P. mume) and the interspecific hybrid Japanese apricot (P. salicina x P. mume), providing clear insight into the spatial distribution and orientation of dividing cells. We systematically optimized a 5-ethynyl-2'-deoxyuridine (EdU) labeling protocol for thick ovary tissues by adjusting infiltration conditions and fixation methods. In addition, electron microscopy combined with wide-view tiling visualization was applied to directly identify dividing cells, including those undergoing chromosome segregation and cell plate formation. By combining with machine learning-based detection, we efficiently and objectively identified dividing cells. Using these complementary approaches, we found that cell division activity was broadly distributed throughout pre-anthesis ovaries in all three crops, without pronounced spatial restriction. In contrast, analysis of division orientation revealed region-specific patterns: cells in the outermost exocarp divided predominantly anticlinally, whereas cells in the mesocarp divided largely periclinally, consistent with subsequent ovary (fruit) enlargement. The integrated framework presented here provides a foundation for understanding the spatial and three-dimensional regulation of fruit development and for future studies in fruit morphogenesis and horticulture.

plant biology↗

bioRxiv2025

Roles of a Drosophila ADAM 10 transmembrane metalloprotease, Kuzbanian, in tissue architecture and function of the adult adipose tissue

Various molecular mechanisms in mature adipose tissue regulate whole-body physiology. In contrast, our current understanding of the development of this tissue is limited. The adult fat body (AFB) of Drosophila melanogaster is an emerging model for investigating the regulatory mechanisms of adipose tissue morphogenesis in vivo. AFB precursor cells undergo long-range directional and collective migration, proliferation, and homotypic adhesion, leading to the formation of monolayered AFB during metamorphosis. Here, we show that a Drosophila ADAM10 transmembrane metalloprotease, Kuzbanian (Kuz), is required for the AFB morphogenesis in the precursor cells at the onset of adhesion. Histological and ultrastructural analyses revealed that the kuz knocked-down AFB cells formed multilayered structures or clumps, indicating that Kuz is essential for forming a single-cell-thick tissue sheet. Furthermore, adults with the morphologically altered AFB were supersensitive to starvation stress. Finally, we tested the hypothesis that Notch (N), a well-characterized substrate for Kuz or ADAM10, participates in AFB development, and found that knocking down N reduced AFB area coverage and made the adults less adaptive to starvation, similar to kuz knockdown. Altogether, our study highlights the critical role of Kuz in both the architecture and function of adult adipose tissue.

developmental biology↗

bioRxiv2025

Uric acid accumulation in cockroach wings

Cockroaches, embracing some 4,500 species in the world, are found in a variety of environments including human settlements. The ecological success of cockroaches is attributable to the ability to endure long periods of starvation and to thrive on nutritionally poor diets, which is underpinned by the capability of storing their own nitrogenous waste products as uric acid in the fat body and also by the endosymbiosis with bacteriocyte-dwelling bacteria Blattabacterium that recycle the stored uric acid for synthesis of amino acids. Previous histological studies on cockroaches described that uric acid is accumulated within the fat body, especially in urocytes. Here we report that cockroaches also accumulate uric acid in the wings. In our observation of the German cockroach Blattella germanica under different nutritional conditions, we found that well-fed cockroaches exhibited whitish aggregates in the wing veins, which is ascribed to accumulation of uric acid granules. The uric acid granules in the wings disappeared by starvation and were restored by feeding in B. germanica. The uric acid granules in the wings were found not only in B. germanica but also in other diverse cockroach species.

physiology↗

bioRxiv2025

Cockroach bacteriocytes migrate into the ovaries for vertical transmission of the bacterial endosymbiont Blattabacterium

Diverse insect groups are obligatorily associated with and dependent on specific microorganisms as essential mutualistic partners that are usually maintained in specialized cells or organs, called bacteriocytes or symbiotic organs. Many organisms with symbiotic microorganisms have developed elaborate vertical transmission mechanisms, which are thought to be important for the evolution of intimate symbiotic relationships with microorganisms. One such case is the cockroach-Blattabacterium endosymbiosis, in which the symbiotic bacteria have been evolutionarily conserved and co-speciated with the host insects with stable vertical symbiont transmission via ovarial passage. While classical histological descriptions and recent electron microscopic observations have reported the vertical symbiont transmission processes in some cockroach-Blattabacterium associations, the full picture of the infection dynamics has not been fully understood. In this study, we conducted detailed histological and cytological observations of the localization of the bacteriocytes and the symbiotic bacteria during the postembryonic development of the German cockroach Blattella germanica. We found that the symbiont-filled bacteriocytes migrate into and associate with nymphal ovaries and are subsequently eliminated from adult ovaries, suggesting that symbiont infection to the ovaries may only occur during nymphal stages. We also found that the symbiotic bacteria are localized in the space between each oocyte and surrounding follicle cells, the symbiont-localized space is interconnected between neighboring oocytes, and therefore the symbiotic bacteria can move across oocytes within the same ovariole, suggesting the possibility that the symbiont-infected oocytes may serve as the source of symbiont supply to developing young oocytes upstream in the same ovariole. Based on these observations, we provide a hypothesis as to how the postembryonic developmental dynamics of the bacteriocytes are integrated into the vertical symbiont transmission and functioning in the cockroach-Blattabacterium endosymbiosis.

developmental biology↗

bioRxiv2025

Identification of stem cell marker-positive subpopulations in the vocal fold of the larynx through transcriptomic analyses

Information on the maintenance of tissue homeostasis is important for the development of effective therapeutic methods, however, reports on the cellular composition and tissue stem cells of the larynx were scarce. Therefore, we analyzed mouse laryngeal mucosa using scRNA-seq, and spatial transcriptomics by photo-isolation chemistry, and performed the generation of laryngeal organoid used as an in vitro model from mouse laryngeal mucosa. As a result, we found a SOX9-positive basal cell subpopulation and a Lgr5-positive fibroblast subpopulation in the mouse vocal fold, and obtained three types of epithelial organoids from laryngeal epithelium. We also confirmed the differences in pseudostratified ciliated columnar epithelium composition between the supraglottis and subglottis of the mouse larynx. These findings provide novel insights and valuable tools for future research in laryngology and stem cell biology.

cell biology↗

bioRxiv2024

Direct Intercellular Vesicle Exchange between Adjacent Cells

Intercellular communication plays a central role in the development and integrity of multicellular organisms. Vesicle transfer, especially through extracellular space, has recently been highlighted as a critical intercellular communication modality, carrying nucleic acids, proteins, and others to distant cells. Previously, we demonstrated that extracellular vesicles induce "phenotypic synchronization of cells (PSyC)" during stem cell differentiation. While examining the mechanism underlying PSyC, we discovered a novel form of cellular communication mediated by direct intercellular vesicle exchange (DIVE) between adjacent cells across the plasma membrane (PM). By achieving cell-wide and high-spatiotemporal resolution imaging of vesicles labeled with fusion proteins of CD63 or CD81 to StayGold, a photostable fluorescent marker, we observed small vesicles (50-500 nm in diameter) directly transferred between adjacent cells. These vesicles moved at approximately 1 {micro}m/s and crossed PM in approximately 10-20 seconds. Furthermore, multiple vesicles traversed nearly identical sites of PM, suggesting the presence of specific routes or structures, potentially including a pore, mediating the vesicle transfer. Three-dimensional electron microscopy provided supportive observations for traversing vesicles with single membrane. These vesicles, named InterCellular Vesicles (InterCVs), were observed to colocalize with nucleic acids, including mRNA, microRNA, and DNA, suggesting the exchange of nucleic acid-mediated information, potentially inducing PSyC, between adjacent cells. Our discovery, DIVE, reveals a previously unknown modality of cell-cell communication, with the potential to reshape our understanding of cellular biology.

cell biology↗

bioRxiv2024

Ca2+-evoked sperm cessation determines embryo number in mammals.

In mammals, fertilization takes place followed by fetus development in the maternal body, so the number of fetuses that exceeds the mothers capacity increases the frequency of stunted growth and stillbirths, while an excessive number of pups increases postnatal stunting and maternal child-rearing stress, which is detrimental to offspring procreation and species maintenance. Therefore, various control mechanisms are thought to be at work to ensure that fertilization occurs in appropriate numbers. Sperm are not capable of fertilization immediately after they are produced in the testis, and must undergo a stepwise activation process including capacitation, hyper motility activation or acrosome reaction before they meet the egg in the oviduct, where fertilization takes place, contributing positively on fertilization, which in turn ensures the number of fetuses for the maintenance of species. In contrast, in this study, we found that a subpopulation of sperm is derived in a Ca2+-dependent manner during the process for sperm to acquire fertility, which may regulate the number of fetuses. When sperm were harvested from the epididymis of mice and activated in vitro, a subpopulation of sperm emerged from the sperm population in which Lypd4 was expressed on the sperm surface at a ratio up to 30%. The sperm in this subpopulation were rather small in size, more permeable to dyes, and had already ceased motility. We further characterized this sperm population by surface antigen screening using various monoclonal antibodies and found the expression of several proteins, such as CD55, ICOS or Ccr3, specific to this population. The emergence of this sperm population was induced at a concentration of about 4% of Ca2+ in body fluids and was independent of capacitation or acrosome reaction, and also apoptotic process. This subpopulation also appeared over time in sperm ejaculated into the female body, accounting for about 50% of the sperm that reached the oviduct in an hour. When this sperm subpopulation was then removed from the entire population using anti-Lypd4 antibody followed by in utero insemination, the fertilization rate of the oocytes collected from the oviducts doubled. Such a sperm subpopulation was also observed in macaque monkeys, and removal of this subpopulation increased the egg penetration rate of sperm, suggesting that this sperm subpopulation exists commonly in mammals and that the mothers acceptable fetal number is adjusted by systematically sterilizing a certain number of sperm.

developmental biology↗

bioRxiv2024

Frequent and asymmetric cell division in endosymbiotic bacteria of cockroaches

Many insects are obligatorily associated with and dependent on specific microbial species as essential mutualistic partners. In the host insects, such microbial mutualists are usually maintained in specialized cells or organs, called bacteriocytes or symbiotic organs. Hence, potentially exponential microbial growth cannot be realized but must be strongly constrained by spatial and resource limitations within the host cells or tissues. How such endosymbiotic bacteria grow, divide and proliferate is important for understanding the interactions and dynamics underpinning intimate host-microbe symbiotic associations. Here we report that Blattabacterium, the ancient and essential endosymbiont of cockroaches, exhibits unexpectedly high rates of cell division (20-58%) and, in addition, the cell division is asymmetric (average asymmetry index > 1.5) when isolated from the German cockroach Blattella germanica. The asymmetric division of endosymbiont cells at high frequencies was observed irrespective of host tissues (fat bodies vs. ovaries) or developmental stages (adults vs. nymphs vs. embryos) of B. germanica, and also observed in several different cockroach species. By contrast, such asymmetric and frequent cell division was observed neither in Buchnera, the obligatory bacterial endosymbiont of aphids, nor in Pantoea, the obligatory bacterial gut symbiont of stinkbugs. Comparative genomics of cell division-related genes uncovered that the Blattabacterium genome lacks the Min system genes that determine the cell division plane, which may be relevant to the asymmetric cell division. These observations combined with comparative symbiont genomics provide insight into what processes and regulations may underpin the growth, division and proliferation of such bacterial mutualists continuously constrained under within-host conditions. IMPORTANCEDiverse insects are dependent on specific bacterial mutualists for their survival and reproduction. Due to the long-lasting coevolutionary history, such symbiotic bacteria tend to exhibit degenerative genomes and suffer uncultivability. Because of their microbiological fastidiousness, the cell division patterns of such uncultivable symbiotic bacteria have been poorly described. Here, using fine microscopic and quantitative morphometric approaches, we report that, although bacterial cell division usually proceeds through symmetric binary fission, Blattabacterium, the ancient and essential endosymbiont of cockroaches, exhibits frequent and asymmetric cell division. Such peculiar cell division patterns were not observed with other uncultivable essential symbiotic bacteria of aphids and stinkbugs. Gene repertoire analysis revealed that the molecular machineries for regulating the bacterial cell division plane are lost in the Blattabacterium genome, suggesting the possibility that the general trend toward the reductive genome evolution of symbiotic bacteria may underpin their bizarre cytological/morphological traits.

microbiology↗