Biology subjects

Yashiro, K.

Publications and source records attributed to Yashiro, K..

8 recordsLinked to original sources

bioRxiv2026

Topological defects and coherent myocardial chirality shape torsional heart contraction

The efficient pumping of the mammalian heart relies on torsional contractile motion generated by its highly ordered three-dimensional (3D) architecture of myocardial fibres. However, the topological principles governing how its complex geometry translates into contractile mechanics remain elusive. Here, we show that the mammalian heart forms a chiral nematic field, a biological analogue to 3D liquid crystals, whose topological organisation underlies its function. Analysis of 3D imaging data revealed disclination lines, continuous assemblies of topological defects characteristic of nematic systems, within the compact myocardium. Finite-element simulations reveal that these defects are not mere structural irregularities but can locally modulate contractile behaviour and reduce mechanical work. In heterotaxy hearts with reversed global anatomy (situs inversus), myocardial fibres retain a predominantly counter-clockwise twist, similar to that of the normal heart, but with a small clockwise component near the base. This decoupling of tissue-level chirality from systemic left-right patterning suggests that cardiac twist is an intrinsic property of the myocardial fibre. Mechanical simulations of situs inversus heart demonstrate that the coherence of transmural chirality, rather than its specific orientation, is critical for contractile efficiency. Together, these findings establish the heart as a topological material and reveal how organised chiral fields generate robust organ-level mechanical function.

biophysics↗

bioRxiv2025

L-Phenylalanine restriction amplifies boron neutron capture therapy efficacy through increased L-boronophenylalanine uptake and induces activating transcription factor 4 stress response in tumor cell lines

Boron neutron capture therapy (BNCT) relies on the selective uptake of boron-10 compounds by tumor cells. L-boronophenylalanine (BPA) serves as a key carrier, and enhancing its accumulation is critical for improving BNCT efficacy. In this study, we investigated the effects of L-phenylalanine (Phe) restriction on the tumor cell lines SAS, U87-MG, PANC-1, and A375, and the immortalized keratinocyte line HaCaT on modulating BPA uptake and associated cellular responses. Quantitative analysis using inductively coupled plasma atomic emission spectroscopy (ICP-AES) showed that 24 h Phe restriction increased BPA uptake in the SAS, U87-MG, and PANC-1 cell lines. Colony formation assays confirmed enhanced sensitivity to neutron irradiation in these cells. RNA sequencing indicated that Phe restriction activated the integrated stress response downstream of activating transcription factor 4 (ATF4), although this pathway was not directly linked to increased BPA uptake. The L-type amino acid transporter 1 (LAT1)/4F2 heavy chain (4F2HC) complex was identified as the exclusive transport route for BPA. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis showed that Phe restriction altered intracellular levels of amino acids that serve as LAT1/4F2HC exchange substrates, suggesting a metabolic basis for enhanced BPA transport. Our results reveal that Phe restriction enhances BPA uptake and BNCT efficacy in a cell line-dependent manner, likely through the modulation of amino-acid metabolism. Therefore, targeted amino-acid manipulation prior to BNCT may represent a promising strategy to improve therapeutic outcomes.

cancer biology↗

bioRxiv2024

BMP4 regulates asymmetric Pkd2 distribution in mouse nodal immotile cilia and ciliary mechanosensing required for left-right determination

BackgroundMouse nodal immotile cilia mechanically sense the bending direction for left-right (L-R) determination and activate the left-side-specific signaling cascade, leading to increased Nodal activity. Asymmetric distribution of Pkd2, a crucial channel for L-R determination, on immotile cilia has been reported recently. However, the causal relationship between the asymmetric Pkd2 distribution and direction-dependent flow sensing is not well understood. Furthermore, the underlying molecular mechanism directing this asymmetric Pkd2 distribution remains unclear. ResultsThe effects of several recombinant proteins and inhibitors on the Pkd2 distribution were analyzed using super-resolution microscopy. Notably, bone morphogenetic protein 4 (BMP4) affected the Pkd2 distribution. Additionally, three-dimensional manipulation of nodal immotile cilia using optical tweezers revealed that excess BMP4 caused defects in the mechanosensing ability of the cilia. ConclusionsExperimental data together with model calculations suggest that BMP4 regulates the asymmetric distribution of Pkd2 in nodal immotile cilia, thereby affecting the ability of these cilia to sense the bending direction for L-R determination. This study, for the first time, provides insight into the relationship between the asymmetric protein distribution in cilia and their function.

developmental biology↗

bioRxiv2023

Acto3D: user- and budget-friendly software for multichannel high-resolution three-dimensional imaging

Advances in fluorescence microscopy and tissue-clearing technology have revolutionized three-dimensional (3D) imaging of fluorescently labeled tissues, organs, and embryos. However, the complexity and high cost of existing software and computer solutions for such imaging limit its widespread adoption by researchers with limited resources. We here introduce Acto3D as a user- and budget-friendly, open-source computer software application designed to streamline the generation and observation of high-resolution 3D images of targets labeled with multiple fluorescent probes. Acto3D features an intuitive interface that simplifies the importation, visualization, and analysis of data sets, has an associated tool for annotation of vascular lumens, and incorporates multiple fluorescence channels for comprehensive imaging. Underpinned by an integrated graphics processing unit, Acto3D allows accurate image reconstruction and efficient data processing without the need for expensive high-performance computers. We validated the software by imaging mouse embryonic structures. Acto3D thus constitutes a cost-effective and efficient platform to support biological research.

developmental biology↗

bioRxiv2023

Ciliary protein CEP290 regulates focal adhesion via microtubule system in non-ciliated cells

Almost all differentiated mammalian cells have primary cilia on their surface. Ciliary dysfunction causes ciliopathy in humans. Centrosomal protein 290 (CEP290) is a ciliary protein that causes ciliopathies, localizes at the cilial base in ciliated cells, whereas it localizes to the centrosome in non-ciliated proliferating cells. The cilia-dependent function of CEP290 has been extensively studied; however, the cilia-independent function, which is likely responsible for the wider phenotypic spectra of CEP290-related ciliopathies, remains largely unknown. Here, we examined cilia-independent functions of CEP290 in non-ciliated cells. Our study showed that Cep290 function loss suppresses microtubule elongation due to microtubule organizing center malfunction. Surprisingly, CEP290 forms a complex with the adenomatous polyposis coli (APC) protein encoded by the adenomatous polyposis coli gene. The APC-CEP290 complex exists in the centrosome and on microtubule fibers. Notably, the reduced focal adhesion formation is likely responsible for the Cep290 mutant phenotypes, including impaired directed cell migration, shrunken cell shape, and reduced adhesive capacity to the extracellular matrix. The APC-CEP290 complex is consistently important for transporting a focal adhesion molecule, paxillin, to focal adhesions in non-ciliated cells. Thus, our findings provide a novel platform to better understand the ciliopathies.

cell biology↗

bioRxiv2021

Myosin phosphatase target subunit 1 governs integrity of the embryonic gut epithelium to circumvent atresia development in medaka, Oryzias latipes

Congenital intestinal atresia (IA) is a birth defect characterised by the absence or closure of part of the intestine. Although genetic factors are implicated, mechanistic understanding has been hindered by the lack of suitable animal models. Here, we describe a medaka (Oryzias latipes) mutant, generated by N-ethyl-N-nitrosourea (ENU) mutagenesis, that develops IA during embryogenesis. Positional cloning identified a nonsense mutation in mypt1, encoding myosin phosphatase target subunit 1. Mutant embryos exhibited ectopic accumulation of F-actin and phosphorylated myosin regulatory light chain (Mrlc) in the intestinal epithelium, consistent with disrupted actomyosin regulation. These cytoskeletal abnormalities were accompanied by epithelial disorganisation without notable alterations in cell proliferation, motility, or apoptosis. Inhibition of myh11a, encoding smooth muscle (SM) myosin heavy chain, ameliorated the IA phenotype but Blebbistatin treatment completely rescued the defect, suggesting a non-contractile role prior to SM maturation. Together, these findings demonstrate that mypt1 loss disrupts intestinal morphogenesis through actomyosin dysregulation. Given the recent clinical identification of IA associated with MYPT1 mutations, this medaka model offers a valuable platform to investigate the developmental and molecular basis of MYPT1-associated IA in human.

developmental biology↗

bioRxiv2020

AMPK regulates cell shape of cardiomyocytes by modulating turnover of microtubules through CLIP-170

AMP-activated protein kinase (AMPK) is a multifunctional kinase that regulates microtubule (MT) dynamic instability through CLIP-170 phosphorylation; however, its physiological relevance in vivo remains to be elucidated. In this study, we identified an active form of AMPK localized at the intercalated discs in the heart, a specific cell-cell junction present between cardiomyocytes. A contractile inhibitor, MYK-461, prevented the localization of AMPK at the intercalated discs, and the effect was reversed by the removal of MYK-461, suggesting that the localization of AMPK is regulated by mechanical stress. Time-lapse imaging analysis revealed that the inhibition of CLIP-170 Ser-311 phosphorylation by AMPK leads to the accumulation of MTs at the intercalated discs. Interestingly, MYK-461 increased the individual cell area of cardiomyocytes in CLIP-170 phosphorylation-dependent manner. Moreover, heart-specific CLIP-170 S311A transgenic mice demonstrated elongation of cardiomyocytes along with accumulated MTs, leading to progressive decline in cardiac contraction. In conclusion, these findings suggest that AMPK regulates the cell shape and aspect ratio of cardiomyocytes by modulating the turnover of MTs through homeostatic phosphorylation of CLIP-170 at the intercalated discs.

cell biology↗

bioRxiv2019

Sox17 expression in endocardium precursor cells regulates heart development in mice

The endocardium is the endothelial component of the vertebrate heart and plays a key role in heart development. Cardiac progenitor cells (CPCs) that express the homeobox gene Nkx2-5 give rise to the endocardium. Where, when, and how the endocardium segregates during embryogenesis have remained largely unknown, however. We now show that Nkx2-5+ CPCs that express the Sry-type HMG box gene Sox17 specifically differentiate into the endocardium in mouse embryos. Approximately 20% to 30% of Nkx2-5+CPCs transiently express Sox17 from embryonic day (E) 7.5 to E8.5.Although Sox17 is not essential or sufficient for endocardium fate, it can bias the fate of CPCs toward the endocardium. On the other hand, Sox17 expression in the endocardium is required for heart development. Deletion of Sox17 specifically in the mesoderm markedly impaired endocardium development with regard to cell proliferation and behavior. The proliferation of cardiomyocytes, ventricular trabeculation, and myocardium thickening were also impaired in a non-cell-autonomous manner in the Sox17 mutant, resulting in anomalous morphology of the heart, likely as a consequence of down-regulation of NOTCH signaling. Changes in gene expression profile in both the endocardium and myocardium preceded the reduction in NOTCH-related gene expression in the mutant embryos, suggesting that Sox17 expression in the endocardium regulates an unknown signal required for nurturing of the myocardium. Our results thus provide insight into differentiation of the endocardium and its role in heart development. SignificanceThe endocardium is vital for vertebrate heart development; however, the molecular mechanisms regulating fate determination and differentiation remain largely unknown. Here, we show that a part of the earliest cardiac progenitor cells (CPCs) transiently and exclusively express Sry-type HMG box gene Sox17 in the mouse embryo. Sox17-expressing CPCs specifically differentiate to the endocardium. Sox17 biases the fate of CPCs toward the endocardium, and regulates proliferation and cellular behavior cell autonomously. Conversely, Sox17 in the endocardium regulates the myocardium non-cell autonomously. Notably, Sox17 is required for the ventricular trabeculation via the NOTCH signal that is not directly induced but maintained by Sox17. This study, thus, sheds light on endocardium development.

developmental biology↗