Biology subjects

Nakashima, T.

Publications and source records attributed to Nakashima, T..

7 recordsLinked to original sources

bioRxiv2026

Osteocyte State Transitions Modulate Bone Remodeling During Early Skeletal Aging

Osteocytes are long-lived cells that play a central role in bone homeostasis, yet age-related changes in their functional states remain poorly understood, particularly because skeletal aging involves multiple processes beyond cellular senescence. We generated an osteocyte-specific MepeCre mouse line and combined osteocyte ablation in young and middle-aged mice with skeletal phenotyping, single-cell transcriptomics, and senolytic treatment. MepeCre-driven recombination was largely confined to osteocytes, with minimal off-target activity. Osteocyte ablation increased bone mass at both ages, indicating that osteocytes constrain bone accrual as part of their role in skeletal homeostasis. However, the accompanying remodeling changes differed with age: enhanced osteoblast activity predominated in young mice, whereas reduced osteoclast-mediated bone resorption predominated in middle-aged mice. Single-cell transcriptomics revealed distinct osteocyte subpopulations whose relative abundance shifted with age, from a predominantly matrix-enriched state in young mice to an expanded aging-transitional state in middle-aged mice. Although this state showed partial enrichment of senescence-associated transcriptional signatures, senolytic treatment failed to recapitulate the increase in bone mass induced by osteocyte ablation. Osteocyte therefore regulate bone mass through age-dependent mechanisms that coincide with shifts in osteocyte-state composition. These changes emerge by middle age and may contribute to early remodeling imbalance before overt cellular senescence during skeletal aging. Graphical AbstractGraphical summary of the findings of this study. AA, amino acids; NA, nucleic acid; UA, uric acid; TCA, tricarboxylic acid.

molecular biology↗

bioRxiv2025

Synergistic RAS-MAPK and AKT Activation in MYC-Driven Tumors via Adjacent PVT1 Rearrangements

MYC-driven (MYC+) cancers are aggressive and often fatal. MYC dysregulation is a key event in these cancers, but overexpression of MYC alone is not always enough to cause cancer. Plasmocytoma Variant Translocation 1 (PVT1), a long non-coding RNA (lncRNA) adjacent to MYC on chromosome 8 is a rearrangement hotspot in many MYC+ cancers. In addition to being co-amplified with MYC, the genomic rearrangement at PVT1 involves translocation, which has had obscure functional consequences. We report that translocation at the PVT1 locus cause asymmetric enrichment of 5-PVT1 and loss of 3-PVT1. Despite being classified as a non-coding RNA, the retained 5 region of PVT1 generates a circular RNA (CircPVT1) that codes for the novel peptide we call Firefox (FFX). FFX augments AKT signaling and synergistically activates MYC and mTORC1 in these cells. Further, the 3 end of PVT1, which is lost during the translocation, codes for a tumor-suppressing micropeptide we named as Honeybadger (HNB). We demonstrate that HNB interacts with KRAS and disrupts the activation of KRAS effectors. Loss of HNB leads to activation of RAS/MAPK signaling pathway, and enhances MYC stability by promoting phosphorylation of MYC at Ser62. These findings identify PVT1 as a critical node that synchronizes MYC, AKT, and RAS-MAPK activities in cancer. Our study thus identifies a key mechanism by which rearrangements at the PVT1 locus activate additional oncogenic pathways that synergize with MYC to exacerbate the aggressiveness of MYC+ cancers. This newfound understanding explains the poor prognosis associated with MYC+ cancers and offers potential therapeutic targets that could be leveraged in treatment strategies for these cancers.

cancer biology↗

bioRxiv2023

Effect of percutaneous ventricular assisted device on post-cardiac arrest myocardial dysfunction in swine model with prolonged cardiac arrest

BackgroundPercutaneous left ventricular assist device (pLVAD) can provide hemodynamic support during and after cardiac arrest, but it remains unclear if pLVAD reduces post-cardiac arrest myocardial dysfunction. MethodsThis is an analysis of a subset of animals that achieved return of spontaneous circulation (ROSC) in a study comparing pLVAD, transient aortic occlusion (AO), or both during cardiopulmonary resuscitation (CPR) after prolonged cardiac arrest. pLVAD, AO, or both were initiated after 24 minutes of ventricular fibrillation cardiac arrest (8 min no-flow and 16 min mechanical CPR). AO was discontinued post-ROSC, and pLVAD support or standard care were continued. Beginning 60 minutes post-ROSC, pLVAD support was weaned to <1.0 L/min while maintaining a mean arterial pressure >70 mmHg, and subsequently removed at 240 minutes when feasible. The primary outcome was the recovery of cardiac index (CI), stroke volume index (SVI), and left ventricular ejection fraction (LVEF) at 240 minutes post-ROSC. Data are shown as mean (standard error). ResultsSeventeen animals achieved ROSC without complication and were included in this analysis (pLVAD group, n = 11 and standard care group, n = 6). For the primary outcome, the pLVAD group had significantly higher CI of 4.2(0.3) vs. 3.1(0.4) L/min/m2 (p=0.043) and LVEF 60(3) vs. 49(4) % (p=0.029) at 240 minutes after ROSC, respectively, when compared with the standard care group, while SVI was not significant difference (2[3] vs. 23[4] mL/min/m2, p=0.054). During the first 60 minutes after ROSC with maximum pLVAD flow, the pLVAD group had significantly higher coronary perfusion pressure (62[4] vs. 47[5] mmHg, p=0.019), lower LV stroke work index (3.9[3.0] vs. 14.9[4.4] cJ/m2, p=0.043), and lower total pulmonary resistance index (13.2[4.8] vs. 21.5[14.4] Wood Unit, p=0.001). ConclusionThese results suggest that early pLVAD support after ROSC is associated with better recovery myocardial function compared to standard care after prolonged cardiac arrest.

physiology↗

bioRxiv2022

Mycelial differentiation linked avermectin production in studied with Raman imaging

Streptomyces avermitilis is a gram-positive bacterium that undergoes complex physiological and morphological differentiation during its life cycle, which has implications in secondary metabolites production. Avermectin, produced by S. avermitilis, is widely used as an anthelmintic and insecticidal agent. In this study, we have applied Raman microspectroscopic imaging to elucidate the correlation between production of avermectin and the morphological differentiation in S. avermitilis. We demonstrate distinctive variations in the localization of avermectin at various morphological stages, such as, substrate mycelium, spore-bearing mycelium, spiral spore chains under solid culture conditions. Under liquid culture condition, however, avermectin is detected only in mycelia after early MII stage of differentiation. Morphological differentiation was observed in liquid and solid cultures, but the chemical profiles of the mycelia were substantially different. Spherical bodies containing avermectin with characteristically different chemical composition to that of spores were also observed under solid culture, which suggests possible release of extracellular vesicles (EVs). Key pointsO_LIAvermectin production is regulated during mycelial differentiation C_LIO_LILiquid and solid culture conditions affects mycelial differentiation C_LIO_LIRaman microspectroscopic analysis reveals localization profiles of avermectin C_LI

microbiology↗

bioRxiv2021

Raman microspectroscopy imaging analysis of extracellular vesicles (EVs) biogenesis by filamentous fungus Penicilium chrysogenum

Mechanism of production of extracellular vesicles (EVs) and their molecular contents are of great interest owing to their diverse roles in biological systems and are far from being completely understood. Even though, cellular cargo release mediated by EVs have been demonstrated in several cases, their role in secondary metabolite production and release remains elusive. In this study we investigate this aspect in detail using Raman micro-spectroscopic imaging. We provide considerable evidence to suggest that the release of antibiotic penicillin by filamentous fungus Penicillium chrysogenum involves EVs. Morphological modifications of the fungal body during biogenesis, changes in cell composition at the locus of biogenesis, and major molecular contents of the released EVs are also revealed in this study. ImportanceExtracellular vesicles (EVs) play a key role in cellular communications. EVs role in functioning of fungi are relatively less explored. Here we show selective enrichment of chemical contents at certain locations of mycelium of P. chrysogenum forming protruding regions. Secondary metabolite penicillin is excessively localized in them. We provide evidence to show that EVs are released from these protrusions. Raman imaging has been applied for molecular profiling of the mycelium and for characterizing chemical contents of the EVs. Our study suggests a possible general role of EVs in the release of antibiotics from the producing organisms.

cell biology↗

bioRxiv2020

Detection of Penicillin G Produced by Penicillium chrysogenum KF 425 in Vivo with Raman Microspectroscopy and Multivariate Curve Resolution-Alternating Least Squares Methods

Raman microspectroscopy is a minimally invasive technique that can identify molecular structure without labeling. In this study, we demonstrate in vivo detection of the bioactive compound penicillin G inside Penicillium chrysogenum KF425 fungus cells. Highly overlapped spectroscopic signatures acquired using Raman microspectroscopic imaging are analyzed using a multivariate curve resolution-alternating least squares (MCR-ALS) method to extract the pure spectra of individual molecular constituents. In addition to detecting multiple constituents such as proteins and lipids, we observe the subcellular localization of penicillin G like granule particle inside the fungus body. To date, there have been no reports of direct visualization of intracellular localization of penicillin G. The methodology we present in this article is expected to be applied as a screening tool for the production of bioactive compounds by microorganisms.

microbiology↗

bioRxiv2017

Multiple strategies for heat adaptation in rice endosperms revealed by on-site cell-specific analysis

Plant cells have multiple strategies to adapt to environmental stresses. Rice endosperms form chalkiness in a part of the tissue under heat conditions during the grain-filling stage, although nitrogen supply reduces chalky rice. Air spaces formed in the cells cause an irregular light reflection and create chalkiness, yet what exactly occurs remains unclear at cell level. Through on-site cell-specific analysis, we show that heat-treated cells adjust osmotically and retard protein synthesis to preserve protein storage vacuoles in the cytosol, resulting in air space formation. Application of nitrogen enhances heat tolerance to sustain protein body and amyloplast development during strong osmotic adjustment, which diminishes air spaces to avoid chalkiness. Hence, we conclude that rice endosperm cells could alter organelle compartments spatially during the heat adaptation, depending on the available nitrogen level. Our findings provide new insight into the cellular mechanism of rice chalky formation as a strategy for heat acclimation.

plant biology↗