Biology subjects

Masuda, A.

Publications and source records attributed to Masuda, A..

8 recordsLinked to original sources

bioRxiv2026

Early detection of pancreatic ductal adenocarcinoma by single-molecule profiling of pancreatic enzyme activities

Pancreatic ductal adenocarcinoma (PDAC) remains a leading cause of cancer-related mortality, largely due to diagnosis at advanced stages. Early detection through minimally invasive liquid biopsy holds promise for improving patient outcomes. Here, we report a blood-based liquid biopsy platform based on single-molecule enzyme activity profiling (SEAP), which detects proteoform-level alterations in circulating pancreatic enzymes at single-molecule resolution. Using a tissue-centric biomarker discovery strategy, we identified activity signatures of pancreas-specific digestive enzymes associated with PDAC. A combinatorial classifier detected PDAC (stage I-IV) with 95.5% specificity and 75.0% sensitivity (74.2% for stage I-II) across 690 blood samples collected from multiple hospitals and biobanks. Performance was further validated in an independent cohort enriched for early-stage disease, where 54.2% (13/24) of stage IA, 64.3% (9/14) of stage IB, and 21.4% (3/14) of stage 0 lesions were classified as positive. These findings support the clinical potential of SEAP for early detection of PDAC.

biochemistry↗

bioRxiv2025

Baculovirus-mediated gene transfer enables functional expression of PIEZO1 ion channel in isolated muscle satellite cells

Primary tissue stem cells are useful not only for basic cell biological research but also for therapeutic applications: however, their broader utility is often limited by technical challenges, such as a low efficiency of exogenous gene expression. PIEZO1 is a large mechanosensitive ion channel that plays an important role in muscle-resident stem cells, known as muscle satellite cells (MuSCs), during muscle regeneration. In this study, we developed a method for the ectopic expression of PIEZO1 in isolated MuSCs. Using a baculovirus vector system, we expressed PIEZO1 in myoblast C2C12 cells. Following optimization of the infection condition, we achieved robust PIEZO1 expression in isolated MuSCs during activated and differentiated states, with appropriate subcellular localization and ion channel activity. Importantly, the baculovirus-mediated PIEZO1 expression restored the reduced proliferative capacity of Piezo1-deficient MuSCs to a level comparable to wild-type cells, indicating that the exogenously expressed PIEZO1 is functionally equivalent to the endogenous protein. Overall, we established an efficient method for the transfer of the Piezo1 gene into isolated MuSCs, which should provide a versatile platform to study other large proteins in MuSCs. Summary StatementA baculovirus-based method was developed, enabling robust and functional PIEZO1 expression in isolated muscle satellite cells and providing a platform to study large proteins in isolated stem cells.

cell biology↗

bioRxiv2024

Characterization of high affinity IgM and IgG monoclonal antibodies against norovirus variants GII.4 and GII.17

Human norovirus, a leading cause of viral gastroenteritis, results in significant global health and economic burden, requiring sensitive and accurate diagnosis and effective therapeutics and vaccines. In this study, we immunized mice with the virus like capsid particles of GII.4, a mainstream strain, and GII.17, a modern strain that began to circulate in 2014, and used hybridoma technology to generate hybridoma cells that produce norovirus-binding antibodies against GII.4 and GII.17, respectively. Selection of these hybridoma cells yielded monoclonal IgG and IgM antibodies against these strains. Characterization of these antibodies revealed that avidity effect by multivalent binding is necessary for IgM to bind to norovirus at high efficiency, while IgG achieve high affinity even by monovalent binding. Surface plasmon resonance and ELISA data suggest that the high density of antigen protrusion domain in the norovirus capsid, containing approximately protomers, facilitates IgM to bind to norovirus capsid with high efficiency.

biochemistry↗

bioRxiv2024

Low microbial abundance and community diversity within the egg capsule of the oviparous cloudy catshark (Scyliorhinus torazame) during oviposition

Vertebrate embryos are protected from bacterial infection by various maternally derived immune factors before the embryonic organs are fully developed. However, the defense mechanisms employed by elasmobranch embryos during development remain poorly understood. This study attempted to elucidate the embryonic defense mechanism of elasmobranchs by investigating the intracapsular environment of freshly laid eggs of the oviparous cloudy catshark (Scyliorhinus torazame). The egg capsule of oviparous elasmobranchs is tightly sealed until pre-hatching (early opening of the egg capsule), after which seawater flows into the capsule and the embryos are consequently exposed to the surrounding seawater. We first experimentally examined the resistance of embryos to potential bacterial infections and found that the early embryos were highly vulnerable to environmental pathogens, suggesting that the embryos are protected from the threat of infection before pre-hatching. Indeed, the intracapsular environment of freshly laid eggs exhibited a significantly low bacterial density that was maintained until pre-hatching. Furthermore, the microbiome inside eggs just after oviposition differed markedly from the microbiomes of rearing seawater and adult oviducal gland epithelia; these eggs were predominantly populated by an unidentified genus of Sphingomonadaceae. Overall, this study provides compelling evidence that early embryos of oviparous cloudy catshark are incubated in a clean intracapsular environment that potentially plays a significant role in embryonic development in oviparous elasmobranchs. Our results suggest that maintenance of this clean condition might be attributable to bactericidal or bacteriostatic activities associated with the egg jelly and/or oviducal gland.

microbiology↗

bioRxiv2023

RNPS1 in PSAP complex controls cyclical pre-mRNA splicing over the cell cycle

Cell cycle progression requires periodic gene expression through splicing control. However, the splicing factor that directly controls this cell cycle-dependent splicing remain unknown. Cell cycle-dependent expression of the AURKB (aurora kinase B) gene is essential for chromosome segregation and cytokinesis. We previously reported that RNPS1 is essential to maintain precise splicing in AURKB intron 5. Here we show that RNPS1 plays this role in PSAP complex with PNN and SAP18, but not ASAP complex with ACIN1 and SAP18. Whole-transcriptome sequencing of RNPS1- and PNN-deficient cells indicated that RNPS1, either alone or as PSAP complex, is an essential splicing factor for a subset of introns. Remarkably, protein expression of RNPS1, but not PNN, is coordinated with cyclical splicing in PSAP-controlled introns including AURKB intron 5. The ubiquitin-proteasome pathway is involved in the periodic decrease of RNPS1 protein level. RNPS1 is a key factor that controls periodic splicing during the cell cycle. O_FIG O_LINKSMALLFIG WIDTH=185 HEIGHT=200 SRC="FIGDIR/small/567984v3_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@84475dorg.highwire.dtl.DTLVardef@693637org.highwire.dtl.DTLVardef@16678feorg.highwire.dtl.DTLVardef@917ee0_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIThe AURKB gene encodes a protein kinase essential for cytokinesis and cell cycle C_LIO_LIPSAP complex (RNPS1, PNN, SAP18) is required for precise splicing in AURKB intron 5 C_LIO_LIRNPS1 protein in PSAP complex controls periodical splicing during the cell cycle C_LIO_LICyclical decrease of RNPS1 protein is mediated by the ubiquitin-proteasome pathway C_LI

molecular biology↗

bioRxiv2022

Nhlh1 and Nhlh2, a global transcriptional mechanism regulating commissural axon projection via activating Robo3

SUMMARYCommissural neurons are highly heterogeneous in their developmental origins, neurotransmitter type and function, but all share the common feature of projecting axons across the midline. The floor plate-crossing commissural axons in mammals, from the spinal cord to the midbrain, are guided by a conserved molecular mechanism relying primarily on Netrin-1/DCC/Robo3 signaling. Up to date, we know very little about the upstream transcriptional program that specify commissural axon laterality, neither do we know if a common mechanism operates in all commissural neurons. Here, we identified a pair of highly related helix-loop-helix transcription factors, Nhlh1 and Nhlh2, as a global transcriptional mechanism that controls the laterality of all floor plate-crossing commissural axons. Forced expression of Nhlh1/2 induce ectopic Robo3 expression and contralateral axon projections. And mutant mice deficient in both genes show a remarkable reduction in Robo3 expression and a total lack of ventral commissures from the spinal cord to the midbrain. This global mechanism may interact with neuron type specific mechanism to achieve specific generation of commissural circuits.

neuroscience↗

bioRxiv2022

Toxicity of House Cricket (Acheta domesticus) in Mice

There is an urgent need to address the shortage of animal protein due to food shortages caused by the global population growth. Crickets contain an abundance of proteins in their exoskeleton and muscles and have attracted attention as a new protein source; however, their safety as a food source has not been confirmed. We evaluated the toxicity of the House cricket (Acheta domesticus), on cells and mammals. In genotoxicity in vitro, cricket powder was added to Chinese hamster lung CHL-IU cells at concentrations of 5,000 {micro}g/mL, and the rate of chromosomal aberrations was assessed. In genotoxicity in vivo, mice were orally administered up to 2,000 mg/kg of cricket powder for 2 days. In both tests, cricket powder did not show any toxic effect. A repeated oral toxicity study was performed administering up to 3,000 mg/kg of cricket powder or control (saline) for 14 or 90 consecutive days and measuring body weight changes, blood biochemistry, blood properties, and organ weights. In each time course, there were no differences in there parameters between the control and cricket powder treated groups. These results suggest that House crickets ([≤]3,000 mg/kg) are not toxic to cells and organisms.

pharmacology and toxicology↗

bioRxiv2018

The hippocampus encodes delay and value information during delay-discounting decision making

The hippocampus, a region critical for memory and spatial navigation, has been implicated in delay discounting, the decline in subjective reward value when a delay is imposed. However, how delay discounting is encoded in the hippocampus is poorly understood. Here we recorded from the hippocampal CA1 region of mice performing a delay-discounting decision-making task, where delay lengths and reward amounts were changed across sessions, and identified subpopulations of neurons in CA1 which increased or decreased their firing rate during long delays. The activity of both delay-active and -suppressive cells reflected delay length, reward amount, and arm position, however manipulating reward amount differentially impacted the two populations, suggesting distinct roles in the valuation process. Further, genetic deletion of NMDA receptor in hippocampal pyramidal cells impaired delay-discount behavior and diminished delay-dependent activity in CA1. Our results suggest that distinct subclasses of hippocampal neurons concertedly support delay-discounting decision in a manner dependent on NMDA receptor function.

neuroscience↗