Biology subjects

Yokota, S.

Publications and source records attributed to Yokota, S..

9 recordsLinked to original sources

bioRxiv2026

A vagal sensory pathway for satiety suppression by intestinal fructose

Mammals primarily use glucose as an energy source, but they can also utilize other isocaloric monosaccharides, such as galactose and fructose. Since the gustatory system cannot distinguish between different sugars in ingested foods, it remains unclear whether and how mammals control the intake of different monosaccharides. Here we perform in vivo calcium imaging of the nodose ganglion in mice and find that intestinal glucose and fructose activate distinct populations of vagal sensory neurons. While glucose suppresses food intake in fed mice, fructose does not, resulting in increased calorie intake. However, after vagotomy, both glucose and fructose suppressed food intake, suggesting that vagal circuits activated by fructose facilitate feeding. This specialized vagal sensory pathway for fructose may partly explain the excess calorie intake induced by a fructose-rich diet.

neuroscience↗

bioRxiv2026

TACE reprograms RANKL-mediated differentiation of macrophages by activating the non-canonical pathway of IRF3

Inflammation is associated with an influx of inflammatory macrophages and increased activation and differentiation of osteoclasts. Receptor activator of NF-kB ligand (RANKL) is a key driver for osteoclast differentiation. However, the pathogenic mechanisms augmenting RANKL-induced osteoclast differentiation in inflammatory conditions are not fully elucidated. Here, we show that TNF- converting enzyme (TACE) plays a critical role in pathological bone erosion and enhances osteoclast differentiation in inflammatory conditions. Myeloid cell-specific TACE deletion in a murine arthritis model attenuates joint inflammation and bone destruction. TACE deficiency suppresses distal RANKL signaling in macrophages by increasing IRF3 activation, while enhancing proximal RANKL signaling, leading to the suppression of osteoclast differentiation. Mechanistically, IRF3 activation limits macrophage reprogramming by suppressing NFATc1 and HB-EGF in response to RANKL through a non-canonical pathway. HB-EGF, a TACE substrate, activates EGFR signaling and promotes osteoclastogenesis by inhibiting IRF3 activation. TACE regulates the reciprocal inhibition of the IRF3-HBEGF axis. Our study highlights a role for TACE as a rheostat, balancing both pro- and anti-osteoclastogenic signals.

cell biology↗

bioRxiv2025

Genome-edited retinal organoids restore host bipolar connectivity in the primate macula

Retinal organoids (ROs) represent a promising regenerative strategy for restoring vision in retinal degenerative diseases, but whether host cone bipolar cells (BCs) in the primate macula can rewire with transplanted photoreceptors remains unresolved. Here, we transplanted genome-edited human retinal organoids lacking ON-BCs (Islet-1-/- ROs) into a non-human primate macular degeneration model. Remarkably, host rod and cone BCs extended dendrites toward grafted photoreceptors, forming functional synapses confirmed by immunohistochemistry, ultrastructural imaging, and focal macular electroretinography. Both ON- and OFF-pathway connectivity was rebuilt, providing the first demonstration of host-graft synaptic integration in the primate macula. These results establish that primate cone circuits retain a surprising capacity for rewiring and highlight genome-edited ROs as a powerful platform for vision restoration. Our findings represent a critical translational step toward stem cell-based therapies capable of repairing central vision in patients with advanced macular degeneration.

neuroscience↗

bioRxiv2024

A FRET assay to quantitate levels of the human β-cardiac myosin interacting heads motif based on its near-atomic resolution structure

In cardiac muscle, many myosin molecules are in a resting or "OFF" state with their catalytic heads in a folded structure known as the interacting heads motif (IHM). Many mutations in the human {beta}-cardiac myosin gene that cause hypertrophic cardiomyopathy (HCM) are thought to destabilize (decrease the population of) the IHM state. The effects of pathogenic mutations on the IHM structural state are often studied using indirect assays, including a single-ATP turnover assay that detects the super-relaxed (SRX) biochemical state of myosin functionally. Here we develop and use a fluorescence resonance energy transfer (FRET) based sensor for direct quantification of the IHM state in solution. The FRET sensor was able to quantify destabilization of the IHM state in solution, induced by (a) increasing salt concentration, (b) altering proximal S2 tail length, or (c) introducing the HCM mutation P710R, as well as stabilization of the IHM state by introducing a dilated cardiomyopathy-causing mutation (E525K). Our FRET sensor conclusively showed that these perturbations indeed alter the structural IHM state. These results establish that the structural IHM state is one of the structural correlates of the biochemical SRX state in solution.

biophysics↗

bioRxiv2023

Testis organ culture system capable of evaluating testicular toxicity

Successful treatment of pediatric cancers often results in long-term health complications, including potential effects on fertility. Therefore, assessing the male reproductive toxicity of anti-cancer drug treatments and the potential for recovery is of paramount importance. However, in vivo evaluations are time-intensive and require large numbers of animals. To overcome these constraints, we utilized an innovative organ culture system that supports long-term spermatogenesis by placing the testis tissue between a base agarose gel and a polydimethylsiloxane ceiling, effectively mirroring the in vivo testicular environment. The present study aimed to determine the efficacy of this organ culture system for accurately assessing testicular toxicity induced by cisplatin, using acrosin-green fluorescent protein (GFP) transgenic neonatal mouse testes. The testis fragments were treated with different concentrations of cisplatin-containing medium for 24 hours and incubated in fresh medium for up to 70 days. The changes in tissue volume and GFP fluorescence over time were evaluated to monitor the progression of spermatogenesis, in addition to the corresponding histopathology. Cisplatin treatment caused tissue volume shrinkage and reduced GFP fluorescence in a concentration-dependent manner. Recovery from testicular toxicity was also dependent on the concentration of cisplatin received. The results demonstrated that this novel in vitro system can be a faithful replacement for animal experiments to assess the testicular toxicity of anti-cancer drugs and their reversibility, providing a useful method for drug development. Short AbstractAssessing the male reproductive toxicity of anti-cancer drugs and the potential for recovery is of paramount importance, however, in vivo evaluations are time-intensive and require large numbers of animals. We utilized an innovative organ culture system that mirrors the in vivo testicular environment to determine its efficacy in accurately assessing testicular toxicity induced by cisplatin. The results demonstrate that this system can be a faithful replacement for animal experiments to assess the testicular toxicity of anti-cancer drugs and their reversibility.

developmental biology↗

bioRxiv2023

Reactive blue dye detects male reproductive toxicity

BackgroundReactive blue 2 (RB2) dye specifically binds to the nuclei of human spermatozoa under weakly alkaline conditions, thus providing a new method to assess sperm quality. However, this technique has not yet been applied to other mammalian species, such as well-established rodent models, which could enable evaluation of the male reproductive toxicity of drug candidates in non-clinical studies. ObjectivesWe aimed to evaluate the usefulness of RB2 staining in assessing testicular and epididymal sperm toxicity in mice using a busulfan-induced infertility model. MethodsMale C57BL/6J mice were intraperitoneally administered 40 mg/kg of busulfan. After 28 days, the testes and epididymis were collected and stained with RB2 at pH 10. In vitro evaluations were conducted on uncoated glass slides with RB2 mixed with either protamines extracted from the spermatozoa or intracellular protein components from somatic cells without protamines. ResultsFollowing peanut agglutinin (PNA) lectin histochemistry, RB2-positive cells were observed in elongating and elongated spermatids at all stages except for stages IX-XI of the seminiferous epithelium. After busulfan administration, the proportion of RB2-positive germ cells in the seminiferous tubules decreased significantly, and no RB2-positive spermatozoa were found in the caput epididymis of treated mice. Aggregates were observed in the mixture of RB2 dye (pH 10) with protamines but not in the mixture of intracellular protein components without protamines, and this specificity was lost at neutral pH. Discussion and ConclusionOur study demonstrates that RB2 specifically stains steps 12-16 spermatids, indicating specific binding to protamine expressed in these spermatids. The RB2 staining technique has potential as a biomarker for male reproductive toxicity, allowing for the rapid visualization of protamination.

pharmacology and toxicology↗

bioRxiv2023

Dentate neurogenesis mediates cognitive flexibility via modulation of the hippocampal longitudinal-axis network

Adult neurogenesis endows the hippocampus with unparalleled neural plasticity, essential for intricate cognitive functions. However, the manner in which sparse newborn neurons (NBNs) modulate neural activities and subsequently shape behavior remains enigmatic. Utilizing a newly engineered NBN-Tetanus Toxin mouse model, we non-invasively silenced NBNs and confirmed their crucial role in cognitive flexibility, as demonstrated through reversal learning in the Morris water maze and the Go/Nogo task in operant learning. Pairing task-based functional MRI (tb-fMRI) with operant learning revealed a dorsal hippocampal hyperactivation during Nogo task, implying that hippocampal hyperexcitability might underlie the observed behavioral deficits. Notably, resting-state fMRI (rs-fMRI) revealed enhanced functional connectivity between the dorsal and ventral dentate gyrus following NBN silencing. Further exploration of PV+ interneurons and mossy cells activities highlighted NBNs integral part in preserving the excitation/inhibition balance within the hippocampus. Our findings emphasize how the neural plasticity driven by NBNs extensively modulates the hippocampus, sculpting cognitive flexibility.

neuroscience↗

bioRxiv2022

Development of a non-invasive method for testicular toxicity evaluation using a novel compact magnetic resonance imaging system

In non-clinical animal studies for drug discovery, histopathological evaluation is the most powerful tool to assess testicular toxicity. However, histological analysis is extremely invasive; many experimental animals are needed to evaluate changes in the pathology and anatomy of the testes over time. As an alternative, small animal magnetic resonance imaging (MRI) offers a non-invasive methodology to examine testicular toxicity without radiation. The present study demonstrated the suitability of a new, ready-to-use compact MRI platform using a high-field permanent magnet to assist with the evaluation of testicular toxicity. To validate the utility of the MRI platform, male mice were treated with busulfan (40 mg/kg, intraperitoneal injection). Tenty-eight days after treatment, both testes in busulfan-treated and control mice (n = 3/group) were non-invasively scanned in situ by MRI at 1 tesla. On a T1-weighted, 3D gradient-echo MRI sequences (voxel size: 0.23 x 0.23 x 0.50 mm), the total testicular volume in busulfan-treated mice was significantly smaller than in controls. On T1-weighted images, the signal intensity of the testes was significantly higher in busulfan-treated mice than in controls. The mice were sacrificed, and the testes were isolated for histopathological analysis. The weight of the testes in busulfan-treated mice significantly decreased, similar to the results of the non-invasive analysis. Additionally, periodic acid-Schiff stain-positive effusions were observed in the interstitium of the busulfan-treated mouse testes, potentially explaining T1 shortening due to a high concentration of glycoproteinaceous content. The present data demonstrated a rapid evaluation of testicular toxicity in vivo by compact MRI.

pharmacology and toxicology↗

bioRxiv2021

Argonaute Binding within Human Nuclear RNA and its Impact on Alternative Splicing

Mammalian RNA interference (RNAi) is often linked to the regulation of gene expression in the cytoplasm. Synthetic RNAs, however, can also act through the RNAi pathway to regulate transcription and splicing. While nuclear regulation by synthetic RNAs can be robust, a critical unanswered question is whether endogenous functions for nuclear RNAi exist in mammalian cells. Using enhanced crosslinking immunoprecipitation (eCLIP) in combination with RNA sequencing (RNAseq) and multiple AGO knockout cell lines, we mapped AGO2 protein binding sites within nuclear RNA. The strongest AGO2 binding sites were mapped to micro RNAs (miRNAs). The most abundant miRNAs were distributed similarly between cytoplasm and nucleus, providing no evidence for mechanisms that facilitate localization of miRNAs in one compartment versus the other. Beyond miRNAs, most statistically-significant AGO2 binding was within introns. Splicing changes were confirmed by RT-PCR and were recapitulated by synthetic duplex RNAs and miRNA mimics complementary to the sites of AGO2 binding. These data support the hypothesis that miRNAs can control gene splicing. While nuclear RNAi proteins have the potential to be a natural regulatory mechanism, careful study will be necessary to identify critical RNA drivers of normal physiology and disease.

molecular biology↗