Biology subjects

TSUBOI, T.

Publications and source records attributed to TSUBOI, T..

4 recordsLinked to original sources

bioRxiv2026

Green genetically encoded IP3 biosensor for hierarchical analysis of its signaling network

Inositol 1,4,5-trisphosphate (IP3) is a key second messenger that regulates diverse physiological processes. Visualization of IP3 dynamics in living cells is therefore important for understanding its signaling processes. In this study, we developed genetically encoded green fluorescent IP3 biosensors named Green iPenguins with distinct half-maximal effective concentrations (EC50) for IP3, enabling detection of IP3 signals over a range of concentrations. The biosensors displayed more than a 4-fold increase in fluorescence intensity upon IP3 and showed high specificity for IP3 over structurally related molecules. When expressed in HEK293T cells, the biosensors enabled visualization of IP3 dynamics involved in different signaling pathways. They were also compatible with dual-color imaging, allowing simultaneous monitoring of IP3 together with cAMP or Ca2+ signals. In addition, the hierarchical relationship between IP3 and Ca2+ signaling was visualized, providing insight into the temporal relationship between these two second messengers. The biosensors are expected to facilitate future studies of physiological processes involving IP3 signaling networks.

bioengineering↗

bioRxiv2025

Genome-wide identification and characterization of QTLs for transcriptional noise in human midbrain cells

Not only the abundance of gene expression but also its cell-to-cell variation, referred to as "transcriptional noise", is known to have certain biological significance. However, the mechanistic basis of transcriptional noise, particularly how it is regulated by genetic variants, remains elusive. In this study, we analyzed single-cell RNA sequencing (scRNA- seq) data of human induced pluripotent stem cell (iPSC)-derived midbrain cells (795,661 cells in 17 conditions) from 155 individuals with their genotypes to perform genome-wide mapping of quantitative trait loci for transcriptional noise (tnQTLs). Our analyses controlling for confounding factors such as gene expression abundance identified a total of 101,024 significant tnQTL-gene pairs. A comparison with QTLs for expression levels (i.e. eQTLs) detected by an equivalent pipeline revealed that the majority (81%) of tnQTLs were also identified as eQTLs, while no significant eQTL effects were observed in the others, and a small portion (7%) of eQTLs were with significant tnQTL effects. The tnQTLs and eQTLs showed distinctive patterns of sharing across cellular conditions, where tnQTL effects were often more condition-specific than those of eQTLs. In particular, tnQTLs without significant eQTL effects (termed tn>eQTLs) were dramatically altered by rotenone-induced oxidative stress. The tn>eQTLs also exhibited unique patterns of enrichment in various functional genomic elements, such as being frequently observed in promoters of non-QTL target genes. In the analysis using summary statistics from genome-wide association studies (GWAS) for various human complex traits, we found nominally significant enrichment of heritability for schizophrenia in tn>eQTLs. Possible contributions of tn>eQTLs to schizophrenia risk were supported by the enrichment of association signals in their target genes. We also identified genes whose transcriptional noise was implicated to be causally associated with a trait by a Mendelian randomization analysis, including HLA genes and YWHAE associated with multiple autoimmune/psychiatric disorders. To further explore the role of transcriptional noise dysregulation in disease, we analyzed scRNA-seq data from human schizophrenia and mouse model brains. Genes exhibiting differential transcriptional noise between cases and controls, i.e. differentially noisy genes (DNGs), were particularly abundant in the superficial and deep layer excitatory neurons, where association signals in schizophrenia GWAS were also enriched in their DNGs. Overall, our comprehensive mapping of tnQTLs provides a resource for a new class of regulatory genetic variants, deepens our understanding of the mechanistic basis of how genetic variants regulate transcriptional noise, and highlights the roles of tnQTLs and transcriptional noise dysregulation in human complex traits.

genetics↗

bioRxiv2024

Immediate glucose signaling transmitted via the vagus nerve in gut-brain neural communication

Sucrose consumption is influenced by certain gut-brain signaling mechanisms. Among these, one pathway involves neuropod cells, which form synaptic connections with the vagus nerve, leading to the immediate activation of central dopaminergic pathways. This study explored the role of the frontal cortex in its process. We found that the vagus nerves immediate activation is mediated by the sodium-glucose cotransporter 1 (SGLT1) of neuropod cells after the intragastric glucose injection in mice. Also, we showed that the involvement of both astrocytes and neurons in the frontal cortex via D2 and D1 dopamine receptors, respectively, by in vivo Ca2+ imaging. Finally, we revealed that psychological stress, which induces a reduction in sucrose preference, significantly diminishes the activation levels of both the vagus nerve and the frontal cortex. These findings highlight the role of a comprehensive gut-brain network in modulating sucrose preference, involving neuropod cells, the vagus nerve, and the frontal cortex. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/586971v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@1f28baeorg.highwire.dtl.DTLVardef@b053a9org.highwire.dtl.DTLVardef@449431org.highwire.dtl.DTLVardef@5d3ad9_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2022

Exocytotic dynamics of glucagon-like peptide-1 from enteroendocrine L cell line is regulated by actin polymerization

Stimulus-secretion coupling of glucagon-like peptide-1 (GLP-1) from enteroendocrine L cells is important for glucose homeostasis. Although intracellular second messengers including Ca2+ and cAMP, and cellular structures including actin cytoskeleton play roles in induction of exocytosis of GLP-1 granules, little is known about the specific part in the process of exocytosis in which they are involved. Here we explored the role of those molecules by live-cell imaging with mouse L cell line GLUTag cells, and used two stimuli: deoxycholic acid (DCA) and high K+. DCA increased both intracellular Ca2+ and cAMP levels, while high K+ only increased Ca2+. We next monitored a single exocytosis of GLP-1 granules and found that, during the first 10 minutes of stimulation, both stimuli mainly induced the exocytosis from the predocked granules with the plasma membrane before stimulation or granules immediately fused to the plasma membrane without docking. Furthermore, inhibition of actin polymerization suppressed the proportion of exocytosis by the predocked granules. These results suggest that the exocytotic process of GLP-1 granules is determined by interaction with F-actin upon the increase of either Ca2+ or cAMP. Summary statementExocytotic process of glucagon-like peptide-1 granules from a mouse enteroendocrine L cell line is regulated by actin polymerization immediately after elevation of intracellular Ca2+ or cAMP levels.

cell biology↗