Biology subjects

Higashitani, N.

Publications and source records attributed to Higashitani, N..

4 recordsLinked to original sources

bioRxiv2026

Microgravity affects the nervous system and aging in C. elegans through reduced tactile stimulation

Space travel is becoming accessible, yet our understanding of how space environment and microgravity ({micro}G) affect biology, physiology, and health remains incomplete. We investigated {micro}G effects on neuromuscular development and aging in Caenorhabditis elegans. Nematodes in {micro}G showed downregulation of genes related to synaptic signaling, dopamine response, locomotion, and cuticle development, with impaired synaptic vesicle dynamics, reduced motility, and shorter body lengths. Aged worms in {micro}G showed decreased collagen gene expression, increased motor neuron defects, synaptic vesicle accumulation and decreased release, and mitochondrial morphology collapse in body wall muscles, indicating accelerated aging. MEC-4 mechanoreceptor was identified as a key mediator of {micro}G-induced body length reduction and changes in extracellular matrix gene expression. {micro}G conditions suppressed mechanoreceptor genes, suggesting multiple mechanosensory systems are affected. Physical stimulation through culture medium with small beads in space mitigated many {micro}G-induced expression changes, including mechanoreceptors, neuromuscular defects, and aging-related phenotypes. These results highlight mechanical stimulis role in maintaining neuromuscular integrity during spaceflight and suggest restoring tactile input could counter health risks from reduced stimulation in long-term space missions. SIGNIFICACEWe found that microgravity ({micro}G) conditions suppress the expression of multiple mechanoreceptor genes in Caenorhabditis elegans, indicating that several mechanosensory systems are affected during spaceflight. Importantly, reintroducing physical stimulation by adding small beads to the culture medium in space partially reversed many of these {micro}G-induced gene expression changes. This intervention also mitigated neuromuscular defects and aging-related phenotypes observed under {micro}G conditions. Collectively, these findings underscore the essential role of mechanical stimuli in preserving neuromuscular integrity during space missions and suggest that restoring tactile input may be a promising strategy to counteract the health risks associated with reduced tactile stimulation during prolonged spaceflights.

systems biology↗

bioRxiv2025

Actin cytoskeletal remodeling requires the interaction between Solo and LARG in response to substrate stiffness

In response to external mechanical stimuli, cells remodel their actin cytoskeleton. Solo, a Rho guanine nucleotide exchange factor (RhoGEF), is involved in mechanical stress responses. Using BioID, we identified PDZ-RhoGEF (PRG), a member of the RGS-RhoGEF family (regulator of G protein signaling domain-containing RhoGEFs, as a Solo-interacting protein. Moreover, we found that Solo regulates PRG during the mechanical stress response. Furthermore, we identified leukemia-associated RhoGEF (LARG), another RGS-RhoGEF member, as a Solo-interacting protein; however, the functional role of this interaction remains unknown. Therefore, in this study, we investigated the interaction between Solo and LARG and found that LARG localizes to Solo accumulation sites at the basal plane and that LARG is required for Solo-induced actin polymerization. Additionally, Solo is required to maintain LARG activity in cells, and this interaction is related to actin regulation in response to substrate stiffness. We further investigated the relationship between LARG and PRG as a function of Solo. We noted that although they did not competitively localize at Solo accumulation sites, knockdown of either PRG or LARG suppressed Solo-induced actin polymerization to the same extent as double knockdown, indicating that these signaling pathways cooperatively regulate Solo-induced actin polymerization.

cell biology↗

bioRxiv2023

Interaction between Solo and PDZ-RhoGEF is involved in actin cytoskeletal remodeling and response to substrate stiffness

Recent findings indicate that Solo, a RhoGEF, is involved in cellular mechanical stress responses. However, the mechanism of actin cytoskeletal remodeling via Solo remains unclear. Therefore, this study was aimed at identifying Solo-interacting proteins using the BioID, a proximal-dependent labeling method and elucidating the molecular mechanisms of function of Solo. We identified PDZ-RhoGEF (PRG) as a Solo-interacting protein. PRG co-localized with Solo in the basal area of cells, depending on Solo localization, and enhanced actin polymerization at Solo accumulation sites. Additionally, Solo and PRG interaction was necessary for actin cytoskeletal remodeling and RhoA activation. Moreover, overexpression of the binding domains of Solo and PRG had a dominant-negative effect on actin polymerization and actin stress fiber formation in response to substrate stiffness. Therefore, Solo restricts the localization of PRG and regulates actin cytoskeletal remodeling in synergy with PRG in response to the surrounding mechanical environment.

cell biology↗

bioRxiv2022

A stratagem for primary root elongation under moderate salt stress in the halophyte Schrenkiella parvula

Halophytes are salt-tolerant plants that grow in soil or waters of high salinity. Schrenkiella parvula is one of the halophyte plants that grow around Tuz (Salt) Lake, TURKEY that can survive at 600 mM NaCl. Intriguingly, S. parvula belongs to the same Brassicaceae family as the model plant Arabidopsis thaliana, and its genome is 90% homologous to the Arabidopsis genome. Here, we performed proteomic analysis and physiological studies on the roots of S. parvula seedlings cultivated under a moderate salt condition at 100 mM NaCl. Surprisingly, under 100 mM NaCl conditions, the primary roots elongated much faster than under NaCl-free conditions, although up to 200 mM those were reduced. On the other hand, iso-osmotic mannitol did not promote primary root elongation, suggesting a specific response to NaCl. Epidermal cell elongation was promoted in the elongation zone, but meristem size and DNA replication were decreased. In addition, root hair formation and lateral root elongation were suppressed at moderate salinity. Compared with A. thaliana, the cell death and ROS increase of root tip meristem cells under 100 mM NaCl condition were significantly lower in S. parvula seedlings. The size and starch content of sedimentary amyloplasts/statoliths in columella cells decreased, and gravitropism of primary roots was partially reduced. Gene expression analyses showed that the expression of auxin response and biosynthesis genes IAA1, IAA2, TAA1 and YUC8 were repressed and the SOS1 gene was upregulated two-fold in roots grown under moderate salt conditions. Proteomic analysis showed that co-chaperone and activator of HSPs such as Hop2 and Aha1 domain-containing protein orthologs were upregulated. Moreover, several secondary metabolic process-related proteins, antioxidant proteins, stress response proteins and proline catabolic process-related proteins were also increased. In contrast, enzymes associated with root hair elongation and nucleotide and protein syntheses were downregulated. These changes in auxin-related physiological responses, root architecture, lower ROS signaling, and stress-related protein expression promote primary root penetration into lower-salinity deeper soils as an adaptation of S. parvula.

plant biology↗