Proceedings of the Japan Academy. Series B, Physical and Biological Sciences最新文献

Adherent eukaryotic cells typically exhibit amoeboid locomotion through actin polymerization and bleb-driven mechanisms. However, testate amoebae, which enclose their bodies within a shell, exhibit variation in these locomotion types. This study focused on Arcella, a representative testate amoeba that pulls its shell using multiple pseudopods extending from a single aperture on the ventral side. Arcella is found in peatlands and freshwater, where it adapts its movement to various substrates. We characterized its movement on glass as well as hard, and soft gel substrates through detailed observation. The results indicated a higher randomness in motion on the soft gel, which was influenced by the pseudopodial elongation direction. Additionally, we evaluated the relationship between movement direction and traction stress. The dipole moment of the traction stress field determined the axis of motion, whereas quadrupole moments were correlated with forward and lateral movements. Although some relationships between multipole moments and velocity were shared with other cells, Arcella exhibited unique characteristics in its movement mechanism, which likely occurred due to its use of multiple pseudopods alongside its shell.

The pseudoautosomal region (PAR) of mammalian sex chromosomes is a small region of sequence identity shared by the X and Y chromosomes that allows pairing, crossover, recombination, and proper segregation of sex chromosomes. Although the mouse PAR sequence was largely a mystery, we have recently obtained the complete PAR sequences of the C57BL/6J and CAST/EiJ strains. Here, we report the complete PAR sequence of a Japanese wild mouse-derived strain, MSM/Ms, and compare the PARs of the three strains. There are considerable differences in the size of PARs between strains (MSM/Ms PAR is only about 20% the length of C57BL/6J PAR) and numerous amino acid substitution variants were found in the PAR genes. High GC-content exons and short introns are common features of the PAR genes and are likely a consequence of maintaining the functions of the encoded proteins during rapid evolution of the mouse PAR, whose recombination frequency in male meiosis is ∼100 times higher than the autosomal average.

BAF complexes are ATP-dependent chromatin remodelers that govern gene expression and cellular identity. The non-canonical BAF (ncBAF) complex, with BRD9 as its signature component, orchestrates chromatin remodeling essential for balanced hematopoiesis. BRD9 loss disrupts enhancer-promoter interactions and CTCF-mediated chromatin architecture, causing myeloid skewing, impaired lymphoid differentiation, and diminished hematopoietic stem cell (HSC) fitness-phenotypes recapitulating physiological aging. This mechanism underlies aging-related pathologies such as myelodysplastic syndromes (MDS), in which spliceosomal mutations in SF3B1 trigger aberrant BRD9 splicing and destabilize its mRNA. Remarkably, BRD9 exhibits context-dependent functions: its depletion consistently promotes differentiation and apoptosis in myeloid leukemias, contrasting its differential roles in myeloid differentiation in adult versus fetal hematopoiesis. Thus, BRD9 mechanistically links spliceosomal dysfunction to chromatin dysregulation, bridging aging-associated disease and malignant transformation through context-dependent roles. Among the diverse assemblies of BAF family, these findings position the BRD9-ncBAF axis as both a critical determinant of hematopoietic fate decisions and a promising therapeutic target in hematologic malignancies.

Inbred laboratory mice, such as the C57BL/6J strain, are presumed to be genetically uniform and are used in medical and biological research. Here, we report a substantial copy number variation (CNV) in a segmental duplication (SD) in the mouse pseudoautosomal region (PAR), which challenges the widely accepted assumption. The PAR consists of an identical sequence shared by the X and Y chromosomes at their distal ends, enabling proper pairing and recombination during meiosis. The copy number in C57BL/6J mice ranged from 4 to 27 per diploid genome. The mean (± standard deviation) was 12.9 ± 4.8. We found that de novo CNV emerged in nearly every spermatogenesis meiosis. The presence of CNV in the SD has also been detected in other classical inbred mouse strains. Each copy of the SD contains the Erdr1 gene. A correlation was observed between copy number and Erdr1 expression levels in males, and there was a significant negative correlation between expression level and body weight.

Spider silk has garnered significant attention across diverse research fields because of its remarkable physical and biological properties, which have driven extensive efforts to develop materials and fabrication processes that replicate its unique characteristics. This review focuses on the structure of silk fibers and the mechanisms that underlie their formation, with an emphasis on the hierarchical organization that contributes to their outstanding performance. Additionally, the biodegradability of silk proteins and their degradation products are discussed, and their potential for sustainable material design are highlighted.

Nyctinasty, a circadian-regulated leaf movement observed in legumes, has long intrigued scientists. This study identified genus-specific endogenous chemical factors, leaf-closing factors (LCFs) and leaf-opening factors (LOFs), that control this rhythmic behavior. In Samanea saman, a model for nyctinasty, the LCF 12-hydroxyjasmonic acid glucoside induces leaf-folding by selectively targeting extensor motor cells and activating reactive oxygen species (ROS)-dependent K⁺ efflux via the SPORK2 channel. Functional analyses revealed that SPORK2 and the SsSLAH1/SsSLAH3 anion channel complex are key effectors in the regulation of leaf movement. Remarkably, SPORK2 also functions as a temperature-sensitive K⁺ channel, inactivating at low temperatures to mediate rain-induced leaf folding, a phenomenon underlying the nickname "rain tree". These findings provide a chemical entry point to dissect the molecular machinery of nyctinasty and reveal a previously unrecognized role for plant K⁺ channels in temperature sensing.

Extranodal NK/T-cell lymphoma (ENKTL) is a rare, aggressive Epstein-Barr virus (EBV)-associated malignancy. The 5th edition of the WHO classification refined their nomenclature by removing "nasal type" and introducing related entities to reflect updated biological insights. This review synthesizes recent advances in epidemiology and molecular pathogenesis in ENKTL, highlighting recurrent driver gene alterations, particularly frequent mutations in X-linked genes such as DDX3X and MSN, alongside TP53 mutations and PD-L1 structural variations that facilitate immune evasion. We also discuss novel mouse models that replicate the ENKTL niche, revealing how Trp53 loss and the EBV oncoprotein LMP1 synergistically remodel the tumor microenvironment to promote lymphomagenesis. Therapeutically, while L-asparaginase-based regimens including SMILE and P-GemOx remain the standard of care, emerging immune checkpoint inhibitors have demonstrated encouraging efficacy, particularly in combination with chemotherapy. This review provides an integrated perspective on the evolving landscape of diagnosis, disease biology, and translational treatment strategies for NK/T-cell lymphoproliferative disorders.

Metagenomics has become a powerful approach for deciphering the structure and function of the human gut microbiome, a complex microbial ecosystem in the gut. The human gut microbiome plays a crucial role in health and disease through multifaceted interactions with various factors, including age, diet, lifestyle, and medications. This review summarizes key advances in gut microbiome research over the past two decades and presents several topics from a recent large-scale, data-driven study, specifically a cohort-based initiative, the Japanese 4D microbiome project. These include a population-level characterization of the Japanese gut microbiome in a global context through comparison with 31,695 gut metagenomes from 37 countries, as well as an extensive analysis of the effects of medications. This review provides new insights into the ecology and uniqueness of the Japanese gut microbiome and highlights the importance of large-scale, well-phenotyped cohorts in advancing microbiome science.

Advancements in living standards, medical technologies, and nutrition have contributed to the global increase in life expectancy. However, the widening gap between life expectancy and healthy life expectancy indicates that a growing population requires ongoing medical care and hospitalization. The development of a home-use telediagnostic system is a promising solution for improving the quality of life for patients and healthcare providers to extend a healthy lifespan and reduce the burden on clinicians. Such a system also holds the potential for rapid health assessments during emergency situations, where timely triage is critical. This study reviews recent progress in noninvasive, multimodal sensor patches capable of continuously monitoring vital signs and biomarkers via the skin. Furthermore, we explore the integration of machine learning for real-time, on-device data analysis as an edge system, enabling autonomous health feedback without reliance on the Internet. Although several technical challenges remain before practical implementation, these innovations may pave the way for a paradigm shift in conventional medical care.

This study assessed the feasibility of unconstrained deep-learning-based sleep stage classification using cardiorespiratory and body movement activities derived from piezoelectric sensors installed under a bed mattress. Heart and respiratory rates and their respective variabilities, cardiorespiratory coupling index, and body movement were simultaneously acquired through polysomnography (PSG) for 106 untreated participants with suspected sleep apnea. We used a bidirectional long short-term memory network to predict the five sleep stages using five different input feature combinations. The best performance was achieved with a model comprising six parameters, including cardiorespiratory variability features, with a balanced accuracy of 0.70 ± 0.05, Cohen's κ of 0.40 ± 0.11, and an F1 score of 0.63 ± 0.08. Deming regression and Bland-Altman analyses of the six major sleep parameters estimated by the model and those determined by PSG showed significant correlations (r = 0.426-0.781) with a low bias. These results demonstrate the effectiveness of the proposed approach and its potential to expand opportunities for in-home sleep monitoring.