Biology subjects

Kurokawa, Y.

Publications and source records attributed to Kurokawa, Y..

5 recordsLinked to original sources

bioRxiv2026

Highly plastic macrophage niches orchestrate acquired quiescence and reactivation in breast-cancer bone metastasis

Recurrence and metastasis remain major causes of cancer mortality, sustained by therapy-resistant micrometastatic cells. Bone is a frequent site of breast-cancer relapse, yet the cues that reawaken disseminated cells remain poorly defined. We identify a previously unrecognized, highly plastic CXCL16 macrophage population that integrates tumor-associated macrophage programs found in distant metastatic sites such as lung and brain with non-tumor disease-associated traits in bone marrow. These CXCL16 macrophages establish a transient niche that restrains disseminated cancer-cell proliferation. Single-cell transcriptomics delineate functional remodeling of myeloid niches within the bone metastatic microenvironment: a CXCL16 macrophage niche that transiently constrains metastatic growth, and G-CSF macrophage and neutrophil niches that reignite tumor outgrowth. In primary tumors, cancer-associated fibroblasts (CAFs) aberrantly secrete G-CSF in response to cancer-cell signals, expanding G-CSF-receptor-positive subset of cancer cells with high metastatic potential. In advanced human bone metastases, CXCL16 macrophages localize to CAF-rich stroma but are excluded from cancer-cell clusters, indicating immune evasion. Together, these findings uncover CAF-bone-marrow cross-talk as a therapeutic target linking stromal inflammation, immune remodeling, and metastatic progression.

cancer biology↗

bioRxiv2025

Submolecular video-imaging of the Smc5/6 complex topologically bound to DNA

Structural maintenance of chromosomes (SMC) complexes are ring-shaped ATPases that hold distinct DNA segments together to regulate various chromosome structures and functions. However, their dynamic mechanisms of DNA binding and processing remain poorly understood. Here, using high-speed atomic force microscopy, we directly visualized the dynamics of the Smc5/6 complex on DNA at submolecular resolution, resolving its individual domains. ATP-bound Smc5/6 stably binds DNA via the ATPase head domain, whereas following ATP hydrolysis, the DNA is entrapped within the SMC compartment and positioned around the opposite hinge domain. Furthermore, Smc5/6 topologically entraps two DNA segments together and stabilizes the DNA twist structures, promoting DNA compaction. Our findings provide a visual demonstration of how an SMC complex employs its ring architecture to facilitate distinct DNA binding modes.

biophysics↗

bioRxiv2022

Reconstituting human somitogenesis in vitro

The segmented body plan of vertebrates is established during somitogenesis, a well-studied process in model organisms, but remains largely elusive in humans due to ethical and technical limitations. Despite recent advances with pluripotent stem cell (PSC)-based approaches1-5, a system that robustly recapitulates human somitogenesis in both space and time remains missing. Here, we introduce a PSC-derived mesoderm-based 3D model of human segmentation and somitogenesis, which we termed Axioloids, that captures accurately the oscillatory dynamics of the segmentation clock as well as the morphological and molecular characteristics of segmentation and sequential somite formation in vitro. Axioloids show proper rostrocaudal patterning of forming segments and robust anterior-posterior FGF/WNT signaling gradients and Retinoic Acid (RA) signaling components. We identify an unexpected critical role of RA signaling in the stabilization of forming segments, indicating distinct, but also synergistic effects of RA and extracellular matrix (ECM) on the formation and epithelialization of somites. Importantly, comparative analysis demonstrates striking similarities of Axioloids to the human embryo, further validated by the presence of the HOX code in Axioloids. Lastly, we demonstrate the utility of our Axioloid system to study the pathogenesis of human congenital spine diseases, by using patient-like iPSC cells with mutations in HES7 and MESP2, which revealed disease-associated phenotypes including loss of epithelial somite formation and abnormal rostrocaudal patterning. These results suggest that Axioloids represent a promising novel platform to study axial development and disease in humans.

developmental biology↗

bioRxiv2020

Rrp1 translocase and ubiquitin ligase activities restrict the genome destabilising effects of Rad51 in fission yeast

Rad51 is the key protein in homologous recombination DNA repair and has important roles during DNA replication. Auxiliary factors regulate Rad51 activity to facilitate productive, and prevent inappropriate, recombination that could lead to genome instability. Previous genetic analyses identified a function for Rrp1 (a member of the Rad5/16-like group of SWI2/SNF2 translocases) in counteracting Rad51 activity, shared with the Rad51 mediator Swi5-Sfr1 and the Srs2 anti-recombinase. Here, we show that Rrp1 overproduction alleviates the toxicity associated with excessive Rad51 activity in a manner dependent on Rrp1 ATPase domain. Purified Rrp1 binds to DNA and has a DNA-dependent ATPase activity. Importantly, Rrp1 directly interacts with Rad51 and removes it from double-stranded DNA, confirming that Rrp1 is a translocase capable of modulating Rad51 activity. Additionally, we demonstrate that Rrp1 possesses E3 ubiquitin ligase activity with Rad51 as a substrate, suggesting that Rrp1 regulates Rad51 in a multi-tiered fashion.

genetics↗

bioRxiv2019

Real-time tracking reveals the catalytic process of Rad51-driven DNA strand exchange

During homologous recombination, Rad51 forms a nucleoprotein filament on single-stranded DNA to promote DNA strand exchange. This filament binds to double-stranded DNA (dsDNA), searches for homology, and promotes transfer of the complementary strand, producing a new heteroduplex. Strand exchange proceeds via two distinct three-strand intermediates, C1 and C2. C1 contains the intact donor dsDNA whereas C2 contains newly formed heteroduplex DNA. Here, we show that conserved DNA binding motifs, loop 1 (L1) and loop 2 (L2) in site I of Rad51, play distinct roles in this process. L1 is involved in formation of the C1 complex whereas L2 mediates the C1-C2 transition, producing the heteroduplex. Another DNA binding motif, site II, serves as the DNA entry position for initial Rad51 filament formation, as well as for second donor dsDNA incorporation. Our study provides a comprehensive molecular model for the catalytic process of strand exchange mediated by eukaryotic RecA family recombinases.

molecular biology↗