Biology subjects

Ichise, H.

Publications and source records attributed to Ichise, H..

5 recordsLinked to original sources

bioRxiv2025

Chromatin organizer ASCL1 governs gene programs in thymic epithelial cells, defining immunological self

Immunological self-tolerance depends on medullary thymic epithelial cells (mTECs), which express a broad repertoire of self-antigens to support negative selection of autoreactive T cells and the development of regulatory T cells. Although the autoimmune regulator AIRE is essential for this process, additional factors are required to establish the full mTEC gene expression program. Because thymoma is frequently associated with autoimmunity, implicating defective thymic tolerance, we performed single-cell RNA sequencing of TECs from thymoma patients and identified the transcription factor ASCL1 as selectively downregulated in tumor mTECs. Deletion of Ascl1 in mouse TECs resulted in spontaneous autoimmunity without inducing thymic tumorigenesis. Transcriptomic and chromatin accessibility analyses revealed that ASCL1 influences mTEC gene expression programs and is associated with corresponding changes in chromatin accessibility. Genetic interaction analyses further suggested that ASCL1 activity in immature mTECs modulates the AIRE dependency of gene expression in mature mTECs. Together, these findings identify ASCL1 as a key regulator of mTEC function and central tolerance, providing insight into mechanisms that safeguard immune homeostasis and whose disruption may contribute to autoimmune disease.

immunology↗

bioRxiv2025

Immune Niche Formation in Engineered Mouse Models Reveals Mechanisms of Tumor Dormancy

Residual tumor cells can persist in a dormant state during clinical remissions that may last decades. The mechanisms that lead to such growth control vs. eventual reactivation and macroscopic tumor outgrowth remain unclear. Here, we report data from a mouse model that reveals a key role of host immunity and the cellular and molecular mechanisms that control tumor dormancy. Abrogation of myeloid-specific TGF-{beta}RII expression (T{beta}RIImyeKO) resulted in an IFN-{gamma} rich immune microenvironment. IFN-{gamma} in turn elevated KLF4-mediated SLURP1 production in malignant cells, which is critical to the tumor cell quiescent state through interruption of fibronectin-integrin signaling pathways. The dormant tumor lesions were located in spatially localized immune niches rich in NK cells, cDCs, monocytes, and neutrophils, concomitant with tumor cell inactivation of NK cell immune surveillance through a CD200-CD200R1 mechanism. Our studies identify the IFN-{gamma}-KLF4-SLURP1 and CD200-CD200R1 axes as critical molecular drivers in tumor dormancy regulated by immune-tumor crosstalk. These insights provide enhanced mechanistic understanding of tumor dormancy in a mouse model suitable for further investigation of cancer treatment resistance and prevention of metastatic spread.

cancer biology↗

bioRxiv2024

Rebalancing Viral and Immune Damage versus Tissue Repair Prevents Death from Lethal Influenza Infection

Maintaining tissue function while eliminating infected cells is fundamental to host defense. Innate inflammatory damage contributes to lethal influenza and COVID-19, yet other than steroids, immunomodulatory drugs have modest effects. Among more than 50 immunomodulatory regimes tested in mouse lethal influenza infection, only the previously reported early depletion of neutrophils showed efficacy, suggesting that the infected host passes an early tipping point in which limiting innate immune damage alone cannot rescue physiological function. To re-balance the system late in infection, we investigated whether partial limitation of viral spread using oseltamivir (Tamiflu) together with enhancement of epithelial repair by blockade of interferon signaling or the limitation of further epithelial cell loss mediated by cytotoxic CD8+ T cells would prevent death. These treatments salvaged a large fraction of infected animals, providing new insight into the importance of repair processes and the timing of adaptive immune responses in survival of pulmonary infections.

immunology↗

bioRxiv2021

Metastatic Single Tumor Cells Evade NK Cell-mediated Killing by Thrombin-mediated Loss of the Activating Ligand CD155/PVR/Necl-5

Natural killer (NK) cells lyse invading tumor cells to limit metastatic growth in the lung, but how some cancers evade this host protective mechanism to establish a growing lesion is not known. Here we have combined ultra-sensitive bioluminescence whole body imaging with intravital two-photon microscopy involving genetically-encoded biosensors to examine this question. NK cells eliminated disseminated tumor cells from the lung within 24 hrs of arrival, but not thereafter. Intravital dynamic imaging revealed that a disseminated tumor cell in a pulmonary capillary interacts with an NK cell every 2 hrs on average. In the first 4 hrs after tumor cell arrival, 50% of such encounters lead to tumor cell death but after 24 hrs of arrival, nearly 100% of the interactions result in the survival of the tumor cell. This evasion of NK cell surveillance is mediated by thrombin-dependent loss of cell surface CD155/PVR/Necl-5, a ligand for the NK cell activating receptor DNAM-1. This loss prevents the NK cell signaling needed for effective killing of tumor targets. By quantitatively visualizing the evasion of NK cell surveillance, we have uncovered a molecular mechanism for cancer evasion and provided an explanation for the anti-metastatic effect of anticoagulants. SUMMARYIntravital functional two-photon microscopy reveals that metastatic tumor cells lodged in pulmonary capillaries acquire resistance to patrolling NK cells. Protease-mediated loss of the activating ligand CD155/PVR/Necl-5 on tumor cells prevents NK cells from ERK activation and tumor cell killing.

immunology↗

bioRxiv2020

S1PR1 regulates the quiescence of lymphatic vessels by inhibiting laminar shear stress-dependent VEGF-C signaling

During the growth of lymphatic vessels (lymphangiogenesis), lymphatic endothelial cells (LECs) at the growing front sprout by forming filopodia. Those tip cells are not exposed to circulating lymph, as they are not lumenized. In contrast, LECs that trail the growing front are exposed to shear stress, become quiescent and remodel into stable vessels. The mechanisms that coordinate the opposed activities of lymphatic sprouting and maturation remain poorly understood. Here we show that the canonical tip cell marker Delta-Like 4 (DLL4) promotes sprouting lymphangiogenesis by enhancing Vascular Endothelial Growth Factor C (VEGF-C) /VEGF Receptor 3 (VEGFR3) signaling. However, in lumenized lymphatic vessels laminar shear stress (LSS) inhibits the expression of DLL4, as well as additional tip cell markers. Paradoxically, LSS also upregulates VEGF-C/VEGFR3 signaling in LECs, but sphingosine 1-phosphate (S1P) receptor 1 (S1PR1) activity antagonizes LSS-mediated VEGF-C signaling to promote lymphatic vascular quiescence. Correspondingly, S1pr1 loss in LECs induced lymphatic vascular hypersprouting and hyperbranching, which could be rescued by reducing Vegfr3 gene dosage in vivo. In addition, S1PR1 regulates lymphatic vessel maturation by promoting membrane localization of the tight junction molecule Claudin-5. Our findings suggest a new paradigm in which LSS induces quiescence and promotes the survival of LECs by downregulating DLL4 and enhancing VEGF-C signaling, respectively. S1PR1 dampens LSS/VEGF-C signaling, thereby preventing sprouting from quiescent lymphatic vessels. These results also highlight the distinct roles that S1PR1 and DLL4 play in LECs when compared to their known roles in the blood vasculature.

developmental biology↗