The Discovery of Nucleocytosis at the University of Tokyo
Researchers at the Institute of Medical Science (IMSUT), University of Tokyo, have identified a groundbreaking process called nucleocytosis, where macrophages actively extract DNA from the nuclei of dying cells. This mechanism activates the cGAS-STING pathway, leading to type I interferon (IFN-I) production, which plays a dual role in protective immunity and potential disease pathology.
The study, published in Nature Communications on February 18, 2026, reveals how self-DNA from compromised cells triggers innate immune responses. Led by Hideo Negishi, with co-first authors Yusuke Wada and Yoshitaka Shirasaki, the team demonstrated that lysosomal dysfunction in target cells enables macrophages to access and pull out nuclear DNA.
This finding builds on decades of research into cytosolic DNA sensing, offering fresh insights into how the body distinguishes harmful cell death from routine turnover. For Japan's academic community, it underscores IMSUT's prowess in immunology, attracting global talent to higher education institutions like the University of Tokyo.
Background on cGAS-STING Pathway and Self-DNA Sensing
The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway is central to innate immunity. When cytosolic DNA is detected, cGAS produces second messenger cGAMP, activating STING on the endoplasmic reticulum, which triggers IFN-I production via TBK1-IRF3 signaling. IFN-I then amplifies antiviral states and adaptive immunity.
Self-DNA, normally sequestered in the nucleus or mitochondria, can aberrantly enter the cytosol during infection, cancer, or sterile injury, risking autoimmune activation. Prior studies showed phagocytosis of dying cells exposes DNA, but the precise extraction from intact nuclei was unknown until nucleocytosis.
In Japan, pioneers like Shizuo Akira, who won the 2011 Nobel for Toll-like receptor discovery, paved the way. IMSUT continues this legacy, with facilities supporting advanced live-cell imaging crucial for visualizing nucleocytosis.
Key Researchers and Their Contributions
Hideo Negishi, project associate professor at IMSUT, spearheaded the study, integrating expertise in nucleic acid immunity. His prior work on immunogenic cell death informed the nucleocytosis hypothesis. Yusuke Wada and Yoshitaka Shirasaki, both from IMSUT, conducted pivotal experiments on lysosomal dynamics and DNA extraction.
Ken J. Ishii, professor and vaccine expert, provided oversight on translational potential. The 20+ author team included specialists in autophagy, like Atsushi Yoshimori, ensuring multidisciplinary rigor. This collaborative model exemplifies University of Tokyo's research ecosystem, fostering PhD and postdoc opportunities via higher-ed-jobs/postdoc.
Deciphering the Nucleocytosis Mechanism Step-by-Step
Nucleocytosis unfolds through precise cellular events:
- Lysosomal malfunction in target cells, induced by proton loss or palmitoyl-protein thioesterase 1 (PPT1) inhibition, causes cell death.
- Calreticulin (CRT), an endoplasmic reticulum chaperone, accumulates in the nucleus due to nuclear envelope perturbations.
- Macrophages engulf or contact dying cells, using secretion activity to breach nuclear barriers enriched with CRT.
- Nuclear DNA is mechanically extracted into the macrophage cytosol.
- Extracted DNA binds cGAS, igniting STING-IFN-I signaling.
Live-cell imaging confirmed extraction dynamics, distinguishing it from passive leakage. PPT1, a lysosomal enzyme degrading palmitoylated proteins, links lipid metabolism to immunity when inhibited.
Photo by Szymon Shields on Unsplash
Experimental Approaches Validating Nucleocytosis
The team employed CRISPR-Cas9 knockouts of cGAS/STING/PPT1 in mouse models, observing abolished IFN-I responses. Cationic amphiphilic drugs (CADs) like amiodarone, PPT1 inhibitors, mimicked the process in vitro and in vivo, inducing nucleocytosis-dependent inflammation.
Advanced techniques included super-resolution microscopy for nuclear DNA tracking and mass cytometry for IFN-I profiling. Co-culture assays with lysosome-impaired fibroblasts showed macrophages selectively extracting DNA from CRT+ nuclei. These methods highlight IMSUT's cutting-edge infrastructure, ideal for aspiring researchers exploring academic careers.
Read the full Nature Communications paper for protocols and data.
Implications for Autoimmune and Inflammatory Diseases
Nucleocytosis explains self-DNA-driven pathologies like systemic lupus erythematosus (SLE), where defective clearance amplifies IFN-I. In Aicardi-Goutières syndrome, mimicking viral DNA accumulation, it could exacerbate neurodegeneration.
Conversely, in cancer, enhancing nucleocytosis might boost immunogenic cell death for immunotherapy. CADs, FDA-approved for other uses, offer repurposing potential, but risks of hyperinflammation necessitate balanced modulation. Japanese cohorts, with high autoimmune incidence, provide ideal testing grounds.
PubMed abstract details disease models.
Therapeutic Potential and Drug Targets
PPT1 emerges as a prime target; inhibitors trigger controlled nucleocytosis for vaccines, while stabilizers prevent excess in autoimmunity. Ongoing trials could integrate CADs with checkpoint inhibitors.
Gene therapies editing macrophage PPT1 might fine-tune responses. For higher ed, this opens research jobs in translational immunology at universities like Tokyo.
Japan's Preeminence in Immunology Research
Japan leads with 10% global immunology papers, bolstered by MEXT funding and RIKEN. University of Tokyo ranks top-5 worldwide for life sciences, drawing international postdocs.
Nucleocytosis aligns with national priorities in precision medicine. Programs like JSPS fellowships support such breakthroughs, encouraging careers via research assistant roles.
Future Outlook and Research Frontiers
Upcoming studies will probe nucleocytosis in humans, using organoids and single-cell RNA-seq. Human macrophage variants and cross-species differences warrant exploration.
Integration with AI for pathway prediction could accelerate discoveries. For students, rate professors in immunology on Rate My Professor to find mentors.
Opportunities in Higher Education and Immunology Careers
This discovery spotlights Japan's universities for immunology training. Pursue PhDs at UTokyo or fellowships abroad. Explore higher-ed-jobs, career advice, and university jobs for roles in research and academia. Post a vacancy or find adjunct positions to contribute to the field.
