Biology subjects

Nojima, S.

Publications and source records attributed to Nojima, S..

3 recordsLinked to original sources

bioRxiv2024

Spatial transcriptomics elucidates medulla niche supporting germinal center response in myasthenia gravis thymoma

Myasthenia gravis (MG) is known to be epidemiologically associated with abnormalities of the thymus, an organ that maintains central tolerance. However, due to the complexity of the thymus, specific characteristics related to the pathogenesis of MG remain elusive. In our study, we attempted to narrow down the features associated with MG using spatial transcriptome analysis of thymoma and thymic hyperplasia samples. We found that the majority of thymomas were constituted by the cortical region, whereas the medullary region was localized in comparatively restricted areas. Moreover, the medullary region contained polygenic enrichment, MG-specific germinal center structures, and a supporting immune microenvironment. Additionally, neuromuscular medullary thymic epithelial cells (nmTECs), previously identified as MG-specific autoantigen-producing cells, were situated at the cortico-medullary junction. The immune microenvironment in the medulla was characterized by a specific chemokine pattern and specific immune cells, such as CCR7+ migratory dendritic cells (migDCs) and effector regulatory T (Treg) cells. Furthermore, similar germinal center structures and immune microenvironments were observed in the medulla during thymic hyperplasia. This study indicates that the medulla and junction areas are related to the pathology of MG, suggesting that these areas should be the focus of future studies on MG pathogenesis and drug targeting.

immunology↗

bioRxiv2022

Dynamic interaction of bacterial cellulose synthase subunit D (BcsD) in type I bacterial cellulose synthase

Cellulose is a promising biological material for supporting sustainable human life. This natural polymer is synthesized by cellulose synthase, a protein complex in the cell membrane. Cellulose synthase in bacteria is a hetero-subunit complex, and its subunit organization varies widely depending on the species. In the type I bacterial cellulose synthase complex, the BcsD (bacterial cellulose synthase D) protein is believed to play an important role in producing cellulose with long slender fiber morphology and high crystallinity, given the phenotype of the bcsD-deficient mutant and the specific existence of the type I operon in bacterial species synthesizing crystalline cellulose microfibrils such as Acetobacter. In this study, we successfully established a heterogeneously expressed Bcs protein in Escherichia coli as an experimental model and conducted biochemical studies for the BcsD protein and the other three major subunits of bacterial cellulose synthase, BcsA, BcsB, and BcsC. It has been shown that the BcsD protein interacts with the functionally required minimal subunits of the BcsAB complex, as well as the BcsC protein. Furthermore, it was shown that BcsD interacts with the BcsAB complex in two modes: direct protein-protein interactions and indirect interactions through the product cellulose. The former and latter modes represent the basal and active states of the type I bacterial cellulose synthase, respectively. This dynamic behavior of the BcsD protein is important for the type I bacterial cellulose synthase complex to regulate the crystallization process of cellulose.

biochemistry↗

bioRxiv2021

Myasthenia gravis-specific aberrant neuromuscular gene expression by medullary thymic epithelial cells in thymoma

Myasthenia gravis (MG) is a neurological disease caused by autoantibodies against neuromuscular-associated proteins. While MG is frequently developed in thymoma patients, the etiologic factors for MG are not well understood. Here, by constructing a comprehensive atlas of thymoma using bulk and single-cell RNA-seq, we identified ectopic expression of neuromuscular molecules in MG-associated thymoma (MG-thymoma). These molecules were originated from a distinct subpopulation of medullary thymic epithelial cells (mTECs), which we named neuromuscular mTECs (nmTECs). MG-thymoma also exhibited microenvironments dedicated to autoantibody production, including ectopic germinal center formation, T follicular helper cell accumulation, and type 2 conventional dendritic cell migration. Cell-cell interaction analysis also predicted the interaction between nmTECs and T/B cells via CXCL12-CXCR4. The enrichment of nmTECs presenting neuromuscular molecules within MG-thymoma was further confirmed by immunohistochemically and by cellular composition estimation from MG-thymoma transcriptome. Altogether, this study suggests that nmTECs play a significant role in MG pathogenesis via ectopic expression of neuromuscular molecules.

immunology↗