title: Nanoimaging granule dynamics and subcellular structures in activated mast cells using soft X-ray tomography.
abstract: Mast cells play an important role in allergic responses. During activation, these cells undergo degranulation, a process by which various kinds of mediators stored in the granules are released. Granule homeostasis in mast cells has mainly been studied by electron microscopy (EM), where the fine structures of subcellular organelles are partially destroyed during sample preparation. Migration and fusion of granules have not been studied in detail in three dimensions (3D) in unmodified samples. Here, we utilized soft X-ray tomography (SXT) coupled with fluorescence microscopy to study the detailed structures of organelles during mast cell activation. We observed granule fission, granule fusion to plasma membranes, and small vesicles budding from granules. We also detected lipid droplets, which became larger and more numerous as mast cells were activated. We observed dramatic morphological changes of mitochondria in activated mast cells and 3D-reconstruction revealed the highly folded cristae inner membrane, features of functionally active mitochondria. We also observed giant vesicles containing granules, mitochondria, and lipid droplets, which we designated as granule-containing vesicles (GCVs) and verified their presence by EM in samples prepared by cryo-substitution, albeit with a less clear morphology. Thus, our studies using SXT provide significant insights into mast cell activation at the organelle level.
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan, ROC.
authors.forename: Huan-Yuan
authors.initials: HY
authors.lastname: Chen
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan, ROC.
authors.forename: Dapi Meng-Lin
authors.initials: DM
authors.lastname: Chiang
authors.affiliation: National Synchrotron Radiation Research Center, Taiwan, ROC.
authors.forename: Zi-Jing
authors.initials: ZJ
authors.lastname: Lin
authors.affiliation: National Synchrotron Radiation Research Center, Taiwan, ROC.
authors.forename: Chia-Chun
authors.initials: CC
authors.lastname: Hsieh
authors.affiliation: National Synchrotron Radiation Research Center, Taiwan, ROC.
authors.forename: Gung-Chian
authors.initials: GC
authors.lastname: Yin
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan, ROC.
authors.forename: I-Chun
authors.initials: IC
authors.lastname: Weng
authors.affiliation: Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin, Albert-Einstein-Str. 15, D-12489 Berlin, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Guttmann
authors.affiliation: Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin, Albert-Einstein-Str. 15, D-12489 Berlin, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Werner
authors.affiliation: Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin, Albert-Einstein-Str. 15, D-12489 Berlin, Germany.
authors.forename: Katja
authors.initials: K
authors.lastname: Henzler
authors.affiliation: Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin, Albert-Einstein-Str. 15, D-12489 Berlin, Germany.|Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, D-12489 Berlin, Germany.
authors.forename: Gerd
authors.initials: G
authors.lastname: Schneider
authors.affiliation: National Synchrotron Radiation Research Center, Taiwan, ROC.
authors.forename: Lee-Jene
authors.initials: LJ
authors.lastname: Lai
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan, ROC.|Department of Dermatology, UC Davis School of Medicine, Sacramento, CA, USA.
authors.forename: Fu-Tong
authors.initials: FT
authors.lastname: Liu
mesh_terms: D000707:Anaphylaxis / Q000276:immunology*; D000818:Animals; D015550:Cell Degranulation; D002460:Cell Line; D003594:Cytoplasmic Granules / Q000648:ultrastructure*; D042541:Intracellular Space; D008407:Mast Cells / Q000648:ultrastructure*; D008854:Microscopy, Electron; D008928:Mitochondria / Q000648:ultrastructure*; D036103:Nanotechnology; D051381:Rats; D014056:Tomography, X-Ray / Q000379:methods*