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Space flight-associated neuroocular syndrome (SANS), characterized by increased optic nerve sheath diameter (ONSD) and globe flattening, is detected in some astronauts. 1 Because inflight cerebrospinal fluid (CSF) pressure measurement is excessively invasive, it is not realistic to conduct. We estimated CSF pressure (p CSF) during space flight based on published reports 2 and found that SANS was not caused mainly by increased p CSF but rather by brain upward shift (BUS), recently demonstrated in postflight astronauts. 3 Our findings suggest that eyes are portals into effects on the brain during space flight.

Myasthenia gravis (MG) is a neurological disease caused by autoantibodies against neuromuscular-associated proteins. While MG frequently develops 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-sequencing, we identify ectopic expression of neuromuscular molecules in MG-type thymoma. These molecules are found within a distinct subpopulation of medullary thymic epithelial cells (mTECs), which we name neuromuscular mTECs (nmTECs). MG-thymoma also exhibits 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 predicts the interaction between nmTECs and T/B cells via CXCL12-CXCR4. The enrichment of nmTECs presenting neuromuscular molecules within MG-thymoma is further confirmed immunohistochemically and by cellular composition estimation from the MG-thymoma transcriptome. Altogether, this study suggests that nmTECs have a significant function in MG pathogenesis via ectopic expression of neuromuscular molecules.

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