A novel method to identify Post-Aire stages of medullary thymic epithelial cell differentiation

摘要

Autoimmune regulator~+ (Aire) medullary thymic epithelial cells (mTECs) play a critical role in tolerance induction. Several studies demonstrated that Aire~+mTECs differentiate further into Post-Aire cells. Yet, the identification of terminal stages of mTEC maturation depends on unique fate-mapping mouse models. Herein, we resolve this limitation by segmenting the mTEC~hi(MHCII~hiCD80~hi) compartment into mTEC~A/hi (CD24~-Sca1~-), mTEC~B/hi (CD24~+Sca1~-), and mTEC~c/hi (CD24~+Sca1~+). While mTEC~A/hi included mostly Aire-expressing cells, mTEC~B/hi contained Aire~+ and Aire~- cells and mTEC~c/hi were mainly composed of cells lacking Aire. The differential expression pattern of Aire led us to investigate the precursor-product relationship between these subsets. Strikingly, tran-scriptomic analysis of mTEC~A/hi, mTEC~B/hi, and mTEC~c/hi sequentially mirrored the specific genetic program of Early-, Late- and Post-Aire mTECs. Corroborating their Post-Aire nature, mTEC~c/hi downregulated the expression of tissue-restricted antigens, acquired traits of differentiated keratinocytes, and were absent in Aire-deficient mice. Collectively, our findings reveal a new and simple blueprint to survey late stages of mTEC differentiation.