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

Abstract

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 mTEChi(MHCIIhiCD80hi) compartment into mTECA/hi (CD24−Sca1−), mTECB/hi (CD24+Sca1−), and mTECC/hi (CD24+Sca1+). While mTECA/hi included mostly Aire‐expressing cells, mTECB/hi contained Aire+ and Aire− cells and mTECC/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, transcriptomic analysis of mTECA/hi, mTECB/hi, and mTECC/hi sequentially mirrored the specific genetic program of Early‐, Late‐ and Post‐Aire mTECs. Corroborating their Post‐Aire nature, mTECC/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.

Acute irradiation alters the heterogeneity among medullary thymic epithelial cells

“…TA-mTECs are concordant with clusters 6 and 9, which are separated most likely because of differences in cell cycle phase proportions (Supplementary Figure S2C, D and E). Cluster 2 seemed to contain both Aire + and Aire -TECs (Figure 3B and C) and its average expression level of Aire was lower than that of cluster 1; therefore, it was assigned to Late-Aire mTECs (Ferreirinha et al, 2021).…”

T‐cell selection in the thymus: New routes toward the identification of the self‐peptide ligandome presented by thymic epithelial cells

“…Moreover, the identification of many of the new progenitors or mature subsets depends so far on complex scR-NAseq approaches, which are incompatible with their isolation for functional analysis. Therefore, there is a need to develop easier methodologies to prospectively identify these populations based on the expression of specific cell-surface markers [16,17,21,22]. Lastly, complementary genome-wide studies have provided valuable insights into the cellular heterogeneity and transcriptomic diversity of human TECs [23][24][25], which appear to mimic in part the data obtained in the mouse models.…”

“…It is recognized that mTECs have distinctive (epi)genetic abilities to express TRA, in a process that is partially dependent on Aire and forebrain embryonic zinc finger 2 (Fezf2) [1,2]. Apart from direct control of TRA expression, Aire regulates alternative processes in mTEC function that cooperates to ensure tolerance induction and prevent autoimmunity [22,28,29]. The promiscuous gene expression capacity of mTECs allows them to function as a library of ubiquitous antigens and TRAs, which at a single cell level are presented in an ordered but randomly organized expression pattern [30][31][32].…”

miR-155 exerts posttranscriptional control of autoimmune regulator (Aire) and tissue-restricted antigen genes in medullary thymic epithelial cells

“…In addition to TRAs, which are extremely important for testing the self-reactivity of thymocytes, studies have shown that several Aire-dependent genes have different functions in mTECs; these genes participate in processes such as the differentiation and maturation of mTECs [ 14 ], interactions of mTECs with thymocytes and dendritic cells [ 15 , 16 ], induction of thymocyte migration within the thymus, apoptosis of mTECs and even the processing of mRNAs (alternative splicing), thus contributing to the expression of TRA isoforms in mTECs [ 1 – 3 , 5 , 6 , 17 ].…”