To induce central T-cell tolerance, medullary thymic epithelial cells (mTEC) collectively express most protein-coding genes, thereby presenting an extensive library of tissue-restricted antigens (TRAs). To resolve mTEC diversity and whether promiscuous gene expression (PGE) is stochastic or coordinated, we sequenced transcriptomes of 6,894 single mTEC, enriching for 1,795 rare cells expressing either of two TRAs, TSPAN8 or GP2. Transcriptional heterogeneity allowed partitioning of mTEC into 15 reproducible subpopulations representing distinct maturational trajectories, stages and subtypes, including novel mTEC subsets, such as chemokine-expressing and ciliated TEC, which warrant further characterisation. Unexpectedly, 50 modules of genes were robustly defined each showing patterns of co-expression within individual cells, which were mainly not explicable by chromosomal location, biological pathway or tissue specificity. Further, TSPAN8+ and GP2+ mTEC were randomly dispersed within thymic medullary islands. Consequently, these data support observations that PGE exhibits ordered co-expression, although mechanisms underlying this instruction remain biologically indeterminate. Ordered co-expression and random spatial distribution of a diverse range of TRAs likely enhance their presentation and encounter with passing thymocytes, while maintaining mTEC identity.

中文翻译：

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单个髓质胸腺上皮细胞中生物学上不确定但有序的混杂基因表达。

为了诱导中枢 T 细胞耐受，髓质胸腺上皮细胞 (mTEC) 共同表达大多数蛋白质编码基因，从而提供广泛的组织限制性抗原 (TRAs) 文库。为了解决 mTEC 的多样性以及混杂基因表达 (PGE) 是随机的还是协调的，我们对 6,894 个单个 mTEC 的转录组进行了测序，富集了 1,795 个表达两种 TRA、TSPAN8 或 GP2 的稀有细胞。转录异质性允许将 mTEC 划分为 15 个可重复的亚群，代表不同的成熟轨迹、阶段和亚型，包括新的 mTEC 亚群，例如表达趋化因子和纤毛 TEC，这需要进一步表征。出乎意料的是，50 个基因模块被稳健地定义，每个模块都显示出单个细胞内的共表达模式，主要无法通过染色体位置、生物学途径或组织特异性来解释。此外，TSPAN8+ 和 GP2+ mTEC 随机分散在胸腺髓质岛内。因此，这些数据支持 PGE 表现出有序共表达的观察结果，尽管该指令背后的机制在生物学上仍然不确定。各种 TRA 的有序共表达和随机空间分布可能会增强它们的呈现和与经过的胸腺细胞的相遇，同时保持 mTEC 身份。尽管该指令背后的机制在生物学上仍然不确定。各种 TRA 的有序共表达和随机空间分布可能会增强它们的呈现和与经过的胸腺细胞的相遇，同时保持 mTEC 身份。尽管该指令背后的机制在生物学上仍然不确定。各种 TRA 的有序共表达和随机空间分布可能会增强它们的呈现和与经过的胸腺细胞的相遇，同时保持 mTEC 身份。