Table_3_Klf4 protects thymus integrity during late pregnancy.xlsx

Pregnancy causes abrupt thymic atrophy. This atrophy is characterized by a severe decrease in the number of all thymocyte subsets and qualitative (but not quantitative) changes in thymic epithelial cells (TECs). Pregnancy-related thymic involution is triggered by progesterone-induced functional changes affecting mainly cortical TECs (cTECs). Remarkably, this severe involution is rapidly corrected following parturition. We postulated that understanding the mechanisms of pregnancy-related thymic changes could provide novel insights into signaling pathways regulating TEC function. When we analyzed genes whose expression in TECs was modified during late pregnancy, we found a strong enrichment in genes bearing KLF4 transcription factor binding motifs. We, therefore, engineered a Psmb11-iCre : Klf4lox/lox mouse model to study the impact of TEC-specific Klf4 deletion in steady-state conditions and during late pregnancy. Under steady-state conditions, Klf4 deletion had a minimal effect on TEC subsets and did not affect thymic architecture. However, pregnancy-induced thymic involution was much more pronounced in pregnant females lacking Klf4 expression in TECs. These mice displayed a substantial ablation of TECs with a more pronounced loss of thymocytes. Transcriptomic and phenotypic analyses of Klf4-/- TECs revealed that Klf4 maintains cTEC numbers by supporting cell survival and preventing epithelial-to-mesenchymal plasticity during late pregnancy. We conclude that Klf4 is essential for preserving TEC’s integrity and mitigating thymic involution during late pregnancy.

妊娠可引发突发性胸腺萎缩。该萎缩以所有胸腺细胞亚群数量显著减少，以及胸腺上皮细胞（thymic epithelial cells, TECs）出现质性（而非量性）变化为特征。妊娠相关的胸腺退化主要由孕酮诱导的功能改变触发，此类改变主要影响皮质胸腺上皮细胞（cortical thymic epithelial cells, cTECs）。值得注意的是，这种严重的退化可在分娩后迅速得到纠正。
我们提出假说，阐明妊娠相关胸腺变化的机制，可为调控TEC功能的信号通路提供全新见解。当我们分析妊娠晚期TEC中表达发生改变的基因时，发现其中显著富集了携带KLF4转录因子结合基序的基因。为此，我们构建了Psmb11-iCre : Klf4lox/lox小鼠模型，以探究稳态条件下及妊娠晚期TEC特异性Klf4敲除的影响。
在稳态条件下，Klf4敲除对TEC亚群的影响微乎其微，且不会改变胸腺结构。但在TEC中缺失Klf4表达的妊娠雌性小鼠中，妊娠诱导的胸腺退化程度明显加剧。此类小鼠表现出TEC的显著缺失，并伴随胸腺细胞更为严重的丢失。对Klf4敲除TEC的转录组学与表型分析显示，在妊娠晚期，Klf4通过维持细胞存活、抑制上皮-间充质可塑性，以维持皮质TEC的数量。
综上，我们认为Klf4对于维持TEC的完整性、减轻妊娠晚期的胸腺退化至关重要。