Next-generation sequencing of cTEC and mTEC isolated from non-pregnant and pregnant females lacking the expression of Klf4 (KO) or not (LOX)

Stress-induced thymic involution is defined by profound damage to thymic epithelial cells (TECs), resulting in an acute and transient reduction of thymopoietic capacity. During pregnancy, thymic involution is not associated with TEC loss but rather with TEC quality modifications. Study of the mechanisms of TEC maintenance during pregnancy may be of critical importance for identifying new players for thymic regeneration in other models of thymic involution. We report a strong enrichment for motifs recognized by KLF4 based on genes differentially expressed in TECs of pregnant females. Therefore, we studied the impact of Klf4 deletion in TECs during pregnancy by analyzing thymus composition and TEC transcriptome. Conditional Klf4 deletion in homeostatic conditions does not injure thymic integrity. However, pregnant females lacking Klf4 show a disrupted thymus with substantial loss of thymic epithelial cells. Klf4 maintains cTEC number during pregnancy by maintaining cell survival and inhibiting the transition to a mesenchymal state. Our study reveals Klf4 as a protective factor for TECs during pregnancy-associated thymic involution and represents a potential study subject for other models of stress-induced thymic involution. mRNA sequencing was performed on cortical and medullary thymic epithelial cells (cTECs and mTECs) extracted from 12 weeks aged non-pregnant and pregnant female mice (2 days before delivery), which are either expressing Klf4 (LOX) or not (KO). The conditional deletion of Klf4 in TECs was performed using a Cre/lox system. cTECs (EpCAM+, CD45-, UEA1-) and mTECs (EpCAM+, CD45-, UEA1+) were purified by cell sorting after the enzymatic digestion of the stroma.