TFEB safeguards trophoblast syncytialization in humans and mice (mouse RNA-Seq)

Nutrient sensing and adaptation in the placenta are essential for pregnancy viability and proper fetal growth. Our recent research demonstrates that the placenta adapts to nutrient insufficiency through mTOR inhibition-mediated trophoblast differentiation toward syncytiotrophoblasts (STBs), a highly specialized multinucleated trophoblast subtype directing extensive maternal-fetal interactions. However, the underlying mechanism remains elusive. Here, we unravel the indispensable role of the mTORC1 downstream transcriptional factor TFEB in STB formation both in vitro and in vivo. Endogenous TFEB deficiency significantly impaired STB differentiation in trophoblast cells and placenta organoids. Mechanistically, TFEB conferred direct transcriptional regulation of the fusogen ERVFRD-1 in human trophoblasts and thereby profoundly promoted STB formation, independent of its canonical function as a master regulator of the autophagy-lysosomal pathway. In line with the in vitro findings, systemic or trophoblast-specific deletion of Tfeb compromised STB formation and placental vascular construction, leading to severe embryonic lethality. Moreover, TFEB directs the trophoblast syncytialization response driven by mTORC1 signaling. Importantly, TFEB expression positively correlates with the reinforced trophoblast syncytialization in human fetal growth restriction (FGR) placentas exhibiting suppressed mTORC1 activity. Our findings substantiate that the TFEB-fusogen axis ensures proper STB formation during placenta development and under nutrient stress, shedding light on TFEB as a mechanistic link between nutrient-sensing machinery and trophoblast differentiation. To investigate the function of TFEB in the regulation of trophoblast syncytialization in human and mice, we established Tfeb ko mice. We then performed gene expression profiling analysis using data obtained from RNA-seq of control or Tfeb KO mice from placenta in E9.5 and E11.5.胎盘的营养感知与适应对于妊娠存活及胎儿正常生长至关重要。我们的最新研究表明，胎盘可通过mTOR（哺乳动物雷帕霉素靶蛋白，mammalian target of rapamycin）抑制介导的滋养层细胞向合胞体滋养层细胞（syncytiotrophoblasts, STBs）分化来适应营养不足——合胞体滋养层细胞是一类高度特化的多核滋养层亚型，负责介导广泛的母胎交互。然而，其背后的分子机制仍不明晰。本研究阐明了mTORC1（mTOR复合物1，mTOR complex 1）下游转录因子TFEB（转录因子EB，Transcription Factor EB）在体外与体内合胞体滋养层细胞形成过程中不可或缺的作用。内源性TFEB缺失会显著损伤滋养层细胞与胎盘类器官的合胞体滋养层细胞分化。从机制上来说，TFEB可直接转录调控人滋养层细胞中的融合因子ERVFRD-1，进而独立于其作为自噬-溶酶体通路核心调控因子的经典功能，强力促进合胞体滋养层细胞的形成。与体外实验结果一致，全身或滋养层特异性敲除Tfeb会破坏合胞体滋养层细胞形成与胎盘血管构建，导致严重的胚胎致死。此外，TFEB介导了由mTORC1信号通路驱动的滋养层合胞化反应。重要的是，在呈现mTORC1活性受抑的人类胎儿生长受限（fetal growth restriction, FGR）胎盘中，TFEB的表达与增强的滋养层合胞化呈正相关。我们的研究结果证实，TFEB-融合因子轴可确保胎盘发育过程中及营养应激状态下合胞体滋养层细胞的正常形成，揭示了TFEB作为营养感知机制与滋养层分化之间的机制性纽带。为探究TFEB在人类与小鼠滋养层合胞化调控中的功能，我们构建了Tfeb基因敲除（knockout, KO）小鼠。随后，我们利用胚胎发育第9.5天（E9.5）与第11.5天（E11.5）的对照组或Tfeb KO小鼠胎盘的RNA-seq数据开展了基因表达谱分析。