Epigenetic regulation of cell-autonomous type I interferon responses in trophoblast

胎盘是支持胎儿发育的重要多功能器官。胎盘功能障碍对母亲和胎儿都有重大影响，并与所谓的巨大产科综合征有关，包括先兆子痫、宫内发育受限和早产。这些反过来又构成围产期胎儿死亡和发病率的危险因素，以及成年后的长期疾病。然而，胎盘功能障碍的分子基础尚不清楚，需要将基本机制发现与表型和临床数据联系起来的研究策略。在本提案中，我们将重点关注胎盘炎症的调节，以及它如何影响妊娠结局。具体地说，我们将研究I型干扰素(干扰素)反应的调节，这构成了对抗病毒和细菌等病原体的先天免疫途径。值得注意的是，I型干扰素反应涉及怀孕的正常过程，如分娩，这可能发生在不孕不育的条件下。同样，I型IFN的调节失调与早产有关，但这似乎也可能在没有感染的情况下发生。这表明胎盘中存在细胞内在的炎症触发因素。事实上，我们发现当细胞耗尽KAP1蛋白时，滋养层细胞(胎盘细胞)可以自主地表现出I型干扰素反应。KAP1是表观遗传机制的重要辅助蛋白，它不仅调节基因的表达，而且最重要的是调节转座元件(TES)的表达。TES是在基因组中整合和复制的重复序列，已经扩展到约占人类基因组的一半。TES在胎盘的进化过程中发挥了重要作用。与这一提议相关的TE生物学的一个关键方面是，许多病毒来自古老的逆转录病毒，可以模仿它们的许多行为，包括在细胞内触发炎症反应。因此，我们假设TES的表观遗传去调控可以驱动胎盘中感染非依赖性的I型干扰素反应，对妊娠结局有潜在的影响。这得到了培养细胞和人类胎盘的初步数据的支持。我们建议通过研究培养细胞的分子机制，测试动物模型的表型，最后分析适当的人类队列中的胎盘样本来检验这一假设。在细胞培养模型中，我们将深化我们在KAP1上的发现，并将其扩展到其他TE调节途径。我们还将直接测试TES在驱动I型干扰素反应中的作用。在小鼠身上，我们将测试KAP1和TE解除调控对炎症标记物、胎盘发育和妊娠时机的影响。在人类中，我们将询问足月和早产胎盘的I型干扰素无菌反应是否与TE放松调控有关。通过这一全面的工作计划，我们的目标是揭示胎盘炎症的新机制和临床见解，以及它与正常和病理性妊娠事件的联系。

The placenta is an essential multi-functional organ that supports fetal development. Placental dysfunction has a major impact on both mother and fetus, and is associated with what are known as the great obstetrics syndromes, which include preeclampsia, intrauterine growth restriction and preterm birth. These in turn constitute risk factors for perinatal fetal mortality and morbidity, as well as long-term illness in adulthood. Yet the molecular underpinnings of placental dysfunction remain unclear, requiring research strategies that link basic mechanistic findings with phenotypes and clinical data.In this proposal we will focus on the regulation of inflammation in the placenta, and how it impacts pregnancy outcomes. Specifically, we will study the regulation of the type I interferon (IFN) response, which constitutes an innate immunity pathway against pathogens such as viruses and bacteria. Notably, type I IFN responses are involved in normal processes in pregnancy such as labour, which presumably occur in sterile conditions. Similarly, dysregulation of type I IFNs is linked to preterm birth, yet this can also seemingly occur in the absence of infection. This suggests that there are cell-intrinsic triggers of inflammation in the placenta.Indeed, we have found that trophoblast (cells of the placenta) can autonomously display a type I IFN response when cells are depleted of the KAP1 protein. KAP1 is an important accessory protein for epigenetic mechanisms that regulates not only the expression of genes, but also, and arguably most prominently, that of transposable elements (TEs). TEs are repetitive sequences that integrated and replicated within genomes, having expanded to make up approximately half of the human genome. TEs have played important roles in the evolution of the placenta. A key aspect of TE biology relevant to this proposal is that many are derived from ancient retroviruses and can mimic many of their actions, including triggering inflammatory responses within the cell. We therefore hypothesize that epigenetic deregulation of TEs can drive infection-independent type I IFN responses in the placenta, with potential impact for pregnancy outcomes. This is supported by preliminary data in cultured cells and human placentas.We propose to test this hypothesis by investigating molecular mechanisms in cultured cells, testing phenotypes in animal models, and finally analysing placental samples from appropriate human cohorts. In cell culture models we will deepen our findings on KAP1 and expand it to other TE-regulatory pathways. We will also directly test for a role of TEs in driving type I IFN responses. In mice, we will test the effect of KAP1 and TE deregulation on markers of inflammation, placental development and gestational timing. In humans, we will ask whether sterile type I IFN responses are associated with TE deregulation, both in term and preterm placentas. Through this comprehensive work programme we aim to uncover novel mechanistic and clinical insights into placental inflammation, and its links to normal and pathological pregnancy events.