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，并与所谓的重大产科综合征有关，包括先兆子痫、宫内生长受限和早产。这些又构成围产期胎儿死亡率和发病率以及成年后长期患病的危险因素。然而，胎盘功能障碍的分子基础仍然不清楚，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。具体来说，我们将研究I型干扰素（IFN）反应的调节，这构成了对病毒和细菌等病原体的先天免疫途径。值得注意的是，I型IFN应答参与妊娠中的正常过程，例如分娩，这可能发生在无菌条件下。类似地，I型IFN的失调与早产有关，但这似乎也可能在没有感染的情况下发生。事实上，我们已经发现，当滋养层细胞（胎盘细胞）的KAP 1蛋白耗尽时，滋养层细胞可以自主地显示I型IFN反应。KAP 1是表观遗传机制的重要辅助蛋白，不仅调节基因的表达，而且可以说最突出的是调节转座因子（TE）的表达。TE是在基因组内整合和复制的重复序列，已扩展到约占人类基因组的一半。TE在胎盘的进化中起着重要作用。与这一提议相关的TE生物学的一个关键方面是，许多来自古老的逆转录病毒，可以模仿它们的许多作用，包括触发细胞内的炎症反应。因此，我们假设，表观遗传失调的TE可以驱动感染无关的I型干扰素在胎盘中的反应，对妊娠结局的潜在影响。这是支持培养细胞和人类胎盘的初步数据。我们建议通过研究培养细胞的分子机制，在动物模型中测试表型，并最终分析合适的人类队列的胎盘样本来验证这一假设。在细胞培养模型中，我们将深化我们对KAP 1的发现，并将其扩展到其他TE调控途径。我们还将直接测试TE在驱动I型IFN应答中的作用。在小鼠中，我们将测试KAP 1和TE失调对炎症标志物、胎盘发育和妊娠时间的影响。在人类中，我们将询问在足月和早产胎盘中，无菌I型IFN应答是否与TE失调相关。通过这项全面的工作计划，我们的目标是揭示胎盘炎症的新机制和临床见解，及其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.