Understanding the role of histone3 lysine4 trimethylation in neontal innate immune development under normal and inflammatory conditions

项目摘要/摘要 新生儿的促炎细胞因子的表达受到抑制，难以清除病原体，使 他们特别容易受到感染。这是一个世界性的健康问题，新生儿感染。 每年造成近100万人死亡。新生儿特异性免疫的控制因素 人们对这些反应以及它们如何以及何时过渡到更成熟的反应知之甚少。新生儿依赖于 由于适应性免疫系统的主要缺陷，他们严重依赖先天免疫反应来对抗感染。 单核细胞和巨噬细胞是先天免疫反应的中心细胞，通过感知病原体和启动 导引他们清除的炎症性瀑布。尽管新生儿和成人的单核/巨噬细胞 含有相同的遗传密码，它们在病原体诱导的基因表达上表现出显著的差异。邮寄- 翻译性组蛋白修饰通过影响染色质结构和基因转录调节基因转录。 可访问性，并可能在这方面发挥作用。单核/巨噬细胞显示出一个发育阶段- H3K4甲基转移酶MLL1的特异性增加及其激活组蛋白的相关收益 组蛋白3赖氨酸4三甲基化(H3K4me3)在免疫重要基因启动子位置的修饰 随着发育从极早产儿发展到成人。这一收益允许变得越来越强大 随着发育的进展，炎症反应。皮肤和胃肠道的微生物定植 发生在出生后，与1型干扰素的表达有关，据信1型干扰素有助于免疫 系统成熟，防止有害的病原体反应。绒毛膜羊膜炎是一个炎症过程 在出生时左右影响新生儿，这对免疫系统发育和 容易使暴露在空气中的新生儿患上长期的免疫相关并发症。这一点的中心假设是 推测由于缺乏H3K4me3，新生儿单核/巨噬细胞在很大程度上没有H3K4me3模式 宫内微生物暴露，以及出生后微生物暴露刺激低度1型干扰素 诱导巨噬细胞H3K4me3沉积并促进MLL1表达 发展阶段特定的方式。绒毛膜羊膜炎暴露刺激发育 不适当的1型干扰素表达，导致MLL1表达失调和 新生儿单核/巨噬细胞格局的整体重塑及其随后的功能障碍 单核/巨噬细胞反应。这一假设将通过以下具体目标进行调查：1) 描述婴儿期和儿童期正常人单核细胞H3K4me3的模式，并确定 发育阶段特异性H3K4me3单核细胞模式如何影响染色质可及性和基因 表达，2)确定MLL1驱动的H3K4me3中1型干扰素的需求和充分性 在小鼠巨噬细胞发育和功能中的位置，以及3)决定1型干扰素的作用 和MLL1在绒毛膜羊膜炎诱导的小鼠巨噬细胞H3K4me3重构和后续功能中的作用。

PROJECT SUMMARY/ABSTRACT Neonates have dampened expression of pro-inflammatory cytokines and difficulty clearing pathogens, making them uniquely susceptible to infections. This is a worldwide health problem, with neonatal infections contributing to nearly one million deaths each year. The factors controlling neonatal specific immune responses and how and when they transition to more mature responses are poorly understood. Neonates rely heavily on innate immune responses to fight infections due to major defects in their adaptive immune system. Monocytes and macrophages are central to innate immune responses by sensing pathogens and initiating an inflammatory cascade that directs their clearance. Although both neonatal and adult monocytes/macrophages contain the same genetic code, they exhibit dramatic differences in pathogen-induced gene expression. Post- translational histone modifications can regulate gene transcription by influencing chromatin structure and accessibility, and likely play a role in this. Monocytes/macrophages demonstrate a developmental stage- specific increase in the H3K4 methyltransferase MLL1 with an associated gain in the activating histone modification histone 3 lysine 4 trimethylation (H3K4me3) at promoter sites of immunologically important genes as development progresses from extremely preterm neonate to adult. This gain allows for increasingly robust inflammatory responses as development advances. Microbial colonization of the skin and gastrointestinal tract occurs after birth and is associated with type 1 interferon expression, which is believed to guide immune system maturation and prevent detrimental pathogen responses. Chorioamnionitis is an inflammatory process affecting neonates around the time of birth, which negatively impacts immune system development and predisposes exposed neonates to long-term immune-related complications. The central hypothesis of this proposal is that neonatal monocytes/macrophages are largely un-patterned with H3K4me3 due to lack of in utero microbial exposure, and that postnatal microbial exposure stimulates low grade type 1 IFN expression which drives MLL1 expression and directs macrophage H3K4me3 deposition in a developmental stage-specific manner. Chorioamnionitis exposure stimulates a developmentally inappropriate level of type 1 interferon expression, which results in dysregulated MLL1 expression and global remodeling of the neonatal monocyte/macrophage landscape with subsequent dysfunctional monocyte/macrophage responses. This hypothesis will be investigated via the following specific aims: 1) Characterize normal human monocyte H3K4me3 patterning during infancy and early childhood and determine how developmental stage-specific H3K4me3 monocyte patterning impacts chromatin accessibility and gene expression, 2) Determine the requirement and sufficiency of type 1 interferons in MLL1-driven H3K4me3 placement in murine macrophage development and function, and 3) Determine the roles of type 1 interferons and MLL1 in chorioamnionitis-induced murine macrophage H3K4me3 remodeling and subsequent function.